Methods and systems for utilizing a multicast/broadcast CID scheduling MAC management message

Methods and systems for utilizing a multicast/broadcast connection identifier (CID) scheduling message in an orthogonal frequency-division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) frame in an effort to bypass at least a portion of the Media Access Control (MAC) protocol data unit (PDU) parsing of the frame are provided. By bypassing at least a portion of the MAC PDU parsing of the OFDM/OFDMA frame (which may be in accordance with one or more standards of the IEEE 802.16 family of standards), a particular user terminal need not spend a lot of overhead in the CID filtering process, determining which MAC PDUs are intended to be processed by the MAC of that particular user terminal. Furthermore, for certain embodiments, a user terminal may power down related circuitry during the terminal's bypassing time period(s) of the OFDM/OFDMA frame in an effort to save power.

TECHNICAL FIELD

Certain embodiments of the present disclosure generally relate to wireless communication and, more particularly, to providing multicast/broadcast connection identifier (CID) scheduling information in an orthogonal frequency-division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) frame.

BACKGROUND

OFDM and OFDMA wireless communication systems under IEEE 802.16 use a network of base stations to communicate with wireless devices (i.e., mobile stations) registered for services in the systems based on the orthogonality of frequencies of multiple subcarriers and can be implemented to achieve a number of technical advantages for wideband wireless communications, such as resistance to multipath fading and interference. Each base station emits and receives radio frequency (RF) signals that convey data to and from the mobile stations. Such an RF signal from a base station includes an overhead load, in addition to the data load (voice and other data), for various communication management functions. Each mobile station processes the information in the overhead load of each received signal prior to processing the data.

The IEEE 802.16x standard was developed for the delivery of such wideband services as voice, data, and video. The Media Access Control (MAC) layer of the standard can support bursty data traffic with high peak rate demand while simultaneously supporting streaming video and latency-sensitive voice traffic over the same channel. Some of this traffic may include broadcast and/or multicast data intended for delivery to a plurality of mobile stations. The resources allocated to one mobile station or to a multicast/broadcast connection by the MAC scheduler can vary from a single time slot to the entire OFDM/OFDMA frame, thus providing a very large dynamic range of throughput to a specific mobile station or to a plurality of mobile stations, respectively, at any given time. Furthermore, since the resource allocation information is conveyed in the MAP messages at the beginning of each frame, the scheduler can effectively change the resource allocation on a frame-by-frame basis to adapt to the bursty nature of the traffic.

SUMMARY

Certain embodiments of the present disclosure generally relate to providing a multicast/broadcast connection identifier (CID) scheduling message in an orthogonal frequency-division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) frame in an effort to bypass at least a portion of the Media Access Control (MAC) protocol data unit (PDU) parsing of the frame. By bypassing at least a portion of the MAC PDU parsing of the OFDM/OFDMA frame, a particular user terminal need not spend a lot of overhead in the CID filtering process, determining which MAC PDUs are intended to be processed by the MAC of that particular user terminal. Furthermore for some embodiments, a user terminal may power down related circuitry during the terminal's bypassing time period(s) of the OFDM/OFDMA frame in an effort to save power.

Certain embodiments of the present disclosure provide a method for processing multicast or broadcast data transmitted in OFDM or OFDMA frames. The method generally includes decoding a downlink MAP (DL-MAP); extracting CID scheduling information contained in the DL-MAP, wherein the scheduling information identifies the location of data bursts associated with one or more multicast or broadcast CIDs within one or more OFDM or OFDMA frames; and bypassing at least a portion of the one or more frames based on the scheduling information when parsing the frames.

Certain embodiments of the present disclosure provide a receiver for processing multicast or broadcast data transmitted in OFDM or OFDMA frames. The receiver generally includes decoding logic configured to decode a DL-MAP; extracting logic configured to extract CID scheduling information contained in the DL-MAP, wherein the scheduling information identifies the location of data bursts associated with one or more multicast or broadcast CIDs within one or more OFDM or OFDMA frames; and bypassing logic configured to bypass at least a portion of the one or more frames based on the scheduling information when parsing the frames.

Certain embodiments of the present disclosure provide an apparatus for processing multicast or broadcast data transmitted in OFDM or OFDMA frames. The apparatus generally includes means for decoding a DL-MAP; means for extracting CID scheduling information contained in the DL-MAP, wherein the scheduling information identifies the location of data bursts associated with one or more multicast or broadcast CIDs within one or more OFDM or OFDMA frames; and means for bypassing at least a portion of the one or more frames based on the scheduling information when parsing the frames.

Certain embodiments of the present disclosure provide a mobile device capable of processing multicast or broadcast data. The mobile device generally includes a receiver front end for receiving signals based on multicast or broadcast data transmitted in OFDM or OFDMA frames; decoding logic configured to decode a DL-MAP; extracting logic configured to extract CID scheduling information contained in the DL-MAP, wherein the scheduling information identifies the location of data bursts associated with one or more multicast or broadcast CIDs within one or more OFDM or OFDMA frames; and bypassing logic configured to bypass at least a portion of the one or more frames based on the scheduling information when parsing the frames.

Certain embodiments of the present disclosure provide a computer-program product for processing multicast or broadcast data transmitted in OFDM or OFDMA frames comprising a computer readable medium having a set of instructions stored thereon, the set of instructions being executable by one or more processing devices and the set of instructions including: instructions for decoding a DL-MAP, instructions for extracting CID scheduling information contained in the DL-MAP, wherein the scheduling information identifies the location of data bursts associated with one or more multicast or broadcast CIDs within one or more OFDM or OFDMA frames, and instructions for bypassing at least a portion of the one or more frames based on the scheduling information when parsing the frames.

Certain embodiments of the present disclosure provide a method for transmitting multicast or broadcast data in OFDM or OFDMA frames. The method generally includes obtaining scheduling information identifying the location of data bursts, associated with one or more multicast or broadcast CIDs, to be transmitted in one or more OFDM or OFDMA frames; and transmitting the scheduling information in a portion of a DL-MAP of the one or more frames.

Certain embodiments of the present disclosure provide a transmitter for transmitting multicast or broadcast data in OFDM or OFDMA frames. The transmitter generally includes scheduling logic configured to obtain scheduling information identifying the location of data bursts, associated with one or more multicast or broadcast CIDs, to be transmitted in one or more OFDM or OFDMA frames; and transmission logic configured to transmit the scheduling information in a portion of a DL-MAP of the one or more frames.

Certain embodiments of the present disclosure provide an apparatus for transmitting multicast or broadcast data in OFDM or OFDMA frames. The apparatus generally includes means for obtaining scheduling information identifying the location of data bursts, associated with one or more multicast or broadcast CIDs, to be transmitted in one or more OFDM or OFDMA frames; and means for transmitting the scheduling information in a portion of a DL-MAP of the one or more frames.

Certain embodiments of the present disclosure provide a mobile device capable of transmitting multicast or broadcast data. The mobile device generally includes logic configured to obtain scheduling information identifying the location of data bursts, associated with one or more multicast or broadcast CIDs, to be transmitted in one or more OFDM or OFDMA frames; and a transmitter front end for transmitting the scheduling information in a portion of a DL-MAP of the one or more frames.

Certain embodiments of the present disclosure provide a computer-program product for transmitting multicast or broadcast data in OFDM or OFDMA frames comprising a computer readable medium having a set of instructions stored thereon, the set of instructions being executable by one or more processing devices and the set of instructions including: instructions for obtaining scheduling information identifying the location of data bursts, associated with one or more multicast or broadcast CIDs, to be transmitted in one or more OFDM or OFDMA frames, and instructions for transmitting the scheduling information in a portion of a DL-MAP of the one or more frames.

Certain embodiments, as summarized above, also comprise the OFDM or OFDMA frames including a format in accordance with one or more standards of the Institute of Electrical and Electronics Engineers (IEEE) 802.16 family of standards.

DETAILED DESCRIPTION

Certain embodiments of the present disclosure provide techniques and apparatus for providing information regarding multicast/broadcast connection identifier (CID) scheduling in an orthogonal frequency-division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) frame. The CID scheduling information may be included, for example, as a Media Access Control (MAC) management message contained in a DL-MAP. A user terminal may process this CID scheduling message to locate DL bursts of interest (e.g., for channels of a media broadcast associated with given CIDs).

As a result, rather than process the entire frame of data in order to locate DL bursts of interest and filtering out DL bursts that are not of interest, the user terminal (e.g., mobile station) may be able to bypass at least a portion of the Media Access Control (MAC) protocol data unit (PDU) parsing of the frame. By bypassing at least a portion of the MAC PDU parsing of the OFDM/OFDMA frame, a particular user terminal need not spend a lot of overhead in the CID filtering process, determining which MAC PDUs are intended to be processed by the MAC of that particular user terminal. Furthermore for some embodiments, a user terminal may power down related circuitry during the terminal's bypassing time period(s) of the OFDM/OFDMA frame in an effort to save power.

Exemplary Wireless Communication System

The methods and apparatus of the present disclosure may be utilized in a broadband wireless communication system. The term “broadband wireless” refers to technology that provides wireless, voice, video, Internet, and/or data network access over a given area.

WiMAX, which stands for the Worldwide Interoperability for Microwave Access, is a standards-based broadband wireless technology that provides high-throughput broadband connections over long distances. There are two main applications of WiMAX today: fixed WiMAX and mobile WiMAX. Fixed WiMAX applications are point-to-multipoint, enabling broadband access to homes and businesses, for example. Mobile WiMAX offers the full mobility of cellular networks at broadband speeds.

Mobile WiMAX is based on OFDM and OFDMA technology. OFDM is a digital multi-carrier modulation technique that has recently found wide adoption in a variety of high-data-rate communication systems. With OFDM, a transmit bit stream is divided into multiple lower-rate substreams. Each substream is modulated with one of multiple orthogonal subcarriers and sent over one of a plurality of parallel subchannels. OFDMA is a multiple access technique in which users are assigned subcarriers in different time slots. OFDMA is a flexible multiple-access technique that can accommodate many users with widely varying applications, data rates, and quality of service requirements.

The rapid growth in wireless internets and communications has led to an increasing demand for high data rate in the field of wireless communications services. OFDM/OFDMA systems are today regarded as one of the most promising research areas and as a key technology for the next generation of wireless communications. This is due to the fact that OFDM/OFDMA modulation schemes can provide many advantages such as modulation efficiency, spectrum efficiency, flexibility, and strong multipath immunity over conventional single carrier modulation schemes.

IEEE 802.16x is an emerging standard organization to define an air interface for fixed and mobile broadband wireless access (BWA) systems. These standards define at least four different physical layers (PHYs) and one Media Access Control (MAC) layer. The OFDM and OFDMA physical layer of the four physical layers are the most popular in the fixed and mobile BWA areas respectively.

FIG. 1illustrates an example of a wireless communication system100. The wireless communication system100may be a broadband wireless communication system. The wireless communication system100may provide communication for a number of cells102, each of which is serviced by a base station104. A base station104may be a fixed station that communicates with user terminals106. The base station104may alternatively be referred to as an access point, a Node B, or some other terminology.

FIG. 1depicts various user terminals106dispersed throughout the system100. The user terminals106may be fixed (i.e., stationary) or mobile. The user terminals106may alternatively be referred to as remote stations, access terminals, terminals, subscriber units, mobile stations, stations, user equipment, etc. The user terminals106may be wireless devices, such as cellular phones, personal digital assistants (PDAs), handheld devices, wireless modems, laptop computers, personal computers, etc.

A variety of algorithms and methods may be used for transmissions in the wireless communication system100between the base stations104and the user terminals106. For example, signals may be sent and received between the base stations104and the user terminals106in accordance with OFDM/OFDMA techniques. If this is the case, the wireless communication system100may be referred to as an OFDM/OFDMA system.

A communication link that facilitates transmission from a base station104to a user terminal106may be referred to as a downlink108, and a communication link that facilitates transmission from a user terminal106to a base station104may be referred to as an uplink110. Alternatively, a downlink108may be referred to as a forward link or a forward channel, and an uplink110may be referred to as a reverse link or a reverse channel.

A cell102may be divided into multiple sectors112. A sector112is a physical coverage area within a cell102. Base stations104within a wireless communication system100may utilize antennas that concentrate the flow of power within a particular sector112of the cell102. Such antennas may be referred to as directional antennas.

FIG. 2illustrates various components that may be utilized in a wireless device202. The wireless device202is an example of a device that may be configured to implement the various methods described herein. The wireless device202may be a base station104or a user terminal106.

The wireless device202may also include a housing208that may include a transmitter210and a receiver212to allow transmission and reception of data between the wireless device202and a remote location. The transmitter210and receiver212may be combined into a transceiver214. An antenna216may be attached to the housing208and electrically coupled to the transceiver214. The wireless device202may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers, and/or multiple antennas.

The wireless device202may also include a signal detector218that may be used in an effort to detect and quantify the level of signals received by the transceiver214. The signal detector218may detect such signals as total energy, pilot energy from pilot subcarriers or signal energy from the preamble symbol, power spectral density, and other signals. The wireless device202may also include a digital signal processor (DSP)220for use in processing signals.

The various components of the wireless device202may be coupled together by a bus system222, which may include a power bus, a control signal bus, and a status signal bus in addition to a data bus.

FIG. 3illustrates an example of a transmitter302that may be used within a wireless communication system100that utilizes OFDM/OFDMA. Portions of the transmitter302may be implemented in the transmitter210of a wireless device202. The transmitter302may be implemented in a base station104for transmitting data306to a user terminal106on a downlink108. The transmitter302may also be implemented in a user terminal106for transmitting data306to a base station104on an uplink110.

Data306to be transmitted is shown being provided as input to a serial-to-parallel (S/P) converter308. The S/P converter308may split the transmission data into N parallel data streams310.

The N parallel data streams310may then be provided as input to a mapper312. The mapper312may map the N parallel data streams310onto N constellation points. The mapping may be done using some modulation constellation, such as binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), 8 phase-shift keying (8PSK), quadrature amplitude modulation (QAM), etc. Thus, the mapper312may output N parallel symbol streams316, each symbol stream316corresponding to one of the N orthogonal subcarriers of the inverse fast Fourier transform (IFFT)320. These N parallel symbol streams316are represented in the frequency domain and may be converted into N parallel time domain sample streams318by an IFFT component320.

A brief note about terminology will now be provided. N parallel modulations in the frequency domain are equal to N modulation symbols in the frequency domain, which are equal to N mapping and N-point IFFT in the frequency domain, which is equal to one (useful) OFDM symbol in the time domain, which is equal to N samples in the time domain. One OFDM symbol in the time domain, Ns, is equal to Ncp(the number of guard samples per OFDM symbol)+N (the number of useful samples per OFDM symbol).

The N parallel time domain sample streams318may be converted into an OFDM/OFDMA symbol stream322by a parallel-to-serial (P/S) converter324. A guard insertion component326may insert a guard interval between successive OFDM/OFDMA symbols in the OFDM/OFDMA symbol stream322. The output of the guard insertion component326may then be upconverted to a desired transmit frequency band by a radio frequency (RF) front end328. An antenna330may then transmit the resulting signal332.

FIG. 3also illustrates an example of a receiver304that may be used within a wireless communication system100that utilizes OFDM/OFDMA. Portions of the receiver304may be implemented in the receiver212of a wireless device202. The receiver304may be implemented in a user terminal106for receiving data306from a base station104on a downlink108. The receiver304may also be implemented in a base station104for receiving data306from a user terminal106on an uplink110.

The transmitted signal332is shown traveling over a wireless channel334. When a signal332′ is received by an antenna330′, the received signal332′ may be downconverted to a baseband signal by an RF front end328′. A guard removal component326′ may then remove the guard interval that was inserted between OFDM/OFDMA symbols by the guard insertion component326.

The output of the guard removal component326′ may be provided to an S/P converter324′. The S/P converter324′ may divide the OFDM/OFDMA symbol stream322′ into the N parallel time-domain symbol streams318′, each of which corresponds to one of the N orthogonal subcarriers. A fast Fourier transform (FFT) component320′ may convert the N parallel time-domain symbol streams318′ into the frequency domain and output N parallel frequency-domain symbol streams316′.

A demapper312′ may perform the inverse of the symbol mapping operation that was performed by the mapper312, thereby outputting N parallel data streams310′. A P/S converter308′ may combine the N parallel data streams310′ into a single data stream306′. Ideally, this data stream306′ corresponds to the data306that was provided as input to the transmitter302.

Exemplary OFDM/OFDMA Frame with CID Scheduling Message

Referring now toFIG. 4A, an OFDM/OFDMA frame400containing a multicast/broadcast CID scheduling message for a Time Division Duplex (TDD) implementation is depicted as a typical, but not limiting, example. As illustrated, the CID scheduling message may be included in the DL-MAP414as a CID MAP415for certain embodiments. As will be described in greater detail below, the CID scheduling message may provide the location, within the frame400, of DL-Bursts associated with particular multicast/broadcast CIDs. As the DL-MAP414is decoded by all user terminals, including the CID scheduling message in the DL-MAP414allows all user terminals access to the scheduling information contained therein.

Other implementations of an OFDM/OFDMA frame, such as Full and Half-Duplex Frequency Division Duplex (FDD) may be used, in which case the frame is the same except that both downlink (DL) and uplink (UL) messages are transmitted simultaneously over different carriers. In the TDD implementation illustrated, each frame may be divided into a DL subframe402and a UL subframe404, which may be separated by a small guard interval406—or, more specifically, by Transmit/Receive and Receive/Transmit Transition Gaps (TTG and RTG, respectively)—in an effort to prevent DL and UL transmission collisions. The DL-to-UL-subframe ratio may be varied from 3:1 to 1:1 to support different traffic profiles.

Within the OFDM/OFDMA frame400, various control information may be included. For example, the first OFDM/OFDMA symbol of the frame400may be a preamble408, which may contain several pilot signals (pilots) used for synchronization. Fixed pilot sequences inside the preamble408may allow the receiver304to estimate frequency and phase errors and to synchronize to the transmitter302. Moreover, fixed pilot sequences in the preamble408may be utilized to estimate and equalize wireless channels. The preamble408may contain BPSK-modulated carriers and is typically one OFDM symbol long. The carriers of the preamble408may be power boosted and are typically a few decibels (dB) (e.g., 9 dB) higher than the power level in the frequency domain of data portions in the WiMAX signal. The number of preamble carriers used may indicate which of the three segments of the zone are used. For example, carriers0,3,6, . . . may indicate that segment0is to be used, carriers1,4,7, . . . may indicate that segment1is to be used, and carriers2,5,8, . . . may indicate that segment2is to be used.

A Frame Control Header (FCH)410may follow the preamble408. The FCH410may provide frame configuration information, such as the usable subchannels, the modulation and coding scheme, and the MAP message length for the current OFDM/OFDMA frame. A data structure, such as the downlink Frame Prefix (DLFP)412, outlining the frame configuration information may be mapped to the FCH410.

As illustrated inFIG. 4B, the DLFP412for Mobile WiMAX may comprise six bits for the used subchannel (SCH) bitmap412a, a reserved bit412bset to 0, two bits for the repetition coding indication412c, three bits for the coding indication412d, eight bits for the MAP message length412e, and four reserved bits412fset to 0 for a total of 24 bits in the DLFP412. Before being mapped to the FCH410, the 24-bit DLFP may be duplicated to form a 48-bit block, which is the minimal forward error correction (FEC) block size.

Following the FCH410, a DL-MAP414and a UL-MAP416may specify data burst allocation and other control information for the DL and UL subframes402,404. In the case of OFDMA, multiple users may be allocated data regions within the frame, and these allocations may be specified in the DL and UL-MAP messages414,416. The MAP messages may include the burst profile for each user, which defines the modulation and coding scheme used in a particular link. Since MAP messages contain critical information that needs to reach all users, the DL and UL-MAP messages414,416may often be sent over a very reliable link, such as BPSK or QPSK with rate ½ coding and repetition coding. The DL subframe402of the OFDM/OFDMA frame may include DL bursts of various bit lengths containing the downlink data being communicated.

Thus, the DL-MAP414may describe the location of the bursts contained in the downlink zones and the number of downlink bursts, as well as their offsets and lengths in both the time (i.e., symbol) and the frequency (i.e., subcarrier or subchannel) directions. For certain embodiments, the CID scheduling message (e.g., CID MAP415) may provide additional information about the location, within the frame400, for multicast/broadcast data bursts associated with particular CIDs. Providing this information in the CID scheduling message may allow a user terminal to bypass particular DL bursts associated with CIDs that are not of interest. For certain embodiments, a user terminal may power down certain components if portions to be bypassed allow sufficient time.

Likewise, the UL subframe404may include UL bursts of various bit lengths composed of the uplink data being communicated. Therefore, the UL-MAP416, transmitted as the first burst in the downlink subframe402, may contain information about the location of the UL burst for different users. The UL subframe404may include additional control information as illustrated inFIG. 4A. The UL subframe404may include a UL ACK418allocated for the mobile station (MS) to feed back a DL hybrid automatic repeat request acknowledge (HARQ ACK) and/or a UL CQICH420allocated for the MS to feed back channel state information on the Channel Quality Indicator channel (CQICH). Furthermore, the UL subframe404may comprise a UL Ranging subchannel422. The UL Ranging subchannel422may be allocated for the MS to perform closed-loop time, frequency, and power adjustment, as well as bandwidth requests. Altogether, the preamble408, the FCH410, the DL-MAP414, and the UL-MAP416may carry information that enables the receiver304to correctly demodulate the received signal.

For OFDMA, different “modes” can be used for transmission in DL and UL. An area in the time domain where a certain mode is used is generally referred to as a zone. One type of zone is called DL-PUSC (downlink partial usage of subchannels) and may not use all the subchannels available to it (i.e., a DL-PUSC zone may only use particular groups of subchannels). There may be a total of six subchannel groups, which can be assigned to up to three segments. Thus, a segment can contain one to six subchannel groups (e.g., segment0contains the first two subchannel groups, segment1contains the next two, and segment2contains the last two subchannel groups). Another type of zone is called DL-FUSC (downlink full usage of subchannels). Unlike DL-PUSC, DL-FUSC does not use any segments, but can distribute all bursts over the complete frequency range.

Exemplary DL-MAP with a CID Scheduling Message

The DL-MAP414ofFIG. 4A, containing a multicast/broadcast CID scheduling message, is illustrated in more detail inFIG. 5.

The DL-MAP414may begin with a Management Message Type502having a length of 8 bits, which has a value of 2 (00000010b) to indicate the control message is a DL-MAP. The Management Message Type502may be followed by a frame duration code504, which is 8 bits long, and a frame number506, which is 24 bits long. The frame number506may be followed by a Downlink Channel Descriptor (DCD) count508having a length of 8 bits and matching the DCD configuration change count value. The DCD message refers to physical (PHY) and Media Access Control (MAC) layer-related parameters to be applied to each burst interval allocated to the downlink, which include a modulation type, a forward error correction (FEC) code type, and the like. The DCD count508may be followed by a base station identifier (BSID)510, having a length of 6 bytes for a total length of 48 bits. The BSID510may uniquely identify the network base station and may be followed by a DL symbol duration512indicating a number of OFDMA symbols in the DL subframe402and having a length of 8 bits.

A number (n) of DL-MAP information elements (IEs)514having variable lengths may follow the DL symbol duration512. A generic DL-MAP IE514may comprise a Downlink Interval Usage Code (DIUC)516, a list of connection IDs518, and the DL burst allocation520(e.g., subchannel offset, symbol offset, subchannel number, and symbol number) to define a downlink transmission. A DIUC516between 0 and 12 inclusive may indicate that the DL-MAP IE provides a DL burst profile (i.e., the modulation and coding scheme used in the burst), while a DIUC516of 14 or 15 may indicate that the DL-MAP IE is a control information element. A DIUC516having a 4-bit value of 15 (1111b) may indicate a DL-MAP Extended IE, and a DIUC516having a 4-bit value of 14 (1110b) may indicate a DL-MAP Extended-2 IE. A DIUC516of 13 may indicate that the DL-MAP IE is used for safety zones (i.e., gap) and peak-to-average-power ratio (PAPR) reduction. Although not shown inFIG. 5, some embodiments of the DL-MAP414may include padding having a length of 4 bits in an effort to reach a byte boundary for the DL-MAP414.

Exemplary MAC PDU

Referring now toFIG. 6, the DL bursts within the OFDM/OFDMA frame400may comprise one or more Media Access Control (MAC) protocol data units (PDUs)600containing MAC management messages or user data. A typical MAC PDU600may consist of three components: a generic MAC header (GMH)602containing PDU control information, a variable length PDU body known as the payload604containing information specific to the PDU type, and an optional frame check sequence (FCS), which may contain an IEEE 32-bit (4-byte) cyclic redundancy check (CRC)606code. Containing the actual MAC management message or the user data, the payload604may vary in length from 0 to 2041 bytes if there is no CRC present or may vary from 0 to 2037 bytes with the CRC606present. For OFDMA, the CRC606is typically mandatory.

The GMH602may comprise a 1-bit header type (HT)608having a value equal to 0. A header type equal to 1 may indicate a MAC signaling header for uplink transmission or a compressed/reduced private DL-MAP for downlink transmission, which are beyond the scope of this disclosure. The HT608may be followed by a 1-bit encryption control (EC)610indicating whether the payload604is encrypted and a 6-bit type field612, thereby composing the first byte of the GMH602. The type field612may indicate the PDU type and any subheaders or special payload types in the message payload604.

The next byte of the GMH602may include a 1-bit extended subheader field (ESF)614, a 1-bit CRC indicator (CI)6, a 2-bit encryption key sequence (EKS)616providing an index into a vector of encryption key information, and a reserved bit618. Following the reserved bit618, a length field620may indicate the length of the MAC PDU in bytes including the length of the GMH602. The length field620may be divided into two different bytes of the GMH602, wherein the first portion620atypically includes the first three bits including the most significant bit (MSB) of the length field620and the second portion620btypically includes the last 8 bits including the least significant bit (LSB).

A two-byte connection identifier (CID)622(shown in separate bytes, as622aand622b) may follow the length field620for a total of 6 bytes in the GMH602. As a MAC-layer address, the CID622may uniquely identify a connection, which, as defined herein, generally refers to a unidirectional mapping between MAC peers over the airlink. A connection may be a unicast connection between a base station (BS)104and a user terminal106(MS). For multicast and broadcast services (MBS) where multicast or broadcast information is intended for delivery to a plurality of user terminals (e.g. subscriber stations or mobile stations), the BS104may provide the user terminal106with access by creating a multicast traffic connection with each user terminal to be associated with the service or a broadcast transport connection. The CID622used for the MBS may be the same for all user terminals on the same channel that participate in the connection.

A one-byte header check sequence (HCS)624may follow the CID622in the generic MAC header602. The HCS624may provide a CRC in an effort to detect errors in the GMH602.

FIG. 7illustrates examples of MAC PDU construction including fragmentation and packing. In the convergence sublayer (CS) of the MAC (layer2in the Open System Interconnection (OSI) Reference Model), a packet header suppression identifier (PHSI)702may be added to a packet PDU704from a higher layer, such as the network layer (layer3in the OSI Reference Model), in an effort to form a MAC service data unit (SDU)706.

Depending on various factors, such as the quality of service (QoS) desired and the available bandwidth, the entire MAC SDU706may be incorporated into the payload604of a MAC PDU708by a lower sublayer of the MAC, such as the MAC common part sublayer (CPS) for certain instances. In other instances, the MAC SDU706may be divided into two MAC SDU fragments7101,7102. The MAC SDU fragments710may have different lengths. Each fragment710may be incorporated into the payload604of a different MAC PDU712following a fragmentation subheader714. Fragmentation may allow efficient use of available bandwidth relative to the QoS requirements of a connection's service flow.

In contrast with fragmentation in which one MAC SDU706is divided into a plurality of MAC SDU fragments710, another MAC PDU construction technique comprises packing, in which multiple MAC SDUs are combined in the payload604of a single MAC PDU. For example, a first MAC SDU7061and a second MAC SDU7062, which may have different lengths, may be incorporated into a single MAC PDU716. Each MAC SDU706in the payload604may be preceded by a packing subheader718.

A DL burst may contain one or more MAC PDUs708,712,716of various types concatenated together within the burst. Thus, a DL burst may contain one or more CIDs622, some of which may signify multicast traffic connections or broadcast transport connections.

Exemplary Method of Using a Multicast/Broadcast CID Scheduling Message

Without multicast/broadcast CID scheduling information indicating the location of WiMAX multicast/broadcast bursts of interest, a user terminal might inefficiently parse an entire frame only to filter out the MAC PDUs within the DL bursts of the OFDM/OFDMA frame that are not intended for that user terminal based on the CID for a multicast traffic connection or a broadcast transport connection. In such a scenario, after determining which MAC PDUs are intended for that user terminal, the user terminal may begin processing and decoding the multicast/broadcast data such that the data may be sent from the MAC layer to higher layers. However, especially in cases where the portion of the DL subframe for multicast/broadcast data is a small fraction of the DL subframe data, a user terminal may spend a lot of overhead in the CID filtering process, parsing the MAC PDUs.

By providing multicast/broadcast CID scheduling information (e.g., in a CID scheduling MAC management message), certain embodiments of the present disclosure provide methods and apparatus to bypass at least some of the MAC PDU parsing in an effort to reduce the overhead spent in the CID filtering process. Since the scheduling and resource allocation for multicast/broadcast data within an OFDM/OFDMA frame is known to the base station104before a signal based on a particular frame is broadcast, the scheduling information may be incorporated into the frame. In this manner, a given user terminal receiving the signal may use the scheduling information to avoid parsing at least a portion of the DL subframe402that does not pertain to that particular user terminal.

The multicast/broadcast scheduling information may be incorporated into an OFDM/OFDMA frame in any suitable manner. The scheduling information may be considered as a MAC management message and may be based on the CIDs for multicast and broadcast connections. Such a multicast/broadcast CID scheduling MAC management message may comprise CID information, timing information, and modulation information. The CID information may allow a user terminal to determine whether the multicast/broadcast CID scheduling message applies to that particular user terminal. The timing information may denote the starting OFDM/OFDMA symbol for the multicast/broadcast data or where the user terminal may begin parsing the MAC PDUs in the DL subframe. The modulation information may signify the user terminal which modulation and coding scheme was used to encode the multicast/broadcast data.

For certain embodiments, the multicast/broadcast CID scheduling message may be included in the DL-MAP414as illustrated inFIG. 5. In such cases, the CID scheduling message may be a CID MAP and may be configured as a DL-MAP IE514, such as the multicast/broadcast (MB) CID MAP IE located as the first DL-MAP IE5141following the DL symbol duration512. First DL-MAP IE5141may be followed by a second DL-MAP IE5142, and so on, through n DL-MAP ILEs512nThe MB CID MAP IE may be located in any DL-MAP IE position. Being a control IE, the MB CID MAP IE may be a DL-MAP Extended IE or a DL-MAP Extended-2 IE. Because the DL-MAP may most likely be sent over a very reliable link, such as BPSK or QPSK with rate ½ coding and repetition coding as described above, most if not all user terminals may most likely be able to receive the MB CID MAP IE.

For certain other embodiments, the multicast/broadcast CID scheduling MAC management message may be incorporated as one or more MAC PDUs within a DL burst of the OFDM/OFDMA frame. In an effort to save CID filtering overhead, the multicast/broadcast CID scheduling message may most likely reside in one of the earlier DL bursts (i.e. a DL burst having a lower symbol index), such as the first DL burst after the UL-MAP416, as opposed to a later DL burst (i.e., a DL burst with a higher symbol index). However, if the DL burst containing the MAC PDU(s) with the multicast/broadcast scheduling message is transmitted with a higher-order modulation and coding scheme, not all user terminals may be able to receive the CID scheduling message.

FIG. 8is a flow diagram of example operations800for transmitting CID scheduling information in an OFDM/OFDMA frame, using a multicast/broadcast CID scheduling message in the DL-MAP. The operations800may, for example, be performed by a base station104.

The operations800begin, at802, by obtaining scheduling multicast/broadcast CID scheduling information. The base station will have this information, as it already allocates the different CID DL bursts among the frame. At804, a CID scheduling MAC management message containing the CID scheduling information is generated. This message may include the CID scheduling information in any suitable format, for example, as a list of CIDs and pointer information indicating the locations within the frame for the corresponding data bursts.

At806, the CID scheduling MAC management message is transmitted in the DL-MAP of a frame. A user terminal receiving this message may bypass processing DL bursts pertaining to CIDs that are not of interest.

FIG. 9is a flow diagram of example operations900for processing an OFDM/OFDMA frame and bypassing a portion of the frame parsing based on the scheduling message. The operations900may begin, at902, by receiving a signal based on an OFDM/OFDMA frame. At904, the DL-MAP414of the OFDM/OFDMA frame may be decoded, and a multicast/broadcast CID scheduling message may be extracted from the DL-MAP at906.

At908, at least a portion of the OFDM/OFDMA frame may be bypassed when parsing the MAC PDUs based on the extracted multicast/broadcast CID scheduling message. For example, the multicast/broadcast CID scheduling message may indicate that the DL subframe does not contain any multicast/broadcast data, and in such cases, the entire DL subframe—or at least the remaining portion after processing the DL-MAP414and UL-MAP416—may be bypassed. As another example, the DL subframe may contain multicast/broadcast data, but the multicast/broadcast CID scheduling message may indicate that one or more DL bursts do not contain any multicast/broadcast data. In such cases, any one, a combination, or all of these DL bursts may be bypassed according to the CID scheduling message. As yet another example, a given DL burst may contain multicast/broadcast data, but the multicast/broadcast CID scheduling message may indicate that one or more MAC PDUs within the particular DL burst do not contain any multicast/broadcast data. In such cases, any one, a combination, or all of these MAC PDUs may be bypassed according to the CID scheduling message.

Taking this one step further,FIG. 7illustrates that some MAC PDUs716may contain more than one MAC SDU706. In some cases, one or more of the MAC SDUs may be multicast/broadcast data, while the other MAC SDUs may comprise other elements, such as unicast data or a control message. Therefore, the multicast/broadcast CID scheduling message may indicate that a portion of a MAC PDU does not contain any multicast/broadcast data. In such cases, any one, a combination, or all of these MAC SDUs without multicast/broadcast data may be bypassed according to the CID scheduling message.

For certain embodiments, whether there is sufficient time to power down circuitry related to MAC PDU parsing and processing in a user terminal that received the signal may be determined at910. To determine this, the time period for bypassing a portion of the DL subframe according to the multicast/broadcast CID scheduling message (i.e., the bypass period) may be compared against a predetermined threshold, for example. If the bypass period is greater than the predetermined threshold, the circuitry may be powered down at912during the bypass period. In this manner, the user terminal may conserve power, which may be especially desirable for battery-powered user terminals, such as cell phones or laptop computers. If the bypass period is not greater than the predetermined threshold, the related circuitry may remain powered on during the bypass period.

For example, suppose that DL Burst #5inFIG. 4Acontains broadcast data and that the MAC PDUs within DL Burst #5contain a CID622according to one or more broadcast transport connections. The DL-MAP414may comprise a multicast/broadcast CID scheduling message denoting that a user terminal interested in only the multicast/broadcast data may potentially bypass parsing the MAC PDUs of the DL subframe in all of the DL bursts with the exception of DL Burst #5. In this case, the bypass period may start after the OFDM/OFDMA symbols for the UL-MAP416and may end at the OFDM/OFDMA symbols for the DL Burst #5. The bypass period for this particular user terminal may be determined to be sufficiently long at910such that the user terminal circuitry related to MAC PDU parsing and processing (which is normally on) may be powered down at912during the bypass period. This related circuitry may be powered up in an effort to parse and process the MAC PDUs within DL Burst #5according to the multicast/broadcast CID scheduling message.

Returning toFIG. 9, any remaining portion of the DL subframe that is not bypassed may be parsed, and the MAC PDUs pertaining to the user terminal that received the signal according to the CIDs622may be processed (e.g., decoded). Once portions of the DL subframe402have been bypassed or processed and the UL subframe404has been transmitted, the user terminal(s) may wait to receive a new signal based on a new OFDM/OFDMA frame, and the operations900may repeat beginning at902.

The operations described above may be performed by various hardware and/or software component(s) and/or module(s) corresponding to a number of means-plus-function blocks. For example, the operations800and900ofFIGS. 8 and 9described above may be performed by various hardware and/or software component(s) and/or module(s) corresponding to the means-plus-function blocks800A-806A and900A-912A illustrated inFIGS. 8A and 9A, respectively.

Information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals and the like that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles or any combination thereof.