Abstract:
The present invention provides a new method and apparatus, in a network device of a multi-carrier based wireless access network, for transmitting uplink data to access device side, and the corresponding method and apparatus for channel estimation in its uplink counterpart device, wherein, a plurality of network device comprise one or more multi-antenna network devices, at least one of the multi-antenna network device transmits multipath subcarrier modulated symbols via a plurality of transmitting antennas configured for itself, wherein, at least two transmitting antennas use different subcarrier sets, but share one pilot pattern, wherein, pilot pattern used by each network device is different from the pilot pattern used by any other network device. The present invention not only can fully utilize the frequency diversity introduced by the plurality of transmitting antennas, but also can guarantee a relative high antenna power gain and save as much time-frequency resource cost caused by pilot signal as possible.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a multi-carrier based wireless access network, in particular relates to the uplink data transmission and the processing of the uplink communication in a multi-carrier based wireless access network. 
       BACKGROUND OF THE INVENTION 
       [0002]    Multi-User Multiple-Input Multiple-Output (MU-MIMO) 
         [0003]    The uplink of the MU-MIMO is typically referred to as Multiple Access Channel (MAC), and the downlink is referred to as Broadcast Channel (BC). In the uplink, all mobile terminals work at the same frequency band and transmit signals to the base station simultaneously, and then the base station distinguishes user data in a proper manner. The base station needs to separate data of each user by using array processing, multi-user detection or other effective manner aiming at different access manners. In the downlink, the base station performs serial-parallel conversion to the processed data so as to generate a plurality of data streams, each of which is pulse-shaped and modulated, and then transmitted to the wireless space via a plurality of antennas. Each receiving antenna receives an aggregation of the signals transmitted to all the communication users by the base station and interference and noise, wherein, the Multi-Address Interference (MAI) introduced thereby should be eliminated. In this disclosure, there is no intention to distinguish the concepts of “user” and “mobile terminal”. 
         [0004]    Due to the independency of each user channel in the MU-MIMO system, the user can get to know about its own channel state information, but can hardly obtain the channel state information of the other users, and the obtaining of the channel state information of the other users requires great cost. That is to say, it is hard to conduct cooperation between users. On the contrary, the base station is qualified to obtain the channel state information of all the communication users. For the Time Division Duplex (TDD) system, it could be obtained by the training or pilot sequence of the uplink received by the base station. For the Frequency Division Duplex (FDD) system, it could be obtained through the feedback. Besides, the processing ability of the base station is stronger than that of the Mobile Terminal (MS), thus the preprocessing of the signal (e.g. beamforming) is done before the base station transmits the signal, so as to eliminate and inhibit the interference, or the base station performs postprocessing to distinguish the users after the signals are received. 
         [0005]    Since the Multi-User MIMO system uses the same frequency band, other multiple access methods except Frequency Division Multiple Access (FDMA) may be applied. Wherein, the spectrum effectiveness of the Time Division Multiple Access (TDMA) is relatively low, while numerous code resources are required for Code Division Multiple Access (CDMA). However, Space Division Multiple Access (SDMA) doesn&#39;t have these two disadvantages. In the mean time, multi-antennas of the Multi-User MIMO can also satisfy the requirement for the space dimension in the Space Division Multiple Access, therefore, Space Division Multiple Access (SDMA) becomes an important multiple access method in the Multi-User MIMO system. 
         [0006]    Multi-User MIMO has many advantages, e.g. enlarging the system throughput by using multiplexing gain of the multi-antennas, enhancing the system performance by using diversity gain of the multi-antennas, distinguishing the users by using the directivity gain of the antenna, so as to eliminate the interference between users, etc. Of course, if combined with the realization problem of the practical application, the complexity of the algorithm should also be considered, thus a compromise between the performance and the complexity needs to be found. It could be said so, that the complexity is the price for the numerous advantages introduced by the Multi-User MIMO technology. 
         [0007]    Virtual MIMO Based On Collaborative Diversity Implemented by Multiple Single Antenna Mobile Terminals (VMIMO) 
         [0008]    The spacing between adjacent antennas required by the ideal MIMO multi-antenna system is far greater than the wavelength of the electric wave, and the transmission channel between a plurality of transceive antennas are un-correlated. However, it has always been difficult for the user terminal to implement the settlement of the multiple antennas, and it is unrealistic to satisfy the ideal requirements mentioned above, due to the limitation of the mass, volume and power consumption. Thus Sendonaris etc. proposed a new space diversity technique, Collaborative diversity, the basic principle of which is: a user terminal transmits the information received from its partner (another mobile terminal) besides its own information to the base station. In the mean time, part of the information of its partner is received by the mobile terminal and forward to the base station. Thus, two independent fading paths are generated between the two mobile terminals and the base station respectively, and therefore the spatial diversity gain is obtained in the way of imitating the traditional multi-transmitting antenna diversity. The base station may confront the multi-user interference effectively by joint detection technique of interference cancellation, maximum likelihood criterion (ML) etc. for the uplink signals transmitted over different paths. 
         [0009]    Virtual MIMO Based On Collaborative Spatial Multiplexing Implemented By Multiple Single Antenna Mobile Terminals 
         [0010]    It is proposed in the protocol version 1.0 of the mobile WIMAX system configuration based on IEEE802.16e standard, that a virtual MIMO technique which is referred to as Collaborative Spatial Multiplexing is implemented, by matching two mobile terminals having single transmitting antenna. Wherein, the two mobile terminals communicate with the same base station in the same time-frequency resource, each mobile terminal only transmits its own traffic data, while each user terminal transmits its on pilot data using one of the two orthogonal pilot patterns, so that the base station can properly estimate the two uplink channels from the two mobile terminals, and then retrieve the uplink traffic data corresponding to the two mobile terminals using spatial multiplexing decoder such as minimum mean square error (MMSE) decoder or maximum likelihood decoder. 
         [0011]    For more details of the content of the protocol version 1.0 of Mobile WiMAX system configuration, please see WiMAX Forum™ Mobile System Profile Release 1.0 Approved Specification (Revision 1.4.0: 2007-05-02). 
         [0012]    Virtual MIMO Implemented by Using Least One Multi-Antenna Mobile Terminal 
         [0013]    In the protocol version 1.5 of the mobile WiMAX system configuration based on IEEE 802.16e standard and the developing IEEE 802.16m standard specification, it is possible to configure a plurality of transmitting antennas for one mobile terminal, even though the spacing between the antennas can not achieve the various requirements of the ideal status temporally. 
         [0014]    Virtual MIMO implemented by using at least one multi-antenna mobile terminal has the following three forms, each mobile terminal has two transmitting antennas without loss of generality, and the virtual MIMO is implemented by matching two mobile terminals. 
         [0015]    (a) Each mobile terminal works under Single-Input Multiple-Output (SIMO) mode, or each mobile terminal transmits the same data via the two transmitting antennas thereof, or one mobile terminal works under SIMO mode, while the other mobile terminal transmits the same data via its two transmitting antennas. 
         [0016]    Advantages: Only two orthogonal pilot patterns are needed. 
         [0017]    Disadvantages: The spatial diversity gain of the multi-antennas is not fully utilized, and when one of the mobile terminals uses only one transmitting antenna, the power gain of the silent antenna will be wasted, the transmitting power averaged to each subcarrier is not high. 
         [0018]    (b) One mobile terminal works under SIMO mode or transmits the same data via its two transmitting antennas, and the other mobile terminal works under MIMO mode, such as Space Time Transmit Diversity (STTD) or Spatial Multiplexing (SM). 
         [0019]    Advantages: The mobile terminal working under MIMO mode fully utilizes the spatial diversity gain and power gain of its multi-antenna. And, if space-time coding scheme like STTD etc. is used, the robustness of the system could be improved; while if it is implemented that, two independent data streams are transmitted using SM via the two antennas of one mobile terminal, the data throughput of the system could be increased. 
         [0020]    Disadvantages: The mobile terminal working under SIMO mode or transmitting the same data via its two transmitting antennas doesn&#39;t fully utilize the spatial diversity gain and/or power gain of its multi-antenna. Since the two transmitting antennas of the mobile terminal using STTD or SM require to use pilot patterns orthogonal to each other, the two user terminals requires three orthogonal pilot patterns. Thus the pilot signals occupy more resources i.e. subcarrier+time slot. Channel estimation and the corresponding traffic data decode are to be carried out based on the pilot signals in the three orthogonal pilot patterns, thus the receiver is more complicated than that of the protocol version 1.0 of the mobile WiMAX system configuration. 
         [0021]    (c) Both mobile terminals work under MIMO mode, such as STTD or SM. 
         [0022]    Advantages: Two user terminals can both fully utilize the transmitting antennas thereof, high power gain and diversity gain could be achieved. 
         [0023]    Disadvantages: Four pilot patterns orthogonal to each other being used, the pilot signals occupy more resources. Channel estimation and the corresponding traffic data decode are to be carried out based on the pilot signals in the four orthogonal pilot patterns, thus the receiver is much more complicated than that of the protocol version 1.0 of the mobile WiMAX system configuration. 
         [0024]    By now, WiMAX and IEEE 802.16m standardization organization are discussing about the above (b) and (c). There are four detailed implementation manners for the situation in (a): 
         [0025]    1. Basic VMIMO 
         [0026]    Each mobile terminal uses one transmitting antenna to transmit uplink signal. It belongs to open-loop scheme and the base station doesn&#39;t need to transmit any indicating information related to the configuration of the transmitting antenna to the mobile terminal. 
         [0027]    2. VMIMO Assisted by Spatially Uncoded Transmit Diversity (SUTD) 
         [0028]    The two transmitting antennas of each mobile terminal transmit the same uplink signal. It belongs open-loop scheme, and the base station doesn&#39;t need to transmit any indicating information related to the configuration of the transmitting antenna to the mobile terminal. 
         [0029]    3. VMIMO Assisted by Switched Transmit Diversity (TSTD) 
         [0030]    Each mobile terminal uses its two configured transmitting antenna alternatively in time dimension, for example, one mobile terminal uses the first transmitting antenna to transmit the frame of odd number, and uses the second transmitting antenna to transmit the frame of even number, while another mobile terminal uses the first transmitting antenna to transmit the frame of even number, and uses the second transmitting antenna to transmit the frame of odd number, as shown in  FIG. 1 . Since the frames are continuous transmit elements in time domain, one mobile terminal uses only one transmitting antenna in each frame size, thus this scheme is also open-looped. 
         [0031]    4. Similar to manner 3, the mobile terminal&#39;s selection of antenna is not simple periodical alternation, but selecting the one with better signal quality. Thus it is closed-loop scheme. The detailed selection of antenna is based on the information from the base station for indicating the quality of the uplink signal or based on the Channel Reciprocity under time division duplex mode. 
         [0032]    The former three implementation manners for the situation (a) could not implement the diversity gain of the multi-antennas. This defect will be further described below in connection with simulation diagram. Furthermore, besides the implementation manner 2, the mobile terminal in other manner keeps one of its transmitting antennas silent, so that the power gain is impaired. 
       SUMMARY OF THE INVENTION 
       [0033]    In the light of the problems existing in the prior art mentioned above, the present invention is intended to provide a new method and apparatus for uplink signal transmission in the multi-carrier based multi-antenna network device having a plurality of transmitting antennas, such as mobile terminal, and a corresponding method and apparatus for channel estimation in the uplink counterpart device of the network device such as base station. The above scheme can fully utilize the frequency diversity introduced by the plurality of transmitting antennas. 
         [0034]    This invention is also intended to provide the above mentioned method and apparatus which can guarantee a relatively high antenna power gain. 
         [0035]    This invention is also intended to provide the above mentioned method and apparatus, which can save as much time-frequency resource cost caused by the pilot signal as possible. 
         [0036]    For the above intention, according to a first aspect of the invention, a method, in a network device of a multi-carrier based wireless access network, for transmitting uplink data to access device side, is provided, wherein the network device has a plurality of transmitting antennas, and the method comprises the following steps: transmitting multipath subcarrier modulated symbols via the plurality of transmitting antennas, Wherein, subcarrier sets used by at least two transmitting antennas are different. 
         [0037]    Preferably, at least two transmitting antennas share the same pilot pattern. 
         [0038]    According to a second aspect of the invention, a method, in an uplink counterpart device of a network device of a wireless access network, for performing channel estimation, is provided, wherein, the method comprises the following steps: parsing a pilot signal from an uplink signal received from the network device, based on a pilot pattern preassigned to the plurality of transmitting antennas of the network device; performing the channel estimation for the uplink channel between the network device and the uplink counterpart device according to the parsed pilot signal, the obtained channel estimation results being used for parsing the subsequent signals, 
         [0039]    According to a third aspect of the invention, a first transmitting device, in a network device of a multi-carrier based wireless access network, for transmitting uplink data to access device side, is provided, wherein, the network device has a plurality of transmitting antennas, and the first transmitting device comprises: a second transmitting means, configured to transmit multipath subcarrier modulated symbols via the plurality of transmitting antennas, wherein, subcarrier sets used by at least two transmitting antennas are different. 
         [0040]    Preferably, at least two transmitting antennas share the same pilot pattern. 
         [0041]    According to a fourth aspect of the invention, a channel estimation device, in an uplink counterpart device of a network device of a wireless access network, is provided, wherein, the device comprises: a pilot parsing means, configured to parse a pilot signal from an uplink signal received from the network device, based on a pilot pattern preassigned to the plurality of transmitting antennas of the network device; a processing means, configured to perform the channel estimation for the uplink channel between the network device and the uplink counterpart device according to the parsed pilot signal, the obtained channel estimation results being used for parsing the subsequent signals. 
         [0042]    According to a fifth aspect of the invention, a method of performing uplink communication between a plurality of network devices and their common uplink counterpart device in a multi-carrier based wireless access network is provided, wherein the plurality of network devices comprises one or more multi-antenna network devices, wherein at least one multi-antenna network device transmits multipath subcarrier modulated symbols via a plurality of transmitting antennas configured for itself, wherein subcarrier sets used by at least two transmitting antennas are different. 
         [0043]    Preferably, at least two transmitting antennas share the same pilot pattern. 
         [0044]    Preferably, different pilot patterns are used by the plurality of network devices, wherein, the different pilot patterns may be pilot patterns orthogonal to each other. 
         [0045]    With the method and apparatus provided in this invention, the frequency diversity introduced by multi-antennas can be effectively utilized, and a relatively high antenna power gain can be guaranteed, furthermore, preferably, the invention can save the time-frequency resource cost caused by the pilot signal as much as possible, namely can use as few orthogonal pilot patterns as possible. 
     
    
     
       BRIEF DESCRIPTION OF TUE DRAWINGS 
         [0046]    By reading the detailed description of the non-constricting embodiments with reference to the following drawings, the other features, objects and advantages of this invention will become apparent. 
           [0047]      FIG. 1  shows a schematic view of the VMIMO assisted by Time Switched Transmit Diversity (TSTD) in the prior art; 
           [0048]      FIG. 2  shows a sketch of the physical layer of an OFDM transmitter according to one embodiment of the invention; 
           [0049]      FIG. 3   a  shows a schematic view of two mobile terminals according to one embodiment of the invention; 
           [0050]      FIG. 4  shows a flow chart of the method according to one preferable embodiment of the invention: 
           [0051]      FIG. 5  shows a block diagram of a first transmitting device in a network device of a multi-carrier based wireless access network, for transmitting uplink data to access device side, according to one embodiment of the invention; 
           [0052]      FIG. 6  shows a block diagram of a channel estimation device in an uplink counterpart device of a network device of a wireless access network, according to one embodiment of the invention; 
           [0053]      FIG. 7   a  and  FIG. 7   b  show a comparison between the simulation results of the present invention and the prior art. 
       
    
    
       [0054]    In the drawings, same or similar reference numerals refer to the same or similar components. 
       DETAILED DESCRIPTION OF EMBODIMENTS 
       [0055]      FIG. 2  shows a sketch of the physical layer of a transmitter according to one embodiment of the invention. Since only the uplink signal transmission is discussed in the present invention, the transmitter is mainly located in the various network devices needing to transmit uplink signal in a wireless manner in the access network, such as mobile terminal, relay station, etc. Of course, with the development of the wireless transmission technology, if the base station needs to transmit uplink wireless signal in the near further, the transmitter shown in the figure may also be used in the base station. In the following, without loss of generality, the present invention will be described using the uplink communication between the mobile terminal and the base station as example. 
         [0056]    It should be understood by those skilled in the art, some modules that should be included in the Orthogonal Frequency Division Multiplexing (OFDM) transmitter, such as module for inserting Cyclic Prefix (CP), are omitted in  FIG. 2  for the sake of conciseness. And it should also be understood by those skilled in the art, such omission will not influence the realization of the present invention, because these modules have no substantial connection with the technical solution of the invention described in the following. And, although OFDM is used as an example in the following, the scope of the invention is defined by the appended claims, and the technical solution thereof may be applied in various multi-carrier based wireless communication systems. 
         [0057]    One of the core concepts of the invention is that, at least two transmitting antennas of the mobile terminal which has a plurality of transmitting antennas use different subcarrier sets but share the same pilot pattern. Therefore, the functions implemented by module U comprises mapping the pilot symbol and the QAM modulated data symbol to a plurality of subcarriers, while the corresponding relationship between these subcarriers and the transmitting antennas could he determined before the subcarrier modulation, or instantly determined after the earner modulation. In the following, without loss of generality, the situation of the predetermination of the corresponding relationship between the subcarriers and the transmitting antennas is taken as an example. 
         [0058]    Referring to  FIG. 3   a  in connection with  FIG. 3   b ,  FIG. 3   a  shows two mobile terminals  21  and  22 . The mobile terminal  21  has two transmitting antennas TX_ 21   a  and TX_ 21   b , and uses a first pilot pattern. The mobile terminal  22  has two transmitting antennas TX_ 22   a  and TX_ 22   b , and uses a second pilot pattern. Taking the mobile terminal  21  side for example, the adjacent six Resource Units are corresponding to TX_ 21   a  and TX_ 21   b  respectively. The detailed corresponding relationship is that, RU 1 , RU 3  and RU 5  are corresponding to TX_ 21   a , and RU 2 , RU 4  and RU 6  are corresponding to TX_ 21   b . It can he seen in  FIG. 3   b , a Resource Unit is a resource block formed by a plurality of subcarriers and a plurality of OFDM symbols. For the uplink of OFDM system, a Resource Unit is typically the smallest unit of the channel estimation, thus  FIG. 3   a  shows a preferred embodiment. 
         [0059]    It should be understood by those skilled in the art, only 24 subcarriers are shown in  FIG. 3   a  for the sake of convenience. Although it is far less than the number of the subcarriers in the practical OFDM system, such as 1024, this has no influence on an integral and clear description of the substance of the present invention. Based on the statement above, the structure formed by 3 OFDM symbols and 24 subcarriers could be seen as one OFDM frame, wherein each row may be seen as one OFDM symbol. 
         [0060]    It should also be understood by those skilled in the art,  FIG. 3   a  only shows one specific embodiment of the present invention. In fact, the corresponding relationship between each resource unit and the transmitting antenna may vary flexibly, for example, RU 1 -RU 3  may be transmitted over TX_ 21   a , and RU 4 -RU 6  may be transmitted over TX_ 21   b ; or RU 1 , RU 2 , RU 5 , RU 6  are transmitted over TX_ 21   a , and RU 3 , RU 4  are transmitted over TX_ 21   b . In a word, one transmitting antenna of one mobile terminal transmits signals by using a part of the subcarriers available at the mobile terminal. 
         [0061]      FIG. 4  shows a flow chart of the method according to one preferable embodiment of the invention. As stated above, the sequence relationship between steps is merely a non-constricting embodiment of the present invention, especially step S 212  and S 213  which have no sequence therebetween. 
         [0062]    According to the preferable embodiment, in step S 211 , the mobile terminal obtains a corresponding relationship between a plurality of transmitting antennas and the subcarriers determined according to the channel quality information. Step S 211  may be implemented by some sub-steps. For example, in the Time Division Duplex (TDD) mode. the receiving channel quality and the transmitting channel quality are the same within the channel related time, because the receiving and transmitting are of the same frequency hut of different time. Therefore, the mobile terminal  21  may obtain the quality related information of the uplink signal received by the base station and transmitted by the mobile terminal  21  using each RU, according to the downlink channel quality related information received at each RU. The corresponding relationship between its subcarriers and the plurality of transmitting antennas is therefore determined. For example, the base station may indicate the quality related information of the uplink signal previous received form each RU of the mobile terminal  21  to the mobile terminal  21 , and then the mobile terminal  21  determines the corresponding relationship between its subcarriers and the plurality of transmitting antennas according to the indication information received from the base station. For example, if the mobile terminal  21  uses the corresponding relationship of its subcarriers and the plurality of transmitting antennas shown in  FIG. 3   a , and the uplink signal quality related information from the base station indicates that, the quality of the signal transmitted over TX_ 21   a  is a few dB higher than that of the signal transmitted over TX_ 21   b , the mobile terminal  21  adjusts the distribution of the plurality of subcarriers on the two transmitting antennas. For example, the ratio of 1:1 (two antennas go halves in the total subcarrier) shown in  FIG. 3   a  is adjusted to 2:1 or even higher. Optionally, the mobile terminal may also prestore a plurality of information indicating the different corresponding relationships between the subcarriers and the transmitting antennas, and properly selects therefrom according to the uplink signal quality related information. 
         [0063]    According to a variant of the situation above, the base station instead of the mobile terminal  21  may determine the corresponding relationship between the subcarriers and the transmitting antennas TX_ 21   a  and TX_ 21   b  in the following time period, thus, the information transmitted to the mobile terminal  21  by the base station is the specific corresponding relationship between each subcarrier and the corresponding transmitting antenna; or the number of the available subcarriers on each antenna, while the mobile terminal  21  may determine on its own which antenna use which subcarrier. 
         [0064]    In this example, it can be seen that there are differences between the execution cycles of step S 211  and its subsequent step shown in  FIG. 4 . If there is more uplink data, the step S 212  and S 213  are actually performed constantly, while the step S 211  is performed preferably at a determined period. It should be understood by those skilled in the art, if the period is too long, the system may be unable to timely response to the sudden degradation of the channel etc., which leads to mass of data being transmitted over antenna with extremely had channel conditions, therefore the base station is unable to receive properly. Likely, if the period is too short, the requirement to the processing ability of the mobile terminal is too high, which may therefore result in the increment of the feedback as it is preferably carried out based on the uplink signal quality related information. 
         [0065]    It should he understood by those skilled in the art, the corresponding relationship between each subcarrier and the transmitting antennas may he statically configured, for example, subcarriers No.  0 - 5 , No.  12 - 17  may be statically corresponding to TX_ 21   a , while subcarriers No.  6 - 11 , No.  18 - 23  may be statically corresponding to TX_ 21   b . Thus, step S 211  may be omitted. Furthermore, the mobile terminal  21  may also prestore a plurality of information indicating the different corresponding relationships between the subcarriers and the transmitting antennas, and periodically switch the used corresponding relationship, in this case, step S 211  may also be omitted. 
         [0066]    In step S 212 , the QAM modulated data symbols, the pilot symbols generated by the pilot symbol generator are together modulated with the subcarrier, therefore the multi-path subcarrier modulated symbols are obtained. Wherein, since certain subcarrier is corresponding to certain specific transmitting antenna, date symbols or pilot symbols modulated by certain subcarrier are queued on the corresponding transmitting antenna. Thus, two paths of subcarrier modulated symbols are generated. 
         [0067]    In step S 213 , the two paths of subcarrier modulated symbols obtained in step S 212  are transmitted to the base station over the corresponding transmitting antenna. 
         [0068]    As shown in  FIG. 3   a , except for the idle subcarriers, each RU may carry 10 data symbols or pilot symbols, and in the above embodiment, the data symbols carried by the shown six RUs are different from each other. According to a variant of the embodiment, wherein, the data rate is half of that in the previous embodiment, namely, the data symbols carried by RU 1  and RU 2 , by RU 3  and RU 4 , by RU 5  and RU 6  are respectively the same, the remaining general data symbols are buffered temporarily for later transmission. Thus, same data symbols are transmitted over the two transmitting antennas of the mobile terminal  21 , with the subcarrier used being different. Extra frequency diversity may be introduced, of course, the price of which is the decrease of data rate. 
         [0069]    The procedure in the mobile terminal  22  shares the same principle with the mobile terminal  21  thus, no more details will be given here. However, preferably, the first pattern by the mobile terminal  21  is different n the second pilot pattern used by the mobile terminal  22 . More preferably, the first pilot pattern and the second pilot pattern are orthogonal to each other. 
         [0070]    In the present invention, preferably, each transmitting antenna transmits using full power. Thus, in comparison with the prior art shown in  FIG. 1 , the antenna transmitting power averaged to each subcarrier is higher, thus the advantage of transmitting power gain is obvious. 
         [0071]    According to a different embodiment of the invention, under the permission of the conditions such as the equipment size etc., the mobile terminal may have more than two transmitting antennas, for example, four or even eight. Then, the implementation manner of the present invention is more flexible, for example, if one OFDM symbol comprises 8 RUs, while the mobile terminal has 4 antennas, then the first and the fifth RUs may be transmitted over the first transmitting antenna, and the second and the sixth RUs may be transmitted over the second transmitting antenna, and the third and the seventh RUs may be transmitted over the third transmitting antenna, and the fourth and the eighth RUs may he transmitted over the fourth transmitting antenna, and the base station may have only one pilot pattern assigned to the mobile terminal. Alternatively, the first, third, fifth and seventh RUs may be transmitted over the first and second transmitting antennas, and the second, fourth, sixth and eighth RUs may be transmitted over the third and fourth transmitting antennas, and the base station may have one pilot pattern or a plurality of orthogonal pilot patterns assigned to the mobile terminal. For example, the first and the third transmitting antennas share one pilot pattern, and the second and the fourth transmitting antennas share another pilot pattern. Other equivalents or obvious variants of these two examples may also achieve the same technical effect, and won&#39;t be further described. 
         [0072]    In the embodiment where a plurality of pilot patterns are assigned to one mobile terminal by the base station, in order to implement channel estimation, the pilot patterns assigned to different mobile terminals by the base station are different. According to each pilot pattern known previously, the base station may parse out the pilot signals transmitted using different pilot patterns from the uplink signals transmitted by the plurality of mobile terminals, so as to perform channel estimation for each uplink channel, and parse the subsequent uplink signals more preciously. Basically, the introduction of the invention has no influence on the receiver of the uplink counterpart device such as base station. The uplink signal transmitted according to the present invention may be received and parsed using the existing receiver based on ML or MMSE. 
         [0073]    The invention is described above in the aspect of method. In the following it will he described in the aspect of apparatus.  FIG. 5  shows a block diagram of a first transmitting device in a network device of a multi-carrier based wireless access network, for transmitting uplink data to access device side, according to one embodiment of the invention.  FIG. 6  shows a block diagram of a channel estimation device in an uplink counterpart device of a network device of a wireless access network, according to one embodiment of the invention. 
         [0074]    The first transmitting device  211  comprises a second transmitting means  2111  and a first obtaining means  2112 . The first obtaining means  2112  comprises a second obtaining means  21121  and a determining means  21122 . The channel estimation device  111  comprises a pilot parsing means  1111  and a processing means  1112 . The following description is carried out referring to  FIG. 5  and  FIG. 6  in connection with  FIGS. 3   a  and  3   b . The first transmitting means  211  is typically located in the mobile terminal  21 ,  22  as shown in  FIG. 3   a , and the channel estimation device  111  is typically located in the uplink counterpart device such as a base station. Taking the uplink communication between the mobile terminal  21  and the base station to which it belongs as an example: 
         [0075]    According to a preferred embodiment, the first obtaining means  2112  at the mobile terminal  21  obtains the corresponding relationship between a plurality of transmitting antennas and the subcarriers determined according to the channel quality information, which may he cooperatively implemented by two sub-means thereof. Specifically for example, in the Time Division Duplex (TDD) mode, the receiving channel quality and the transmitting channel quality are the same within the channel related time, because the receiving and transmitting are of the same frequency but of different time. Therefore, the second obtaining means  21121  may obtain the quality related information of the uplink signal received by the base station and transmitted by the mobile terminal  21  using each RU, according to the downlink signal quality related information received at each RU. The determining means  21122  determines therefore the corresponding relationship between the subcarriers and the plurality of transmitting antennas. Specifically for example, the base station may indicate the quality related information of the uplink signal previous received from each RU of the mobile terminal  21  to the second obtaining means  21121 , and then the determining means  21122  determines the corresponding relationship between the subcarriers and the plurality of transmitting antennas according to the indication information received by the second obtaining means  21121 . Specifically for example, if the second transmitting means  2111  of the mobile terminal  21  uses the corresponding relationship of the subcarriers and the transmitting antennas shown in  FIG. 3   a , and the uplink signal quality related information from the base station indicates that, the quality of the signal transmitted over TX_ 21   a  is a few dB higher than that of the signal transmitted over TX_ 21   b , the determining means  21122  at the mobile terminal  21  adjusts the distribution of the plurality of subcarriers on the two transmitting antennas. For example, the ratio of 1:1 (two antennas go halves in the total subcarrier) shown in  FIG. 3   a  is adjusted to 2:1 or even higher. Optionally, the mobile terminal may also prestore a plurality of information indicating the different corresponding relationships between the subcarriers and the transmitting antennas, and properly selects therefrom according to the uplink signal quality related information. 
         [0076]    According to a variant of the situation above, the base station instead of the mobile terminal  21  may determine the corresponding relationship between the subcarriers and the transmitting antennas TX_ 21   a  and TX_ 21   b  in the following time period, thus, the information transmitted to the mobile terminal  21  by the base station is the specific corresponding relationship between each subcarrier and the corresponding transmitting antenna; or the number of the available subcarriers on each antenna, while the determining means  21122  of the mobile terminal  21  may determine on its own which antenna use which subcarrier. 
         [0077]    In this example, it can be seen that there are differences between the execution cycles of the First obtaining means  2112  and the second transmitting means  2111 . If there is more uplink data, the second transmitting means  2111  is actually performing constantly, while the first obtaining means  2112  is performing preferably at a determined period. It should be understood by those skilled in the art, if the period is too long, the system may be unable to timely response to the sudden degradation of the channel etc., which leads to mass of data being transmitted over antenna with extremely bad channel conditions, therefore the base station is unable to receive properly. Likely, if the period is too short, the requirement to the processing ability of the mobile terminal is too high, which may therefore result in the increment of the feedback as it is preferably carried out based on the uplink signal quality related information. 
         [0078]    It should be understood by those skilled in the art, the corresponding relationship between each subcarrier and the transmitting antennas may be statically configured, for example, subcarriers No.  0 - 5 , No.  12 - 17  may be statically corresponding to TX_ 21   a , while subcarriers No.  6 - 11 , No.  18 - 23  may be statically corresponding to TX_ 21   b . Thus, the first obtaining means  2112  may be omitted. Furthermore, the mobile terminal  21  may also prestore a plurality of information indicating the different corresponding relationships between the subcarriers and the transmitting antennas, and periodically switch the used corresponding relationship, in this case, the first obtaining means  2112  may also be omitted. 
         [0079]    The QAM modulated data symbols, the pilot symbols generated by the pilot symbol generator are together modulated with the subcarrier, therefore the multi-path subcarrier modulated symbols are obtained. Wherein, since certain subcarrier is corresponding to certain specific transmitting antenna, date symbols or pilot symbols modulated by certain subcarrier are queued on the corresponding transmitting antenna. Thus, two paths of subcarrier modulated symbols are generated. It should be understood by those skilled in the art, the above subcarrier modulation may be implemented by the second transmitting means  2111 , or be implemented by another means. 
         [0080]    The second transmitting means  2111  transmits the above two paths of subcarrier modulated symbols over the corresponding transmitting antenna to the base station. 
         [0081]    As shown in  FIG. 3   a , except for the idle subcarriers, each RU may carry 10 data symbols or pilot symbols, and in the above embodiment, the data symbols carried by the shown six RUs are different from each other. According to a variant of the embodiment, wherein, the data rate is half of that in the previous embodiment, namely, the data symbols carried by RU 1  and RU 2 , by RU 3  and RU 4 , by RU 5  and RU 6  are respectively the same, the remaining general data symbols are buffered temporarily for later transmission. Thus, same data symbols are transmitted over the two transmitting antennas of the mobile terminal  21 , with the subcarrier used being different. Extra frequency diversity may be introduced, of course, the price of which is the decrease of data rate. 
         [0082]    The procedure in the mobile terminal  22  shares the same principle with the mobile terminal  21 , thus, no more details will be given here. However, preferably, the first pilot pattern used by the mobile terminal  21  is different from the second pilot pattern used by the mobile terminal  22 . More preferably, the first pilot pattern and the second pilot pattern are orthogonal to each other. 
         [0083]    In the present invention, preferably, each transmitting antenna transmits using full power. Thus, in comparison with the prior art shown in  FIG. 1 , the antenna transmitting power averaged to each subcarrier is higher, thus the advantage of transmitting power gain is obvious. 
         [0084]    According to a different embodiment of the invention, under the permission of the conditions such as the equipment size etc., the mobile terminal may have more than two transmitting antennas, for example, four or even eight. Then, the implementation manner of the present invention is more flexible, for example, if one OFDM symbol comprises 8 RUs, while the mobile terminal has 4 antennas, then the first and the fifth RUs may be transmitted over the first transmitting antenna, and the second and the sixth RUs may be transmitted over the second transmitting antenna, and the third and the seventh RUs may be transmitted over the third transmitting antenna, and the fourth and the eighth RUs may be transmitted over the fourth transmitting antenna, and the base station may have only one pilot pattern assigned to the mobile terminal. Alternatively, the first, third, fifth and seventh RUs may be transmitted over the first and second transmitting antennas, and the second, fourth, sixth and eighth RUs may be transmitted over the third and fourth transmitting antennas, and the base station may have one pilot pattern or a plurality of orthogonal pilot patterns assigned to the mobile terminal. For example, the first and the third transmitting antennas share one pilot pattern, and the second and the fourth transmitting antennas share another pilot pattern. Other equivalents or obvious variants of these two examples may also achieve the same technical effect, and won&#39;t he further described. 
         [0085]    In the embodiment where a plurality of pilot patterns are assigned to one mobile terminal by the base station, in order to implement channel estimation, the pilot patterns assigned to different mobile terminals by the base station are different. According to each pilot pattern known previously, the pilot paring means  1111  at the base station may parse out the pilot signals transmitted using different pilot patterns from the uplink signals transmitted by the plurality of mobile terminals, so that the processing means  1112  performs channel estimation for each uplink channel, and parses the subsequent uplink signals more preciously. Basically, the introduction of the invention has no influence on the receiver of the uplink counterpart device such as base station. The uplink signal transmitted according to the present invention may be received and parsed using the existing receiver based on ML or MMSE. 
         [0086]      FIG. 7   a  and  FIG. 7   b  shows a comparison between the simulation results of the present invention and the prior art. Table 1 shows the various conditions of the simulation. Four VMIMO technologies are compared in  FIG. 7   a , wherein the base station has two receiving antennas, while  FIG. 7   b  compares these four VMIMO technologies under the condition that the base station has four receiving antennas. It can be clearly seen from  FIGS. 7   a  and  7   b , the curve of the Block Error Ratio (BLER) against the Signal to Noise Ratio (SNR) implemented by the solution provided in this invention is the steepest, which means extra diversity gain is implemented in this invention in comparison with the other solution. Under the consideration of the power gain of the transmitting antenna, besides the shown diversity gain, the present invention provides an extra gain of 3 dB in comparison with basic VMIMO and TSTD based MIMO. 
         [0000]    
       
         
               
             
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Simulation conditions 
               
             
          
           
               
                 Parameter 
                 Assumption 
               
               
                   
               
               
                 OFDM parameter 
                 Carrier frequency = 2.5 GHz 
               
               
                   
                 FFT size = 1024: CP length = 128 samples 
               
               
                   
                 WiMAX uplink, PUSC permutation 
               
               
                 Channel model 
                 3GPP SCME-Urban Micro, 30 kmph 
               
               
                 Channel coding 
                 CTC, coding = 1/2 
               
               
                 Modulation scheme 
                 16QAM 
               
               
                 Transmitting power of each  
                 Total transmit power is the same for  
               
               
                 MS 
                 all the four schemes 
               
               
                 Path loss offset between to  
                 0 
               
               
                 MSs and BS 
                   
               
               
                 Antenna configuration 
                 2 or 4 Rx with antenna spacing of 4λ at the 
               
               
                   
                 BS side 
               
               
                   
                 2 Tx with antenna spacing of 0.5λ at the 
               
               
                   
                 MS side 
               
               
                 Channel estimation 
                 Realistic channel estimation 
               
               
                   
               
             
          
         
       
     
         [0087]    Only a preferable embodiment of the present invention has been described above, however the scope of the present invention is not limited thereto. Alternations or replacements within the technical scope of the disclosure of the invention which easily occur to those skilled in the art should be covered in the scope of the invention. Thus, the scope of the present invention is defined by the appended claims.