Note: Descriptions are shown in the official language in which they were submitted.
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MEDIUM ACCESS CONTROL FOR WIRELESS SYSTEMS
TECHNICAL FIELD
This application relates to wireless communication techniques.
BACKGROUND
Draft IEEE 802.16m System Description Document, IEEE 802.16m-08/003r1,
dated April 15th 2008, states that: "This [802.16m] standard amends the IEEE
802.16 WirelessMAN-OFDMA specification to provide an advanced air
interface for operation in licensed bands. It meets the cellular layer
requirements of IMT-Advanced next generation mobile networks. This
amendment provides continuing support for legacy WirelessMAN-OFDMA
equipment... The purpose of this standard is to provide performance
improvements necessary to support future advanced services and
applications, such as those described by the ITU in Report ITU-R M.2072."
Also, IEEE 802.16m System Requirements Document, IEEE 802.16m-
07/002r4), states that: "Overhead, including overhead for control signaling as
well as overhead related to bearer data transfer, for all applications shall
be
reduced as far as feasible without compromising overall performance and
ensuring proper support of systems features."
SUMMARY
According to a first broad aspect, the present invention seeks to provide a
method for execution by a mobile station in a mobile communications network,
the method comprising: receiving a first mobile station identifier from the
network during a ranging operation involving the mobile station; using the
first
mobile station identifier to extract the contents of at least one message
received from the network during said ranging operation; receiving a second
mobile station identifier subsequent to completion of the ranging operation;
and using the second mobile station identifier, different from the first
mobile
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station identifier, to extract the contents of at least one message received
from
the network after said ranging operation is complete.
According to a second broad aspect, the present invention seeks to provide a
mobile station comprising: receive circuitry configured for: receiving
messages
from a network, at least one of the messages received during a ranging
operation and comprising a first mobile station identifier, and receiving a
second mobile station identifier subsequent to completion of the ranging
operation; and a processing entity configured for extracting the contents of
at
least one message received from the network during said ranging operation
based on the first mobile station identifier and for extracting the contents
of at
least one message received from the network after said ranging operation is
complete based on the second mobile station identifier different from the
first
mobile station identifier.
According to a third broad aspect, the present invention seeks to provide a
computer-readable storage medium comprising computer-readable instructions
which, when executed by a computing entity in a mobile station, cause the
mobile station to: receive messages from a network, at least one of the
messages received during a ranging operation and comprising a first mobile
station identifier; extract the contents of at least one message received from
a
network during a ranging operation based on using a first mobile station
identifier; receive a second mobile station identifier subsequent to
completion
of the ranging operation; and extract the contents of at least one message
received from the network after said ranging operation is complete based on
using the second mobile station identifier different from the first mobile
station
identifier.
According to a fourth broad aspect, the present invention seeks to provide a
mobile station comprising: means for receiving messages from a network, at
least one of the messages received during a ranging operation and
comprising a first mobile station identifier; means for extracting the
contents of
at least one message received from the network during said ranging operation
based on the first mobile station identifier; means for receiving a second
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mobile station identifier subsequent to completion of the ranging operation;
and means for extracting the contents of at least one message received from
the network after said ranging operation is complete based on the second
mobile station identifier different from the first mobile station identifier.
According to a fifth broad aspect, the present invention seeks to provide a
method for execution by a base station in a mobile communications network,
comprising: outputting a first message destined for a mobile station, the
first
message including a first mobile station identifier for use by the mobile
station
during a ranging operation; determining that said ranging operation is
complete; outputting a second message destined for the mobile station
subsequent to completion of the ranging operation, the second message
including a second mobile station identifier for use by the mobile station in
subsequent communication with the network.
According to a sixth broad aspect, the present invention seeks to provide a
base station comprising: transmit circuitry configured for outputting messages
destined for a mobile station; a processing entity configured for determining
when a ranging operation involving a mobile station is complete, for inserting
into a first one of the messages transmitted during the ranging operation a
first
mobile station identifier for use by the mobile station during said ranging
operation, and for inserting into a second one of the messages transmitted
subsequent to completion of the ranging operation a second mobile station
identifier for use by the mobile station after said ranging operation is
complete.
According to a seventh broad aspect, the present invention seeks to provide a
computer-readable storage medium comprising computer-readable instructions
which, when executed by a computing entity in a base station, cause the base
station to: insert into a first message destined for a mobile station involved
in a
ranging operation a first mobile station identifier for use by the mobile
station
during said ranging operation; and insert into a second message transmitted
subsequent to completion of the ranging operation and destined for the mobile
station a second mobile station identifier for use by the mobile station after
said ranging operation is complete.
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According to an eighth broad aspect, the present invention seeks to provide a
base station comprising: means for outputting messages destined for a mobile
station; means for determining when a ranging operation involving a mobile
station is complete; means for inserting into a first one of the messages
transmitted during the ranging operation a first mobile station identifier for
use
by the mobile station during said ranging operation; and means for inserting
into a second one of the messages transmitted subsequent to completion of
the ranging operation a second mobile station identifier for use by the mobile
station after said ranging operation is complete.
According to a ninth broad aspect, the present invention seeks to provide a
method for data transmission, comprising: accessing a memory to obtain an
amount of data associated with a service flow established with a recipient and
to be transmitted thereto; accessing the memory to obtain control information
characterizing the service flow; formulating a datagram by placing at least
some of the data into a payload of the datagram and placing, in a header of
the datagram, the control information characterizing the service flow, wherein
the control information characterizing the service flow occupies a fewer than
sixteen bits of the header; modulating a radio frequency signal with the
datagram and releasing the radio frequency signal over a wireless medium.
Other aspects and features of the present application will become apparent to
those ordinarily skilled in the art upon review of the following description
of
specific embodiments of a disclosure in conjunction with the accompanying
drawing figures and appendices.
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BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present application will now be described, by way of
example only, with reference to the accompanying drawing figures, wherein
like reference numerals are used in different figures to denote similar
elements.
FIG. 1 is a block diagram of a cellular communication system.
FIG. 2 is a block diagram of an example base station that might be used to
implement some embodiments of the present 5 application.
FIG. 3 is a block diagram of an example wireless terminal that might be
used to implement some embodiments of the present application.
FIG. 4 is a block diagram of an example relay station that might be used to
implement some embodiments of the present application.
FIG. 5 is a block diagram of a logical breakdown of an example OFDM
transmitter architecture that might be used to implement some embodiments
of the present application.
FIG. 6 is a block diagram of a logical breakdown of an example OFDM
receiver architecture that might be used to implement some embodiments of
the present application.
FIG. 7 is Figure 1 of IEEE 802.16m-08/003r1, an Example of overall
network architecture.
FIG. 8 is Figure 2 of IEEE 802.16m-08/003r1, a Relay Station in overall
network architecture.
FIG. 9 is Figure 3 of IEEE 802.16m-08/003r1, a System Reference Model.
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FIG. 10 is Figure 4 of IEEE 802.16m-08/003r1, The IEEE 802.16m
Protocol Structure.
FIG. 11 is Figure 5 of IEEE 802.16m-08/003r1, The IEEE 802.16m
MS/BS Data Plane Processing Flow.
FIG. 12 is Figure 6 of IEEE 802.16m-08/003r1, The IEEE 802.16m MS/BS
Control Plane Processing Flow.
FIG. 13 is Figure 7 of IEEE 802.16m-08/003r1, Generic protocol
architecture to support multicarrier system.
FIG. 14 is a flow diagram showing a message flow between a base station
and a mobile station involved in a ranging operation therewith, in the case of
initial network entry, in accordance with a specific non-limiting embodiment
of
the present invention.
FIG. 15 conceptually illustrates a header of a medium access control protocol
data unit (MAC PDU).
FIG. 16 shows a variant of the flow diagram in FIG. 14.
FIG. 17 shows another variant of the flow diagram in FIG. 14.
FIG. 18 is a flow diagram showing a message flow between a base station
and a mobile station involved in a ranging operation therewith, in the case
where the mobile station re-enters the network from an idle state, in
accordance with a specific non-limiting embodiment of the present invention.
FIG. 19 is a flow diagram showing a message flow between a base station
and a mobile station involved in a ranging operation therewith, in the case of
a
location update, in accordance with a specific non-limiting embodiment of the
present invention.
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FIG. 20 shows a state diagram of a mobile station, illustrating a number of
possible states, including an initialization state, an access state, a
connected
state and an idle state.
FIG. 21 shows in greater detail how the mobile station transitions into and
out
of the initialization state.
FIG. 22 shows in greater detail how the mobile station transitions into and
out
of the access state.
FIG. 23 shows in greater detail how the mobile station transitions into and
out
of the connected state.
FIG. 24 shows in greater detail how the mobile station transitions into and
out
of the idle state.
It is to be expressly understood that the description and drawings are only
for
the purpose of illustration of certain embodiments of the invention and are an
aid for understanding. They are not intended to be a definition of the limits
of
the invention.
DETAILED DESCRIPTION
In the present disclosure, reference has been made to IEEE 802.16 and IEEE
802.16m. In the below, the term "IEEE 802.16" is meant to encompass
versions of IEEE Std 802.16-, including but not limited to IEEE Std 802.16-
2004 and -2009, while the term "IEEE 802.16m" is meant to encompass
versions of IEEE 802.16m-08, including but not limited to 802.16m-08/003r3,
and /003r1 and /003r9a. All of the foregoing documents, are available from the
IEEE, 3 Park Avenue, New York, NY 10016-5997, USA, and can be consulted
to in order to obtain additional background information as to the context in
which certain embodiments of the present invention may find application.
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Referring to the drawings, FIG. 1 shows a base station controller (BSC) 10
which controls wireless communications within multiple cells 12, which cells
are served by corresponding base stations (BSs) 14. In some configurations,
each cell is further divided into multiple sectors 13 or zones (not shown). In
general, each BS 14 facilitates communications with mobile stations (MSs)
16, which are within the cell 12 associated with the corresponding BS 14. The
MSs 16 can alternatively be referred to as mobile terminals, wireless
stations,
wireless terminals, subscriber stations, subscriber terminals, etc.
The movement of the MSs 16 in relation to the BSs 14 results in significant
fluctuation in channel conditions. As illustrated, the BSs 14 and MSs 16 may
include multiple antennas to provide spatial diversity for communications. In
some configurations, relayes (or relay stations ¨ RSs) 15 may assist in
communications between BSs 14 and MSs 16. MSs 16 can be handed off 18
from any cell 12, sector 13, zone (not shown), BS 14 or RS 15 to an other cell
12, sector 13, zone (not shown), BS 14 or RS 15. In some configurations,
BSs 14 communicate with each and with another network (such as a core
network or the Internet, both not shown) over a backhaul network 11. In some
configurations, a BSC 10 is not needed.
With reference to FIG. 2, an example of a BS 14 is illustrated. The BS 14
generally includes a control system 20, a baseband processor 22, transmit
circuitry 24, receive circuitry 26, multiple antennas 28, and a network
interface 30. The receive circuitry 26 receives radio frequency signals
bearing information from one or more remote transmitters provided by MSs
16 (illustrated in FIG. 3) and RSs 15 (illustrated in FIG. 4). A low noise
amplifier and a filter (not shown) may cooperate to amplify and remove
broadband interference from the signal for processing. Downconversion and
digitization circuitry (not shown) will then downconvert the filtered,
received
signal to an intermediate or baseband frequency signal, which is then
digitized into one or more digital streams.
The baseband processor 22 processes the digitized received signal to extract
the information or data bits conveyed in the received signal. This processing
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typically comprises demodulation, decoding, and error correction operations.
As such, the baseband processor 22 is generally implemented in one or more
digital signal processors (DSPs) or application-specific integrated circuits
(ASICs). The received information is then sent across a wireless network via
the network interface 30 or transmitted to another MS 16 serviced by the BS
14, either directly or with the assistance of a RS 15.
On the transmit side, the baseband processor 22 receives digitized data,
which may represent voice, data, or control information, from the network
interface 30 under the control of control system 20, and encodes the data for
transmission. The encoded data is output to the transmit circuitry 24, where
it is modulated by one or more carrier signals having a desired transmit
frequency or frequencies. A power amplifier (not shown) will amplify the
modulated carrier signals to a level appropriate for transmission, and deliver
the modulated carrier signals to the antennas 28 through a matching network
(not shown). Modulation and processing details are described in greater
detail below.
With reference to FIG. 3, an example of a MS 16 is illustrated. Similarly to
the BS 14, the MS 16 will include a control system 32, a baseband processor
34, transmit circuitry 36, receive circuitry 38, multiple antennas 40, and
user
interface circuitry 42. The receive circuitry 38 receives radio frequency
signals bearing information from one or more BSs 14 and RSs 15. A low
noise amplifier and a filter (not shown) may cooperate to amplify and remove
broadband interference from the signal for processing. Downconversion and
digitization circuitry (not shown) will then downconvert the filtered,
received
signal to an intermediate or baseband frequency signal, which is then
digitized into one or more digital streams.
The baseband processor 34 processes the digitized received signal to extract
the information or data bits conveyed in the received signal. This processing
typically comprises demodulation, decoding, and error correction operations.
The baseband processor 34 is generally implemented in one or more digital
signal processors (DSPs) and application specific integrated circuits (ASICs).
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For transmission, the baseband processor 34 receives digitized data, which
may represent voice, video, data, or control information, from the control
system 32, which it encodes for transmission. The encoded data is output to
the transmit circuitry 36, where it is used by a modulator to modulate one or
more carrier signals that is at a desired transmit frequency or frequencies. A
power amplifier (not shown) will amplify the modulated carrier signals to a
level appropriate for transmission, and deliver the modulated carrier signal
to
the antennas 40 through a matching network (not shown). Various
modulation and processing techniques available to those skilled in the art are
used for signal transmission between the mobile terminal and the base
station, either directly or via the relay station.
In orthogonal frequency division multiplexing (OFDM) modulation, the
transmission band is divided into multiple, orthogonal carrier waves. Each
carrier wave is modulated according to the digital data to be transmitted.
Because OFDM divides the transmission band into multiple carriers, the
bandwidth per carrier decreases and the modulation time per carrier
increases. Since
the multiple carriers are transmitted in parallel, the
transmission rate for the digital data, or symbols, on any given carrier is
lower
than when a single carrier is used.
OFDM modulation utilizes the performance of an Inverse Fast Fourier
Transform (IFFT) on the information to be transmitted. For demodulation, the
performance of a Fast Fourier Transform (FFT) on the received signal
recovers the transmitted information. In practice, the IFFT and FFT are
provided by digital signal processing carrying out an Inverse Discrete Fourier
Transform (IDFT) and Discrete Fourier Transform (DFT), respectively.
Accordingly, the characterizing feature of OFDM modulation is that orthogonal
carrier waves are generated for multiple bands within a transmission channel.
The modulated signals are digital signals having a relatively low transmission
rate and capable of staying within their respective bands. The individual
carrier waves are not modulated directly by the digital signals. Instead, all
carrier waves are modulated at once by IFFT processing.
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Orthogonal Frequency Division Multiple Access (OFDMA) is a multi-user
version of the OFDM digital modulation scheme. Multiple access is achieved
in OFDMA by assigning subsets of subcarriers to individual users. This
allows simultaneous low data rate transmission from several users. Like
OFDM, OFDMA employs multiple closely spaced sub-carriers, but the sub-
carriers are divided into groups of sub-carriers. Each group is named a sub-
channel. The sub-carriers that form a sub-channel need not be adjacent. In
the downlink, a sub-channel may be intended for different receivers. In the
uplink, a transmitter may be assigned one or more sub-channels. Sub-
channelization defines sub-channels that can be allocated to MSs depending
on their channel conditions and data requirements. Using sub-channelization,
within the same time slot a BS can allocate more transmit power to user
devices (MSs) with lower SNR (Signal-to-Noise Ratio), and less power to user
devices with higher SNR. Sub-channelization also enables the BS to allocate
higher power to sub-channels assigned to indoor MSs resulting in better in-
building coverage. Sub-channelization in the uplink can save a user device
transmit power because it can concentrate power only on certain sub-
channel(s) allocated to it. This power-saving feature is particularly useful
for
battery-powered user devices.
In operation, OFDM can be used for at least downlink (DL) transmission from
the BSs 14 to the MSs 16. Each BS 14 is equipped with "n" transmit
antennas 28 (n >=1), and each MS 16 is equipped with "m" receive antennas
40 (m >=1). Notably, the respective antennas can be used for reception and
transmission using appropriate duplexers or switches and are so labelled only
for clarity. (When RSs 15 are used, OFDM may be used for downlink
transmission from the BSs 14 to the RSs 15 and from RSs 15 to the MSs 16.)
In the uplink direction, the MS 16 may use the OFDMA digital modulation
scheme. (When RSs 15 are used, OFDMA may be used for uplink
transmission from the BSs 14 to the RSs 15 and from RSs 15 to the MSs 16.)
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It should be appreciated that the choice of OFDM in the downlink and OFDMA
in the uplink is by no means limiting, and that other modulation schemes could
be used.
With reference to FIG. 4, an example of a RS 15 is illustrated. Similarly to
the
BS 14, and the MS 16, the RS 15 will include a control system 132, a
baseband processor 134, transmit circuitry 136, receive circuitry 138,
multiple
antennas 130, and relay circuitry 142. The relay circuitry 142 enables the RS
to assist in communications between a BS 14 and MSs 16. The receive
10 circuitry 138 receives radio frequency signals bearing information from
one or
more BSs 14 and MSs 16. A low noise amplifier and a filter (not shown) may
cooperate to amplify and remove broadband interference from the signal for
processing. Downconversion and digitization circuitry (not shown) will then
downconvert the filtered, received signal to an intermediate or baseband
15 frequency signal, which is then digitized into one or more digital
streams.
The baseband processor 134 processes the digitized received signal to
extract the information or data bits conveyed in the received signal. This
processing typically comprises demodulation, decoding, and error correction
operations. The baseband processor 134 is generally implemented in one or
more digital signal processors (DSPs) and application specific integrated
circuits (ASICs).
For transmission, the baseband processor 134 receives digitized data, which
may represent voice, video, data, or control information, from the control
system 132, which it encodes for transmission. The encoded data is output to
the transmit circuitry 136, where it is used by a modulator to modulate one or
more carrier signals that is at a desired transmit frequency or frequencies. A
power amplifier (not shown) will amplify the modulated carrier signals to a
level appropriate for transmission, and deliver the modulated carrier signal
to
the antennas 130 through a matching network (not shown). Various
modulation and processing techniques available to those skilled in the art are
used for signal transmission between the mobile terminal and the base
station, either directly or indirectly via a relay station, as described
above.
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With reference to FIG. 5, a logical OFDM transmission architecture will be
described. Initially, the BSC 10 will send data to be transmitted to various
MSs
16 to the BS 14, either directly or with the assistance of a RS 15. The BS 14
may use the channel quality indicators (CQ1s) associated with the mobile
terminals to schedule the data for transmission as well as select appropriate
coding and modulation for transmitting the scheduled data. The CQls may be
directly from the MSs 16 or determined at the BS 14 based on information
provided by the MSs 16. In either case, the CQI for each MS 16 is a function
of the degree to which the channel amplitude (or response) varies across the
OFDM frequency band.
Scheduled data 44, which is a stream of bits, is scrambled in a manner
reducing the peak-to-average power ratio associated with the data using data
scrambling logic 46. A cyclic redundancy check (CRC) for the scrambled
data is determined and appended to the scrambled data using CRC adding
logic 48. Next, channel coding is performed using channel encoder logic 50
to effectively add redundancy to the data to facilitate recovery and error
correction at the MS 16. Again, the channel coding for a particular MS 16 is
based on the CQI. In some implementations, the channel encoder logic 50
uses known turbo encoding techniques. The encoded data is then processed
by rate matching logic 52 to compensate for the data expansion associated
with encoding.
Bit interleaver logic 54 systematically reorders the bits in the encoded data
to
minimize the loss of consecutive data bits. The resultant data bits are
systematically mapped into corresponding symbols depending on the chosen
baseband modulation by mapping logic 56. Quadrature Amplitude
Modulation (QAM) or Quadrature Phase Shift Key (QPSK) modulation can be
used, by way of example. The degree of modulation can be chosen based
on the CQI for the particular mobile terminal. The symbols may be
systematically reordered to further bolster the immunity of the transmitted
signal to periodic data loss caused by frequency selective fading using
symbol interleaver logic 58.
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At this point, groups of bits have been mapped into symbols representing
locations in an amplitude and phase constellation. When spatial diversity is
desired, blocks of symbols are then processed by space-time block code
(STC) encoder logic 60, which modifies the symbols in a fashion making the
transmitted signals more resistant to interference and more readily decoded
at a MS 16. The STC encoder logic 60 will process the incoming symbols
and provide "n" outputs corresponding to the number of transmit antennas 28
for the BS 14. The control system 20 and/or baseband processor 22 as
described above with respect to FIG. 5 will provide a mapping control signal
to control STC encoding. At this point, assume the symbols for the "n"
outputs are representative of the data to be transmitted and capable of being
recovered by the MS 16.
For the present example, assume the BS 14 has two antennas 28 (n=2) and
the STC encoder logic 60 provides two output streams of symbols.
Accordingly, each of the symbol streams output by the STC encoder logic 60
is sent to a corresponding IFFT processor 62, illustrated separately for ease
of understanding. Those skilled in the art will recognize that one or more
processors may be used to provide such digital signal processing, alone or in
combination with other processing described herein. In an example, the IFFT
processors 62 operate on the respective symbols to provide an inverse
Fourier Transform. The output of the IFFT processors 62 provides symbols in
the time domain. The time domain symbols are grouped into frames, which
are associated with a prefix by prefix insertion logic 64. Each of the
resultant
signals is up-converted in the digital domain to an intermediate frequency and
converted to an analog signal via the corresponding digital up-conversion
(DUC) and digital-to-analog (D/A) conversion circuitry 66. The resultant
(analog) signals are then simultaneously modulated at the desired RE
frequency, amplified, and transmitted via the RF circuitry 68 and antennas 28.
Notably, pilot signals known by the intended MS 16 are scattered among the
sub-carriers. The MS 16, which is discussed in detail below, can use the pilot
signals for channel estimation.
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Reference is now made to FIG. 6 to illustrate reception of the transmitted
signals by a MS 16, either directly from BS 14 or with the assistance of RS
15.
Upon arrival of the transmitted signals at each of the antennas 40 of the MS
16, the respective signals are demodulated and amplified by corresponding
RF circuitry 70. For the sake of conciseness and clarity, only one of the two
receive paths is described and illustrated in detail. Analog-to-digital (ND)
converter and down-conversion circuitry 72 digitizes and downconverts the
analog signal for digital processing. The resultant digitized signal may be
used by automatic gain control circuitry (AGC) 74 to control the gain of the
amplifiers in the RF circuitry 70 based on the received signal level.
Initially, the digitized signal is provided to synchronization logic 76, which
includes coarse synchronization logic 78, which buffers several OFDM
symbols and calculates an auto-correlation between the two successive
OFDM symbols. A resultant time index corresponding to the maximum of the
correlation result determines a fine synchronization search window, which is
used by fine synchronization logic 80 to determine a precise framing starting
position based on the headers. The output of the fine synchronization logic
80 facilitates frame acquisition by frame alignment logic 84. Proper framing
alignment is important so that subsequent FFT processing provides an
accurate conversion from the time domain to the frequency domain. The fine
synchronization algorithm is based on the correlation between the received
pilot signals carried by the headers and a local copy of the known pilot data.
Once frame alignment acquisition occurs, the prefix of the OFDM symbol is
removed with prefix removal logic 86 and resultant samples are sent to
frequency offset correction logic 88, which compensates for the system
frequency offset caused by the unmatched local oscillators in the transmitter
and the receiver. The synchronization logic 76 can include frequency offset
and clock estimation logic 82, which is based on the headers to help estimate
such effects on the transmitted signal and provide those estimations to the
correction logic 88 to properly process OFDM symbols.
At this point, the OFDM symbols in the time domain are ready for conversion
to the frequency domain using FFT processing logic 90. The results are
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frequency domain symbols, which are sent to processing logic 92. The
processing logic 92 extracts the scattered pilot signal using scattered pilot
extraction logic 94, determines a channel estimate based on the extracted
pilot signal using channel estimation logic 96, and provides channel
responses for all sub-carriers using channel reconstruction logic 98. In order
to determine a channel response for each of the sub-carriers, the pilot signal
is essentially multiple pilot symbols that are scattered among the data
symbols throughout the OFDM sub-carriers in a known pattern in both time
and frequency. Continuing with FIG. 6, the processing logic compares the
received pilot symbols with the pilot symbols that are expected in certain sub-
carriers at certain times to determine a channel response for the sub-carriers
in which pilot symbols were transmitted. The results are interpolated to
estimate a channel response for most, if not all, of the remaining sub-
carriers
for which pilot symbols were not provided. The actual and interpolated
channel responses are used to estimate an overall channel response, which
includes the channel responses for most, if not all, of the sub-carriers in
the
OFDM channel.
The frequency domain symbols and channel reconstruction information,
which are derived from the channel responses for each receive path are
provided to an STC decoder 100, which provides STC decoding on both
received paths to recover the transmitted symbols. The channel
reconstruction information provides equalization information to the STC
decoder 100 sufficient to remove the effects of the transmission channel
when processing the respective frequency domain symbols.
The recovered symbols are placed back in order using symbol de-interleaver
logic 102, which corresponds to the symbol interleaver logic 58 of the
transmitter. The de-interleaved symbols are then demodulated or de-
mapped to a corresponding bitstream using de-mapping logic 104. The bits
are then de-interleaved using bit de-interleaver logic 106, which corresponds
to the bit interleaver logic 54 of the transmitter architecture. The de-
interleaved bits are then processed by rate de-matching logic 108 and
presented to channel decoder logic 110 to recover the initially scrambled data
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and the CRC checksum. Accordingly, CRC logic 112 removes the CRC
checksum, checks the scrambled data in traditional fashion, and provides it to
the de-scrambling logic 114 for descrambling using the known base station
de-scrambling code to recover the originally transmitted data 116.
In parallel to recovering the data 116, a CQI, or at least information
sufficient
to create a CQI at the BS 14, is determined and transmitted to the BS 14. As
noted above, the CQI may be a function of the carrier-to-interference ratio
(CR), as well as the degree to which the channel response varies across the
various sub-carriers in the OFDM frequency band. For this embodiment, the
channel gain for each sub-carrier in the OFDM frequency band being used to
transmit information is compared relative to one another to determine the
degree to which the channel gain varies across the OFDM frequency band.
Although numerous techniques are available to measure the degree of
variation, one technique is to calculate the standard deviation of the channel
gain for each sub-carrier throughout the OFDM frequency band being used to
transmit data.
In some embodiments, a relay station may operate in a time division manner
using only one radio, or alternatively include multiple radios.
Turning now to FIG. 7, there is shown an example network reference model,
which is a logical representation of a network that supports wireless
communications among the aforementioned BSs 14, MSs 16 and RSs 15, in
accordance with a non-limiting embodiment of the present invention. The
network reference model identifies functional entities and reference points
over which interoperability is achieved between these functional entities.
Specifically, the network reference model can include a MS 16, an Access
Service Network (ASN), and a Connectivity Service Network (CSN).
The ASN can be defined as a complete set of network functions needed to
provide radio access to a subscriber (e.g., an IEEE 802.16e or an IEEE
802.16m subscriber). The ASN can comprise network elements such as one
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or more BSs 14, and one or more ASN gateways. An ASN may be shared by
more than one CSN. The ASN can provide the following functions:
= Layer-1 and Layer-2 connectivity with the MS 16;
= Transfer of AAA messages to subscriber's Home Network Service
Provider (l-1-NSP) for authentication, authorization and session
accounting for subscriber sessions
= Network discovery and selection of the subscriber's preferred NSP;
= Relay functionality for establishing Layer-3 (L3) connectivity with the
MS 16 (e.g., IP address allocation);
= Radio resource management.
In addition to the above functions, for a portable and mobile environment, an
ASN can further support the following functions:
= ASN anchored mobility;
= CSN anchored mobility;
= Paging;
= ASN-CSN tunnelling.
For its part, the CSN can be defined as a set of network functions that
provide
IP connectivity services to the subscriber. A CSN may provide the following
functions:
= MS IP address and endpoint parameter allocation for user sessions;
= AAA proxy or server;
= Policy and Admission Control based on user subscription profiles;
= ASN-CSN tunnelling support;
= Subscriber billing and inter-operator settlement;
= lnter-CSN tunnelling for roaming;
= Inter-ASN mobility.
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The CSN can provide services such as location based services, connectivity
for peer-to-peer services, provisioning, authorization and/or connectivity to
IP
multimedia services. The CSN may further comprise network elements such
as routers, AAA proxy/servers, user databases, and interworking gateway
MSs. In the context of IEEE 802.16m, the CSN may be deployed as part of a
IEEE 802.16m NSP or as part of an incumbent IEEE 802.16e NSP.
In addition, RSs 15 may be deployed to provide improved coverage and/or
capacity. With reference to FIG 8, a BS 14 that is capable of supporting a
legacy RS communicates with the legacy RS in the "legacy zone". The BS 14
is not required to provide legacy protocol support in the "16m zone". The
relay protocol design could be based on the design of IEEE 802-16j, although
it may be different from IEEE 802-16j protocols used in the "legacy zone".
With reference now to FIG. 9, there is shown a system reference model,
which applies to both the MS 16 and the BS 14 and includes various
functional blocks including a Medium Access Control (MAC) common part
sublayer, a convergence sublayer, a security sublayer and a physical (PHY)
layer.
The convergence sublayer performs mapping of external network data
received through the CS SAP into MAC SDUs received by the MAC CPS
through the MAC SAP, classification of external network SDUs and
associating them to MAC SFID and CID, Payload header
suppression/compression (PHS).
The security sublayer performs authentication and secure key exchange and
Encryption.
The physical layer performs Physical layer protocol and functions.
The MAC common part sublayer is now described in greater detail. Firstly, it
will be appreciated that Medium Access Control (MAC) is connection-oriented.
That is to say, for the purposes of mapping to services on the MS 16 and
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associating varying levels of QoS, data communications are carried out in the
context of "connections". In particular, "service flows" may be provisioned
when the MS 16 is installed in the system. Shortly after registration of the
MS
16, connections are associated with these service flows (one connection per
service flow) to provide a reference against which to request bandwidth.
Additionally, new connections may be established when a customer's service
needs change. A connection defines both the mapping between peer
convergence processes that utilize the MAC and a service flow. The service
flow defines the QoS parameters for the MAC protocol data units (PDUs) that
are exchanged on the connection. Thus, service flows are integral to the
bandwidth allocation process. Specifically, the MS 16 requests uplink
bandwidth on a per connection basis (implicitly identifying the service flow).
Bandwidth can be granted by the BS to a MS as an aggregate of grants in
response to per connection requests from the MS.
With additional reference to FIG. 10, the MAC common part sublayer (CPS) is
classified into radio resource control and management (RRCM) functions and
medium access control (MAC) functions.
The RRCM functions include several functional blocks that are related with
radio resource functions such as:
= Radio Resource Management
= Mobility Management
= Network Entry Management
= Location Management
= Idle Mode Management
= Security Management
= System Configuration Management
= MBS (Multicast and Broadcasting Service)
= Service Flow and Connection Management
= Relay functions
= Self Organization
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= Multi-Carrier
Radio Resource Management
The Radio Resource Management block adjusts radio network
parameters based on traffic load, and also includes function of load
control (load balancing), admission control and interference control.
Mobility Management
The Mobility Management block supports functions related to Intra-RAT
/ Inter-RAT handover. The Mobility Management block handles the
Intra-RAT / Inter-RAT Network topology acquisition which includes the
advertisement and measurement, manages candidate neighbor target
BSs/RSs and also decides whether the MS performs Intra-RAT / Inter-
RAT handover operation.
Network Entry Management
The Network Entry Management block is in charge of initialization and
access procedures. The Network Entry Management block may
generate management messages which are needed during access
procedures, i.e., ranging, basic capability negotiation, registration, and
so on.
Location Management
The Location Management block is in charge of supporting location
based service (LBS). The Location Management block may generate
messages including the LBS information.
Idle Mode Management
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The Idle Mode Management block manages location update operation
during idle mode. The Idle Mode Management block controls idle mode
operation, and generates the paging advertisement message based on
paging message from paging controller in the core network side.
Security Management
The Security Management block is in charge of
authentication/authorization and key management for secure
communication.
System Configuration Management
The System Configuration Management block manages system
configuration parameters, and system parameters and system
configuration information for transmission to the MS.
MBS (Multicast and Broadcasting Service)
The MBS (Multicast Broadcast Service) block controls management
messages and data associated with broadcasting and/or multicasting
service.
Service Flow and Connection Management
The Service Flow and Connection Management block allocates "mobile
station identifiers" (or station identifiers ¨ STIDs) and "flow identifiers"
(FIDs) during access/handover/ service flow creation procedures. The
mobile station identifiers and FIDs will be discussed further below.
Relay functions
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The Relay Functions block includes functions to support multi-hop relay
mechanisms. The functions include procedures to maintain relay paths
between BS and an access RS.
Self Organization
The Self Organization block performs functions to support self
configuration and self optimization mechanisms. The functions include
procedures to request RSs/MSs to report measurements for self
configuration and self optimization and receive the measurements from
the RSs/MSs.
Multi-Carrier
The Multi-carrier (MC) block enables a common MAC entity to control a
PHY spanning over multiple frequency channels. The channels may be
of different bandwidths (e.g. 5, 10 and 20 MHz), be on contiguous or
non-contiguous frequency bands. The channels may be of the same or
different duplexing modes, e.g. Frequency Division Duplexing (FDD),
Time Division Duplexing (TDD), or a mix of bidirectional and broadcast
only carriers. For contiguous frequency channels, the overlapped
guard sub-carriers are aligned in frequency domain in order to be used
for data transmission.
The medium access control (MAC) includes function blocks which are related
to the physical layer and link controls such as:
= PHY Control
= Control Signaling
= Sleep Mode Management
= QoS
= Scheduling and Resource Multiplexing
= ARQ
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= Fragmentation/Packing
= MAC PDU formation
= Multi-Radio Coexistence
= Data forwarding
= Interference Management
= Inter-BS coordination
PHY Control
The PHY Control block handles PHY signaling such as ranging,
measurement/feedback (CQI), and HARQ ACK/NACK. Based on CQI
and HARQ ACK/NACK, the PHY Control block estimates channel
quality as seen by the MS, and performs link adaptation via adjusting
modulation and coding scheme (MCS), and/or power level. In the
ranging procedure, PHY control block does uplink synchronization with
power adjustment, frequency offset and timing offset estimation.
Control Signaling
The Control Signaling block generates resource allocation messages.
Sleep Mode Management block handles sleep mode operation.
Sleep Mode Management
The Sleep Mode Management block may also generate MAC signaling
related to sleep operation, and may communicate with Scheduling and
Resource Multiplexing block in order to operate properly according to
sleep period.
QoS
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The QoS block handles QoS management based on QoS parameters
input from the Service Flow and Connection Management block for
each connection.
Scheduling and Resource Multiplexing
The Scheduling and Resource Multiplexing block schedules and
multiplexes packets based on properties of connections. In order to
reflect properties of connections Scheduling and Resource Multiplexing
block receives QoS information from The QoS block for each
connection.
ARQ
The ARQ block handles MAC ARQ function. For ARQ-enabled
connections, ARQ block logically splits MAC SDU to ARQ blocks, and
numbers each logical ARQ block. ARQ block may also generate ARQ
management messages such as feedback message (ACK/NACK
information).
Fragmentation/Packing
The Fragmentation/Packing block performs fragmenting or packing
MSDUs based on scheduling results from Scheduling and Resource
Multiplexing block.
MAC PDU formation
The MAC PDU formation block constructs MAC PDU so that BS/MS
can transmit user traffic or management messages into PHY channel.
MAC PDU formation block adds MAC header and may add sub-
headers.
Multi-Radio Coexistence
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The Multi-Radio Coexistence block performs functions to support
concurrent operations of IEEE 802.16m and non-IEEE 802.16m radios
collocated on the same mobile station.
Data forwarding
The Data Forwarding block performs forwarding functions when RSs
are present on the path between BS and MS. The Data Forwarding
block may cooperate with other blocks such as Scheduling and
Resource Multiplexing block and MAC PDU formation block.
Interference Management
The Interference Management block performs functions to manage the
inter-cell/sector interference. The operations may include:
= MAC layer operation
= Interference measurement/assessment report sent via MAC
signaling
= Interference mitigation by scheduling and flexible frequency reuse
= PHY layer operation
= Transmit power control
= Interference randomization
= Interference cancellation
= Interference measurement
= Tx beamforming/precoding
Inter-BS coordination
The Inter-BS coordination block performs functions to coordinate the
actions of multiple BSs by exchanging information, e.g., interference
management. The functions include procedures to exchange
information for e.g., interference management between the BSs by
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backbone signaling and by MS MAC messaging. The information may
include interference characteristics, e.g. interference measurement
results, etc.
Reference is now made to FIG 11, which shows the user traffic data flow and
processing at the BS 14 and the MS 16. The dashed arrows show the user
traffic data flow from the network layer to the physical layer and vice versa.
On the transmit side, a network layer packet is processed by the convergence
sublayer, the ARQ function (if present), the fragmentation/packing function
and the MAC PDU formation function, to form MAC PDU(s) to be sent to the
physical layer. On the receive side, a physical layer SDU is processed by
MAC PDU formation function, the fragmentation/packing function, the ARQ
function (if present) and the convergence sublayer function, to form the
network layer packets. The solid arrows show the control primitives among
the CPS functions and between the CPS and PHY that are related to the
processing of user traffic data.
Reference is now made to FIG 12, which shows the CPS control plane
signaling flow and processing at the BS 16 and the MS 14. On the transmit
side, the dashed arrows show the flow of control plane signaling from the
control plane functions to the data plane functions and the processing of the
control plane signaling by the data plane functions to form the corresponding
MAC signaling (e.g. MAC management messages, MAC header/sub-header)
to be transmitted over the air. On the receive side, the dashed arrows show
the processing of the received over-the-air MAC signaling by the data plane
functions and the reception of the corresponding control plane signaling by
the control plane functions. The solid arrows show the control primitives
among the CPS functions and between the CPS and PHY that are related to
the processing of control plane signaling. The solid arrows between
M _ SAP/C_ SAP and MAC functional blocks show the control and
management primitives to/from Network Control and Management System
(NCMS). The primitives to/from M_SAP/C_SAP define the network involved
functionalities such as inter-BS interference management, inter/intra RAT
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mobility management, etc, and management related functionalities such as
location management, system configuration etc.
Non-limiting examples of MAC management messages include DL-MAP, UL-
MAP, DCD and UCD. Although nomenclature from IEEE 802.16 and/or
802.16m has been adopted, it should be appreciated that strict compliance
with either standard is not a requirement, and that those skilled in the art
will
recognize the use of common nomenclature as being an aid in understanding
rather than a limitation of the present invention.
The DL-MAP and UL-MAP can be used to define access to the downlink and
uplink information respectively. The DL-MAP is a MAC management
message that defines burst start times on the downlink. Equivalently, the UL-
MAP is a set of information that defines the entire (uplink) access for all
MSs
during a scheduling interval. Basically, the DL-MAP and UL-MAP can be
viewed as directories, broadcasted by the BS, of downlink and uplink frames.
The DCD (Downlink Channel Descriptor) message is a broadcasted MAC
management message transmitted by the BS 14 at a periodic time interval in
order to provide the burst profiles (physical parameter sets) that can be used
by a downlink physical channel during a burst, in addition to other useful
downlink parameters. The UCD (Uplink Channel Descriptor) message is a
broadcasted MAC management message transmitted by the BS at a periodic
time interval in order to provide the burst profile (physical parameter sets)
description that can be used by an uplink physical channel in addition to
other
useful uplink parameters.
Reference is now made to Fig 13, which shows a generic protocol
architecture to support a multicarrier system. A common MAC entity may
control a PHY spanning over multiple frequency channels. Some MAC
messages sent on one carrier may also apply to other carriers. The channels
may be of different bandwidths (e.g. 5, 10 and 20 MHz), be on contiguous or
non-contiguous frequency bands. The channels may be of different duplexing
modes, e.g. FDD, TDD, or a mix of bidirectional and broadcast only carriers.
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The common MAC entity may support simultaneous presence of MSs 16 with
different capabilities, such as operation over one channel at a time only or
aggregation across contiguous or non-contiguous channels.
Figure 20 illustrates a possible state transition diagram for a MS 16. By way
of non-limiting example, the diagram shows four (4) states, Initialization
state,
Access state, Connected state and Idle state.
Initialization State
In the Initialization state (see FIG. 21), the MS 16 performs cell
selection by scanning, synchronizing and acquiring the system
configuration information before entering Access state. If the MS 16
cannot properly perform the system configuration information decoding
and cell selection, it returns to perform scanning and downlink
synchronization. If the MS 16 successfully decodes the information
and selects a target BS 14, it transitions to the Access state.
Access State
In the Access state (see FIG. 22), the MS 16 performs network entry
with the target BS 14. Network entry is a multi step process consisting
of ranging, pre-authentication capability negotiation, authentication and
authorization, capability exchange and registration.
The breakdown of the system entry procedure leading from downlink
scanning and synchronization to the point where a connection is
established can be as follows, by way of non-limiting example:
= Downlink scanning and synchronization and acquisition of granting
message (which grants uplink resource) and acquisition of
description of downlink channel and uplink channel;
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= Initial ranging
= Capability negotiation
= Authorization and authentication/key exchange
= Registration with BS 14
= Connection establishment
Upon failure to complete network entry, the MS 16 may transition to the
Initialization state.
Connected State
When in the Connected state the MS 16 may operate in one of 3
modes (see FIG. 23): Sleep mode, Active mode and Scanning mode.
During the Connected state, the MS 16 can maintain one or more
fundamental connections established during Access state. Additionally
the MS 16 and BS 14 may establish additional transport connections.
The MS 16 may remain in the Connected state during a handover. The
MS 16 may transition from the Connected state to the Idle state on a
command from the BS 14. Failure to maintain the fundamental
connection(s) may also prompt the MS 16 to transition to the
Initialization state.
Referring now to the modes of operation in the Connected state, when
the MS 16 is in Active mode, the BS 14 may schedule the MS 16 to
transmit and receive at the earliest available opportunity provided by
the protocol being implemented, i.e. the MS is assumed to be
'available' to the BS 14. The MS 16 may request a transition to either
Sleep or Scanning mode from Active mode. Transition to Sleep or
Scanning mode can happen on command from the BS 14. The MS 16
may transition to Idle state from Active mode of the Connected state.
When in Sleep mode, the MS 16 and BS 14 agree on a division of the
resources in time into Sleep Windows and Listening Windows. The MS
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16 is only expected to be capable of receiving transmissions from the
BS 14 during the Listening Windows and any protocol exchange has to
be initiated during that time. The MS 16 transition to Active mode is
prompted by control messages received from the BS 14. The MS 16
may transition to Idle state from Sleep mode of the Connected state
during Listening Intervals.
When in Scanning mode, the MS 16 performs measurements as
instructed by the BS 14. The MS 16 is unavailable to the BS 14 while
in scanning mode. The MS 16 returns to Active mode once the
duration negotiated with the BS 14 for scanning expires.
Idle State
The Idle state (see FIG. 24) may, by way of non-limiting example,
include 2 separate modes, namely Paging Available mode and Paging
Unavailable mode, based on its operation and MAC message
generation. During the Idle state, the MS 16 may perform power
saving by switching between Paging Available mode and Paging
Unavailable mode.
Idle Mode, the MS 16 may belong to one or multiple paging groups.
When in Idle mode, the MS 16 may be assigned paging groups of
different sizes and shapes based on user mobility. The MS 16
monitors the paging message at during the MS's Paging Listening
Interval. The start of the MS's Paging Listening Interval is derived
based on paging cycle and paging offset. Paging offset and paging
cycle can be defined in terms of number of superframes.
The MS 16 may thus be paged by the BS 14 (using a specialized
paging message) while it is in the Paging Available mode. If the MS 16
is paged with indication to return to the Connected state, the MS 16
transitions to the Access state for its network re-entry.
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The MS 16 may also perform a location update procedure during Idle
State.
During Paging Unavailable mode, MS 16 does not need to monitor the
downlink channel in order to reduce its power consumption.
The MS has a global address (or global identifier) and logical addresses (or
logical identifiers) that identify the MS 16 during operation. Specifically,
the
global address can be a globally unique 48-bit IEEE Extended Unique
Identifier (EUI-48Tm) based on the 24-bit Organizationally Unique Identifier
(OUI) value administered by the IEEE Registration Authority. However, this is
not a limitation or restriction of the present invention.
As far as the logical identifiers are concerned, these can include one or more
"flow identifiers" (FIDs) and one or more "mobile station identifiers". The
FIDs
can uniquely identify management connections and transport connections that
the MS 16 has established with the network. Some specific FIDs may be pre-
assigned. For their part, the mobile station identifiers uniquely identify the
MS
16 within the domain of the BS 14. Various types of STID could be as follows:
Access ID: a temporary identifier assigned to the MS 16 when
performing a ranging operation (i.e., upon network entry while in the
Access state or upon network re-entry or during a location update while
in the Idle state). This ID can be assigned to the MS 16 by the BS 14
when the BS 14 first detects a ranging code transmission from the MS
16.
MS ID: an identifier assigned to the MS 16 for use in the Connected
state. The MS ID replaces the Access ID and can be sent to the MS
16 during the ranging operation. Downlink control
information
dedicated to a particular MS (e.g. downlink PHY burst/resource
allocation) can be addressed using the MS ID. The MS ID may, but
need not be, be the same length as the Access ID identifier.
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Idle ID: an identifier assigned to an MS for use in the Idle state. In
order to reduce signaling overhead and provide location privacy, the
Idle ID can be assigned to uniquely identify those MSs in the Idle state
that are in a particular paging group. The Idle ID remains valid for the
MS 16 as long as the MS 16 stays in the same paging group. The Idle
ID may be assigned during Idle state entry or during location update
due to a paging group change. The Idle ID can be included in a
message sent by the MS 16 in the Idle state for the purposes of page
response or location update.
By way of example, the mobile station identifiers mentioned above could be 8
bits, 10 bits or 12 bits in length, although longer or shorter STIDs are
possible
without departing from the present invention.
Different mobile station
identifiers can be of different lengths. For example, the Access ID could be
the same length and the MS ID, both of which could be shorter than the Idle
ID. However, this is only an example and is not to be considered limiting.
Other mobile station identifiers may exist and could be reserved, for example,
for broadcast or multicast services.
As will be appreciated by those of skill in the art, a MAC PDU is a package of
data (group of data bits, or datagram) that contain header, connection
address and data protocol information that is used to control and transfer
information across a type of medium (such as a radio channel). With
reference now to FIG. 15, the MAC PDU created in association with a given
connection contains a header, which holds the corresponding FID along with
control information (e.g., a length field, which indicates the length of the
payload of the MAC PDU and an Extended Header (EH) bit which, if set,
indicates that additional information appears in an extended portion (not
shown) of the header). The MAC PDU may also have payload of data and
error checking bits (CRC) bits after the header (e.g. user data). The payload
may be used to carry management messages and data associated with
various traffic connections.
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Being local to the MS, each FID is shorter than the 16-bit CID defined in IEEE
Standard 802.16-2004 or IEEE Standard 802.16-2009. In one non-limiting
embodiment, the FID can be of length 4 bits. In another non-limiting
embodiment, the FID can be of length 3 bits. Other possibilities exist within
the scope of the present invention. The use of the FID in the MAC header
also results in a shorter overall MAC header than the ones proposed in IEEE
802.16-2004 or IEEE 802.16-2009, where the 16-bit CID is used.
The following now describes a ranging operation that can be performed by the
MS 16 and the BS 14 in order to establish connectivity. The ranging
operation is performed by the appropriate functional blocks described above
and, in particular, the functional blocks belonging to the Medium Access
Control (MAC) Common Part Sublayer (CPS). These functional blocks may
include, for example and without limitation, the Network Entry Management
block and the Idle Mode Management block (part of the radio resource control
and management ¨ RRCM ¨ functions), as well as the PHY Control block
(part of the medium access control ¨ MAC ¨ functions) described earlier in
connection with FIG. 10.
Three non-limiting scenarios of the ranging operation will be described,
namely Scenario A in which the MS 16 is seeking to establish initial
connectivity to the network (i.e., the MS 16 is powered up, goes through the
Initialization state and performs ranging from the Access state), Scenario B
in
which the MS 16 performs ranging upon re-entering the network (e.g., after
having been in the Idle state, after having left the network to use a
different
one, then returned (i.e., roaming), etc.), and Scenario C in which the MS 16,
after having been in the Idle state, performs ranging in the context of a
location update.
Scenario A
In Scenario A, the MS 16 is seeking to establish initial connectivity to the
network. Firstly, the MS 16 is powered up and goes through the Initialization
state. During the Initialization state, the MS 16 performs scanning and
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synchronization. In other words, when the MS 16 wants to join the network, it
first scans the downlink frequencies to search for a suitable channel. The
search is complete as soon as it detects a downlink frame. The next step is to
establish synchronization with the BS 14. Once the MS 16 receives a DL-
MAP message and a DCD message, the downlink synchronization phase is
complete and the MS 16 remains synchronized as long as it keeps receiving
DL-MAP and DCD messages. After the synchronization is established, the
MS 16 waits for a UCD message to acquire uplink channel parameters.
A ranging operation now takes place while the MS 16 is in the Access state.
With reference to FIG. 14, the BS 14 issues an uplink granting message 1410
(e.g., a UL-MAP message) which defines an initial ranging interval to be used
by the MS 16 in the uplink frame. The contents of the uplink granting
message could be formulated by an uplink scheduler in the BS 14. The uplink
scheduler manages uplink bandwidth, and schedules MSs that will be
allocated uplink grants based on the QoS requirements of their service flow(s)
and bandwidth requests. An uplink grant allocated by the uplink scheduler is
directed towards a reserved FID (e.g., broadcast) and can use a predefined
robust profile with BPSK 1/2 modulation/FEC, for example. After transmission
of granting message 1410, the BS 14 continues to operate normally (1412).
This includes the periodic issuance of other granting messages, such as
granting message 1422.
Meanwhile, as shown at 1412, the MS 16 has been waiting for receipt of a
granting message and is assumed to ultimately receive granting message
1410. Upon receipt of the granting message 1410, the MS 16 formulates a
ranging message 1416 characterized by a set of ranging resources. For
example, the MS 16 can select, at random, a code from a set of pseudonoise
ranging codes, modulate it onto a ranging subchannel, and subsequently
transmit it in a randomly selected ranging slot from among a set of available
ranging slots on the uplink frame. The MS 16 can use random selection or
random backoff to select a ranging slot. When random selection is used, the
MS 16 can select one ranging slot from all available slots in a single frame
using a uniform random process, although other possibilities exist. When
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random backoff is used, the MS 16 can select one ranging slot from all
available ranging slots in a corresponding backoff window using a uniform
random process, for example.
If the BS 14 properly detects the presence of the ranging code in the ranging
slot of ranging message 1416, then the BS 14 issues a ranging response
message to the MS 16. For example, the ranging response message could
take a form similar to an RNG-RSP message as defined in IEEE 802.16 or
802.16m. In anticipation of this event, at step 1426, the MS 16 determines
whether an RNG-RSP message has been received from the BS 14. If a
certain amount of time has elapsed, and a RNG-RSP message has not been
received, then this means that the BS 14 has not properly detected the
presence of the ranging code in the ranging slot of ranging message 1416.
This could be for a variety of reasons, including power issues, interference,
etc. Meanwhile, the MS 16 is also attentive to receipt of further granting
messages (step 1420). If indeed the aforementioned granting message 1422
is received without having receiving an intervening RNG-RSP message from
the BS 14, then the MS 16 will be granted a new ranging interval in an uplink
frame.
In response, and similar to what was described earlier, the MS 16 formulates
a ranging message 1424 that is characterized by a set of ranging resources.
Specifically, the MS 16 selects, at random, a code from a set of pseudonoise
ranging codes, modulates it onto a ranging subchannel, and subsequently
transmits it in a randomly selected ranging slot from among a set of available
ranging slots on the uplink frame, and returns to step 1426. If the BS 14
properly detects the presence of the ranging code in the ranging slot of
ranging message 1424, then the BS 14 will issue a ranging response
message to the MS 16. In anticipation of this event, at step 1426, the MS 16
determines whether a ranging response message has been received from the
BS 14. If a certain amount of time has elapsed, and a ranging response
message still has not been received, then the MS 16 will receive yet another
granting message at step 1420 and so on. However, if the BS 14 does
properly detect the presence of the ranging code in the ranging slot of
ranging
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message 1424 (step 1428), then the BS 14 will determine whether the ranging
operation is successful (step 1430). In other words, just because the BS 14
can hear the MS 16 does not mean that the MS 16 is using adequate power,
timing and frequency parameters.
Thus, the outcome of step 1430 may be that the BS 14 has determined that
the ranging operation was a success, in which case the BS 14 proceeds to
issue a ranging response message 1450 indicative of this determination. On
the other hand, the outcome of step 1430 may be that the BS 14 has
determined that the ranging operation was not a success. In this case, the BS
14 proceeds to step 1432 where a parameter adjustment is calculated. This
may affect one or more of the frequency, timing and power that characterize
the signaling used by the MS 16. Various algorithms can be used to
determine an adjustment of the power, timing and/or frequency characteristics
of the uplink signal. Also at step 1432, the BS 14 calculates a new ranging
code and/or a new ranging slot to be used by the MS 16. Also at step 1432,
the BS 14 determines an Access ID for the MS 16. The Access ID is as yet
unknown to the MS 16. The Access ID can be used by the BS 14 as an
address, encryption key or scrambling code for content destined for the MS
16 during the ranging operation.
The BS 14 then proceeds to formulate a ranging response message 1434,
which is sent to the MS 16. Ranging response message 1434 specifies that
ranging is to continue, and provides any necessary adjustments to the timing /
frequency / power characteristics of the uplink signal. In addition, ranging
response message 1434 specifies the ranging code and/or ranging slot that
were used by the MS 16 to transmit ranging message 1424. This allows the
MS 16 to recognize that ranging response message 1434 is actually destined
for it. In addition, ranging response message 1434 identifies the assigned
ranging code and/or assigned ranging slot to be used by the MS 16 next time.
In addition, ranging response message 1434 includes the Access ID
mentioned above.
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Ranging response message 1434 is then received at the MS 16. The MS 16
executes step 1426 and determines that ranging response message 1434 is
indeed a ranging response message destined for the MS. In particular, this
can be determined based on fact that the ranging code and/or ranging slot
that the MS 16 previously used are present in ranging response message
1434. Therefore, the MS 16 takes the "Y" branch out of step 1426. Also, the
MS 16 stores the received Access ID in a memory for future use. Also, the
MS 16 makes the requisite adjustments to the power / time / frequency
characteristics it uses in the uplink direction. The MS 16 then proceeds to
formulate another ranging message 1436 characterized by a set of ranging
resources (and also the adjusted time / frequency / power) characteristics.
This time, the MS 16 uses the assigned ranging code and the assigned
ranging slot received from the BS 14 in ranging response message 1434.
The BS 14 receives ranging message 1436 and determines whether the
ranging operation is successful (step 1438). The outcome of step 1438 may
be that the BS 14 has determined that the ranging operation was a success,
in which case the BS 14 proceeds to issue a ranging response message 1448
indicative of this determination. However, it is possible at this stage that
the
previous power / time / frequency adjustments were not sufficient. The
outcome of step 1438 may therefore be that the BS 14 has determined that
the ranging operation was not a success. In this case, the BS 14 proceeds to
step 1440 where a further parameter adjustment is calculated. This may
again affect one or more of the frequency, timing and power that characterize
the signaling used by the MS 16. Various algorithms can be used to
determine an adjustment of the power, timing and/or frequency characteristics
of the uplink signal. Also at step 1440, the BS 14 may, but need not,
calculate
a new ranging code and/or a new ranging slot to be used by the MS 16.
The BS 14 then proceeds to formulate a ranging response message 1442,
which is sent to the MS 16. Ranging response message 1442 specifies that
ranging is to continue, as well as provides any necessary further adjustments
to the timing / frequency / power characteristics of the uplink signal. In
addition, ranging response message 1442 specifies the Access ID that had
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previously been sent to the MS 16 in ranging response message 1434. The
Access ID allows the MS 16 to recognize that ranging response message
1442 is destined for it. It is therefore not necessary to transmit in ranging
response message 1442 the ranging code and/or ranging slot that were used
by the MS 16 to transmit ranging message 1436. In addition, ranging
response message 1442 identifies the assigned ranging code and/or assigned
ranging slot, if computed at step 1440, to be used by the MS 16 in the future.
At step 1444, the MS 16 makes the requisite adjustments to the power / time /
frequency characteristics it uses in the uplink direction. The MS 16 then
proceeds to formulate another ranging message 1446 characterized by a set
of ranging resources (and also the adjusted time / frequency / power)
characteristics. The MS 16 uses either the ranging code and the ranging slot
it had used in the past or it uses the assigned ranging code and/or the
assigned ranging slot specified by the MS 16 in ranging response message
1442. The BS 14 receives ranging message 1446 from the MS 16 and
determines whether the ranging operation is successful (step 1438). If the
outcome of step 1438 is that the BS 14 has determined that the ranging
operation was not a success, then the BS 14 returns to step 1440. However,
at some point, the ranging operation will be considered to have been
successful, and the BS 14 proceeds to issue a ranging response message
1448 indicative of this determination. Ranging response message 1448 also
includes the Access ID identifying the MS 16. However, a lengthy MAC
address is not required.
The BS 14 then issues a granting message 1452, which schedules the next
uplink transmission from the MS 16. In this case, the next uplink transmission
from the MS 16 is a ranging request message 1454 containing the global
address (e.g., the 48-bit MAC address) of the MS 16. For example, the
ranging request message 1454 could take a form similar to an RNG-REQ
message as defined in IEEE 802.16 or 802.16m. Receipt of the global
address by the BS 14 allows the BS 14 to determine the true identity of the
MS 16 with which the ranging operation has completed successfully. Thus, at
step 1456, the BS 14 determines the MS ID based on the global address.
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This can be done by looking up the MS ID in a table in a memory, based on
the global address. Alternatively, the MS ID can be assigned from a pool of
addresses or identifiers, and stored in association with the global address.
The BS 14 then sends a ranging response message 1458 to the MS 16,
containing the MS ID, as well as the Access ID identifying the MS. The MS
16 receives the ranging response message 1458, and determines that it is the
recipient of this message (based on the Access ID). The MS 16 proceeds to
extract the MS ID and store it in a memory. With the ranging operation now
complete, the MS 16 enters the Connected state. The MS 16 uses the MS ID
in future communication with the network during the Connected state. Future
communication can include transmission and/or reception of data in
association with management connections and traffic connections.
It should be appreciated that because the Access ID is designed for use
specifically during the ranging operation, and because only a limited number
of mobile stations will perform ranging at any given time, the Access ID can
be limited to a small number of bits and, in particular, fewer than 16 bits.
As
an example, the 8-10 bit range may be suitable as a length of the Access ID.
Also, the fact that the same Access ID could conceivably be recycled by
different mobile stations performing ranging at different non-overlapping
times, the Access ID does not have a one-to-one mapping to a given MS's
global address. This preserves anonymity and enhances security.
Also, because during the Connected state the MS 16 can be identified by the
MS ID rather than its global address, and because the MS ID is local to the
domain of the serving BS, a similarly small number of bits can be used and, in
particular, fewer than 16 bits. Again, the 8-10 bit range may be suitable, by
way of example. However, this does not imply that the Access ID and the MS
ID need to be of the same length.
It will also be appreciated that the comparatively short length of the Access
ID
and MS ID cause shortening of the granting message (e.g., UL-MAP), the
ranging response message (e.g., RNG-RSP) and the ranging request
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message (e.g., RNG-REQ). The DL-MAP, DCD and UCD messages would
similarly benefit from a reduced length.
A first alternative embodiment is now described with reference to the flow
diagram in FIG. 16. Specifically, consider that the outcome of step 1438 is
that the BS 14 has determined that the ranging operation was not a success.
In this case, the BS 14 proceeds to step 1640 where a further parameter
adjustment is calculated. This may again affect one or more of the frequency,
timing and power that characterize the signaling used by the MS 16. Various
algorithms can be used to determine an adjustment of the power, timing
and/or frequency characteristics of the uplink signal. Also at step 1640, the
BS 14 calculates a new ranging code and a new ranging slot to be used by
the MS 16. As ranging continues, the ranging resources assigned correspond
to ranging channels with progressively smaller timing offsets. For example,
initial ranging attempts may be sent in a ranging region that spans 6 symbols
which is intended to accommodate larger ranging timing offsets. As ranging
progresses, the BS 14 can assign ranging resources to the MS 16 that span
progressively shorter durations, such as 3 and then 2 symbols. The final
ranging resource assigned may only accommodate synchronization to within
an OFDM cyclic prefix length. (The final ranging resource assigned may also
be retained by the MS 16 for periodic ranging.)
The BS 14 then proceeds to formulate a ranging response message 1642,
which is sent to the MS 16. Ranging response message 1642 specifies that
ranging is to continue, as well as provides any necessary further adjustments
to the timing / frequency / power characteristics of the uplink signal. In
addition, ranging response message 1642 identifies the assigned ranging
code and the assigned ranging slot to be used by the MS 16 in the future.
Indeed, at step 1444, the MS 16 makes the requisite adjustments to the
power / time / frequency characteristics it uses in the uplink direction. The
MS
16 then proceeds to formulate another ranging message 1646 characterized
by a set of ranging resources (and also the adjusted time / frequency / power)
characteristics. The MS 16 uses the assigned ranging code and the assigned
ranging slot specified by the MS 16 in ranging response message 1642.
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A second alternative embodiment is now described with reference to the flow
diagram in FIG. 17. Specifically, in this alternative embodiment, once the
ranging code and ranging slot used in a ranging message are received
("heard") b the BS 14, the MS 16 continues to use the same ranging code and
ranging slot until the BS 14 generates a ranging response message indicative
of successful ranging.
Alternatively or in addition, the MS 16 and BS 14 use sequences (or
"scrambling codes") for scrambling communications between the two entities.
A first such sequence is an "initial ranging sequence" and a second such
sequence is a "continued ranging sequence". As shown in FIG. 17, the initial
ranging sequence is used by the MS 16 to scramble the ranging messages it
sends before it receives the first ranging response message from the BS 14.
Also as shown in FIG. 17, the initial ranging sequence is also used by the BS
14 to scramble messages sent to the MS 16 before the MS 16 has received
the Access ID. Also as shown in FIG. 17, the continued ranging sequence
(or, optionally, the initial ranging sequence) can be used by the MS 16 to
scramble the ranging messages it sends between receiving the first ranging
response message from the BS 14 and receipt of the MS ID. Thus, it is
assumed that the initial ranging sequence (and, if used, the continued ranging
sequence) are known to the BS 14 and the MS 16. Also as shown in FIG. 17,
after the MS 16 has received the Access ID, the BS 14 scrambles messages
destined for the MS 16 using the Access ID. Clearly, the appropriate
descrambling needs to be performed by the recipient and therefore prior
knowledge of the appropriate scrambling code is needed. For this reason, it
is only after the MS 16 has been informed of the Access ID that messages
destined for the MS 16 can be scrambled using the Access ID.
Scenario B
In Scenario B, the MS 16 becomes involved in a ranging operation upon re-
entering the network (e.g., after having been in the Idle state, after having
left
the network to use a different one, then returned (i.e., roaming), etc.).
Thus,
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in this scenario, synchronization is assumed to have been maintained.
Reference is now made to the flow diagram in FIG. 18, which shows the
actions of the BS 14 and MS 16 while the MS 16 is in the Access state. It
should be appreciated that ranging can occur autonomously (i.e., MS-
initiated) or in response to a paging message 1809 from the BS 14 while the
MS 16 is in the Paging Available mode of the Idle state. In the case of a
received paging message 1809, the paging message 1809 can specify the set
of dedicated ranging resources to be used by the MS 16, such as a dedicated
ranging code and a dedicated ranging slot.
The BS 14 issues an uplink granting message 1810 (e.g., a UL-MAP
message) which defines an initial ranging interval to be used by the MS 16 in
the uplink frame. The contents of the uplink granting message could be
formulated by an uplink scheduler in the BS 14. The uplink scheduler
manages uplink bandwidth, and schedules MSs that will be allocated uplink
grants based on the QoS requirements of their service flow(s) and bandwidth
requests. An uplink grant allocated by the uplink scheduler is directed
towards a reserved FID (e.g., broadcast) and can use a predefined robust
profile with BPSK 1/2 modulation/FEC, for example. After transmission of
granting message 1810, the BS 14 continues to operate normally (1812).
This includes the periodic issuance of other granting messages, such as
granting message 1822.
Meanwhile, as shown at 1812, the MS 16 has been waiting for receipt of a
granting message and is assumed to ultimately receive granting message
1810. Upon receipt of the granting message 1810, the MS 16 formulates a
ranging message 1816 characterized by the set of dedicated ranging
resources specified in the paging message 1809. This includes a dedicated
ranging code and/or a dedicated ranging slot.
If the BS 14 properly detects the presence of the dedicated ranging code in
the dedicated ranging slot of ranging message 1816, then the BS 14 issues a
ranging response message to the MS 16. For example, the ranging response
message could take a form similar to an RNG-RSP message as defined in
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IEEE 802.16 or 802.16m. In anticipation of this event, at step 1826, the MS
16 determines whether an RNG-RSP message has been received from the
BS 14. If a certain amount of time has elapsed, and a RNG-RSP message
has not been received, then this means that the BS 14 has not properly
detected the presence of the dedicated ranging code in the dedicated ranging
slot of ranging message 1816. This could be for a variety of reasons,
including power issues, interference, etc. Meanwhile, the MS 16 is also
attentive to receipt of further granting messages (step 1820). If indeed the
aforementioned granting message 1822 is received without having receiving
an intervening RNG-RSP message from the BS 14, then the MS 16 will be
granted a new ranging interval in an uplink frame.
In response, and similar to what was described earlier, the MS 16 formulates
a ranging message 1824 that is characterized by the same set of dedicated
ranging resources. If the BS 14 properly detects the presence of the
dedicated ranging code in the dedicated ranging slot of ranging message
1824, then the BS 14 will issue a ranging response message to the MS 16. In
anticipation of this event, at step 1826, the MS 16 determines whether a
ranging response message has been received from the BS 14. If a certain
amount of time has elapsed, and a ranging response message still has not
been received, then the MS 16 will receive yet another granting message at
step 1820 and so on. However, if the BS 14 does properly detect the
presence of the dedicated ranging code in the dedicated ranging slot of
ranging message 1824 (step 1828), then the BS 14 will determine whether the
ranging operation is successful (step 1830). In other words, just because the
BS 14 can hear the MS 16 does not mean that the MS 16 is using adequate
power, timing and frequency parameters.
Thus, the outcome of step 1830 may be that the BS 14 has determined that
the ranging operation was a success, in which case the BS 14 proceeds to
issue a ranging response message 1850 indicative of this determination. On
the other hand, the outcome of step 1830 may be that the BS 14 has
determined that the ranging operation was not a success. In this case, the BS
14 proceeds to step 1832 where a parameter adjustment is calculated. This
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may affect one or more of the frequency, timing and power that characterize
the signaling used by the MS 16. Various algorithms can be used to
determine an adjustment of the power, timing and/or frequency characteristics
of the uplink signal. Also at step 1832, the BS 14 optionally calculates a new
ranging code and/or a new ranging slot to be used by the MS 16. Also at step
1832, the MS 14 determines an Access ID for the MS 16. The Access ID is
as yet unknown to the MS 16. The Access ID can be used by the BS 14 as
an address, encryption key or scrambling code for content destined for the
MS 16 during the ranging operation.
The BS 14 then proceeds to formulate a ranging response message 1834,
which is sent to the MS 16. Ranging response message 1434 specifies that
ranging is to continue, and provides any necessary adjustments to the timing /
frequency / power characteristics of the uplink signal. In addition, ranging
response message 1834 specifies the ranging code and/or ranging slot that
were used by the MS 16 to transmit ranging message 1824. This allows the
MS 16 to recognize that ranging response message 1834 is actually destined
for it. In addition, ranging response message 1834 optionally identifies the
new ranging code and/or new ranging slot determined at step 1832. In
addition, ranging response message 1834 includes the Access ID mentioned
above.
Ranging response message 1834 is then received at the MS 16. The MS 16
executes step 1826 and determines that ranging response message 1834 is
indeed a ranging response message destined for the MS. In particular, this
can be determined based on fact that the ranging code and/or ranging slot
that the MS 16 previously used are present in ranging response message
1834. Therefore, the MS 16 takes the "Y" branch out of step 1826. Also, the
MS 16 stores the received Access ID in a memory for future use. Also, the
MS 16 makes the requisite adjustments to the power / time / frequency
characteristics it uses in the uplink direction. The MS 16 then proceeds to
formulate another ranging message 1836 characterized by a set of ranging
resources (and also the adjusted time / frequency / power) characteristics.
The MS 16 uses the either the dedicated ranging code and the dedicated
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ranging slot, or the new ranging code and the new ranging slot received from
the BS 14 in ranging response message 1834.
The BS 14 receives ranging message 1836 and determines whether the
ranging operation is successful (step 1838). The outcome of step 1838 may
be that the BS 14 has determined that the ranging operation was a success,
in which case the BS 14 proceeds to issue a ranging response message 1848
indicative of this determination. However, it is possible at this stage that
the
previous power / time / frequency adjustments were not sufficient. The
outcome of step 1838 may therefore be that the BS 14 has determined that
the ranging operation was not a success. In this case, the BS 14 proceeds to
step 1840 where a further parameter adjustment is calculated. This may
again affect one or more of the frequency, timing and power that characterize
the signaling used by the MS 16. Various algorithms can be used to
determine an adjustment of the power, timing and/or frequency characteristics
of the uplink signal. Also at step 1840, the BS 14 may, but need not,
calculate
another new ("newer") ranging code and/or another new ("newer") ranging slot
to be used by the MS 16.
The BS 14 then proceeds to formulate a ranging response message 1842,
which is sent to the MS 16. Ranging response message 1842 specifies that
ranging is to continue, as well as provides any necessary further adjustments
to the timing / frequency / power characteristics of the uplink signal. In
addition, ranging response message 1842 specifies the Access ID that had
previously been sent to the MS 16 in ranging response message 1834. The
Access ID allows the MS 16 to recognize that ranging response message
1842 is destined for it. It is therefore not necessary to transmit in ranging
response message 1842 the ranging code and/or ranging slot that were used
by the MS 16 to transmit ranging message 1836. In
addition, ranging
response message 1842 identifies the newer ranging code and/or the newer
ranging slot, if computed at step 1840, to be used by the MS 16 in the future.
At step 1844, the MS 16 makes the requisite adjustments to the power / time /
frequency characteristics it uses in the uplink direction. The MS 16 then
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proceeds to formulate another ranging message 1846 characterized by a set
of ranging resources (and also the adjusted time / frequency / power)
characteristics. The MS 16 uses either the dedicated ranging code and the
dedicated ranging slot, or the new ranging code and the new ranging code it
(may have) used last time, or the newer ranging code and the newer ranging
slot specified by the MS 16 in ranging response message 1842. The BS 14
receives ranging message 1846 from the MS 16 and determines whether the
ranging operation is successful (step 1838). If the outcome of step 1838 is
that the BS 14 has determined that the ranging operation was not a success,
then the BS 14 returns to step 1840. However, at some point, the ranging
operation will be considered to have been successful, and the BS 14
proceeds to issue a ranging response message 1848 indicative of this
determination. Ranging response message 1848 also includes the Access ID
identifying the MS 16. However, a lengthy MAC address is not required.
The BS 14 then issues a granting message 1852, which schedules the next
uplink transmission from the MS 16. In this case, the next uplink transmission
from the MS 16 is a ranging request message 1854 containing the Idle ID of
the MS 16. For example, the ranging request message 1854 could take a
form similar to an RNG-REQ message as defined in IEEE 802.16 or 802.16m.
Receipt of the Idle ID by the BS 14 allows the BS 14 to determine the true
identity of the MS 16 with which the ranging operation has completed
successfully. This is because the Idle ID is uniquely mapped to the MS 16.
At step 1856, the BS 14 determines the Access ID based on the Idle ID. This
can be done by looking up the MS ID in a table in a memory, based on the
Idle ID, which may or may not involve an intermediate step of determining the
global address. Alternatively, the MS ID can be assigned from a pool of
addresses or identifiers, and stored in association with the Idle ID.
The BS 14 then sends a ranging response message 1858 to the MS 16,
containing the MS ID, as well as the Access ID identifying the MS. The MS
16 receives the ranging response message 1858, and determines that it is the
recipient of this message (based on the Access ID). The MS 16 proceeds to
extract the MS ID and store it in a memory. With the ranging operation now
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complete, the MS 16 enters the Connected state. The MS 16 uses the MS ID
in future communication with the network during the Connected state. Future
communication can include transmission and/or reception of data in
association with management connections and traffic connections.
A first alternative embodiment can incorporate changes to FIG. 18 similar to
those that modified the flow diagram in FIG. 16.
A second alternative embodiment can incorporate changes to FIG. 18 similar
to those that modified the flow diagram in FIG. 17.
Scenario C
In Scenario C, the MS 16 becomes involved in a ranging operation in order to
carry out a location update while in the Idle state. The location update can
occur autonomously (i.e., MS-initiated) or in response to a paging message
from the BS 14 while the MS 16 is in the Paging Available mode of the Idle
state. Specifically, the MS in Idle mode can perform a location update
process operation if one of following location update trigger conditions is
met:
= Paging group location update: The MS 16 performs the Location
Update process when the MS 14 detects a change in paging group.
The MS 16 detects the change of paging group by monitoring the
Paging Group Ds, which are transmitted by the BS 14;
= Timer based location update: The MS 16 periodically performs
location update process prior to the expiration of idle mode timer;
= Power down location update: The MS 14 attempts to complete a
location update once as part of its orderly power down procedure;
= Multicast/broadcast (MBS) location update: When receiving MBS
data in the Idle state, during MBS zone transition, the MS 16 may
perform a MBS location update process to acquire the MBS zone
information for continuous reception of MBS data.
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Reference is now made to the flow diagram in FIG. 19, which shows the
actions of the BS 14 and MS 16 while the MS 16 performs a location update
while in the Idle state. Specifically, the description from reference numeral
1809 up until the point where the MS 16 issues ranging request message
1854 containing the Idle ID of the MS 16 is identical to that given above with
reference to Fig. 18. The ranging request message 1854 may be also
formulated to indicate that it is a location update and not occurring in the
context of network entry. At step 1956, the BS 14, which is in receipt of
ranging request message 1854, acknowledges the location update. This can
be done by issuing a ranging response message 1958 to the MS 16,
containing a location update acknowledgement, as well as the Access ID
identifying the MS. The MS 16 receives the ranging response message 1958,
and determines that it is the recipient of this message (based on the Access
ID). With the ranging operation now complete, the MS 16 goes back into the
Idle state until a further location update is required or until it is
commanded to
enter into the Connected state. The MS 16 uses the Idle ID in future
communication with the network during the Idle state.
A first alternative embodiment can incorporate changes to FIG. 19 similar to
those that modified the flow diagram in FIG. 16.
A second alternative embodiment can incorporate changes to FIG. 19 similar
to those that modified the flow diagram in FIG. 17.
It should be appreciated that many variants of the above embodiments are
possible. Specifically, messages may be scrambled, encoded or encrypted in
any desired fashion. In particular, the scrambling techniques described with
reference to FIG. 17 could be applied to any of the other message flow
diagrams, in order to enhance security, reduce peak power or for other
reasons.
In addition, although the above messages have been described in the context
of the IEEE 802.16 and IEEE 820.16m mobile communication standards, it
should be appreciated that the present invention can be more broadly applied
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to other communication systems, including those being implemented or
designed in accordance with other mobile communication standards, such as
the Long Term Evolution (LTE) standard being promulgated by the Third
Generation Partnership Project (3GPP).
In addition, although the above description has focused on initial ranging
using an Access ID and an MS ID, it should be appreciated that the MS 16
may effect periodic ranging using one or both of these identifiers.
In addition, although the above description has focused on a point-to-
multipoint (PMP) implementation using an orthogonal frequency division
multiple access (OFDMA) PHY layer, it should be appreciated that
embodiments of the present invention may apply to other implementations
and PHY layers, including a mesh implementation, as well as a single carrier
(SC) PHY, a single-carrier access (SCa) PHY and orthogonal frequency
division multiplexing (OFDM) PHY. For example, in the SC, SCa and OFDM
PHY layers, rather than sending a ranging code, the MS may send a RNG-
REQ message in an initial ranging interval. Also, the MAC protocol used may
support Time Division Duplexing (TDD) and/or frequency division duplexing
(FDD).
In addition, it should be appreciated that embodiments of the present
invention can be applied to relay stations (RSs). More specifically, a RS can
behave such as to allow the MS to interact as if it were interacting with a
BS,
while behaving such as to allow the BS to interact as if it were interacting
with
a MS. Meanwhile, the RS may implement one or more of the above
described features with respect to initial ranging.
The foregoing figures and description provide one specific example of a
communication system that could be used to implement embodiments of the
application. It is to be understood that embodiments of the application can be
implemented with communications systems having architectures that are
different than the specific example, but that operate in a manner consistent
with the implementation of the embodiments as described herein.
CA 02773961 2011-12-22
WO 2011/003195
PCT/CA2010/001066
19582R0W003W /85934-133
Those skilled in the art will appreciate that in some embodiments, the MS 16
and/or the BS 14 may comprise one or more computing apparatuses that
have access to a code memory (not shown) which stores computer-readable
program code (instructions) for operation of the one or more computing
apparatuses, thereby allowing one or more of the above described functions
to be carried out. The computer-readable program code could be stored on a
medium which is fixed, tangible and readable directly by the one or more
computing apparatuses, (e.g., removable diskette, CD-ROM, ROM, fixed disk,
USB drive), or the computer-readable program code could be stored remotely
but transmittable to the one or more computing apparatuses via a modem or
other interface device (e.g., a communications adapter) connected to a
network (including, without limitation, the Internet) over a transmission
medium, which may be either a non-wireless medium (e.g., optical or analog
communications lines) or a wireless medium (e.g., microwave, infrared or
other transmission schemes) or a combination thereof. In other
embodiments, the MS 16 and/or the BS 14 may comprise pre-programmed
hardware or firmware elements (e.g., application specific integrated circuits
(ASICs), electrically erasable programmable read-only memories
(EEPROMs), flash memory, etc.), or other related components that allow one
or more of the above described functions to be carried out.
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