JP2007509586A - Frequency division multiplexing of multiple data streams in a multi-carrier communication system - Google Patents

Abstract

Frequency division multiplexing of a plurality of data streams in a multi-carrier communication system United States Patent Application 20070274735 Kind Code: A1 A plurality of data using frequency division multiplexing (FDM) in an OFDM system is formed of U usable subbands. . Each interlace is a different set of S subbands, and each interlace subband is combined with each subband of the other interlace. M slots are defined for each symbol period, and 1 to M slot indexes can be assigned. (1) frequency diversity is achieved for each slot index, and (2) the interlace used for pilot transmission has a variable distance to the interlace used for each slot index, and the channel Slot indexes can be mapped to interlaces to improve estimation performance. Each data stream can be processed as a fixed size data packet, and a different number of slots for each data packet can be used depending on the encoding and modulation scheme used for the data packet. .
[Selection] FIG. 9A

Description

  This application was filed on September 1, 2004, and “A Method for Multiplexing and Transmitting Multiple Multimedia Streams to Mobile Terminals over Terrestrial Radio”. ")", Serial number 10 / 932,586, filed on April 5, 2004, "Multiplexing and transmission of multiple data streams in a wireless multi-carrier communication system". US Provisional Patent Application Serial Number 60 / 559,740 entitled “Transmission of Multiple Data Streams in a Wireless Multi-Carrier Communication System” and filed on October 24, 2003, Frequency Division Multiplexing Method of Various Multimedia Streams for Multicast Wireless Transmission ”(“ A Method f or US Patent No. 60 / 514,315, entitled "or frequency-Division Multiplex Various Multimedia Streams for Multicast Wireless Transmission to Mobile Devices").

(Field)
The present invention relates generally to communication, and more specifically to techniques for multiplexing multiple data steams in a wireless multi-carrier communication system.

  A multi-carrier communication system utilizes multiple carriers for data transmission. These multiple carriers can be provided by orthogonal frequency division multiplexing (OFDM), some other multi-carrier modulation technique, 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 or frequency channels. With OFDM, each subband is associated with a respective subcarrier that may be modulated with data.

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

  Multiplexing multiple data streams for simultaneous transmission challenges whether these streams are actually variable (eg, have a data rate and / or coding and modulation scheme that varies over time). Maybe be challenge. In one simple multiplexing scheme, multiple data streams are assigned different time slots or symbol periods using time division multiplexing (TDM). Because of this TDM scheme, only one data stream is sent at any time and this data stream uses all the subbands available for data transmission. This TDM scheme has certain undesirable characteristics. First, the amount of data that can be sent to the smallest time unit that can be allocated to a given data stream can be considered as "granularity" for the data stream, but is used for the data stream. Depending on the coding and modulation schemes. Different encoding and modulation schemes may then be associated with different granularities, which may complicate the allocation of resources to the data stream and may result in inefficient resource utilization. Absent. Second, if the granularity for a given encoding and modulation scheme is too large compared to the decoding capability of the wireless device, then a large input buffer is required at the wireless device that stores the received symbols. May be.

  Therefore, there is a technical need for a technique for efficiently multiplexing a plurality of data streams in a multi-carrier communication system.

[wrap up]

  Techniques for multiplexing multiple data streams using frequency division multiplexing (FDM) in a wireless multi-carrier (eg, OFDM) communication system are described herein. In one embodiment, M disjoint or non-overlapping “interlaces” are formed of U subbands that can be used for transmission. Note that M> 1 and U> 1. Interlaces do not overlap in that each usable subband is contained within only one interlace. Each interlace is a different set of S subbands, where U = MS. The S subbands in each interlace are uniformly distributed across the N total subbands and are evenly spaced apart by the M subbands. N = M · S ′ and S ′ ≧ S. This interlaced subband configuration provides frequency diversity and can simplify processing at the receiver. For example, the receiver may use a “partial” S′-point fast Fourier transform (for each interlace of interest (instead of a full N-point fast Fourier transform (FET)) (FET). "Partial" S'-point fast Fourier transform) (FET). M interlace can 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 in each symbol period. Can be sent.

  In one embodiment, the multiple data streams are assigned “slots”, and each slot is a unit of transmission, which may be equal to one interlace in one symbol period. M slots are then available in each symbol period, and M can be assigned from slot indices 1 to M. Each slot index can be mapped to one interlace in each symbol period based on a slot-to-interlace mapping scheme. One or more slot indexes can be used for FDM pilots, and the remaining slot indexes can be used for data transmission. The slot-to-interlace mapping may be such that the interlace used for pilot transmission has variable distances to the interlace used for each slot index in different OFDM symbol periods. This allows all slot indexes used for data transmission to achieve similar channel estimation performance.

  Each data stream can be processed as a fixed size data packet. In this case, a different number of slots may be used for each data packet depending on the coding and modulation scheme used for the data packet. Alternatively, each data stream can be processed as variable size data packets. For example, the packet size can be selected such that an integer number of data packets is sent in each slot. In any case, if multiple data packets are sent in a given slot, then the data symbols of each data packet are all sub-data used for the slot. Since it can be distributed across the band, frequency diversity is achieved for each data packet sent in the slot.

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

[Detailed description]
The features and nature of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the accompanying drawings in which like reference characters identify correspondingly throughout.

  The term “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

  The multiplexing techniques described herein can be used for various wireless multi-carrier communication systems. These techniques can also be used for the downlink as well as the uplink. The downlink (or forward link) refers to the communication link from the base station to the wireless device, and the uplink (or reverse link) refers to the communication link from the wireless device to the base station. Point to. For ease of understanding, these techniques are described below for the downlink in OFDM based systems.

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

  At base station 110, TX data processor 120 receives multiple (T) data streams (or “traffic” data) and processes each data stream to generate data symbols (eg, Encodes, interleaves, and symbol maps). As used herein, a “data symbol” is a modulation symbol for traffic data, and a “pilot symbol” is a modulation symbol for pilot (that is, a base station and a wireless device). The modulation symbol is a complex value (a for points) in a signal group for a modulation scheme (eg, M-PSK, M-QAM, etc.). complex value). TX data processor 120 also multiplexes the data symbols for the T data stream and pilot symbols onto the appropriate subbands to provide a composite symbol stream. Modulator 130 performs OFDM modulation on the multiplexed symbols on the multiplexed symbols in the combined symbol stream to generate OFDM symbols. A transmitter unit (TMTR) 132 converts the OFDM symbols to analog signals and further adjusts (eg, amplifies, filters, and upconverts the analog signal to produce a modulated signal) (frequency upconverts)). Base station 110 then transmits the modulated signal from antenna 134 to wireless devices in the system.

  In the wireless device 150, the transmitted signal from the base station 110 is received by the antenna 152 and supplied to the receiver unit (RCVR) 154. The receiver unit 154 conditions the received signal (eg, filters, amplifies, and frequency downconverts) and converts the modulated signal to produce a stream of input samples. Digitize. To obtain received symbols for one or more data streams of interest, the demodulator 160 performs OFDM demodulation on the input samples and further transmits the data sent by the base station 110. Detection (eg, equalization or matched filtering) with respect to received symbols to obtain detected data symbols, which are symbol estimates. To do. RX data processor 170 then processes (eg, symbol demaps, deinterleaves, and decodes) the detected data symbols for each selected data stream, and Supply decoded data for the stream. The processing by demodulator 160 and RX data processor 170 is complementary to the processing by modulator 130 and TX data processor 120 at base station 110, respectively.

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

  Base station 110 may transmit T data streams for various services such as broadcast, multicast, and / or unicast. A broadcast transmission is sent to all wireless devices within a specified service area, a multicast transmission is sent to a group of wireless devices, and a unicast transmission is Sent to a specific wireless device. For example, the base station 110 can broadcast many data streams for multimedia (eg, television) programs and for multimedia content such as video, audio, teletext, data, video / audio clips, etc. . A single multimedia program can be broadcast as three separate data streams for video, audio, and data. This allows independent reception of the video, audio and data portions of the multimedia program by the wireless device.

  FIG. 2 shows an exemplary super-frame structure 200 that can be used for system 100. The T data stream can be transmitted in a superframe, and each superframe has a predetermined time duration. A superframe can also be referred to as a frame, a time slot, or some other terminology. For the embodiment shown in FIG. 2, each superframe 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 stream (eg, the encoding and modulation scheme used for each data stream, the specific location of each data stream within the superframe, etc.) I can do it. The T data stream is sent in field 216. Although not shown in FIG. 2, each superframe can be divided into multiple (eg, 4) same-sized frames to facilitate data transmission. Other frame structures can also be used for the system 100.

  FIG. 3 shows a combined an interlaced subband structure that can be used for the system 100. System 100 utilizes an OFDM structure having N total subbands. U subbands can be used for data and pilot transmissions 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. As an example, system 100 can utilize an OFDM structure with N = 4096 total subbands, U = 4000 usable subbands, and G = 96 guard subbands.

  The U usable subbands can be arranged into M interlaces or disjoint subband sets. M interlaces are disjoint or non-overlapping in that each of the U usable subbands belongs to only one interlace. Each interlace contains S usable subbands, where U = M · S. In different groups of S ′ = N / M subbands that are uniformly distributed across the N total subbands, such that consecutive subbands in the group are spaded apart by M subbands, Each interlace is associated. For example, group 1 includes subbands 1, M + 1, 2M + 1, etc., group 2 includes subbands 2, M + 2, 2M + 2, etc., and group M includes subbands M, 2M, 3M, etc. I can do it. For each group, the S subbands of S 'are usable subbands, and the remaining S'-S subbands are guard subbands. Each interlace can then include S usable subbands in the group associated with each interlace. For the exemplary OFDM structure described above, M = 8 interlaces can be formed, each interlace being equally spaced with M = 8 subbands, S ′ = 512 subbands. S = 500 usable subbands selected from the band are included. The S usable subbands in each interlace are thus interlaced with the S usable subbands in each of the other M-1 interlaces.

  In general, the system can utilize any OFDM structure with any number of total subbands, usable subbands, and guard subbands. Any number of interlaces can also be formed. Each interlace may include any one of any number of usable subbands and U usable subbands. For simplicity, the following description is for the combined subband configuration shown in FIG. 3, comprising M interlaces, each containing an S usable subband with a uniform distribution. Is against. This combined subband structure offers several advantages. First, frequency diversity is achieved because each interlace contains usable subbands derived from within the overall system bandwidth. Second, by performing a partial S′-point FET instead of a full N-point FET, the wireless device can recover the data / pilot symbols sent on a given interlace and processed by the wireless device Can be simplified.

  Base station 110 may transmit FCM pilots on one or more interlaces to allow the wireless device to perform various functions, such as channel estimation, frequency tracking, time tracking, and the like.

  FIG. 4A shows a data and pilot transmission scheme 400 with “staggered” FDM pilots. In this example, M = 8, one interlace is used for the FDM pilot in each symbol period, and the remaining seven interlaces are used for traffic data. Pilot symbols are sent on one interlace (eg, interlace 3) in odd-numbered symbol periods and on another interlace (eg, interlace 7) in even-numbered symbol periods, In an alternating manner, FDM pilots are sent on two designated interlaces. The two interlaces used for the FDM pilot are staggered or offset with M / 2 = 4 interlaces. This staggered arrangement allows the wireless device to observe the channel response for more subbands and can improve performance.

  FIG. 4B shows a data and pilot transmission scheme 410 with “cycled” FDM pilots. In this example, M = 8, one interlace is used for the FDM pilot in each symbol period, and the remaining seven interlaces are used for traffic data. FDM pilots are sent on all 8 interlaces in a cycled manner, such that the pilot symbols are sent on different interlaces during each M-symbol period duration. It is done. For example, the FDM pilot may be on interlace 1 in symbol period 1, then on interlace 5 in symbol period 2, then on interlace 2 in symbol period 3, and so on, and in symbol period 8 Can be sent on interlace 8, then back to interlace 1 in symbol period 9, and so on. This cycling allows the wireless device to watch the channel response for all available subbands.

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

  The base station 110 can transmit the T data stream on the M interlace in various ways. In the first embodiment, each data stream is sent on the same one or more interlaces in each symbol period in which the data stream is sent. For this embodiment, interlaces are statically assigned to each data stream. In a second embodiment, each data stream can be sent on a different interlace in different symbol periods in which the data stream is sent. For this embodiment, interlace is dynamically assigned to each data stream to improve frequency diversity and that the quality of the channel estimate is independent of the slot index or index assigned to the data stream. You can be sure. The second embodiment can also be seen as a form of frequency hopping and will be described in more detail below.

  In order to average channel estimation and detection performance for all T data streams, a transmission scheme 410 is used for the first embodiment with statically assigned interlaces. The transmission scheme 400 or 410 can be used for the second embodiment with dynamically assigned interlaces. If FDM pilot is sent on the same interlace (called pilot interlace) in each symbol period and is used to obtain channel estimates for all M interlaces, then Sometimes an interlace channel estimate closer to the pilot interlace is generally better than an interlace channel estimate further away from the pilot interlace. The detection performance for the data stream can be degraded if the stream is always assigned an interlace far away from the pilot interlace. Assigning interlaces with a varying distance (or spacing or offset) to the pilot interlace can avoid this performance degradation due to channel estimation bias.

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

In the first slot-to-interlace mapping scheme, slot indexes are mapped to interlaces in an in a permutated manner. For a transmission scheme 400 with M = 8 and 1 pilot slot and 7 data slots in each symbol period, the mapping is performed as follows. Eight interlaces can be represented by the original sequence {I _1, I _2, I _3, I _4, I _5, I _6, I _7, I ₈ }. The rearranged sequence is formed as {I _1, I _5, I _3, I _7, I _2, I _6, I _4, I ₈ }. The i th interlace in the original sequence is placed at the i _br th position in the rearranged sequence, where i ∈ {1... 8}, i _br ∈ {1. In addition, (i _br -1) is an abit-reverse index of (i-1). Since these indexes start from 1 instead of 0 _, an offset of −1 is used for i and i _br . As an example, for i = 7, (i−1) = 6, the bit representation is “110”, the inverse bit index is “011”, (i _br −1) = 3, i _br = 4 is there. The seventh interlace in the original sequence is placed in the fourth position in the interlaces thus rearranged. The two interlaces used for the FDM pilot then form a shortened interlace sequence {I _1, I _5, I _3/7, I _2, I _6, I _4, I ₈ } Combined in the sorted sequence. The kth slot index (or kth data slot index) used for data transmission is (k−1) th in the shortened interlace sequence for kε {2... To be interlaced. For each subsequent symbol period, the shortened interlace sequence is cyclically shifted to the right by two positions and folded back to the left. The kth data slot index is again mapped to the (k-1) th interlace in the cyclically shifted shortened interlace sequence.

FIG. 5 shows the mapping of slot indexes to interlaces for the first mapping scheme described above. Slot index 1 used for the FDM pilot is mapped to interlaces 3 and 7 on the alternating symbol periods for transmission scheme 400. Data slot indices 2-8 interlaced race sequence first symbol period, which is shortened to seven interlaces in _{{I 1, I 5, I} 3/7, I 2, I 6, I 4, I 8} The second symbol period is mapped to a cyclically or cyclically shifted interlace sequence {I _4, I _8, I _1, I _5, I _3/7, I _2, I ₆ }, etc. . As shown in FIG. 5, each data slot index is divided into seven different interlaces in seven consecutive symbol periods, where one of the seven interlaces is interlace 3 or 7. To be mapped. All seven data slot indexes then achieve similar performance.

In the second slot-to-interlace mapping scheme, slot indices are mapped to interlaces in a pseudo-random manner. A pseudo-random number (PN) generator can be used to generate the PN number used to map the slot index to the interlace. The PN generator can be implemented with a particular generator polynomial, eg, a linear feedback shift register (LFSR) that implements g (x) = x ¹⁵ + x ¹⁴ +1. For each symbol period j, the LFSR is updated and the V least significant bits (LSBs) of the LFSR can be expressed as PN (j), where j = 1, 2,. = Log ₂ M. The kth data slot index is mapped to interlace [(PN (j) + k) mod M] +1 for k∈ {2... 8} if this interlace is not used for FDM pilot. Otherwise, it is mapped to interlace [(PN (j) + k + 1) mod M] +1.

  In the third slot-to-interlace mapping scheme, slot indexes are mapped to interlaces in a cyclic manner. For each symbol period j, the kth data slot index is for kε {2... M}, if this interlace is not used for FDM pilots, the interlace [(j + k) mod M] +1 Otherwise mapped to interlace [(j + k + 1) mod M] +1.

  The M slot index can thus be mapped to M interlaces in various ways. Several exemplary slot interlace mapping schemes have been described above. Other mapping schemes can also be used and are within the scope of the present invention.

  Slots can be assigned to the T data stream in various ways. In the first slot allocation scheme, each data stream carries a non-negative integer number of data packets (ie, zero or more data packets), so a sufficient number of slots in each superframe are allocated. . Because of this scheme, data packets can be defined to have a fixed size (eg, a predetermined number of information bits), making it simple to encode and decode for data packets. Can be Each fixed size data packet can be encoded and modulated in order to generate an encoded packet having a variable size depending on the encoding and modulation scheme used for the packet. The number of slots required to transmit the encoded packet then depends on the encoding and modulation scheme used for the packet.

  In the second slot assignment scheme, each data stream can be assigned a non-negative integer number of slots in each superframe, and an integer number of data packets is sent in each assigned slot. Can be done. The same encoding and modulation scheme can be used for all data packets sent in any slot. Each data packet may have a size that depends on (1) the number of data packets sent in the slot, and (2) the coding and modulation scheme used for that slot. Because of this scheme, data packets can have a variable size.

  Slots can also be assigned to data streams in other ways. For ease of understanding, the following description assumes that the first slot allocation scheme is used by the system.

  Each data stream can be encoded in various ways. In one embodiment, each data stream is encoded with a 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 convolutional code, or some other code.

FIG. 6 shows an exemplary outer coding scheme that uses a 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 the data stream are written in one row per memory row. After the K _rs data packet is written to the K _rs row, block coding is performed column-wise, one column at a time. In one embodiment, each column contains K _rs bytes (1 byte per row) and (N _rs , K _rs ) reads to generate a corresponding codeword containing N _rs bytes. Encoded with Solomon code. The first K _rs bytes of the codeword are data bytes (these are also called systematic bytes) and the last N _rs -K _rs bytes are parity bytes (these are used by the wireless device for error correction) Is possible). Reed-Solomon encoding generates N _rs -K _rs parity bytes for each codeword, which are written in the N _rs -K _rs to N _rs lines of memory after the K _rs lines of data. . The RS block includes K _rs rows of data and N _rs -K _rs rows of parity. In one embodiment, N = 16 and K _rs are configurable parameters, eg, K _rs ε {12, 14, 16}. The Reed-Solomon code is disabled when K _rs = N _rs . The data / parity packet (or each row) of the RS block is then encoded with a turbo inner code to generate a corresponding encoded packet. Code block contains Nrs coded packets for Nrs rows of the RS block (N _rs coded packets).

  The Nrs encoded packet of each code block can be sent in various ways. For example, each code block can be transmitted in one superframe. Each superframe can be divided into multiple (eg, 4) frames. Each code block can then be divided into multiple (eg, 4) sub-blocks, and each sub-block of the code block can be sent in one frame of the superframe. Transmission of each code block in multiple parts throughout the superframe can provide time diversity.

  Each data stream can be transmitted with or without hierarchical coding, where the term “encoding” in this context refers to channel rather than data coding at the transmitter. Refers to encoding. A data stream can be composed of two substreams, which are referred to as a base stream and an enhancement stream. The base stream can carry basic information and can be sent to all wireless devices in the coverage area of the base station. The enhancement stream can carry further information and can be sent to a wireless device that watches for better channel conditions. Using hierarchical coding, the base stream is encoded and modulated to generate a first modulation symbol stream, and the enhancement stream is encoded and modulated to generate a second modulation symbol stream. Is done. The same or different coding and modulation schemes can be used for the base stream and the enhancement stream. The two modulation symbol streams can then be 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 8 modes are given indices from 1 to 8. Each mode is associated with a specific modulation scheme (eg, QPSK or 16-QAM) and a specific inner code rate (eg, 1/3, 1/2, or 2/3). The first five modes are for “regular” coding with only the base stream, and the last three modes are for hierarchical coding with base and enhancement streams. For simplicity, the same modulation scheme and inner code rate are used for both base and enhancement streams for each hierarchical coding mode.

  The fourth column of Table 1 shows the number of slots required to transmit one fixed size data packet for each mode. Table 1 assumes S usable subbands per slot and a data packet size of 2-S information bits and S usable subbands per slot (eg, S = 500). A slot is mapped to one interlace with S usable subbands, and each subband can carry one data symbol, so each slot has a capacity of S data symbols. For mode 1, a data packet with 2 · S information bits is encoded with a rate 1/3 inner code to generate 6 · S code bits, which are then QPSK. Maps to the 3 · S data symbol to be used. The 3 · S data symbols for the data packet can be sent in three slots, each slot carrying an S data symbol. Similar processing can be performed for each of the other modes in Table 1.

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

  FIG. 7A shows the transmission of the smallest integer number of data packets using one slot in each of the integer number of symbol periods for each of the first five modes listed in Table 1. Indicates. One data packet is (1) 3 symbol periods for mode 1, (2) 2 symbol periods for mode 2 and (3) 1 symbol period for mode 4 It can be sent using one slot. Two data packets can be sent using 3 slots for 3 symbols since each data packet takes 1.5 slots for mode 3. Four data packets can be sent using one slot during a three symbol period because for mode 5 each data packet takes 0.75 slots to send.

  FIG. 7B shows the transmission of a minimum integer number of data packets using an integer number of slots in one symbol period for each of the first five modes listed in Table 1. One data packet uses (1) three slots for mode 1, (2) two slots for mode 2, and (3) one slot for mode 4 for one symbol period. Can be sent inside. Two data packets can be sent in one symbol period using 3 slots for mode 3. Four data packets can be sent in one symbol period using 3 slots for mode 5.

  As shown in FIGS. 7A and 7B, a minimum number of data packets can be transmitted in several ways for each mode (except mode 4). Transmitting the minimum number of data packets in a shorter period of time reduces the amount of ON time required to receive the data packets, but provides less time diversity. The reverse is true for transmitting a minimum number of data packets over a longer period of time.

  FIG. 8A shows the partitioning of a single encoded packet into three slots for mode 1. The three slots may be for three different interlaces in one symbol period, or may be for one interlace in three different symbol periods. Three slots can watch different channel conditions. Bits in the encoded packet can be interleaved (ie, reordered) prior to partitioning into three slots. Interleaving for each encoded packet can randomize the signal-to-noise ratio (SNR) of the bits throughout the encoded packet, which can improve coding performance. Interleaving can be performed in various ways, as is known in the art. Interleaving may also be such that adjacent bits in the encoded packet are not sent in the same data symbol.

  FIG. 8B shows the partitioning of four encoded packets into three slots for mode 5. As shown in FIG. 8B, the three slots can be successively filled with four encoded packets. If multiple encoded packets share a slot (eg, for modes 3 and 5), all bits sent in the slot are each encoded in the slot. The bits for the packet can be interleaved so that they are distributed across the subbands used for the slots. The interleaving across each slot provides frequency diversity for each encoded packet sent in the slot and can also improve decoding performance.

  Interleaving across slots can be done in various ways. In one embodiment, the bits for all encoded packets sent in a given slot are first mapped to data symbols and the data symbols are then reordered (in a permutated manner), mapped to the subband used for that slot. For the symbol-to-subband mapping, a first sequence with S'continuous values, 0 to S'-1, is first formed. A second sequence of S 'values is then created such that the i-th value of the second sequence is equal to the bit reverse of the i-th value of the first sequence. All values greater than or equal to S 'in the second sequence are removed to obtain a third sequence with S values ranging from 0 to S-1. To obtain a sequence of permuted S index values (S permutated index values) ranging from 1 to S, expressed as F (j), each value in the third sequence is then incremented by one. Clemented. The jth data symbol in the slot can be mapped to the F (j) th subband (F (j) -th subband) in the interlace used for the slot. For example, if S = 500 and S ′ = 512, then the first sequence is {0,1,2,3, ..., 510,511} and the second sequence is {0,256, 128, 384, ..., 255, 511}, and the third sequence is {0, 256, 128, 384, ..., 255}. The sequence F (j) only needs to be computed once and can be used for all slots. Other mapping schemes can also be used for symbol-to-subband mapping to achieve interleaving across each slot.

  In general, each data stream can carry any number of data packets in each superframe, depending on the data rate of the stream. Each data stream is allocated a sufficient number of slots in each superframe based on its data rate, depending on slot availability and possibly other factors. For example, each data stream may be constrained by a specified maximum number of slots in each symbol period, which may depend on the mode used for the data stream. Each data stream may be limited to a specified 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 determined by the decoding and buffering performance of the wireless device. Constraining each data stream within a maximum data rate ensures that the data stream can be recovered by a wireless device having defined decoding and buffering performance. The maximum data rate limits the number of data packets that can be transmitted in each symbol period for the data stream. The maximum number of slots can then be determined by the maximum number of data packets and the mode used for the data stream.

  In one embodiment, each data stream can be assigned an integer number of slots in a given symbol period, and multiple data streams do not share interlaces. For this embodiment, assuming that one slot is used for the FDM pilot, up to M-1 data streams can be sent on M-1 data slots in each symbol period. In another embodiment, multiple data streams can share interlaces.

FIG. 9A shows a block diagram of one embodiment of a TX transmission data processor at base station 110. TX data processor 120 includes T TX data stream processors 910a-910t for T data streams, a TX overhead data processor 930 for overhead / control data, a pilot processor 932 for TDM and FDM pilots, and a multiplexer (Mux) 940. . Each data stream processor 910 processes each data stream {d _i } to generate a corresponding data symbol stream {Y _i }, where iε {1... T}.

Within each TX data stream processor 910, an encoder 912 receives, encodes, and provides encoded packets for the data stream {d _i }. The encoder 912 performs encoding according to a concatenated code including, for example, a Reed-Solomon outer code and a turbo or convolutional inner code. In this case, as shown in FIG. 6, the encoder 912 encodes the K _rs data packet of each block to generate N _rs encoded packets. Encoding increases the reliability of transmission for the data stream. The encoder 912 can also generate and add a cyclic redundancy check (CRC) value for each encoded packet, which can be decoded by the wireless device for error detection (ie, the packet is correctly or incorrectly decoded). Can be used to determine if) The encoder 912 can also shuffle the encoded packets.

  Interleaver 914 receives the encoded packets from encoder 912 and interleaves the bits in each encoded packet to generate an interleaved packet. Interleaving provides time and / or frequency diversity for packets. The slot buffer 916 is then filled with interleaved packets for all slots assigned to the data stream, for example as shown in FIG. 8A or 8B.

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

  Bit to symbol mapping unit 920 receives the scrambled bits for each slot from scrambler 918 and modulates these bits according to the modulation scheme selected for the data stream (eg, QPSK or 16-QAM). And provide data symbols for the slot. Symbol mapping consists of (1) grouping a set of B bits to form B-bit binary values, where B ≧ 1, and (2) each B bit 2 This is accomplished by mapping the hex value to a complex value for a point in a signal constellation. The outer and inner 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 sent using hierarchical coding, then the base stream may be processed by a set of processing units 912-920 to generate a first stream of modulation symbols. The enhancement stream can also be processed by another set of processing units 912-920 to generate a second stream of modulation symbols (not shown in FIG. 9 for simplicity). . As shown in Table 1, the same encoding and modulation scheme may be used for both the base stream and the enhancement stream, or different encoding and modulation schemes may be used for the two streams. May be used. A 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 done in other ways. For example, scrambled bits for both the base stream and the enhancement stream can be provided to a single bit-to-symbol mapping unit that provides data symbols to the data stream.

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

TX overhead data processor 930 processes the overhead / control data according to the coding and modulation scheme used for overhead / control data and provides overhead symbols. A pilot processor 932 performs processing for TDM and FDM pilots and provides pilot symbols. Multiplexer 940 provides mapped data symbols for the T data stream from TX data stream processors 910a-910t, overhead symbols from overhead data processor 930, pilot symbols from pilot processor 932, and guard symbols. receive. Multiplexer 940 provides onto the proper subbands and symbol periods, data symbols, overhead symbols, pilot symbols and guard symbols based on MUX_TX from controller 140, and a combined symbol stream, { Y _c } is output.

FIG. 9B shows a block diagram of an embodiment of modulator 130 at base station 110. Modulator 130 includes an inverse fast Fourier transform (IFFT) unit 950 and a cyclic prefix generator 952. In each symbol period, the IFFT unit 950 determines the N symbols for the N total subbands in order to obtain “transformed” symbols containing N time-domain samples. the N total subbands) is converted to the time domain with an N-point IFFT. To combat intersymbol interference (ISI) caused by frequency selective fading, the periodic prefix generator 952 includes a corresponding OFDM symbol containing N + C samples. Is repeated for each transformed symbol portion (or C sample). The repeated part is often called a cyclic prefix or guard interval. For example, the cyclic prefix length may be C = 512 when N = 4096. Each OFDM is transmitted in one OFDM symbol period (or simply a symbol period), which is an N + C sample period. The periodic prefix generator 952 provides an output sample stream {Y} to the combined symbol stream {Y _c }.

  FIG. 10A shows a block diagram of an embodiment of a wireless device 150 demodulator.

Demodulator 160 includes a cyclic prefix removal unit 1012, a Fourier transform unit 1014, a channel estimator 1016, and a detector 1018. . Periodic prefix removal unit 1012 removes the periodic prefix in 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 a set of S received symbols. , {Xm (k)}} to the interlace, where m = 1. A channel estimator 1016 is a channel gain estimate for each selected interlace m based on the input sample sequence {x (n)}.

(Derives). Detector 1018 is a channel gain estimate for the interlace.

Perform detection (eg, equalization or matched filtering) on the set of S received symbols {Xm (k)}} for each selected interlace with , S detected data symbols for the interlace

Supply.

  FIG. 10B shows a block diagram of an embodiment of an RX data processor at wireless device 150. Multiplexer 1030 receives all interlaced detected data symbols from detector 1018 and performs multiplexing of detected data and overhead symbols for each symbol period based on MUX_RX control, respectively. Each detected data symbol stream is provided to an RX data stream processor 1040 of interest to a respective RX data stream processor, and a detected overhead symbol stream is provided to an RX overhead data processor 1060.

Within each RX data stream processor 1040, a subband-to-symbol demapping unit 1042 passes received symbols on each subband in each selected interlace into the slot. Maps to the appropriate position of. An interlace-to-slot demapping unit 1044 maps each selected interlace to the appropriate slot. A symbol-to-bit demapping unit 1046 maps the received symbols for each slot to code bits. A descrambler 1048 descrambles the code bits for each slot and supplies descrambled data. Slot buffer 1050 buffers one or more slots of descrambled data, performs reassembly of packets as needed, and provides descrambled packets. A deinterleaver 1052 deinterleaves each descrambled packet and provides a deinterleaved packet. A decoder 1054 decodes the deinterleaved packets and provides decoded data packets for 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 in FIG. 9A. Symbol to bit demapping and decoding is performed according to the mode used for the data stream. An RX overhead data processor 1060 processes the received overhead symbols and provides decoded overhead data.

Due to the periodic structure of M interlaces, the Fourier transform unit 1014 obtains the set of S received symbols {Xm (k)}} for that interlace, A partial S′-point Fourier transform can be performed for each selected interlace m. The Fourier transform for an S ′ subband containing all S subbands of interlace m, where m = 1... M, can be expressed as:

Where x (n) is the sample period n,

, And N = M · S ′.

here,

Is a rotated sample and a phaser that changes the input sample x (n) from sample to sample.

(-1 in the exponents of the terms m-1 and n-1 is for an index numbering scheme starting with 1 instead of 0), and ,
g _m (n) is a time-domain value obtained by accumulating M rotated samples separated by S ′ samples.

Equation (1) can be expressed as:

The partial S ′ point Fourier transform for interlace m is performed as follows. N rotated sample

For each of the N input samples in the sequence {x (n)} of one symbol period, as shown in equation (2):

Is first rotated. As shown in equation (3), the rotated sample is then accumulated among the M rotated samples of the S ′ set to obtain the S ′ time domain value {g _m (n)}. Is done. Each set is a sequence

Contains every S'-th rotated sample, and the S 'set is a sequence

Related to different starting rotated samples. To obtain the S 'received symbols for interlace m, a normal S'-point Fourier transform is then performed, followed by the S' time domain value. Performed on {g _m (n)}. The received symbols for the S usable subbands are retained, after which the received symbols for the S′-S unused subbands are discarded.

For channel estimation, a partial S′-point Fourier transform is used to obtain a set of S received pilot symbols, {X _p (k)} or X (M · k + p), FDM It can be performed on N input samples for interlace p used for pilot. Channel gain estimate for subband in interlace p

ここで、Ｐ（Ｍ・ｋ＋ｐ）は、インタレースｐ中のｋ番目のサブバンド(the k-th subband)のための知られたパイロットシンボルであり、「＊」は、複素共役(a complex conjugate)である。式（５）は、全てのＳ'サブバンドがパイロット伝送に使用されることを前提にしている。

In order to obtain the modulation on the received pilot symbols, it is then removed as follows:

Where P (M · k + p) is a known pilot symbol for the kth subband in the interlace p, and “*” is a complex conjugate. ). Equation (5) assumes that all S ′ subbands are used for pilot transmission.

S ′ point to obtain a sequence of S ′ modulated time-domain channel gain values, {h _p (n)}, which can be expressed as IFFT then channel gain estimate

Done with respect to. The channel gain values in the sequence {h _p (n)} are then the sequence of S ′ derotated time-domain channel gain values.

To get

Derotated by multiplication with.

The channel gain estimate for the subbands in interlace m can then be expressed as:

As shown in equation (6), the channel gain estimate for the subbands in interlace m is the sequence of S ′ rotated channel gain values.

To obtain each derotated time domain channel gain value in the sequence {h (n)}

Can be obtained by first multiplying by The normal S ′ point FFT is then sequenced to obtain an S ′ channel gain estimate for the subbands in interlace m.

To be done. The rotated channel gain value for interlace m is

As can be obtained as

The derotation of h _p (n) by

The rotation of h (n) by can be combined.

  An exemplary channel estimation scheme has been described above. The channel estimation can also be done in other ways. For example, the channel estimates obtained for the different interlaces used for pilot transmission give a more accurate channel estimate for each interlace of interest. Can be filtered (eg, over time) and / or post-processed (eg, impulse response {h (n)}) to obtain Based on a least square estimate).

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

  For software implementation, multiplexing techniques can be implemented with modules (eg, procedures, functions, etc.) that perform the functions described herein. The software code is stored in a storage device (eg, storage device 142 or 182 in FIG. 1) and can be executed by a processor (eg, controller 140 or 180). The storage device can be implemented within the processor or external to the processor, in which case it is communicatively coupled to the processor via various means as is known in the art. I can do it.

  The previous description of the disclosed 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 readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. . Accordingly, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

FIG. 1 shows a block diagram of a base station and a wireless device. FIG. 2 shows an exemplary superframe configuration. FIG. 3 shows a combined subband configuration. FIG. 4A shows FDM pilots “staggered”. FIG. 4B shows a “circulated” FDM pilot. FIG. 5 shows an exemplary mapping of slot indexes to interlaces. FIG. 6 illustrates the encoding of a data block (?) Having an outer code. FIG. 7A shows packet transmission for different modes. FIG. 7B shows packet transmission for different modes. FIG. 8A shows the partitioning of a different number of packets into slots. FIG. 8B shows the partitioning of a different number of packets into slots. FIG. 9A shows a block diagram of a transmission (TX) data processor. FIG. 9B shows a block diagram of the modulator. FIG. 10A shows a block diagram of a demodulator. FIG. 10B shows a block diagram of a receive (RX) data processor.

Claims (47)

A data transmission method in a wireless multi-carrier communication system, comprising:
Assigning a slot to each of a plurality of data symbol streams, where each slot is a unit of transmission and the plurality of slots are frequency division multiplexed in each symbol period;
Multiplexing the data symbols in each data symbol stream on the slots assigned to the data symbol stream;
Forming a composite symbol stream with data symbols multiplexed onto the plurality of data symbol streams, wherein the plurality of data symbol streams can be independently recovered by a receiver;
A method comprising: Forming a plurality of non-overlapping interlaces in usable U frequency subbands for transmission, where U> 1 and each interlace is a different set selected from the U frequency subbands Frequency subbands of
Mapping the plurality of slots in each symbol period to the plurality of interlaces;
The method of claim 1, further comprising: Forming 2 ^N non-overlapping interlaces in multiple frequency subbands available for transmission, where N ≧ 1 and each interlace is selected from among the multiple frequency subbands Different sets of frequency subbands;
Mapping the plurality of slots in each symbol period to the 2 ^N interlaces;
The method of claim 1, further comprising: 4. The method of claim 3, wherein N is equal to 1, 2, 3, or 4. Forming the plurality of non-overlapping interlaces,
Forming the plurality of interlaces with an equal number of frequency subbands;
The method of claim 2, comprising: Forming the plurality of non-overlapping interlaces,
Forming the plurality of interlaces in the frequency subbands in each interlace combined with the frequency subbands in each of the remaining interlaces;
The method of claim 2, comprising: Forming the plurality of non-overlapping interlaces,
Forming a plurality of groups of frequency subbands, wherein each group includes frequency subbands uniformly distributed across the T total frequency subbands in the system, where T ≧ U;
Forming each interlace in a subband selected from a frequency subband of each group;
The method of claim 2, comprising: Assigning a slot to each of the plurality of data symbol streams,
Assigning each of the plurality of interlaces to one data symbol stream, even if so in each symbol period;
The method of claim 2, comprising: The plurality of slots in each symbol period are identified by a slot index;
For each symbol period, mapping the slot index to the plurality of interlaces based on a mapping scheme;
The method of claim 2, further comprising: Mapping the slot index to the plurality of interlaces;
Mapping each slot index used for data transmission to a different one of the plurality of interlaces in different symbol periods;
The method of claim 9, comprising: Distributing the data symbols multiplexed on each assigned slot across the frequency subbands in the interlace to which the slot is mapped;
The method of claim 2, further comprising: Distributing the data symbols multiplexed over each of the assigned slots is as follows:
Distributing the data symbols for each data packet sent to the slot across the frequency subbands in the interlace to which the slot is mapped;
The method of claim 11, comprising: Selecting a slot for pilot transmission from the plurality of slots in each symbol period;
Multiplexing pilot symbols on the slots used for pilot transmission;
The method of claim 2, further comprising: Mapping the slots used for pilot transmission to different interlaces in different symbol periods;
The method of claim 13, further comprising: Mapping the plurality of slots in each symbol period to the plurality of interlaces such that an interlace used for pilot transmission has a variable distance to an interlace used for data transmission;
The method of claim 13, further comprising: Assigning one or more slot indexes for pilot transmission;
Assigning the remaining slot index for data transmission;
The method of claim 9, further comprising: Mapping the one or more slot indices used for pilot transmission to one or more predetermined interlaces;
Mapping each slot index used for data transmission to a different interlace in different symbol periods;
The method of claim 16, further comprising: Processing a plurality of data streams to obtain the plurality of data symbol streams, one data symbol stream for each data stream;
The method of claim 1, further comprising: Assigning the slot to each of the plurality of data symbol streams;
Assigning a particular 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 1, further comprising: The processing of the plurality of data streams includes
Encoding a data packet for each data stream according to an encoding scheme for generating encoded packets for the data stream;
Modulating the encoded packet for each data stream according to a modulation scheme that generates data symbols for the corresponding data symbol stream;
The method of claim 18, further comprising: Encoding the data packets for each data stream comprises encoding an integer number of data packets for each data stream in each frame of a predetermined time interval,
The assigning the slot to each of the plurality of data symbol streams means that an integer number of slots are transmitted to each data symbol stream in each frame in the frame for the corresponding data stream. Comprising allocating based on a number of data packets,
The method of claim 18. Assigning the slot to each of the plurality of data symbol streams;
Assigning each data symbol stream to a specific number of slots determined by the encoding and modulation scheme and decoding constraints used for the data symbol stream;
The method of claim 1, comprising: An apparatus in a wireless multi-carrier communication system comprising:
A controller that operates to assign a slot to each of a plurality of data symbol streams, where each slot is a unit of transmission and the plurality of slots are frequency division multiplexed in each symbol period;
Data that operates to multiplex data symbols in each data symbol stream onto the slot assigned to the data symbol stream and to form a composite symbol stream with the data symbols multiplexed to the plurality of data symbol streams The processor and still here the plurality of data symbol symbol streams can be recovered independently by the receiver;
A device comprising: The controller further forms a plurality of non-overlapping interlaces in the U frequency subband available for transmission (where U> 1), and the slots in each symbol period are 24. The apparatus of claim 23, wherein the apparatus operates to map to a plurality of interlaces, each interlace being a different set of frequency subbands selected from the U frequency subbands. The plurality of slots in each symbol period are identified by a slot index, and the data processor is further operative to map the slot index to the plurality of interlaces based on a mapping scheme during each symbol period; 25. The apparatus of claim 24. The controller is further operative to select a slot for pilot transmission from among the plurality of slots in each symbol period, and the data processor is further configured to pilot symbols on the slot used for pilot transmission. 24. The apparatus of claim 23, wherein the apparatus operates to multiplex. The controller is further operative to allocate a particular 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. 23. The apparatus according to 23. The apparatus of claim 23, wherein the data processor is further operative to process a plurality of data streams to obtain a plurality of data symbol streams, one data symbol stream for each data stream. 24. The apparatus of claim 23, wherein the wireless multi-carrier communication system utilizes orthogonal frequency division multiplexing (OFDM). 24. The apparatus of claim 23, wherein the wireless multi-carrier communication system is a broadcast system. An apparatus in a wireless multi-carrier communication system comprising:
Means for assigning a slot to each of a plurality of data symbol streams, where each slot is a unit of transmission and the plurality of slots are frequency division multiplexed in each symbol period;
Means for multiplexing the data symbols in each data symbol stream onto the slots assigned to the data symbol stream;
Means for forming a composite symbol stream with data symbols multiplexed to the plurality of data symbol streams, wherein the plurality of data symbol streams are recoverable independently by a receiver;
A device comprising: Means for forming a plurality of non-overlapping interlaces in U frequency subbands usable for transmission, where U> 1, each interlace being a different one selected from said U frequency subbands A set of frequency subbands;
Means for mapping the plurality of slots in each symbol period to the plurality of interlaces;
32. The apparatus of claim 31, further comprising: The plurality of slots in each symbol period are identified by a slot index;
Further comprising means operative to map the slot index to the plurality of interlaces for each symbol period based on a mapping scheme;
The apparatus of claim 32. Means for selecting a slot for pilot transmission from among the plurality of slots in each symbol period;
Means for multiplexing pilot symbols on said slots used for pilot transmission;
32. The apparatus of claim 31, further comprising: Means for processing a plurality of data streams to obtain a plurality of data symbol streams, one data symbol stream for each data stream;
32. The apparatus of claim 31, further comprising: A method for receiving data in a wireless multi-carrier communication system, comprising:
Selecting one or more recovery data streams from a plurality of data streams transmitted by a transmitter in the system;
Determining which slot is used for each selected data stream, where each slot is a unit of transmission, and multiple slots are frequency division multiplexed in each symbol period, and , For each of the plurality of data streams, data symbols are multiplexed onto the slot assigned to the data stream, and wherein the plurality of data streams can be independently recovered by a receiver ;
Multiplexing the detected data symbols obtained for the slots used for each selected data stream onto the detected data symbol stream, where each detected data symbol is a data symbol An at least one detected data symbol stream is obtained for at least one data stream selected for recovery;
Processing each detected data symbol stream to obtain a corresponding decoded data stream;
A method comprising: Further comprising mapping the plurality of slots in each symbol period to a plurality of non-overlapping interlaces formed in U frequency subbands usable for transmission;
U> 1, and each interlace is a different set of frequency subbands selected from among the U frequency subbands.
36. The method of claim 35. The plurality of slots in each symbol period are identified by a slot index, and mapping the plurality of slots in each symbol period includes:
Mapping the slot index to the plurality of interlaces in each symbol period based on a mapping scheme;
38. The method of claim 37, comprising: Performing a partial Fourier transform on each slot used for each selected data stream to obtain data symbols received for the slot, and the partial Fourier transform is more than all in the system. Is the Fourier transform for a few frequency subbands;
Detecting for received data symbols for each slot used for each selected data stream to obtain detected symbols for said slot;
37. The method of claim 36, further comprising: 37. The method of claim 36, further comprising performing a partial Fourier transform on each slot used for pilot transmission to obtain a channel estimate for the slot. 41. The method of claim 40, further comprising deriving a channel estimate for each slot used for each selected data stream based on channel estimates obtained from slots used for pilot transmission. . An apparatus in a wireless multi-carrier communication system comprising:
A controller operative to select at least one recovery data stream from among a plurality of data streams transmitted by a transmitter in the system and to determine a slot to be used for each selected data stream; Here, each slot is a transmission unit, and a plurality of slots are frequency-division multiplexed in each symbol period, and here, for each of the plurality of data streams, a data symbol is converted into the data stream. Multiplexed on the assigned slot, and wherein the plurality of data streams are independently recoverable by the receiver;
The detected data symbols obtained for the slots used for each selected data stream are multiplexed onto the detected data symbol stream and each detected to obtain a corresponding decoded data stream. A data processor that operates to process the received data symbol stream, where each detected data symbol is an estimate of the data symbol and is at least 1 for the at least one data stream selected for recovery. Two detected data symbol streams are obtained;
A device comprising: The controller is further operative to map the plurality of slots in each symbol period to a plurality of non-overlapping interlaces formed with U frequency subbands available for transmission, where U> 43. The apparatus of claim 42, wherein each interlace is a different set of frequency subbands selected from among the U frequency subbands. To perform a partial Fourier transform on each slot used for each selected data stream to obtain received data symbols for the slot, and to obtain detected symbols for the slot 43. The apparatus of claim 42, further comprising a demodulator that operates to detect for the received data symbols for each slot used for each selected data stream. An apparatus in a wireless multi-carrier communication system comprising:
Means for selecting at least one recovery data stream from a plurality of data streams transmitted by a transmitter in the system;
Means for determining the slot to be used for each selected data stream, where each slot is a unit of transmission, and a plurality of slots are frequency division multiplexed in each symbol period, and , For each of the plurality of data streams, data symbols are multiplexed onto the slot assigned to the data stream, and wherein the plurality of data streams can be independently recovered by a receiver ;
Means for multiplexing the detected data symbols obtained for the slot used for each selected data stream onto the detected data symbol stream, wherein each detected data symbol is a data symbol An at least one detected data symbol stream is obtained for at least one data stream selected for recovery);
Means for processing each detected data symbol stream to obtain a corresponding decoded data stream;
A device comprising: Means for mapping the plurality of slots in each symbol period to a plurality of non-overlapping interlaces formed in U frequency subbands available for transmission, wherein U> 1, each interlace being 46. The apparatus of claim 45, wherein the apparatus is a different set of frequency subbands selected from among U frequency subbands. Means for performing a partial Fourier transform on each slot used for each selected data stream to obtain data symbols received for said slot;
Means for detecting for said received data symbols for each slot used for each selected data stream to obtain detected symbols for said slot;
46. The apparatus of claim 45, further comprising:

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