CN101039137A - Method and system for reducing codebook search-based precoding feedback bits of MIMO-OFDM system - Google Patents

Abstract

Provided is a MIMO-OFDM system codebook search based reducing procode feedback information bit number method and device which is used in the air interface communication between users and the base station. The users include the channel state information acquisition unit and a channel variation tracing unit. According to the channel state information, the corresponding largest singular values of MIMO channel matrix are extracted from each OFDM sub channel and according to the sequence of OFDM sub channel, the largest singular values can be viewed as points on a smooth curve and the pole can be found. The codebook search unit searches the complete codebook to the sub channel corresponding to the pole and obtains the corresponding complete codebook procode vector serial number. The sub channeles which ar not corresponded to the pole are divided into a number of groups according to the sequence of OFDM channel, and the construction and searching methods of sub codebook are used to obtain the procode codebook vector sub codebook serial number for each group of sub channels which are not corresponded to the pole. The feedback information integration unit feedbacks the series of codebook vector serial number information to the transmitting end.

Description

The MIMO-OFDM system reduces the method and the device of precoding feedback bits number based on codebook search

Technical field

The present invention relates to a kind of method for precoding and device, specifically is a kind of MIMO-OFDM system reduces the precoding feedback bits number based on codebook search method and apparatus.Be used for radio transmission technical field.

Background technology

Use many antennas on transmitter and receiver, promptly constituted multiple-input and multiple-output (MIMO) mode, this transmission means can strengthen the reliability of wireless connections and increase the capacity of wireless communication system.In the wireless environment that disturbance is enriched, for a system that has MT transmit antennas and MR root reception antenna, the MIMO transmission means is that relative with the reception antenna number less numerical value with number of transmit antennas is linear to the contribution that channel capacity improves.For broadband connections, OFDM (OFDM) technology is divided into the flat fading channel of one group of parallel quadrature with frequency-selective channel, has improved the system spectrum utilance greatly, and can effectively overcome the intersymbol string around (ISI).The OFDM technology combines with the MIMO technology, has become the outstanding alternative of following wide-band mobile communication system.

Precoding technique can better overcome the decline of channel to signal at the fading characteristic of wireless channel with the feasible signal that sends of the mode of weighting, better follows the tracks of the variation of channel status, is the good method that improves the mimo system performance.Mainly concentrate at the research of precoding technique and how to improve in the performance of precoding under the incomplete known case of channel status and how to reduce on these two problems of precoding feedback information data volume.The correlation technique of known channel state information precoding technique mainly contains at present:

1. under the situation of receiving terminal known channel state information, the mimo channel matrix is carried out singular value (SVD) to be decomposed, with the singular value vector that obtains signal is carried out precoding, this method is the method that can obtain optimal performance in theory, but the singular value vector that calculates be fed back to transmitting terminal fully, feedback information volume is quite huge.Referring to document: David J.Love etc., " Limited Feedback Precodingfor Spatial Multiplexing Systems ", IEEE Global Telecommunications Conference, 2003.GLOBECOM ' 03.Volume 4,1-5Dec.2003Page (s): 1857-1861.

2. under the situation of receiving terminal known channel state information, from the code book that pre-defines, search out best vector as the precoding weighing vector according to channel condition information according to certain criterion, only need feedback codebook vectors sequence number just can make transmitting terminal finish precoding, thereby can effectively reduce precoding feedback information bits number, but 1. performance with respect to can descending to some extent, and the degree that descends depends on the design of code book and the size of code book.Referring to document: Shengli Zhou etc., " BER Criterion and CodebookConstruction for Finite-Rate Precoded Spatial Multiplexing with LinearReceivers ", IEEE Transactions on Signal Processing, Volume 54, Issue 5, May2006Page (s): 1653-1665.

3. for having big quantum channel ofdm system, even 2. the employing method still needs to feed back and a large amount of finish precoding to all subchannels than special envoy transmitting terminal.At this situation, two kinds of methods that can further reduce the precoding feedback bits number are arranged: (1) interpolation method: the OFDM subchannel is divided into groups every group of subchannel that contains equal number; For first subchannel of every group, search obtains precoding vectors in code book; Other subchannels for every group utilize correlation, and the utilization interpolation algorithm calculates precoding vectors.Referring to document: Jihoon Choi etc., " Interpolation based TransmitBeamforming for MIMO-OFDM with Limited Feedback ", IEEE Transactions onSignal Processing, Volume 53, Issue 11, Nov.2005Page (s): 4125-4135. (2) subspace search method:, search for complete code book for first subchannel and obtain precoding vectors according to the order of OFDM subchannel; For the subchannel of back, want under the prerequisite of feedack bit number determining, utilize correlation, from complete code book, extract the minority codebook vectors and form the subspace, search obtains precoding vectors in the subspace.Referring to document: Shengli Zhou etc., " Recursive and Trellis-basedFeedback Reduction for MIMO-OFDM with Transmit Beamforming ", IEEEGlobal Telecommunications Conference, 2005.GLOBECOM ' 05.Volume 6,28Nov.-2Dec.2005Page (s): 5pp.These two kinds of methods are all utilized the correlation of codebook vectors, the scope that the subspace search method has come down to dwindle codebook search has reduced feedback bits quantity, but 2. the reduction of systematic function is arranged with respect to method, interpolation method is to utilize several precoding codebook vectors that the complete code book of search obtains by calculating other vector, improve the systematic function of complete codebook search precoding, but increased the computational complexity of system.

Summary of the invention

The objective of the invention is to overcome deficiency of the prior art, provide a kind of MIMO-OFDM system to reduce the method and the device of precoding feedback bits number, make it under the situation that number of bits of feedback further reduces, obtain to ask searching algorithm essentially identical bit error rate performance with sub-sky based on codebook search.Algorithm performance that the present invention carries is sane, and is easy to realize.

The present invention is achieved by the following technical solutions:

The present invention relates to the MIMO-OFDM system based on the method and technology scheme that codebook search reduces the precoding feedback bits number is: at first according to channel condition information all MIMO subchannel matrixes are carried out singular value (SVD) and decompose, extract the maximum singular value of its corresponding mimo channel matrix for each OFDM subchannel; Secondly, find the limit of these singular value place curves; Afterwards, according to certain criterion (as snr of received signal maximal criterion, maximum-likelihood criterion, minimum singular value criterion, minimum mean square error criterion, channel capacity maximal criterion etc.) search code book, obtain corresponding precoding codebook vector sequence number for the pairing subchannel of limit; For the pairing subchannel of non-limit, be divided into some groups according to pole location, every group initial with the corresponding subchannel of limit, precoding codebook vector with the limit respective channels is initial center vector, with the method for sub-codebook structure and search obtain non-limit the precoding codebook vector of corresponding subchannel.

MIMO-OFDM of the present invention system comprises the steps: based on the method that codebook search reduces the precoding feedback bits number

Step 1 according to channel condition information, is carried out singular value (SVD) for the pairing mimo channel matrix of each OFDM subchannel and is decomposed, and extracts the maximum in all singular values, so that further use in next step.

Step 2 according to the order of OFDM subchannel, depends on the correlation between subchannel, can be considered as point on the smooth curve to the maximum singular value of all subchannel correspondences.Find out the limit in these points, and write down pairing subchannel sequence number.The pairing singular value of first subchannel (boundary) always is considered to a limit.The singular value (boundary) of last subchannel correspondence does not count.

Step 3, search for complete code book for the pairing subchannel of limit according to certain criterion (as snr of received signal maximal criterion, maximum-likelihood criterion, minimum singular value criterion, minimum mean square error criterion, channel capacity maximal criterion etc.), obtain corresponding complete code book precoding vectors sequence number.

Step 4 for the subchannel of non-limit correspondence, is divided into some groups to all OFDM subchannels according to the subchannel of the limit correspondence that finds in step 2 numbering, every group with the corresponding subchannel of limit as initial, end at the subchannel before the next limit.Each groups of subchannels is used sub-codebook structure and searching algorithm, up to all finding suitable sub-codebook vector for the subchannel of each non-limit correspondence.

Described sub-codebook structure may further comprise the steps:

1. step determines the bit number that the corresponding subchannel of non-limit will feed back.Determine number of bits of feedback, just determined the size of sub-codebook;

Step 2., the structure of sub-codebook is that the codebook vectors that is obtained with last sub-channel is a core, searches for the code book of whole precoding vectors according to smallest chord apart from criterion, finds the codebook vectors that satisfies this criterion, then this vector is exactly a vector in the sub-codebook;

3. step is searched for the method for sub-codebook and is obtained precoding sub-codebook vector for the subchannel employing of non-limit correspondence, and record sub-codebook vector sequence number.

If the initial subchannel that should organize, the pairing subchannel of promptly a certain limit singular value, the complete codebook vectors of acquisition is w _i, the sequence number of this vector in complete code book is i.With w _iFor core makes up sub-codebook W _i, establish W _iComprise 2 ^B2(B ₂Be the required number of bits of feedback of the corresponding subchannel of non-limit) individual codebook vectors, then other codebook vectors in the sub-codebook are with respect to w _iShould satisfy minimum string apart from criterion, make string distance between other vectors and core vector $d(w_i,w_j)=\sqrt{1-{\left|w_i^H{w}_j\right|}^2}$ Minimum.According to the criterion search sub-codebook W identical with step 3 _i, be that second subchannel tried to achieve sub-codebook vector w _j(w _j∈ W _i), the sub-codebook sequence number of this vector is j.With w _jFor 2. the core repeating step is the subchannel constructor code book of next non-limit correspondence, the subchannel of all non-limit correspondences all obtains the sub-codebook vector to the groups of subchannels.The search sub-codebook will foundation and the corresponding subchannel code book of application and the limit identical criterion of criterion of searching for.

Above-mentioned steps four is described to be divided into some groups for when frequency domain changes mild relatively channel with the OFDM subchannel, adopts the subchannel group technology based on complete codebook search:

At first, all subchannels are searched for whole code book according to criterion as required, obtain the precoding codebook vector of each subchannel; Secondly, determine the number M of different codebook vectors in the same grouping, and be the center, search for whole code book, find to comprise that center vector satisfies M codebook vectors of this criterion by the criterion identical with the front with the precoding codebook vector of first subchannel; Once more, from first subchannel, put in order by subchannel, codebook vectors to each subchannel compares with M the codebook vectors that obtains, if the codebook vectors of subchannel belongs in the M collection, then this subchannel belongs to same grouping, and till the codebook vectors that finds subchannel m did not belong to M, so far Yi Qian all subchannels belonged to first grouping; Codebook vectors with subchannel m is the center again, constructs a M new codebook vectors by the criterion identical with the front, uses the codebook vectors of subchannel thereafter and M to compare, and obtains second grouping, so repeatedly, and till all subchannels groupings are finished; At last, during feedback, can adopt the mode of differential position to form feedback information, also can carry out the structure and the search of sub-codebook each groups of subchannels all the other subchannels except that first subchannel.

The mode of described differential position forms feedback information, is meant, the quantity that each groups of subchannels is begun complete codebook vectors sequence number that subchannel obtains and the contained subchannel of this groups of subchannels is synthetic, and this composite signal is fed back to transmitting terminal; Transmitting terminal can extract every group of quantity information that begins complete codebook vectors sequence number of subchannel and the contained subchannel of this groups of subchannels from the composite signal of receiving; Other subchannels for each groups of subchannels do not feed back any information, begin the identical precoding codebook vector of subchannel and carry out precoding and be to use with every group.

Step 5 is for the corresponding subchannel feed back full codebook vectors sequence number of singular value limit, for non-limit institute corresponding subchannel feedback sub-codebook vector sequence number.From code book, obtain precoding vectors at transmitting terminal according to feedback information, use the precoding codebook vector to carry out precoding to transmitting.For certain groups of subchannels, all have identical, complete precoding vectors code book and all observe under the prerequisite of same sub-codebook vector coding rule at receiving terminal and transmitting terminal, transmitting terminal extracts the precoding vectors sequence number from feedback information process comprises: at first, extract the complete codebook vectors sequence number of the subchannel of limit correspondence, according to this sequence number, can from complete code book, obtain corresponding precoding vector; Secondly, extract the sub-codebook vector sequence number of the corresponding subchannel of non-limit, the sub-codebook construction process in the repeating step five, the constructor code book just can extract required precoding vectors according to sub-codebook vector sequence number from sub-codebook.

Based on said method, the receiving end device technical scheme that the present invention relates in a kind of MIMO-OFDM system to reduce based on codebook search the precoding feedback bits number is: comprising:

The channel condition information acquiring unit obtains channel condition information;

The channel status tracking cell, the channel condition information that obtains according to the channel status acquiring unit extracts the maximum singular value of corresponding mimo channel matrix for each OFDM subchannel, and the order of pressing the OFDM subchannel, described maximum singular value is considered as point on the smooth curve, finds out limit;

The full code search unit obtains the complete code book sequence number of precoding codebook vector of the subchannel of described limit correspondence;

The sub-codebook search unit for the subchannel of non-limit correspondence, is divided into several groups in proper order by the OFDM subchannel, obtains the precoding codebook vector sub-codebook sequence number of the subchannel of every group of non-limit correspondence with the method for sub-codebook structure and search;

The feedback information synthesis unit, described full code search unit and sub-codebook search unit is synthetic, and feed back.

Match with above-mentioned receiving end device, the invention provides the transmitting terminal device that reduces the precoding feedback bits number in a kind of MIMO-OFDM system based on codebook search, comprising:

The feedback information processing unit receives synthetic feedback information, and according to becoming sub-codebook with the employed identical method construct of receiving end device;

The precoding vectors extraction unit extracts complete code book sequence number, and obtains corresponding precoding vector in whole code book, extracts the sub-codebook sequence number, and obtain corresponding precoding vector in the sub-codebook of described structure.

The inventive method above-mentioned steps is finished by the cooperation of transmitting end device and receiving end device.Transmitting end device comprises feedback information processing unit and precoding vectors extraction unit.After receiving terminal receives the information of transmitting end device emission, finish a series of tasks such as the obtaining of channel condition information, channel variation tracking, codebook search, feedback information be synthetic, feedback information is launched; After transmitting end device receives feedback information, finish tasks such as feedback information processing, precoding vectors extraction, and use the precoding vectors that extracts that the data of preparing to transmit are carried out precoding, finally form missile information.

The corresponding relation of the functional unit of said apparatus and the inventive method performing step is: in receiving terminal channel condition information acquiring unit and channel variation tracking cell completing steps one, step 2 and the step 4 to the grouping of subchannel; Codebook search unit completing steps three complete codebook searches and step 4 sub-codebook structure and search; The feedback information synthesis unit, and transmitting terminal feedback information processing unit is finished and the common completing steps five of precoding vectors extraction unit.

The present invention will combine with the singular value decomposition of mimo channel based on the sub-codebook structure and the search method for precoding of codebook search, with respect to the subspace searching method, better utilization of the present invention correlation between the OFDM subchannel, thereby can obtain the error rate of system performance suitable with feedback bits still less with the subspace search method.The present invention has better flexibility again, can better follow the tracks of the variation tendency of channel status by singular value decomposition, be well suited for using in the reality, can be the third generation (3G), super three generations (B3G), the 4th generation (4G) cellular mobile communication and the pre-coding scheme of systems such as Digital Television, WLAN (wireless local area network), wireless wide area network important theory foundation and concrete implementation method are provided.

Description of drawings

Fig. 1 has the emission precoding and receives the MIMO-OFDM systematic schematic diagram that merges

Fig. 2 is a real system device schematic diagram

Fig. 3 is the search procedure flow chart to the precoding codebook vector sequence number of a groups of subchannels

Fig. 4 is the MIMO of a MIMO-OFDM system subchannel maximum singular value change curve (Rayleigh channel model)

Fig. 5 is the MIMO of a MIMO-OFDM system subchannel maximum singular value change curve (3GPP space channel model)

Fig. 6 is multipath Rayleigh channel model bit error rate performance simulation curve figure

Fig. 7 is the correlation curve figure of number of bits of feedback under the multipath Rayleigh channel model

Fig. 8 is 3GPP space channel model bit error rate performance simulation curve figure

Fig. 9 is the correlation curve figure of number of bits of feedback under the 3GPP space channel model

Embodiment

Below in conjunction with accompanying drawing embodiments of the invention are elaborated: present embodiment is being to implement under the prerequisite with the technical solution of the present invention, provided detailed execution mode and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

(1) has emission precoding and the structure that receives the MIMO-OFDM system that merges

The structure of the MIMO-OFDM system that has the emission precoding and receive to merge as shown in Figure 1, the present invention adopts having the emission precoding and receiving the MIMO-OFDM system that merges of receiving for 42, the subcarrier number is 64, adopts the QPSK modulation system.Channel condition information obtains at receiving terminal, and the present invention does not relate to concrete obtain manner.The codebook search algorithm unit utilizes channel condition information search code book, finally forms the precoding feedback information.Transmitting terminal is finished precoding to transmitting according to feedback information.For full test the present invention to the error rate of system Effect on Performance, adopt multipath Rayleigh channel model and 3GPP space channel model to carry out system-level performance simulation.The channel multi-path number of multipath Rayleigh channel model is 3, and its normalized power, delay parameter are [11/exp (1) 1/exp (2)], and wherein exp (α) represents α power of the truth of a matter of natural logrithm.Use 42 basic in 3GPP space channel model receipts " UrbanMicro " models, concrete parameter setting please refer to " ETSI TR 125 996 V6.1.0 Universal MobileTelecommunications System (UMTS); Spacial channel model for Multiple InputMultiple Output (MIMO) simulations ".

(2) real system device configuration

As Fig. 2, shown in the real system device schematic diagram.Receiving terminal user Us comprises channel condition information acquiring unit CSIU, and channel variation tracking cell CTU comprises the codebook search unit of complete code book search unit CBSU and sub-codebook search unit SCBSU and feedback information synthesis unit FBIU; Transmitting terminal base station B comprises feedback information processing unit FBIU and precoding vectors extraction unit PCVU.After user Us receives the information FWI of base station B emission, finish a series of tasks such as the obtaining of channel condition information, channel variation tracking, codebook search, feedback information be synthetic, feedback information FBI is launched; After base station B receives feedback information FBI, finish tasks such as feedback information processing, precoding vectors extraction, and use the precoding vectors that extracts that the data of preparing to transmit are carried out precoding, finally form missile information FWI.

(3) precoding codebook

The present invention does not relate to the design problem of code book, and the code book that contains 64 precoding vectors as shown in the table is all used in all emulation, analysis and the explanation that the present invention did, and the numbering of the precoding vectors in the code book is shown in the table content of vector top:

0	1
		0.356951624498497+0.087021253122628i 0.087538247968263+0.157842790148989i 0.464961899023787+0.003310516186638i 0.785006382746187+0i	-0.393640804251131+0.226679583108209i 0.391843572449198+0.335386198677016i -0.365548690067920+0.274081968806544i 0.564704547407226+0i
2	3
		0.078477545103364-0.293480305674212i -0.748797597782116+0.35426817874787i 0.274858149722221-0.279091431849834i 0.260898007615250+0i	-0.226952477440298+0.302495440405902i 0.045813840483885-0.159771933576918i -0.756129550925118-0.024227116679576i 0.506995317348923+0i
4	5
		0.016629383219082-0.548100260407838i 0.329918987649270+0.053568193785053i 0.593755741268673-0.212741728402888i 0.435647282861194+0i	0.062745512342009+0.28903524130746i -0.051072769902764+0.815841095860682i -0.410536827740416+0.025453682338864i 0.274095114087804+0i
6	7
		-0.680589371770339+0.122208496083638i -0.308379033726114+0.236137877996725i -0.061891702690689-0.23780305510512i 0.557336154194487+0i	0.702899821781835-0.21213319868808i -0.353011734553576-0.142865131733656i -0.335861517352320+0.300679480971262i 0.335697046219173+0i
8	9

-0.457390837755998+0.55116645731328i 0.021380119536013-0.279580227893189i 0.162807090376393-0.335416964056339i 0.519014697360117+0i	0.149563267442602-0.346171404703475i 0.209012658651896+0.189430403807373i -0.482325266216683+0.566653853689253i 0.473805620378527+0i
		10	11
0.210480050619146+0.414360979093343i -0.499094844549650+0.222532973365597i 0.470349215239227-0.483670307957973i 0.173842423271414+0i	-0.258660106307685-0.008496869979997i -0.692865418484841+0.079069893051379i -0.072569706565812+0.621267010174366i 0.235518908463983+0i
		12	13
0.592015373254703+0.582355760172544i 0.137019118275859-0.143269960836841i 0.292202723735543-0.244861887726547i 0.354597335231372+0i	-0.256613271153266-0.091773159204282i 0.444582372069229-0.075705941773748i 0.117910323634874+0.117736149668846i 0.833413340296762+0i
		14	15
0.779451639250902-0.27838255497303i 0.029228998147820+0.410981176917134i 0.028440861125743+0.010322193764359i 0.379846025090652+0i	-0.365866268109414+0.500489303630263i -0.591561695325715-0.137529791722979i -0.058558302195821+0.096041249531479i 0.483879790294821+0i
		16	17
0.198785135059516-0.058438557326465i 0.098174556352726-0.446556612228481i 0.344698349054737-0.473674291371931i 0.636265720834603+0i	0.169038697576193+0.019359745330828i 0.366757380072909-0.367406471855126i 0.401393703959202+0.591479400329905i 0.436563673466750+0i
		18	19
-0.273005656043511-0.240724221834976i 0.156095048882922+0.379725386314942i 0.092760706513432-0.465209026582785i 0.688432088448403+0i	0.255643589375425+0.25617698318559i -0.654447998902842-0.458557853996416i -0.208827387136597+0.196628812333964i 0.384929152324533+0i
		20	21
-0.175582147145863+0.144707451932447i -0.484354552481520-0.483192765015156i -0.409130940680855-0.51582615400427i 0.216081777364644+0i	0.448722246314840-0.372022311830466i 0.382031070878501-0.242298080725016i 0.078279327339982+0.174224175560373i 0.647387001479322+0i
		22	23
0.049798100221768+0.45924093946434i 0.174895890779308+0.287942212081821i 0.040594128577570-0.514501244811295i 0.637776766930883+0i	-0.181371423473449-0.573540928709123i -0.188723792573650+0.08380375101276i 0.226471926851179+0.149795235860783i 0.722348478877908+0i
		24	25

0.364829964775585+0.19150525478417i -0.008250428063829-0.191266279743798i -0.506689375673734-0.666596155526833i 0.304120727471565+0i	-0.453357286673871-0.402026115053686i 0.411688167268537-0.453012316602812i 0.343929096827416+0.200287784083603i 0.315804444671273+0i
		26	27
0.232880390136569-0.155421457730254i 0.264866801115886+0.284139463489054i -0.328403962010150-0.122473753164011i 0.804905121640799+0i	-0.354572014701710+0.389177388602744i -0.003322736245235+0.231567165882527i 0.242004033236088+0.343349482839371i 0.701947600773093+0i
		28	29
-0.084395681191154-0.573279917610033i -0.667889547678047-0.150590354339682i -0.333686085724523-0.137468999090408i 0.255400612423906+0i	-0.128044176520414+0.471261964994374i 0.342698802460669-0.639191367347149i 0.430437688271587+0.0567095957038i 0.216832179761858+0i
		30	31
-0.072478278975765-0.38836384646231i 0.848118516524330+0.096531142087918i -0.128613092605241-0.186969142111614i 0.252583361847224+0i	0.057141581238298+0.179258048448113i -0.341078752348845+0.610202639065212i 0.239717042694033-0.033363578105601i 0.646020144292873+0i
		32	33
-0.171505335254686-0.134757917562604i -0.388895473216825+0.198405977364231i -0.432805853749264+0.161175034947204i 0.740623591145402+0i	0.577181639701887-0.480167049799375i -0.170021239188678-0.381086665863719i 0.461636056260068+0.064602745120702i 0.211861575768583+0i
		34	35
-0.830770266184756+0.172983099955473i 0.380415651704306-0.113436574360985i -0.240844188993775-0.139336461672781i 0.211879953193259+0i	0.239806463023271-0.198372401614427i -0.384336890258112+0.23468693316285i 0.773905095579232+0.235209328758199i 0.214699612158360+0i
		36	37
0.356770849229954+0.553478205199716i 0.092786046491057+0.175345642735536i -0.291929432685644+0.180521007975391i 0.639695603134996+0i	-0.101623100881888-0.19590127478446i -0.352349776957874-0.70323613976498i 0.158637155485356+0.003918420427685i 0.554457303308403+0i
		38	39
0.141933765309632+0.150677408944564i 0.679096291662266-0.04082554856478i -0.603919404264782+0.010701685494794i 0.359832534679353+0i	-0.565179977062548+0.340497252396964i 0.387712462008401+0.520258704253664i 0.163337614239901-0.209632218032129i 0.270218983468458+0i
		40	41

-0.076661489911072-0.442008718045616i 0.026065211825916+0.715873570181332i -0.036829806572261+0.215285245324433i 0.487742528264697+0i	-0.074654379543847+0.191302256058694i -0.149793970111646-0.188824263538624i -0.110780325568535-0.180710840365141i 0.924558622316897+0i
		42	43
-0.629775675001484-0.514079974368504i 0.000607037287624+0.018292730862026i -0.107798265316786+0.456756100718282i 0.344271382900709+0i	0.735011225323959+0.281521711188846i 0.488654688984417+0.297928392967882i -0.100544817488804-0.17697596619727i 0.107375692961120+0i
		44	45
-0.185513532879718+0.269163746978718i 0.149664323243531+0.152827688388859i 0.263958467753102+0.871054286622889i 0.137732536090646+0i	0.443058265048865-0.285279938515542i -0.389080403666089-0.038989156485028i 0.099975020782261-0.210203445281907i 0.717795599334016+0i
		46	47
-0.410591664888992-0.011686224336499i 0.134112239909072-0.447990746441809i -0.283862524396876+0.478437777002363i 0.550559239204643+0i	0.386241903875835-0.22423342391646i 0.386264836612171+0.133097048839162i 0.101033827292290-0.690263953551393i 0.383339347115087+0i
		48	49
0.040204760299369+0.720677724417516i -0.125018218749566+0.325210527697812i -0.057083889171037+0.576427201892237i 0.148623224795631+0i	-0.150909618206174-0.077941771926269i -0.361585454565060+0.138211290641578i -0.174195917272322-0.758759089934615i 0.463945461617288+0i
		50	51
0.186037591658573-0.034259861330377i -0.192806043199926-0.208562835801435i -0.037259583122348+0.542496202925689i 0.766715881468691+0i	-0.201188419138141+0.148127042281698i 0.531882163455516-0.384658233323257i -0.146157404458416-0.516555506190961i 0.467471313804239+0i
		52	53
0.323635364458280+0.027615654264899i -0.072751957246294+0.458121425331828i 0.041316847738780+0.620724875720926i 0.540669016713939+0i	0.578724934885432-0.322482909727906i 0.184565521363491-0.025953175095286i -0.032138138619195+0.723923080786462i -0.035309161025197+-0i
		54	55
-0.268616297407505-0.419234687217999i -0.477930105825920-0.252448706975998i 0.358909378953723+0.488565081164877i 0.304020139558371+0i	0.295294083242106+0.393657162774235i 0.311422730547897-0.504100626651494i -0.083036569044721+0.062962104331736i 0.629185652511092+0i
		56	57

-0.362511326434096-0.060875223704766i 0.294873758731290+0.273937649399616i 0.698666982434460+0.18002202195594i 0.427017441407025+0i	0.418488279723962+0.267481861798854i -0.516535233257670+0.151993667423685i -0.271085559689180-0.327359855290397i 0.531750350898891+0i
		58	59
-0.212611632435715+0.071517425941793i -0.255921518813918-0.14058435517616i 0.647511353545195-0.090322820975941i 0.661054159557580+0i	0.243047968835183-0.34562457662559i 0.041659489454298-0.430931057629066i -0.487221916898723-0.0868728463902i 0.623780538042166+0i
		60	61
0.197488858119452+0.217163988928689i 0.767053752307653+0.212160612074468i 0.305520373049332+0.017726045058834i 0.432200714442446+0i	-0.085224534478317-0.632441952077555i 0.023195573343403+0.309113061372416i -0.458777954437545-0.39238178043336i 0.363626681567204+0i
		62	63
0.259926879091315+0.54767982311008i -0.286684701719544-0.253104836931113i 0.330304609170848+0.350160955758209i 0.504500567322775+0i	-0.432452335626408-0.496846053976878i 0.022699616845970-0.346693920599429i -0.171558792957541-0.275236294256694i 0.583292029566757+0i

(4) singular value decomposition of mimo channel matrix

In real system, this process of the present invention is by channel condition information acquiring unit (CSIU), and channel variation tracking cell (CTU) is finished.The mimo channel matrix of k OFDM subchannel correspondence is carried out singular value decomposition can be expressed as:

$H\left(k\right)=U\left(k\right)\mathrm{\Λ}\left(k\right)V^H\left(k\right)=[u_1\left(k\right),u_2\left(k\right),...,u_{M_r}\left(k\right)]\mathrm{\Λ}{[v_1\left(k\right),v_2\left(k\right),...,v_{M_t}\left(k\right)]}^H,$ Wherein first diagonal entry of matrix Λ is exactly the singular value of mimo channel matrix maximum.Utilize the Changing Pattern of the maximum singular value place curve of MIMO subchannel matrix to carry out the search of precoding codebook and the structure of sub-codebook is a core of the present invention.Shown in Figure 4 is the situation of change figure that adopts the maximum singular value place curve of MIMO subchannel matrix under the situation of Rayleigh channel model.Simultaneously, provide the code book sequence number form of the precoding vectors correspondence of searching for code book fully and obtained here: [11 11 11 11 11 11 11 11 11 11 23 23 23 23 23 2,525 25 25 25 25 25 25 25 25 25 25 25 25 63 63 6,363 63 63 13 13 13 13 13 13 13 13 13 13 13 13 1,313 13 13 13 50 50 50 50 50 50 50 50 50 50 50 50] according to maximum signal noise ratio principle.Contrast code book sequence number form and Fig. 4 can find, the variation of code book sequence number often occur in the curve limit near.Shown in Figure 5 is the situation of change figure that adopts the maximum singular value place curve of MIMO subchannel matrix under the situation of 3GPP space channel model.Simultaneously, provide the code book sequence number form of the precoding vectors correspondence of searching for code book fully and obtained here: [62 2222 262 62 62 62 62 62 62 62 62 62 62 62 62 27 27 2,727 62 62 62 62 62 62 222 62 62 62 62 62 62 6,262 62 62 62 62 62 62 62 2222222 35 35 3,535 35 35 62 62 62 62] according to maximum signal noise ratio principle.Equally, contrast code book sequence number form and Fig. 5 can find, the variation of code book sequence number often occur in the curve limit near.

The generation of (5) search of precoding codebook, subchannel grouping and precoding sub-codebook

The search of code book can be as required a certain according in the criterions such as snr of received signal maximal criterion, maximum-likelihood criterion, minimum singular value criterion, minimum mean square error criterion, channel capacity maximal criterion.The present invention will describe the codebook search process according to the snr of received signal maximal criterion.Here at first simply introduce maximum-likelihood criterion, minimum singular value criterion, minimum mean square error criterion, channel capacity maximal criterion.But the introduction of these several criterions is list of references also: Love, D.J., Heath, R.W., Jr., " Limited feedback unitary precoding for spatial multiplexing systems, " IEEETrans.Info.Theo.Vol 51 (8), Aug.2005 Page (s): 2967-2976.

1. maximum-likelihood criterion

When system used maximum likelihood receiver, receiving terminal judgement output to received signal can be expressed as: $\hat{S}k=\underset{s\&Element;\mathrm{\&psi;}}{\arg \min }{\left|\right|r_k-H{w}_{i}s\left|\right|}_2^2.$ The upper bound of the error sign ratio that maximum likelihood receives is a minimum euclidean distance between constellation $d_{\min ,R}=\underset{s_{}}{\mathrm{<figure-callout\; id="1"\; label="min\; s"\; filenames="A20071003962300241.png"\; state="\{\{state\}\}">min</figure-callout>}}{\left|\right|{\mathrm{Hw}}_i(s_1-s_2)\left|\right|}_2$ Function.Then the maximum-likelihood criterion of codebook search is: $w_{\mathrm{opt}}=\underset{w_i\&Element;W}{\arg \max }{d}_{\min ,R}.$ In the above-mentioned formula, ψ represents the modulation constellation set; r _kRepresent received signal; The symbol of s representative emission;

Represent the symbol of receiving terminal judgement output; w _iRepresent codebook vectors.

2. minimum singular value criterion

The corresponding linear receiver of this criterion.The ZF receiver is a kind of of linear receiver, and the lower limit of the minimum signal to noise ratio that ZF receives can be expressed as: ${\mathrm{SNR}}_{\min }\&GreaterEqual;{\mathrm{\&lambda;}}_{\mathrm{<figure-callout\; id="2"\; label="min"\; filenames="A20071003962300271.png,A20071003962300272.png"\; state="\{\{state\}\}">min</figure-callout>}}^2\frac{{\mathrm{\&epsiv;}}_s}{N_0},$ λ wherein _MinBe Hw ₁Minimum singular value.Then the minimum singular value criterion of codebook search is: $w_{\mathrm{opt}}=\underset{w_{}}{\mathrm{<figure-callout\; id="1"\; label="arg\; max\; w"\; filenames="A20071003962300241.png"\; state="\{\{state\}\}">arg</figure-callout>}\max }{\mathrm{\&lambda;}}_{\min }.$ Above-mentioned

It is the signal to noise ratio that transmits.

3. minimum mean square error criterion

The same corresponding linear receiver of this criterion.The least mean-square error receiver is the another kind of form of linear receiver, and the mean square error of received signal can be expressed as: $\stackrel{\&OverBar;}{\mathrm{MSE}}={(1+w_i^H{H}^H{\mathrm{Hw}}_i)}^{-1}.$ Then the minimum mean square error criterion of codebook search is: $w_{\mathrm{opt}}=\underset{w_i\&Element;W}{\arg \min }\stackrel{\&OverBar;}{\mathrm{MSE}}.$

4. channel capacity maximal criterion

According to the shannon capacity formula, the mimo channel capacity is: $C={\mathrm{<figure-callout\; id="2"\; label="log"\; filenames="A20071003962300271.png,A20071003962300272.png"\; state="\{\{state\}\}">log</figure-callout>}}_2\det (I+\frac{w_i^H{H}^H{\mathrm{Hw}}_i}{N_0}).$

Then the channel capacity maximal criterion of codebook search is: $w_{\mathrm{opt}}=\underset{w_i\&Element;W}{\arg \max C}.$ Above-mentioned N ₀Represent noise variance.

In real system, this process of the present invention is finished by the codebook search unit that comprises complete code book search unit (CBSU) and sub-codebook search unit (SCBSU).The present invention adopts the above-mentioned code book that contains 64 precoding vectors, based on maximum signal noise ratio principle codebook search is described here.Complete code book can be expressed as W=[w ₁, w ₂..., w ₆₄], then after transmitting terminal carried out precoding, the received signal of a certain antenna of receiving terminal can be expressed as r (k)=w _kH (k) s (k)+n (k), wherein H (k) is the mimo channel matrix of k OFDM subchannel, and s (k) is for sending signal, and n (k) is an additive white Gaussian noise.According to this received signal, the expression formula that can obtain received signal to noise ratio is $\mathrm{\&gamma;}\left(k\right)={\left|w_{k}H\left(k\right)\right|}^2\frac{{\mathrm{\&epsiv;}}_s}{N_0},$ ε wherein _sFor sending the average energy of signal, N ₀Variance for additive white Gaussian noise.In order to make the signal to noise ratio maximum of received signal, the maximum signal noise ratio principle of codebook search can be expressed as $w_{\mathrm{opt}}={\arg \underset{w_k\&Element;W}{\max }\left|w_{k}H\left(k\right)\right|}^2,$ Be w _OptFor making the codebook vectors of snr of received signal maximum in the code book.

Among the present invention, for the pairing OFDM subchannel of the limit in the singular value of all MIMO subchannel matrixes, the optimum precoding codebook vector of search in complete code book, promptly for the code book that contains 64 precoding vectors, the bit number that the subchannel of each limit correspondence need feed back is 6.Afterwards, with subchannel grouping, every group of subchannel with the limit correspondence be as initial, ends at the subchannel before the next limit.To the search procedure of the precoding codebook vector of a groups of subchannels as shown in Figure 3.In order to reduce number of bits of feedback, adopt the mode of sub-codebook structure and search for the corresponding subchannel of non-limit.If the complete codebook vectors of trying to achieve according to maximum signal noise ratio principle for the pairing subchannel of a certain limit is w _iIf wish to make corresponding subchannels of all the other non-limits in this groups of subchannels to feed back the precoding information of 1 bit, then sub-codebook is the code book that contains two codebook vectors.Here describe apart from the structure of the shortest criterion based on string sub-codebook.For example, for the adjacent subchannel of the corresponding subchannel of limit, its sub-codebook structure is with w _iFor core is searched for whole code book, seek and to make the string distance $d(w_i,w_j)=\sqrt{1-{\left|w_i^H{w}_j\right|}^2}$ The shortest vector w _j, w like this _iAnd w _jJust constituted a sub-codebook together.The rest may be inferred, is core with the precoding codebook vector of last sub-channel, searches for whole code book and find apart from the core string apart from the shortest vectorial structure sub-codebook, all obtains sub-codebook up to all subchannels.If wish to make corresponding subchannels of all the other non-limits in the groups of subchannels to feed back the precoding information of 2 bits, then sub-codebook is the code book that contains 4 codebook vectors.Constituted mode still can be according to the shortest string apart from theorem, but selected codebook vectors is to core vector string apart from three the shortest vectors relatively in the whole code book.

In addition, for changing mild relatively channel, very effective based on the subchannel group technology of complete codebook search at frequency domain.Concrete grammar is: at first, all subchannels are searched for whole code book according to certain criterion (as snr of received signal maximal criterion, maximum-likelihood criterion, minimum singular value criterion, minimum mean square error criterion, channel capacity maximal criterion etc.), obtain the precoding codebook vector of each subchannel; Secondly, determine the number M of different codebook vectors in the same grouping, this numerical value M has influence on systematic function and feedback overhead; Once more, with first subchannel m ₀The precoding codebook vector be the center, equally can be by smallest chord apart from the whole code book that contains 64 precoding vectors of criterion search, find to comprise center vector and core vector string M codebook vectors apart from minimum.And from first subchannel, put in order by subchannel, the codebook vectors of each subchannel and M the codebook vectors that obtains are compared, if the codebook vectors of subchannel belongs in the M collection, then this subchannel belongs to same grouping, up to finding subchannel m ₁Codebook vectors do not belong to till the M.So far Yi Qian all subchannels belong to first grouping.Again with subchannel m ₁Codebook vectors be the center, construct a M new codebook vectors by smallest chord apart from criterion, use m ₁After the codebook vectors of subchannel and the M collection relatively, if the codebook vectors of subchannel belongs in the M collection, then this subchannel belongs to same grouping, up to finding subchannel m ₂Codebook vectors do not belong to till the M, thereby obtain second grouping, so repeatedly, till grouping is finished to all subchannels.At last, during feedback, can adopt the mode of differential position to form feedback information, i.e. each grouping only needs first subchannel (m in this group of feedback ₀, m ₁, m ₂...) codebook vectors and should the group in the subchannel number.The size of M can be determined according to system requirements.In addition, also can carry out the structure and the search of sub-codebook to each groups of subchannels all the other subchannels except that first subchannel.

Calculus of finite differences formed feedback information in use location is made up of some two-dimentional vectors.For example, when M gets 1, to all subchannels be: [5 5555555 50 50 50 54 54 54 54 18 18 18 18 1,818 18 18 18 26 55555555 17 52 52 52 25 25 2,525 25 25 25 25 25 25 25 55555555555 55 55 5] according to the codebook vectors sequence number that the maximum signal noise ratio principle search obtains.The subchannel grouping situation that obtains according to above-mentioned packet mode is: 0～7,8～10,11～14,15～23,24,25～32,33,34～36,37～47,48～63, and totally 10 groups.Feed back the codebook vectors sequence number of every group of subchannel correspondence and the two-dimensional vector of the contained subchannel number composition of groups of subchannels and just can form feedback information: [(5,8), (50,3), (54,4), (18,9), (26,1), (5,8), (17,1), (52,3), (25,11), (5,16)], the search situation of the current precoding vectors code book of reflection that this information can be unique.If codebook vectors sequence number and differential position information all adopt 6 bits of encoded, then total bit number of internal feedback information sometime is about 120.

For the formation of sub-codebook structure and search method feedback information with use and will be below one save and be elaborated.

(6) formation of the search of sub-codebook, feedback information and transmitting terminal are to be numbered according to certain rule the codebook vectors in the sub-codebook to the prerequisite of the use sub-codebook search of feedback information.Coding rule is flexibly, and the present invention does not do special qualification, only requires that this coding rule is received end and transmitting terminal is observed simultaneously.The sub-codebook search procedure is identical with the process of the whole code book of search, and according to identical criterion (as snr of received signal maximal criterion, maximum-likelihood criterion, minimum singular value criterion, minimum mean square error criterion, channel capacity maximal criterion etc.).After all subchannels all obtain corresponding codebook vectors or sub-codebook vector sequence number, will form feedback data stream, with a groups of subchannels that contains 9 subchannels is example: first subchannel of establishing groups of subchannels, be the subchannel of limit correspondence, the complete codebook vectors sequence number of searching for complete code book acquisition is No. 60.Remaining 8 subchannel, the subchannel of promptly non-limit correspondence, the sub-codebook vector sequence number that the sub-codebook (establishing sub-codebook generates with 1 bit) that the corresponding above-mentioned sub-codebook building method of foundation of search constructs obtains is respectively: No. 1, No. 1, No. 1, No. 1, No. 1, No. 0, No. 0, No. 0, No. 0.Groups of subchannels hereto then, feedback information is exactly [60,1,1,1,1,1,0,0,0,0].In real system, this process is finished by feedback information synthesis unit (FBIU).

After transmitting terminal (feedback information processing unit (FBIU) and precoding vectors extraction unit (PCVU)) is received this feedback information, at first extract codebook vectors sequence number 60, i.e. the codebook vectors sequence number of the corresponding subchannel of limit.According to this sequence number, transmitting terminal can extract 60 these vectors of number from complete code book.What subsequently, transmitting terminal extracted will be sub-codebook vector sequence number 1,1,1,1,1,0,0,0,0, before foundation sub-codebook vector sequence number was extracted the sub-codebook vector, transmitting terminal at first will be used the sub-codebook building method of introducing previously, for the subchannel of non-limit correspondence is constructed corresponding sub-codebook, and use identical rule that the vector in the sub-codebook is numbered, according to the sub-codebook vector sequence number that from feedback information, extracts, from the sub-codebook of correspondence, extract the sub-codebook vector then.

(7) embodiment

Embodiment 1

Present embodiment is based on above-mentioned multipath Rayleigh channel model.Suppose that at first channel status is quasi-static, promptly channel status is constant in the transmission course of a packet.The data that present case is used comprise 1920 data bits, generate the packet that contains 960 symbols through sign map and QPSK modulation.Suppose to have obtained channel condition information, then feed back generation unit and finish processes such as singular value decomposition, limit search, codebook search, subchannel grouping, sub-codebook generation, sub-codebook search, formation precoding codebook sequence number feedback information bits according to channel condition information at receiving terminal.Present embodiment uses 1 bit to generate sub-codebook, and promptly each sub-codebook contains 2 codebook vectors.Precoding codebook sequence number feedback information bits arrives transmitting terminal through feedback channel.The signal of transmitting terminal is modulated through OFDM, and forms the signal that 4 tunnel preparations are loaded into 4 transmit antennas.The precoding functional unit is selected the precoding codebook vector according to precoding codebook sequence number feedback bits information from code book, 4 road signals to be transmitted are carried out precoding.After the precoding, signal is loaded into the emission of 4 transmit antennas, through multipath Rayleigh channel, is received by two reception antennas at receiving terminal.The received signal of two reception antennas is carried out the OFDM demodulation respectively.Receiving terminal extracts precoding vectors according to precoding codebook sequence number feedback bits information equally from code book, the restituted signal weighting is merged.Combined signal is finally deciphered the acquisition data symbol according to maximum-likelihood criterion, obtains data bit through the QPSK demodulation.

Bit error rate performance simulation curve and number of bits of feedback correlation curve shown in Figure 7 under the multipath Rayleigh channel model shown in Figure 6 show, the present invention has obtained and has used the essentially identical bit error rate performance of subspace searching algorithm of 2 bits generation sub-codebook under the situation of number of bits of feedback minimizing about 43; Reduce about 295 in number of bits of feedback, under 4 times the situation, bit error rate performance only has the loss of 0.5-2.5dB with respect to the situation of searching for code book fully to the greatest extent.

Embodiment 2

Present embodiment is based on above-mentioned 3GPP space channel model.This channel model is a kind of channel model of rapid fading with respect to above-mentioned multipath Rayleigh channel model.So present embodiment can be verified the performance of the present invention under the fast fading channel condition.The concrete implementation process of present embodiment is identical with embodiment 1.Bit error rate performance curve and number of bits of feedback correlation curve shown in Figure 9 under the 3GPP space channel model shown in Figure 8 show, under 3GPP space channel model condition, the present invention has obtained slightly to be better than the bit error rate performance that uses 2 bits to generate the subspace searching algorithm of sub-codebook under the situation of number of bits of feedback minimizing about 32; Reduce 281 in number of bits of feedback, under 4 times the situation, bit error rate performance only has the loss of 0.5-2dB with respect to the situation of searching for code book fully to the greatest extent.In addition, from number of bits of feedback correlation curve shown in Figure 9, can see that two significantly fluctuate, this is variation more violent the causing relatively of 3GPP space channel model, this shows that also algorithm of the present invention can better track channel change, is a kind of method that reduces precoding feedback information bits number more flexibly.

(8) adaptability of the present invention

Above-mentionedly change the different embodiment of severe degree at two kinds and show that algorithm of the present invention has certain adaptability to different channels.This adaptability is mainly reflected on the wave characteristic of instantaneous feedback bit number.The trend of fluctuation is that when channel variation was violent, the feedback information bits number can increase thereupon; When channel variation was steady, the feedback information bits number can decrease or held stationary.This adaptability proves that also algorithm of the present invention can better be followed the tracks of the variation of channel, is a kind of consideration channel variation, reduces the method for feedback information bits number.

Claims (13)

1, a kind of MIMO-OFDM system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that, may further comprise the steps:

Step 1 is according to the maximum singular value of channel condition information for the corresponding mimo channel matrix of each OFDM subchannel extraction;

Step 2 according to the order of OFDM subchannel, is considered as point on the smooth curve with these maximum singular values, seeks the limit in these singular values;

Step 3 is searched for complete code book for the pairing subchannel of limit, obtains corresponding complete code book precoding vectors sequence number;

Step 4 for the pairing subchannel of non-limit, is divided into several groups in proper order by the OFDM subchannel, obtains the sub-codebook sequence number of precoding codebook vector by every group of corresponding subchannel of non-limit with the method for sub-codebook structure and search;

Step 5 feeds back to transmitting terminal with the series of codebook vector serial number information that is obtained, and transmitting terminal utilizes this information extraction codebook vectors, finishes the emission precoding.

2, MIMO-OFDM as claimed in claim 1 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that, the maximum singular value method of the mimo channel matrix of each OFDM subchannel correspondence of the extraction described in the step 1 is that MIMO subchannel matrix is carried out singular value decomposition.

3, MIMO-OFDM as claimed in claim 1 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that, the maximum singular value method of the mimo channel matrix of each OFDM subchannel correspondence of the extraction described in the step 1 is to grip the eigenvalue of maximum of transposed matrix product altogether by asking for mimo channel matrix and mimo channel matrix.

4, MIMO-OFDM as claimed in claim 1 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that, limit described in the step 2, order according to the OFDM subchannel, the pairing singular value of first subchannel is an extreme point, and the singular value of last subchannel correspondence is not as extreme point.

5, MIMO-OFDM as claimed in claim 1 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that, grouping described in the step 4 is to be divided into some groups according to pole location, and every group initial with the corresponding subchannel of limit, ends at the preceding subchannel of next limit; Every group of precoding codebook vector with the corresponding subchannel of limit is that initial center vector is implemented sub-codebook structure and search.

6, MIMO-OFDM as claimed in claim 5 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that described sub-codebook structure and search comprise:

1. step determines the bit number that the corresponding subchannel of non-limit will feed back.Determine number of bits of feedback, just determined the size of sub-codebook;

Step 2., the structure of sub-codebook is that the codebook vectors that is obtained with last sub-channel is a core, searches for the code book of whole precoding vectors according to smallest chord apart from criterion, finds the codebook vectors that satisfies this criterion, then this vector is exactly a vector in the sub-codebook;

3. step is searched for the method for sub-codebook and is obtained precoding sub-codebook vector for the subchannel employing of non-limit correspondence, and record sub-codebook vector sequence number.

7, MIMO-OFDM as claimed in claim 6 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that, the search sub-codebook of step described in 3. will foundation and the corresponding subchannel code book of application and the limit identical criterion of criterion of searching for.

8, MIMO-OFDM as claimed in claim 1 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that, grouping described in the step 4 is for changing mild relatively channel at frequency domain, to adopt the subchannel group technology based on complete codebook search:

At first, all subchannels are searched for whole code book according to criterion as required, obtain the precoding codebook vector of each subchannel; Secondly, determine the number M of different codebook vectors in the same grouping, and be the center, search for whole code book, find to comprise that center vector satisfies M codebook vectors of this criterion by identical criterion with the precoding codebook vector of first subchannel; Once more, from first subchannel, put in order by subchannel, codebook vectors to each subchannel compares with M the codebook vectors that obtains, if the codebook vectors of subchannel belongs in the M collection, then this subchannel belongs to same grouping, and till the codebook vectors that finds subchannel m did not belong to M, so far Yi Qian all subchannels belonged to first grouping; Codebook vectors with subchannel m is the center again, constructs a M new codebook vectors by identical criterion, uses the codebook vectors of subchannel thereafter and M to compare, and obtains second grouping, so repeatedly, and till all subchannels groupings are finished; At last, during feedback, adopt the mode of differential position to form feedback information, or each groups of subchannels all the other subchannels except that first subchannel are carried out the structure and the search of sub-codebook.

9, MIMO-OFDM as claimed in claim 8 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that, described differential position mode is fed back, be meant: the quantity that each groups of subchannels is begun complete codebook vectors sequence number that subchannel obtains and the contained subchannel of this groups of subchannels is synthetic, and this composite signal is fed back to transmitting terminal; Transmitting terminal extracts every group of quantity information that begins complete codebook vectors sequence number of subchannel and the contained subchannel of this groups of subchannels from the composite signal of receiving; For in each groups of subchannels except that the subchannel of beginning the subchannel, do not feed back any information, begin the identical precoding codebook vector of subchannel and carry out precoding and be to use with every group.

10, MIMO-OFDM as claimed in claim 1 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that transmitting terminal described in the step 5 utilizes feedback information to extract codebook vectors from code book, finishes the emission precoding, comprising:

1. step for the subchannel of limit correspondence, directly utilizes the codebook vectors sequence number in the feedback information to extract codebook vectors from complete code book, carries out the transmitting terminal precoding;

2. step for the subchannel of non-limit correspondence, at first, adopt the mechanism structure sub-codebook identical with receiving terminal; Secondly, utilize the sub-codebook vector sequence number in the feedback information from sub-codebook, to extract codebook vectors, carry out the transmitting terminal precoding.

11, MIMO-OFDM as claimed in claim 10 system reduces the method for precoding feedback bits number based on codebook search, it is characterized in that, 2. step when receiving terminal adopts identical sub-codebook structure mechanism with transmitting terminal, also will adopt the method for numbering serial of identical sub-codebook vector.

12, reduce the receiving end device of precoding feedback bits counting method in a kind of MIMO-OFDM according to claim 1 system based on codebook search, it is characterized in that, comprising:

The channel condition information acquiring unit obtains channel condition information;

The channel status tracking cell, the channel condition information that obtains according to the channel status acquiring unit extracts the maximum singular value of corresponding mimo channel matrix for each OFDM subchannel, and the order of pressing the OFDM subchannel, described maximum singular value is considered as point on the smooth curve, finds out limit;

The full code search unit obtains the complete code book sequence number of precoding codebook vector of the subchannel of described limit correspondence;

The sub-codebook search unit for the subchannel of non-limit correspondence, is divided into several groups in proper order by the OFDM subchannel, obtains the precoding codebook vector sub-codebook sequence number of the subchannel of every group of non-limit correspondence with the method for sub-codebook structure and search;

The feedback information synthesis unit, described full code search unit and sub-codebook search unit is synthetic, and feed back.

13, reduce the transmitting terminal device of precoding feedback bits counting method in a kind of MIMO-OFDM according to claim 1 system based on codebook search, comprising:

The feedback information processing unit receives synthetic feedback information, and according to becoming sub-codebook with the employed identical method construct of receiving end device;

The precoding vectors extraction unit extracts complete code book sequence number, and obtains corresponding precoding vector in whole code book, extracts the sub-codebook sequence number, and obtain corresponding precoding vector in the sub-codebook of described structure.

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