KR20060086439A - Frequency division multiplexing of multiple data streams in a wireless multi-carrier communication system - Google Patents

Abstract

Techniques for multiplexing multiple data streams using frequency division multiplexing (FDM) in an OFDM system are described. M disjoint "interlaces" are formed with U usable subbands. Each interlace is a different set of S subbands, where. The subbands for each interlace are interlaced with the subbands for each of the other interlaces. M slots may be defined for each symbol period and assigned slot indices 1 through M. The slot indices may be mapped to interlaces such that (1) frequency diversity is achieved for each slot index and (2) the interlaces used for pilot transmission have varying distances to the interlaces used for each slot index, which improves channel estimation performance. Each data stream may be processed as data packets of a fixed size, and different numbers of slots may be used for each data packet depending on the coding and modulation scheme used for the data packet.

Description

FREQUENCY DIVISION MULTIPLEXING OF MULTIPLE DATA STREAMS IN A WIRELESS MULTI-CARRIER COMMUNICATION SYSTEM}

This application is filed on September 1, 2004, with the title of the invention "A Method for Multiplexing and Transmitting Multiple Multimedia Streams to Mobile Terminals over Terrestrial Radio," and US Patent Application No. 10 / 932,586, filed April 2004. US patent provisional application dated May 5, entitled "Multiplexing and Transmission of Multiple data Streams in a Wireless Multi-Carrier Communication System", and application number 60 / 559,740, and application date October 24, 2003, titled invention This is "A Method for Frequency-Division Multiplex Various Multimedia Streams for Multicast Wireless Transmission to Mobile Devices" and claims priority to US patent provisional application with application number 60 / 514,315.

TECHNICAL FIELD The present invention relates generally to communications and, more particularly, to techniques for multiplexing multiple data streams in a wireless multi-carrier communication system.

Multi-carrier communication systems use multiple carriers for data transmission. Such multiple carriers may be provided by orthogonal frequency division multiplexing (OFDM), some other multi-carrier modulation techniques, or some other configuration. OFDM effectively partitions the overall system bandwidth into multiple (N) orthogonal frequency subbands. These subbands are also referred to as tones, carriers, subcarriers, bins and frequency channels. With OFDM, each subband is associated with each subcarrier that can be modulated with data.

A base station of a multi-carrier communication system can transmit multiple data streams simultaneously. Each data stream may be processed separately (eg, coded and modulated) at the base station, and thus may be independently reconstructed (eg, demodulated and decoded) by the wireless device. Multiple data streams may have fixed or variable data rates and may use the same or different coding and modulation schemes.

Multiplexing multiple data streams for simultaneous transmission may be attempted if these streams are variable (eg, have data rates and / or coding and modulation schemes that change over time). In one simple multiplexing scheme, multiple data streams are assigned to different time slots or symbol periods using time division multiplexing (TDM). In this TDM scheme, only one data stream is transmitted at any given moment, so this data stream uses all the subbands available for data transmission. This TDM scheme has undesirable characteristics. First, the amount of data that can be transmitted in the minimum time unit allocable for a given data stream, which can be viewed as the "granularity" for the data stream, depends on the coding and modulation scheme used for the data stream. . Different coding and modulation schemes can be associated with different sophistication, which can complicate the allocation of resources to data streams and cause inefficient resource usage. Second, if the precision for a given coding and modulation schemes is relatively too high for the decoding function of the wireless device, a large input buffer may be required at the wireless device to store the received symbols.

Therefore, there is a technical need for techniques for multiplexing multiple data streams efficiently in a multi-carrier communication system.

Techniques for multiplexing multiple data streams using frequency division multiplexing (FDM) in wireless multi-carrier (eg, OFDM) are presented herein. In one embodiment, M disjoint or non-overlapping “interlaces” are formed over U subbands usable for transmission (where M> 1 and U> 1). . Interlaces are not overlapped because each usable subband is contained within only one interlace. Each interlace is a different set of S subbands, where U = M.S. The S subbands in each interlace may be selected from the S 'subbands evenly distributed across the N total subbands and spaced at equal intervals by the M subbands (where N = M S 'and S'> = S). This interlaced subband structure can provide frequency diversity and simplify processing at the receiver. For example, the receiver may perform a "partial" S'-point fast Fourier transform (FFT) for each interlace of interest, instead of a full N-point Fourier transform (FFT). M interlaces may be used to transmit multiple data streams in an FDM manner. In one embodiment, each interlace is used by only one data stream in each symbol period, and up to M data streams may be transmitted over M interlaces in each symbol period.

In one embodiment, multiple data streams are assigned to "slots," each slot being a transmission unit equivalent to one interlace in one symbol period. M slots are available in each symbol period and may be assigned slot indices from 1 to M. Each slot index may be mapped to one interlace in each symbol period based on a slot-to-interlace mapping scheme. One or more slot indices may be used for the FDM pilot, and the remaining slot indices may be used for data transmission. Slot-to-interlace mapping may be made such that the interlaces used for pilot transmission have varying distances to the interlaces used for each slot index in different OFDM symbol periods. This allows all slot indices used for data transmission to achieve similar channel estimation performance.

Each data stream can be treated as data packets of fixed size. In this case, different numbers of slots may be used for each data packet depending on the coding and modulation scheme used for that data packet. Alternatively, each data stream can be treated as data packets with variable sizes. For example, packet sizes may be selected such that an integer number of data packets are sent in each slot. In any case, if multiple data packets are transmitted in a given slot, the data symbols for each data packet can be distributed over all subbands used for the slot, resulting in for each data packet transmitted in the slot. Frequency diversity is achieved.

Various aspects and embodiments of the invention are described in more detail below.

The features and characteristics of the present invention will become more apparent from the following detailed description and drawings.

1 shows a block diagram for a base station and a wireless device.

2 shows an exemplary super-frame structure.

3 shows an interlaced subband structure.

4A and 4B show “staggered” and “cycled” FDM pilots, respectively.

5 illustrates an example mapping of slot indices and interlaces.

6 shows coding of a data block using an outer code.

7A and 7B illustrate the transmission of packets in different modes.

8A and 8B illustrate dividing a different number of packets into slots.

9A shows a block diagram of a transmit (TX) data processor.

9B shows a block diagram of a modulator.

10A shows a block diagram of a demodulator.

10B shows a block diagram of a receive (RX) data processor.

The word "examplary" is used herein to mean "presenting as an example, illustration or explanation." Any embodiment or design described herein as "exemplary" is not to be construed as preferred or advantageous over other embodiments or designs.

The multiplexing techniques presented herein may be used for various wireless multi-carrier communication systems. These techniques can also be used for the uplink as well as the downlink. The downlink (or forward link) refers to the communication link from base stations to wireless devices, and the uplink (or reverse link) refers to the communication link from wireless devices to base stations. For clarity, these techniques will be described below for the downlink in an OFDM-based system.

1 shows a block diagram of a base station 110 and a wireless device 150 in a wireless system 100 using OFDM. Base station 110 is generally a fixed station and may also be referred to as a base transceiver system (BTS), an access point, a transmitter, or some other terminology. Wireless device 150 may be fixed or mobile and may be referred to as a user terminal, mobile station, receiver, or some other terminology. Wireless device 150 may also be a portable unit such as a cellular phone, a handheld device, a wireless module, a personal digital assistant (PDA), or the like.

At base station 110, TX data processor 120 receives multiple (T) data streams (or “traffic” data) and processes each data stream (eg, encodes, interleaves) to generate data symbols. And symbol mapping). As used herein, a “data symbol” is a modulation symbol for traffic data, a “pilot symbol” is a modulation symbol for a pilot (data known to both base stations and wireless devices), and a modulation symbol is a modulation scheme (eg For example, it is a complex value for one point in the signal array for M-PSK, M-QAM, etc.). TX data processor 120 also multiplexes the data symbols and pilot symbols for the T data streams over the appropriate subbands to provide a composite symbol stream. Modulator 130 performs OFDM modulation on the multiplexed symbols in the composite symbol stream to produce OFDM symbols. Transmitter unit (TMTR) 132 converts (eg, amplifies, filters, and frequency upconverts) the analog signals to convert OFDM symbols into analog signals and further generate a modulated signal. Base station 110 then transmits the modulated signal from antenna 134 to wireless devices in the system.

In wireless device 150, a signal transmitted from base station 110 is received by antenna 152 and provided to a receiver unit (RCVR) 154. Receiver unit 154 digitizes the adjusted signal to adjust (eg, filter, amplify and frequency downconvert) the received signals and generate a stream of input samples. Demodulator 160 performs OFDM demodulation on input samples to obtain received symbols for one or more data streams of interest, and additionally detects (eg, detects received symbols to obtain detected data symbols). Equalization or matching filtering), and the detected data symbols are estimates for the data symbols transmitted by the base station 110. The RX data processor 170 then processes (eg, symbol demaps, deinterleaves, and decodes) the detected symbol streams for each selected data stream and provides decoded data for that stream. Processing by demodulator 160 and RX data processor 170 is complementary to processing by modulator 130 and TX data processor 120 at base station 110.

Controllers 140 and 180 direct operation at base station 110 and wireless device 150, respectively. Memory units 142 and 182 provide storage for program codes and data used by controllers 140 and 180, respectively. Controller 140 or scheduler 144 may allocate system resources for the T data streams.

Base station 110 may transmit T data streams for various services, such as broadcast, multicast, and / or unicast services. Broadcast transmissions are sent to all wireless devices within a specified coverage area, multicast transmissions are sent to a group of wireless devices, and unicast transmissions are sent to a specific wireless device. For example, base station 110 may broadcast multiple data streams for multimedia (eg, television) programs and multimedia content such as video, audio, teletext, data, video / audio clips, and the like. . One multimedia program can be broadcast as three separate data streams for video, audio and data. This allows the video, audio and data portions of the multimedia program to be received independently at the wireless device.

2 illustrates an example super-frame structure 200 that may be used in the system 100. T data streams can be transmitted within a super-frame, with each super-frame having a predetermined time period. Super-frames may also be referred to as frames, time slots, or some other terminology. In the embodiment shown in FIG. 2, each super-frame includes a field 212 for one or more TDM pilots, a field 214 for overhead / control data, and a field 216 for traffic data. The TDM pilot (s) can be used by the wireless device for synchronization (eg, frame detection, frequency error estimation, timing acquisition, etc.). The overhead / control data indicates various parameters for the T data streams (eg, the coding and modulation scheme used for each data stream, the specific location of each data stream within the super-frame, etc.). can do. T data streams are sent in field 216. Although not shown in FIG. 2, each super-frame may be divided into multiple (eg, four) same-sized frames to facilitate data transfer. Other frame structures may also be used for the system 100.

3 illustrates an interlaced subband structure 300 that may be used in system 100. System 100 uses an OFDM structure with N total subbands. U subbands may be used for data and pilot transmission and are referred to as “usable” subbands (where U <= N). The remaining G subbands are not used and are referred to as "guard" subbands (where N = U + G). By way of example, system 100 may use an OFDM structure with N = 4096 full subbands, U = 4000 usable subbands, and G = 96 guard subbands.

U usable subbands may be arranged in M interlaces or disjoint subband sets. The M interlaces are not disjointed or overlapped because each of the U usable subbands belongs to only one interlaces. Each interlace contains S usable subbands (where U = M.S). Each interlace can be associated with a different group of S '= N / M subbands uniformly distributed across the N total subbands, such that consecutive subbands in the group are spatially as M subbands as possible. It is located away. For example, group 1 may include subband 1, M + 1, 2M + 1, etc., group 2 may include subbands 2, M + 2, 2M + 2, etc., and group M may include Subbands M, 2M, 3M, and the like. In each group, S of the S 'subbands are usable subbands and the remaining S'-S subbands are guard subbands. Each interlace may then include the S available subbands in the group associated with it. In the example OFDM structure described above, M = 8 interlaces may be formed, with each interlace selected from S ′ = 512 subbands spaced at equal intervals by M = 8 subbands. Two usable subbands. Thus, the S usable subbands in each interlace are interlaced with the S usable subbands in each of the other M-1 interlaces.

In general, a system can use any OFDM structure with any number of total subbands, usable subbands, and guard subbands. In addition, any number of interlaces may be formed. Each interlace may include any number of usable subbands and any of the U usable subbands. Interlaces can also include the same or different numbers of usable subbands. For simplicity, the following description is made for the interlacing subband structure shown in FIG. 3, which has S interleaved subbands with M interlaces and each interlace uniformly distributed. This interlaced subband structure provides several advantages. First, frequency diversity is achieved because each interlace includes usable subbands taken over the entire system bandwidth. Second, the wireless device can recover the data / pilot symbols transmitted over a given interlace by performing a partial S'-point FFT instead of the full N-point FFT, which can simplify the processing of the wireless device.

Base station 110 may send an FDM pilot over one or more interlaces to allow wireless devices to perform various functions, such as, for example, channel estimation, frequency tracking, time tracking, and the like. The base station 110 may transmit FDM pilot and traffic data in various ways.

4A shows a data and pilot transmission scheme 400 with a “stagger” FDM pilot. In the case of M = 8, one interlace is used for the FDM pilot in each symbol period, and the remaining seven interlaces are used for traffic data. The FDM pilot is transmitted on two designated interlaces in an alternative manner, with the result that the pilot symbols are over one interlace (e.g. interlace 3) in odd symbol periods and another interlace (e.g. in even symbol periods). For example, it is transmitted through interlace 7). The two interlaces used for the FDM pilot are staggered or offset by M / 2 = 4 interlaces. This staggering allows wireless devices to observe the channel response for more subbands, which can improve performance.

4B shows a data and pilot transmission scheme 410 with a "cycled" FDM pilot. In the case of M = 8, one interlace is used for the FDM pilot in each symbol period and the remaining seven interlaces are used for traffic data. The FDM pilot is sent on all eight interlaces in a circular fashion, with the result that pilot symbols are sent on different interlaces during each M-symbol period. For example, an FDM pilot is transmitted over interlace 1 in symbol period 1, interlace 5 in symbol period 2, interlace 2 in symbol period 3, and also in the following symbol periods in the same manner and transmitted over interlace 8 in symbol period 8 Thereafter, it is transmitted on interlace 1 again in symbol period 9 and also in subsequent symbol periods in the same manner. This cycling allows the wireless devices to observe the channel response for all available subbands.

In general, an FDM pilot may be sent on any number of interlaces and on any of the M interlaces in each symbol period. The FDM pilot can also be sent using any pattern, two of which are shown in FIGS. 4A and 4B.

Base station 110 may transmit T data streams over M interlaces in various ways. In the first embodiment, each data stream is transmitted on the same one or more interlaces in each symbol period in which the data stream is transmitted. In this embodiment, interlaces are fixedly assigned to each data stream. In a second embodiment, each data stream may be sent on different interlaces in different symbol periods in which the data stream is sent. In such an embodiment, interlaces are dynamically assigned to each data stream, thereby improving frequency diversity and ensuring that the quality of the channel is independent of the slot index or indices assigned to the data stream. The second embodiment can be seen in the form of frequency hopping, which is described in more detail below.

In order to average the channel estimation and detection performance for all T data streams, the transmission scheme 410 can be used for the first embodiment with fixedly assigned interlaces, and the transmission scheme 400 or 410 It can be used for the second embodiment with dynamically allocated interlaces. If an FDM pilot is sent over the same one interlace (referred to as pilot interlace) in each symbol period and used to obtain channel estimates for all M interlaces, the channel for the interlace closer to the pilot interlace Estimation is typically better than channel estimation for interlaces far from the pilot interlace. If the data stream continues to be assigned interlaces far from the pilot interlace, the detection performance for the data stream may be degraded. Allocation of interlaces with varying distances (or spacing or offset) to the pilot interlace can avoid this performance degradation due to channel estimation bias.

In the second embodiment, M slots may be defined for each symbol period, and each slot may be mapped to one interlace in one symbol period. Slots usable for traffic data are also referred to as data slots, and slots usable for FDM pilot are also referred to as pilot slots. M slots in each symbol period may be assigned an index from 1 to M. Slot index 1 may be used for the FDM pilot, and slot indexes 2 through M may be used for data transmission. T data streams may be allocated to slots having indices of 2 to M in each symbol period. The use of slots with fixed indices can simplify the assignment of slots to data streams. The M slot indices may be mapped to M interlaces in each symbol period based on any mapping scheme that may achieve the desired frequency diversity and channel estimation performance.

In the first slot-to-interlace mapping scheme, slot indices are mapped to interlaces in a permutated manner. In the transmission scheme 400 in which M = 8 and one pilot slot and seven data slots in each symbol period, the mapping may be performed as follows. The eight interlaces may be represented by an initial sequence {I ₁ , I ₂ , I ₃ , I ₄ , I ₅ , I ₆ , I ₇ , I ₈ }. The substituted sequence may be formed by {I ₁ , I ₅ , I ₃ , I ₇ , I ₂ , I ₆ , I ₄ , I ₈ }. The i th interlace in the initial sequence is placed in the i _br th position in the substituted sequence (where i ∈ {1... 8}, i _br ∈ {1... 8}), and (i _br -1) Is the bit-reverse index of (i-1). Since these indices start at 1 instead of 0, an offset of -1 is used for i and i _br . For example, when i = 7 and (i-1) = 6, the bit representation is '110', the bit-inversion index is '011', (i _br -1) = 3 and i _br = 4 to be. The seventh interlace of the initial sequence is thus placed in the fourth position in the substituted sequence. After two interlaces used for the FDM pilot are combined in the sequence substituted to form an interlaced sequence shortened _{{I 1, I 5, I} 3/7, I 2, I 6, I 4, I 8} . The kth slot index (or kth data slot index) (where k ({2... 8}) for data transmission is then mapped to the (k-1) th interlace in the shortened interlace sequence. Then, for each symbol period, the shortened interlace sequence is cyclically shifted to the right by two positions and enclosed to the left. The k th data slot index is mapped back to the (k-1) th interlace in the shortened interlaced sequence that is cyclically shifted.

5 shows mapping of slot indices and interlaces for the first mapping scheme described above. Slot index 1, used for the FDM pilot, is mapped to interlaces 3 and 7 via alternating symbol periods for the transmission scheme 400. The data slot index 2 to 8 are mapped to the seven interlaces in the interlaced sequence shorter for one symbol period _{{I 1, I 5, I} 3/7, I 2, I 6, I 4, I 8} , Seven interlaces for the shortened interlaced sequence {I ₄ , I ₈ , I ₁ , I ₅ , I _3/7 , I ₂ , I ₆ } that are cyclically shifted during the second symbol period. As shown in FIG. 5, each data slot index is mapped to seven different interlaces in seven consecutive symbol periods, one of the seven interlaces being interlace 3 or 7. After that all seven data slot indexes will achieve similar performance.

In the second slot-to-interlace mapping scheme, slot indices are matched with interlaces in a pseudo-random manner. A pseudo-random number (PN) generator can be used to generate PN numbers used to map slot indices with interlaces. The PN generator may be implemented via a linear feedback shift register (LFSR) that implements a particular generator polynomial, for example g (x) = x ¹⁵ + x ¹⁴ +1. For each symbol period j, the LFSR is updated and the V least significant bits (LSBs) in the LFSR may be denoted as PN (j) (where j = 1,2,... And V = log _2). M). The k th data slot index (k∈ {2... M}) is interlaced [(PN (j) + k) unless interlace [(PN (j) + k) mod M] +1 is used for the FDM pilot. ) may be mapped to mod M] +1, otherwise it may be mapped to interlace [(PN (j) + k + 1) mod M] +1.

In a third slot-to-interlaced mapping scheme, slot indices are mapped with interlaces in a circular fashion. For each symbol period j, the k th data slot index (k∈ {2... M}) is interlaced [(j) if interlace [(j + k) mod M] +1 is not used for the FDM pilot. + k) may be mapped to mod M] +1, otherwise it may be mapped to interlace [(j + k + 1) mod M] +1.

M slot indices may thus be mapped to M interlaces in various ways. Some example slot-to-interlace mapping schemes have been described above. Other mapping schemes may also be used, which is within the scope of the present invention.

Slots may be allocated to T data streams in various ways. In the first slot allocation scheme, each data stream is allocated with a sufficient number of slots in each super-frame to transmit non-negative integer data packets (ie zero or more data packets). In this manner, data packets can be defined to have a fixed size (ie, a predetermined number of information bits), thereby simplifying the coding and decoding for the data packets. Each fixed size data packet may be coded and modulated to produce a coded packet having a variable size that depends on the coding and modulation scheme used for the packet. The number of slots needed to transmit a coded packet depends on the coding and modulation scheme used for the packet.

In the second slot allocation scheme, each data stream may be allocated to non-negative integer slots in each super-frame, and integer data packets may be sent in each assigned slot. The same coding and modulation scheme can be used for all data packets transmitted in any given slot. Each data packet may have a size that depends on (1) the number of data packets transmitted in the slot and (2) the coding and modulation scheme used for the slot. In this way, data packets can have varying sizes.

Slots may also be allocated for data streams in other ways. For clarity, the following description assumes that the first slot allocation scheme is used by the system.

Each data stream can be coded in a variety of ways. In one embodiment, each data stream may be coded using concatenated code consisting of an outer code and an inner code. The outer code may be a block code, such as a Reed-Solomon (RS) code or some other code. The inner code may be a turbo code, a convolution code or some other code.

6 illustrates an example outer coding scheme using Reed-Solomon outer code. The data stream is divided into data packets. In one embodiment, each data packet has a fixed size and includes a predetermined number of information bits or L information bytes (eg, 1000 bits or 125 bytes). Data packets for a data stream are written to rows of memory, one packet per row. After K _rs data packets are written to K _rs rows, block coding is performed column-wise one column at a time. In one embodiment, each column is coded using the (N _rs , K _rs ) Reed-Solomon code to generate a corresponding codeword containing K _rs bytes (one byte per row) and N _rs bytes. do. First K _{rs of} Codewords The byte is a data byte (also referred to as a systematic byte) and the remaining N _rs -K _rs bytes are parity bytes (which can be used by the wireless device for error correction). Reed-Solomon coding generates N _rs -K _rs parity bytes for each codeword, where the parity bytes are K _rs of data. After the rows are written to the rows N _rs -K _rs to N _rs of the memory. RS block is the K _rs of data It contains rows and N _rs -K _rs rows of parity. In one embodiment, N _rs = 16 and K _rs is a configurable parameter, for example K _rs ∈ {12,14,16}. The Reed-Solomon code is disabled if K _rs = N _rs . Each data / parity packet (or each row) of the RS block is then coded by a turbo inner code to produce a corresponding coded packet. The code block comprises N _rs of coded packets for the N rows of the RS block _rs.

N _rs coded packets for each code block may be transmitted in various ways. For example, each code block may be sent in one super-frame. Each super-frame can be divided into multiple (eg four) frames. Each code block may then be divided into multiple (eg, four) sub-blocks, and each sub-block of the code block may be transmitted in one frame of the super-frame. Transmitting each code block in multiple portions of a super-frame can provide time diversity.

Each data stream may be transmitted through hierarchical coding or without hierarchical coding, where the term “coding” refers to channel coding rather than data coding at the transmitter. The data stream may consist of two substreams, which are referred to as a base stream and an enhancement stream. The base stream may carry basic information and may be sent to all wireless devices within the coverage area of the base station. The enhancement stream may carry additional information and may be sent to wireless devices that maintain better channel conditions. Through hierarchical coding, the elementary stream is coded and modulated to produce a first modulation symbol stream, and the enhancement stream is coded and modulated to produce a second modulation symbol stream. The same or different coding and modulation schemes may be applied for the base stream and enhancement stream. The two modulation symbol streams are then scaled and combined to obtain one data symbol stream.

Table 1 shows an exemplary set of eight “modes” that can be supported by the system 100. These eight modes are provided at indexes 1-8. Each mode is associated with a particular modulation scheme (eg QPSK or 16-QAM) and a particular internal code rate (eg 1/3, 1/2 or 2/3). The first five modes are for "regular" coding using only elementary streams, and the next three modes are for hierarchical coding using elementary and enhancement streams. For simplicity, the same modulation scheme and inner code rate are used for both the basic and enhancement streams for each hierarchical coding mode.

Table 1

The fourth column of Table 1 shows the number of slots required to transmit one fixed size data packet in each mode. Table 1 assumes a data packet size of 2 · S information bits and S usable subbands per slot (e.g., S = 500). Since the slot is mapped to one interlace with S usable subbands and each subband can carry one data symbol, the capacity of each slot has S data symbols. In mode 1, a data packet having 2 S information bits is coded using an internal code whose rate is 1/3 to generate 6 S code bits, and the coding bits are 3 S data using QPSK. Mapped to symbols. Three S data symbols for a data packet can be transmitted in three slots, with each slot carrying S data symbols. Similar processing can be performed for each of the other modes in Table 1.

Table 1 shows an exemplary design. In addition, data packets of other sizes (eg, 500 information bits, 2000 information bits, etc.) may also be used. Also, for example, multiple packet sizes may be used, such that each packet may be sent in an integer number of slots. For example, a packet size with 1000 information bits may be used for modes 1,2 and 4, and a packet size with 1333 information bits may be used for modes 3 and 5. In general, the system may also support any number of modes, any number of data packet sizes, and any packet sizes for any number of coding and modulation schemes.

7A shows transmitting, for each of the first five modes shown in Table 1, at least one integer number of data packets using one slot in each of the number of symbol periods. One data packet may be transmitted using (1) three symbol periods in mode 1, (2) two symbol periods in mode 2, and (3) one slot in one symbol period in mode 4 . In mode 3, since each data packet takes 1.5 slots for transmission, two data packets can be sent using one slot in three symbol periods. In mode 5, since each data packet takes 0.7 slots for transmission, four data packets can be transmitted using one slot in three symbol periods.

7B shows transmitting, for each of the first five modes shown in Table 1, at least integer data packets using integer slots in one symbol period. One data packet may be transmitted in one symbol period using (1) three slots in mode 1, (2) two slots in mode 2, and (3) one slot in mode 4. In mode 3, two data packets may be transmitted in one symbol period using three slots. In mode 5, four data packets may be transmitted in one symbol period using three slots.

As shown in Figures 7A and 7B, the minimum number of data packets may be sent in various ways for each mode (except mode 4). Sending the smallest number of data packets in a short time period reduces the amount of ON time required to receive the data packets but provides less time diversity. The opposite is true when transmitting the minimum number of data packets over a long period of time.

8A shows splitting one coded packet into three slots in mode 1. FIG. Three slots may exist in three different interlaces in one symbol period or in one interlace in three different symbol periods. Three slots can maintain different channel conditions. The bits of the coded packet may be interleaved (ie relocated) before being divided into three slots. Interleaving for each coded packet can randomize the signal-to-noise ratios (SNRs) of the bits over the coded packet, thereby improving decoding performance. Interleaving can be performed in a variety of ways as is known in the art. Interleaving may also ensure that adjacent bits of a coded packet are not transmitted in the same data symbol.

8B shows splitting four coded packets into three slots in mode 5. FIG. Three slots may be filled by four coded packets sequentially as shown in FIG. 8B. If multiple coded packets share a slot (as is the case for modes 3 and 5), all the bits to be sent in the slot can be interleaved, so that the bits for each coded packet sent in the slot are slots. It can be distributed through the subbands used for. Interleaving through each slot can provide frequency diversity for each coded packet transmitted in the slot and can improve decoding performance.

Interleaving through slots can be performed in a variety of ways. In one embodiment, the bits for all coded packets to be transmitted in a given slot are initially mapped with data symbols, and the data symbols are mapped to subbands used for the slot in a substitution manner. In symbol-to-subband mapping, a first sequence having S 'sequential values 0 through S'-1 is initially formed. A second sequence of S 'values is then generated such that the i th value in the second sequence is equal to the bit inversion of the i th value of the first sequence. All values equal to or greater than S 'in the second sequence are removed to obtain a third sequence having S values in the range of 0 to S-1. Each value in the third sequence is incremented by 1 to obtain a sequence of S displaced index values in the range of 1 to S, denoted F (j). The j th data symbol of the slot may be mapped to the F (j) th subband of the interlace used for the slot. For example, if S = 500 and S '= 512, the first sequence is {0,1,2,3 ,. . . , 510,511}, the second sequence is {0, 256, 128, 384,. . . , 255,511}, the third sequence is {0, 256, 128, 384,. . . , 255}. The sequence F (j) is only needed once for the calculation and can be used for all slots. Other mapping schemes may also be used for symbol-to-subband mapping to achieve interleaving through each slot.

In general, each data stream can carry any number of data packets in each super-frame, depending on the data rate of the stream. Each data stream is allocated to a sufficient number of slots in each super-frame based on its data rate, and the data rate depends on the availability of slots and other possible factors. For example, each data stream may be limited to the maximum number of slots specified in each symbol period, with the maximum number of slots dependent on the mode used for the data stream. Each data stream may be limited to a specific maximum data rate, which is the maximum number of information bits that can be transmitted in each symbol period for the data stream. The maximum data rate is typically set by the decoding and buffering functions of wireless devices. Limiting each data stream to within the maximum data rate ensures that the data stream can be recovered by wireless devices having defined decoding and buffering functions. The maximum data rate limits the number of data packets that can be sent in each symbol period for the data stream. The maximum number of slots may be determined by the maximum number of data packets and the mode used for the data stream.

In one embodiment, each data stream may be assigned to an integer number of slots in any given symbol period, with multiple data streams not sharing an interlace. In this embodiment, it is assumed that up to M-1 data streams may be transmitted through M-1 data slots in each symbol period, with one slot being used for the FDM pilot. In another embodiment, multiple data streams may share an interlace.

9A shows a block diagram of one embodiment of TX data processor 120 at base station 110. TX data processor 120 is configured for T TX data stream processors 910a through 910t for T data streams, TX overhead data processor 930 for orderhead / control data, for TDM and FDM pilots. Pilot processor 932 and multiplexer (Mux) 940. Each TX data stream processor 910 processes each data stream {d _i } to produce a corresponding data symbol stream {Y _i } (where i ∈ {1... T}).

Within each TX data stream processor 910, encoder 912 receives and encodes data packets for its data stream {d _i } and provides coded packets. The encoder 912 performs encoding according to a concatenated code consisting of, for example, a Reed-Solomon outer code and a turbo or convolutional inner code. In this case, encoder 912 encodes each block of K _rs data packets to produce N _rs coded packets as shown in FIG. Encoding increases the reliability of the transmission for the data stream. The encoder 912 also generates a cyclic redundancy check (CRC) and appends it to each coded packet, which is then used to correct the error (i.e., determine whether the packet was decoded correctly or there was an error). Can be used by. Encoder 912 may also shuffle coded packets.

Interleaver 914 receives the coded packets from encoder 912 and interleaves the bits of each coded packet to generate an interleaved packet. Interleaving provides time and / or frequency diversity for packets. Slot buffer 916 is filled with interleaved packets for all slots allocated to the data stream, as shown, for example, in FIGS. 8A and 8B.

The scrambler 918 receives the bits for each slot and scrambles with the PN sequence to randomize the bits. M different PN sequences may be used for the M slot indices. M PN sequences may be generated via a linear feedback shift register (LFSR) that implements a particular generator polynomial, for example g (x) = x ¹⁵ + x ¹⁴ +1. The LFSR can be loaded with a different 15-bit initial value for each slot index. In addition, the LFSR may be reloaded at the start of each symbol period. The scrambler 918 may perform an exclusive-OR on one bit in the PN sequence and each bit in the slot to generate scrambled bits.

The bit-to-symbol mapping unit 920 receives the scrambled bits for each slot from the scrambler 918 and converts the bits and modulation symbols according to a modulation scheme (eg, QPSK or 16-QAM). It provides mapping and provides data symbols for the slots. Symbol mapping consists of (1) grouping a set of B bits to form B-bit binary values (where B> = 1), and (2) assigning each B-bit binary value to the signal arrangement for the modulation scheme. This can be accomplished by mapping complex values for one point that is present. The external and internal codes for encoder 912 and the modulation scheme for mapping unit 920 are determined by the mode used for the data stream.

If the data stream is transmitted using hierarchical coding, the elementary stream may be processed by one set of processing units 912-920 to produce a first stream of modulation symbols, and the enhancement stream may be 9 may be processed by another set of processing units 912-920 to produce a second stream of modulation symbols (not shown in FIG. 9). As shown in Table 1, the same coding and modulation scheme may be used for both the base stream and enhancement stream, or different coding and modulation schemes may be used for the two streams. The combiner can then receive and combine the first and second modulation symbol streams to generate data symbols for the data stream. Hierarchical coding can also be performed in other ways. For example, scrambled bits for both the elementary and enhancement streams may be provided in one bit-to-symbol mapping unit that provides data symbols for the data stream.

The slot-to-interlace mapping unit 922 is suitable for interlacing with each slot assigned to the data stream based on the slot-to-interlace mapping scheme used by the system (eg, as shown in FIG. 5). Map. The symbol-to-subband mapping unit 924 then maps the S data symbols in each slot with the appropriate subbands in the slot mapped interlace. Symbol-to-subband mapping may be performed in a manner that distributes S data symbols across the S subbands used for the slot, as described above. Mapping unit 924 provides data symbols for data stream {d _i }, which are mapped with the appropriate subbands used for the data stream.

TX overhead data processor 930 processes the overhead / control data and provides overhead symbols according to the coding and modulation scheme used for the overhead / control data. Pilot processor 932 performs processing on the TDM and FDM pilots and provides pilot symbols. Multiplexer 94 includes mapped data symbols for T data streams from TX data stream processors 910a through 910t, overhead symbols from TX overhead data processor 930, pilot processor 932. Receive pilot symbols and guard symbols from the. The multiplexer 940 provides data symbols, overhead symbols, pilot symbols, and guard symbols in the appropriate subbands and symbol periods based on the MUX_TX control from the controller 140 and synthesized symbol stream {Y _C }. Outputs

9B is a block diagram of one embodiment of a modulator 130 of base station 110. Modulator 130 includes an inverse fast Fourier transform (IFFT) unit 950 and a cyclic prefix generator 952. During each symbol period, the IFFT unit 950 time-domains the N symbols for the N total subbands via the N-point IFFT to obtain a "converted" symbol containing N time-domain samples. Convert to To prevent intersymbol interference (ISI), caused by frequency selective fading, cyclic prefix generator 952 repeats the portion (or C samples) of each transformed symbol to include N + C samples. Form a corresponding OFDM symbol. Repeated portions are often referred to as cyclic prefixes or guard intervals. For example, the length of the cyclic prefix may be C = 512 for N = 4096. Each OFDM symbol is transmitted in one OFDM symbol period (or simply symbol period), which is an N + C sample period. Cyclic prefix generator 952 provides an output sample stream {y} for composite symbol stream {Y _C }.

를 획득한다. 탐지기(1018)는 각각의 선택된 인터레이스에 대한 채널 이득 추정

를 이용하여 각각의 선택된 인터레이스를 위한 S개의 수신된 심볼들의 세트 {X_m(k)}에 대한 탐지(예를 들어, 등화 또는 매칭 필터링)를 수행하고 상기 인터레이스로 S개의 탐지된 데이터 심볼들

를 제공한다. 10A shows a block diagram of one embodiment of a demodulator 160 of wireless device 150. Demodulator 160 includes a cyclic prefix controller unit 1012, a Fourier transform unit 1014, a channel estimator 1016 and a detector 1018. The cyclic prefix controller unit 1012 removes the cyclic prefix from each received OFDM symbol and provides a sequence of N input samples {x (n)} for the received OFDM symbol. The Fourier transform unit 1014 performs a partial Fourier transform on the input sample sequence {x (n)} for each selected interlace m and performs a set of S received symbols {X _m (k)} for the interlace. (Where m = 1.. M). Channel estimator 1016 estimates the channel gain for each selected interlace m based on the input sample sequence {x (n)}.

Acquire. Detector 1018 estimates channel gain for each selected interlace

Performs detection (eg, equalization or matching filtering) on the set of S received symbols {X _m (k)} for each selected interlace using S detected data symbols with the interlace

To provide.

10B shows a block diagram of one embodiment of an RX data processor 170 of wireless device 150. Multiplexer 1030 receives detected data symbols for all interlaces from detector 1018, performs multiplexing of detected data and overhead symbols during each symbol period based on MUX_RX control, and each of interest. Provide a detected data symbol stream of the RX data stream processor 1040 and a detected overhead symbol stream to the RX overhead data processor 1060.

Within each RX data stream processor 1040, subband-to-symbol demapping unit 1042 maps the received symbol on each subband of the selected interlace to the appropriate location in the slot. Interlace-to-slot demapping unit 1044 maps to each selected interlace and the appropriate slot. The symbol-to-bit demapping unit 1046 maps the received symbols for each slot with code bits. Descrambler 1048 descrambles the code bits for each slot and provides descrambled data. Slot buffer 1050 buffers one or more slots of descrambled data, performs reassembly of packets as needed, and provides descrambled packets. Deinterleaver 1052 deinterleaves each descrambled packet and provides a deinterleaved packet. The decoder 1054 decodes the deinterleaved packets and provides the decoded data packets to the data stream {d _i }. In general, the processing performed by units within RX data stream processor 1040 is complementary to the processing performed by corresponding units within TX data stream processor 910 of FIG. 9A. Symbol-to-bit demapping and decoding are performed depending on the mode used for the data stream. The RX overhead data processor 1060 processes the received overhead symbols and provides decoded overhead data.

Due to the periodic structure of the M interlaces, the Fourier transform unit 1014 determines the partial S 'for the interlace to obtain a set of S received symbols {X _m (k)} for each selected interlace m. Point Fourier transform can be performed. The Fourier transform for S 'subbands containing all S subbands of interlace m (where m = 1.. M) can be expressed as follows:

이며, N=MㆍS'이다. 다음의 항들은 다음과 같이 정의될 수 있다:Where x (n) is the input sample for sample period n,

And N = M · S '. The following terms may be defined as follows:

은

에 의해 입력 샘플 x(n)을 회전시킴으로써 획득된 회전된 샘플이며,

은 샘플마다 가변하는 페이저이다(m-1과 n-1에 대한 지수에 있는 -1은 0 대신에 1에서 시작하는 인덱스 넘버링 방식에 의한 것이다); 그리고 g_m(n)은 S' 샘플들만큼 떨어져 있는 M개의 회전된 샘플들을 누적시킴으로써 획득되는 시간-도메인 값이다. here,

silver

Is a rotated sample obtained by rotating the input sample x (n) by

Is a sampler that varies from sample to sample (-1 in the exponent for m-1 and n-1 is by index numbering, starting at 1 instead of 0); And g _m (n) is a time-domain value obtained by accumulating M rotated samples that are separated by S ′ samples.

Equation (1) can be expressed as follows:

에 의해 회전되어 N개의 회전된 샘플들의 시퀀스

을 획득한다. 그 후에 회전된 샘플들은 수학식 (3)에 제시된 바와 같이 S'개의 시간-도메인 값들 {g_m(n)}을 획득하기 위해, M개의 회전된 샘플들의 S'개의 세트들에서 누적된다. 각각의 세트는 시퀀스

에서 S'번째마다 회전된 샘플을 포함하며, S'개의 세트들은 시퀀스

에 있는 상이한 스타팅 회전 샘플들과 관련되어 있다. 그 후에 보통의 S'-포인트 푸리에 변환이 S'개의 시간 도메인 값들 {g_m(n)}을 통해 수행되어 인터레이스 m에 대한 S'개의 수신된 심볼들을 획득한다. S개의 사용가능한 서브밴드들에 대한 수신된 심볼들은 유지되며, S'-S개의 사용되지 않는 서브밴드들에 대한 수신된 심볼들은 버려진다. The partial S'-point Fourier transform for interlace m may be performed as follows. Each of the N input samples in the sequence {x (n)} for one symbol period is initially shown in equation (2).

Sequence of N rotated samples rotated by

Acquire. The rotated samples are then accumulated in the S 'sets of M rotated samples to obtain S' time-domain values {g _m (n)} as shown in equation (3). Each set is a sequence

Contains samples rotated every S'ths, and S 'sets are sequence

It relates to different starting rotational samples in. A normal S'-point Fourier transform is then performed through S 'time domain values {g _m (n)} to obtain S' received symbols for interlace m. Received symbols for S usable subbands are retained and received symbols for S'-S unused subbands are discarded.

을 획득하기 위해 제거된다:For channel estimation, the partial S'-point Fourier transform is an interlace p used for the FDM pilot to obtain a set of S received pilot symbols, {X _p (k)} or X (M · k + p). Can be performed over N input samples for. The modulation on the received pilot symbols is then channel gain estimates for the subbands of interlace p as follows.

Is removed to obtain:

을 통해 수행되며, {h_p(n)}은 다음과 같이 표현될 수 있다:

(여기서, n=1 . . . S'). 시퀀스 {h_p(n)}에 있는 채널 이득 값들은 그 후에 S'개의 디로테이트된(derotated) 시간-도메인 채널 이득 값들의 시퀀스

(여기서, n=1 . . . S')을 획득하기 위해

과의 곱셈에 의해 디로테이트된다. Where P (M.k + p) is a known pilot symbol for the kth subband of interlace p, and " * " represents a conjugate complex number. Equation (5) assumes that all S 'subbands are used for pilot transmission. The S'-point IFFT then performs channel gain estimates to obtain a sequence of S 'modulated time-domain channel gain values {h _p (n)}.

{H _p (n)} can be expressed as:

Where n = 1.. S '. The channel gain values in the sequence {h _p (n)} are then followed by a sequence of S 'derotated time-domain channel gain values.

(Where n = 1... S ') to obtain

Derotate by multiplication with

The channel gain estimates for the subbands of interlace m can be expressed as follows:

를 획득하기 위해 처음에 시퀀스 {h(n)}에 있는 각각의 디로테이트된 시간-도메인 채널 이득 값을

과 곱함으로써 획득될 수 있다. 그 후에 보통의 S'-포인트 FFT는 인터레이스 m의 서브밴드들에 대한 S'개의 채널 이득 추정들을 획득하기 위해 시퀀스

에 대하여 수행된다.

에 의한 h_p(n)의 디로테이션과

에 의한 h(n)의 로테이션은 결합될 수 있으며, 그 결과 인터레이스 m에 대한 회전된 채널 이득 값들은

(여기서, n=1. . . S')로서 획득될 수 있다. As shown in Equation 6, the channel gain estimates for the subbands of interlace m are a sequence of S 'rotated channel gain values.

Each derotated time-domain channel gain value in the sequence {h (n)} is initially derived to obtain

Can be obtained by multiplying by The normal S'-point FFT is then sequenced to obtain S 'channel gain estimates for the subbands of interlace m.

Is performed against.

Derotation of h _p (n) by

The rotation of h (n) by can be combined so that the rotated channel gain values for interlace m

(Where n = 1... S ').

An exemplary channel estimation scheme has been described above. Channel estimation may also be performed in other ways. For example, channel estimates obtained for the different interlaces used for pilot transmission may be filtered (eg, over time) and / or to make a more accurate channel estimate for each interlace of interest. Or post-processed (eg, based on the least squares estimate of the impulse response {h (n)}).

The multiplexing techniques described herein may be implemented by various means. For example, these techniques may be implemented by hardware, software, or a combination thereof. In a hardware implementation, the processing units used to perform multiplexing at the base station may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), and programmable logic (PLDs). devices), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. Can be. Processing units used to perform complementary processing in the wireless device may also be implemented by one or more ASICs, DSPs, and the like.

In a software implementation, multiplexing techniques may be implemented within modules (eg, procedures, functions, etc.) that perform the functions described herein. The software codes may be stored in a memory unit (eg, memory unit 142 or 182 of FIG. 1) and executed by a processor (eg, controller 140 or 180). The memory unit may be implemented within the processor or external to the processor. When the memory unit is implemented outside the processor, the memory unit may be communicatively connected to the processor through various means known in the art.

The previous description of the presented embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the present invention. Thus, the present invention should not be limited to the embodiments set forth herein but should be construed in the broadest scope consistent with the principles and novel features set forth herein.

Claims (47)

A method for transmitting data in a wireless multi-carrier communication system, the method comprising: Assigning slots to each of the plurality of data symbol streams, each slot being a unit of transmission and the plurality of slots are frequency division multiplexed in each symbol period; Multiplexing the data symbols of each data symbol stream into the slots assigned to the data symbol stream; And Forming a composite symbol stream using multiplexed data symbols for the plurality of data symbol streams, the plurality of data symbol streams being independently recoverable by a receiver. The method of claim 1, Forming a plurality of non-overlapping interlaces using U frequency subbands usable for transmission—U &lt; 1 &gt; and each interlace of selected frequency subbands from among the U frequency subbands. Different set; And And mapping the plurality of slots to the plurality of interlaces in each symbol period. The method of claim 1, Forming 2 ^N non-overlapping interlaces using a plurality of frequency subbands usable for transmission—N> = 1 and each interlace is a different set of frequency subbands selected from the plurality of frequency subbands -; And And mapping the plurality of slots into the 2 ^N interlaces in each symbol period. The method of claim 3, wherein N is 1, 2, 3 or 4. The method of claim 2, Forming the plurality of non-overlapping interlaces, Forming the plurality of interlaces using an equal number of frequency subbands. The method of claim 2, Forming the plurality of non-overlapping interlaces, Forming the plurality of interlaces using the frequency subbands of each interlace interlaced with the frequency subbands in each of the remaining interlaces. The method of claim 2, Forming the plurality of non-overlapping interlaces, Forming a plurality of frequency subband groups, each group including frequency subbands uniformly distributed across the T total frequency subbands in the system; And Forming each interlace using frequency subbands selected from each group of frequency subbands. The method of claim 2, Allocating the slots to each of the plurality of data symbol streams may include: Assigning each of the plurality of interlaces to one data symbol stream in each symbol period. The method of claim 2, The plurality of slots in each symbol period are identified by slot indices and the method includes: During each symbol period, further comprising mapping the slot indices to the plurality of interlaces based on any mapping scheme. The method of claim 9, The step of mapping the slot indexes to the plurality of interlaces, Mapping each slot index used for data transmission to different ones of the plurality of interlaces of different symbol periods. The method of claim 2, Distributing multiplexed data symbols to each assigned slot over frequency subbands of a slot mapped interlace. The method of claim 11, Distributing the multiplexed data symbols to each allocated slot, Distributing data symbols for each data packet transmitted to the slot on frequency subbands of a slot-mapped interlace. The method of claim 2, Selecting slots for pilot transmission among the plurality of slots in each symbol period; And And multiplexing pilot symbols into the slots used for pilot transmission. The method of claim 13, And mapping the slots used for pilot transmission to different interlaces in different symbol periods. The method of claim 13, The interlaces used for pilot transmission further comprise mapping the plurality of slots to the plurality of interlaces in each symbol period to have varying distances with respect to the interlaces used for data transmission. How to. The method of claim 9, Assigning at least one slot index for pilot transmission; And Allocating remaining slot indices for data transmission. The method of claim 16, Mapping the at least one slot index used for pilot transmission to at least one predetermined interlace; And And mapping each slot index used for data transmission to different interlaces in different symbol periods. The method of claim 1, Obtaining one data symbol stream for each data stream, and processing the plurality of data streams to obtain a plurality of data symbol streams. The method of claim 1, Allocating the slots to each of the plurality of data symbol streams may include: Allocating a specific number of slots to each data symbol stream based on at least one coding and modulation scheme and at least one packet size used for the data symbol stream. The method of claim 18, The processing of the plurality of data streams may include: Encoding data packets for each data stream in accordance with a coding scheme for generating coded packets for the data stream; And Modulating the coded packets for each data stream in accordance with a modulation scheme for generating data symbols for a corresponding data symbol stream. The method of claim 18, Encoding data packets for each data stream includes encoding integer number of data packets for each data stream in each frame of a predetermined time period, Allocating the slots to each of the plurality of data symbol streams comprises allocating an integer number of slots to each data symbol stream in each frame based on the number of data packets transmitted in the frame for the corresponding data stream. Method comprising a. The method of claim 1, Allocating the slots to each of the plurality of data symbol streams may include: Assigning each data symbol stream to a specific number of slots determined by decoding constraints and the coding and modulation scheme used for the data symbol stream. A device in a wireless multi-carrier communication system, A controller operative to assign slots to each of the plurality of data symbol streams, each slot being a unit of transmission and the plurality of slots are frequency division multiplexed in each symbol period; A data processor operative to multiplex the data symbols of each data symbol stream into the slots assigned to the data symbol stream and to form a composite symbol stream using the multiplexed data symbols for the plurality of data symbol streams-the And the plurality of data symbol streams is independently recoverable by a receiver. The method of claim 23, wherein The controller is further operative to form a plurality of non-overlapping interlaces using the U frequency subbands available for transmission and to map the plurality of slots to the plurality of interlaces in each symbol period, wherein U> 1. And each interlace is a different set of frequency subbands selected from among the U frequency subbands. The method of claim 24, In each symbol period the plurality of slots are identified by slot indices, and the data processor is further operable to map the slot indices to the plurality of interlaces based on any mapping scheme during each symbol period. Characterized in that the device. The method of claim 23, wherein The controller is further operable to select slots for pilot transmission among the plurality of slots in each symbol period, and the data processor is further operable to multiplex pilot symbols to the slots used for pilot transmission. Device. The method of claim 23, wherein And the controller is further operative to assign a specific number of slots to each data symbol stream based on at least one coding and modulation scheme and at least one packet size used for the data symbol stream. The method of claim 23, wherein And the data processor is further operative to obtain one data symbol stream for each data stream and process the plurality of data streams to obtain a plurality of data symbol streams. The method of claim 23, wherein And wherein said wireless multi-carrier communication system utilizes orthogonal frequency division multiplexing (OFDM). The method of claim 23, wherein And the wireless multi-carrier communication system is a broadcast system. A device in a wireless multi-carrier communication system, Means for assigning slots to each of the plurality of data symbol streams, each slot being a unit of transmission and the plurality of slots are frequency division multiplexed in each symbol period; Means for multiplexing the data symbols of each data symbol stream into the slots allocated to the data symbol stream; And Means for forming a composite symbol stream using multiplexed data symbols for the plurality of data symbol streams, wherein the plurality of data symbol streams are independently recoverable by a receiver. The method of claim 31, wherein Means for forming a plurality of non-overlapping interlaces using U frequency subbands usable for transmission, where U> 1 and each interlace is a different set of frequency subbands selected from the U frequency subbands ; And And means for mapping the plurality of slots to the plurality of interlaces in each symbol period. The method of claim 32, In each symbol period the plurality of slots are identified by slot indices, and the apparatus further comprises means for mapping the slot indices to the plurality of interlaces for each symbol period based on any mapping scheme. Apparatus comprising a. The method of claim 31, wherein Means for selecting slots for pilot transmission among the plurality of slots in each symbol period; And And means for multiplexing pilot symbols into the slots used for pilot transmission. The method of claim 31, wherein Means for obtaining one data symbol stream for each data stream and processing the plurality of data streams to obtain a plurality of data symbol streams. A method of receiving data in a wireless multi-carrier communication system, the method comprising: Selecting at least one data stream for recovery from the plurality of data streams transmitted by the transmitter in the system; Determining slots used for each selected data stream, wherein each slot is a unit of transmission and the plurality of slots are frequency division multiplexed in each symbol period and the data symbols for each of the plurality of data streams are Multiplexed into slots allocated to a data stream, wherein the plurality of data streams are independently recoverable by a receiver; Multiplexing the detected data symbols obtained for the slots used for each selected data stream into the detected data symbol streams, wherein each detected data symbol is an estimate of the data symbol and at least one detected data symbol stream is Obtained for the at least one data stream selected for reconstruction; And Processing each detected data symbol stream to obtain a corresponding decoded data stream. 36. The method of claim 35 wherein Mapping the plurality of slots of each symbol period to a plurality of non-overlapping interlaces formed over U frequency subbands usable for transmission, wherein U> 1 and each interlace is the U frequency subbands. A different set of frequency subbands selected from among the bands. The method of claim 37, The plurality of slots in each symbol period are identified by slot indices, and the mapping of the plurality of slots in each symbol period is based on any mapping scheme and the slot indices in the plurality of slots in each symbol period. And mapping to interlaces of the. The method of claim 36, Performing a partial Fourier transform on each slot used for each selected data stream to obtain received data symbols for the slot, wherein the partial Fourier transform is less than all frequency subbands of the system. Fourier transform for small subbands; And And performing detection on the received data symbols for each slot used for each selected data stream to obtain detected symbols for the slot. The method of claim 36, And performing a partial Fourier transform for each slot used for pilot transmission to obtain a channel estimate for the slot. The method of claim 40, Obtaining a channel estimate for each slot used for each selected data stream based on channel estimates obtained from the slots used for pilot transmission. A device in a wireless multi-carrier communication system, A controller operable to select at least one data stream for recovery from the plurality of data streams transmitted by the transmitter in the system and to determine the slots used for each selected data stream—each slot being a unit of transmission A plurality of slots are frequency division multiplexed in each symbol period, data symbols for each of the plurality of data streams are multiplexed into slots allocated to the data stream, and the plurality of data streams are independently independent by a receiver. Recoverable; And Data operative to multiplex the detected data symbols obtained for the slots used for each selected data stream into the detected data symbol stream and process each detected data symbol stream to obtain a corresponding decoded data stream. A processor, wherein each detected data symbol is an estimate of a data symbol and at least one detected data symbol stream is obtained for the at least one data stream selected for reconstruction. The method of claim 42, The controller is further operative to map the plurality of slots of each symbol period to a plurality of non-overlapping interlaces formed over the U frequency subbands available for transmission, where U> 1 and each interlace And a different set of frequency subbands selected from among frequency subbands. The method of claim 42, Perform a partial Fourier transform on each slot used for each selected data streams to obtain received data symbols for the slot and each selected data stream to obtain detected symbols for the slot And a demodulator operative to perform detection on the received data symbols for each slot used for the purpose. A device in a wireless multi-carrier communication system, Means for selecting at least one data stream for restoration among a plurality of data streams transmitted by a transmitter in the system; Means for determining the slots used for each selected data stream, wherein each slot is a unit of transmission and the plurality of slots are frequency division multiplexed in each symbol period and the data symbols for each of the plurality of data streams Multiplexed into slots allocated to the data stream, wherein the plurality of data streams are independently recoverable by a receiver; Means for multiplexing the detected data symbols obtained for the slots used for each selected data stream into the detected data symbol stream, wherein each detected data symbol is an estimate of the data symbol and at least one detected data symbol stream. Is obtained for the at least one data stream selected for reconstruction; And Means for processing each detected data symbol stream to obtain a corresponding decoded data stream. The method of claim 45, Means for mapping the plurality of slots of each symbol period to a plurality of non-overlapping interlaces formed over the U frequency subbands usable for transmission, wherein U> 1 and each interlace is U And a different set of frequency subbands selected from among two frequency subbands. The method of claim 45, Means for performing partial Fourier transform on each slot used for each selected data streams to obtain received data symbols for the slot; And And means for performing detection on the received data symbols for each slot used for each selected data streams to obtain detected symbols for the slot.

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