Note: Descriptions are shown in the official language in which they were submitted.
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W)~tELESS PERSONAL COMMUNICATION SYSTEM
- Wireless access communications systems (WACS) strive to provide flexible
communication services in a
wireless fashion. WACS, in personal communication services (PCS) environments
may provide a system for
improving or eliminating drop wire requirements to homes and businesses. Radio
transmitters are the vehicle for
eliminating the need for wiring.
While cellular telephones and cordless telephones also provide some wireless
features, certain limitations
are inherent in each of these systems. Cellular telephones transmit signals to
cellular base stations at relatively high
power levels. The high power levels require Federal Communications Commission
(FCC) approval and careful
frequency planning to avoid unwanted interference. Additionally, the cellular
base stations tend to be complicated
and expensive units. Cordless residential telephones are lower power devices,
but the frequencies are usually prone
to interference. Also, cordless phones require wire connections to the public
telephone lines and cannot
communicate with wireless access communication PCS systems. Furthermore,
cellular phones and cordless phones
are generally not capable of supporting both voice and data transmissions.
A typical architecture for a wireless PCS system includes subscriber units
(SUs), radio ports (RPs), one or
more radio port controllers (RPCs), and an access manager (AM). The SUs
transmit information to the RPs using
radio frequencies. RPs are small devices typically mounted to existing utility
poles. The RPs are connected to an
RPC using wireline facilities. Each RPC is connected to a switch that is part
of the public switched telephone
network (PSTN) and the AM. The AM provides overall coordination of RPCs and
high level control of the entire
2 0 WACS system.
A consortium of telecommunication entities has recently developed a proposed
standard for providing
WACS .PCS. This standard outlines the above-mentioned architecture. Further
details concerning this proposed
standard are set out in Bellcore Corp. publication TR-INS-001313 entitled
Generic Criteria for Version 0.1 Wireless
Access Communications Systems (WACS) published October 1993 (herein sometimes
referred to as the
2 5 specification). The publication is available to those interested in WACS
PCS from Bellcore Corp. at Bellcore,
Customer Services, 8 Corporate Place - Room 3C-183, Piscataway, NJ 08854-4156,
or at 1 (800) 521-CORP, and a
copy of this publication has been submitted by applicants to become part of
the record of the present application.
Also, the reader may refer to Bellcore manual SR-ARH-002315 describing
specific modulator and demodulator
requirements in the SU and the RP. The reader is presumed to be familiar with
the specification and with related
3 0 technological issues known to those having ordinary skill in the art.
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Although a general standard has been set forth, advances and improvements to
the technology have been
discovered including implementation of novel configurations and circuitry. In
the configuration of the general
standard, SUs, whether portable or fixed, receive analog voice signals such as
those spoken into a telephone handset.
The SUs typically convert the analog voice signal to a digital signal and
compress the digital signal. The SU then
transmits the compressed signal over a radio link to an RP. The RP forwards
the signal to an RPC over wireline
facility.
Signals received by an RP from an RPC intended for a particular SU are
transmitted by the RP, received by
the SU, decompressed and converted to an analog signal to drive e.g. an
earpiece. Although this architecture
provides a functioning WACS PCS, it does not account for optimization of
electronic hardware to perform the
I O necessary signal processing. Also, this architecture does not cover system
configurations that improve signal routing ~ i/ 4
and decrease hardware requirements when specific applications arise.
Furthermore, only fixed or limited mobility
use is contemplated in the existing proposed standard.
Accordingly, a WACS PCS system is desirable that will operate in low power
applications, support voice
and data communications, and communicate with other WACS PCS systems.
Optimized hardware and flexible
system configurations are also desirable in a WACS PCS system, including
systems which minimize or eliminate the
need for transmission over tariff lines such PSTN or other commercial signal
carriers.
It would also be desirable for a WACS PCS system to allow a set of portable
SUs with a single dialed
number to be individually accessed. Such a feature would allow each member in
a family having a portable SU to be
accessed individually (e.g. only the desired family member's unit may ring)
even though the family only pays for a
2 0 single phone line from the local phone company.
It would also be desirable if an SU in a WACS PCS system could transmit and
receive both voice and data
information, especially if the SU could transmit and receive the data without
using a modem. Modemless data
transmission over the same line used for voice communication would greatly
reduce costs for the end user.
Reduced costs include the cost of a separate phone line for data transmission
and the costs associated with having a
2 5 modem such as in a fax machine.
Another advantageous feature is a wireless personal communication system that
provides data services
substantially similar to those provided by traditional wireline systems. The
system should transparently provide
these services to subscribers. In addition, the wireless personal
communication system should allow transmission of
high speed data such as voice band data.
3 0 It would also be desirable for an SU and an RP to be able to use a single
circuit board. A single circuit
board for the SU and the RP would reduce costs of manufacture and maintenance
for the SU and RP manufacturer.
It would also be desirable for a WACS PCS system to be flexible enough for use
both in the United States
and in other countries. It would also be desirable for the RPC to be able to
interface with switching systems that are
compliant with International standards. Such a system would advantageously
interwork with several communication
3 5 protocols associated with would comply with each country's technical
specification.
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It would also be advantageous for a WACS PCS system to allow new software
versions to be downloaded
to various components such as an SU, RP, or R_pC within the system.
Preferably, the same communication
infrastructure used for handling normal traffic could be used for downloading
the new soRware version. Direct
downloading advantageously allows a component owner to update software within
the component without requiring
the owner to take any action, such as changing a PROM or sending the component
to a maintenance center.
Another advantageous feature would be for the SU to be remotely activated by
the wireless PCS system.
Such remote activation would prevent fraudulent access and simplify the user
registration process.
Another advantageous feature would be for a WACS PCS system that could use
excess bandwidth in
existing CATV cabling. Using existing cabling would reduce costs in providing
PCS service and would allow cable
operating companies to provide telephony service as well as cable programming.
Aspects of the present invention provide a wireless personal communications
system (WPCS) having
several features, embodied in several forms. In one embodiment, the WPCS
includes at least one RP, a first SU in
communication with the RP, and a second SU in communication with the fu~st SU
through the RP without involving
the RPC in the manner contemplated by the specification. The RP may preferably
include a channel switching unit
for connecting the first SU with the second SU without using any tariff lines
to or from an RPC. Such an RP may be
used as a component in a wireless PBX or Centrex system including ISDN based
systems. Another preferred
embodiment provides for a walkie-talkie option where the first SU communicates
directly with the second SU,
2 0 preferably over an unlicensed frequency. In another preferred embodiment,
a plurality of SUs in communication
with an RP may be accessed individually using a single dialed number.
The SU may in another embodiment include a data port for directly transmitting
and receiving digital
information without using a modem. The SU may also include a pair of antennas
mounted spatially and angularly
diverse from each other, e.g., the second antenna may be at an opposite end of
the SU and orthogonal (or otherwise
2 5 non-parallel) to the first antenna. In another presently prefer-ed
embodiment, the SU includes a single integrated
circuit performing the functions of cyclic redundancy check (CRC), modulation,
demodulation, correlation,
decoding, encoding, and data transport.
In a further embodiment, the SU includes a particular circuit for
downconverting radio frequency signals
not contemplated in the specification. The circuit includes a first
downconverter section having a local oscillator
3 0 centered at a fu~st frequency, and a second downconverter section having a
local oscillator centered at a second
frequency. In another preferred embodiment, the SU is a portable SU for use in
a wireless personal communications
system and may be used in a high mobility environment. A high mobility
environment may include use of the
portable SU while traveling at typical vehicular speeds, e.g. 55 Mph.
Operating in a high mobility environment
provides a seamless connection for the end user. For example, a user may
originate a conversation on a portable SU
3 5 at home, and continue the conversation while driving to and then arriving
at work. Any handoff performed by an
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originating WACS PCS system to other systems, such as a second WACS PCS,
cellular system, or other
telecommunication system, will preferably be substantially transparent to the
SU user.
Preferably, the SU is implemented using a circuit board that may also be used
in an RP. The circuit board
preferably includes elements common to the SU and the RP and is configurable
to support common functions such
as transmission, reception, encoding, and decoding.
Another preferred embodiment provides for a wireless personal communications
system including a first
1RP, and a second RP in direct communication with the first RP via a
communications link other than (or in addition
to) the normal 1tP-ItPC-RP links contemplated by the specification. The
communication link may cant' audio,
video, and/or data signals and may use any method of communication, preferably
digital, such as a TI line, coaxial
1-0 cable, microwave connection, or fiber optic link. In a particular
embodiment a plurality of RPs may be directly
linked together such as in a local area network arrangement. One node in the
local area network may be an ItPC.
Alternatively, the ItPC may have a separate connection to one or more of the
RPs.
A further preferred embodiment provides, in a wireless personal communications
system including an ltP,
an SU in communication with the ltP, and an ItPC connected to the ItP, an ItPC
preferably including at least one
digital microprocessor having an interrupt of less than I millisecond. The
ItPC preferably has a communication
backplane including a plurality of slots. Each slot is adapted to selectively
receive either a Tl card interfacing to a
TI line or an EI card interfacing to an E1 line.
The 1RPC may further include at least one switching transcoder module (ST1V1).
Each STM is connected to
a separate TI line. Each switching transcoder module (STM) has at least one
digital signal processor capable of
2 0 processing both digitized voice and personal communication system
messages. In one preferred embodiment, the
STM includes at least one DSP handling both incoming and outgoing message
traffc. The DSP may handle from
two to six different conversations.
In another preferred embodiment, the STM has a fast digital signal processor
assigned to process incoming
messages and a second digital signal processor assigned to process outgoing
messages. The STM may further
2 5 include a plurality of memory butlers in communication with the digital
signal processors. The buffers may be
circular buffers adapted to receive and transmit personal communication system
messages from an RP or from a
digital switch. Each STM may further include a central processor for
allocating each time slot in each T1
communication line to at least one of the digital signal processors. The
central processor preferably communicates
with each digital signal processor using inter-processor data messages.
3 0 The ItPC preferably includes a call control processor including state
machines for processing ISDN and
WACS layer 3 protocols. In one embodiment, the ItPC includes a first global
resource processor for balancing
loading among various other processors in the ItPC. The ItPC may further
include a second global resource
processor and a disk drive coupled to the second global resource processor.
The second global resource processor
preferably cooperates with the disk drive to perform at least some access
manager functions.
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I
The RPC also preferably includes a channel access processor (CAP) for
processing Layer 2 personal I
communication system messages. Each of the processors within the RPC may
execute a mufti-tasking operating
system. The mufti-tasking operating system allows processors to create a
thread that is associated with a routine
executed by the processor. In one embodiment, a thread is created by the
operating system for at least one routine
performing call processing functions.
Another aspect of the present invention is that the RP or the RPC or both may
include a method of
modulating and demodulating signals for communication over unused bandwidth of
CATV cabling. An RPC may
be located at the headend of the CATV system or at other nodes in the CATV
system. In this embodiment, a cable
television provider may conveniently provide telephone service as well as
cable television to their customers, and/or
existing cabling may be used to minimize installment cost of a wireless PCS
system.
A further embodiment of the present invention provides a method of maintaining
user registration data in a
wireless personal communications system including the steps of timing a period
directly after an SU user hangs up,
maintaining power to the SU and a connection between the SU and the personal
communications system until the
timer reaches a predetermined value, and shutting down the SU after the timer
reaches the predetermined value. The
method of maintaining user registration is preferably incorporated into a
power saving standby mode in the SU. The
standby mode periodically depowers the SU during times of limited message
activity.
A further aspect of the present invention provides a method for downloading a
set of system upgrades to
any component, such as the SU; RP, RPC, or AM, in a wireless personal
communications system. The method of
downloading includes the steps of monitoring usage of the component receiving
downloaded information,
2 0 downloading a set of system upgrades to the component if the component is
inactive, verifying that the component
received the complete set of system upgrades, and then implemented the
downloading system upgrade. Also, the
wireless PCS system may include a table matching each- component with their
current software version.
Downloading a component advantageously reduces or eliminates the need to
change a PROM or otherwise
reprogram a user's component. Downloading is particularly useful for sending
system upgrades to SUs and RPs
2 5 since these components are likely to be owned by individuals.
A further embodiment provides a stand-alone wireless personal communications
system including a
plurality of portable SUs that may communicate with at least one local RP. The
RP transmits to and receives signals
from the plurality of portable SUs. The stand-alone system serving a home,
office or campus, can service SUs and
provide flexible communication without using any PSTN or other tariff
carriers: The stand-alone system may also
~ 3 0 be combined with direct SU-SU communication such as the walkie-talkie
embodiment described above to provide an
intercom or paging feature. The intercom feature allows SU users to send
messages or page other SU users within
the broadcast range of the SUs. If desired, the system may optionally port to
an external network such as the PSTN
or a WACS PCS system.
Alternatively, stand-alone systems may be networked with each other. For
example, an RP in a fn~st stand-
3 5 alone system may communication with an RP in a second stand-alone system
via radio or other communication
device such as a wireline facility. Many other connections and alternative
configurations of stand-alone system are
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possible. For example, a stand-alone system may function as a wireless PBX
replacing
traditional PBX systems. Such as a wireless PBX may be a node, or several
nodes, in a local
area or wide area network. The wireless PBX may also be connected to other PBX
systems
(wireless or standard wireline PBX systems) at other locations, such as in a
wide area
communication system.
Yet other aspects of the present invention are as follows:
A wireless personal communications system for carrying voice and data
communication signals, the system comprising:
a radio port controller;
a radio port coupled to the radio port controller, said radio port having an
RF transmit
section transmitting digital information in a time division multiplexed (TDM)
message frame,
the radio port including a channel switching unit; and
first and second subscriber units, each of said subscriber units having an RF
transmit section
transmitting digital information in a time division multiple access (TDMA)
format, wherein
the channel switching unit is adapted to route communication signals between
said first and
second subscriber units without routing the communication signals through the
radio port
controller.
A wireless personal communications system including:
at least one radio port;
at least two subscriber units, wherein one of said subscriber units
communicates with
another of said subscriber units through at least one of said at least one
radio port;
a radio port controller connected to said radio port, wherein said radio port
controller
has at least one digital microprocessor said microprocessor having an
interrupt of less than 1
millisecond;
said radio port controller further comprising:
a first global resource processor for balancing loading among various other
processors
in the radio port controller;
a second global resource processor;
a disk drive coupled to the second global resource processor; and
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said second global resource processor cooperates with said disk drive to
perform at least
some of the traditional access manager functions.
A wireless personal communications system comprising:
a radio port having an RF transmit section transmitting digital information in
a time
division multiplexed (TDM) message frame; and
first and second subscriber units, each of said subscriber units having an RF
transmit section
transmitting digital information in a time division multiple access (TDMA)
format, said first
and second subscriber units being adapted to selectively communicate with one
another via
said radio port, wherein said first subscriber unit may be accessed using the
same dialed
number as said second subscriber unit.
A wireless personal communications system comprising:
a radio port controller including a switching transcoder module (STM) having a
plurality of digital signal processors, each digital signal processor being
capable of
processing both digitized voice and personal communication system messages;
a radio port coupled to the radio port controller, said radio port having an
RF transmit
section transmitting digital information in a time division multiplexed (TDM)
format; and
at least two subscriber units, each of said subscriber units having an RF
transmit section
transmitting digital information in a time division multiple access (TDMA)
format, said
subscriber units being adapted for selective communication with one another
via said radio
port.
A wireless personal communications system comprising:
a radio port controller including a channel access processor (CAP) for
processing
layer 2 personal communication system messages;
a radio port coupled to the radio port controller, said radio port having an
RF transmit
section transmitting digital information in a time division multiplexed (TDM)
message frame;
and
at least two subscriber units, each of said subscriber units having an RF
transmit
section transmitting digital information in a time division multiple access
(TDMA) format,
said subscriber units being adapted for selective communication with one
another via said
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radio port.
A wireless personal communications system comprising:
a radio port controller including a plurality of processors executing a multi-
tasking
operatingsystem wherein at least one of said processors creates a thread
associated with a call
processing routine;
a radio port coupled to the radio port controller, said radio port having an
RF transmit
section transmitting digital information in a time division multiplexed (TDM)
message frame;
and
at least two subscriber units, each of said subscriber units having an RF
transmit
section transmitting digital information in a time division multiple access
(TDMA) format,
said subscriber units being adapted for selective communication with one
another via said
radio port.
A wireless personal communications system for carrying voice and data
communication signals, at least some of the communication signals being in
TDM/TDMA
format, the system comprising:
a radio port including a time slot interchange device for switching
communication
signals between time slot frames; and
at least two subscriber units, a first one of the subscriber units
transmitting communication
signals in a first time slot frame and a second one of the subscriber units
transmitting
communication signals in a second time slot frame; wherein the time slot
interchange device
is adapted to switch the communication signals in the first time slot frame
with the
communication signals in the second time slot frame to permit direct
communication between
the first and second subscriber units through said radio port.
The invention itself, together with further attendant advantages, will best be
understood by reference to the following detailed description, taken in
conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram of a standard wireless access communication system.
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Fig. 2 is a block diagram of a presently preferred embodiment of an SU
according to
the present invention.
Fig. 3 is a block diagram of a preferred RF section of a portable SU.
Fig. 4 is an illustration of a preferred message format sent by the subscriber
unit of
Fig. 2.
Fig. 5 is an illustration of a preferred message format sent by a radio port.
Fig. 6 is a functional block diagram of an encoder in the subscriber unit of
Fig. 2.
Fig. 7 is a functional block diagram of a decoder in the subscriber unit of
Fig. 2.
Fig. 8 is a functional block diagram of a radio port.
Fig. 9 is a block diagram of a preferred embodiment of the radio port of the
present
invention
Fig. 10 is a block diagram of a universal circuit board for use in an RP or
SU.
Fig. 11 is a block diagram showing functions to be performed by an RPC.
Fig. 12 is a block diagram illustrating one preferred embodiment of an RPC.
Fig. 13 is a block diagram of one preferred embodiment of an STM that may be
used
within the RPC of Fig. 12.
Fig. 14 is a block diagram of a central processor that may be used in the STM
of Fig.
13.
Figs. 15 - 20 are diagrams of various internal communication messages which
may be
used within the STM of Fig. 13.
Fig. 21 is a preferred DSP assignment table in the central processor of Fig.
14.
Fig. 22 is a block diagram of a CAP which may be used within an RPC.
Fig. 23 is a block diagram of a CCP that may be used within an RPC.
Fig. 24 is a block diagram of a global resource processor (GRP) that may be
used
within an RPC.
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Figs. 25-27 are message flow diagrams showing a preferred embodiment of
various messages between an
SU and an RPC.
Fig. 28. is an illustration of a variation of the system shown in Fig. I .
Fig. 29 is a diagrammatic illustration of a representative branch of the
system of Fig. 1.
Fig. 30 is a representative stand-alone system for wireless communications.
Fig. 31 is an illustration of an alternative embodiment of an SU.
Fig. 32 is an illustration of an alternative configuration of a system
architecture in a wireless personal
communtcat~ons system.
Fig. 33 is an illustration of an alternative configuration of a system
architecture in a wireless personal
communications system.
Fig. 34 is an illustration of an alternative configuration of a system
architecture in a wireless personal
communications system.
Fig. 35 is an illustration of an alternative configuration of a system
architecture in a wireless personal
communications system.
DhTA . .D D . RIPTION OF THE D A WIN
Fig. 1 illustrates a general block diagram of a standard wireless access
communication system (WACS) 10.
The WACS 10 includes subscriber units (SU) 20, radio ports ()ZP) 50, radio
port control units (RPC) 60, an
operations maintenance center (OMC) 70, a local digital switch 80, and an
access manager (AM) 90. The SU 20
2 0 communicates with the radio port 50 via radio links. Each RP 50
communicates with an ItPC 60 via transmission
lines, typically standard T1 lines. The 1RPC 60 controls radio links and
transmission lines carrying various voice and
data communications. The switch 80 controls access between wireless access
communication systems (WACS) 10
and the public switch telephone network (PSTN). The AM 90 provides call
control and also communicates with the
switch 80 providing voice paths between the WACS network and the PSTN.
Additional details are known to those
2 5 skilled in the art and are set forth in the Bellcore specification.
Recently, a newer proposed standard, personal access
communications (PACS), has been introduced. Both WACS and PACS standards,
however, may be implemented
on the system described below.
The SU 20 may be either a fixed subscriber unit or a portable subscriber unit.
A fixed subscriber unit may
be connected to an analog telephone by standard two (or more) wire analog
telephone lines. The SU 20, fixed or
3 0 portable, provides voice and data quality comparable to a wired system. A
portable subscriber unit is similar to the
fixed subscriber unit 20 but also includes a mouthpiece, an earpiece, and a
user interface keypad. The portable
subscriber unit 20, in one embodiment is similar to a cellular phone. In
another embodiment, the portable SU 20 is
functionally similar to a cordless phone. Unlike many cordless and cellular
phones, however, the portable SU 20
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digitally processes and filters all voice signals prior to broadcasting.
Subscriber units 20 provide wireless access for
both voice and data information. Unless otherwise indicated, the term
subscriber unit (SU) applies to both the fixed
and the portable versions in the following descriptions.
An SU 20 may be located in the home or the offce. Multiple SUs 20 may be in
range of a single RP 50
and may be in broadcast range of each other. One embodiment of the present
invention includes SUs 20 capable of
directly communicating with each other in an intercom-like or walkie-talkie
system. Another embodiment provides
SUs 20 that can communicate with each other through a common RP 50 configured
with a call switching capability.
Thus, SU 20 to SU 20 calls may be made without routing through the RPC 60 or
other components of the system.
Alternatively, calls between SUs 20 may be switched through an RPC without
performing any compression
1 Q processing.
Another feature of the SU 20 is a distinctive ring capability which may
provide individual annunciation or
pager functions. In this embodiment, a group of SUs 20 in a home or office
environment are assigned the same
phone number identifier. Each SU 20 programmed to this phone number can be
individually accessed. Individual
access may be accomplished by adding a suffx code to the telephone number. The
suffx code may cause only one
of the SUs 20 to ring or all of the SUs to ring with an identifying tone
specific to one user.
Preferably, the portable SU 20 may be used
in either low mobility, pedestrian environments or in higher mobility,
automobile environments. In a high mobility
environment, the RPC streamlines processing by sending some of the layer 2
messages from at least one of the DSPs
in the STM instead of processing the message in the CAP. Also, the SU 20 may
include a plurality and preferably
2 0 two receive chains. One of the receive chains is dedicated to sweeping for
optimal frequencies, and the other receive
chain communicates with the RP 50.
Referring to Fig. 2, a preferred implementation of an SU 20 is shown in
greater detail. The SU 20 has five
connections to the outside environment: an RF receive antenna 30, an RF
transmit antenna 29, a telephone
connection 61, a data port 62, and a debug port 63. Internally, the subscriber
SU 20 comprises an RF receive section
2 5 21, an RF transmit section 22, an analog port 23, a digital dataport 24, a
timing generator 25, a memory section 66,
and a databus 26 connecting all the internal blocks together.
The RF receive section 21 receives an RF input signal from the antenna 30. As
shown in Fig. 2, there
appear to be two antennas 29, 30 connected to the receive section 21. One
antenna 29 is actually switched between
the transmit and receive sections 21, 22 in standard WACS/PACS PCS. The RF
section 21 recovers voice
3 0 information from the RF signal in the form of a 32 kilobit per second
(kbps) ADPCM signal. The RF section 21 also
demodulates correlation information in the RF input signal. The received
information, whether voice or data, is then
placed on the databus 26.
The RF transmit section 22 receives voice or data information from the databus
26 and performs the
function of transmitting voice or data information. Voice information is
compressed to 32 kbps ADPCM and data
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information is simply modulated onto RF signals for transmission. In another
embodiment the SU 20 may transmit
or receive from another SU 20 directly.
The analog port 23 receives analog information such as from an analog
telephone and converts it to digital
32 kbps ADPCM for further processing and transmission over a radio link. Voice
information arriving from the
databus 26 in 32 kbps ADPCM form is converted to an analog signal and is
communicated to a telephone connected
to the port 23. The digital port 24 manages data signals sent to and from both
the debug port 63 and the data port 62.
The databus 26 is a data line connecting the various internal fwtctions of the
SU 20. Preferably, the databus 26 is a
16-bit wide communication line.
In a preferred embodiment, a standard two wire loop connects the analog port
23 to a standard analog
telephone. Analog voice signals picked up at the handset of the telephone will
be converted in a subscriber line
interface chip (SLIC) 56 from the two wire signal to a four wire signal. The
four wire format voice signals are
sampled and coded into a 64 kilobit per second mu-law pulse code modulated
(PCM) signal by a PCM codec 48 in
the SU 20. The digital signal is then processed in the digital signal
processor (DSP) 49 which compresses the PCM
signal into a 32 kbps ADPCM signal. In a portable SU the SLIC 56 is
unnecessary because the voice signals are
received from a mouthpiece attached to the portable SU. In one preferred
embodiment the same circuit board may
be used for either portable or fixed applications. A switch or jumper may be
used on the circuit board to designate
the board's application. Alternatively, the board may be loaded without the
SLIC 56 when a portable SU is desired.
The universality of the circuit board design allows for cost savings to
consumers and system operators:
In either type of SU, the DSP 49 sends the ADPCM signal along a databus 26 to
the RF transmit section 22
2 0 where it enters a transmit buffer 45. The digital signal is temporarily
stored in the transmit buffer 45 and then is
transferred to the channel encoder 44. The channel encoder 44 encodes the
digital signal with synchronization
information in accordance with instructions stored in a programmable read only
memory (PROM) 46 integrated
circuit. The program stored in the PROM 46 is the decoding and encoding
algorithm disclosed in the Bellcore
specification which anyone of ordinary skill in the art may program in to a
PROM or other memory device. The
2 5 encoded digital signal is transported through a serial-to-parallel (S/P)
converter 43 to a modulator 42. The encoded
signal is then converted from digital to analog in a digital-to-analog (D/A)
converter 41 and transmitted from the
transmit RF section 40 by an RF antenna 29.
Digital data signals originating at the digital input port 24 follow a
different path. Initially, the signal
coming in at a digital port 24 passes through an RS-232 connection 64 into a
DUART device 65. The data
3 0 information signal, unlike a voice signal, is not compressed into ADPCM
format. The digital data signal is not
processed in the PCM codec 48 or DSP 49. Instead, it proceeds along the same
databus 26 as the voice signals and
goes directly to the transmit buffer 45, the encoder 44 and then to the MOD 42
for modulation onto a carrier
frequency.
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After modulation, the signal (regardless of whether voice or data) is then
converted to an RF signal
approximately within the range of 1.8 to 2.2 GHz and transmitted from the RF
transmit section 22 at an average
power of approximately 10-20 milliwatts. The peak power transmitted is
approximately 80-160 milliwatts.
In standard WACS PCS, the output power of the RF transmit section 22 is
controlled by a power control
channel (PCC). The PCC can control the output power in steps of 0.75 dB +/-
0.25 dB steps, with the total
adjustment range being approximately 30dB. In a preferred embodiment, a power
controller 42 in the RF transmit
section 22 of the SU 20 translates the power control instructions originating
from the RPC 30.
Signals received by the SU 20 from a WACS/PACS PCS system first arrive at the
RF antennas 29, 30 and
are processed through a receive RF unit 31. The received analog signals are
converted to digital form in an analog-
to-digital (A/D) converter 32 and then demodulated in a demodulator 33. The
demodulated wave form is then
passed through a parallel-to-serial (P/S) converter 34, decoded in a channel
decoder 35, and passed through a receive
buffer 36. As part of the demodulation and decoding of the signal, the signal
is also passed through a digital
correlator 37 to analyze timing synchronization. The decoded signal in the
receive buffer 36 then passes on to the
databus 26 to the appropriate analog or digital port 23, 24 as determined by
the DSP 49. Suitable parts for the A/D
and D/A converters 32, 41 are a CXD1175AM-T6 A/D converter and a CXDI 171-T6
D/A converter available from
Sony Corporation. The Demod and Mod 33, 42 are preferably components as
described in Bellcore specification.
Fig. 3 shows a block diagram of a preferred embodiment of an RF transmit and
receive section 900 for a
portable SU. On the transmit ('fx) signal side, the RF section 900 has a
modulator 902 that modulates the outgoing
digital signal into I 904 and Q 906 lines which connect to a pair of I,Q
mixers 908. The pair of I,Q mixers 908
2 0 utilize the reference frequency firm a second local oscillator (L02) 910
to mix the I and Q transmit signals 904, 906
to a first intermediate frequency (IF) transmit signal preferably centered at
295.15 MHz for licensed band frequency
transmissions. The fast IF transmit signal is then filtered in a bandpass
filter 912, preferably a discrete circuit of
inductors and capacitors centered at 295.15 MHz, before being mixed again in a
mixer 914.
The mixer 914 receives the fu~st IF transmit signal and a mixing fi~equency
from a fu~st local oscillator
2 5 (LO 1 ) 916. The LO 1 is preferably capable of producing frequencies in
the range of 2.125 to 2.205 Ghz adjustable in
300 kHz steps. The first IF transmit signal is mixed to a higher frequency
second IF transmit signal in the mixer 914
preferably in the range of 1.85 to 1.93 GHz. After mixing, the second IF is
passed through a first gain stage 918, a
bandpass filter 920 with a pass band of preferably 1.85 to 1.93 GHz, and a
second gain stage 922. Once the signal
passes through the second gain stage 922, it proceeds through a
transmit/receive (T/R) switch 924 that connects the
3 0 signal to an uplink antenna 926 for broadcast over the airwaves.
Received signals in the range of 1.91 to 1.99 GHz arrive at both the uplink
antenna 926 and the
downlink antenna 928. The T/R switch 924 connects one of the antennas to the
receive portion of the RF section
900. The received signal is fast amplified in a gain stage 930, such as a low
noise amplifier to control the noise
figure, and is then passed through a bandpass filter 932 with a pass band of
1.91 to 1.99 GHz to a mixer 934. The
3 5 mixer 934 mixes the received signal with a reference frequency generated
by LOI 916 to create a first IF receive
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signal. A bandpass filter 936 centered at 215.15 MHz and connected to the
mixer 934 filters the first IF receive
signal.
The filtered first IF is then mixed in a second mixer 938 and downconverted to
a second IF preferably
centered at 10.7 MHz. Another bandpass filter 940 filters the second IF and
connects to a third mixer 942. The third
mixer 942 down converts the second IF to a third IF, preferably centered at
768 MHz by mixing the second IF
against a reference frequency. In a preferred embodiment the reference
frequency is a 9.932 MHz signal generated
by a crystal oscillator. The third IF continues on to an analog-to-digital
(A/D) converter 946 and the rest of the SU
circuitry for timing measurements and recovery of the voice or data
information.
The RF transmit and receive section 900 is based on a frequency scheme
determined by the reference
oscillator 948 which is preferably a temperature controlled crystal oscillator
(TCXO) set at 15.36 MHz. The TCXO
948 signal is passed through a divide-by-four (,4) circuit 950 and connected
to a mixer 952. The mixer 952, in one
embodiment, may be an image rejection mixer: The mixer 952 receives the
divided TCXO 948 signal and a signal
directly from the TCXO 948. The mixer 952 mixes these frequencies to a higher
frequency, preferably 19.2 Mhz.
The 19.2 MHz reference frequency branches off into two paths. One path
connects to a divide-by-48 (,48) circuit
956 and the other path connects to a divide-by-64 (,64) circuit 954. The ,64
954 signal, preferably a 300kHz signal,
is connected to LO1 916. The ,48 circuit 956 preferably produces a 400 kHz
signal and is connected to L02 910.
The TCXO signal also passes through a divide-by 5 (,5) circuit 958 for use by
the A/D converter 946 as a 3.072
MHz reference. Other frequency schemes may be used and the TCXO signal may be
used to create reference
frequencies to the rest of the SU.
2 0 In a preferred embodiment, the central processing unit managing the
processes in the SU 20 is a digital
signal processor (DSP) 49. A Texas Instruments TMS320C50 DSP chip is suitable.
Other DSP chips, such as a TI
TMS320C53 may also be used. The DSP 49 is used for both signal controls and
performing the 32 kbps ADPCM
speech encoding/decoding. In one embodiment, the DSP 49 operates as a 16-bit
parallel load processor utilizing a
16-bit wide data bus 26. The DSP 49 is driven by a clock frequency received
from the RF transmit 22 and receive
2 5 21 sections. Preferably the clock frequency is approximately 16 MHz (see
Fig. 3 TCXO) but higher or lower
frequencies may be used.
Another embodiment of the SU 20 includes an application specific integrated
circuit (ASIC) for performing
the control functions of cyclic redundancy checking, general synchronization
of incoming and outgoing signals,
digital phase-locked loop. In addition, the compression/decompression of the
signals may be completed by the
3 0 ASIC. Referring again to Fig. 2, an ASIC may replace the channel decoder
35, channel encoder 44, digital correlator
37, and the DUART 65.
Two components in the SU 20 require the attention of the DSP 49. The DUART 65,
which handles data
flow, and the channel encoder/decoder 44, 35, which is preferably a single
chip such as a Xilinx XC4005-6PQ208C,
both generate interrupts to indicate that there is incoming data or that the
component is ready for more data. The
3 5 channel encoder/decoder 44, 35 generates two separate interrupts; one for
encoding and one for decoding.
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In standard WACS/PACS PCS, the SU 20 employs a time division multiple access
(TDMA) method of
communicating digital information to a radio port 50. As best seen in Fig. 4,
the formatted information transmitted
from the SU 20 to the RP 50 is arranged in eight time slot frames 60, each
time slot 161 comprising 100 bits of
information. The SU 20 broadcasts information onto one of the time slots 161
in radio transmission bursts to the RP
50. A particular RF frequency can carry one frame 60 of information. In a
preferred embodiment the SU 20 can
sweep in frequency for available time slots in a message 60.
Each 100 bit burst of information lasts approximately 250 microseconds and is
synchronized such that the
burst always corresponds with an appropriate time slot 161 that the SU 20
reserved for the particular transmission.
Each time slot 161 of the transmitted message frame 60 carries information
necessary to synchronize the SUs 20
transmission burst. Each TDMA burst from an SU 20 contains several information
fields: guard band (GRD), slow
channel (SC), fast channel (FC), cyclic redundancy check (CRC), and a reserved
bit (RES).
The GRD and SC fields contain error information. The FC contains the speech or
data transmitted from the
SU 20 to the RP 50. The CRC information is computed at the SU 20 and used to
compare against CRC data
computed in the RP 50 for error detection or correction.
Fig. 5 depicts the standard formatted information received by an SU 20. An RP
50 transmits voice or data
information to an SU in time division multiplex (TDM) format. TDM
transmissions are continuous radio
transmissions as opposed to the TDMA bursts. Again the SU 20 is allocated to a
specific 100 bit time slot in a frame
70. The time slot 70 includes a synchronization pattern (SYC), a slow channel
(SC), a fast channel (FC) containing
the speech or data transmitted from the RP 50, a cyclic redundancy code (CRC),
and power control channel (PCC)
2 0 information.
The SYC and SC information comprise a 23 bit message that the SU 20 uses to
synchronize with the RP 50.
Synchronization and correlation are performed by the Xilinx chip.-
The CRC represents data computed at the RPC 60 useful for determining errors
in transmission.
The channel encoder 44, such as a XC4005-6PQ208C from Xilinx at 2100 Logic
Drive, San Jose CA
95124-3400, preferably encodes a digital voice signal with the proper digital
correlation information. The encoded
signal is then modulated preferably using quadrature amplitude modulation
(QAM) with a raised-cosine spectral
shaping filter.
As seen in Fig. 6, a preferred method of encoding voice data generated at the
SU 20 is to take the 64 kbps
mu-law PCM signal created at the PCM Codec 48 and encode the information into
32 kbps ADPCM. Preferably the
3 0 DSP 49 performs the encoding. The encoding is based on the CCITT
Recommendation 6.721 standard algorithm.
The encoding process begins by converting the mu-law PCM to uniform PCM. After
conversion to uniform PCM, a
difference signal is obtained by subtracting an estimate of the input signal
from the input signal itself. An adaptive
quantizer is used to assign four bits to the value of the difference signal
per sample. An inverse quantizer produces a
quantized difference signal from these four bits. The signal estimate is added
to this quantized difference signal to
3 5 produce the reconstructed version of the input signal. Both the
reconstructed signal and the quantized difference
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signal are operated on by an adaptive predictor which produces the estimate of
the input signal, thereby completing
the feedback loop.
Voice signals received on the antennas 29, 30 (Fig. 2) are 32 kbps ADPCM
signals modulated on RF
frequencies. The signals must be demodulated, converted to 64 kbps mu-law PCM
in the DSP, and sent to the PCM
Codec 48 for conversion into analog signals. The decoding, as illustrated in
the functional block diagram of Fig. 7,
is performed in a functional structure similar to the feedback portion of the
encoder algorithm together with a
uniform PCM to mu-law PCM conversion and a synchronous coding adjustment. The
adjustment prevents
cumulative distortion on synchronous tandem codings.
In a preferred embodiment the SU20 includes a delayed deregistration feature
and standby mode. The
delayed deregistration feature operates to keep an SU 20 registered on a
WACS/PACS PCS system for a period after
the SU 20 terminates a communication (i.e., hangs up). This feature helps to
avoid problems associated with
inadvertent disconnections and helps to speed up system access to the system
for consecutive telephone/data calls.
One embodiment of this feature includes a timer built in to the SU 20 to keep
the SU registered with the system for a
predetermined period of time after a disconnection, planned or inadvertent.
Another embodiment of this feature is to
control the SU power down from a timer located in the RPC that will keep the
SU registered for a predetermined
period of time.
In standard WACS/PACS PCS, the radio port (1ZP) 50 performs the basic function
of transmitting and
2 0 receiving voice and data information between the SU 20 and the ItPC 30.
The RP 50 exchanges information with
one or more SUs 20 over a radio link at RF frequencies, preferably in the
range of 1.8 to 2.2 GHz. The RP 50 may
exchange information with a single RPC 30 over a standard TI transmission
line. In addition one or more IZPs 50
may communicate with the ItPC 30 over a DSl interface, a high bit-rate
subscriber line (HDSL) interface, or Tl
interface methods.
2 5 Additionally, in a preferred embodiment the RP 50 - RPC 30 interface may
be a microwave, optical, or
cable television line interface. In one embodiment the RPs 50 may be
configured to utilize existing CATV cabling
for RP 50 - ItPC 30 communication (or RP to RP communications in alternative
embodiments discussed herein).
Existing unused bandwidth in the return band of the frequency division
multiplexed television signals may be used
3 0 on the CATV cabling. The CATV downstream and upstream signals are
preferably frequency division multiplexed
with the RPC to RP data signals and RP 50 to ItPC 30 data signals
respectively. The cable television return band is
approximately 5 to 50 MHz. Both voice and data information may be sent in
either direction along any of the
1'u'-RPC (or RP-1tP) interfaces. At higher data rates, video telephone calls
having both audio and video components
may be transmitted along these interfaces.
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An RP 50 is less expensive to manufacture and easier to use than a base
transceiver system in a cellular
network. Typically, an RP 50 is mounted onto an existing telephone pole or the
side of a building. RPs 50 do not
perform any special per-call processing on signals, such as subscriber
registration or authentication, and may
therefore be inexpensively produced.
Fig. 8 best shows a preferred embodiment including a functional block diagram
of a basic RP 50. The
RP 50 generally performs several functions including: transmission/reception
of the radio frequency signals, channel
coding/decoding of signals for synchronization with the network, and general
performance measurements. The
RP 50 contains an IF and RF section 51 receiving and transmitting information
signals at RF frequencies over an
antenna or antennas. Received RF signals at the IF and RF section 51 are
downconverted to a 400 kilobits per
0 second (kbps) data stream and sent to the channel enc~derfdecod~r"5:3
functioti~block: - Although 400 kilobits per
second is shown in the preferred embodiment, other data rates are equally
suitable, such as 384 Kbps. The channel
encoder/decoder 53 function is controlled by a microprocessor 52. The channel
encoder/decoder 53 function
involves managing the timing of signals an iving and leaving the RP 50. The
microprocessor function 52 manages
the formation received from an RPC is encoded into 32 kbps ADPCM for
transmission to an SU 20.
The standard RP 50 also performs radio channel measurements measuring the
performance of SUs 20 and
the RP 50. Controlled by the microprocessor 52, the radio channel measurement
54 is made and information is sent
to the RPC for processing with each burst. Voice and data signals broadcast
over a radio link at RF frequencies are
received at the RP 50. The RF frequencies are downconverted from the RF
frequencies to a 400 kbps data stream in
order to recover the information in the signal. The 400 kbps data stream is
decoded, processed through a radio
2 0 channel measurement unit 54 and then sent through a line interface card 55
for transmission over a T1 line connected
to an RPC. The decoded information received from an SU 20 and sent on to the
T1 line is preferably in a 64 kbps
PCM format. Conversely, signals received from the RPC are processed fu~st
through a line interface card 55
controlled by a microprocessor 52 and then encoded and converted to RF
frequencies for transmission to an SU 20.
Fig. 9 illustrates a preferred embodiment of the RP 50 in more detail. The RP
50 receives RF frequency
2 5 signals from one or more SUs 20 on a pair of spatially diverse antennas
152, 154. The RP 50 is tuned to receive a
particular frequency by the digital signal processor 174, such as a TMS320C53.
The received signal from the SU 20
is then downconverted in the receive RF sections 155, 156 respectively
attached to the spatially diverse antennas
152, 154. Each receive RF section 155, 156 downconverts the same frequency and
channels the downconverted
signal to an analog-to-digital (A/D) converter 157, 158 respectively attached
to the receive RF sections I55, 156.
3 0 Preferably the A/D converters 157, 158 are 8 bit, 20 Megasample per second
A/D converters such as a
CXD1175AM-T6 manufactured by Sony Corporation. The digital signals are
transferred to modem demodulators
160, 162, which may be implemented as VF4718 chips manufactured by Bellcore
Corp. Once the digital signals
have been demodulated in the demodulating sections 160, 162 they are compared
in a diversity selector 164.
Antenna diversity selection is described in standard WAC/PACS PCS to produce
the strongest signal
3 5 possible in the radio port 50. At the diversity selector 164, preferably
implemented with a VF4719 chip made by
Bellcore Corp., the different RF downconverted signals demodulated in the
demodulators 160, 162 are compared to
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find the best signal of the two that have been downconverted. Other forms of
selection diversity may alternatively be
employed such as known ratio combining or equal combining techniques. Ratio
combining involves taking the
better portions of each signal and combining the two portion to reconstruct
the best signal. Equal combining requires
taking equal amounts of both signals received on the antennas 152, 154 and
combining them. Because the antennas
152, 154 are spatially diverse from one another, the RP 50 is more likely to
receive a stronger signal. In a preferred
embodiment, the antennas are positioned spatially and angularly diverse and
most preferably orthogonal to one
another.
In another preferred embodiment, a frequency hopping scheme may be used where
the hopping rate is
proportional to the frame transmission rate. For a frame rate of 2 ms, a
frequency hopping rate of 500 Hz may be
used to enhance robustness in reception of RF signals. Each RF frequency
involved in frequency hopping is
preferably separated by 300 ICHz. Such a hopping mechanism also enhances the
transmission range of each cell in
the wireless PCS system. The above described advantages of frequency hopping
may also be realized by an antenna
hopping scheme.
Antenna hopping involves transmitting on different antennas to provide
increased randomization in the RF
signal received by an SU 20. Each RP 50 is programmed to transmit a
distinguishable antenna hopping sequence
and an antenna hopping code identifying the transmitted sequence. Preferably,
a DSP in the SU 20 receives the code
and responds to the antenna hopping sequence.
Another preferred embodiment may provide time diversity by interleaving a
plurality of frames.
Interleaving involves segmenting a digital signal, such as a digitized speech
signal, over a predetermined number of
2 0 message frames. The number of frames interleaved is proportional to the
randomization in the received RF signal,
but an increased number of frames increases transmission delay. A person
skilled in the art may choose the optimal
number of frames interleaved for a given application.
Following reception and downconversion of the RF frequencies and diversity
selection, the signal is then
processed through a parallel-to-serial (P/S) converter 166 and input in serial
format to a channel decoder 168. The
2 5 channel decoder 168 decodes the correlation information. In a preferred
embodiment the channel decoder 168
comprises a Xilinx XC4005-6PQ208C chip. Information decoded in the channel
decoder 168 is then forwarded to a
receive buffer 170 prior to being sent on a databus 173 to a destination
determined by the digital signal processor
174. Voice information is transmitted along the databus 173 to the DSP 174.
The DSP 174 decodes the 32 kbps
ADPCM to 64 kbps PCM. The PCM Codec 176 receives the 64 kbps mu-law PCM and
decodes it into an analog
3 0 signal. The analog signal is then processed in a Data Access Arrangement
(DAA) 178 for transmission along
telephone lines.
If the information placed onto the databus 173 is data information, the data
information is then directed by
the DSP 174 to the appropriate dataports 188, 186. The dataports 188, 186 are
connected to the databus 173 via a
DUART which translates the information into an asynchronous serial
input!output form that is then handed to an RS-
3 5 232 port 184. Alternatively, if the information placed on the databus 173
is intended for processing through a
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WACS1PACS network, then the information is routed through a T1 transport 190,
which may preferably comprise
an AT&T 1711SA chip, which interfaces with an RPC 30. In the alternative
embodiment mentioned above, where
the RP 50 is connected to an RPC (or other RP) via existing CATV lines, the T1
transport 190 is replaced with a
transport capable of modulating/demodulating the information up to the 5-SOMHz
band available on the CATV line.
Voice information received from the telephone lines or the RPC 30 is
transferred along the databus 173 to
the transmit buffer 194 in preparation for encoding in a channel encoder 196.
In a preferred embodiment the channel
encoder is a Xilinx XC4005-6PQ208C chip. The encoder 196 is programmed with
the algorithm disclosed in the
Bellcore specification in fumware installed in a PROM 198. The RP 50 also has
a memory block 175 for extra
program storage capability. The channel encoder 196 encodes the received 32
kbps ADPCM signal with
l0v= -----information regarding-timing anu synchronization. w'I"ne -encoded
ADPCM signal is processed through a serial=to-w~~=-~ _ _ _ _~
parallel (S/P) 200 device to configure the signal for modulation in a
modulator 202 which then transfers the signal to
a digital-to-analog (D/A) converter 204. After conversion to analog form, the
modulated signal is then converted to
an RF transmission signal in a transmit RF section 206. The RF signal
containing the encoded data is then
transferred along the transmit antenna 208 to the appropriate SU 20. For
transmission of data where no encoding is
necessary the encoder 196 and S/P converter 200 are bypassed and the databus
173 is directly connected to the
modulator 202. This decision may preferably be controlled by digital signal
processor (DSP) 174.
Another feature embodied in the RP 50 is power control in connection with a
subscriber unit 20. The radio
port 50 collects data on received signal strength using a received signal
strength indicator (RSSI) 172. The RSSI 172
is located on the RF receive portion of the RP 50. Also a word error
indication bit (WEI) is received from an SU 20
2 0 and transferred through the DSP 174 to the RPC 30.
Generally the RP 50 transmits a time division multiplex (TDM) transmission
with 8 time slots. The RP 50
uses one of the time slots as a system broadcast channel (SBC) for reference
by the SU 20 in synchronizing frames
transmitted. Just as the SU 20 transmits into one of the 8 slots in bursts,
the RP 50 transmits on all 8 slots. When
transmitting, the RP 50 synchronizes with the rest of the system 10 using a
timing generator 192 which preferably
2 5 operates at 400 kilohertz. The timing aspects of the eight slot message 70
transmitted by the RP 50 is important both
because information sent from an SU 20 must be synchronized to fit into the
proper slot in a frame and because
information transmitted to the RP 50 and then onto TI lines must be
synchronous with time slots available and
expected by the system 10. As mentioned above, a preferred format for the
interface between the RP 50 and the
RPC is DS1 over a T1 line. Similar to the time slots in the eight slot message
transmitted between SU 20 and RP 50
3 0 the TI line connected to the RPC 30 also has DS 1 time slots which must be
synchronized with the information.
Referring again to Fig. S, formatted information transmitted via RF
frequencies from the RP 50 to the
SU 20 is illustrated. The SBC time slot contains 100 bits as do the other 7
time slots. However, the 64 bit fast
channel (FC) in the SBC is unused.
In a preferred embodiment a universal circuit board may be used to construct
either a radio port 50 or a
3 5 subscriber unit 20. Different components may be loaded depending on
whether the universal board is to be an RP or
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an SU (or a hybrid RP/RPC in an alternative embodiment discussed herein).
Alternatively, the universal circuit
board may have all the functional elements for RP and SU configurations loaded
and the specific configuration
enabled may be determined by a simple hardware or software switch.
As best shown in Fig. 10, the universal board 1000 has two antennas 1001
connected to two receive chains
1002. A transmit chain 1004 is connected to one antenna 1001 through a
transmit/receive switch 1003. The two
receive chains connect at an antenna diversity selector 1005. The receive
chains 1002 and the transmit chain 1004
are linked to a databus 1008. Also linked to the databus are an
encoder/decoder 1006, and a memory block 1007.
The board further contains a DSP 1009 connected to a PCM codec 1010. The DSP
1009 is also connected to the
databus 1008. The PCM codec 1010 connects to a SLIC 1011, a portable SU
connector 1012, and a DAA 1013.
1 D The DAA 1013 is connected to a PSTN port 1014 and the SLIC 1011 connects
to an analog phone jack 1015. A T1
transport 1016 connects to the databus 1008 and to an RP/RPC port 1017. The
data bus 1008 is further linked to a
DUART 1018 which is, in turn, connected to an RS-232 connector 1019. The
connector 1019 is linked to both a
debug port 1020 and a data port 1021.
In a preferred embodiment of the universal circuit board 1000, an SU can be
created by disconnecting or
disabling one receive chain 1002, the DAA 1013, and the T1 transport 1016. In
addition, the appropriate program
for encoding/decoding signal synchronization is placed in the memory 1007. In
an alternative embodiment, the
encoding/decoding program for both the RP and SU may be loaded into the memory
1007 for later designation by
instructions received at the debug port 1020, by a hardware switch on the
universal board, or by a decision of the
DSP 1009.
2 0 Differentiation between a fixed and a portable SU may also be made with
the universal board 1000 in a
preferred embodiment. By disabling or not connecting a SLIC 1011, in addition
to the other changes necessary to
create an SU, the board 1000 is suitable for use as a portable SU. A fixed SU
is created by enabling or connecting a
SLIC 1011 and disabling or disconnecting the portable SU connector 1012.
In another embodiment, the universal circuit board may be configured as an RP.
By disabling or
2 5 disconnecting the SLIC 1011 and the portable SU connector 1012, the
universal board 1000 has substantially all the
necessary functions to operate as an RP. Further, another preferred embodiment
of the universal board 1000 as an
RP includes customizing the type of RP required for a specific configuration.
For example, an RP that will only be
used to directly connect to the PSTN does not need the T1 transport circuitry
1016. Power supply requirements on
the universal board 1000 can be met by either including the necessary
components or by external power supply
3 0 circuitry both of which are easily accomplished by one of ordinary skill
in the art. The presently preferred
embodiment of the universal board 1000 adds flexibility to WACS/PACS PCS
system planning and requires fewer
parts to be carried in stock for repairs or replacements of system parts.
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Another central component in the wireless personal communication system is the
radio port controller
(RPC) 300. The RPC 300 manages RP resources and controls the transport of
information between a network switch
80 and its associated RPs 50.
The RPC 300 interfaces with at least one RP 50 and with at least one switch
80. The RP 50 interface is
preferably a DS 1 layer 1 interface allowing a 64 kb/s clear channel and a
TDM/TDMA layer 2 interface mapping the
TDMlTDMA time slots to DS1 channels. The RPC 300 to switch 80 interface is
preferably a DS1 physical interface
using the ISDN Basic Rate Interface BRI communication protocol defined in the
Bellcore specification.
In the basic configuration contemplated by the Bellcore specification, the RPC
300 performs catl processing
V functions and transcodes compressed data into full PCM data and vice-versa.
The RPC 300 exchanges signaling
information with the SU 20 and collects performance monitoring information
(e.g. radio link quality, channel usage,
channel allocation, traffic data, and system capacity information).
Fig. 11 is a functional block diagram of a potential embodiment of an RPC 300.
The RPC 300 includes an
RP DS1 line interface module 301 connected to RPs 50 over RP DSI communication
links 318 and a switch DS1
line interface module 302 connected to the switch 80 over switch DS 1
communication links 320. The RPC 300 also
includes a radio interface function module 308 in communication with the RP
DS1 line interface module 301
through an RP-Tl bus 306 and a switch interface function module 310 in
communication with the switch DS1 line
interface module 302 through a switch Tl bus 304. The radio interface function
module 308 and the switch interface
function module 310 are connected to an auxiliary communication function
module 312. The auxiliary
2 0 communication function module 312 is connected to the AM 90, preferably
over a fn~st Ethernet TCP/IP interface
314 and is connected to the OMC 70, preferably over a second Ethemet TCP/IP
interface 316.
The RP-DS1 line interface function module 301 preferably consists of the
physical, mechanical, and
electrical functions required to support the 1.544 DS1 lines 318 to the RPs
50. The switch-DS1 line interface
function module 302 preferably consists of the physical, mechanical, and
electrical functions required to support the
2 5 1.544 DS1 lines 320 to the switch 80. The radio interface function module
308 preferably performs the
functions of multiplexing and demultiplexing wireless personal communication
system (WACS or PACS) traffc and
signaling information into the DSO slots of the DS1 interface to the RP 318.
The radio interface function module
308 may also insert unused bits in the RP DS1 interface 318 due to timing
differences between the 1.544 DS1 line
and the RP 50 time slots. In addition, the radio interface function module 308
generates a TDM/fDMA
3 0 synchronization pattern for the RP DS 1 interface 318. The radio interface
function module 308 also transcodes
compressed digitized speech into mu-law PCM speech and transcodes mu-law PCM
speech into compressed
digitized speech. Currently, the RPC 300 compresses speech using 32 kb/s ADPCM
encoding; however, other
compression schemes may be used such as 16 kb/s LDCELP or ADPCM type
compression. Also, although mu-law
PCM is used for uncompressed speech, other digital representations of speech
may be used such as A-law PCM.
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The radio interface function module 308 performs error checking of wireless
personal communication
system layer 2 information preferably using a 16-bit checksum, and processes
radio link quality measurements such
as word error indication bits and co-channel interference codes received from
the RP 50 over the RP DS1 interface
318. The radio interface function module 308 also processes layer 2 wireless
personal communication system
signaling messages. In addition, the radio interface 308 maintains TDMfTDMA
timeslot status information such as
busy/idle and per-call information for each active call. Finally, the radio
interface 308 multiplexes alerting channel
and system information channel information based on priority onto a system
broadcast channel that is sent over the
RP DS 1 communication link 318.
The switch interface function module 310 performs the signaling functions
required to interface to the
switch. More specifically, the switch interface module 310 receives and
transmits call processing messages to the
switch. In a preferred embodiment the communication protocol to the switch
over the DS1 interface 320 is the ISDN
basic rate interface (BRI) and the switch interface function module receives,
transmits, and processes ISDN
communication messages. However, the interface 320 may be any other digital
communication method such as
ISDN primary rate interface (PRI) or an optical interface such as SONET. The
switch interface function module 310
also interfaces with the auxiliary communication function module 312
performing incoming call processing and
OMC functions. The switch interface function module 310 communicates with the
radio interface function module
308 using the switch T1 bus 304 when processing outgoing calls.
The auxiliary communication function module 312 coordinates activities of
various ItPs 50 such as by
maintaining per-RP information including e.g. "up/down" status, radio link
quality, channel usage data, and traffic
2 0 statistics. The auxiliary communication function module 312 routes calls
from the switch 80 to the proper RP 50.
The auxiliary module 312 also sends, receives, and processes layer 3 wireless
personal communication messages to
and from the AM 90 using the first Ethernet TCP/IP interface 314. The
auxiliary module 312 interfaces to the OMC
70 ovefthe second Ethemet interface 316 to monitor and control a software
downline load function such as when a
new version of software may be downloaded to a component of the system. Such
downloading is particularly useful
2 5 for updating software in the SU 20.
Fig. 12 shows a component block diagram of a preferred embodiment of an ItPC
330 according to the
present invention. The 1ZPC 330 includes a global resource processor (GRP)
332, a switching transcoder module
(STM) 334, a common access processor (CAP) 336, and a call control processor
(CCP) 338. The RPC 330 also
includes a T1 bus backplane 344 and an E1 bus backplane 346. The TI bus 344
interfaces to a T1 card 342. The T1
3 0 card 342 can-support up to two T1 lines 356, each interfacing with the RP
50. The TI card 342 communicates with
the TI bus 344 over a TI bus slot 354. Similarly, a TI switch card 340 in
communication with the switch over two
- Tl lines 360 fits into a slot 358 in the E1 bus backplane 346. The RP Tl
card 342 may be installed in slots 1, 3, 5, 7
providing up to 8 Tl lines to the RPs 50. The switch side T1 cards 340 may be
installed preferably in slots 9, 10, I 1,
12, 13 of the E1 bus backplane 346 providing up to 10 Tl lines 360 to the
switch.
3 5 The GItP 332 communicates over a backbone LAN 352 to the OMC 70 and to the
AM 90. The GRP 332
also communicates with at least one CAP 336 and at least one CCP 338 over an
internal LAN 350. The GItP 332
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provides access to the external backbone LAN 352 and performs network
management and other centralized RPC
330 functions. Each CAP 336 communicates with preferably up to 8 STMs 334 over
a high speed VME bus 348.
Each STM 334 is connected to both the Tl bus 344 and the E1 bus 346. Also,
each CCP 338 is connected to the El
bus 346.
As shown in Fig. 12 there may be as many as 5 CAPS 336, and as many as 4 CCPs
338 in the RPC 330.
Although Fig. 12 shows a specific number of each component the present
invention is not limited to a specific
number of components. Specifically, the present invention is designed support
additional components such as extra
GRPs 332, CCPs 338, CAPS 336 and STMs 334.
In addition, as more processors are added, additional Tl cards 342 and T1
switch cards 340 may also be
added. Also, it should be noted that the E1 bus 346 may also support E1 cards
as well as T1 cards 349 for use in
countries other than the United States such as in Europe. In a preferred
embodiment, a backplane associated with the
E1 bus 346 has a plurality of slots and each slot is adapted to receive either
a T1 or an E1 card. The slot electrically
connects the T1 bus and the E1 bus to the inserted card (T1 or E1), preferably
using a single universal connector. In
one embodiment, a manual switch connected to the backplane allows a user to
manually select the card type and the
associated bus, Tl or E1. Alternatively, the type of card, T1 or E1, supported
by each slot may be configured in
software instead of using the manual switch.
Each STM 334 receives and transmits wireless personal communication system
interface frames to and
from an RP 50 via one T1 line 356 and the Tl backplane bus 344. Preferably,
one STM 334 is used to handle one
Tl line 356 to the RP 50. Each STM 334 also receives and transmits speech data
to and from the switch on DSO
2 0 slots on any of the T1 lines 360 connected to the E1 backplane bus 346.
The CAP 336 provides interrupt timing to the STMs 334 and sends commands to
the STMs 334 over the
VME bus 348. The VME bus 348 allows the CAP 336 to directly access, read or
write the local memory within each
STM 334. The CAP 336 can also access the backplane T1 bus 344. The CAP 336
communicates with the CCP 338
and the GRP 352 over the internal LAN 350.
2 5 The CAP 336 includes a common processor module (CPM) containing a
processor such as an INTEL 960
processor including associated circuitry and a communication chip interface
such as the AT&T SPYDER chip. The
common processor communicates with either the T1 bus 344, the E1 bus 346, the
LAN 359, or the VME bus 348.
Each CAP 336 manages and maintains radio links for up to 8 STMs 334. Each CAP
336 maintains
information such as STM numbers, radio port IDs, RF carriers and TDM/'TDMA
time slots used by the radio link as
3 0 well as the radio link status. Each CAP 336 generates STM 334
synchronization interrupts and forwards wireless
personal communication system layer 3 messages received from the STM 334 to
the CCP 338 and sends messages
from the CCP 338 to the STM 334. The CAP 336 also processes wireless personal
communication system layer 2
messages except the acknowledge mode transfer messages that are handled by the
STM 334.
The CCP 338 provides an ISDN interface to the switch. The CCP 338 performs
switch interface processing
3 5 including ISDN D-channel signal processing and multiplexing/
demuItiplexing of multiple D channels from the
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switch side T1 line 360. The CCP 338 accesses time slots on the backplane E1
bus 346 containing ISDN channel
signaling information received from the switch via a communication module,
such as an AT&T SPYDER chip. T'he
CCP 338 also performs wireless personal communication system layer 3
processing including call origination, call
delivery, call disconnect and anchor ALT processing as well as the exchange of
messages with the CAP 336 and the
GRP 332 in support of layer 3 processing.
The GRP 332 provides RPC 330 centralized functions such as network management,
OMC interfacing, set
up and management of TCP/IP connections to the access manager AM, wireless
access communication system
layer 3 registration message processing, and load balancing between multiple
CCPs 338 and CAPs 336.
As shown in Fig. 13, the STM 334 contains one central processor (CP) 362 such
as an INTEL 960
processor and 12 digital signal processors (DSP)s 364 such as Texas
Instruments C30DSP processors in the prefer ed
embodiment. The STM 334 also has an E1 buffer 370 for communicating with the
switch 80, and a communication
processor such as an AT&T SPYDER chip for communicating with the RPs 50.
The E1 buffer 370 includes an input buffer having the same length, preferably
320 bytes, as an output
buffer. The E1 buffer 370 contains a forward slot location pointer (FSLP) for
determining the current position in the
E1 buffer 370 for transmitting and receiving data. The FSLP may be a register
containing the offset into the buffer
370 of the current byte being received or transmitted.
The SPYDER communication processor 366 is preferably configured so that a DS1
frame is divided into
two superchannels. Each superchannel carries 12 bytes of a wireless personal
communication system payload group.
A payload group consists of 1680 bits (16 bursts, each burst having 105 bits)
of data from the RP 50. For both
2 0 transmit and receive, a buffer 367 configured for the SPYDER for each
superchannel, consists of 16 circularly linked
blocks having 12 bytes each. The buffer size matches the size of the RP time
slot and the number of buffers match
the size of the payload group. This configuration allows efficient
synchronization to the payload group in addition to
efficient manipulation of RP 50 time slot data.
The DSPs 364 provide speech transcoding such as ADPCM to PCM or LDCELP to PCM
as well as
2 5 wireless personal communication system layer 2 message processing. The
DSPs 364 communicate with the CP 362
via an internal FIFO 378 mechanism. The CP 362 communicates with the CAP
module 336 via the backplane VME
bus 348 and also communicates via the internal LAN 350 during downloading and
debugging.
A pair of DSPs 364 within each STM 334, one DSP 364 for processing receive
slots from the RP side and
the other DSP 364 for processing receive slots from the switch side Tl 360, is
allocated for each call. The CP 362
3 0 assigns each of the DSPs 364 into pairs where one DSP 364 is a Rx DSP 364
and the other is a Tx DSP 364. Each
DSP 364 pair converts ADPCM speech from the RP side T1 line 356 to PCM speech
sent to the switch side T1 line
360 as well as compresses PCM speech from the switch to ADPCM speech sent to
the RP 50.
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The pair of DSPs 364 also perform wireless personal communication system layer
2 acknowledge mode transfer
processing. This processing involves splitting and recombining layer 3
messages into multiple layer 2 segments;
maintaining sequence number, checksum, and acknowledgment data; and
retransmitting layer 2 messages. The pair
of DSPs 364 also perform RP signal quality measurements such as RSSI
measurements. The pair of DSPs 364
process the IZSSI values received from the RP 50 over the T1 line 356 and
provides the best RP timeslot information
to the CP 362.
The CP 362 receives wireless personal communication system messages from the
RP 50 and distributes
data to the pair of DSPs 364. The CP 362 also receives PCM speech from the
switch and distributes the data to the
pair of DSPs 364 handling the call. The CP 362 synchronizes wireless personal
communication system messages on
the RP side and performs wireless personal communication system layer 2 and
layer 3 message forwarding between
the CAP 336 and the pair of DSPs 364. The CP 362 also marks the next available
slot for a call to the RP using
RSSI information received from the DSPs 364. Finally the CP 362 processes
anchor time slot interchange
information.
As shown in figure 14, the CP 362 in the STM 334, preferably contains a
background process 400, an
interrupt process 410, a DSP interface 422, and various memory components. The
memory components include data
structures such as the VME buffer 416, the time slot control blocks 418, the
uplink circular queue 424, the downlink
circular queue 426, and the DSP flags 420. The VME buffer 416 is connected to
the VME BUS 348 and allows
communication between the STM 334 and the CAP 336. The time slot control
blocks 418 preferably include 16
blocks grouped into an array with one block for each RP Tl 368 time slot. The
time slot control blocks 418 contain
2 0 all the information required by a payload interrupt process 412 to process
voice and layer 2 messages related to each
time slot in the RP TI line 368. The DSP flags 420 include an array of state
flags, one for each DSP 364. In the
preferred embodiment there are 12 DSPs so the array contains 12 DSP flag
entries. Each flag entry is used to mark
whether a DSP 364 is available for use by the payload interrupt process 412.
The interrupt process 410 performs all time critical processing including
building a wireless personal
2 5 communication system payload envelope and determining which time slot to
mark as available. The background
process 400 performs non-time-critical functions required by the STM 334.
In a preferred embodiment, the background process 400 consists of the
background task 402, the signal
quality task 404, and the configuration task 406. The background task 402
preferably performs the following
functions: sending health check messages to the controlling CAP 336, checking
the health of the DSPs 364 and
3 0 reloading DSPs 364 reporting a large number of errors, monitoring and, if
necessary, resetting the E 1 hardware such
as the EI bus 346, processing commands received from the CAP 336, and
monitoring STM 334 alarm conditions.
STM 334 alarm conditions may include loss of T1 clock, loss of or unstable CAP
336 interrupt, STM 334 to CAP
336 interface failure, DSP 364 failure, loss of synchronization at the RP T1
368, and E1 buffer 370 memory failure.
The signal quality task 404 periodically processes RP 50 signal quality
measurement data such as RSSI data
3 5 received from the DSP 364 and uses the signal quality data to mark the
next best time slot available in the time slot
control block 418. Preferably, the configuration task 406 is responsible for
processing STM 334 configuration
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messages received from the CAP 336 during STM 334 initialization and
reconfiguration. A more detailed
description of hardware initialization and configuration may be found in U.S.
Patent No. 5,299,198, the entire
disclosure to be incorporated by reference herein.
The interrupt process 410 includes the wireless personal communication system
payload interrupt process
412 and an anchor interrupt process 414. The payload interrupt process 412 is
controlled by a control interrupt,
preferably 500 micro seconds in duration, generated by the CAP 336.
In a preferred embodiment, the payload interrupt process 412 periodically
performs the following
functions: voice processing, next available slot marking, wireless personal
communication system layer 2 and 3
processing, and setting the time slot control block 418 active upon receipt of
a busy time slot indication. Voice
processing involves moving data from the EI input buffer 370 to the DSP 364
for compression, such as ADPCM
compression, and then moving the compressed data to the transmit buffer 367
for output to the RP Tl line 368.
Voice processing also includes receiving voice data from the receive buffer
367 and decompressing the data to PCM
data and placing the PCM data into the E1 output buffer 370.
Layer 2 and 3 message processing involves processing both uplink and downlink
messages. For the uplink,
a message received from the SU 20 is inserted into the uplink time slot
circular queue 424. For the downlink, a
message from the CAP 336 is inserted into the downlink time slot circular
queue 426 indicating the message is
available for transmission over the RP T1 line 368.
Preferably, the anchor intermpt process 414 is enabled when the STM 334 is
configured for anchor mode.
The anchor intetnrpt routine 414 preferably moves data from the E1 input
buffer 370 for a particular DSO slot of the
2 0 Tl line 372 to the EI output buffer 370 effectively looping data from the
switch.
The DSP interface module 422 may communicate with the DSPs 364 using the FIFO
374. The DSP
interface 422 may send and receives formatted messages to the DSPs 364 over a
FIFO data bus 376 by reading and
writing data. When a command is sent to the DSP 364 it may also be written
into the FIFO 374. The CP 362 then
issues an interrupt to the DSP 364, and the DSP 364 preferably processes the
command and inserts a response back
2 5 into the bidirecrional FIFO 374. Each response from the DSP 364 contains a
response status code. In a preferred
embodiment the following response status codes are available: no error (0x00),
PCM data returned (0x01), wireless
personal communication system payload returned (0x02), layer 2 message
returned (0x03), layer 3 message returned
(0x04), INFO ACK being processed (0x05), layer 3 message segment in response
(0x06), layer 3 message
acknowledged (0x07), error (Oxff). Each response from the DSP 364 also
contains a NRlI'R status field containing
3 0 the status of DSP 364 timer (TRxxx) and counter (NRxxx) parameters. The
NR/TR status field is bit mapped with
each bit set to 1 if the NRxxx counter value has been exceeded or the TRxxx
timer has expired. In the preferred
embodiment the NRrfR status field includes: bit 0 - TR216 timer, bit 1 - TR217
timer, bit 2 - TR218 timer, bit 3 -
NR210 count, bit 4 - NR211 count, bit 5 - NR212 count, and bit 6 - NR213
count.
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Each CP 362 to DSP 364 command or response includes a time slot number
corresponding to the RP T1
368 time slot being processed. Time slots 0 to 7 are allocated to the first
frequency in the wireless personal
communication system payload group and 8 to 15 are allocated to the second
frequency in the payload group.
Some of the CP 362 to DSP 364 commands or responses includes an SC type field
and an SC data field that
is dependent on the SC type field. Preferably, the SC type fields include the
following types: system broadcast
(0x00) - the SC data field contains the available bandwidth, available channel
(0x01) -- the SC data field contains
the available bandwidth, busy channel with CCIC (0x02) - the SC data field
contains the CCIC, busy channel with
MC-S (0x03) - SC data field contains the 4 bit segment of the MC-S, and busy
channel with SDC (0x04) - SC data
field contains 4 bit directive of the SDC.
In a preferred embodiment, the following CP 362 commands and DSP 364 responses
may be supported:
ADPCM compression, payload processing, layer 2 message building, layer 3
message building, DSP configuration,
link deactivation, and layer 3 polling. As shown in Figure 15, the ADPCM
compress command has octet aligned
fields containing 16 bytes of PCM voice data. The ADPCM command also includes
a length field containing the
number of following bytes in the command, an embedded operations channel EOC
field, SYC bits, a wireless
personal communication system super&ame number, the time slot number, the SC
channel type, and the SC channel
data. The ADPCM response contains a 12 byte payload envelope built by the DSP
364 as well as the response status
field, the length field, and the NRlTR status field.
As shown in figure 16, the process payload command preferably contain the
payload envelope to be
processed. The response contains a data field that may be PCM data, a layer 2
message, a layer 3 message, or may
2 0 be empty if a layer 3 message is pending. The response also includes the
EOC, the signal quality RSSI value, the
quality indicator (QI), the word error index (WER), the wireless superframe
number, the time slot, and the SC
channel type and data.
As shown in figure 17, the build layer 2 message command preferably contains a
layer 2 message. The
response includes the payload envelope containing the layer 2 message.
2 5 As shown in figure 18, the build layer 3 message command preferably
includes a layer 3 message to be
built into multiple payloads. The command may include a payload containing a
portion of the layer 3 message.
Subsequent commands sent to the DSP 364 result in a response including
payloads containing fiuther segments of
the layer 3 message and a status of layer 3 message pending until the entire
layer 3 message has been sent to the RP
50.
3 0 As shown in figure 19, the configure DSP command preferably loads the
NRxxx and TRxxx parameters
into the DSP 364.
The deactivate link command (not shown) causes the DSP 364 to stop any
protocol processing and to reset
its sequence numbers for the given time slot.
As shown in figure 20, a layer 3 polling command may poll the DSP 364 for a
layer 3 acknowledgement
3 5 message from the SU 20. When the CP 362 sends a layer 3 message to the DSP
364, the CP 362 preferably polls the
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DSP 364 until receiving a response having a response status of "layer 3
message received" indicating that the SU 20
has acknowledged receiving the layer 3 message. When the response indicates
that the SU 20 has acknowledged
receiving the layer 3 message, the length field in the response is zero and
the response does not contain a payload
envelope.
Figure 21 shows how DSPs 364 may be allocated by the CP 362 for processing the
individual payload
envelopes in a payload group. The letter "a" is the fu~st RF frequency in the
payload group. As shown, the DSPs 364
are grouped into pairs, one transmitting DSP and one receiving DSP. The DSPs
364 are grouped into pairs so that
signalling for ACK MODE TRANS and INFO ACK message processing can occur using
a dual port shared RAM
between the pair of DSPs 364. Although Fig. 11 only shows allocation of DSPs
364 for a single RF frequency, other
allocations of DSPs 364 are possible for handling multiple RF frequencies.
According to another aspect of the present invention, the STM 334 operates in
the following manner. For
downlink voice processing, the STM 334 moves voice data from the switch 80 to
the SU 20. STM 334 downlink
voice processing is initiated by the payload interrupt process 382. After 16
bytes of data has been received into the
E1 buffer area 370, the CP 362 composes the 16 bytes of voice data into a
compression command sent to a transmit
(Tx) DSP 364. The Tx DSP 364 converts the 16 bytes of PCM voice data into
ADPCM data and forms a payload
envelope containing the compressed data. The payload envelop containing the
compressed speech data is then
moved into the buffer area 367 for transmission over the RP Tl line 368.
STM 334 uplink voice processing requires the STM 334 to move voice data from
the SU 20 to the switch.
When a payload envelope has been received in the buffer area 367 and a DSP 364
allocated to the time slot is
2 0 available, the CP 362 payload interrupt process 382 formats the received
data into a DSP process payload command
and sends the command to the Rx DSP 364. The DSP 364 then converts the ADPCM
speech from the received
payload into 16 bytes of PCM speech. The PCM speech is then moved from the
FIFO 374 to the E1 buffer area 370
for transmission to the switch.
STM 334 downlink message processing involves moving layer 2 messages from the
CAP 336 to the SU 20.
2 5 The CP 362 moves the layer 2 message from the VME buffer 386 to the Tx DSP
364 using the build layer 2
message command. The Tx DSP 364 responds to the build layer 2 message with a
payload containing the layer 2
message. The payload containing the layer 2 message is then moved to the
buffer area 367 for transmission over the
TI line 368.
STM 334 uplink message processing involves processing a message received from
the SU 20. The payload
3 0 envelope containing the message is passed to an available DSP 364. The DSP
364 responds to the CP 362 with the
layer 2 message that is then inserted into the uplink circular queue 424 in
the CP 362 where the message can be
retrieved by the CAP 336 for further processing.
STM 334 anchor processing involves looping all received data from the E1 input
buffer 370 to the E1
output buffer 370 for a designated time slot. Anchor processing is done by the
CP 362 using the anchor interrupt
3 5 process 384.
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As shown in Figure 22, the CAP 336 preferably includes various processing and
data elements. In a
particularly preferred embodiment, the CAP 336 includes a wireless personal
communication system layer 2 unit 500
which includes a system broadcast task 502, a wireless personal communication
system link manager 506, a wireless ~ ',
personal communication system layer 2 state machine 504, and a radio link
control block 508.
The system broadcast task 502 may have three message cues. An alert channel
cue system, system
information channel cue and priority request channel cue. The system broadcast
task 502 preferably formulates a
system broadcast channel (SBC) Superframe 510 from the three message cues
which is sent to the STM 334. Within
the STM, the SBC Superframe may be received in a VME SBC area 516 of the VME
buffer 416. The system
broadcast task 502 is preferably awakened every I .02 seconds since the SBC
Superframe 510 has a period of 1.024
seconds: The system broadcast task 502 may also communicate with the state
machine 504.
The link manager 506 communicates with a router task 516 via messages from the
CCP 338 over the
internal LAN 350 and sends and receives layer 2 and 3 messages to the STM 334.
The link manager 506 also sends
link commands to an STM manager task 514 in communication with the STM 334.
The VME buffer 416 has a layer
2 and layer 3 area 518 and a configuration area 520 for receiving and sending
messages to the link manager 506 and
the STM manager task 514. The link manager 506 also communicates with the
state machine 504. The link
manager 506 is responsible for establishing and maintaining radio links. The
link manager 506 receives and
processes CCP layer 3 messages and forwards any alert commands received from
the CCP to the system broadcast
task 502. '
Messages sent to the STM 334 from the link manager 506 include header
information such as the STM slot
2 0 number, payload group number, time slot number (0/15), and message type
(layer 2 or layer 3). The STM slot
number, paid load group number and time slot number constitute a radio link
identifier 1ZL,ID used to identify
messages for active links. The radio link control block RLCB 508 contains an
entry for each radio link. Each link is
identified by the associated STM slot number, payload group number and time
slot number. The ItLCB 508
contains the following fields: RL1D, assigned STM chassis number, assigned
time slot number and current state.
2 5 The STM manager task 514 monitors and controls every STM 334 associated
with the CAP 336. The STM
manager 514 performs the functions of initializing the STM monitoring the STM
334 for alarms and failures,
verifying software in each STM 334, reconstructing data structures from the
STM 334 in the event of a failure, and
providing utilities and writing commands over the VME bus 348.
The state machine 504 in the preferred embodiment has been implemented as a
layer 2 state table that is
3 0 shown in Table A below. Processing within the state machine 504 is
preferably performed as directed by the state
table. The state table includes various procedures described in detail below.
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Table A.
WACS/PACS
Layer
2 State
Table
Events States
Null Initial Link Link ALT Anchored
State Access Up SuspendIn
Pending Progress
Initial SOO
Access
Req.
Initial SOI
Access
Cnf
Initial S02
Access
Deny
L3 Message SO1
Link Suspend S03
Link Resume S08
Access S09 S09
Release
ALT RequestS04 S04 S04
ALT Complete SOS
ALT Deny SOI
ALT Exec S I
0
ALT Ack S 10
Set Anchor S06
Release S07
Anchor
Set Link SO1
Release SOI
Link
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WACS State Procedures
State Procedure SOO
This state procedure performs the following when an Initial Access Request is
received in Null State.
I. Set the current state to Initial Access Pending.
State Procedure SOl
1. Set the current state to Link Up.
State Procedure S02
This state procedure performs the following. --_. __ . _ . .
1. If anchor channel is allocated then activate voice channel on the anchor
channel.
2. Deallocates all link resources.
3. Set the current state to the Null State.
State Procedure S03
This state procedure performs the following when a Link Suspend is received in
the Link Up State.
4
I. Set the current state to Link Suspend State.
2. Forward LINK SUSPEND to CCP.
3. Send Mute command to STM.
State Procedure S04
This state procedure performs the following when an ALT Request is received in
Null State.
1. Set the state to the ALT In Progress.
2 0 2. Forward ALT REQ to CCP.
State Procedure S05
This state procedure performs the following.
I . If (Infra-AL'I~ then switch the voice path to the new time slot or STM.
2. Stop 1'N202.
2 5 3. Set the current state to Link Up.
4. Forward ALT COMP to CCP.
State Procedure S06
This state procedure performs the following.
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1. Set the current state to Anchored.
2. Send command to Anchor STM to anchor a channel.
State Procedure S07
This state procedure performs the following.
1. Release all call resources.
2. Set current state to Null State.
State Procedure S08
'This state procedure performs the following.
1. Set the can ent state to Link Up.
2. Forward LINK RESUME to CCP.
State Procedure S09
This state procedure performs the following.
1. Set the current state to Null State.
2. Forward ACCESS RELEASE to CCP.
State Procedure SIO
This state procedure sets the current state to ALT In Progress.
As shown in figure 23, the CCP 338 includes process components that may be
executed on a processor such
as an INTEL 960 processor. The CCP 338 is loaded with multitasking operating
system software such as
VXWORKS from Wind River Systems. The process components include a management
task 550 that initiates and
2 0 directs messages between the other components, a call control task 552
that implements a layer 3 wireless personal
communication system state machine, and an ISDN processing task 554. The ISDN
processing task 554 implements
layers 1, 2, and 3 of the ISDN access signaling protocol defined as CCITT
standard Q931/Q921 and controls a
synchronous protocol data formatter device that communicates with the switch
80 at the central office. The ISDN
task 554 is performed by ISDN software available from PGM&S Inc. at 1025
Briggs Road, Suite 100, Mt. Laurel,
2 5 NJ 08054.
The management task 550 preferably spawns the other components and routes all
incoming and outgoing
messages from the AM 90 and the CAP 336. In a preferred embodiment, the call
control task 552 has one thread for
each active call. Each thread may be an instantiation of the wireless personal
communication system layer 3 state
machine defined in table form in Appendix A. The state machine table defined
in Appendix A contains many teens
3 0 defined in the Bellcore specification. Also, persons skilled in the art
will recognize that the Intelligent Services
Peripheral (ISP) supports the AM 90.
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The call control task 552 may also have a thread that performs ALT DN
management and a thread that
routes messages to and from each of the state machine threads. The Global
Resource Processor (GRP) 332 is a
collection of tasks and functions that are executable preferably on a CPM
board including an Intel 960 processor. As
shown in figure 24, the GRP 332 includes a message muter 600, a resource
manager (RM) 604, a call distribution
manager (CDM) 606, an administrative interface 608, a network management
system (NMS) agent 610, and an
InputlOutput port manager (IOPM) 612. The message muter 600 communicates with
the AM 90 and the OMC 90
over the backbone LAN 352 and communicates with the other RPC components over
the RPC LAN 350. The
message router 600 is connected with the RM 604, the NMS agent 610, and the
CDM 606. The CDM 606 is
connected to the RM 604 through a congestion data block 616. The CDM 606 is
also connected to the
administrative interface 60R and the rrtessage routes 600r -- _.
The IOPM 612 is connected to an IO card function module 614 that communicates
with external
communication links such as Tl lines. The IOPM 612 is connected to the CDM 606
and the administrative interface
608.
The RM task 604 is the central RPC 330 component responsible for handling
resource shortages throughout
the RPC 330. This task 604 manages buffers and queue shortages on RPC 330
components indicating a component's
CPU is over-utilized with respect to the component's available memory. The RM
604 keeps track of global
resources enabling the CDM 606 to balance the load among RPC processors. The
RM 604 may throttle system
activity within its control such that the offered traffic load is balanced
against the available system resources. The
RM 604 prevents the system from reaching a critical point in which increased
activity results in a collapse of the '
2 0 components under the RM's 604 control.
The RM 604 manages congestion report messages received from components in the
RPC 330 of the
associated GRP 332. For each congestion report message, the RM 604 records
appropriate statistics, and sends an
acknowledgement to the sending component. The RM 604 manages a system resource
table based on the congestion
report messages. The RM 604 may receive commands for statistics reports from
the NMS Agent (AGNT) 610.
2 5 The RM 604 recognizes the onset of system wide congestion in a way that
protects against further
congestion, reacts to congestion in a manner that is specific to the area of
congestion and corresponds to the severity
of the congestion level. The RM 604 allocates and tracks system resources
available within the RPC so that traffic is
prioritized in the order of emergency calls, existing traffic, and then new
traffic with respect to the available
resources.
3 0 The GRP 332 provides an interface to the OMC 70 for performing network
management functions. The
Network Management Agent 610 provides a transport mechanism to support these
functions or may perform
network management functions directly. The NMS Agent 610 performs the
following functions: maintains statistics
by application tasks in a global memory area, provides statistics to the OMC
70, monitors trace and control flags,
maintains summary status information, processes alarms and call control
requests, and supports processor downline
3 5 loading and reconciliation.
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Call control requests include call monitoring, call tracing, call path
allocation, forced call handoff, and
forced call clearing. The NMS agent 610 also handles call record management,
component control in response to
OMC commands, and debugging and testability support such as upline dump, and
memory read/write.
The Call Distribution Manager (CDM) 606 provides call distribution and network
management services.
When a call setup is initiated, the CDM 606 determines the call identifier
(RCID) and selects a CCP 338 for the call.
The CDM 606 handles call manipulation requests (by controlling the appropriate
CCP 338) from the OMC 70 such
as call monitoring, forcing an ALT, clearing a call and fetching the status or
statistics of a call.
The message router 600 allows the GRP 332 to perform call processing functions
including distributing
requests for call originations among active CCPs 338, providing via the
Backbone LAN 352 an interface to other
RPCs, initiating graceful disconnection of active calls when CCPs 338 fail,
and polling active CCPs 338 for current
call status information when switching in a backup GRP 332.
The IOPM 612 indicates when Tl line failures occur by frequently polling the
IO Cards 614 minimizing the
time between failure and resulting action. The IOPM 612 maintains and reports
to the OMC 70 the status of I/O
ports. The IOPM 612 also monitors T1 I/O Ports for alarm conditions and
reports events to the OMC 70. Finally,
the IOPM 612 may perform switchover for backup T1 cards in response to alarm
conditions or to an operator
request.
Another preferred embodiment allows the RPC 330 to perform functions
traditionally handled in the AM
90. An ItPC 330 performing traditionally AM functions may be implemented by
adding a GItP 332 with an
associated disk drive to the RPC 330. The disk drive includes various
databases. These databases may provide for
2 0 subscriber features, dynamic subscriber data, radio equipment
configuration, altering area mapping, terminal
location, routing instructions, call processing activity information,
subscriber status, encryption information, or other
subscriber desired information.
Traditionally AM functions provided in the RPC 330 on the added GItP 332
include authenticating and
registering subscribers, administrating the radio network, managing billing
information, and interacting with the
2 5 database to determine the subscriber's radio location, status, alerting
information, and terminating features. The GRP
332 may also control the 2 stage alerting process by first locating the SU 20
and then directing the switch to establish
a voice connection to the RP 50 and alert the subscriber. The GItP 332 works
with the switch to provide originating
service for wireless calls. The GRP 332 instructs the switch 80 to associate
the call origination with the subscriber.
The GRP 332 may query the database for the subscriber's originating features
and control the switch to provide that
3 0 set of features.
Although a single added GRP 332 and disk drive have been disclosed, the
present invention is not limited
to the number or arrangement of GIZPs 332 or storage devices such as disk
drives used for performing at least some
traditionally AM functions. A network including multiple GItPs 332, storage
devices, or other RPC 330 processing
components may be arranged in various ways for efficiently implementing
traditionally AM functions in the RPC
3 5 330 of the present invention.
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Figure 25 shows the messages transmitted between various RPC 330 elements and
the SU 20 for a layer 2
initial access message. The CP 362 (labeled STM960 in figure 25) receives a
payload from the RP Tl line 368
communicating with the SU 20. The CP 362 distributes the payload to multiple
Rx DSPs 364 to handle the
individual time slots in the payload. Each Rx DSP 364 parses the time slot
fast channel and determines that the
payload is carrying an initial access message. The DSP 364 resets the
acknowledge-mode-transfer link variables
(NS/NR) and then forwards the initial access message through the CP 362 to the
CAP 336 via the internal VME bus
348. The link manager 506 in the CAP 336 performs the necessary layer 2
protocol processing using the state
machine 504 and sends an access confum message via the CP 362 to the Tx DSP
364. The Tx DSP 364 formats the
~I Oaccess confirm message in the fast channel of the time slot into a payload
to be sent to the SU 20 over the RP TI line
368.
Figure 26 shows the message flow for a call origination from an SU 20. The Rx
DSP 364 parses the fast
channel and determines the call origination message is an acknowledge-mode-
transfer (layer 3) message. The Rx
DSP 364 performs acknowledge-mode-transfer processing including assembling the
call origination message from
the multiple segments received in the fast channel. The Rx DSP 364 also
validates the checksum and sends an Info
Ack Layer 2 message via shared RAM to the Tx DSP 364 for transmission over the
RP TI line 368 to the SU 20.
When the complete layer 3 call origination message has been received, the Rx
DSP 364 forwards the message to the
CCP 338 via the CAP 336.
The CCP 338 performs layer 3 processing upon receiving the call origination
message as defined in the
2 0 layer 3 state machine (see Appendix A) and executed by the call control
task 552. Layer 3 processing includes
message exchange with the AM 90 and sending an RCID assign layer 3 message to
the Tx DSP 364 via the CAP 336
and CP 362. The Tx DSP 364 fragments the layer 3 message into multiple
segments if necessary and sends the
RCID assign message to the SU 20. The Tx DSP 364 then performs ack-mode
transfer processing such as waiting
for any layer 2 info ack messages and retrartsmitting any unreceived message
segments. The other messages shown
2 5 in Figure 26 are processed in a similar manner until the call is set up
and a communication path is established
through the RPC 330. ,
Figure 27 shows the RPC 330 message flow for a call delivery. First the CCP
338 receives an alert
message from the AM 90 and sends an internal alert message to the CAP 336. The
CAP 336 uses the system
broadcast task 502 to format an SBC superframe 510 that is sent to each STM
334 managed by that CAP 336. The
3 0 SBC superframe message is then tuansmitted by each STM 334 in the SBC slot
of the payload on the RP TI line 368.
The remaining messages are layer 2 and layer 3 messages that proceed in a
similar manner as described for call
origination until a call connection is established.
The PCS system may use the components in a variety of configurations. Fig. 28
shows a preferred
3 5 embodiment of a portion of a PCS system 200 having a hybrid RP/RPC 202
capable of switching calls between two
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or more SUs 204, 206. In this embodiment the hybrid RP/RPC 202 contains the
hardware of a regular RP 50 as
described above and also includes a time slot interchange device 218. The time
slot interface device 216 is capable
of switching information between time slot frames in the eight frame messages
60, 70 of the TDM/T'DMA format.
The hybrid RP/RPC 202 contains two channel units (CU1, CU2) 212, 214, a switch
210, a time slot interface (TSI)
216, and a Tl interface card 218. The TSI 216 connects a memory location in
CU1 212 to a memory location in
CU2 214
Signals received from a first SU (SU1) 204 at the antenna assembly 208 of the
hybrid RP/RPC 202 are
transmitted through the switch 210 to the CU1 212. Signals received from a
second SU (SU2) received at the
antenna assembly 208 are transmitted through the switch 210 to the CU2 214.
Both CU1 212 and CU2 214
communicate with the TSI 216. The TSI 216 swaps information between the time
slots transmitted by the respective
SUs 204, 206 to complete an SU to SU call. In a preferred embodiment, four
separate calls, each having an SU 20
on each end of the call, can be handled by a single hybrid RP/RPC 202.
Fig. 29 illustrates a branch of the standard configuration of a wireless PCS
system 220. The system 220
includes an SU 222, an RP 224, an RPC 226, and an AM 228. The SU 222 may be
either portable or fixed. The RP
224 is preferably mounted on a telephone pole for better reception of radio
frequencies and convenient access to
telephone lines. The RPC 226 manages at least one RP 224 and calls are
monitored by the AM 228. The RPC 226
is connected to the PSTN 230 for routing calls that cannot be switched within
the system 220.
Figure 30 shows a stand-alone wireless PCS system 232. The stand-alone system
232 may act as an
advanced cordless phone system. The RP 234 is mounted on the side of a home or
business in this embodiment. By
2 0 bringing the RP 234 down from the position on the telephone pole (see Fig.
29) as is the case in a more standard
configuration, the system 232 acts more like a cordless phone system with the
additional benefits of digital signal
processing. One or more portable SUs 236 may communicate with the RP 234.
Alternatively, a mixture of portable
and fixed SUs may communicate with the RP 234. The RP 234 may communicate with
an RPC or with the PSTN
directly. Preferably the RP 234 receives the radio signals from the one or
more SUs 236 and then places digital 64
kbps PCM signals on the telephone lines via a standard RJ-11 phone jack and a
drop wire 238 attached to the
structure in which the RP 234 is located. The stand-alone system 232 may also
include paging features and internal
calling between SUs 236 over unlicensed frequencies.
In another embodiment, of the stand-alone system 232 a hybrid RP/RPC, as
described above, may replace
the RP 234. Yet another embodiment of the system 232 includes an RP 234
mounted on the interior or exterior of a
3 0 structure where there is no drop wire 238. Rather than communicating
through a drop wire 238, the system uses an
RP configured to send and receive signals to another RP positioned, for
example, on a telephone pole over a radio
link.
Fig. 31 shows another embodiment of an SU. In this embodiment the SU is built
on a computer board 260.
The SU computer board 260 may just have data capability or may have data and
voice. The SU board is simply
3 5 placed in a personal or other form of computer 262 and may be part of any
of the system configurations described
herein.
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Figure 32 shows another preferred embodiment of a wireless PCS system 238. In
this embodiment,
multiple ltPs 240 may be linked together and connected to a single Tl, or
compatible, line 242. The RPs 240 may
be connected together in serial fashion. As with the RP 50 - ItPC 30
interface, the interface may be a DSI, HDSL, a
cable, microwave, or optical interface. Each RP 240 has access to a
predetermined number of time slots in a
message 60, 70. By dividing up time slots among the number of connected ltPs
240, only one TI line 242 is
necessary thereby saving the system operator extra wiring and usage fees.
Further, the serially connected RPs may
be used in a stand-alone system or may be connected to the PSTN.
In one variation, the RPs 240 may only be tuned to a single 1tF frequency such
that only eight calls may be
handled. In another variation, multiple frequencies, each capable of carrying
an eight frame message 60, 70, may be
-- handled by the ItPs 240 so that ali available time slots on a Tl ine or
other interface is used.-Also, a hybrid 1tP/RPC
may be used in the serial configuration.
Other network configurations may also be implemented in a presently preferred
PCS system. Fig. 33
illustrates a star configuration 243. The star configuration 243 may have
chains of ItPs 244 linked along a single, or
multiple, Tl line 246. A central RP 248 may be configured internally to pass
signals along however many branches
are included. Another embodiment of the star configuration includes an RP 248
or a hybrid 1tP/RPC connected to a
Tl or other suitable link that is connected to the PSTN, an RPC or another
local area network (LAN). Fig. 34 shows
another network configuration of ltPs 252. This circular LAN 251 may be
connected with Tl or other type data
connections 254 capable of carrying the PCS message frames. Fig. 35 best shows
a portion of a system 256 for use
in remote areas or areas lacking any telephone infrastructure. The system 256
may include an SU or SUs 258 in
2 0 communication with an RP 260 that is a simple relay/repeater transmitting
to another RP repeater 260. The one or
more RP repeaters 260 can transmit to a standard RP 262 in communication with
an 1RPC 264 and a standard PCS
system. Also, the RP repeaters 260 may connect the SU 258 to a hybrid RP/RPC
for switching calls to other remote
SU's. The flexibility of the repeater system 256 would allow for stand-alone
systems to exist, communicate with
each other if desired, and later be transformed into a public network if
desired.
30
