Note: Descriptions are shown in the official language in which they were submitted.
21! 92248
METHOD AND APPARATUS FOR SPECTRUM MANAGEMENT
Field of the Invention
The present invention relates generally to a method and apparatus for radio spectrum
5 management. More particularly, the present invention relates to a method and apparatus for
automatically m~n~ging radio spectrum used to provide wireless communications services.
Back~round of the Invention
Wireless communications in general, and wireless cellular communications systems in
10 particular, are becoming increasingly popular. Originally, cellular communications systems
were used to provide analog mobile telephone services. Today, cellular communications systems
provide various wireless communications services. As used herein, the term wireless
communication service is used to identify any logically discreet use of the wireless spectrum.
For example, wireless services include analog mobile telephone service, digital mobile telephone
15 service, and cellular digital packet data (CDPD) services.
Cellular communication systems are well known, and generally include cell sites, each of
which serves a coverage area, or cell. The cell site is the location within a cell which contains
the hardware (e.g. antenna(s) and radio base station) required to communicate with mobile end
units (e.g. wireless mobile telephone or wireless mobile data terminal). A mobile end unit
20 operating within a particular cell in the system communicates with the cellular system through
the cell site covering that cell. The various cell sites are connected to one or more mobile
switching centers (MSC) which connect the cellular system to a land-line network. In the case of
2 21 92248
a cellular telephone network, the land-line network is the public switched telephone network
(PSTN). In the case of a CDPD network, the land line network may be the PSTN or some other
type of data network (e.g. the Internet).
Wireless communication service providers are generally licensed to operate a wireless
system in a particular geographic area using a specified frequency spectrum for radio
communication between mobile end units and base stations. For example, a typical wireless
service provider may have a license to operate in a 12.5 MHz spectrum. This spectrum may be
divided into 416 channels, each 30 KHz wide. Each of these 416 channels is capable of handling
the communication between one mobile end unit and a radio base station. For further
information on cellular air interface, see, EIA/TIA Standard 553, "Mobile Station-Land Station
Compatibility Specification", September 1989, Electronic Industries Association, Washington,
D.C.; EIA/TIA Interim Standard IS-54-B "Cellular System Dual-Mode Mobile Station -
Basestation Compatibility Standard", April, 1992, Electronic Industries Association,
Washington, D.C.; and E~A/TIA Interim Standard IS-136 "Cellular System Dual-Mode Mobile
Station - Basestation: Digital Control Channel Compatibility Standard", April, 1995, Electronic
Industries Association, Washington, D.C., which are incorporated herein by reference.
Most wireless systems in use today are fixed channel cellular systems. A fixed channel
cellular system is a cellular system in which each cell is assigned a fixed group of channels for
communication. For example, if each cell within a cellular system were assigned a group of 34
channels, there could be a maximum of 416/34 = 12.24 or approximately 12 cells carrying the
permissible 416 calls in the serving area if there was no channel reuse. However, if cells are
sufficiently spaced apart, in terms of geographic ground distance, channels can be reused in
2 1 9224~
multiple cells without overlap. Designing a fixed cell system which reuses channels is a complex
task. One problem with a fixed system is that cellular traffic is not always constant. Thus, the
characteristics of a cell site may be such that the cellular traffic at the site may not be consistent
during the course of a day or week. Further, over time, the overall characteristics of cellular
5 traffic at a site may change such that the daily and weekly usage patterns in general may change.
When a cellular system is initially installed in a geographic area, the channels are
allocated among the cell sites based on estimated demand. As the system operates, information
about radio spectrum usage in the system is collected and stored in a ~ t~b~e in the mobile
switching center. After the system has been installed for a period of time, a person (generally an
10 engineer) will analyze the stored spectrum information. The engineer may look at statistics such
as blocking rate (the rate at which users ~lle~ ling to use the cellular system are blocked),
dropped call rate (the rate at which calls are prematurely dropped), attempt failures ( user
requesting a communication channel but not receiving one), page failures (a paging system
failing to complete a page to a paging unit), out of service statistics (how often a channel is taken
15 out of service due to unacceptable quality), and bit error rate (error rate on digital channels).
Based on this information, the engineer may determine that channel reallocation is necessary.
For example, it may be determined that another channel is required at a particular cell site. If
this is the case, the engineer must then go on to determine an appropriate channel to allocate to
the cell site. This requires an analysis of potential interference with other cell sites using that
20 channel. The alteration of the channel assignments in a fixed system is a complex and time
consuming task, which generally requires the expertise of a radio frequency (RF) engineer or
other competent person. Manual reallocation of channels, as described above, is particularly
4 2 1 9224&
difficult to perform in real time, and thus cannot take into account the variability of
communication traffic on a short term basis.
To more efficiently use the limited frequency spectrum, schemes other than fixed
channel systems are also being studied. One such scheme is called adaptive channel allocation.
5 In an adaptive channel allocation system, the cells are not assigned a fixed group of channels.
Instead, the cellular system is self org~ni7ing in that each cell dynamically determines which
channels it will use for communication. Thus, the system adapts itself based upon the
communication traffic. The problem with current adaptive channel allocation schemes is that a
cell site dynamically determines which channels it will use for communication without
10 communicating with other cell sites. As a result, the overall efficiency of the spectrum use is
limited.
Another difficulty in the maintenance of wireless systems is the sharing of radio
spectrum among different services. As described above, wireless service providers are
increasing the types of wireless services they provide. However, the spectrum available to
15 provide these services is not increasing at the same pace. Thus, a single wireless service provider
must share the same spectrum among dirr~.ellL services, such as analog mobile telephone service,
digital mobile telephone service, and, mobile CDPD service. As is the case with cellular
telephone systems, CDPD systems are generally fixed channel systems, such that the cell sites
are assigned certain fixed channels, and these fixed channels are dedicated to CDPD service. (It
20 is noted that CDPD systems often share base station hardware with cellular telephone systems.)
Again, a problem exists in that the demand for the dirl~lent types of services may vary over time.
As a result, engineers need to study spectrum usage and periodically need to reallocate channels
2 1 9224&
among the cell sites and among the various services. The reallocation of channels over multiple
services is even more complex and time consuming than reallocating channels in a single service
system.
As described above, frequency spectrum is limited, and the frequency spectrum licensed
5 to a wireless communication service provider is a highly valuable resource which must be
managed efficiently.
Summary of the Invention
The present invention provides a real time method and appal~lus for m~n~ging the
10 frequency spectrum within, and across, wireless services, in order to make more efficient use of
radio spectrum.
In a single wireless service embodiment, a frequency spectrum manager device is in
communication with a switching office of a wireless communication system. The switching
of fice is in communication with a plurality of radio base stations, each of which are capable of
15 communicating with mobile end units over a plurality of radio channels. Each of the radio base
stations has a set of radio channels which the radio base station uses for communicating with the
mobile end units. This set of radio channels defines the radio channel configuration of the radio
base station. A memory unit stores spectrum information which is received by the switching
office from the base stations. Such spectrum information may include, for example, the blocking
20 rate at the base station, or measured spectrum characteristics at the geographic location of the
base station. In an advantageous embodiment, the memory unit is contained in the switching
office. The frequency spectrum manager receives the spectrum information from the switching
6 2 1 92248
office, analyzes the information based on stored rules, and sends base station reconfiguration
commands to the switching of fice based on the analysis of the spectrum information.
In addition, remote data collectors which are capable of measuring the radio spectrum in
a geographic location may be provided, which communicate with the frequency spectrum
5 manager. The frequency spectrum manager receives spectrum information from these remote
data collectors and analyzes this spectrum information in conjunction with the spectrum
information received from the switching office in order to make reconfiguration command
determinations.
In a multiple wireless communication services embodiment, the frequency spectrum
10 manager is in communication with the switching of fices of a plurality of wireless communication
services. The frequency spectrum manager receives spectrum information related to the services,
analyzes the information, and makes reconfiguration determinations based on the analysis. In
such an embodiment, the frequency spectrum manager makes determinations taking into
consideration the needs of the different services, and how the services interact with each other.
These and other advantages of the invention will be apparent to those of ordinary skill in
the art by reference to the following detailed description and the accompanying drawings.
Brief Dese. iplion of the Drawin~s
Fig. 1 shows a cellular communications system in accordance with the single service
20 embodiment of the present invention.
Fig. 2 shows a block diagram of the components of the frequency spectrum manager.
7 21 92248
Fig. 3 shows a block diagram of a cellular communications system in accordance with
the multiple service embodiment of the present invention.
Fig. 4 shows additional details of the cellular communications system shown in Fig. 3 .
Fig. 5 is a flowchart of an exemplary rule algorithm implemented by the frequency
5 spectrum manager.
Detailed Dcse. ;~lion
Fig. 1 shows a cellular communications system 100 in accordance with the single service
embodiment of the present invention. A cellular telephone network 102 is shown comprising a
10 plurality of radio base stations (RBS) 103, each of which is in communication with a mobile
switching center (MSC) 106. Such communication may be provided by a direct connection
between the RBS 103 and the MSC, as shown in Fig. 1. Such cellular telephone networks are
well known in the art, and the detailed operation and architecture of such a system will not be
discussed herein. It will be recognized by those skilled in the art that there may be multiple
MSCs 106 within the cellular telephone system 102, each of which would have at least one RBS
103 in communication with it. Only one MSC 106is shown in Fig. 1 to simplify the figure.
As is well known, the MSC 106 controls the functioning of the RBSs 103. Such control
includes the assignment of radio channels which each RBS 103 will use to communicate with
mobile end units. As used herein, a mobile end unit is any mobile device which communicates
20 with a wireless communication system. For example, in the cellular telephone network 102
shown in Fig. 1, a mobile end unit could be a mobile cellular telephone. The MSC 106is
connected to the public switched telephone network (PSTN) 108, such that a mobile end unit
8 2 i 92248
may communicate with a land line telephone 110. For more information on cellular telephone
systems see, The Cellular Radio Handbook, by Neil Boucher, ISBN: 0-930633-17-2, Quantum
Publishing, Mendocino, CA, June 1990; and Mobile Cellular Telecommunications Systems, by
William C. Y. Lee, ISBN: 0-07-037030-3, McGraw Hill Book Company, 1989, which are
S incorporated herein by reference.
In accordance with the principles of the present invention, a frequency spectrum manager
(FSM) device 112 communicates with the wireless telephone network 102 via the MSC 106. As
will be described in further detail below, the FSM 112 receives spectrum information which was
collected by the MSC 106. Alternatively, the FSM 112 may receive spectrum information from
the RBSs 103 directly. The FSM 112 may also receive spectrum information from one or more
remote commandable data collectors (RCDC) 114. These RCDCs 114 are devices which may be
positioned within the geographic service area of the wireless communication system, and which
measure the radio spectrum in the geographic location in which they are placed. The radio
spectrum measurements taken by the RCDCs 114 may include, for example, the signal strength
of various channels in use in the geographic location. The RCDCs 114 are used in order to
collect spectrum information in addition to the spectrum information collected by the MSC 106
through the RBSs 103. The RCDCs 114 may be directly connected to the FSM 112, they may be
connected through the PSTN 108, or they may communicate with the FSM through a wireless
communication channel. The RCDCs 114 are advantageously of the type described in copending
United States patent application serial no. 08/525,873 entitled Method And Apparatus For
Spectrum Analysis, filed September 8, 1995, which is incorporated herein by reference. The data
9 21 ~2248
received from the RCDCs 114 may be pre-processed before it is sent to the FSM 112 in
accordance with the techniques described in the above referenced patent application.
During operation, the MSC 106 stores system performance information for the RBSs103. Such system performance inforrnation may include:
The channels assigned to each RBS 103 . The set of channels assigned to a RBS
defines the radio channel configuration of the RBS.
The blocking rate of each RBS 103. A communication between a mobile end unitand an RBS is blocked if there are no available channels on which the mobile endunit and the RBS can communicate.
The dropped call rate of each RBS 103. The dropped call rate measures calls in
progress which are premàturely dropped by the RBS 103.
The attempt failure rate of each RBS 103. The attempt failure rate measures users
who request a communication channel but do not receive one.
Out of service statistics for channels allocated to RBS. Out of service statistics
measure how often a channel is taken out of service due to unacceptable quality. Bit error rate statistics for digital channels allocated to RBS. The bit error rate
measures errors on digital channels.
In addition, the MSC 106 stores interference information for the RBSs 103. Such
20 hllelrelellce information may include:
lo 2 I S22~8
Carrier / Illlel re~el (C / I) ratio information. Such information is a measurement of
the ratio of the signal strength on a channel when it is being used to communicate
with a mobile end unit with the strength of interference signals on that channel. For
example, if a channel is not being used in a cell site, the RBS 103 in that cell site
S may be used to measure the signal strength of signals that are being received on that
channel. Such signals may be received because that same channel may be in use for
communications in a different cell, in accordance with a channel reuse scheme. This
measured signal strength is the interferer signal strength. The signal strength
received by the RBS when the channel is being used for communication with an endunit within the cell is the carrier signal strength. The comparison of the interferer
signal strength with the carrier signal strength results in a C / I ratio.
In addition, if the cellular telephone network 102 provides digital cellular telephone
service, the MSC 106 stores Mobile Assisted Handoff (MAHO) information for mobile end units
operating within the service area. In accordance with the IS-54 and IS-136 air protocols, a
mobile end unit m~int~inc a MAHO list which contains the signal strengths of the signals that the
mobile end unit is receiving over control channels of nearby cells. For further information on
these air protocols, see, EWTIA Standard 553, "Mobile Station-Land Station Compatibility
Specification", September 1989, Electronic Industries Association, W~chin~ton, D.C.; EL~/TIA
Interim Standard IS-54-B "Cellular System Dual-Mode Mobile Station - BasestationCompatibility Standard", April, 1992, Electronic Industries Association, Washington, D.C.; and
EL~/TIA Interim Standard IS-136 "Cellular System Dual-Mode Mobile Station - Basestation:
21 92248
Digital Control Channel Compatibility Standard", April, 1995, Electronic Industries Association,
Washington, D.C., which are incorporated by reference herein. The channels included in a
mobile end unit MAHO list are variable, and an indication of which channels to include in the
MAHO list is sent to the mobile end unit by the MSC 106. The channels included in a MAHO
5 list generally consist of control channels used in the cells adjacent to the serving cell.
Periodically, the MAHO list of a mobile end unit is sent to, and stored in, the MSC 106.
Thus, in one embodiment, the MSC 106 stores the following spectrum information:
1. RBS system performance information;
2. RBS interference information; and
3. Mobile end unit MAHO information.
The FSM 112 receives the spectrum information from the MSC 106 and the spectrum
information from the RCDC's 114, processes the information, and makes spectrum management
decisions based on the information. The FSM 112 is shown in further detail in
Fig. 2. The FSM 112 may advantageously be implemented using a programmed digital computer
of the type which is well known in the art. Such a digital computer may be, for example, a
personal computer, mainframe computer, minicomputer, or workstation. The overall functioning
of the FSM 112 is controlled by a central processing unit (CPU) 202 executing computer
program instructions. CPU 202 is connected to a memory unit 204 which contains the computer
program instructions (i.e. control program) 206 which are executed by the CPU 202 and control
the overall function of the FSM 112. The memory unit 204 also contains rules 208 which are the
rules which the FSM 112 uses to manage the spectrum.
12 2 1 92248
The rules 208 may be stored in various ways. For example, rules 208 may be algorithms
which describe the actions to be taken based on various input data. Thus, the rules may be in the
form of computer program instructions which describe the algorithms. In addition, the rules may
be in the form of data tables which correlate input data with associated actions. One skilled in
5 the art would recognize that the rules may take other forms as well. Further various methods of
storing rules could be combined. One exemplary rule will be described in further detail below in
conjunction with Fig. 5.
The memory unit 204 also stores data 210. Such data 210 includes the spectrum
information 226 received from the MSC 106 and the RCDCs 114. Memory unit 204 also
contains channel assignment data 220. Channel assignment data 220 contains information
indicating which channels are assigned to which cells. In addition, the data 210 includes
geographic information 222 which contains information indicating the geographic location of the
cell sites. The data 210 also includes working data 224 which the FSM 112 uses during
processing. For example, during processing, the FSM will make certain calculations and will
15 need to store intermediate information. Data 210 is advantageously stored in a manner which
allows fast access to information needed for analysis by the FSM 112. For example, portions of
the data 210 could be stored as a relational (l~t~b~e in a well known manner.
Memory unit 204 may be any type of machine readable storage device. For example,
memory unit 204 may be a random access memory (RAM), a read only memory (ROM), a
20 programmable read only memory (PROM), an erasable programmable read only memory
(EPROM), an electronically erasable programmable read only memory (EEPROM), a magnetic
storage media (i.e. a magnetic disk), or an optical storage media (i.e. a CD-ROM). Further, the
13 2 1 9Z248
FSM 112 may contain various combinations of machine readable storage devices, which are
accessible by the CPU 202, and which are capable of storing a combination of computer program
code, rules, and data. CPU 202 is also connected to one or more user input devices 212, such as
a keyboard, mouse, light pen, touch screen, or microphone, which allow for user input to the
FSM 112. A user may be, for example, a network manager who manages the cellular telephone
network 102. CPU 202 is also connected to one or more user output devices 214, such as a
display screen, printer, or speakers, which allow a user to perceive output generated by the FSM
112. In addition, CPU 202 is connected to a data I/O port 216 which allows the FSM 112 to
communicate with external devices. Thus, data I/O port 216 has one or more communication
lines 218 which allow the FSM 112 to receive data from, and send data to, external devices, such
as MSC 106 and RCDCs 114. One skilled in the art of data communications would recognize
that there are various ways to implement a communication channel between the FSM 112 and
external devices, including wired and wireless communication channels. The details of such
communication techniques will not be described in detail herein.
During operation, the FSM 112 sends requests for spectrum information to the MSC 106
and the RCDCs 114. If the request is to the MSC 106, the request may specify a particular type
of spectrum information (e.g. system performance, hllellelence, MAHO) and the request may
specify spectrum information from a particular one of RBSs 103. The MSC 106 responds by
sending the requested information to the FSM 112. Upon receipt, the FSM 112 stores the
requested data as spectrum information 226 in the memory unit 204. Alternatively, instead of the
FSM 112 sending requests for spectrum information to the MSC 106, the MSC 106 may be
configured to periodically send spectrum information to the FSM 112.
14 21 92~48
The FSM 112 may also request specific information from the RCDCs 114. As disclosed
in copending U.S. Patent application serial no. 08/525,873, the RCDCs 114 may measure and
store various types of spectrum information, such as the signal strength of channels operating in
the geographic location of the RCDCs 114. Further, the RCDCs 114 may be remotelyconfigurable, in that the FSM 112 may send commands to the RCDCs 114 to request that the
RCDCs 114 measure particular characteristics of the spectrum. Upon receipt of information
from the RCDCs 114, the received information is stored as spectrum information 210 in the
memory unit 204. Alternatively, instead of the FSM 112 sending requests for spectrum
information to the RCDCs 114, the RCDCs 114 may be configured to periodically send spectrum
information to the FSM 112.
The FSM 112 processes the received spectrum information 210 according to stored
spectrum management rules 208. These rules 208 will vary depending on the particular
implementation. In general, the rules specify the actions which the FSM will take based on the
information received from the external devices. There are three types of actions:
1. Data Request: The FSM 112 may determine that it needs more information in order
to made a decision. Thus, the FSM 112 may request further information from the MSC
106 or a RCDC 114. In addition, an information request may include a request that a
RCDC 114 begin making certain types of measurements and that the RCDC 114 send the
requested information to the FSM 112 when the requested information has been
collected.
2 1 9224&
2. User Recommendation: The FSM 112 may determine that certain spectrum
management action would be advantageous, but the rules 208 may specify that such
action requires user intervention/approval. Thus, the FSM 112 may output such a
recommendation to a user output device 214 indicating the recommended action.
3. Reconfiguration Command: If the FSM 112 determines that certain spectrum
management action would be advantageous, and the rules 208 specify that such action
may be implemented by the FSM 112, the FSM 112 may take steps to implement the
required action. Such action would generally entail sending a reconfiguration command
to the MSC 106. For example, if the FSM determines that a channel should be
deallocated from one RBS 103 and reallocated to another RBS 103, the FSM 112 would
send a radio channel reconfiguration command specifying the required action to the
MSC 106. The MSC 106 would then take the appropriate action to reconfigure the RBSs
103. In an alternate embodiment, the FSM 112 sends radio channel reconfiguration
commands directly to the RBS 103, or to an intermediate device which controls the RBS
103.
The FSM 112 is an expert system which makes decisions based on stored rules 208. It is
noted that the stored rules 208 are rules of the type which, in prior art systems, have been
20 evaluated and applied by engineers performing spectrum analysis. An advantage of the present
invention is that these rules are now implemented in an expert system (FSM 112) which can
evaluate and implement the rules in real time. Thus, the stored rules 208 may be any type of
16 2 1 92248
rules which heretofore have been evaluated and implemented by engineers. Rules of the type
which are suitable to use in conjunction with the present invention are disclosed in, Mobile
Cellular Telecommunications Systems, by William C. Y. Lee. ISBN: 0-07-037030-3, McGraw
Hill Book Company, 1989, Chapter 8, pages 245-268, which is incorporated herein by reference.
5 The particular types of rules will vary depending on the implementation, and will not be set forth
in detail herein.
As shown in Fig. 1, a predictive modeler 116 is connected to the FSM 112. The
predictive modeler 116 is connected to a storage device containing modeling data 118. RF
engineers often use predictive modelers during the design or modification of wireless systems.
10 Predictive modeling data 118 comprises data which has been collected over time and which is
useful in making certain predictions about the wireless system. For example, modelling data 118
may contain data such as RBS 103 locations, antenna types used at different RBS 103 locations,
and channel allocations at various RBS 103 locations. The predictive modeler 116 includes a
processor executing computer program code which, in conjunction with the modelling data 118,
15 performs various calculations. For example, such calculations may predict the received signal
strength at a given location and the potential for interference between multiple RBS 103 sites. In
an advantageous embodiment, the predictive modeler 116 augments rules 208, and the FSM 112
uses the predictive modeler 116 in making decisions.
Fig. I shows a wireless system which provides a single service (cellular telephone
20 service). However, wireless service providers may provide more than one service, and it is
desirable to centrally manage these services when they share radio ~pe.;ll.l.ll. A block diagram of
a multiple service system in accordance with the present invention is shown in Fig. 3. Fig. 3
17 2 1 ~2248
shows a system 300 which contains the cellular telephone network 102 of Fig. 1, a personal base
station (PBS) network 302, and a cellular digital packet data (CDPD) network 304. Each of
these networks provides a wireless communication service and they share the same frequency
spectrum. In an advantageous embodiment, each of these networks are connected to a wireless
5 communication node 306, which provides for communication between the networks, and
between the networks and the FSM 112. One skilled in the art would recognize that there are
ways of providing communication between the networks other than wireless communication
node 306. In the configuration shown in Fig. 3, the FSM 112 is able to manage the shared
spectrum across the multiple wireless services.
10The system of Fig. 3 is shown in further detail in Fig. 4. The cellular telephone network
102 is as described above in conjunction with Fig. 1. The PBS network 302 comprises a
plurality of PBS devices 402 which are connected to the PSTN 108. A PBS 402 is a device
which allows a cellular telephone to function as a cordless land-line telephone when used in the
vicinity of the PBS. This system allows a user of the cellular telephone to communicate with
15other land line telephones 110 through the PSTN 108. When the PBS 402 is not communicating
with a cellular telephone, it will periodically connect to a private access visitor location register
(PA-VLR) 404 through the PSTN 108. Such a PBS network is described in detail in United
States patent application serial no. 08/526,066, entitled Wireless Communication System, filed
September 8, 1995, which is incorporated herein by reference. (What is referred to herein as a
20 personal base station (PBS) is referred to as a cordless cellular base station (CCBS) in United
States patent application Serial No. 08/526,066; and what is referred to herein as a private access
visitor location register (PA-VLR) is referred to as a cordless cellular base station visitor location
18 2 1 92248
register (CCBS VLR) in United States patent application Serial No. 08/526,066.) Only a brief
description of the PBS network 302 will be described herein. It will be recognized by those
skilled in the art that there may be multiple PA-VLR's 404 within the PBS network 302, each of
which would have one or more PBSs 402 connecting to it through the PSTN 108. Only one PA-
5 VLR 404 is shown in Fig. 4 to simplify the figure. When the cellular telephone is operating in thevicinity of the PBS 402, the PBS 402 will choose a channel which will be used for
communication between the PBS 402 and the cellular telephone. Such a channel is within the
frequency spectrum which is assigned to the wireless service provider, and which is used to
provide cellular telephone services through the cellular telephone network 102 and CDPD
services through the CDPD network 304. Therefore, the PBS 402 must choose a channel that
will not interfere with other services provided in the area. A list of possible channels from which
the PBS 402 may choose is stored in the PBS 402. This list is controlled by the PA-VLR 404 via
communication with the PBS 402. In one embodiment, such communication is accomplished by
the PBS 402 periodically initiating a connection with the PA-VLR 404 over the PSTN 108, at
which time the PA-VLR 404 may update the channel list stored in the PBS 402.
The CDPD network 304 comprises one or more mobile data base stations (MDBS) 406
in communication with a mobile data intermediate system 408. Such a CDPD network is
described in detail in Cellular Digital Packet Data System Specification, release 1.0, July 19,
1993, CDPD System Specification, 650 Town Center Drive, Suite 820, Costa Mesa, CA 92626,
20 which is incorporated herein by reference. Only a brief description of the CDPD network 304
will be described herein. It will be recognized by those skilled in the art that there may be
multiple MDISs 408 within the CDPD system 304, each of which would have a plurality of
19 2 1 92248
MDBSs 406 in communication with it. Only one MDIS 408 is shown in Fig. 4 to simplify the
figure. As is well known, the MDIS 408 controls the functioning of the MDBSs 406. Such
control includes the assignment of radio channels which each MDBS 406 will use to
communicate with mobile end units. A mobile end unit in the CDPD network 304 may be, for
example, a wireless mobile data terminal. The MDIS 408 is connected to a network 410, such
that a mobile end unit may communicate with a land line device or other mobile end units. The
network may be, for example, the Internet, or the PSTN.
In accordance with the multiple service embodiment of the invention shown in Figs. 3
and 4, the FSM 112 communicates with the various wireless service networks 102, 302, 304 via
the wireless communication node 306. The FSM 112 receives and sends data to the RCDCs 114
as described above.
As described above, mobile end units are devices which communicate with a wireless
communication network. It is noted that networks providing different services may communicate
with different types of mobile end units. For example, the cellular telephone network 102 may
communicate with a mobile telephone, and the CDPD network 304 may communicate with a
wireless mobile data terminal. However, it is noted that networks providing different services
may also communicate with mobile end units of the same type. For example, the cellular
telephone network 102 and the CDPD network 304 may both communicate with a hybrid mobile
end unit which is capable of communicating with both networks.
The communication between the cellular telephone network 102 and the FSM 112 is as
described above. With respect to the PBS network 302, the PA-VLR 404 stores spectrum
information for each of the PBSs 402. Such spectrum information includes channel allocation
20 2 1 92248
data for each of the PBSs 402. This channel allocation data includes a list of channels from
which a PBS 402 may choose a channel for communication with a cellular telephone operating in
the vicinity of the PBS 402. In addition, spectrum information for a PBS 402 may include
system perforrnance information (e.g. blocking rate, dropped call rate, attempt failure rate, out of
S service statistics, bit error rate statistics) and interference information (e.g. C/l ratio). Such
spectrum information may be requested by, and sent to, the FSM 112 via the wireless
communications node 306. The FSM 112 is able to control the functioning of the PBSs 402 by
sending commands to the PA-VLR 404 via the wireless communications node 306. For example,
if the information received by the FSM 112 indicates that a certain PBS 402 is having difficulty
finding an acceptable communication channel, the FSM 112 can adjust the channels available to
the PBS 402 by sending channel allocation reconfiguration commands to the PA-VLR 404. The
PA-VLR 404 in turn will update the list of channels stored in the PBS 402 the next time
communication is established between the PA-VLR 404 and the PBS 402 via the PSTN 108.
With respect to the CDPD network 304, the MDIS 408 stores spectrum information of
the MDBSs 406 in a manner similar to the manner in which the MSC 106 stores spectrum
information of the RBSs 103, as described above. Thus, the FSM 112 receives data from the
MDIS 408 via the wireless communication node 306. Further, the MDIS 408 controls the
MDBSs 406 in a manner similar to that in which the MSC 106 conkols the RBSs 103. Thus, the
FSM 112 may send similar control information to the MDIS 408 to control the MDBSs 406.
In the embodiment described above in conjunction with Fig. 1, the FSM 112 manages the
radio spectrum with respect to a single service. In the embodiment of Fig. 4, the FSM 112
manages the radio spectrum across various services. However, the basic functioning of the FSM
21 2 1 92248
112 is the same as described above in conjunction with Fig. 1. In the multiple service
embodiment, the rules 208 which the FSM 112 uses to manage the spectrum, must take into
account the various data available from the different networks and the RCDCs 114. Further, the
decisions made by the FSM 112 in accordance with the rules 208 will be more complex, in that a
5 reconfiguration of the spectrum usage in one service may affect other services as well. As stated
above, the stored rules 208 are rules of the type which, in prior art system, have been evaluated
arid applied by engineers during spectrum analysis. The rules for m~n:~ging spectrum across
various technologies are complex, and the present invention implements these rule in an expert
system (FSM 112) which can evaluate and implement the rules in real time. Rules ofthe type
10 which are suitable to use in conjunction with the present invention are disclosed in Mobile
Cellular Telecommunications Systems, by William C. Y. Lee, ISBN: 0-07-037030-3, McGraw
Hill Book Company, 1989, Chapter 8, pages 245-268, which is incorporated herein by reference.
The rules 208 which would be used in a multiple service application would vary depending on
the particular application, and such detailed rules will not be described herein. However, for
15 illustration purposes, the following rule algorithm is supplied as an example.
An illustrative rule algorithm is described in conjunction with Fig. 5. Assume for
purposes of this description, that this rule algorithm is being carried out with respect to the
cellular telephone network 102. It would be recognized by one skilled in the art that this rule
could be carried out with respect to the personal base station network 302 or the cellular digital
20 packet data network 304. As described above, the rule algorithm shown in Fig. 5 is implemented
as computer program instructions stored as rules 208 in memory unit 204. The program
instructions are executed by CPU 202 in order to implement the stored rules.
22 2 ~ 92248
The rule algorithm is initiated in step 500. In step 502, the system performanceinformation for a cell within the cellular telephone network 102 is analyzed. As discussed above,
one type of information received by the FSM 112 from the MSC 106 is system performance
information for the RBSs 103 in the cells. This system performance information is retrieved
from the spectrum information 226 in the memory unit 204 and the system performance
information is analyzed to determine if the demand and supply of channels within the cell are
well matched. Such analysis could be based on the blocking rate ofthe RBS 103 within the cell.
The demand may be too high, too low, or well matched, with respect to the supply of channels.
In step 504 the results of the demand analysis are examined. If the demand is too high
compared to the supply, then in step 508 it is determined, with reference to geographic
information 222 and spectrum information 226, whether spectrum information for the geographic
location of the cell being analyzed is available. If the required data is not available, the FSM 112
makes a data request in step 506, and the further processing of this rule algorithm waits for a
response. Such a data request may be to the MSC 106 requesting that one of the RBSs 103
connected to the MSC 106 makes certain spectrum measurements and passes those
measurements back to the FSM 112 through the MSC 106. The data request may also be to a
RCDC 114 in the appropliate geographic area, requesting that the RCDC 114 take certain
spectrum measurements and that those measurements be returned to the FSM 112. Upon receipt
of the requested information, or if the information is available at the outset, channel quality
projections are performed in step 510. During channel quality projections, all, or a portion of,
the channels which are available to the wireless service provider are evaluated to determine if
any of the channels would provide acceptable quality at the cell (requesting cell) which needs
23 21 92248
more channels to satisfy its demand. Those skilled in the art will recognize that there are various
ways to determine whether a channel would be acceptable at a particular cell. For example,
Carrier/Interferer ratio information could be analyzed to determine the projected quality of a
channel at a particular location. In addition, the predictive modeler 116 and the associated
5 modeling data 118, could be used to make predictions regarding the quality of a channel at a
particular cell. In step 512 it is determined whether any of the channels analyzed in step 510
would provide acceptable quality. If not, then in step 518 an alarm output is provided to the user.
Such an alarm output may be a notice to a user via user output device 214 that a particular cell
has demand greater than supply, and that no channel available to the service provider would
10 provide acceptable quality. The rule algorithm would end in step 538.
If it were determined in step 512 that at least one of the channels analyzed in step 510
would provide acceptable quality, then in step 514 inter-service channel analysis is performed on
these acceptable channels. Inter-service channel analysis is performed in order to determine
whether any of the acceptable channels are available to be assigned to the requesting cell. The
FSM 112 ~ccesses channel assignment information 220 to determine if an acceptable channel is
already assigned to another cell within the cellular telephone network 102, the CDPD network
304, or to a PBS 402 within the PBS network 302. If it is determined that a channel is assigned
to another cell or PBS 402, then the FSM 112 accesses the geographic information 222 and looks
up the geographic location of that cell or PBS to determine if the assignment of the channel to the
20 requesting cell would illle- rel e with the existing use of the channel. If the FSM determines that
there would not be any illl~lr~lt;llce, then the channel could be assigned to the requesting cell. If
the assignment of the channel to the requesting cell would cause inl~lr~.cllce with the existing
24 2 1 9224&
use of the channel, then the channel cannot be assigned to the requesting cell. Such channel
analysis is carried out until an acceptable channel is found to be available or until it is
determined that no acceptable channels are available.
If it is determined in step 516 that no channels were found to assign to the requesting
cell, then an alarm output is sent to the user output device 214 in step 518 indicating that the
requesting cell requires addition channel capacity, but that an acceptable and available channel
could not be found. The rule algorithm then ends in step 538. If it is determined in step 516 that
at least one acceptable channel is available, then in step 520 the channel assignment information
220 is updated, and in step 522 the FSM 112 sends a reconfiguration command to the MSC 106
to command the MSC 106 to assign the channel to the RBS 103 ofthe requesting cell. The rule
algorithm ends in step 538.
Returning now to step 504, if the demand is too low compared to the supply (i.e. there is
an oversupply of channels at the cell), then in step 524 it is determined, with reference to
geographic information 222 and spectrum information 226 whether spectrum information for the
l S geographic location of the cell being analyzed is available. If the required data is not available,
the FSM 112 makes a data request in step 526, and the further processing of this rule algorithm
waits for a response. Such a data request may be to the MSC 106 requesting that one of the
RBSs 103 connected to the MSC 106 makes certain spectrum measurements and passes those
measurements back to the FSM 112 through the MSC 106. The data request may also be to a
RCDC 114 in the a~ opliate geographic area, requesting that the RCDC 114 take certain
spectrum measurements and that those measurements be returned to the FSM 112. Upon receipt
of the requested information, or if the information is available at the outset, channel quality
25 2 ! 92248
analysis for each of the channels currently assigned to the cell are perforrned in step 528. The
channels which are assigned to the cell are determined with reference to channel assignment
inforrnation 220. Based on the quality analysis, the channel(s) to unassign are determined in
step 530. For example, in one embodiment, the channel(s) with the lowest quality may be
unassigned. In step 532, an output alarm is sent to user output device 214 to notify a user that the
cell had too much supply, and that a channel(s) was unassigned from that cell. In step 534, the
channel assignment information 220 is updated to reflect the unassignment. In step 536, the
FSM 112 sends a reconfiguration command to the MSC 106 to command the MSC 106 tounassign the channel from the cell. The rule algorithm then ends in step 538.
Returning again to step 504, if the demand and supply at a cell are well matched, then no
further processing is necessary, and the rule algorithm ends in step 538.
It is to be noted that modifications could be made to the above rule algorithm. For
example, if the FSM 112 determines in steps 514 and 516 that all acceptable channels are
currently assigned to other cells, it is possible to program the FSM 112 to make a priority
determination as to whether a reassignment of a channel should be made from the cell which
currently is assigned the channel to the requesting cell. In such an embodiment, priority
inforrnation could be stored in data area 210 in memory unit 204. Based on such priority data,
the FSM 112 may determine that a cell with higher priority can take a channel away from a cell
with lower priority.
The foregoing Detailed Description is to be understood as being in every respectillustrative and exemplary, but not restrictive. It is to be understood thatthe embodiments shown
and described herein are only illustrative of the principles of the present invention and that
26
2 1 92248
various modifications may be implemented by those skilled in the art without departing from the
- scope and spirit of the invention. For example, the present invention is described in connection
with the wireless services of telephone, CDPD, and PBS. However, the invention is not limited
to use in
5 connection with such services. The invention could be used to manage radio spectrum with
respect to other services.
