Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: TRANSMISSION OF MULTICAST BROADCAST SERVICE (MBS)
TRAFFIC IN A WIRELESS ENVIRONMENT
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. provisional patent application No.
61/239,239 filed on September 2, 2009, which is hereby incorporated by
reference in its entirety.
to This application is a continuation-in-part of the non-provisional
application
(serial number tbd) resulting from conversion under 37 C.F.R. 1.53(c)(3) of
U.S. provisional patent application no. 61/239,239 filed on September 2,
2009, which claims the benefit of U.S. provisional patent application No.
61/094,562 filed on September 5, 2008.
FIELD OF THE INVENTION
This application relates to wireless communication techniques in general, and
more specifically to symbol transmission in a MIMO scheme using Alamouti
codes.
BACKGROUND
The demand for services in which data is delivered via a wireless connection
has grown in recent years and is expected to continue to grow. Included are
applications in which data is delivered via cellular mobile telephony or other
mobile telephony, personal communications systems (PCS) and digital or high
definition television (HDTV). Though the demand for these services is
growing, the channel bandwidth over which the data may be delivered is
limited. Therefore, it is desirable to deliver data at high speeds over this
limited bandwidth in an efficient, as well as cost effective, manner.
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A known approach for efficiently delivering high speed data over a channel is
by using Orthogonal Frequency Division Multiplexing (OFDM). The high-
speed data signals are divided into tens or hundreds of lower speed signals
that are transmitted in parallel over respective frequencies within a radio
frequency (RF) signal that are known as sub-carrier frequencies ("sub-
carriers"). The frequency spectra of the sub-carriers overlap so that the
spacing between them is minimized. The sub-carriers are also orthogonal to
each other so that they are statistically independent and do not create
io crosstalk or otherwise interfere with each other. As a result, the channel
bandwidth is used much more efficiently than in conventional single carrier
transmission schemes such as AM/FM (amplitude or frequency modulation).
Space time transmit diversity (STTD) can achieve symbol level diversity which
significantly improves link performance. STTD code is said to be 'perfect',
therefore, in the sense that it achieves full space time coding rate (Space
time
coding rate = 1, also called rate-1), and it is orthogonal. When the number of
transmit antennas is more than 2, however, rate-1 orthogonal codes do not
exist.
An approach to providing more efficient use of the channel bandwidth is to
transmit the data using a base station having multiple antennas and then
receive the transmitted data using a remote station having multiple receiving
antennas, referred to as Multiple Input-Multiple Output (MIMO). MIMO
technologies have been proposed for next generation wireless cellular
systems, such as the third generation partnership project (3GPP) standards.
Because multiple antennas are deployed in both transmitters and receivers,
higher capacity or transmission rates can be achieved.
When using the MIMO systems to transmit packets, if a received packet has
an error, the receiver may require re-transmission of the same packet.
Systems are known that provide for packet symbols to be mapped differently
than the original transmission.
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A particular challenge in modern wireless environments lies in efficiently and
reliably providing Multicast Broadcast Service (MBS). Previous solutions have
many drawbacks. For example, they fail to satisfactorily address zone
coverage or to provide a sufficiently robust solution.
Thus a need exists for an improved way to transmit MBS traffic.
SUMMARY
io In accordance with a first broad aspect is provided a method of performing
a
multicast broadcast service (MBS) transmission in a multiple-input-multiple-
output (MIMO) communication. The method comprises transmitting first data
over a first MIMO layer, the first data being lower quality data. The method
further comprises transmitting second data over a second MIMO layer, the
is second data being enhancement data for enhancing the lower quality data.
The MBS transmission is to be defined at a subscriber station by the result of
enhancing the lower quality data with the enhancement data if the first and
second data is successfully received, and the MBS transmission is to be
defined at the subscriber station by the lower quality data alone if the first
data
20 is successfully received and the second data is not.
In accordance with a second broad aspect is provided a method of performing
a multicast broadcast service (MBS) transmission in a multiple-input-multiple-
output (MIMO) communication. The method comprises transmitting first data
25 over a first MIMO layer, the first data being lower quality data. The
method
further comprises selecting whether or not to transmit second data over a
second MIMO layer, the second data being enhancement data for enhancing
the lower quality data. The MBS transmission is to be defined at a subscriber
station by the result of enhancing the lower quality data with the enhancement
3o data if the first and second data is successfully received, and the MBS
transmission is to be defined at the subscriber station by the lower quality
data alone if the first data is successfully received and the second data is
not.
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In accordance with a third broad aspect is provided a method for transmitting
multicast broadcast service (MBS) traffic in a multiple-input-multiple-output
(MIMO) communication. The method comprises selecting a transmission
format for transmitting MBS data from amongst a plurality of available
transmission formats each having a transmission mode. The method further
comprises transmitting the MBS traffic using the selected transmission format;
The plurality of available transmission format includes at least a one
transmission format comprising one of a single-layer mode, a spatial
multiplexing (SM) mode and a hierarchical mode and at least another
io transmission format comprising another one of a single-layer mode, a
spatial
multiplexing (SM) mode and a hierarchical mode.
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
is embodiments of a disclosure in conjunction with the accompanying drawing
figures and appendices.
BRIEF DESCRIPTION OF THE DRAWINGS
20 Embodiments of the present application will now be described, by way of
example only, with reference to the accompanying drawing figures, wherein:
FIG. 1 is a block diagram of a cellular communication system;
25 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
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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
io overall network architecture;
FIG. 9 is Figure 3 of IEEE 802.16m-08/003rl, a System Reference Model;
FIG. 10 is Figure 4 of IEEE 802.16m-08/003rl, The IEEE 802.16m Protocol
is Structure;
FIG. 11 is Figure 5 of IEEE 802.16m-08/003r1, The IEEE 802.16m MS/BS
Data Plane Processing Flow;
20 FIG. 12 is Figure 6 of IEEE 802.16m-08/003rl, 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 block diagram of a cellular communication system in which
supports MBS;
FIG. 15. is a block diagram of a DL subframe comprising an MBS zone; and
FIG. 16 is a block diagram of a DL subframe comprising an MBS zone on
which is superposed unicast data.
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Like reference numerals are used in different figures to denote similar
elements.
DETAILED DESCRIPTION
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 (BS) 14. In some configurations,
each cell is further divided into multiple sectors 13 or zones (not shown). In
io general, each BS 14 facilitates communications using OFDM with subscriber
stations (SS) 16 which can be any entity capable of communicating with the
base station, and may include mobile and/or wireless terminals or fixed
terminals, which are within the cell 12 associated with the corresponding BS
14. If SSs 16 moves in relation to the BSs 14, this movement results in
significant fluctuation in channel conditions. As illustrated, the BSs 14 and
SSs 16 may include multiple antennas to provide spatial diversity for
communications. In some configurations, relay stations 15 may assist in
communications between BSs 14 and wireless terminals 16. SS 16 can be
handed off 18 from any cell 12, sector 13, zone (not shown), BS 14 or relay
15 to an other cell 12, sector 13, zone (not shown), BS 14 or relay 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 base station controller 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 SSs 16
(illustrated in FIG. 3) and relay stations 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
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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
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
to the network interface 30 or transmitted to another SS 16 serviced by the BS
14, either directly or with the assistance of a relay 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 subscriber station (SS) 16 is
illustrated. SS 16 can be, for example a mobile station. Similarly to the BS
14,
the SS 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 relays 15. A low noise amplifier and
3o 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.
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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).
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
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
is and processing techniques available to those skilled in the art are used
for
signal transmission between the SS and the base station, either directly or
via
the relay station.
In OFDM modulation, the transmission band is divided into multiple,
20 orthogonal subcarriers. Each subcarrier is modulated according to the
digital
data to be transmitted. Because OFDM divides the transmission band into
multiple subcarriers, the bandwidth per carrier decreases and the modulation
time per carrier increases. Since the multiple subcarriers are transmitted in
parallel, the transmission rate for the digital data, or symbols (discussed
later),
25 on any given subcarrier 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
3o 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
subcarriers are generated for multiple bands within a transmission channel.
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The modulated signals are digital signals having a relatively low transmission
rate and capable of staying within their respective bands. The individual
subcarrier are not modulated directly by the digital signals. Instead, all
subcarrier are modulated at once by IFFT processing.
In operation, OFDM is preferably used for at least downlink transmission from
the BSs 14 to the SSs 16. Each BS 14 is equipped with "n" transmit antennas
28 (n >=1), and each SS 16 is equipped with "m" receive antennas 40
(m >=1). Notably, the respective antennas can be used for reception and
io transmission using appropriate duplexers or switches and are so labelled
only
for clarity.
When relay stations 15 are used, OFDM is preferably used for downlink
transmission from the BSs 14 to the relays 15 and from relay stations 15 to
the SSs 16.
With reference to FIG. 4, an example of a relay station 15 is illustrated.
Similarly to the BS 14, and the SS 16, the relay station 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 relay 14 to assist in communications between a base station
16 and SSs 16. The receive circuitry 138 receives radio frequency signals
bearing information from one or more BSs 14 and SSs 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 frequency signal, which is then
digitized
into one or more digital streams.
3o 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
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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
io 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 SS and the base station, either
directly or indirectly via a relay station, as described above.
With reference to FIG. 5, a logical OFDM transmission architecture will be
described. Initially, the base station controller 10 will send data to be
transmitted to various SSs 16 to the BS 14, either directly or with the
assistance of a relay station 15. The BS 14 may use the information on the
quality of channel associated with the SSs to schedule the data for
transmission as well as select appropriate coding and modulation for
transmitting the scheduled data. The quality of the channel is found using
control signals, as described in more details below. Generally speaking,
however, the quality of channel for each SS 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
may be 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 SS 16. Again, the channel coding for a particular SS 16 may
be based on the quality of channel. In some implementations, the channel
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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
modulation scheme chosen by mapping logic 56. The modulation scheme
may be, for example, Quadrature Amplitude Modulation (QAM), Quadrature
1o Phase Shift Key (QPSK) or Differential Phase Shift Keying (DPSK)
modulation. For transmission data, the degree of modulation may be chosen
based on the quality of channel for the particular SS. 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.
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 SS 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 SS 16.
3o 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
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processors may be used to provide such digital signal processing, alone or in
combination with other processing described herein. The IFFT processors 62
will preferably 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
io (analog) signals are then simultaneously modulated at the desired RF
frequency, amplified, and transmitted via the RF circuitry 68 and antennas 28.
Notably, pilot signals known by the intended SS 16 are scattered among the
sub-carriers. The SS 16 may use the pilot signals for channel estimation.
Reference is now made to FIG. 6 to illustrate reception of the transmitted
signals by a SS 16, either directly from BS 14 or with the assistance of relay
15. Upon arrival of the transmitted signals at each of the antennas 40 of the
SS 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 (A/D) 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
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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. Preferably, the synchronization logic 76 includes 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
io 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
frequency domain symbols, which are sent to processing logic 92. The
is 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
20 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
25 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
30 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
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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
io 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 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 signal comprising an indication
of
channel quality, or at least information sufficient to derive some knowledge
of
channel quality at the BS 14, is determined and transmitted to the BS 14.
transmission of the CQI signal will be described in more detail below. 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 example, the channel
gain for each sub-carrier in the OFDM frequency band being used to transmit
information may be 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.
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FIGs. I to 6 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.
Turning now to Fig. 7, there is shown an example network reference model,
which is a logical representation of a network that supports wireless
io communications among the aforementioned BSs 14, SSs 16 and relay sations
(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 an
SS 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/m subscriber).
The ASN can comprise network elements such as one 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 SS 16;
' Transfer of AAA messages to subscriber's Home Network Service
Provider (H-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
SS 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:
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D ASN anchored mobility;
^ CSN anchored mobility;
Paging;
71 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;
^ Inter-CSN tunnelling for roaming;
I Inter-ASN mobility.
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
3o 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 SS 16 and the BS 14 and includes various functional
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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).
io 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 SS 16 and
associating varying levels of QoS, data communications are carried out in the
context of "connections". In particular, "service flows" may be provisioned
when the SS 16 is installed in the system. Shortly after registration of the
SS
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 SS 16 requests uplink
bandwidth on a per connection basis (implicitly identifying the service flow).
3o Bandwidth can be granted by the BS to a MS as an aggregate of grants in
response to per connection requests from the MS.
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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
^ 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.
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Network Entry Management
The Network Entry Management block is in charge of initialization and access
procedures. The Network Entry Management block may generate
s management messages which are needed during access procedures, i.e.,
ranging, basic capability negotiation, registration, and so on.
Location Management
io 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
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)
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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 "MS
identifiers" (or station identifiers - STIDs) and "flow identifiers" (FIDs)
during
access/handover/ service flow creation procedures. The MS identifiers and
FIDs will be discussed further below.
Relay functions
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. FDD, 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.
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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
^ 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
Sleep Mode Management block handles sleep mode operation. The Sleep
Mode Management block may also generate MAC signaling related to sleep
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operation, and may communicate with Scheduling and Resource Multiplexing
block in order to operate properly according to sleep period.
QoS
The QoS block handles QoS management based on QoS parameters input
from the Service Flow and Connection Management block for each
connection.
io 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
is information from The QoS block for each connection.
ARQ
The ARQ block handles MAC ARQ function. For ARQ-enabled connections,
20 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.
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Multi-Radio Coexistence
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
io 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 backbone signaling and by MS
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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 SS 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
io 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
mobility management, etc, and management related functionalities such as
location management, system configuration etc.
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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.
io 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.
Embodiments of the present invention are described with reference to a
MIMO communication system. The MIMO communication system may
implement packet re-transmission schemes which may be for use in
accordance with the IEEE 802.16(e) and IEEE 802.11 (n) standards. The
packet re-transmission schemes described below may be applicable to other
wireless environments, such as, but not limited to, those operating in
accordance with the third generation partnership project (3GPP) and 3GPP2
standards.
In the following description, the term 'STC code mapping' is used to denote a
mapping of symbols to antennas. Each symbol in such a mapping may be
replaced by its conjugate (e.g. S1*), or a rotation (e.g. jS1, -S1 and jS1),
or a
combination of its conjugate and a rotation (e.g. jSl*). In some embodiments,
the mapping also includes a signal weighting for each antenna.
Multicasting technique (one-source-many-destination) is widely utilized for
multimedia content delivery over networks. Multicast services may be
extended using wireless transmission to subscriber stations. In multicast
services, a wireless system broadcasts data packets to the subscriber
stations and each subscriber station receives and processes the same stream
of packets.
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MBS may be offered in one direction only, and more particularly in the
downlink only. Subscriber stations either in awake/sleep mode or in idle mode
may be able to receive the subscribed multicast and broadcast service flows.
Figure 14 is a block diagram of an exemplary cellular communication system
1400 a plurality of comprising cells 1405, each cell being served by
corresponding BS's 1410. The BS's 1410 and the cells 1405 may be similar to
the BS's 14 and cells 12 described above with reference to Figurel. As in
io Figure 1, in this example, each cell is divided into multiple sectors 1415,
although in other embodiments, the cells may not be so divided. The BS's
1410 facilitate communications using OFDM with subscriber stations (SS)
1425 which may be similar to the SS's 16 described above, with reference to
Figure 1 but more generally may be any entity capable of communicating with
the base station. In this example, the SS's 1425 are subscribed to MBS or
more generally of receive MBS data from the BS's 1410.
The cellular communication system 1400 comprises an MBS area 1420 in
which MBS is provided in accordance with a certain MBS scheme. In the
present example, MBS transmissions are a single frequency network (SFN)
transmissions.
It is to be understood that the size (including number of cells 1405 and
sectors
1415 and the shape and relative size of cells 1405 and of sectors 1415) and
shape of the cellular communication system 1400, including the MBS area
1420 is purely exemplary and that in other examples, the cellular
communication system 1400 may be different. For example, the MBS area
1420 may span the entire cellular communication system 1400, may be as
small as only one or a few cells 1405. Furthermore, insofar as the herein
3o description of the MBS area 1420 and MBS schemes used therein can be
applied to a single sectors 1415, the MBS area 1420 may span only one or a
few sectors 1415.
MBS traffic is transmitted downlink from BS 1410 to SS 1425 in DL
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subframes. More specifically, the MBS traffic is transmitted in a dedicated
MBS zone. Figure 15 shows a DL subframe 1500 comprising an MBS zone
1505 and a unicast zone 1510. In the unicast zone 1510, non-MBS traffic is
conveyed in any suitable way. The unicast zone 1510 is so named for the
purposes of this example to distinguish it from the MBS zone 1505. However,
it is to be understood that the unicast zone 1510 may be any zone in which
non MBS data is being transmitted.
The MBS zone comprises MBS traffic, including MBS control information in an
io MBS control sub-zonel515 and MBS data in an MBS data sub-zone 1520, as
shown.
For simplicity, the DL subframe is shown in block form to illustrate the
overall
transmission resources occupied by the DL subframe. It is to be understood
that the transmission resources occupied by the DL subframe may be defined
in any suitable manner, depending on the encoding/modulating scheme used.
For example, in an OFDM scheme, the transmission resources assigned to a
DL subframe may be defined in terms of time (e.g. time intervals for sending
one symbol) and frequency (e.g. subcarriers).
In the present example, the DL subframe 1500 is defined in terms of OFDM
intervals and subcarriers. However, it is to be understood that the
transmission resources occupied by the DL subframe 1500 may be defined
with parameters other than by time and frequency. For example if dedicated
frequencies are to be assigned wholly to the downlink, then the DL subframe
1500 may be defined uniquely by frequency. In other examples, the DL
subframe 1500 may be defined in terms of time (e.g. OFDM intervals),
subcarriers, spreading sequences, or suitable combinations thereof. Indeed,
any suitable mode of separating transmissions may be used.
Likewise it is to be understood that the MBS zone 1505 and the unicast zone
1510 may be defined using any suitable parameter type. In the present
example the transmission resources occupied by the MBS zone 1505 and by
the unicast zone are defined, like the DL subframe 1500 as a whole, in terms
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of OFDM intervals and subcarriers. However, it should be understood that the
transmission resources occupied by these zones may be defined otherwise as
well. Furthermore, these zones need not be defined using the same
parameters as the DL subframe 1500. For example, they may be defined by
particular spreading sequences used for each zone.
In this example, the DL subframe 1500 comprises both an MBS zone 1505
and a unicast zone 1510. These are multiplexed using FDM. It should be
understood however, that the MBS zone 1505 could occupy an entire DL
io subframe.
In the present example, the MBS zone 1505 is a localized zone. That is, it is
contiguous in time and frequency. It is to be understood, however, that the
MBS zone 1505 may also be a distributed zone that is not contiguous in either
time, frequency, or both. A distributed MBS zone may provide more frequency
diversity to MBS traffic. In particular, a distributed MBS zone may provide
more frequency diversity when the number of sectors participating in SFN
transmission is small.
The configuration of the MBS zone and its location (e.g. the transmission
resources occupied thereby -in this case time and frequency) can be
provided to the SS's 1425 in any suitable way. In one example, the
configuration of the MBS zone 1505 may be signaled by the BS. For example,
the BS may signal the configuration and location of the MBS zone through
any suitable broadcast control, multicast control or unicast control
available, to
all SS's or just to those who subscribed to the MBS service. In an alternative
example, the MBS zone 1505 configurations are agreed to in advance and
are not specifically signaled.
3o The MBS control information contained in the MBS control sub-zone 1515
may contain information on the next occurrence of the MBS zone or data, or
on the periodicity of occurrence of the MBS zone or data.
For MBS traffic transmitted for a large network, multipath channel length may
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be long. To accommodate MBS traffic transmitted for a large network, a larger
cyclic prefix size may be defined. In order to enlarge the cyclic prefix size
in a
DL subframe that is configured to provide for a smaller cyclic prefix size,
one
OFDM symbol is removed from the DL subframe 1500 containing the MBS
zone 1505. The cyclic prefixes of the remaining OFMD symbols are then
increased to fill the original subframe duration. It is to be understood that
while
in this example only one OFDM symbol is removed from the subframe to
make space for larger cyclic prefixes, in other examples more symbols may
be so removed.
The channelization and pilot pattern for the MBS zone 1505 may be the same
across all sectors participating in the SFN transmission. In particular, the
pilot
used for MBS transmission may be a common pilot that is transmitted on the
same tones in every sector participating in the SFN transmissions. Any
suitable pilot pattern may be used for MBS tragic. The pilot pattern used for
MBS traffic may be the same as that of the unicast pilot pattern or different.
In
this particular example the MBS pilot pattern is similar to the pilot pattern
used
for unicast transmissions but with a higher pilot signal density.
As shown in Figure 15, the MBS control information is contained within the
MBS zone 1505. Although the MBS control information is shown here as
being in a contiguous MBS control subzone 1515 of the MBS zone 1505, it is
to be understood that the MBS control subzone 1515 may be non-contiguous
and distributed within the MBS zone 1505.
Figure 16 shows a DL subframe 1600 comprising an MBS zone 1605 and a
unicast zone 1610, similarly to the DL subframe 1500 of Figure 15. The MBS
zone 1605 also comprises an MBS control sub-zone 1615 and an MBS data
sub-zone 1620. In this example, unicast data is superposed onto MBS traffic
in the MBS zone 1605. In such a case, the unicast control information may be
contained within the MBS zone 1605. In particular, the unicast control may be
superposed onto the MBS control in the MBS control sub-zone 1615. Thus, as
shown, the MBS control sub-zone 1615 may comprise MBS SFN Control
1625 relating to SFN transmission and superposed unicast control information
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1630. The unicast control signaling and message format used in the unicast
zone may be used to signal the unicast traffic in the MBS zone 1605. It may
be used to specify configurations and/or location of the unicast traffic in
the
MBS zone 1605.
Returning to the example of Figure 15, in general, common MBS control
information may be sent by all sectors 1415 on the same transmission
resources within the MBS zone 1505 using SFN transmissions. If some
control information is specific to a particular sector 1415, this control
io information may be broadcast to the SS(s) 1425 in the sector 1415 using
transmission resources outside the MBS zone 1505.
The MBS traffic can be transmitted in three different manners. In a first
manner, MBS traffic is a single layer transmission. In this case, the same
is signal is emitted from each of the transmit antennae, e.g. with phase
and/or
gain weighting to maximize signal power at input. This may be referred to as
single layer mode.
In a second case, MBS traffic is transmitted over multiple MIMO layers using
20 spatial multiplexing (SM). This may be referred to as SM mode. In this
case,
the data may be transmitted using either single codeword (SCW) or multiple
codeword (MCW). Generally, however, each sector in the MBS area 1420 or
SFN network will transmit all the MIMO layers using the same transmission
format.
A third manner of transmitting MBS traffic is to use hierarchical layers. In
this
hierarchical mode, two or more layers may be transmitted. A first layer is a
base layer, which carries lower quality data. In this context, quality of data
may refer to a number of things. In one example, the quality data refers to
the
3o quality of the electronic product that it defines. For example, the base
layer
may carry data corresponding to a multimedia product, such as an audio,
video or audio-video product having a low quality. For instance, the lower
quality data may define a video having a lower bitrate or resolution.
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A second layer is an enhanced layer. This layer carries additional information
that is complementary to the lower quality data in the form of enhancement
data to enhance the quality of the data transmitted at the base layer. The
base layer and the enhanced may be for a same MBS transmission. Using the
above example, the additional information may carry, information for
increasing the bitrate or resolution of the video defined by the lower quality
data transmitted over the first layer.
It is to be appreciated that the enhancement data may comprise any data that
1o can enhance the lower quality data. For example, the enhancement data may
convey information for adding 3D to 2D movie data being conveyed over the
base layer or may comprise data for providing a higher bitrate to audio data
being transmitted over the base layer or for providing a higher resolution to
image data. The enhancement data may also improve the quality of the lower
quality data by providing other enhancements peripheral or supplemental to
the lower quality data. For example, the enhancement data may provide
closed captioning to video data transmitted over the base layer, or album art
and/or song information related to a music audio data transmitted over the
enhanced layer.
Furthermore the enhancement data may not be for enhancing the electronic
end-product, but rather for enhancing the lower quality data itself, such as
by
providing additional redundancy.
Beyond the second layer, additional enhancement layers may also be
provided to provide further enhancement data to further improve the quality of
data transmitted at the base layer. For example, the base layer may carry
lower quality data corresponding to a low resolution video data, the
enhancement layer may carry enhancement data for improving the quality of
the lower quality data, and more specifically for enhancing the resolution of
the corresponding video data. A third layer may be provided as a second
enhancement layer. This third layer may be further enhancement data for
further enhancing the lower quality data. This may be done by applying the
further enhancement data to the result of enhancing the lower quality data
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with the enhancement data. For example, the enhancement data may be for
enhancing the resolution of a video defined by the lower quality data and the
further enhancement data may be for further enhancing the resolution.
Alternatively, the further enhancement data may be applicable directly to the
lower quality data, or to both the lower quality data alone or the result of
enhancing it with the enhancement data. For instance, the third layer may
comprise, for example, closed captioning data, or additional audio data, such
as a different language audio track. In such a case, the third layer data can
be
applied to the lower quality data or to the result of enhancing the lower
quality
io data with the second layer data.
In hierarchical mode, whether or not enhancement data is transmitted, and
the transmission configurations and number of layers used may be preset, or
may be selectively chosen, or both. For example, each BS may decide how
many hierarchical layers to employ, and may additionally be subject to
restrictions. In a non-limiting example of a hierarchical mode, there are two
possible layers of transmission to use, a base layer as described above and a
single enhancement layer. The sectors in the center of the MBS area 1425,
such as sectors 14151, may transmit both the base layer and the enhanced
layer, while the sectors near or at the edge of the MBS area 1425, such as
sectors 14150 may be restricted to transmit only the base layer.
The transmission format used in a transmissions defines the mode (single
layer, SM or hierarchical) of transmission of data, as well as the
transmission
configurations, such as the Modulation Coding Scheme (MCS), which defines
the encoding type or rate used and the modulation scheme used. In
hierarchical mode, the MCS used for MBS transmission may be different for
the different layers. For example, the base layer may employ a more robust
MCS to ensure that at least the lower quality data transmitted over the base
layer is received by the SS's 1425.
An MCS table may list transmission formats and may comprise any amount
on information on the transmission formats listed. In the context of the
cellular
communications system 1400, the transmission format for the MBS traffic may
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be indicated by an index into an MBS MCS table. In particular, the MBS MCS
table may define, for every MCS index if the transmission is SM or
hierarchical. Furthermore, the MBS MCS table may define different
modulation levels and code rates to be used, including modulation and code
rates to use at various layers, in the case of hierarchical mode. Table 1,
below
is an exemplary MBS MCS table.
MCS Level l Level2 Mode (SM / Field
Level Modulation Code Rate Modulation Code Rate Hierarchical)
1 QPSK 1/3, 2 reps 000
2 QPSK 1/3 001
3 16 QAM 1 /3 010
4 64 QAM 1 /3 011
5 QPSK 1/3 QPSK 1/3 H 100
6 QPSK 1/3 16 QAM 1/3 H 101
7 QPSK 1/3 QPSK 1/3 SM 110
8 16 QAM 1 /3 16 QAM 1 /3 SM 111
Table 1 - Exemplary MBS MCS table
io Table 1 comprises eight different transmission formats. The MCS level
indicates a level of the modulation coding scheme and may be used as an
index for identifying a certain transmission format in the table. The Field
parameter may also serve to this purpose.The first four such formats define
different single-layer modes, each corresponding to a different modulation
level and/or code rate. The first format includes QPSK modulation and a code
rate of 1/3 with two repetitions. The other three formats include QPSK, 16
QAM and 64 QAM respectively, each with a code rate of 1/3. Since these
transmission formats are all single-layer there is no second level for which
the
table should describe a modulation or encoding scheme
The fifth and sixth transmission formats listed in Table 1 use hierarchical
mode. As described above, in this mode a base layer carries lower quality
data while an enhanced layer carries enhancement data. As shown, the two
layers may, but don't need to, have identical modulation scheme and code
rates. In particular in the fifth transmission format listed the base layer
and the
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enhanced layer both use QPSK modulation and a code rate of 1/3. In the sixth
transmission format listed the base layer uses QPSK modulation, while the
enhanced layer uses 16QAM (both with a code rate of 1/3).
The seventh and eighth transmission formats listed in Table 1 use SM mode.
These employ two layers, although the modulation scheme and code rate is
the same for both layers.
For hierarchical mode, the selection of the number of hierarchical layers to
io employ may be made by the BS 1410. The BS 1410 may select the number of
hierarchical layers to employ on any suitable basis. In a non-limiting
example,
the BS 1410 receives feedback from the SS 1425. Feedback is any
information indicative of a transmission condition. For example, the feedback
may be indicative of a channel condition or quality. Or the feedback may
simply be an indication of whether a previous transmission has succeeded or
failed. Feedback may also include information on an SS 1425's receiving
capabilities or location or any other information that may affect a
transmission.
In order to achieve a desired coverage for MBS traffic, the BS 1410 may
adapt the transmission format used for SFN transmission based on MBS
feedback received from SSs 1425 with which it is in communication.
In general the MBS feedback from the SS 1425 is a low rate feedback
indicative of the quality of service of the MBS data. Any suitable feedback
scheme may be used and the manner in which the BS 1410 selects a
transmission format depends upon the type of feedback received. In one
example, the feedback may be a requested transmission format for MBS
traffic. Alternatively, the feedback may be in the form of an Acknowledge/No-
acknowledge (ACK/NACK) indicator, whereby a NACK may indicate that the
MBS Packet Error Rate (PER) exceeds a certain threshold.
In response to such feedback, the BS 1410 may respond by using only a
subset of the hierarchical layers. In some instances, the transmission format
indicated in the MBS control information may not be consistent with the actual
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transmission format used by the BS 1410. For example the MBS control
information may indicate that hierarchical transmission is being employed but
the BS 1410 may only be employing the first layer. This may occur, for
example, if the BS 1410 has decided to reduce the number of hierarchical
layers being used to achieve a more reliable transmission of the lower quality
data. In such a case, although the SS's 1425 receiving the MBS
transmissions will not receive (all) the enhancement data, they will still
receive
the lower quality data over the base layer.
io It is to be understood that the MBS MCS table shown above as Table 1 is
presented for illustrative purposes only, and in no way is the example of
Table
1 intended to be limiting. In particular, it should be noted that an MBS MCS
table may comprise more or fewer fields/columns to carry any amount of
information regarding the transmission formats contained therein. An MBS
MCS table may also, of course, comprise fewer or more transmission formats,
depending on the number of such transmission formats available for MBS.
Table 2 shows a simpler example of an MBS MCS table:
MCS Level Modulation Code Rate Field
1 00
2 01
3 10
4 11
Table 2 - One Level MBS MCS Table
As shown, in Table 2, no two levels are provided for modulation and code
rate. This table may be used for instances where MBS is employ single-layer
mode only. Furthermore, in the absence of a mode parameter field to define
the mode used for each transmission format listed in the table, it may not be
possible to use Table 2 to define a mode (single layer / SM / hierarchical).
Nevertheless, should knowledge that MBS transmission are to take place
using the SM mode be obtained from a different source (e.g., if this is a
known
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preset condition for the MBS area), Table 2 may still be used to define the
transmission format, if the BS knows that all the layers in the MBS
transmission will use the same listed modulation scheme and code rate.
Likewise if it is known that the MBS transmission are to take place using a
hierarchical mode, Table 2 may also be useful, provided that all layers are to
employ the same modulation scheme and code rate, or more generally that
no information on additional layers is needed.
Table 3 shows an exemplary MBS MCS table for use with hierarchical mode
io only.
MCS Level Level l Level 2 Field
Modulation Code Rate Modulation Code Rate
1 QPSK 1/3, 2 reps QPSK 1/3, 2 reps 00
2 QPSK 1/3 QPSK 1/3 01
3 QPSK 1/3, 2 reps 16QAM 1/3, 2 reps 10
4 QPSK 1/3 16 QAM 1/3 11
Table 3 - Exemplary MBS MCS Table for Hierarchical
Table 3 is an example of a table that may be used for instance where MBS
traffic is transmitted using hierarchical mode only, and does not comprise a
mode field. Since every transmission mode listed is implicitly defined as
employing hierarchical mode, every transmission mode lists the modulation
and code rate used for multiple levels for corresponding layers. In this
example, two layers are used in every transmission format. It is to be
understood that more layers may be used as well. Furthermore, where
multiple layers are used, not all transmission formats need employ all layers.
Table 4 shows an exemplary MBS MCS table combining the single-layer
transmission formats shown in Table 2, above, and some of the hierarchical
transmission format from Table 3, above. This table thus defines transmission
formats defining different modes.
MCS Level Level l Level 2 Field
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Modulation Code Rate Modulation Code Rate
1 QPSK 1/3, 2 reps 000
2 QPSK 1/3 001
3 16QAM 1 /3 010
4 64QAM 1 /3 011
QPSK 1/3 QPSK 1/3 100
6 QPSK 1 /3 16 QAM 1 /3 101
7 Reserved 110
8 Reserved 111
Table 4 - Exemplary MBS MCS Table Combining Different Modes
A similar table could result if the transmission formats include single-layer
modes and SM modes. Table 5 shows an exemplary MBS MCS table listing
5 transmission formats that employ both single-layer and SM modes.
MCS Level l Level2 Mode (SM / Field
Level Modulation Code Rate Modulation Code Rate Hierarchical)
1 QPSK 1/3, 2 reps 000
2 QPSK 1/3 001
3 16 QAM 1 /3 010
4 64 QAM 1 /3 011
5 QPSK 1/3 QPSK 1/3 SM 100
6 16 QAM 1 /3 16 QAM 1 /3 SM 101
7 Reserved 110
8 Reserved 111
Table 5 - Exemplary MBS MCS Table Combining Different Modes
Finally, an MBS MCS table may list transmission formats using single layer,
io SM and hierarchical modes. Table 6 is an example of such an MBS MCS
table. As shown, Table 6 includes fields for the modulation and coding at two
levels, which fields may have different values if the mode indicated for that
particular transmission is the hierarchical mode.
MCS Level 1 Level2 Mode (SM / Field
Level Modulation Code Rate Modulation Code Rate Hierarchical)
1 QPSK 1/3, 2 reps QPSK 1/3, 2 reps H 000
2 QPSK 1/3 QPSK 1/3 H 001
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3 QPSK 1 /3 16 QAM 1 /3 H 010
4 16 QAM 1 /3 011
64 QAM 1 /3 100
6 QPSK 1 /3 QPSK 1 /3 SM 101
7 16 QAM 1 /3 16 QAM 1 /3 SM 110
8 Reserved 111
Table 6 - Exemplary MBS MCS table
If there are more than one MBS network or areas communicating different
MBS transmissions in the cellular communication system 1400, neighboring
5 MBS areas may use non-overlapping MBS zones for the transmission of their
respective MBS content. On the resources used by the neighboring MBS
network, lower power unicast data may be transmitted.
Furthermore, for the sectors 1415 at the edge of the MBS zone may use
1o additional resources to transmit the MBS traffic. Additional information
may be
transmitted for chase combining or incremental redundancy as done in HARQ
for unicast data. This information may be transmitted within a same sub-frame
as the original MBS transmission or in a later sub-frame. This may be done
across several sectors using SFN, or independently on a per-sector basis.
The above-described embodiments of the present application are intended to
be examples only. Those of skill in the art may effect alterations,
modifications
and variations to the particular embodiments without departing from the scope
of the application.
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