WO2008128439A1 - Procédé et dispositif pour réduire le nombre de bits de précodage par rétroaction en fonction d'une recherche de livre de codage dans un système mimo-ofdm - Google Patents

Procédé et dispositif pour réduire le nombre de bits de précodage par rétroaction en fonction d'une recherche de livre de codage dans un système mimo-ofdm Download PDF

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Publication number
WO2008128439A1
WO2008128439A1 PCT/CN2008/000819 CN2008000819W WO2008128439A1 WO 2008128439 A1 WO2008128439 A1 WO 2008128439A1 CN 2008000819 W CN2008000819 W CN 2008000819W WO 2008128439 A1 WO2008128439 A1 WO 2008128439A1
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Prior art keywords
codebook
subchannel
vector
precoding
search
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PCT/CN2008/000819
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English (en)
Chinese (zh)
Inventor
Bo Yang
Feng She
Hanwen Luo
Renmao Liu
Chongguang Yan
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Shanghai Jiao Tong University
Sharp Kabushiki Kaisha
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Publication of WO2008128439A1 publication Critical patent/WO2008128439A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0417—Feedback systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0636—Feedback format
    • H04B7/0639—Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection

Definitions

  • the present invention relates to a precoding method and apparatus, and more particularly to a method and apparatus for reducing the number of precoding feedback bits based on codebook search in a MIMO-OFDM system. Used in the field of wireless transmission technology. Background technique
  • MIMO multiple-input multiple-output
  • OFDM Orthogonal Frequency Division Multiplexing
  • the precoding technique is based on the fading characteristics of the wireless channel.
  • the weighted manner makes the transmitted signal better overcome the channel-to-signal fading, and better tracking the channel state change is a good method to improve the performance of the MIMO system.
  • Research on precoding techniques has focused on how to improve the performance of precoding in cases where channel state is not fully known and how to reduce the amount of precoding feedback information.
  • the related methods of channel state information precoding technology are known at present -
  • the MIMO channel matrix is subjected to singular value (SVD) decomposition, and the obtained singular value vector is used to precode the signal, which is a method for theoretically obtaining optimal performance.
  • the calculated singular value vector is completely fed back to the transmitting end, and the amount of feedback information is quite large. See the literature: David J. Love et al, "Limited Feedback Precoding for Spatial Multiplexing Systems", IEEE Global Telecommunications Conference, 2003. GLOBECOM ' 03. Volume 4, 1-5 Dec. 2003 Page(s): 1857- 1861.
  • the transmitter can complete the precoding by simply feeding back the codebook vector sequence number, so that the number of precoding feedback information bits can be effectively reduced, but the performance is It will decrease relative to 1 and the degree of decline depends on the design of the codebook and the size of the codebook. See literature: Shengli Zhou et al., "BER Criterion and Codebook Construction for Finite-Rate Precoded Spatial Multiplexing with Linear Receivers", IEEE Transactions on Signal Processing, Volume 54, Issue 5, May 2006 Page(s): 1653-1665.
  • Interpolation Group OFDM subchannels, each group containing the same number of subchannels; for the first subgroup of each group Channel, search for the precoding vector in the codebook; for each subchannel of each group, using the correlation, the interpolation algorithm is used to calculate the precoding vector. See the literature: Jihoon Choi et al., "Interpolation based Transmit Beamforming for MIMO-OFDM with Limited Feedback", IEEE Transactions on Signal Processing, Volume 53, Issue 11, Nov.
  • the object of the present invention is to overcome the deficiencies in the prior art, and provide a method and apparatus for reducing the number of precoding feedback bits based on codebook search in a MIMO-OFDM system, so that the number of feedback bits is further In the case of reduction, substantially the same bit error rate performance as the subspace search algorithm is obtained.
  • the proposed algorithm has robust performance and is easy to implement.
  • the invention is achieved by the following technical solutions:
  • the present invention relates to a method for reducing the number of precoding feedback bits based on codebook search in a MIMO-OFDM system.
  • the technical solution is: first performing singular value (SVD) decomposition on all MIMO subchannel matrices according to channel state information, and extracting each OFDM subchannel for each OFDM subchannel.
  • SVD singular value
  • the maximum singular value of the corresponding MIMO channel matrix secondly, find the poles of the curves where the singular values are located; after that, the subchannels corresponding to the poles are according to certain criteria (such as the maximum signal-to-noise ratio criterion of the received signal, the maximum likelihood criterion, the minimum Singular value criterion, minimum mean square error criterion, maximum channel capacity criterion, etc.) Search the codebook to obtain the corresponding precoding codebook vector sequence number; for the subchannel corresponding to the non-pole point, divide into several groups according to the pole position, each group is poled Corresponding to the start of the subchannel, the precoding codebook vector of the pole corresponding channel is used as the starting center vector, and the precoding codebook vector of the subchannel corresponding to the non-pole is obtained by the subcodebook structure and the search method.
  • certain criteria such as the maximum signal-to-noise ratio criterion of the received signal, the maximum likelihood criterion, the minimum Singular
  • the method for reducing the number of precoding feedback bits based on codebook search in the MIMO-OFDM system of the present invention comprises the following steps:
  • Step 1 Perform singular value (SVD) decomposition on the MIMO channel matrix corresponding to each OFDM subchannel according to the channel state information, and extract the maximum value of all the singular values for further application in the next step.
  • SVD singular value
  • Step 2 According to the order of the OFDM subchannels, depending on the correlation between the subchannels, the maximum singular value corresponding to all the subchannels can be regarded as a point on a smooth curve. Find the poles in these points and record the corresponding subchannel number. The singular value (at the boundary) corresponding to the first subchannel is always considered to be a pole. The singular value (at the boundary) corresponding to the last subchannel is not counted.
  • Step 3 Search for the complete codebook for the subchannel corresponding to the pole according to certain criteria (such as the maximum signal to noise ratio criterion, the maximum likelihood criterion, the minimum singularity criterion, the minimum mean square error criterion, the maximum channel capacity criterion, etc.) , obtain the corresponding complete codebook precoding vector sequence number.
  • certain criteria such as the maximum signal to noise ratio criterion, the maximum likelihood criterion, the minimum singularity criterion, the minimum mean square error criterion, the maximum channel capacity criterion, etc.
  • Step 4 For the non-pole corresponding subchannel, divide all OFDM subchannels into groups according to the subchannel numbers corresponding to the poles found in step 2. Each group starts with a pole corresponding subchannel and ends before the next pole. Subchannel. A subcodebook construction and a search algorithm are applied to each subchannel group until a suitable subcodebook vector is found for each non-pole corresponding subchannel.
  • the subcodebook construction includes the following steps: Step 1. Determine the number of bits to be fed back by the non-pole corresponding subchannel. Determine the number of feedback bits, and determine the size of the subcodebook;
  • Step 2 The subcodebook is constructed by using the codebook vector obtained by the previous subchannel as a core, searching the codebook of the entire precoding vector according to the minimum chord criterion, and finding a codebook vector that satisfies the criterion, then the vector is a sub a vector in the codebook;
  • Step 3 The pre-coded sub-codebook vector is obtained by using a method for searching a sub-codebook for the sub-channel corresponding to the pole, and the sub-codebook vector sequence number is recorded.
  • the initial subchannel of the group that is, the subchannel corresponding to a certain singular value
  • obtain a complete codebook vector vv and the sequence number of the vector in the complete codebook is .
  • the subcodebook is searched for the second subchannel according to the same criteria as step three ⁇ (Wj e W ⁇ , the subcodebook number of the vector is: repeating step 2 with ⁇ as the core to construct a subcodebook for the next non-pole corresponding subchannel, and obtaining subcodes for all non-pole corresponding subchannels in the subchannel group This vector.
  • the search subcodebook is based on the same criteria as the application of the pole corresponding subchannel codebook search.
  • the OFDM subchannel is divided into groups according to the above step 4, and when the channel is relatively flat in the frequency domain, the subchannel grouping method based on the full codebook search is adopted:
  • the entire codebook is searched according to the criteria for all subchannels according to the requirements, and the precoding codebook vector of each subchannel is obtained.
  • the number M of different codebook vectors in the same packet is determined, and the preamble of the first subchannel is determined.
  • the codebook vector is centered, and the entire codebook is searched according to the same criteria as before, and M codebook vectors satisfying the criterion including the center vector are found; again, starting from the first subchannel, in the order of subchannels, Comparing the codebook vector of each subchannel with the obtained M codebook vectors.
  • the subchannel belongs to the same packet until the codebook vector of the found subchannel m does not belong to Up to now, all the previous subchannels belong to the first group; and then based on the codebook vector of the subchannel m, a new M codebook vector is constructed according to the same criteria as before, and the code of the subsequent subchannel is used. This vector is compared with M to obtain the second packet, and so on, until all subchannels are grouped. Finally, when feedback is used, position difference can be used. As feedback information, It is also possible to construct and search a subcodebook for each subchannel group except the first subchannel.
  • the method of the position difference forms the feedback information, which is: synthesize the complete codebook vector sequence number obtained by starting the subchannel of each subchannel group and the number of subchannels included in the subchannel group, and feed back the synthesized information to the transmitting end.
  • the transmitting end may extract, from the received synthesized information, the complete codebook vector sequence number of each group of starting subchannels and the number of subchannels included in the subchannel group; for each subchannel of each subchannel group, no information is fed back. Instead, precoding is performed using the same precoding codebook vector as each set of starting subchannels.
  • step 5 the complete codebook vector sequence number is fed back to the subchannel corresponding to the singular value pole, and the subcodebook vector sequence number is fed back to the subchannel corresponding to the non-pole point.
  • the precoding vector is obtained from the codebook according to the feedback information at the transmitting end, and the transmitted signal is precoded using the precoding codebook vector.
  • the transmitter receives the same precoding vector codebook and the same subcodebook vector numbering rule on both the receiving end and the transmitting end, and the transmitting end extracts the precoding vector sequence number from the feedback information.
  • the process includes: first, extracting a complete codebook vector sequence number of the subchannel corresponding to the pole, according to the sequence number, obtaining a corresponding precoding vector from the complete codebook; second, extracting a subcodebook of the non-pole corresponding subchannel The vector sequence number, repeating the subcodebook construction process in step 5, constructing the subcodebook, and extracting the required precoding vector from the subcodebook according to the subcodebook vector sequence number.
  • the present invention relates to a receiving end device technical solution for reducing the number of precoding feedback bits based on codebook search in a MIMO-OFDM system, including:
  • a channel state information acquiring unit acquiring channel state information
  • the channel state tracking unit extracts the maximum singular value of the corresponding MIMO channel matrix for each OFDM subchannel according to the channel state information acquired by the channel state acquiring unit, and treats the maximum singular value as a smooth according to the order of the OFDM subchannels. The point on the curve, find the pole;
  • a complete code search unit obtaining a pre-coded codebook vector complete codebook sequence number of the subchannel corresponding to the pole;
  • the subcodebook search unit divides the subchannels corresponding to the non-poles into a plurality of groups according to the OFDM subchannel order, and obtains a precoding codebook vector subcode of each group of non-pole corresponding subchannels by using a subcodebook structure and a search method. This serial number;
  • the feedback information synthesizing unit synthesizes the complete code search unit and the subcodebook search unit and performs feedback.
  • the present invention provides a transmitting end device for reducing precoding feedback bit number based on codebook search in a MIMO-OFDM system, comprising: a feedback information processing unit, receiving synthesized feedback information, and receiving and receiving The same method used by the end device is constructed as a subcodebook;
  • the precoding vector extracting unit extracts the complete codebook serial number, obtains a corresponding precoding vector in the entire codebook, extracts the subcodebook serial number, and obtains a corresponding precoding vector in the constructed subcodebook.
  • the above steps of the method of the present invention are accomplished by the cooperation of the transmitting end device and the receiving end device.
  • the transmitting device includes a feedback information processing unit and a precoding vector extracting unit. After receiving the information transmitted by the transmitting device, the receiving end completes a series of tasks such as channel state information acquisition, channel change tracking, codebook search, and feedback information synthesis, and transmits the feedback information; after the transmitting device receives the feedback information, The tasks such as feedback information processing, precoding vector extraction, and the like are completed, and the data to be transmitted is precoded using the extracted precoding vector to finally form transmittable information.
  • the corresponding relationship between the functional unit of the foregoing apparatus and the implementation steps of the method of the present invention is: the receiving end channel state information acquiring unit and the channel change tracking unit complete the grouping of the subchannels in step 1, step two and step four; the codebook search unit completes the steps The three complete codebook search and step four subcodebook construction and search; the feedback information synthesis unit, and the transmitter feedback information processing unit completion and the precoding vector extraction unit together complete step five.
  • the present invention combines the subcodebook construction based on codebook search and the search precoding method with the singular value decomposition of the MIMO channel. Compared with the subspace search method, the present invention makes better use of the correlation between OFDM subchannels.
  • the system bit error rate performance comparable to the subspace search method can be obtained with fewer feedback bits.
  • the invention has better flexibility, can better track the changing trend of the channel state through singular value decomposition, and is very suitable for practical applications, and can be the third generation (3G), the super third generation (B3G), the fourth generation ( 4G) Cellular mobile communication and precoding schemes for systems such as digital television, wireless local area networks, and wireless wide area networks provide important theoretical basis and specific implementation methods.
  • Figure 1 is a schematic diagram of a MIMO-OFDM system with transmit precoding and receive combining.
  • Figure 2 is a schematic diagram of the actual system device
  • FIG 3 is a flow chart of a search process for a precoding codebook vector sequence number of a subchannel group
  • Figure 4 is a graph of the maximum singular value of the MIMO subchannel of the MIMO-OFDM system (Rayleigh channel model)
  • Figure 5 is a graph showing the maximum singular value variation of a MIMO subchannel in a MIMO-OFDM system (3GPP spatial channel model)
  • Figure 6 is a simulation curve of BER performance of multipath Rayleigh channel model.
  • Figure 7 is a comparison of the number of feedback bits in the multipath Rayleigh channel model.
  • Figure 8 is a simulation graph of BER performance of 3GPP spatial channel model.
  • 9 is a comparison graph of feedback bit numbers in a 3GPP spatial channel model.
  • the structure of a MIMO-OFDM system with transmit precoding and reception combining is as shown in FIG. 1.
  • the present invention adopts a MIMO-OFDM system with transmission precoding and reception combining with 4 transmissions and 2 receptions, and the number of subcarriers is 64.
  • Adopt QPSK modulation method The channel state information is obtained at the receiving end, and the present invention does not relate to a specific acquisition mode.
  • the codebook search algorithm unit searches the codebook by using channel state information, and finally forms precoding feedback information.
  • the transmitting end performs precoding of the transmitted signal according to the feedback information.
  • a multi-path Rayleigh channel model and a 3GPP spatial channel model are used for system-level performance simulation.
  • the multipath Rayleigh channel model has a channel multipath number of 3, and its normalized power and delay parameters are [1 l/ exp (l) l/ eX p(2)], where exp(a) represents the natural logarithm The base of the alpha power.
  • exp(a) represents the natural logarithm The base of the alpha power.
  • Use the basic 4 transmit and receive "Urban Micro" model in the 3GPP spatial channel model.
  • UMTS Universal Mobile Telecommunications System
  • MIMO Multiple Input Multiple Output
  • Receiver user Us includes channel status information a unit CSIU, a channel change tracking unit CTU, a codebook search unit including a complete codebook search unit CBSU and a subcodebook search unit SCBSU, and a feedback information synthesis unit FBIU;
  • the base station B includes a feedback information processing unit FBIU and a precoding vector Extract unit PCVU.
  • the user US After receiving the information FWI transmitted by the base station B, the user US completes a series of tasks such as channel state information acquisition, channel change tracking, codebook search, and feedback information synthesis, and transmits the feedback information FBI; after receiving the feedback information FBI, the base station B receives the feedback information FBI. And completing tasks such as feedback information processing, precoding vector extraction, and precoding the data to be transmitted using the extracted precoding vector to finally form the transmittable information FWI.
  • the present invention does not relate to the design problem of the codebook. All simulations, analysis and descriptions of the present invention use a codebook containing 64 precoding vectors as shown in the following table. The number of precoding vectors in the codebook is above the vector. The contents of the table are as follows:
  • the process of the present invention is performed by a Channel State Information Acquisition Unit (CSIU), Channel Change Tracking Unit (CTU).
  • CSIU Channel State Information Acquisition Unit
  • CTU Channel Change Tracking Unit
  • the singular value decomposition of the MIMO channel matrix corresponding to the A OFDM subchannel can be expressed as:
  • the search of the precoding codebook and the construction of the subcodebook are the core of the present invention by using the variation rule of the maximum singular value of the MIMO subchannel matrix.
  • Figure 4 shows the Rayleigh channel model. In the case of the MIMO subchannel matrix, the maximum singular value of the curve is changed.
  • FIG. 5 is a diagram showing changes in the curve of the maximum singular value of the MIMO subchannel matrix in the case of using the 3GPP spatial channel model.
  • the search of the codebook may be based on one of the criteria of the received signal SNR maximum criterion, the maximum likelihood criterion, the minimum singular value criterion, the minimum mean square error criterion, and the channel capacity maximum criterion.
  • the invention will describe the codebook search process according to the maximum signal to noise ratio criterion of the received signal.
  • the maximum likelihood criterion, the minimum singular value criterion, the minimum mean square error criterion, and the maximum channel capacity criterion are briefly introduced. The introduction of these guidelines can also be found in the literature: Love, DJ, Heath, RW, Jr., "Limited feedback unitary precoding for spatial multiplexing systems," IEEE Trans. Info. Theo. Vol 51 (8), Aug. 2005 Page (s): 2967 - 2976.
  • the maximum likelihood criterion for a codebook search is:
  • ⁇ ar g ma X i / min /i .
  • ⁇ represents a set of modulation constellations; represents a received signal; a symbol transmitted by a table; a symbol representing a decision output at the receiving end; represents a codebook vector.
  • This criterion corresponds to a linear receiver.
  • the zero-forcing receiver is a kind of linear receiver.
  • the lower limit of the minimum signal-to-noise ratio of zero-forcing reception can be expressed as: SW? min ⁇ in , where l middy is the smallest singular value of Hw.
  • the minimum singular value criterion for codebook search is: is the transmitted signal signal noise
  • the minimum mean square error receiver is another form of linear receiver.
  • the mean square error of the received signal can be expressed as:
  • the maximum channel capacity criterion for the codebook search is: w ⁇ argmaxC u
  • the above N Q represents Noise variance.
  • the process of the present invention is performed by a codebook search unit comprising a complete codebook search unit (CBSU) and a subcodebook search unit (SCBSU).
  • the present invention employs the above code containing 64 precoding vectors.
  • the codebook search is described based on the maximum signal to noise ratio criterion.
  • the complete codebook can be expressed as
  • H(A:) is the A: MIMO channel matrix of the OFDM subchannel, which is the transmitted signal
  • "() is additive white Gaussian noise.
  • an optimal precoding codebook vector is searched in the complete codebook, that is, for a codebook containing 64 precoding vectors.
  • the number of bits that need to be fed back for the subchannel corresponding to each pole is 6.
  • the subchannels are grouped, each group starting with a subchannel corresponding to the pole, and terminating the subchannel before the next pole.
  • the search process for a precoding codebook vector for a subchannel group is shown in FIG. In order to reduce the number of feedback bits, a subcodebook construction and a search method are adopted for the non-pole corresponding subchannel.
  • the complete codebook vector obtained by the subchannel according to the maximum signal to noise ratio criterion is M. If it is desired to enable the remaining non-pole corresponding subchannels in the subchannel group to feed back 1-bit precoding information, the subcodebook is a codebook containing two codebook vectors.
  • the construction of the subcodebook will be described based on the shortest pitch criterion. For example, for a subchannel adjacent to a pole corresponding to a subchannel, the subcodebook structure searches for the entire codebook for the core, and finds a vector w that makes the chord distance d( Wl , W/ ) the shortest, such that w and together constitute
  • the precoding codebook vector of the previous subchannel is the core, and the entire codebook is searched for the vector construct subcodebook with the shortest distance from the core chord, until the subcodebook is obtained for all subchannels. If it is desired to feed 2 bits of precoding information to the remaining non-pole corresponding subchannels in the subchannel group, the subcodebook is a codebook containing 4 codebook vectors. The composition can still be based on the shortest pitch theorem, but the selected codebook vector is the three vectors that are relatively shortest to the core vector in the entire codebook.
  • the subchannel grouping method based on the full codebook search is very effective for channels that are relatively flat in the frequency domain.
  • the specific method is: First, searching for the entire codebook for all subchannels according to certain criteria (such as received signal SNR maximum criterion, maximum likelihood criterion, minimum singularity criterion, minimum mean square error criterion, channel capacity maximum criterion, etc.) Obtaining a precoding codebook vector for each subchannel; second, determining the number M of different codebook vectors in the same packet, the value M affecting system performance and feedback overhead; again, precoding with the first subchannel m Q
  • the codebook vector is centered, and the entire codebook containing 64 precoding vectors can be searched by the minimum chord criterion to find the M codebook vectors including the center vector and the core vector chord.
  • the feedback information can be formed by using the position difference, that is, each packet only needs to feed back the codebook vector of the first subchannel (m Q , m, , m 2 , ) in the group and the within the group.
  • the size of M can be determined according to system requirements.
  • the configuration and search of the subcodebook may be performed for each subchannel group except the first subchannel.
  • the feedback information formed by the position difference method is composed of some two-dimensional vectors.
  • the codebook vector number obtained by searching for the maximum signal to noise ratio criterion for all subchannels is: [5 5 5 5 5 5 5 5 5 50 50 50 54 54 54 54 54 18 18 18 18 18 18 18 26 5 5 5 5 5 5 5 5 17 52 52 52 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 5 5 5 5 5 5 5 5 5 5 5 5 5].
  • the subchannel grouping situation obtained by the above grouping method is: 0 to 7, 8 to 10, 1 to 14 , 15 to 23, 24, 25 to 32, 33, 34 to 36, 37 to 47, 48 to 63, 10 groups.
  • Feedback can be formed by feeding back a two-dimensional vector consisting of the codebook vector number corresponding to each group of subchannels and the number of subchannels included in the subchannel group: [(5, 8), (50, 3), (54, 4), ( 18, 9), (26, 1 ), (5, 8), (17, 1 ), (52, 3), (25, 11 ), (5, 16)], this information can uniquely reflect the current The search situation of the code vector codebook. If the codebook vector number and the position difference information are both 6-bit coded, the total number of bits of feedback information at a certain time is about 120.
  • the premise of the subcodebook search is to encode the codebook vector in the subcodebook according to certain rules.
  • the numbering rule is flexible, and the present invention is not particularly limited. Only the numbering rule is required to be followed by both the receiving end and the transmitting end.
  • the subcodebook search process is the same as the process of searching the entire codebook, and is based on the same criteria (such as the received signal SNR maximum criterion, the maximum likelihood criterion, the minimum singularity criterion, the minimum mean square error criterion, the channel capacity maximum criterion, etc.) ).
  • a feedback data stream is formed, taking a subchannel group containing 9 subchannels as an example: setting the first subchannel of the subchannel group, That is, the sub-channel corresponding to the pole, the complete codebook vector number obtained by searching the complete codebook is 60.
  • the remaining eight subchannels, that is, the subchannels corresponding to the non-poles, search for the subcodebooks that are constructed according to the subcodebook construction method (the subcodebook is generated by using one bit), and the subcodebook vector numbers are respectively: No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, No. 0, No. 0, No. 0.
  • the feedback information is [60, 1 , 1, 1, 1 , 1, 0, 0, 0, 0]. In practical systems, this process is done by the Feedback Information Synthesis Unit (FBIU).
  • FBIU Feedback Information Synthesis Unit
  • the transmitting end After receiving the feedback information, the transmitting end (the feedback information processing unit (FBIU) and the precoding vector extracting unit (PCVU)) first extracts the codebook vector serial number 60, that is, the codebook vector serial number of the pole corresponding subchannel. According to the serial number, the transmitting end can extract the 60-number vector from the complete codebook. Subsequently, the transmitter extracts the subcodebook vector sequence numbers 1, 1, 1, 1, 1, 0, 0, 0.
  • the transmitter Before extracting the subcodebook vector according to the subcodebook vector sequence number, the transmitter must first Applying the subcodebook construction method introduced above, constructing a corresponding subcodebook for the subchannel corresponding to the pole, and numbering the vector in the subcodebook using the same rule, and then based on the subcode extracted from the feedback information The vector sequence number extracts the sub-codebook vector from the corresponding sub-codebook.
  • This embodiment is based on the multipath Rayleigh channel model described above.
  • the channel state is quasi-static, that is, the channel state is constant during the transmission of a data packet.
  • the data used in this case contains 1920 data bits, and generates a packet containing 960 symbols through symbol mapping and QPSK modulation.
  • the feedback generating unit performs singular value decomposition, pole search, codebook search, subchannel grouping, subcodebook generation, subcodebook search, forming a precoding codebook sequence according to the channel state information. Feedback information bits and other processes.
  • This embodiment uses 1 bit to generate a subcodebook, i.e., each subcodebook contains 2 codebook vectors.
  • the precoding codebook sequence number feedback information bit arrives at the transmitting end via the feedback channel.
  • the signal at the transmitting end is OFDM modulated and forms four signals ready to be loaded into the four transmitting antennas.
  • the precoding function unit selects the precoding codebook vector from the codebook according to the precoding code sequence number feedback bit information, and precodes the four channels to be transmitted.
  • the signal is loaded into four transmit antennas, passed through a multipath Rayleigh channel, and received at the receiving end by two receive antennas.
  • the received signals of the two receiving antennas are respectively subjected to OFDM demodulation.
  • the receiving end also extracts the precoding vector from the codebook according to the precoding codebook serial number feedback bit information, and weights and combines the demodulated signals.
  • the combined signal is finally decoded according to the maximum likelihood criterion to obtain data symbols, and the data bits are obtained by QPSK demodulation.
  • the BER performance simulation curve in the multipath Rayleigh channel model shown in Fig. 6 and the feedback bit number comparison curve shown in Fig. 7 show that the present invention obtains and uses a 2-bit generator in the case where the number of feedback bits is reduced by about 43.
  • the subspace search algorithm of the codebook has basically the same bit error rate performance; when the number of feedback bits is reduced by 295 or so, the bit error rate performance is only 0.5 to 2.5 dB loss with respect to the case of completely searching the codebook. .
  • Example 2 This embodiment is based on the above 3GPP spatial channel model.
  • the channel model is a fast fading channel model relative to the multipath Rayleigh channel model described above. Therefore, this embodiment can verify the performance of the present invention under fast fading channel conditions.
  • the specific implementation process of this embodiment is the same as that of Embodiment 1.
  • the error rate performance curve of the 3GPP spatial channel model shown in FIG. 8 and the feedback bit number comparison curve shown in FIG. 9 show that under the condition of the 3GPP spatial channel model, the present invention obtains the case where the number of feedback bits is reduced by about 32. It is slightly better than the bit error rate performance of the subspace search algorithm using 2-bit generation subcodebook; when the number of feedback bits is reduced by 281, 4 times, the bit error rate performance is only 0.5 compared to the case of completely searching the codebook. ⁇ 2dB loss.
  • two obvious fluctuations can be seen from the feedback bit number comparison curve shown in Fig. 9, which is caused by the relatively dramatic change of the 3GPP spatial channel model, which also indicates that the algorithm of the present invention can better track the channel. Change is a more flexible way to reduce the number of bits of precoding feedback information.
  • the above embodiments for different severity of the two changes indicate that the algorithm of the present invention has certain adaptability to different channels.
  • This adaptability is mainly reflected in the fluctuation characteristics of the instantaneous feedback bit number.
  • the trend of fluctuation is that when the channel changes more intensely, the number of feedback information bits will increase; when the channel changes more smoothly, the number of feedback information bits will decrease or remain stable.
  • This adaptability also proves that the algorithm of the present invention can better track the channel change, and is a method for considering the channel variation and reducing the number of feedback information bits.

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Abstract

La présente invention concerne un procédé et un dispositif destinés à réduire le nombre de bits de l'information de précodage par rétroaction en fonction d'une recherche de livre de codage dans un système MIMO-OFDM qui sont utilisés dans la communication d'interface d'espace entre un utilisateur et une station de base. L'utilisateur est doté de : une unité d'acquisition d'information d'état de canal ; une unité de suivi de modification de canal qui soustrait une valeur singulière maximale de matrice de canal MIMO pour chaque sous-canal OFDM selon des informations d'état de canal, tout en considèrant la valeur singulière maximale comme des points sur une courbe régulière selon l'ordre de sous-canaux OFDM et trouve le pôle ; une unité de recherche de livre de codage qui cherche l'intégralité du livre de codage du sous-canal correspondant au pôle, obtient le numéro de série du vecteur de précodage du livre de codage entier correspondant, divise les sous-canaux correspondant au non-pôle en plusieurs groupes selon l'ordre des sous-canaux OFDM, obtient la quantité approprié du nombre sériel de sous-livre de codage pour ces sous-canaux correspondant au non-pôle de chaque groupe par le biais du procédé de la recherche et de la construction de sous-livre de codage ; et une unité de synthétisation d'informations de rétroaction qui rétroagit les informations obtenues d'une série de nombre sériel de vecteur de livre de codage au terminal transmetteur.
PCT/CN2008/000819 2007-04-19 2008-04-21 Procédé et dispositif pour réduire le nombre de bits de précodage par rétroaction en fonction d'une recherche de livre de codage dans un système mimo-ofdm WO2008128439A1 (fr)

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