Transmission schemes for multi-antenna communication systems utilizing multi-carrier modulation

Transmission mechanism of multi-antenna communication system using multi-carrier modulation

The present invention generally relates to data transmission, and more particularly, to the preamble and data transmission mechanism of a multi-antenna transmission system using a multi-carrier mechanism.

The multiple antenna communication system utilizes multiple (T) transmission antennas and at least one (R) reception antenna for preamble and data transmission. T transmission antennas can be used to increase the throughput by transmitting independent data streams from the antennas. The T transmission antennas can also be used to improve reliability by transmitting a single data stream from the excessive antennas.

In a multi-antenna communication system, the channel gain between T transmitting antennas and R receiving antennas must be evaluated. Channel evaluation is required to determine the special mode for data transmission, to process received data transmission, etc. Typically, the receiver transmits a preamble, which is known as a priori, to perform channel evaluation. Then, the receiver can evaluate the channel gain as the ratio of the received preamble symbol to the conventional preamble symbol.

Both noise and interference usually impair channel assessment based on preamble transmission. Noise can come from various sources, such as wireless channels, receiver electronics, etc. Typically, the address noise damage can be addressed by appropriately designing the preamble signal and/or transmitting the preamble signal for a period of time, so that the receiver can obtain a specially designed quality channel assessment.

For a multi-antenna system, the preamble signal transmitted by all T transmission antennas at the same time will cause interference. This is because the preamble signal transmitted by each antenna acts as the interference to the preamble signal transmitted by other antennas.

When T transmission antennas are used for data transmission, the same interference phenomenon occurs. In particular, if multiple antennas transmit the same signal redundantly without addressing the interference, the receiver will cancel the signal depending on the channel conditions and the special location of the receiver. At the same time, a large amount of transmission and/or reliability will not be achieved by data being transmitted by multiple antennas at the same time.

Therefore, there is a need for a transmission mechanism that can effectively address interference in a multi-antenna communication system.

This article discloses the preamble and data transmission mechanism of the multi-antenna communication mechanism using multi-carrier modulation. In one view, sub-band multiplexing is used to prevent interference caused by multiple signals transmitted by multiple antennas at the same time. With factor band multiplexing, the M available sub-bands provided by multi-carrier modulation (for example, OFDM) can be arranged to form multiple groups of sub-bands, and each group includes a different subset of the available sub-bands. The sub-band group will be formed in the following various ways. Then, at least one sub-band group used for preamble transmission and a sub-band group typically used for data transmission are assigned to each T transmission antenna. The sub-band group used for preamble transmission and the sub-band group used for data transmission may be the same or different. Then, the preamble and data will be transmitted by each antenna on the sub-band assigned to the pre- and data transmission. With factor frequency band multiplexing, the preamble and/or data will be transmitted by all T antennas on all available sub-bands at the same time without causing interference.

Other technologies can also be used to improve the performance of preamble and data transmission. For example, for each transmission antenna, the transmission energy used for each sub-band assigned to the antenna will be larger, so all or nearly the sum of the transmission energy available to the antenna will be used for transmission. For preamble transmissions occurring during multiple symbols, the sub-bands assigned to the T transmission antennas can be exchanged. Sub-band exchange allows each antenna to use more sub-bands, and can still obtain improved channel evaluation while preventing interference.

Various viewpoints and examples of the present invention are described in detail below.

The word "exemplary" used in the text means to serve as an example, example, or illustration. The exemplary embodiments or designs described in the text need not be interpreted as preferred or superior embodiments or designs.

The preamble and data transmission mechanisms described in the article will be used in various multi-antenna communication systems and use various multi-carrier modulation techniques. For clarity, such a transmission mechanism will be specifically described for multiple antenna systems using Orthogonal Frequency Division Multiplexing (OFDM).

FIG. 1A shows an OFDM sub-band structure 100, which can be used in a multi-antenna communication system. The system has a full system bandwidth of W MHz, which can be divided into N orthogonal sub-bands using OFDM. In a typical OFDM system, only M sub-bands of the total N sub-bands are used for preamble and data transmission, where M<N. The remaining NM sub-bands are not used for preamble/data transmission, and are used as guard sub-bands to allow the system to meet the spectrum mask requirements. The M available sub-bands include sub-bands F to F+M-1, where F is typically a selected integer, so the M available sub-bands are concentrated in the middle of the operating frequency band.

For OFDM, data or preambles transmitted on each available sub-band are first modulated using a special modulation plan (ie, mapped to modulation symbols). A signal value of zero will be provided to each of the NM unused sub-bands. For each OFDM symbol period, N symbols (for example, M modulation symbols and NM zeros) used for a total of N subbands will be transformed into the time domain using inverse fast Fourier transform (IFFT) to obtain the transformed symbols. It includes N time-domain samples. In order to combat Inter-Symbol Interference (ISI) caused by frequency selective fading, part of each transition symbol is repeated to form a corresponding OFDM symbol, which includes N+C samples, where C is the number of repeated samples. The repeated part is usually called a cyclic prefix. Then, OFDM symbols will be transmitted between wireless channels. In the exemplary design, the system bandwidth is W=20MHz, the total number of sub-bands is N=256, the number of available sub-bands is M=224, and the duration of each transition symbol is 12.8 μsec. One OFDM symbol period (or simply, one symbol period) corresponds to the duration of the OFDM symbol.

As mentioned above, sub-band multiplexing is used to prevent interference caused by multiple signals transmitted by multiple antennas. Using sub-band multiplexing, the preamble and/or data will be simultaneously transmitted by T antennas on a sub-band group with no intersection (where there is no intersection as described below), so interference can be prevented. Several preamble and data transmission mechanisms can be defined by sub-band multiplexing. Some transmission mechanisms are as follows.

FIG. 1B shows a sub-band structure 150 supporting sub-band multiplexing. In this embodiment, the M available sub-bands will start to be divided into S disjoint groups, and each group includes T continuous sub-bands, where TS<img file="TW200423596A_D0001.tif" />M. Then, the T sub-bands in each group are assigned to the T group, and thus the i-th sub-band in each group is assigned to the i-th group. Using this sub-band assignment mechanism, the S sub-bands in each group are evenly allocated to M available sub-bands, and the consecutive sub-bands in the group are separated by T sub-bands. T groups containing sub-bands are assigned to T transmission antennas for preamble/data transmission.

Generally, within the scope of the present invention, M available sub-bands can be assigned to T groups in various ways. The T groups include the same or different numbers of sub-bands. Furthermore, the sub-bands in each group will be evenly or unevenly allocated to the M available sub-bands. The only requirement is that the T sub-band groups will have no intersection with others, so interference can be prevented. For simplification, the following description assumes that each T sub-band group includes S sub-bands, and the sub-bands of each group are evenly distributed and separated by T sub-bands (as shown in FIG. 1B), and TS=M.

Figure 2A shows an exemplary preamble/data transmission from T antennas using sub-band multiplexing. Each T sub-bands will be assigned a separate group containing sub-bands. In FIG. 2A, sub-band group 1 is assigned to antenna 1, sub-band group 2 is assigned to antenna 2, etc., and sub-band group T is assigned to antenna T. The T subband groups will be formed as described above, see Figure 1B. Each group includes S sub-bands, which can be displayed by shaded boxes. The preamble/data transmission from each antenna will only occur on the sub-band assigned to the antenna.

As shown in FIG. 2A, if the preamble/data is transmitted by each antenna only in the sub-band assigned to the antenna, the interference between subsequent transmissions from the T antennas will disappear. Because the sub-bands will be orthogonal to each other, and at most one antenna used for transmission will use each sub-band. Therefore, even T transmissions transmitted by T antennas at the same time will prevent interference.

In a typical wireless communication system, each antenna will be<i>P</i>_<i>ant</i>This is related to the transmission energy, which is the maximum transmission energy used for the lead/data transmission from the antenna. By the peak output of the energy amplifier used for the antenna, or by adjusting the limit, and/or by some other demand indication<i>P</i>_<i>ant</i>. Increased performance can be achieved by using all or as much total transmission energy as possible for the preamble/data transmission from each antenna. In particular, since only S of the M available sub-bands will be assigned to each antenna, where S=M/T, for simplicity, the transmission energy of each S sub-bands assigned to each antenna will be increased by a factor T. Then, a higher received signal-to-noise ratio (SNR) will be allowed to achieve each of the S for each antenna.

In the first preamble transmission mechanism, the preamble is simultaneously transmitted by T antennas using sub-band multiplexing. Sub-band groups will be formed and the number of sub-bands in each group will be greater than the maximum expected delay spread of the system. The delay spread for a particular receiver will differ between the first and last signal distances (receivers used for the signals transmitted by the transmitter). The system's delay spread (L) is the expected worst-case delay spread for all receivers in the system, and will be distributed throughout the coverage area of the system. In order to effectively combat ISI, the cyclic prefix should be longer than the delay spread of the system (ie, C&gt;L, where the unit of the delay spread L is the sample period). Then, the number of subbands in each group will be selected to be greater than or equal to the number of samples used for the cyclic prefix (ie, S<img file="TW200423596A_D0002.tif" />C).

The channel estimation derivation of all M available sub-bands based on a subset of M sub-bands is described in detail as follows: US Patent (Application No. [Attorney's Case No. 020718], titled "Channel Estimation for OFDM Communication" Systems", application date 1/10/2003), and provisional US patent (application number 60/427,896, title "Reduced Complexity Channel Estimation for Wireless Communication Systems", application date 11/19/2002), both Belongs to the applicant of this application, and here and for reference.

For increased performance, the transmission energy of each assigned sub-band for each T antenna will increase by a factor of T. Then, for each antenna, the total energy of the preamble transmission on the S assigned sub-bands will be the same, just as all M available sub-bands will be used for the preamble transmission. The higher transmission energy of each sub-band allows the receiver to obtain a higher quality channel evaluation.

If the number of sub-bands assigned to each antenna is equal to or greater than the delay spread of the system (i.e., S<img file="TW200423596A_D0003.tif" />L), then the channel gains of all M useful sub-bands used for the antenna will be evaluated based on the preamble transmission only in the S sub-bands assigned to the antenna. Furthermore, if the transmission energy of each S sub-bands assigned to each antenna is increased by a coefficient T, the quality of the channel evaluation based on the preamble transmission obtained on only S sub-bands with the same amount of transmission energy will be roughly It is equivalent to the channel evaluation quality based on the preamble transmission on all M available sub-bands. That is, by maintaining the same total preamble energy, the receiver can evaluate the channel gain for all M available sub-bands based on the preamble transmission on a unique subset of the sub-bands (with little or no loss in quality).

The first preamble transmission mechanism allows all T antennas to transmit the preamble at the same time. In order to obtain a channel evaluation of comparable quality, the conventional preamble mechanism that simultaneously transmits all T antennas on all M available sub-bands requires a transmission duration, which is approximately T times longer than that required by the first preamble transmission mechanism. For example, if N_PT preamble OFDM symbols use the conventional mechanism to obtain a channel assessment of a specific quality, and the channel assessment of comparable quality can be based on N transmitted on T antennas_PObtained from the preamble OFDM symbol. Assuming that (1) each antenna is assigned a sufficient number of sub-bands, which is equal to or greater than the cyclic prefix, and (2) the energy specification is used, so the total transmission energy available for each antenna can be used for pre-transmission on the assigned sub-bands. The energy specification was described in the aforementioned US patent (Case No. [Attorney's Case No. 020718]). Therefore, the first preamble transmission mechanism can reduce the preamble sorting operation by a factor of up to T, which is the number of transmission antennas.

In the second preamble transmission mechanism, the preamble is simultaneously transmitted by T antennas using sub-band multiplexing and sub-band switching. The preamble must be transmitted during multiple OFDM symbols. It may be a situation, for example, if the preamble must be averaged over a long period of time to obtain a moderately accurate channel gain assessment. In this situation, additional channel gain improvement can be obtained by assigning multiple groups containing sub-bands to each antenna used for preamble transmission.

Figure 2B shows an exemplary preamble transmission from T antennas using sub-band multiplexing and sub-band switching. For example, preamble transmission occurs during two OFDM symbols. Two groups with sub-bands will be assigned to each T antenna (for example, group<i>i</i>And T/2+<i>i</i>Will be assigned to the<i>i</i>Antennas), each group contains the sub-bands shown in the shaded box. The two groups assigned to each antenna can be selected, so the sub-bands in the group can be separated by T/2 sub-bands. Furthermore, the group will be assigned to T antennas, so for each OFDM symbol period, the T antennas used for the preamble transmission will use the non-crossing cluster. A specific sub-band group will be assigned to multiple antennas (for example, sub-band group 1 will be assigned to antenna 1 and T/2+1), but the antenna will use sub-band groups in different symbol periods.

In Figure 2B, subband group 1 and T/2+1 will be assigned to antennas, subband group 2 and T/2+2 will be assigned to antenna 2, etc., and subband groups T and T/2 will be assigned to Antenna T. For the first OFDM symbol period, subband group 1 can be used for antenna 1, subband group 2 can be used for antenna 2, etc., and subband group T can be used for antenna T. For the second OFDM symbol period, subband group T/2+1 can be used for antenna 1, subband group T/2+2 can be used for antenna 2, etc., and subband group T/2 can be used for antenna T.

Then, the channel gain for each T antenna can be evaluated based on the preamble transmission in the two groups of sub-bands. Using sub-band switching, the total number of sub-bands used for each antenna is 2S instead of S, and improved channel gain can be obtained for all M available sub-bands due to the larger number of sub-bands used for preamble transmission.

For simplicity, Figure 2B shows sub-band multiplexing and switching for exemplary preamble transmission that occurs during two OFDM symbols. Generally, preamble transmission will occur during Q OFDM symbols, where Q is an integer not less than one. Then, Q sub-band groups are assigned to each antenna, and each group includes S sub-bands. Then, a total of SQ sub-bands are assigned to each antenna, and the SQ sub-bands are equally divided by T/Q sub-bands. If Q<img file="TW200423596A_D0004.tif" />2. For each antenna, the sub-bands of each Q group will be mixed with the sub-bands of other Q-1 groups. Due to interleaving, each Q consecutive sub-bands assigned to a specific antenna will be included in the Q groups assigned to the antennas. The Q subband groups assigned to each antenna are used for Q OFDM symbol periods, including a different group of Q groups for each symbol period. For each symbol period, T uncrossed clusters with sub-bands can be used to transmit T antennas at the same time.

The transmission mechanism shown in FIGS. 2A and 2B can be used for data transmission like the preamble transmission. However, for data transmission, it is usually desirable to transmit data (instead of a single antenna) by multiple antennas for each M useful sub-bands. The use of multiple antennas for each sub-band can provide transmission diversity and increase the diversity order of the receiver's signal detection. Transmission diversity can improve the reliability and robustness of data transmission, thereby resulting in a lower error rate and/or higher toughness to path loss.

Transmission diversity can be achieved by various diversity mechanisms. Some examples of such diversity mechanisms include a spatio-temporal transmission diversity (STTD) mechanism and a Wassi-STTD mechanism. For the STTD mechanism, a single data stream can be processed to provide two symbol streams, which can be transmitted by two antennas (or two antennas multiplexed by sub-bands). For the Wassi-STTD mechanism, a single data stream can be processed to provide W symbol streams, which can be transmitted by W antennas (or W groups of antennas multiplexed by sub-bands), where W is used for Wassi-STTD processing Two times the length of the orthogonal code (for example, Wassi code). This two-diversity mechanism is described in detail below.

For the STTD mechanism, if multiple pairs of antennas are available, the transmission of the same pair of symbol streams from each pair of antennas will only cause the receiver's signal to be erased. Then, all the antennas can only transmit data redundantly to obtain improved reliability.

In the first data transmission mechanism, sub-band multiplexing is used to simultaneously transmit data by antenna pairs. This transmission mechanism can be used for the STTD mechanism and the equivalent diversity mechanism. For this data transmission mechanism, M available sub-bands will start to be arranged to form T/2 disjoint clusters containing sub-bands, and each available sub-band will only be assigned to a unique group. The T/2 group includes the same or different number of sub-bands. The sub-bands in each group are evenly or unevenly allocated to the M available sub-bands. Therefore, within the scope of the present invention, M available sub-bands will be assigned to T/2 groups in various ways. In an embodiment to be described below, each group includes 2S sub-bands, which will be evenly distributed, so that the continuous sub-bands in the group are separated by T/2 sub-bands. Then, T/2 sub-band groups are assigned to T/2 sub-band pairs, and one sub-band group is assigned to each antenna pair.

Figure 3A shows an exemplary data transmission from T antennas using sub-band multiplexing and transmission diversity. T antennas will be arranged as T/2 pairs, of which the first<i>i</i>Pair includes two antennas, which are marked as A<i>i</i>And B<i>i</i>. Each T/2 antenna pair is assigned a sub-band group, and the T/2 sub-band group is formed as described above. In Figure 3A, subband group 1 is assigned to pair 1, which includes antennas A1 and B1, subband group 2 is assigned to pair 2, which includes antennas A2 and B2, etc., and subband group T/2 is assigned To pair T/2, it includes antennas At and Bt (where t=T/2). Data can be transmitted by each antenna pair on the sub-band assigned to the antenna pair.

The STTD mechanism can be used to provide a pair of symbol streams, which can be demultiplexed to provide a pair of symbol substreams for each pair of antennas. Therefore, T/2 symbol substream pairs can be generated by the STTD mechanism for T/2 antenna pairs. For each OFDM symbol period, the symbol substream for each antenna includes a data symbol for each subband assigned to the antenna, and a signal zero value for each remaining subband. As shown in Figure 3A, the symbol substream pair for antenna pair 1 will be transmitted on subband group 1, and the symbol substream pair used for antenna pair 2 will be transmitted on subband group 2, etc., and used for antennas. The symbol sub-stream pair of T/2 will be transmitted on the sub-band group T/2. Although the T/2 symbol sub-stream pairs will be simultaneously transmitted by T/2 antenna pairs, they will not interfere with each other because they will be transmitted on non-intersecting sub-band groups. Therefore, it is possible to prevent degraded effects caused by destructive interference between transmissions from different antenna pairs.

For improved performance, each symbol sub-stream can be used by the relevant antenna with the total transmission energy available for that antenna.<i>P</i>_<i>ant</i>transmission. Because only 2S available sub-bands of the M available sub-bands can be used for each T antenna (for the sake of simplicity, S=M/T), the transmission performance coefficient T for each 2S sub-bands assigned to each antenna can be /2 increases. Then, a higher received SNR is allowed to be achieved for each 2S sub-band, which is assigned to each antenna. The higher received SNR for each sub-band will support a higher data rate, which in turn will increase the overall system throughput.

Figure 3A shows an example of assigning M available sub-bands to T antennas. Within the scope of the present invention, the available sub-bands can also be assigned to T antennas in various other ways. For example, sub-bands can be assigned to antennas so that different antenna pairs can be used for data transmission. Therefore, additional diversity can be provided.

Figure 3B shows exemplary data transmission by T antennas using sub-band multiplexing and different antenna pairs for transmission diversity. For simplicity, the description in Figure 3B assumes that T=4 antennas will be used for data transmission. Six different antenna pairs can be formed to have four antennas. The antenna pairs are labeled {1,2}, {3,4}, {1,3}, {2,4}, {1,4}, and { 2,3}.

The M available sub-bands will start to be divided into M/6 groups, and each group includes 6 sub-bands. The 6 sub-bands in each group can then be assigned to 6 different antenna pairs, with one sub-band corresponding to one pair. In Figure 3B, the first sub-band in each group is assigned to the antenna pair {1,2}, and the second sub-band in each group is assigned to the antenna pair {3,4}, etc., and the Finally, the sub-band will be assigned to the antenna pair {2,3}.

The data stream transmitted by the four antennas can be processed using the STTD mechanism to obtain a two-symbol stream. The first symbol stream can be transmitted by the first or left antenna of the 6 pairs, and the second symbol stream can be transmitted by the second or right antenna of the 6 pairs. The first and second symbol streams are then demultiplexed to form four-symbol sub-streams, one sub-stream for each of the four antennas. Each symbol substream includes data symbols for each subband assigned to the relevant antenna, and signal zeros for each unassigned subband.

When the four-symbol sub-stream is available, it is transmitted by four antennas. However, the symbol sub-streams will not interfere with each other because they are transmitted on four disjoint sub-band groups. The sub-band groups have no intersection, so each M available sub-bands will be assigned to a unique antenna pair, as shown in FIG. 3B.

In the second data transmission, data can be transmitted by a group of W antennas using sub-band multiplexing, where W is any integer not less than one. This transmission mechanism can be used for the Vathy-STTD mechanism and other diversity mechanisms. For this data transmission mechanism, the M available sub-bands will start to be arranged to form T/W disjoint sub-band groups, and each sub-band will only be assigned to one group. The T/W groups include the same or different numbers of sub-bands. The sub-bands in each group are evenly or unevenly allocated to the M available sub-bands. In one of the following embodiments, each group includes SW sub-bands (where S=M/T), which will be evenly distributed, so that the continuous sub-bands in the group will be separated by T/W sub-bands. For W&gt;1, this second transmission mechanism allows more sub-bands to be assigned to each antenna than the above-mentioned first transmission mechanism. Having more sub-bands per antenna is beneficial for the same implementation. T/W sub-band groups are assigned to T/W antenna groups, one sub-band group corresponds to each antenna group, and each antenna group includes W antennas. Each antenna can transmit data on the sub-band assigned to the antenna.

Figure 3C shows exemplary data transmission from W antenna groups using sub-band multiplexing. T antennas will be arranged into T/W groups, of which the first<i>i</i>The group includes W antennas, which are denoted as A<i>i</i>, B<i>i</i>, To W<i>i</i>. Each T/W antenna group is assigned a separate sub-band group, and T/W sub-band groups are formed as described above.

The Wassi-STTD mechanism can be used to process a single data stream to provide W symbol streams, where W is twice the length of the orthogonal sequence used for processing (for example, the Wassi sequence). The W symbol streams can be demultiplexed to provide T/W symbol substream groups, and each group includes W symbol substreams. Then, the T/W groups collectively include T symbol substreams. A symbol sub-stream group will be provided to each antenna group, and each antenna will be provided in a separate symbol sub-stream. For each OFDM symbol period, the symbol substream for each antenna includes data symbols for each subband assigned to the antenna, and signal zeros for the remaining subbands. T symbol substreams will be simultaneously transmitted by T antennas. However, the symbol sub-streams will not interfere with each other because they will be transmitted on non-intersecting sub-band groups, so each sub-band will be assigned to a unique group.

Figures 2A and 2B and 3A to 3C show an exemplary sub-band multiplexing mechanism, which can be used for preamble and data transmission. Within the scope of the present invention, multiple other sub-band multiplexing mechanisms can also be used devices. For example, both preamble and data can be transmitted during an OFDM symbol period. In this situation, some of the M available sub-bands can be used for preamble transmission, and the remaining available sub-bands can be used for data transmission. The preamble sub-bands can be multiplexed (for example) as shown in Figure 2A or 2B. Data sub-bands can be multiplexed (for example) as shown in Figure 3A, 3B or 3C.

FIG. 4 shows a flowchart of an embodiment of a procedure 400 for transmitting preamble and/or data sub-band multiplexing. Initially, the M available sub-bands are arranged to form multiple sub-band groups, where each group includes a different sub-group containing M available sub-bands (step 412). The sub-band group can be formed as described above.

Then, each antenna assigns at least one possible sub-band group for preamble and data transmission (step 414). The sub-band group used for preamble transmission and the sub-band group used for data transmission may be the same or different. For the preamble transmission, each antenna is assigned a different group of sub-bands (as shown in Figure 2A above). Alternately, each antenna is assigned at least two groups of sub-bands for sub-band exchange (as shown in FIG. 2B above). For data transmission, each pair of antennas can be assigned a different group of sub-bands (as shown in Figure 3A above), and each antenna will be assigned a different group of sub-bands (as shown in Figure 3B above), each containing W sub-bands The groups of can be assigned sub-bands of different groups (as shown in Figure 3C above), and so on.

The preamble and/or data will then be processed (step 416). For example, STTD encoding, Wassi-STTD encoding, or some other encoding can be used to process the data. It is also possible to determine the total transmission energy for each sub-band assigned to each T antenna (step 418). In particular, the transmission energy of the sub-bands used for each assignment will be higher than the average energy, which is used when transmitting on all M available sub-bands. The scale factor depends on the number of sub-bands assigned to each antenna and the number of available sub-bands.

Then, multiple sub-band groups are used to transmit the preamble and/or data from T antennas at the same time, and the determined transmission energy is used (step 420). The transmission from each antenna will occur in a sub-band group (or multiple groups) that is uniquely assigned to the antenna. For preamble transmission, typically for each M available sub-bands, the only antenna among the T antennas can be used during any particular symbol period. For data transmission, at least two possible antennas are typically available for each M available sub-bands.

FIG. 5 shows a block diagram of an embodiment of a transmitter unit 500 and two receiver units 550x and 550y in a multiple antenna communication system with multiple carrier modulation (for example, OFDM). The transmitter unit 500 will be equipped with T antennas, the receiver unit 550x will be equipped with a single antenna, and the receiver unit 550y will be equipped with R antennas.

In the transmitter unit 500, the transmission (TX) data processor 510 receives traffic data from a data source 508 and other data from a controller 530. The TX data processor 510 encodes, interleaves, and modulates data to provide modulation symbols, which may also be referred to as data symbols. The TX spatial processor 520 receives and multiplexes data symbols with leading symbols (for example, using time division multiplexing or sub-band multiplexing processing), and can perform spatial processing for data transmission. For example, the TX spatial processor 520 may implement the STTD mechanism, the Wassey-STTD mechanism, or other mechanisms. The TX spatial processor 520 provides a stream of transmission symbols for each T antenna. (In the above description, the transmission symbol stream is called a symbol sub-stream.) Each modulator (MOD) 522 receives and processes the individual transmission symbol stream to provide a corresponding radio frequency (RF) modulation signal. T modulators 522a to 522t can generate T RF modulated signals and transmit them by T antennas 524a to 524t, respectively.

In each receiver unit 550, at least one antenna 552 will receive the transmitted RF modulated signal, and each antenna will provide the received signal to an individual demodulator (DEMOD) 554. For what the modulator 522 performs, each demodulator 554 will supplement the execution and provide the received symbols. Then, the receive (RX) spatial processor 560 will perform spatial processing on the received symbols from all demodulators 554 to provide the reply symbols, which are the evaluation of the data symbols transmitted by the transmitter unit. The RX data processor 570 reprocesses (eg, demodulates, resolves, and decodes) the returned symbols to provide decoded data, which can be provided to the data 572 for storage and/or the controller 580 for further processing. The RX spatial processor 560 will also evaluate the channel gain based on the received preamble, and provide channel evaluation (marked as the channel response matrix<b><u style="single">H</u></b>) To the controller 580.

The controllers 530 and 580 control the operations of various processing units in the transmitter unit and the receiver unit, respectively. The memory units 532 and 582 store data and program codes used by the controllers 530 and 580, respectively.

FIG. 6 shows a block diagram of the TX spatial processor 520a. The TX spatial processor 520a implements the STTD mechanism and is an embodiment of the TX spatial processor 520 of FIG. 5. Data symbol from TX data processor 510<i>s</i>(<i>n</i>) Will be provided to the demultiplexer 610, whose demultiplexed data symbols are 2M data symbol substreams (marked as<i>s</i>_<i>k</i>,1(<i>n</i>)and<i>s</i>_<i>k</i>,2(<i>n</i>),in<i>k</i>{1...M}, a pair of data symbol sub-streams are used for each M available sub-bands. Each data symbol substream includes data symbols for each interval of the two OFDM symbol period. The M data symbol substream pairs for the M available subbands are provided to the M spatiotemporal encoders 620a to 620m.

Each spatiotemporal encoder 620 receives and processes its data symbol substream pair to provide a symbol substream for the second spatiotemporal encoding of the relevant subband. Pair the data symbol pairs in the second input substream (for example,<i>s</i>_<i>k</i>,1，<i>s</i>_<i>k</i>,2), the spatio-temporal encoder 620 will provide two vectors<b><u style="single">x</u></b>_<i>k</i>,1and<b><u style="single">x</u></b>_<i>k</i>,2, Each vector includes two space-time coded symbols (or simply coded symbols), which can be sequentially transmitted by the relevant antenna during the two OFDM symbol periods. In particular, the vector<b><u style="single">x</u></b>_<i>k</i>,1Will have an antenna in the first<i>k</i>Sub-band transmission, and vector<b><u style="single">x</u></b>_<i>k</i>,2Will have another antenna on the<i>k</i>Sub-band transmission. In one embodiment, the vector will be defined as<b><u style="single">x</u></b>_<i>k</i>,1=[<i>s</i>_<i>k</i>,1<i>s</i>^*_k,2]^<i>T</i>,and<b><u style="single">x</u></b>_<i>k</i>,2=[<i>s</i>_<i>k</i>,2-s^*_<i>k</i>,1]^<i>T</i>,As shown in Figure 6. In another embodiment, the vector would be defined as<b><u style="single">x</u></b>_<i>k</i>,1=[<i>s</i>_<i>k</i>,1<i>s</i>_<i>k</i>,2]^<i>T</i>,and<b><u style="single">x</u></b>_<i>k</i>,2=[-<i>s</i>_<i>k</i>,2<i>s</i>^*_<i>k</i>,1]^<i>T</i>. The code symbols in each vector have the same intensity as the data symbols, but the phase is opposite. Each spatio-temporal encoder 620 provides two coded symbol substreams to the two multiplexer/demultiplexer 630a and 630b.

Each multiplexer/demultiplexer 630 receives preamble symbols and M coded symbol substreams from M space-time encoders 620a to 620m, multiplexes the coded symbols and preamble symbols based on a special data/preamble transmission mechanism, and provides T/2 transmission symbol streams for T/2 antennas. Each transmission symbol stream includes preamble symbols during preamble transmission and code symbols during data transmission, where the preamble and code symbols are transmitted on a sub-band assigned to the antenna used to transmit the transmission symbol stream.

During the preamble transmission, the multiplexer/demultiplexer 630a and 630b will jointly provide T transmission symbol streams for T antennas. Each transmission symbol stream includes preamble symbols for assignment to the relevant antenna and signal zeros for unassigned sub-bands. For the transmission mechanism shown in Figure 2A, the flow<i>x</i>_<i>A</i>1(<i>n</i>) Includes the preamble symbol for the sub-band of group 1,<i>x</i>_<i>A</i>2(<i>n</i>) Includes the preamble symbols used for the sub-bands of group 2, etc., and<i>x</i>_<i>Bt</i>(<i>n</i>) Includes the preamble symbol for the sub-band of the group T.

During data transmission, the multiplexers/demultiplexers 630a and 630b each provide T/2 transmission symbol streams for T/2 antennas, where each stream includes coded symbols for sub-bands assigned to the relevant antenna And the signal zero value for unassigned sub-bands. For the transmission mechanism shown in Figure 3A, the flow<i>x</i>_<i>A</i>1(<i>n</i>)and<i>x</i>_<i>B</i>1(<i>n</i>) Includes the coding symbols used for the sub-bands of group 1,<i>x</i>_<i>A</i>2(<i>n</i>)and<i>x</i>_<i>B</i>2(<i>n</i>) Includes coding symbols for subbands of group 2, etc., and<i>x</i>_<i>At</i>(<i>n</i>)and<i>x</i>_<i>B</i>t(<i>n</i>) Includes coding symbols for subbands of group T/2.

Each modulator 522 processes the individual transmission symbol streams in the following manner to provide coding symbols for the sub-bands in the group T/2.

The STTD mechanism described in SM Alamouti's previous case "A Simple Transmit Diversity Technique for Wireless Communications" (IEEE Journal on Selected Areas in Communications, Vol. 16, No. 8, October 1998, pages 1451-1458) is here. And for reference. Another US patent application (Case No. 10/179,439, titled "Diversity Transmission Modes for MIMO OFDM Communication System", application date 2002/6/24) of the applicant of this patent application is hereby incorporated for reference.

The Wassi-STTD mechanism uses the following combination: (1) A pair of antennas achieves orthogonal STTD, and (2) a pair of antennas achieves orthogonal Wassi diversity. The Wassi-STTD mechanism can be used in systems with more than two antennas (for example, 4, 6, 8, etc.).

FIG. 7A shows a block diagram of the TX spatial processor 520b, which implements the Wassey-STTD mechanism and is another embodiment of the TX spatial processor 520 of FIG. 5. In this embodiment, the Wassey order of 2 wafers will be used for processing, and W=4. Data symbol<i>s</i>(<i>n</i>) Will be provided to the demultiplexer 710, which will demultiplex the symbol into 4M data symbol substreams (labeled<i>s</i>_<i>k</i>,1(<i>n</i>)to<i>s</i>_<i>k</i>,1(<i>n</i>), where k<img file="TW200423596A_D0005.tif" />{1...M}, one of the four sub-streams is used for each of the M available sub-bands. The M data symbol sub-stream groups for the M available sub-bands will be provided to M Wassi-STTD encoders 720a to 720m.

Each Wassey-STTD encoder 720 receives and processes its group of four data symbol substreams<i>s</i>_<i>k</i>,1(<i>n</i>)to<i>s</i>_<i>k</i>,4(<i>n</i>), and provide four Wassi-STTD coded symbol substreams<i>z</i>_<i>k</i>,1(<i>n</i>)and<i>z</i>_<i>k</i>,4(<i>n</i>) To four multiplexers/demultiplexers 730a to 730d. The processing of the encoder 720 is detailed as follows. Each multiplexer/demultiplexer 730 receives preamble symbols and M coded symbol substreams from M Wassey-STTD encoders 720a to 720m, and multiplexes the coded symbols and preamble symbols based on a special data/preamble transmission mechanism , And provide T/4 transmission symbol streams for T/4 antennas. Each transmission symbol stream includes preamble/coding symbols for the sub-band assigned to the antenna used to transmit the stream.

FIG. 7B shows a block diagram of the Wassey-STTD encoder 720x, which is used for each of the encoders 720a to 720m in FIG. 7A. In the Wassey-STTD encoder 720x, the spatio-temporal encoder 722a receives the first pair of data symbol substreams<i>s</i>_<i>k</i>,1and<i>s</i>_<i>k</i>,2, And the time-space encoder 722b receives the second pair of data symbol substreams<i>s</i>_<i>k</i>,3and<i>s</i>_<i>k</i>,4. For each pair of data symbols in the first pair and the second substream, the spatio-temporal encoder 722a provides a two vector<b><u style="single">x</u></b>_<i>k</i>,1=[<i>s</i>_<i>k</i>,1<i>s</i>^*_<i>k</i>,2]^<i>T</i>,and<b><u style="single">x</u></b>_<i>k</i>,2=[<i>s</i>_<i>k</i>,2-<i>s</i>^*_<i>k</i>,1]^<i>T</i>Respectively to multiplexers 724a and 724b. Similarly, for each pair of data symbols in the second pair of two substreams, the spatio-temporal encoder 722b provides a two vector<b><u style="single">x</u></b>_<i>k</i>,3=[<i>s</i>_<i>k</i>,3<i>s</i>^*_<i>k</i>,4]^<i>T</i>,and<b><u style="single">x</u></b>_<i>k</i>,4=[<i>s</i>_<i>k</i>,4-<i>s</i>^*_<i>k</i>,3]^<i>T</i>Respectively to multiplexers 724c and 724d.

The multiplexers 724a and 724b also each receive the first 2 chip Wassi order W₁²=[0 1], and multiplexers 724c and 724d also each receive the second 2-chip Wassey order W₂²=[1 0]. Then, each multiplexer 724 multiplexes each symbol (its vector<b><u style="single">x</u></b>_<i>k</i>,1) To provide two Wasi-STTD coded symbols, which are sequentially placed on the first antenna of the relevant antenna during two consecutive OFDM symbols.<i>k</i>Transmission on sub-bands. The four multiplexers 724a to 724d provide four coded symbol substreams to the four multiplexers/demultiplexers 730a to 730d, respectively.

It can also implement the Vassy-STTD mechanism, so there are only one pair of data symbol substreams<i>s</i>_<i>k</i>,1and<i>s</i>_<i>k</i>,2Will be provided to each Wassey-STTD encoder 720 and processed to provide a four-encoded symbol substream<i>z</i>_<i>k</i>,1(<i>n</i>)and<i>z</i>_<i>k</i>,4(<i>n</i>). It can also be used to achieve more diversity at a lower data rate. The Wassi-STTD mechanism is also described in detail in the aforementioned US application (Case No. 10/179,439).

FIG. 8 shows a block diagram of an embodiment of an OFDM modulator 522x, which can be used in each of the T modulators 522a to 522t in FIG. 5. In the OFDM modulator 522x, the inverse fast Fourier transform (IFFT) unit 812 will receive for the first<i>i</i>Antenna transmission symbol stream<i>x</i>_<i>i</i>(<i>n</i>), and use N-point inverse fast Fourier transform to transform each sequence of N transmission symbols into time-domain transform symbols, where N corresponds to the total number of sub-bands. Each sequence of N transmission symbols includes<i>i</i>Data/preamble symbols for sub-bands of each antenna and signal zero for unassigned sub-bands. Each transition symbol includes N time-domain samples. For each transition symbol, the cyclic prefix generator 814 repeats a part (or C samples) of the transition symbol to form a corresponding OFDM symbol, which includes N+C samples. The transmitter (TMTR) 816 receives and converts the OFDM symbol stream from the generator 814 into at least one analog signal, and then amplifies, filters, and adjusts the frequency of the analog signal to generate the first analog signal.<i>i</i>RF modulated signal from two antennas.

The preamble and data transmission described in the article can be implemented in a variety of ways. For example, this technology can be implemented in hardware, software, or a combination thereof. For hardware implementation, the components used to perform processing in the transmitter and receiver units can be implemented in at least one of the following or a combination: application-specific integrated circuit (ASIC), digital signal processor (DSP) ), Digital Signal Processing Device (DSPD), Programmable Logic Device (PLD), Field Programmable Gate Array (FPGA), Controller, Microcontroller, Microprocessor, and other electronic units designed to perform the functions in the article .

For software implementation, the processing of the transmitter and receiver units used in the transmission mechanism described in the text can be implemented in modules (for example, processes, functions, etc.) to perform the functions described in the text. The software code can be stored in a memory unit (for example, memory units 532 and 582 in FIG. 5), and executed by a processor (for example, controllers 530 and 580). The memory unit can be implemented inside or outside the processor, and its enclosure can be communicatively coupled to the processor through various conventional methods.

The above-disclosed embodiments can enable those familiar with this technology to manufacture or use the present invention. Those who are familiar with this technology should understand the various modifications of this embodiment, and the broad general definitions defined in the text will be applied to other embodiments within the spirit and scope of the present invention. Therefore, the present invention is not limited to the embodiments shown in the text, but should refer to the broadest scope of the principles and new features disclosed in the text.

<p>500Transmitter unit</p><p>508Data source</p><p>510Transmission Data Processor</p><p>520TX Spatial Processor</p><p>522Modulator</p><p>524antenna</p><p>530controller</p><p>532Memory Unit</p><p>550receiver unit</p><p>552antenna</p><p>554demodulator</p><p>560Receiving Space Processor</p><p>570RX Data Processor</p><p>572Data Shen</p><p>580controller</p><p>582Memory Unit</p><p>610Demultiplexer</p><p>620Space-Time Encoder</p><p>630Multiplexer/Demultiplexer 630</p><p>710Demultiplexer</p><p>720Vasi-STTD encoder</p><p>722Space-Time Encoder</p><p>724Multiplexer</p><p>730Multiplexer/Demultiplexer</p><p>812Anti-Fast Fourier Transformation Unit</p><p>814Cyclic Prefix Generator</p><p>816Transmitter</p>

The features, essence and advantages of the present invention will be more clearly described below and with reference to the drawings. The same reference signs in the figures and text will be equal to each other: Figure 1A shows the OFDM sub-band structure; Figure 1B shows the support for sub-band multiplexing Processed sub-band structure; Figure 2A shows an exemplary preamble/data transmission from T antennas using sub-band multiplexing; Figure 2B shows an exemplary preamble from T antennas using sub-band multiplexing and sub-band switching Transmission; Figure 3A shows exemplary data transmission from T antennas using sub-band multiplexing and transmission diversity; Figure 3B shows data transmission from T antennas using sub-band multiplexing and different antenna pairs for transmission subsets Exemplary data transmission; Figure 3C shows an exemplary data transmission from a group of W antennas using sub-band multiplexing; Figure 4 shows a flow chart of the preamble and/or data transmission using sub-band multiplexing; Figure 5 The block diagram showing the transmitter unit and the two receiver units; Figure 6 shows the block diagram of the transmission (TX) space processor implementing the Time Transmission Diversity (STTD) plan; Figure 7A shows the TX space processor implementing the Wassey-STTD plan Figure 7B shows the block diagram of the Wassey-STTD encoder; and Figure 8 shows the block diagram of the OFDM modulator.