Abstract:
A method, apparatus and system for transmitting signal, the method includes: using the weighting factor sequence, processing weighting repeating modulation for the basic cell block mapped by the data symbol block at the sending end, and obtaining a plurality of the repeating cell blocks corresponding to the said basic cell block; the sending end maps each repeating cell block to the appointed time-frequency position respectively, then sends the signals in the said time-frequency position; and the receiving end demodulates the plurality of data symbol blocks from the blocks, and incorporates the plurality of data symbol blocks; the said receiving end demodulates the incorporated data symbol blocks, and generates the received data. This scheme can be called for short as the block repeating spread diversity transmission technology, it is based on the information symbol in the time-frequency domain two-dimensional grid point. This scheme doesn&#39;t restrict the modulating signal generation manner at bottom, it can form a new multiple address/multiple path transmission scheme, and can be incorporated with the other key technologies in the existing mobile communication.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Priority is claimed with respect to Chinese patent application No. 200710063115.5 filed on Jan. 26, 2007, the disclosure of which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to signal transmission technology, and in particular, to a method, an apparatus and a communication system for broadband wireless signal transmission in a time-frequency domain two-dimensional space. 
     BACKGROUND OF THE INVENTION 
     In the existing wireless communication system, there exist two types of signal transmissions including: downlink transmission, where a base station sends a signal and a terminal receives and demodulates the signal; and uplink transmission, where a terminal sends a signal and a base station receives and demodulates the signal. 
     In the downlink transmission, in order to send data to a plurality of terminal users simultaneously in a certain period of time, a base station needs to employ such a resource allocation mode that the bandwidth and time resources of the system can be shared by the data of the plurality of users within this period of time, and the data of the plurality of users can be sent over the system bandwidth by data multiplexing in this period of time. This mode is referred to as a downlink multi-user data multiplexing mode. 
     In the uplink transmission, a plurality of terminal users, which lie in different areas covered by cell signals, with the distances from the terminal users to the base station being different from each other, may need to send data to the base station and communicate with the base station in a certain period of time. Thus, in this period of time, the bandwidth and time resources of the system are shared by the plurality of terminal users, and by way of resource scheduling, the bandwidth and time resources of the system are allocated to each of the users in a certain approach, so that the data of the plurality of terminal users may be sent to the base station. This mode is referred to as an uplink multiple access mode. 
     Generally, the downlink multi-user data multiplexing mode and the uplink multiple access mode may be called collectively as an uplink and downlink multiple access mode. 
     With respect to the uplink and downlink multiple access mode, three types of basic modes including Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CMDA), as well as the combination thereof, are usually employed. In the TDMA mode, the sending time period is divided into a plurality of small time slices, each of which may be separately allocated to a terminal user and other users cannot use the resource in this time slice simultaneously, that is, a single user occupies all the system bandwidth in the time slice. In the FDMA mode, system bandwidth resource is divided into a plurality of narrower frequency bands, each of which is occupied separately by a single user. In the CDMA mode, each user extends information over the whole frequency band by using a specific code sequence, a plurality of users occupy the same time and bandwidth resources in the system, and different users are separated by using different spread spectrum code sequences. In the first generation mobile communication system, the FDMA mode is employed, while in the second generation and the third generation mobile communication systems, the TDMA and CDMA modes are employed. 
     In the future broadband wireless communication system, with the increase of bandwidth, the multipath interference on a wireless channel will be increased significantly. If the traditional multiple access mode, such as the TDMA or CDMA mode, is still employed, the multipath interference on a signal caused by the bandwidth increase may result in serious inter-symbol interference because of the time delay spread in the wireless channel and the relatively narrow symbol width of a high-speed information stream, thereby the signal demodulation performance may be lowered. An equalization method may be employed to overcome such multipath interferences. Because of the large number of multipaths in a broadband system, and sufficient taps of a filter, sufficient training symbols, and sufficient training time are required for the employment of a traditional time domain equalization, the complexity of the equalization algorithm is increased greatly, thus the complexity of system implementation is increased, and the system performance is lowered. 
     To alleviate the inter-symbol interference on broadband wireless communication signals and avoid the complex equalizer, it is proposed in the industry to employ an Orthogonal Frequency Division Multiplexing (OFDM) mode to improve the performance of signal demodulation. The OFDM mode is one type of the FDMA mode. However, in the traditional FDMA technology, a frequency band is divided into a number of disjoint sub-frequency bands for transmitting data streams in parallel, and an enough guard frequency band should be reserved between two adjacent sub-channels. In an OFDM system, however, the frequency spectrums of the sub-channels are allowed to overlap with each other because of the orthogonality between sub-carriers. Therefore, compared with the conventional FDMA system, the OFDM system may, on one hand, utilize maximally the frequency spectrum resources, and on the other hand, employ a fast algorithm of Discrete Fourier Transform. 
     In the OFDM system, serial-to-parallel conversion is performed on a high-speed data stream, so that the duration time of continuous data symbols on each sub-carrier is increased relatively, thus the inter-symbol interference caused by time dispersion of a wireless channel may be effectively reduced, and the complexity of equalization in a receiver may be lowered. The receiver may easily process a signal through frequency domain equalization. 
     The generation of an OFDM signal is shown in  FIG. 1 . If OFDM symbols are employed, a plurality of orthogonal sub-carriers may be employed for data transmission, and therefore different users may occupy different sub-carriers, so that the multi-user multiplexing and multiple access may be implemented. However, at the same time, the OFDM multiple access mode also has disadvantages. When a pure OFDM system is applied to a cellular mobile system, if the cellular mobile system operates in a co-frequency networking mode, relatively large interference exists between the cells, because when the users of different cells send and receive data by using the same sub-carrier, the signals sent and received by the terminal users of adjacent cells may interfere with each other. Especially at the edge of a cell, a terminal of the cell is near to other cells and the signals coming from other cells are relatively strong, when the terminal receives and sends data, serious mutual interference may be generated between the signals of adjacent cells, so that the communication performance of the terminal at the cell edge is degraded drastically. 
     In order to avoid signal interference between adjacent cells in the case of co-frequency networking, related improved OFDM solutions are put forward. The main solution is a mode combining CDMA and OFDM. At present, there are mainly three multiple access modes combining CDMA and OFDM, which are respectively referred to as: Multi-Carrier CDMA (MC-CDMA) mode, Multi-Carrier Direct-Sequence CDMA (MC-DS-CDMA) mode, and Orthogonal Frequency Code Division Multiple Access (OFCDMA) mode with time-frequency domain two-dimensional spread spectrum and combining OFDM. 
     The generation of an MC-CDMA signal is shown in  FIG. 2A . In the MC-CDMA shown in  FIG. 2A , spread spectrum processing is first performed on each symbol in a data stream, with the length of spread spectrum code being N, and then the spread spectrum processed data is mapped to N sub-carriers modulated by the OFDM. Compared with the OFDM mode, the MC-CDMA multiple access mode is advantageous in that frequency diversity may be utilized and interference between adjacent cells of co-frequency networking may be reduced. 
     The generation of an MC-DS-CDMA signal is shown in  FIG. 2B , and is different from the generation of the MC-CDMA signal. In the MC-DS-CDMA mode, the spread spectrum processing on each symbol is performed over each sub-carrier, that is, spread spectrum is carried out in terms of time, so that a time diversity gain may be obtained, and interference between adjacent cells of co-frequency networking may also be reduced. 
     Based on the above multiple access modes combining CDMA and OFDM, there also exists in the prior art the OFCDMA mode with time-frequency domain two-dimensional spread spectrum and combining OFDM. 
     All of the above solutions of MC-CDMA, MC-DS-CDMA, and OFDM with the time-frequency domain two-dimensional spread spectrum combine CDMA and OFDM. Through these modes combining CDMA and OFDM, a certain diversity gain and anti-multiple access interference capability can be achieved, and multi-cell co-frequency networking may be easily implemented. However, all these solutions are commonly disadvantageous in that: the allocating and scheduling of resources and the controlling of interferences are not flexible and convenient, the elimination of the multiple access interference at a receiving end costs greatly (because the information of a sending end needs to be obtained, and the receiving process is complex), and the fading and interference of a channel may result in a burst error of some symbols, and so on. 
     SUMMARY OF THE INVENTION 
     The invention provides a method, an apparatus and a system for transmitting a signal, to improve the flexibility of the allocating and scheduling of resources and the controlling of interferences, and further improve the system performance and lower the complexity of receiving process. 
     A method for sending a signal, including: 
     performing weighting and repeating modulation on a basic block unit obtained by mapping a data block, by using a weighting factor sequence, to obtain a plurality of repeated block units corresponding to the basic block unit; and 
     mapping each of the repeated block units to a specified time-frequency location, and sending a signal at the specified time-frequency location. 
     A method for sending a signal, including: 
     performing weighting and repeating modulation on a generated data block by using a weighting factor sequence, to obtain a plurality of repeated data blocks corresponding to the data block; 
     modulating and mapping the plurality of repeated data blocks to physical resource blocks respectively to generate repeated block units, and mapping each of the repeated block units to a specified time-frequency location; and 
     sending a signal at the specified time-frequency location. 
     A method for receiving a signal, including: 
     receiving a signal, and demodulating repeated block units at a plurality of specified time-frequency locations to obtain a plurality of data blocks; 
     combining the plurality of data blocks; and 
     demodulating the combined data blocks to generate received data. 
     A method for receiving a signal, including: 
     receiving a signal, and adjusting repeated block units at a plurality of specified time-frequency locations to time-frequency units at the same location; 
     performing channel estimation according to pilot symbols, and combining each repeated block unit according to the channel estimation; 
     demodulating the repeated block units weighted and combined, to obtain a data block; and 
     demodulating the data block, to generate received data. 
     A method for transmitting a signal, including: 
     performing, by a sending end, weighting and repeating modulation on a basic block unit obtained by mapping a data block, by using a weighting factor sequence, to obtain a plurality of repeated block units corresponding to the basic block unit; 
     mapping, by the sending end, each of the repeated block units to a specified time-frequency location, and sending a signal at the time-frequency location; and 
     demodulating, by a receiving end, the plurality of repeated block units received to obtain a plurality of data blocks, and combining the plurality of data blocks; and 
     demodulating, by the receiving end, the combined data blocks to generate received data. 
     A method for transmitting a signal, including: 
     performing, by a sending end, weighting and repeating modulation on a basic block unit obtained by modulating and mapping a data block, by using a weighting factor sequence, to obtain a plurality of repeated block units corresponding to the basic block unit; 
     modulating and mapping each of the repeated block units to a specified time-frequency location; 
     sending a signal at the specified time-frequency location; and 
     receiving, by a receiving end, the signal, and demodulating the repeated block units at a plurality of specified time-frequency locations to obtain the corresponding data blocks; 
     combining, by the receiving end, the obtained data blocks; and 
     demodulating, by the receiving end, the combined data blocks to generate received data. 
     A method for transmitting a signal, including: 
     performing, by a sending end, weighting and repeating modulation on a generated data block by using a weighting factor sequence, to obtain a plurality of repeated data blocks corresponding to the data block; 
     modulating and mapping the plurality of repeated data blocks to physical resource blocks respectively to generate repeated block units, and modulating and mapping each of the repeated block units to a specified time-frequency location; 
     sending a signal at the specified time-frequency location; and 
     receiving, by a receiving end, the signal, and demodulating the repeated block units at a plurality of specified time-frequency locations to obtain the corresponding data blocks; 
     combining, by the receiving end, the obtained data blocks; and 
     demodulating, by the receiving end, the combined data blocks to generate received data. 
     A method for transmitting a signal, including: 
     performing, by a sending end, weighting and repeating modulation on a basic block unit obtained by modulating and mapping a data block, by using a weighting factor sequence, to obtain a plurality of repeated block units corresponding to the basic block unit; 
     modulating and mapping each of the repeated block units to a specified time-frequency location; 
     sending a signal at the specified time-frequency location; and 
     receiving, by a receiving end, the signal, and adjusting the repeated block units at a plurality of specified time-frequency locations to the same time-frequency location; 
     performing channel estimation according to pilot symbols, and combining the adjusted repeated block units according to the channel estimation; 
     demodulating the combined repeated block units to obtain a data block; and 
     demodulating the data block to generate received data. 
     A method for transmitting a signal, including: 
     performing, by a sending end, weighting and repeating modulation on a generated data block by using a weighting factor sequence, to obtain a plurality of repeated data blocks corresponding to the data block; 
     modulating and mapping the plurality of repeated data blocks to physical resource blocks respectively to generate repeated block units, and modulating and mapping each of the repeated block units to a specified time-frequency location; 
     sending a signal at the specified time-frequency location; and 
     receiving, by a receiving end, the signal, and adjusting the repeated block units at a plurality of specified time-frequency locations to the same time-frequency location; 
     performing channel estimation according to pilot symbols, and combining the adjusted repeated block units according to the channel estimation; 
     demodulating the combined repeated block units to obtain a data block; and 
     demodulating the data block to generate received data. 
     An apparatus for sending a signal, including: 
     a first modulation unit, adapted to partition and modulate data to be sent, to generate data blocks; 
     a second modulation unit, adapted to modulate and map the data block to a physical resource block, to generate a basic block unit; 
     a third modulation unit, adapted to perform weighting and repeating modulation on the basic block unit by using a weighting factor sequence, map a plurality of repeated block units obtained by performing weighting and repeating modulation on the basic block unit to specified time-frequency locations respectively; and 
     a communication unit, adapted to send a signal at the specified time-frequency location and receive a signal. 
     An apparatus for sending a signal, including: 
     a first modulation unit, adapted to partition and modulate data to be sent, to generate data blocks; 
     a second modulation unit, adapted to perform weighting and repeating modulation on the generated data block by using a weighting factor sequence, to obtain a plurality of repeated data blocks corresponding to the data block; 
     a third modulation unit, adapted to modulate and map the plurality of repeated data blocks to physical resource blocks respectively, to generate repeated block units, and map each of the repeated block units to a specified time-frequency location; and 
     a communication unit, adapted to send a signal at the specified time-frequency location and receive a signal. 
     An apparatus for receiving a signal, including: 
     a communication unit, adapted to send or receive a signal; 
     a first demodulation unit, adapted to demodulate repeated block units at a plurality of specified time-frequency locations to obtain a plurality of data blocks after receiving the signal; 
     a second demodulation unit, adapted to combine the plurality of data blocks; and 
     a third demodulation unit, adapted to demodulate the combined data blocks to generate received data. 
     An apparatus for receiving a signal, including: 
     a communication unit, adapted to send or receive a signal; 
     an adjusting unit, adapted to adjust repeated block units at a plurality of specified time-frequency locations to time-frequency units at the same location after receiving the signal; 
     a first demodulation unit, adapted to weight each of the repeated block units using pilot symbols, and combine the weighted repeated block units; 
     a second demodulation unit, adapted to demodulate the combined repeated block units to obtain a data block; and 
     a third demodulation unit, adapted to demodulate the data block to generate received data. 
     A communication system, including: 
     a first apparatus, adapted to perform weighting and repeating modulation on a basic block unit obtained by mapping a data block, by using a weighting factor sequence, to form a plurality of repeated block units, and after mapping each of the repeated block units to a specified time-frequency location, send a signal at the time-frequency location; 
     a second apparatus, adapted to receive the signal sent by the first apparatus, demodulate a plurality of repeated block units to obtain a plurality of data blocks, combine the plurality of data blocks, and demodulate the combined data blocks to generate received data. 
     A communication system, including: 
     a first apparatus, adapted to perform weighting and repeating modulation on a generated data block by using a weighting factor sequence, to obtain a plurality of repeated data blocks corresponding to the data block; modulate and map the plurality of repeated data blocks to physical resource blocks respectively to generate repeated block units, and after mapping each of the repeated block units to a specified time-frequency location, send a signal at the specified time-frequency location; 
     a second apparatus, adapted to receive the signal sent by the first apparatus, demodulate a plurality of repeated block units to obtain a plurality of data blocks, combine the plurality of data blocks, and demodulate the combined data blocks to generate received data. 
     A communication system, including: 
     a first apparatus, adapted to perform weighting and repeating modulation on a basic block unit obtained by mapping a data block, by using a weighting factor sequence, to form a plurality of repeated block units; and after mapping each of the repeated block units to a specified time-frequency location, send a signal at the time-frequency location; 
     a second apparatus, adapted to receive the signal sent by the first apparatus, adjust the repeated block units at a plurality of specified time-frequency locations to time-frequency units at the same location, weight and combine the repeated block units by using pilot symbols, demodulate the combined block units to obtain a data block, and then demodulate the data block to generate received data. 
     A communication system, including: 
     a first apparatus, adapted to perform weighting and repeating modulation on a generated data block by using a weighting factor sequence, to obtaine a plurality of repeated data blocks corresponding to the data block; modulate and map the plurality of repeated data blocks to physical resource blocks respectively to generate block units, and after mapping each of the block units to a specified time-frequency location, send a signal at the specified time-frequency location; and 
     a second apparatus, adapted to receive the signal sent by the first apparatus, adjust a plurality of repeated block units at the specified time-frequency locations to time-frequency units at the same location, weight the repeated block units by using pilot symbols, combine the weighted repeated block units, demodulate the combined repeated block units to obtain a data block, and demodulate the data block to generate received data. 
     Since the invention employs information transmission based on the block repeat, as compared with the existing OFDM-type broadband transmission technology, the technical solution of the invention may coordinate the relation between system resource and system performance, treat the interferences between multi-cell and multi-user signals better, implement broadband co-frequency networking more easily, and improve system capacity and performance. 
     As compared with the existing three technical solutions combining CDMA and OFDM, such as MC-CDMA, MC-DS-CDMA and time-frequency domain two-dimensional spread spectrum OFDM, the block repeat transmission solution may cooperate with the packet transmission mechanism better to improve the system performance and simplify the design and implementation of the system; block repeat transmission solution is flexible and convenient for the allocation and scheduling of resources and the controlling of interferences, and can easily balance the advantages of scheduling and diversity; in the block repeat transmission solution, less cost is needed to eliminate multi-access interference at a receiving end (that is, there are only a few requirements on the information of the sending end, and the complexity of receiving process is low); block repeat transmission may better restrain the degradation of system performance caused by channel fading and burst interference. 
     Because block repeat transmission solution is implemented based on the repeating of a basic physical resource block, and the modulation and multi-access mode of a lower layer is not limited, such a block repeat division multiplex (BRDM) solution may also be combined with various basic multi-access modes, thus forming various multi-access/multiplex solutions. For example, the combination of the block repeat division multiplex and Interleaved FDMA (IFDMA) may obtain a BR-IFDMA multi-access mode; the combination of the block repeat division multiplex and DFT-Spread OFDM (DFT-S-OFDM) may obtain a BR-DFT-S-OFDM mode (usually, both IFDMA and DFT-S-OFDM may be referred to as Single-Carrier FDMA (SC-FDMA), so the combination of BRDM with IFDMA and DFT-S-OFDM may also be referred to as a BR-SC-FDMA mode). 
     The technical solution of the invention may be referred for short as block repeat spread diversity transmission technology, which is a transmission solution based on information symbols on time-frequency domain two-dimensional grid points. Actually, the solution performs multi-symbol repeat on a time-frequency resource block within the whole available time-frequency domain resources, thereby implementing the spread repeat transmission of a signal; while a suitable diversity technology may be employed on the receiving end for multi-symbol combining. Through the solution of the invention, various interference problems in the broadband mobile communication may be effectively overcome. Because different users or channels may be distinguished by selected weighting factor sequences, the multiplex transmission of a plurality of users or multiple signals may be implemented on the same time-frequency resource block through the solution of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing the generation and processing of an OFDM signal in the prior art; 
         FIG. 2A  is a schematic diagram showing the generation of an MC-CDMA signal in the prior art; 
         FIG. 2B  is a schematic diagram showing the generation of an MC-DS-CDMA signal in the prior art; 
         FIG. 3  is a schematic diagram showing channel resources in an OFDM modulation mode in the prior art; 
         FIG. 4  is a schematic diagram showing a physical resource block in an OFDM modulation mode in the prior art; 
         FIG. 5  is a schematic diagram showing the arrangement of the pilot and data in a physical resource block in the prior art; 
         FIG. 6  is a schematic diagram showing the block repeat transmission mode for a single user according to an embodiment of the invention; 
         FIG. 7  is a schematic diagram showing the block repeat transmission mode for two users according to an embodiment of the invention; 
         FIG. 8A  is a schematic diagram showing the structure of a communication apparatus for sending a signal according to an embodiment of the invention; 
         FIG. 8B  is a flow chart of generating and sending a signal via three-stage modulation according to an embodiment of the invention; 
         FIG. 9A  is a schematic diagram of the structure of another communication apparatus for sending a signal according to an embodiment of the invention; 
         FIG. 9B  is another flow chart of generating and sending a signal via three-stage modulation according to an embodiment of the invention; 
         FIG. 10  is a schematic diagram showing the structure of a base station according to an embodiment of the invention; 
         FIG. 11A  is a schematic diagram showing the structure of a communication apparatus for receiving and processing a signal according to an embodiment of the invention; 
         FIG. 11B  is a flow chart of generating received data via three-stage demodulation according to an embodiment of the invention; 
         FIG. 12A  is a schematic diagram showing the structure of another communication apparatus for receiving and processing a signal according to an embodiment of the invention; 
         FIG. 12B  is another flow chart of generating received data via three-stage demodulation according to an embodiment of the invention; 
         FIG. 13A  and  FIG. 13B  each are schematic diagrams showing the structure of a communication apparatus according to an embodiment of the invention; 
         FIG. 14  is a schematic diagram showing the structure of a block repeat communication system according to an embodiment of the invention; 
         FIG. 15A ,  FIG. 15B ,  FIG. 15C  and  FIG. 15D  each are flow charts of transmitting a signal between a base station and a mobile terminal according to an embodiment of the invention; and 
         FIG. 16  is a schematic diagram showing the block repeat transmission pilot orthogonal multiplexing according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The information transmission in an embodiment of the present invention is based on the repeat transmission of a basic physical resource block, multiplexing and multiple access, which are called for short as block repeat transmission solution (i.e. Block Repeat (BR)), and Block Repeat Division Multiplex (BRDM)/Block Repeat Division Multiple Access (BRDMA) solution, as well as block repeat spread diversity transmission technology. 
     Because the multiple access mode in the embodiment of the present invention is implemented based on the repeat of a basic physical resource block, the modulation multiple access mode of a lower layer is not limited. Such a block repeat mode may be combined with various multiple access modes to form various composite solutions. For example, the combination with OFDM may be called for short as Block Repeat OFDM (BR-OFDM)/Block Repeat OFDMA (BR-OFDMA); and the combination with SC-FDMA forms a BR-SC-FDMA mode. 
     Detailed illustration will be given below by taking the combination of the block repeat transmission mode and OFDM (i.e. BR-OFDM) as an example. 
     One specific example of the allocation and use of channel resources in the OFDM modulation mode is shown in  FIG. 3 , where a physical resource block (PRB) is a basic unit used for mapping transmission data to a physical layer, and 9 PRBs are allocated to users  1 - 6 . The structure of each PRB is shown in  FIG. 4 . 
     In the OFDM modulation mode, a channel resource is of a time-frequency two-dimensional structure.  FIG. 4  shows an OFDM physical time-frequency resource block unit, which occupies a part of the whole OFDM time-frequency resources. The physical time-frequency resource block unit contains N T  OFDM symbols in time domain, and contains N F  OFDM sub-carriers in frequency domain, thus the physical time-frequency resource block unit contains totally N=N T ×N F  symbols, and the symbols (including data symbols and pilot symbols) in the physical time-frequency resource block unit may be represented as: 
     
       
         
           
             
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     Each symbol in the physical time-frequency resource block unit may be a pilot symbol or a data symbol. The whole OFDM time-frequency resources contain one or more physical time-frequency resource block units. In each PRB, the respective pilot symbols are provided for channel estimation. A specific example of a PRB and pilot and data thereof are shown in  FIG. 5 . 
     The minimum unit and change granularity of transmission rate depends on the size of the basic PRB. To design the size of the basic PRB, it may be considered that the time domain width of the PRB is correlated to the coherent time of a frequency and time doubly-selective channel, while the frequency domain width of the PRB is correlated to the coherent frequency. Thus, a compromise between the design difficulty of pilot symbols and the complexity of the equalization algorithm and channel estimation may be effectively selected. 
     In the embodiment, an example of BR-OFDM for a single user is shown in  FIG. 6 , where a Block Unit (BU) is the basic unit for block repeat, one BU is repeatedly transferred for 6 times, resulting so called repeated block units BU 1 , BU 2 , . . . , and BU 6 , that is, 6 BUs transfer the same data. In the embodiment, the block repeat times are defined as a block repeat factor (RF), and in the specific example shown in  FIG. 6 , RF=6. The repeated block units in  FIG. 6  are arranged in a synthesized time-frequency domain direction. In other embodiments, these 6 BUs may also be arranged in a horizontal direction, a vertical direction or an oblique direction. 
     Each repeated block unit is weighted via a weighting factor, and a block repeat weighting factor sequence (also referred to as repeat code RC) (C 0 C 1  . . . C RF-1 ) is provided by the sending end. During the block repeat transmission, a BU is weighted and repeated, and mapped to a specified time-frequency location. In the case of a single user, the same weighting factor or different weighting factors may be used for each repeated block unit; and if the same weighting factor (i.e., all the members of the weighting factor sequence is 1) is used, the demodulation may be simplified. 
     It is assumed that the data symbols (L symbols) to be transferred by one BU are represented as:
 
d=[d 0 ,d 1 , . . . , d L-1 ].
 
     The data d is mapped to the BU according to a certain correspondence relationship. The symbols (with a total number of N=N T ×N F , including data symbols and pilot symbols) in one BU may be represented as: 
     
       
         
           
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                 ] 
               
               . 
             
           
         
       
     
     A time domain signal corresponding to the BU may be represented as s UB (t), with both the time and frequency of the signal being limited within one BU. A BU adjusted to a specified time-frequency location (t i , f i ), which is equivalent to a BU subjected to time shift (t i ) and frequency shift (f i ) may be represented as s UB (t−t i )e j2πf     i     (t−t     i     ) . 
     It is assumed that the time-frequency location for block repeat is (t i , f i ), wherein, i=0, 1, . . . , RF−1. During the block repeat transmission, a BU is weighted and repeated (with a block repeat weighting factor sequence C 0 C 1  . . . C RF-1 ), and mapped to a specified time-frequency location, and the signal after block repeat may be represented as: 
     
       
         
           
             
               
                 
                   
                     
                       s 
                       
                         Block 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         Repeat 
                       
                     
                     ⁡ 
                     
                       ( 
                       t 
                       ) 
                     
                   
                   = 
                     
                   ⁢ 
                   
                     
                       
                         C 
                         0 
                       
                       ⁢ 
                       
                         
                           s 
                           UB 
                         
                         ⁡ 
                         
                           ( 
                           
                             t 
                             - 
                             
                               t 
                               0 
                             
                           
                           ) 
                         
                       
                       ⁢ 
                       
                         ⅇ 
                         
                           j 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           π 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             
                               f 
                               0 
                             
                             ⁡ 
                             
                               ( 
                               
                                 t 
                                 - 
                                 
                                   t 
                                   0 
                                 
                               
                               ) 
                             
                           
                         
                       
                     
                     + 
                   
                 
               
             
             
               
                 
                     
                   ⁢ 
                   
                     
                       
                         C 
                         1 
                       
                       ⁢ 
                       
                         
                           s 
                           UB 
                         
                         ⁡ 
                         
                           ( 
                           
                             t 
                             - 
                             
                               t 
                               1 
                             
                           
                           ) 
                         
                       
                       ⁢ 
                       
                         ⅇ 
                         
                           j 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           π 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             
                               f 
                               1 
                             
                             ⁡ 
                             
                               ( 
                               
                                 t 
                                 - 
                                 
                                   t 
                                   1 
                                 
                               
                               ) 
                             
                           
                         
                       
                     
                     + 
                     … 
                     + 
                   
                 
               
             
             
               
                 
                     
                   ⁢ 
                   
                     
                       C 
                       
                         RF 
                         - 
                         1 
                       
                     
                     ⁢ 
                     
                       
                         s 
                         UB 
                       
                       ⁡ 
                       
                         ( 
                         
                           t 
                           - 
                           
                             t 
                             
                               RF 
                               - 
                               1 
                             
                           
                         
                         ) 
                       
                     
                     ⁢ 
                     
                       ⅇ 
                       
                         j 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         π 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           
                             f 
                             
                               RF 
                               - 
                               1 
                             
                           
                           ⁡ 
                           
                             ( 
                             
                               t 
                               - 
                               
                                 t 
                                 
                                   RF 
                                   - 
                                   1 
                                 
                               
                             
                             ) 
                           
                         
                       
                     
                   
                 
               
             
             
               
                 
                   = 
                     
                   ⁢ 
                   
                     
                       ∑ 
                       
                         i 
                         = 
                         0 
                       
                       
                         RF 
                         - 
                         1 
                       
                     
                     ⁢ 
                     
                       
                         C 
                         i 
                       
                       ⁢ 
                       
                         
                           s 
                           UB 
                         
                         ⁡ 
                         
                           ( 
                           
                             t 
                             - 
                             
                               t 
                               i 
                             
                           
                           ) 
                         
                       
                       ⁢ 
                       
                         
                           ⅇ 
                           
                             
                                 
                             
                             ⁢ 
                             
                               j 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               2 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               π 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 
                                   f 
                                   i 
                                 
                                 ⁡ 
                                 
                                   ( 
                                   
                                     t 
                                     - 
                                     
                                       t 
                                       i 
                                     
                                   
                                   ) 
                                 
                               
                             
                           
                         
                         . 
                       
                     
                   
                 
               
             
           
         
       
     
     A schematic diagram illustrating an example of the BR-OFDM for a plurality of users is shown in  FIG. 7 . In this example, two users occupy the same time-frequency channel resource for block repeat transmission. During the multi-user block repeat transmission, each user sends a signal according to the BR-OFDM for a single-user; however, since the plurality of users occupy the same time-frequency channel resource, the block repeat weighting factor sequence C 0 C 1  . . . C RF-1  (repeat code RC) for each of the users is different. The receiving end separates the signals occupying the same time-frequency resource according to the different repeat codes. In  FIG. 7 , along the direction of power/repeat code axis, the upper part is user  1  and the lower part is user  2 . When the weighting factor sequences of all the users are orthogonal to each other, the size of block repeat factor determines the number of user signals that may remain fully orthogonal to each other in a cell. 
     In the above embodiments, the term “user” is employed to express the concept of multiple signals. In practice, the “user” may be a terminal user device that conducts wireless communication with a base station using a single signal. However, in a broader sense, the “user” refers to each of signals that may be superposed on the same time-frequency channel resource. From the viewpoint of a terminal, each terminal device may transmit information to a base station via multiple signals superposed on the same time-frequency channel resource, and signals of a plurality of terminal devices may be naturally superposed during transmission over an air interface, while the base station may distinguish and demodulate each of the signals. From the viewpoint of a base station, multiple signals on the same time-frequency channel resource may belong to different terminal devices, and the terminal devices only need to demodulate their own one or more signals from the received superposed signal. 
     In a cell, multiple signals that may be multiplexed over a time-frequency resource block may be distinguished via a group of labels, each of which may correspond to one weighting factor sequence. Of course, when the base station device has a space division multiple access capability, one weighting factor sequence may even be allocated to a plurality of terminal users in the cell. 
     In the present embodiment, the repeated block units may be generated in various modes at the sending end of data. For example, after a generated data block (DB) is modulated and mapped to a PRB to generate a BU, weighting and repeating modulation (or referred to as block repeat modulation) is performed on the BU using a weighting factor sequence to obtain a plurality of repeated block units corresponding to each BU; or weighting and repeating modulation is performed on a generated data block using a weighting factor sequence to obtain a plurality of repeated data blocks corresponding to the generated data block, then each of the repeated data blocks is mapped as a repeated block unit. 
     In the present embodiment, a sending signal is generated from the data to be sent (which is subjected to channel coding, rate adaption and combination mapping) via three-stage modulation. In an implementing mode of the three-stage modulation, the three stages of modulations include sending data modulation at the first stage, BU modulation at the second stage, and block repeat modulation at the third stage.  FIG. 8A  shows an apparatus that can implement such three-stage modulation, and the apparatus includes: a first modulation unit  80 , a second modulation unit  81 , a third modulation unit  82  and a communication unit  83 . The first modulation unit  80  is adapted to modulate the data to be sent to generate a data block; the second modulation unit  81  is adapted to accomplish the BU modulation to generate a basic block unit; the third modulation unit  82  is adapted to accomplish the block repeat modulation to generate repeated block units, and map the repeated block units to specified time-frequency locations; and the communication unit  83  is adapted to send a signal at the specified time-frequency location and receive a signal. The apparatus may be a mobile terminal or a base station.  FIG. 8B  shows an example of the process flow for sending a signal by the apparatus, and the process flow includes the following. 
     Process  800 : The data to be sent is modulated (i.e. subjected to the sending data modulation at the first stage), that is, the data to be sent is modulated and partitioned into blocks, to generate data blocks (DBs). 
     In the Process  800 , the data modulation refers to common digital modulation on the data to be sent, for example, Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), 16 QAM and 64QAM, etc.; and the partitioning process refers to determining the data transmitted by each BU according to the size of the BU. Given that the data to be transmitted by one BU includes L data symbols, the data block generated by the data modulation at the first stage may be represented as:
 
d=[d 0 ,d 1 , . . . , d L-1 ].
 
     Process  801 : The BU modulation (i.e. the second stage of modulation) is performed, that is, the data block is modulated and mapped to a PRB to generate a basic block unit. 
     In the Process  801 , the data block d is mapped to a physical resource BU according to a certain correspondence relationship, and other symbols such as a pilot are inserted into the physical resource BU. In the case of a system employing the OFDM mode, the BU is a time-frequency resource unit in the time-frequency domain, and is formed of N T  symbols in the time domain and N F  carriers in the frequency domain. The symbols (with a total number of N=N T ×N F , including the data symbols and the pilot symbols) in one BU may be represented as: 
     
       
         
           
             s 
             = 
             
               
                 [ 
                 
                   
                     
                       
                         s 
                         
                           0 
                           , 
                           0 
                         
                       
                     
                     
                       
                         s 
                         
                           0 
                           , 
                           1 
                         
                       
                     
                     
                       … 
                     
                     
                       
                         s 
                         
                           0 
                           , 
                           
                             
                               N 
                               F 
                             
                             - 
                             1 
                           
                         
                       
                     
                   
                   
                     
                       
                         s 
                         
                           1 
                           , 
                           0 
                         
                       
                     
                     
                       
                         s 
                         
                           1 
                           , 
                           1 
                         
                       
                     
                     
                       … 
                     
                     
                       
                         s 
                         
                           1 
                           , 
                           
                             
                               N 
                               F 
                             
                             - 
                             1 
                           
                         
                       
                     
                   
                   
                     
                       ⋮ 
                     
                     
                       ⋮ 
                     
                     
                       … 
                     
                     
                       ⋮ 
                     
                   
                   
                     
                       
                         s 
                         
                           
                             
                               N 
                               T 
                             
                             - 
                             1 
                           
                           , 
                           0 
                         
                       
                     
                     
                       
                         s 
                         
                           
                             
                               N 
                               T 
                             
                             - 
                             1 
                           
                           , 
                           1 
                         
                       
                     
                     
                       … 
                     
                     
                       
                         s 
                         
                           
                             
                               N 
                               T 
                             
                             - 
                             1 
                           
                           , 
                           
                             
                               N 
                               F 
                             
                             - 
                             1 
                           
                         
                       
                     
                   
                 
                 ] 
               
               . 
             
           
         
       
     
     Given all the symbols s corresponding to the BU, a time domain signal of the BU may be generated according to the OFDM mode. The time domain signal may be represented as s UB (t), with both the time and frequency of the time domain signal being limited within one BU. 
     Each BU may have its dedicated pilot, and is a self-contained PRB that may be demodulated independently. That is, the receiving end may perform channel estimation via the pilot symbols in the BU and perform coherent demodulation on the signals of the BU. For each user, both the pilot symbols in each BU and the time-frequency grid locations occupied by the pilot symbols are known by the sending end and the receiving end. 
     Process  802 : The block repeat modulation (i.e. the third stage of modulation) is performed, that is, the weighting and Block repeat (BR) modulation is performed on each basic block unit to generate a plurality of repeated block units, which are in turn mapped to specified time-frequency locations respectively. 
     The time-frequency locations corresponding to all the repeated block units are arranged continuously or discontinuously in the time domain; or, the time-frequency locations corresponding to all the repeated block units are arranged continuously or discontinuously in the frequency domain; or, the time-frequency locations corresponding to all the repeated block units are arranged continuously or discontinuously in the time and frequency domains. A specific arrangement pattern of the time-frequency locations may be selected from various modes including sequential arrangement in the time domain direction, sequential arrangement in the frequency domain direction, arrangement in the synthesized time-frequency domain direction, and arrangement in an oblique direction, taking a time-frequency resource block as a basic unit. The specific mode may be predetermined and known by both the sending end and the receiving end. Thus, an entity for resource allocation is generally provided in the network on the base station side. When data transmission is required between a certain terminal device and the base station, the resource allocation entity allocates resources to the terminal and appoints a reference mark of the time-frequency location to which the repeated block unit is mapped, and the terminal and the base station may know the time-frequency location to which each repeated block unit is to be mapped according to the reference mark and the predetermined arrangement pattern. However, the “block” in the embodiment is not limited to be of a rectangular shape. 
     A signal after the BU modulation is represented as s UB (t), with both the time and frequency of the signal being limited within one BU. A BU adjusted to a specified time-frequency location (t i , f i ), which is equivalent to a BU subjected to time shift (t i ) and frequency shift (f i ), may be represented as s UB (t−t i )e j2πf     i     (t−t     i     ) . 
     It is assumed that the time-frequency location for block repeat is (t i , f i ), wherein, i=0, 1, . . . , RF−1. During the block repeat transmission, a BU is weighted and repeated via block repeat code C 0 C 1  . . . C RF-1 , and mapped to a specified time-frequency location. A signal after the block repeat modulation may be represented as: 
     
       
         
           
             
               
                 
                   
                     
                       s 
                       
                         Block 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         Repeat 
                       
                     
                     ⁡ 
                     
                       ( 
                       t 
                       ) 
                     
                   
                   = 
                     
                   ⁢ 
                   
                     
                       
                         C 
                         0 
                       
                       ⁢ 
                       
                         
                           s 
                           UB 
                         
                         ⁡ 
                         
                           ( 
                           
                             t 
                             - 
                             
                               t 
                               0 
                             
                           
                           ) 
                         
                       
                       ⁢ 
                       
                         ⅇ 
                         
                           j 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           π 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             
                               f 
                               0 
                             
                             ⁡ 
                             
                               ( 
                               
                                 t 
                                 - 
                                 
                                   t 
                                   0 
                                 
                               
                               ) 
                             
                           
                         
                       
                     
                     + 
                   
                 
               
             
             
               
                 
                     
                   ⁢ 
                   
                     
                       
                         C 
                         1 
                       
                       ⁢ 
                       
                         
                           s 
                           UB 
                         
                         ⁡ 
                         
                           ( 
                           
                             t 
                             - 
                             
                               t 
                               1 
                             
                           
                           ) 
                         
                       
                       ⁢ 
                       
                         ⅇ 
                         
                           j 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           π 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             
                               f 
                               1 
                             
                             ⁡ 
                             
                               ( 
                               
                                 t 
                                 - 
                                 
                                   t 
                                   1 
                                 
                               
                               ) 
                             
                           
                         
                       
                     
                     + 
                     … 
                     + 
                   
                 
               
             
             
               
                 
                     
                   ⁢ 
                   
                     
                       C 
                       
                         RF 
                         - 
                         1 
                       
                     
                     ⁢ 
                     
                       
                         s 
                         UB 
                       
                       ⁡ 
                       
                         ( 
                         
                           t 
                           - 
                           
                             t 
                             
                               RF 
                               - 
                               1 
                             
                           
                         
                         ) 
                       
                     
                     ⁢ 
                     
                       ⅇ 
                       
                         j 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         π 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           
                             f 
                             
                               RF 
                               - 
                               1 
                             
                           
                           ⁡ 
                           
                             ( 
                             
                               t 
                               - 
                               
                                 t 
                                 
                                   RF 
                                   - 
                                   1 
                                 
                               
                             
                             ) 
                           
                         
                       
                     
                   
                 
               
             
             
               
                 
                   = 
                     
                   ⁢ 
                   
                     
                       ∑ 
                       
                         i 
                         = 
                         0 
                       
                       
                         RF 
                         - 
                         1 
                       
                     
                     ⁢ 
                     
                       
                         C 
                         i 
                       
                       ⁢ 
                       
                         
                           s 
                           UB 
                         
                         ⁡ 
                         
                           ( 
                           
                             t 
                             - 
                             
                               t 
                               i 
                             
                           
                           ) 
                         
                       
                       ⁢ 
                       
                         
                           ⅇ 
                           
                             
                                 
                             
                             ⁢ 
                             
                               j 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               2 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               π 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 
                                   f 
                                   i 
                                 
                                 ⁡ 
                                 
                                   ( 
                                   
                                     t 
                                     - 
                                     
                                       t 
                                       i 
                                     
                                   
                                   ) 
                                 
                               
                             
                           
                         
                         . 
                       
                     
                   
                 
               
             
           
         
       
     
     In the above representation of the signal, the BU is integrally weighted, and the pilot symbols carries information related to the weighting factor sequence. Therefore, in the case that a dedicated pilot is employed and weighted, the data symbols and pilot symbols in each repeated block unit have the same weighting factor. In this case, the receiving end may demodulate the signal via the channel estimation of the dedicated pilot without knowing the weighting factor sequence in advance. However, it is also possible not to weight the dedicated pilot symbols. 
     In the present Process, the block repeat code C 0 C 1  . . . C RF-1 , is a feature sequence corresponding to a user (or a cell, a channel, etc.), and may be an orthogonal code, a pseudo-random code or other code, and may even be a real random code, which is a code word generated at random in real time, not predetermined. Since the receiving end need not know the weighting factor sequence under the condition that the dedicated pilot is weighted, greater flexibility may be brought about in the implementation of system. 
     Process  803 : A signal at the specified time-frequency location is transmitted. 
     During the block repeat modulation, the modulated data contained in all the repeated block units are exactly the same. The arrangement order and relative position of the modulated data in a repeated block unit may be exactly the same as those in another repeated block unit, or different from those in another repeated block unit by a specified correspondence relationship. 
     In another implementing mode of the three-stage modulation, the stages of modulation include sending data modulation at the first stage, block repeat modulation at the second stage, and BU modulation at the third stage.  FIG. 9A  shows an apparatus that can implement such three stages of modulation, and the apparatus includes: a first modulation unit  90 , a second modulation unit  91 , a third modulation unit  92  and a communication unit  93 . The first modulation unit  90  is adapted to modulate the data to be sent to generate a data block; the second modulation unit  91  is adapted to accomplish block repeat modulation to generate repeated data blocks; the third modulation unit  92  is adapted to accomplish BU modulation, to generate and map repeated block units to specified time-frequency locations; and the communication unit  93  is adapted to send a signal at the specified time-frequency location and receive a signal. The apparatus may be a mobile terminal or a base station.  FIG. 9B  shows an example of the process flow for sending the signal by the apparatus, and the process flow includes the following. 
     Process  900 : The data to be sent is modulated (i.e. subjected to the first stage of modulation), that is, the data to be sent is partitioned and modulated, to generate data blocks. 
     The processing at Process  900  is the same as that at Process  800  in  FIG. 8B . The data block may be represented as: d=[d 0 ,d 1 , . . . , d L-1 ]. 
     Process  901 : The block repeat modulation is performed, that is, the data block is weighted and repeated, to generate a plurality of repeated data blocks:
 
d Block Repeat   (i) =C i d =C i [d 0 ,d 1 , . . . , d L-1 ].
 
     Where, C i  is the weighting factor of the ith repeated data block. 
     Process  902 : The BU modulation is performed, that is, the repeated data blocks are modulated and mapped to repeated block units, which are in turn mapped to specified time-frequency locations. 
     Mapping of a data block d Block Repeat   (i)  to a BU obtains the following s (i) . 
     
       
         
           
             
               s 
               
                 ( 
                 i 
                 ) 
               
             
             = 
             
               
                 [ 
                 
                   
                     
                       
                         s 
                         
                           0 
                           , 
                           0 
                         
                       
                     
                     
                       
                         s 
                         
                           0 
                           , 
                           1 
                         
                       
                     
                     
                       … 
                     
                     
                       
                         s 
                         
                           0 
                           , 
                           
                             
                               N 
                               F 
                             
                             - 
                             1 
                           
                         
                       
                     
                   
                   
                     
                       
                         s 
                         
                           1 
                           , 
                           0 
                         
                       
                     
                     
                       
                         s 
                         
                           1 
                           , 
                           1 
                         
                       
                     
                     
                       … 
                     
                     
                       
                         s 
                         
                           1 
                           , 
                           
                             
                               N 
                               F 
                             
                             - 
                             1 
                           
                         
                       
                     
                   
                   
                     
                       ⋮ 
                     
                     
                       ⋮ 
                     
                     
                       … 
                     
                     
                       ⋮ 
                     
                   
                   
                     
                       
                         s 
                         
                           
                             
                               N 
                               T 
                             
                             - 
                             1 
                           
                           , 
                           0 
                         
                       
                     
                     
                       
                         s 
                         
                           
                             
                               N 
                               T 
                             
                             - 
                             1 
                           
                           , 
                           1 
                         
                       
                     
                     
                       … 
                     
                     
                       
                         s 
                         
                           
                             
                               N 
                               T 
                             
                             - 
                             1 
                           
                           , 
                           
                             
                               N 
                               F 
                             
                             - 
                             1 
                           
                         
                       
                     
                   
                 
                 ] 
               
               . 
             
           
         
       
     
     Given that a signal subjected to the BU modulation is represented as s UB   (i) (t), the block unit adjusted to a specified time-frequency location (t i , f i ) may be represented as s UB   (i) (t−t i )e j2πf     i     (t−t     i     ) . 
     The generated signal including all the repeated block units is represented as: 
     
       
         
           
             
               
                 s 
                 
                   Block 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Repeat 
                 
               
               ⁡ 
               
                 ( 
                 t 
                 ) 
               
             
             = 
             
               
                 ∑ 
                 
                   i 
                   = 
                   0 
                 
                 
                   RF 
                   - 
                   1 
                 
               
               ⁢ 
               
                 
                   
                     s 
                     UB 
                     
                       ( 
                       i 
                       ) 
                     
                   
                   ⁡ 
                   
                     ( 
                     
                       t 
                       - 
                       
                         t 
                         i 
                       
                     
                     ) 
                   
                 
                 ⁢ 
                 
                   
                     ⅇ 
                     
                       j 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       π 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         
                           f 
                           i 
                         
                         ⁡ 
                         
                           ( 
                           
                             t 
                             - 
                             
                               t 
                               i 
                             
                           
                           ) 
                         
                       
                     
                   
                   . 
                 
               
             
           
         
       
     
     In the Process  902 , dedicated pilot symbols may also be added. Furthermore, the pilot symbols in the basic block unit may be processed via the same weighting factor sequence as that for the data part, so that the pilot symbols may carry information related to the weighting factor sequence (including the weighting factor sequence, and the information from which the weighting factor sequence may be obtained). 
     Process  903 : A signal at the specified time-frequency location is transmitted. 
     The orders of the BU modulation and the block repeat modulation in the process shown in  FIG. 8B  are different from those in process shown in  FIG. 9B , but it can be seen apparently that the same BR-OFDM signal may be generated with respect to the same data to be sent. 
     The base station may include multiple groups of modulation units, where each group of modulation units includes the above first, second and third modulation units for processing the data of one user, and the groups of modulation units operate concurrently. The base station further includes a combining unit, which is adapted to superpose the signals in the repeated block units at the same time-frequency location and send the superposed signal. The structure of the base station is shown in  FIG. 10 . The process of each group of modulation units is the same as described above, and will not be described hereinafter. 
     In the block repeat modulation in the above process, the pilot symbols and modulated data block that are contained in each repeated block unit are weighted together via a block repeat weighting factor, so that the dedicated pilot symbols carry the information of the weighting factor. However, it is also possible that only the data symbols are weighted and the pilot symbols are not weighted, the sending end may send the weighting factor sequence or codes therein to the receiving end before sending the data, or the receiving end may obtain the weighting factor sequence via system configuration. Additionally, it is also possible that no dedicated pilot is added during the block repeat modulation, and the receiving end may perform demodulation using a common pilot and the conjugate of the weighting factor sequence. The common pilot herein refers to one that is inserted at the location of the pilot time-frequency grid point, and is known by all users associated with the block unit. 
     At the receiving end, three-stage demodulation needs to be performed on the received signal to obtain the received data. In an embodiment, the three stages of demodulation include: BU demodulation at the first stage, block repeat demodulation at the second stage, and data demodulation at the third stage.  FIG. 11A  shows an apparatus that can implement such three stages of demodulation, and the apparatus includes: a communication unit  110 , a first demodulation unit  111 , a second demodulation unit  112  and a third demodulation unit  113 . The communication unit  110  is adapted to send and receive a signal; the first demodulation unit  111  is adapted to accomplish BU demodulation at a specified time-frequency location to generate a data block; the second demodulation unit  112  is adapted to perform the block repeat demodulation to obtain a data block to be demodulated; and the third demodulation unit  113  is adapted to accomplish the demodulation of the data block to be demodulated to generate the received data. The apparatus may be a mobile terminal or a base station.  FIG. 11B  shows an example of a process flow for receiving and demodulating a signal by the apparatus, and the process flow includes the following. 
     Process  1100 : A signal is received. 
     Process  1101 : The BU demodulation (i.e. the first stage of demodulation) is performed, that is, each repeated block unit is detected and inversely mapped at a specified time-frequency location, to obtain a data block. 
     In the Process  1101 , channel estimation may be performed by a channel estimator using pilot symbols, thus obtaining a channel response (i.e. a channel estimation result) of the received signal, where the channel response is valid in a time-frequency resource block to which the pilot symbols belong with respect to a user or a single signal. In the embodiment of the present invention, the algorithm employed and the pilot symbols relied on in the channel estimation are not limited. Then, channel equalization may be carried out on the data symbols in the BU by using the obtained channel response, thus obtaining equalized data symbols, where a simple particular example of the equalization algorithm is to carry out a deconvolution operation on the data symbols received originally. Next, the equalized data symbols are detected. Subsequently, based on a correspondence relationship between the detected data symbols and a data block, a data block corresponding to the repeated block unit is obtained from the detected data symbols. The output of the Process  1101  (which usually is soft data) is represented as:
 
{circumflex over (d)} Block Repeat   (i) =└{circumflex over (d)} BR     0     (i) , {circumflex over (d)} BR     1     (i) , . . . , {circumflex over (d)} BR     L-1     (i) ┘.
 
     If dedicated pilot symbols are employed in the corresponding sending data, and the pilot and data symbols are weighted using the same repeat code, a detection result of the data symbols may be obtained directly using the channel response obtained from the pilot. If only the data symbols are weighted using the repeat code at the sending end, while the pilot symbols are not weighted using the repeat code, the weighting factor in the detection result should be further chipped off (for example, by being divided by the weighting factor, or multiplied by the conjugate of the weighting factor), to restore the data. 
     Process  1102 : The block repeat demodulation (i.e. the second stage of demodulation) is performed, that is, the data blocks obtained from all the repeated block units are combined, obtaining a data block to be demodulated. 
     In the Process  1102 , a selective combining method, a maximum ratio combining method, an equal gain combining method, etc., may be employed for combining all the data blocks. In the maximum ratio combining method, each repeated data block is multiplied by a factor σ i  so that the signal is directly proportional to the signal-to-noise ratio, then all the repeated data blocks are sum up to obtain the data block to be demodulated, as shown in the equation below: 
     
       
         
           
             
               d 
               ^ 
             
             = 
             
               
                 ∑ 
                 
                   i 
                   = 
                   0 
                 
                 
                   RF 
                   - 
                   1 
                 
               
               ⁢ 
               
                 
                   σ 
                   i 
                 
                 · 
                 
                   
                     
                       d 
                       ^ 
                     
                     
                       Block 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       Repeat 
                     
                     
                       ( 
                       i 
                       ) 
                     
                   
                   . 
                 
               
             
           
         
       
     
     Process  1103 : The data demodulation (i.e. the third stage of demodulation) is performed, that is, the obtained data block to be demodulated is demodulated to generate the received data. 
     In the Process  1103 , a common demodulation of digital modulation is performed according to the modulation mode of the sending end, for example, BPSK, QPSK, 16 QAM, 64 QAM, etc. The output of the data symbols may be either a hard decision output, or a soft output for subsequent soft decision decoding. 
     In another implementation of the three-stage modulation, the three stages of demodulation include: block repeat demodulation at the first stage, BU demodulation at the second stage, and data demodulation at the third stage.  FIG. 12A  shows an apparatus that can implement such three-stage modulation, and the apparatus includes: a communication unit  120 , an adjusting unit  121 , a first demodulation unit  122 , a second demodulation unit  123  and a third demodulation unit  124 . The communication unit  120  is adapted to send and receive a signal; the adjusting unit  121  is adapted to adjust repeated block units at a plurality of specified time-frequency locations to time-frequency units at the same location; the first demodulation unit  122  is adapted to weight each of the plurality of repeated block units using the channel estimation and the conjugate of the weighting factor sequence corresponding to the repeated block unit, and then combine the weighted block units; the second demodulation unit  123  is adapted to demodulate the combined block units to obtain a data block; and the third demodulation unit  124  is adapted to generate the received data from the data block. The apparatus may be a mobile terminal or a base station.  FIG. 12B  shows an example of a process flow for receiving and demodulating the signal by the apparatus, and the process flow includes the following. 
     Process  1200 : A signal is received. 
     Process  1201 : Repeated block units at a plurality of specified time-frequency locations (the locations are determined by the block repeat factor determined between the sending end and the receiving end) are adjusted to time-frequency units at the same location. 
     Specifically, this Process is actually a mathematical operation, rather than a physical shift of a signal. From the perspective of the frequency domain, actually, the data symbols in different repeated block units are adjusted relative to their frequency domain reference location; and from the perspective of the time domain, actually, the data symbols in different repeated block units are subjected to subsequent processing simultaneously. 
     Process  1202 : The block repeat demodulation (i.e. the first stage of demodulation) is performed, that is, channel estimation is carried out using the pilot symbols in the repeated block units to obtain a channel response of the received signal, each of the plurality of repeated block units is weighted using the channel estimation and the conjugate of the weighting factor sequence corresponding to the repeated block unit, and the weighted block units are combined. 
     Process  1203 : The block unit demodulation (i.e. the second stage of demodulation) is performed, that is, the combined block units are detected and inversely mapped, to obtain a data block. 
     Process  1204 : The data demodulation (i.e. the third stage of demodulation) is performed, that is, the data block is demodulated to generate the received data. 
     As described above, if the sending end does not add a dedicated pilot during the block repeat modulation, the receiving end may perform demodulation using the common pilot and the conjugate of the weighting factor sequence. The process of the demodulation is the same as that described above, and further description thereof is omitted here. 
     According to the above description, various communication apparatuses with the above sending end function and receiving end function may be obtained according to embodiments of the present invention, that is, the communication apparatus may have the structure of any apparatus shown in  FIG. 8A  and  FIG. 9A  and in  FIG. 10A  and  FIG. 11A , and have the same processes of sending a signal and receiving a signal as those of the above sending end and receiving end respectively. For example, as shown in  FIG. 13A , the communication apparatus includes a first, a second and a third modulation units, a first, a second and a third demodulation units, and a communication unit. For example, as shown in  FIG. 13B , the communication apparatus is a base station, which includes two groups of modulation units, a group of demodulation units, and a communication unit. 
     In a system including a plurality of the above communication apparatuses, the communication apparatus for sending a signal may modulate and send a signal in any one of the above two signal sending modes, and the communication apparatus for receiving a signal may demodulate a received signal in any one of the above two signal receiving modes. 
     Referring to  FIG. 14 , a block repeat transmission communication system includes a base station  140  and a plurality of mobile terminals  141 ,  142 . An example of the process flow in which the base station  140  sends a signal to the mobile terminal  141  is shown in  FIG. 15A , and the process flow includes the following. 
     Process  1500 : The base station  140  modulates and partitions the data to be sent to the terminal  141 , to generate data blocks. 
     Process  1501 : The base station  140  modulates and maps the each data block to a PRB to generate a basic block unit. 
     Process  1502 : The base station  140  performs weighting and repeating modulation on each generated basic block unit by using a weighting factor sequence, to generate a plurality of repeated block units corresponding to the basic block unit, and maps each repeated block unit to a specified time-frequency location. 
     Process  1503 : The base station  140  sends a signal at the specified time-frequency location after modulating the channel. 
     Process  1504 : The terminal  141  receives the signal sent by the base station  140 . 
     Process  1505 : The mobile terminal  141  detects and inversely maps each repeated block unit at a specified time-frequency location, to obtain a data block. 
     Process  1506 : The mobile terminal  141  combines the data blocks obtained from all the repeated block units, to obtain a data block to be demodulated. 
     Process  1507 : The mobile terminal  141  demodulates the obtained data block to be demodulated, to generate the received data. 
     Referring to  FIG. 15B , which shows an example of the process flow in which the base station  140  sends a signal to the mobile terminals  141 ,  142  simultaneously, and the process flow includes the following. 
     Process  1530 : The base station  140  modulates and partitions the data to be sent respectively to the terminals  141 ,  142 , to generate data blocks. 
     Process  1531 : The base station  140  modulates and maps each of the data blocks to a PRB, to generate a basic block unit. 
     Process  1532 : The base station  140  performs weighting and repeating modulation on the respective basic block units using weighting factor sequences corresponding to mobile terminals  141  and  142 , respectively, to obtain a plurality of repeated data blocks corresponding to each basic block unit, and maps each repeated block unit to a specified time-frequency location. Here, the weighting factor sequences of mobile terminals  141 ,  142  are different. 
     Process  1533 : The base station superposes the signals of mobile terminals  141 ,  142  at the same time-frequency location. 
     Process  1534 : The base station  140  sends a signal at the specified time-frequency location after modulating the channel. 
     Process  1535 : The terminals  141 ,  142  respectively receives the signal sent by the base station  140 . 
     Process  1536 : The mobile terminals  141 ,  142  respectively adjust repeated block units at a plurality of specified time-frequency locations to time-frequency units at the same location. 
     Process  1537 : The mobile terminals  141 ,  142  respectively perform block repeat demodulation using the plurality of repeated block units. That is, each of the mobile terminals  141 ,  142  performs channel estimation using the pilot symbols in the repeated block units to obtain a channel response of the received signal, weights each of the plurality of repeated block units using the channel estimation and the conjugate of the weighting factor sequence corresponding to the repeated block unit, and combines the weighted block units (since the weighting factor sequences corresponding to terminals  141 ,  142  are different, the signals can be separated by the weighting and combining). 
     Process  1538 : The mobile terminals  141 ,  142  respectively detect and inversely map the combined block units to obtain a data block. 
     Process  1539 : The mobile terminals  141 ,  142  respectively demodulate the data block to generate the received data. 
     Referring to  FIG. 15C , which shows an example of the process flow in which the mobile terminal  141  sends a signal to the base station  140 , and the process flow includes the following. 
     Process  1560 : The mobile terminal  141  partitions and modulates the data to be sent to the base station  140 , to generate data blocks. 
     Process  1561 : The mobile terminal  141  performs weighting and repeating modulation on each of the generated data blocks using a weighting factor sequence, to obtain a plurality of repeated data blocks corresponding to the generated data block. 
     Process  1562 : The mobile terminal  141  modulates and maps the repeated data blocks to repeated block units, and maps the repeated block units to the specified time-frequency locations. 
     Process  1563 : The mobile terminal  141  sends a signal at the specified time-frequency location after modulating the channel. 
     Process  1564 : The base station  140  receives the signal sent by the mobile terminal  141 . 
     Process  1565 : The base station  140  detects and inversely maps each repeated block unit at a specified time-frequency location, to obtain a data block. 
     Process  1566 : The base station  140  combines the data blocks obtained from all the repeated block units, to obtain a data block to be demodulated. 
     Process  1567 : The base station  140  demodulates the obtained data block to be demodulated, to generate the received data. 
     Referring to  FIG. 15D , which shows another example of the process flow in which the base station  140  sends a signal to the mobile terminal  142 , and the process flow includes the following. 
     Process  1580 : The base station  140  partitions and modulates the data to be sent to the mobile terminal  142 , to generate data blocks. 
     Process  1581 : The base station  140  performs weighting and repeating modulation on each of the generated data blocks using a weighting factor sequence, to obtain a plurality of repeated data blocks corresponding to the generated data block. 
     Process  1582 : The base station  140  modulates and maps the repeated data block to a repeated block unit, and maps the repeated block unit to a specified time-frequency location. 
     Process  1583 : The base station  140  sends a signal at the specified time-frequency location after modulating the channel. 
     Process  1584 : The base station  140  receives the signal sent by the mobile terminal  141 . 
     Process  1585 : The mobile terminal  142  adjusts repeated block units at a plurality of specified time-frequency locations to time-frequency units at the same location. 
     Process  1586 : The mobile terminal  142  performs block repeat demodulation using the plurality of repeated block units. That is, the mobile terminal  142  performs channel estimation using the pilot symbols in the repeated block units to obtain a channel response of the received signal, weights each of the repeated block units using the channel estimation and the conjugate of the weighting factor sequence corresponding to the repeated block unit, and combines the weighted block units. 
     Process  1587 : The mobile terminal  142  detects and inversely maps the combined block units to obtain a data block. 
     Process  1588 : The mobile terminal  142  demodulates the data block to generate the received data. 
     In the multi-access application of block repeat modulation, for the repeated block units of different users/different channels employing the same time-frequency resource block, their pilot symbols are multiplexed in a certain multiplexing mode and demultiplexed. For example, the pilot symbols are transferred in a Time Division mode, a Frequency Division mode or a Code Division mode. An orthogonal multiplexing mode in which the time and frequency are non-overlapping is shown in  FIG. 16 . 
     In summary, in the embodiments of the present invention, a block repeat modulation signal is generated from the data to be sent via three-stage modulation, i.e., the data modulation, the BU modulation and the block repeat modulation (in the case of the block repeat transmission combined with OFDM, the repeated block units correspond to an OFDM time-frequency resource block); correspondingly, the receiving end performs three-stage demodulation on the received signal to generate the received data. By applying the method and the apparatus of the present invention to a broadband wireless communication system, an effective, reliable and variable-speed transmission of information in a wireless communication channel may be implemented, and the multiplexing and multiple access of wireless communication channel resources may also be implemented. By applying the method and the apparatus of the present invention to a wireless mobile cellular system, the co-frequency networking may be implemented conveniently, and system capacity and performance may be improved. The method of the present invention may well solve the problems of resource allocating and scheduling and interference (including intra-cell and inter-cell interferences) controlling in wireless communication, thereby the system capacity and performance may be improved greatly, and an effective solution may be provided for the broadband wireless communication system. 
     The above illustration is generally provided by taking the combination of block repeat transmission and OFDM as an example. However, since such a multi-access mode is implemented based on the repeat of a basic PRB, and the modulation and multi-access mode of the lower layer is not limited, such a block repeat multi-access solution may also be combined with other multi-access modes to form various composite solutions. For example, the combination of the block repeat transmission with SC-FDMA forms a BR-SC-FDMA mode, the block repeat modulation and block repeat demodulation of which are similar with those described above. 
     The technical solution in the embodiment of the present invention is not limited to be combined with other key technologies employed in the existing wireless communication system. For example, the uplink power control technology and downlink power control technology may be employed in the above solutions. By introducing the uplink power control technology based on the signal strength balancing criterion or the signal-to-interference ratio balancing criterion, it is helpful to lower the interferences in the system and improve the system capacity. Similarly, the corresponding power control technology may also be combined in the downlink direction. Since the channel fading of the signals in the respective time-frequency resource blocks is different and may be irrelevant, the power control may be performed based on each block unit. 
     Other technologies that may be combined with the technical solutions in the embodiments of the present invention include Multiple-Input Multiple-Output (MIMO) Antenna technology, Soft Switching technology, Adaptive Modulation and Coding (AMC) technology, Hybrid Automatic Repeat reQuest (HARQ) technology, etc. 
     It will be appreciated that one skilled in the art may make various modifications and alterations to the present invention without departing from the spirit and scope of the present invention. Accordingly, if these modifications and alterations to the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention intends to include all these modifications and alterations.