CN101185275A - Method and apparatus for channel feedback - Google Patents

Abstract

A method for communicating channel estimates on a plurality of subcarriers between a transmitting device and a receiving device. The transmitting device determines a channel estimates on a plurality of subcarriers and then encodes the channel estimates into at least one encoded channel waveform. Then the transmitting device transmits the at least one encoded channel waveform to the receiving device.

Description

The method and apparatus that is used for channel feedback

Invention field

Present invention relates in general to communication system, and particularly, relate to a kind of method and apparatus, be used for providing channel information to transmitter in multiple-input and multiple-output (MIMO) transmission.

Background technology

Multiple-input and multiple-output (MIMO) is a kind of transmission method that relates to a plurality of transmitting antennas and a plurality of reception antennas, and it is expected to increase to a great extent the link capacity of wireless communication system.Multiple transmission policy requirement emission array has the knowledge to a certain degree about channel response between each transmit antenna element and each the reception antenna element, and is commonly called closed-loop MIMO.If carry out array calibration at the transmitter place, then by using the technology such as uplink sounding in the time division duplex (TDD), obtaining completely at the transmitter place, broad-band channel knowledge is possible.Yet when using repeater in the TDD system, perhaps when not carrying out array calibration at the transmitter place, the uplink sounding method can not be worked in Frequency Division Duplexing (FDD) (FDD) system.Therefore, have the demand to such effective ways, this method is not when being effective to this purpose, to provide channel knowledge completely at the transmitter place at uplink sounding.

The accompanying drawing summary

Fig. 1 is the time diagram that feeds back in the TDD system.

Fig. 2 is the time diagram that feeds back in the FDD system.

Fig. 3 shows an option that is used for effective feedback channel knowledge.

Fig. 4 shows second option that is used for effective feedback channel knowledge.

Fig. 5 is to use phase shift with the example of encoding channel information effectively.

Fig. 6 is the example of frequency orthogonal (orthogonal-in-frequency) coding of frequency domain channel information.

Fig. 7 is the example of the frequency orthogonal coding of time domain channel information.

Fig. 8 is the device that is used for transfer channel knowledge.

Fig. 9 is the device operational flowchart of Fig. 8.

Figure 10 is the device that is used to recover channel estimating.

Figure 11 is the device operational flowchart that Figure 10 is shown.

Embodiment

For the sake of simplicity, the present invention presents from following viewpoint, and when the closed loop transmission carried out to user terminal (SS), (BS) provides channel information to the base station.Should be understood that the present invention also is applicable to such situation, i.e. the effect of BS and SS and effect described herein are put upside down.For example, the present invention can be applied to such situation, and wherein, SS provides channel information, to allow the closed loop transmission from SS to BS.Therefore, will mainly concentrate on the situation of BS to the SS emission although describe, term " source communication unit " will refer to carry out the communication unit (for example, BS, SS or other transceivers) that carries out closed loop transmission to target communication unit.

And in present specification, some term can exchange use.Term " channel response ", " frequency-selective channel profile ", " spatial frequency channel response " all refer to the channel response information that the base station needs, and facilitate the use the closed loop transmission technology.This channel response information can also refer to channel knowledge.Term " waveform " and " signal " also can exchange use.Subscriber equipment or subscriber station (SS) refer to mobile device station (MS) or mobile device simply sometimes, and the present invention to be equally applicable to subscriber equipment be situation that fix or mobile device (that is, not fixing).Receiving equipment can be base station (BS), subscriber station (SS) or its any combination.Equally, transmitter can be BS, SS, MS or its any combination.In addition, if system has transponder, repeater or other similar devices, then receiving equipment or transmitter can be transponder, repeater or other similar devices.If BS is carrying out the closed loop transmission to this transponder/interrupter, then this transponder or repeater can be considered to be equal to SS.If repeater is being carried out the closed loop transmission to SS, then this transponder or repeater can be considered to be equal to BS.This repeater can be an one-way repeater, such as uplink relay device or downlink relay device.For example, the uplink relay device receives the uplink signal from SS, and to the BS repeating signal or by the information of this signal indication.Term " fast Fourier transform (FFT) " and " inverse fast fourier transform (IFFT) " refer to discrete Fourier transform (or similar conversion) or inverse discrete Fourier transform (or similar conversion) respectively.

Is crucial at transmitter or source communication unit place acquisition channel knowledge for the gain that obtains by this emission array technique guarantee, this emission array technology such as high specific transmission, emission space division multiple access (SDMA) and a plurality of outputs of a plurality of inputs of closed loop (MIMO) technology.Two kinds of methods that are used to obtain channel knowledge are feedback and channel detection.Channel detection is only just worked for time division duplex (TDD) system, and use such fact, be that up link and down link RF channel are reciprocal, thus the downlink channel knowledge that the uplink channel that BS can obtain free mobile device to carry out is surveyed.Be known that BS must calibrate its up link and down link array in order to make channel detection work.Different with channel detection, channel feedback will work in the TDD system of Frequency Division Duplexing (FDD) (FDD) system and no array calibration.

The present invention is a kind of method, be used for effectively feeding back multiplex (MUX) (a plurality of channel estimating of a plurality of subcarriers for example to BS from (one or more) mobile device, such as for the one or more antennas in the ofdm system), (if the effect exchange of BS and mobile device, described method also will be worked).Described method sends training (for example pilot frequency code element) by BS from its each transmitting antenna and works, make mobile device can measure (or estimation) complex channel response (channel estimating can also obtain according to the additive method that does not require training data, such as direct judgement channel estimating (decision-directed channel estimation) or blind Channel Estimation) to each BS antenna.Next, done the channel estimating (structure channel waveform) of each mobile device coding of (perhaps know/expect by some other means and do like this) like this by the BS scheduling to each BS antenna, and potential then a plurality of such mobile device is beamed back the channel estimating of coding simultaneously to BS, determines Downlink channel estimation with auxiliary BS.

Chnnel coding process at specific mobile device place of the present invention does not require that (for example traditional feedback transmission is used the conventional constellation such as QPSK to the degree that intrinsic precision reached that exceeds the mobile device receiver with channel quantitative, on code element, transmit binary information, and the channel estimating that the present invention can transmit non-quantification basically (for example, do not need these values are restricted to four values of QPSK constellation, but be subjected to the restriction that mobile device received and launched the intrinsic precision of handling certainly); On the contrary, (from the bandwidth aspect) with the number of some measured channel (for example effectively in the present invention, channel from each BS antenna to one or more mobile device antennas) be combined as single channel waveform, be used to be transferred to BS, this channel waveform can also be called as the encoding channel waveform.A plurality of mobile devices can on identical temporal frequency resource, be launched its encoding channel waveform in the SDMA mode.Then, BS uses its a plurality of reception antennas, is used to separate the encoding channel waveform from each mobile device, and determines channel estimating by removing coding then.Note, mobile device for a plurality of antennas, each antenna at mobile device place can be launched different encoding channel waveforms according to the MIMO mode, (for example, waveform is the coding of the channel of the mobile device antenna from whole BS antennas to launching code channel channel waveform).Certainly, in the SDMA mode, from the MIMO type transfers of the encoding channel waveform of a mobile device can with the transmission overlaid from the encoding channel of other mobile devices.By encoding channel effectively estimate and ul transmissions on use SDMA and/or MIMO, channel feedback can become unusual bandwidth efficient.The present invention is by optionally combination S DMA, MIMO, multiple source channel estimating, scrambling are fed back broad-band channel to avoid excessive peak-to-average power ratio and pilot design effectively at frequency domain (for example on a plurality of subcarriers at ofdm system) or time domain (for example by the time domain data code element being replaced with the sample of channel waveform).

Fig. 1 shows the example of the time diagram that the TDD of being used for communication system according to the present invention feeds back, and wherein channel information is being asked in the base station, (TxAA) transmits with the closed loop " emission adaptive array " (Transmit Adaptive Array) of carrying out some type.At first, BS is sending training data (for example, pilot frequency code element) near the end of down link, (in fact, this training can be at descending chain circuit frame Anywhere, if but send training in the end of descending chain circuit frame, then feed back the stand-by period to reduce).For BS with a plurality of transmitting antennas, this BS can carry out a plurality of transmission, such as second transmission on the transmission of first on first transmitting antenna and second transmitting antenna, and the rest may be inferred (a plurality of transmission), wherein these a plurality of transmission preferably include pilot frequency code element, and it allows SS to estimate channel to a plurality of subcarriers of the BS antenna of each emission.These a plurality of transmission can be simultaneously, preferably have quadrature in the antenna/separable pilot frequency sequence (for example, different antennae is used different set or a plurality of subcarrier), but perhaps can separate preferably close in time.Then, each mobile device channel information of being asked by BS, estimation to the channel of each BS transmitting antenna (for example, by determining a plurality of channel estimating of a plurality of subcarriers), channel estimating is encoded to encoding channel waveform (producing or make up channel waveform), and by during up link, sending (emission) this encoding channel waveform, transmit channel knowledge then to the base station.In one embodiment, channel estimating is encoded, in a symbol time, send with the channel estimating of permission from a plurality of BS antennas and/or a plurality of SS reception antennas.Note, in one embodiment, channel estimating sends with the pilot frequency code element that is used at BS place estimating uplink channel, (uplink channel estimation is used by BS, estimates from the encoding channel of each mobile device to allow its uplink channel feedback that receives a plurality of mobile devices of separation and detection).Pilot frequency code element can form channel detection waveform (for example, the pilot frequency code element of OFDM set of subcarriers), is used to realize the purpose of the uplink channel estimation at BS place.BS uses the channel knowledge of feedback, so that (closed loop transmission preferably is on next very near downlink interval in carrying out closed loop transmission (for example TxAA) on the down link after this up link following, thus, making and measure and use channel variation minimum between this measurements, is in the big situation but the present invention also is applicable to delay).Because the channel knowledge of feedback not requirement turns to traditional symbol constellations and (for example, QPSK), therefore, than traditional scheme, can improve the resolution of channel knowledge and dynamic range (for example being non-quantification basically).Therefore, in one embodiment, the channel estimating that is fed is non-quantification basically.In other embodiments, channel estimating can be mapped to (for example, immediate predetermined complex values set) in the set of predetermined value, perhaps can clipped wave, if perhaps its value is lower than particular value, then can be set to 0.

Fig. 2 shows the example that is used for the time diagram that the FDD communication system feeds back, and wherein again, BS is asking channel information, to carry out closed loop (for example, TxAA) transmission.Class of operation is similar to TDD, but in FDD, measured channel and BS use the stand-by period between the estimation of down link upper signal channel can become far below TDD, and this is because be while communicating downlink and up link.For the sake of simplicity, the down link of feedback mechanism hypothesis FDD system uses the identical modulator approach (for example OFDM) with same band with up link.Yet the feedback mechanism that is proposed easily expands to the situation that up link and down link have different modulation and/or bandwidth.In addition, the present invention has predicted and used a plurality of transmission modes in up link, for example, mixing of IFDMA, CDMA, single carrier wave TDMA or these conventional uplink data transmission (any one in these patterns provides low peak-average ratio) and the OFDM/OFDMA (the frequency domain feedback of complex channel response is provided) that is used for feedback transmission.In this case, preferably utilize normal transfer of data, make this feedback transmission in the time or in frequency, carry out multiplexed.Therefore, the present invention can use with other transfer of data from target communication unit in the different modulator approach of modulator approach used, come the send channel waveform.

Notice that the feedback fraction of the uplink frame shown in Fig. 1 and Fig. 2 was made up of two OFDM symbol time cycles.First code-element period is to be used for each mobile device to send the pilot frequency code element (for example, the channel detection waveform) that is used to estimate channel, and second code-element period is used for the transmitting channel feedback, determines the channel estimating of a plurality of subcarriers with the auxiliary source communication unit.

Fig. 3 shows this feedback option, and Fig. 4 shows another feedback option, and it only requires an OFDM code element by hybrid pilot code element (for example, the channel detection waveform) and feedback.Mixing shown in Fig. 4 comprises frequency multiplex, but also can use the mixing of other types, and is multiplexed such as sign indicating number.Obviously, any mixing of pilot tone and channel waveform all is feasible, such as the sample that scatters (scattering) pilot frequency code element and channel waveform on a plurality of symbol times.In addition, pilot frequency code element can not utilize the explicit transmission of channel waveform, for example, and when source communication unit uses channel estimating from the normal data business to detect channel waveform from the target communication unit emission.

With respect to channel multiplexing (or reciprocity (reciprocity)) strategy, (that is, in TDD, mobile device is surveyed up link, and BS supposes the channel reciprocity between up link and the downlink channel) and other technology of the prior art, the advantage of the feedback method that is proposed is:

1. the feedback method that is proposed can be used for TDD and these two kinds of patterns of FDD.

Institute's proposition method in the complexity at mobile equipment unit place far below method based on code book and vector quantization.

3. in tdd mode, use the feedback method that is proposed not require the antenna calibration at BS or mobile device place.

4. the feedback method that is proposed will provide channel feedback mechanism in the TDD system, and it has the repeater (uplink channel is surveyed and will do not worked, and this is because mobile device is not directly launched to BS) on the up link.

5. during array calibration, the feedback method that is proposed can be very useful.For example, the feedback method that is proposed can be used for sending opposite channel from SS and BS.

In addition when the up link of BS and downlink antenna array not simultaneously, the feedback method that is proposed also can be worked.

7. if how the known BS of mobile device calculates its emission weighting, then mobile device can use broadcast pilot on the down link to determine compound channel (i.e. the efficient channel of being seen by mobile device, it is the combination of true (true) RF channel of emission weighted sum).This is that being used for calculating for the uplink channel detection because of the known BS of mobile device is not the channel of the emission weighting of " very ".

Below will provide the detailed description more of some aspect of feedback method that is proposed.Suppose that there is M in (down link and up link place are equal) at the BS place _bIndividual antenna, and following two kinds of situations will be used to discuss mobile device: and 1) wherein mobile device u only has single transmitting antenna and M _{M, u}Individual reception antenna, and 2) wherein mobile device u has M _{M, u}The individual antenna that transmits and receives.(notice that this feedback method is applicable to the transmitting antenna of any number at mobile device place.And this feedback method easily expands to the situation that the base station has the reception antenna and the transmitting antenna of different numbers).Suppose that the OFDM down link has k available subcarrier, then mobile device u on its reception antenna m for the received signal of subcarrier k (0≤k≤K-1), and symbol time b is provided by following:

$Y_{u,m}(k,b)=\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}{H}_{u,m,l}(k,b)X_l(k,b)+N_{u,m}(k,b)---\left(1\right)$

H wherein _{U, m, l}(k, b) be on k the subcarrier and on the symbol time b, the frequency domain channel of m reception antenna from BS (for example, source communication unit) antenna l to mobile device (for example, target communication unit) u, X _l(k b) is the training symbol of launching from l the antenna of BS, and N _{U, m}(k b) has power σ _u ²Additional noise.Notice that time mark b is used to point out the symbol time (wherein, be used for the purpose of channel estimating if desired more than an OFDM code element, then can have a plurality of b values) of pilot frequency code element.

Mobile device can move multi-source channel estimator (multi-sourcechannel estimator) on received signal, preferably to determine the channel estimating at time b place for two or more k values

(determining a plurality of channel estimating of a plurality of subcarriers).Notice that channel estimating is complex values (expression amplitude and phase place) typically.BS can estimate with the simple multi-antenna channel that allows the mobile device place from the pilot signal of its a plurality of antenna emission quadratures.Also can use other channel estimation methods (for example, the judgement is auxiliary, iteration or the like).Then, mobile device is encoded to channel information, to produce channel waveform based on one of method of the following stated.

Method 1: the time of frequency domain channel is gone up separable feedback

This feedback method has used linear phase shift/phase ramp (a.k.a.Steiner ' s phase shift), the measured channel (channel estimating) of being used to encode from a plurality of transmitting antennas, thus time domain channel is quadrature (that is, channel estimating be separable in time domain).Illustrated among Fig. 5 for the mobile device of single antenna and the M at place, base station _bThe example of the time-domain representation as a result of the frequency domain channel phase-shift coding of individual transmitting antenna.As can be seen, suitable phase shift makes the time domain channel of each base station transmit antennas take the different piece of time domain.For this feedback method, mobile device is to encoding from the channel estimating of each BS antenna, with by creating following uplink waveforms (promptly for mobile device u with single transmitting antenna, encoding channel waveform or channel waveform), transmit effectively, (note, time mark d is used to point out the time location of uplink feedback, after its time of origin mark b in certain time, wherein from BS emission pilot frequency code element, to allow the channel estimating at SS place):

$Z_u(k,d)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,u}}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}(k,b)S_{u,m,l}(k,d)---\left(2\right)$

Wherein, S _{U, m, l}(k d) is the coded sequence of the channel estimating of user u, and β _uBe that ratio is regulated (scale factor), be used to make Z _u(k, and average transmit power d) (all average between the frequency, and if applicable, average between All Time) be 1 (perhaps other desirable power levels).Importantly, have a single ratio for whole channel estimating of single mobile device and regulate, thereby kept relative power level between each channel estimating.If do not need ratio to regulate, then can be by setting β _u=1 eliminates it.Note, if M _bBe 2 or more, then BS has a plurality of antennas, and a plurality of channel estimating of determining a plurality of subcarriers can comprise: based on a plurality of transmission that are received from source communication unit (for example, each is from different antennas), determine a plurality of channel estimating of each subcarrier in a plurality of subcarriers.

An example of coded sequence is following signal, and it has incorporated two aspects into.First aspect is Steiner ' the s phase shift that allows channel separation in the time domain, and second aspect is a scramble sequence:

S _u，m，l(k，d)＝q _u(k，d)exp(-j2πk(m-1+(l-1)M _m，u)/α _u} (3)

Wherein, q _u(k, d) be any known/scrambling (scrambling) sequence (constant mould random sequence for example, such as BPSK code element) at random, and α _uBe translocation factor (for example, the α of user u _u=M _{M, u}M _b).Notice that using scramble sequence is an importance of the present invention, has prevented the uplink signal of being launched (that is Z, because make channel estimating multiply by scramble sequence _uExcessive peak-to-average power in (k, IFFT d)) is than (PAPR), particularly for some channel condition (for example, flat fading channel).

When mobile device u had a plurality of transmitting antenna, the feedback transmission of similar MIMO was feasible, and (for m the transmitting antenna at mobile device u place) encoding channel waveform is given:

$Z_{u,m}(k,d)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}(k,b)S_{u,m,l}(k,d)---\left(4\right)$

Wherein, β _uBe that ratio is regulated, be used to make Z _{U, m}(k, average transmit power d) (at whole mobile device antennas, all average between the frequency, and if applicable, average between All Time) are 1 (perhaps some other power level) arbitrarily.Coded sequence S _{U, m, l}(k d) is given:

S _u，m，l(k，d)＝q _u，m(k，d)exp{-j2πk(l-1)/α _u} (5)

Wherein, q _{U, m}(k, d) be any known/scramble sequence (constant mould random sequence for example, such as BPSK code element) at random, and α _uBe translocation factor (for example, the α of user u _u=M _b).

Notice that when using (2) or (4), the frequency domain channel on the subcarrier k is fed back on the subcarrier k.In the TDD system, this means that on the downside if subcarrier k is in, then Fan Kui channel will send on the short arc subcarrier.For fear of this problem, another aspect of the present invention relates to and interweaves between frequency or replace Z _u(k, d) or Z _{U, m}(k, order d) is with scrambling feedback between frequency effectively.Note, before applying phase shift, must be to encoding channel waveform Z _u(k, d) or Z _{U, m}(k, d) execution interweaves, and can not interweave to the channel estimating execution.If use a plurality of OFDM code elements on up link, to send feedback, so, particularly when different channels has different average powers (for example, for two channel estimating of on two OFDM code elements, launching (each has K a to be beamed back value), on each OFDM code element, should launch each channel estimating half (from K/2 value of each estimation), thus, total transmitting power is identical for each OFDM code element), except on frequency, interweaving, can be favourable also interweaving in time.

It shall yet further be noted that to change (2) and (4), to adapt to the situation that pilot tone is mixed with feedback, as shown in Figure 4.When down link bandwidth and/or modulator approach (for example, single carrier wave) when being different from up link, can also change these equatioies, with to chnnel coding.

Method 2: the frequency orthogonal feedback of frequency domain channel

In the method, the downlink channel of measurement separates in frequency domain, and therefore, they can the phase mutual interference.Fig. 6 shows the M for the BS place _bThe example of this coding method of the single reception antenna at individual transmitting antenna and mobile device place.As can be seen, on different sub carrier, send the frequency domain channel (for example, with the channel estimating mapping of specific antenna or be encoded to predetermined subcarrier set) of each antenna, and so can the phase mutual interference.In order to recover the channel estimating at whole subcarriers place, BS need carry out interpolation to this channel estimating.Fig. 6 can be revised as the situation (for example, being similar to Fig. 4) that pilot tone is mixed with feedback that adapts to.With equation form, the channel waveform behind the coding of this form coding frequency domain channel is given (wherein mobile device u only has a transmitting antenna):

$Z_u(k,d)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,u}}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}(k,b)q_u(k,d)\mathrm{\δ}\left({(k+1-(l-1)M_{m,u}-m)}_{M_{m,u}{M}_b}\right)---\left(6\right)$

Wherein, (n) _NBeing the n modulus N, if n equals 0 then δ (n) is 1, and is that δ (n) is 0 in other cases, q _u(k d) is any known scramble sequence (for example, constant mould random sequence is such as BPSK code element at random), and β _uBe that ratio is regulated, be used to make Z _u(k, and average transmit power d) (all average between the frequency, and if applicable, average between All Time) be 1 (perhaps some other desirable power level).As the situation of separability in time, q _u(k d) helps prevent big peak-to-average power ratio in the uplink signal of being launched.Equally, as the situation of separability in time, interweaving can be used for before transmission at frequency Z _u(k d) upward carries out scrambling to code signal.U has M when mobile device _{M, u}During individual transmitting antenna, the coding waveforms of mobile device transmitting antenna m is given:

$Z_{u,m}(k,d)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}(k,b)q_{u,m}(k,d)\mathrm{\δ}\left({(k+1-l)}_{M_b}\right)---\left(7\right)$

Wherein, q _{U, m}(k, d) be any known/scramble sequence (for example, constant mould random sequence is such as BPSK code element at random), and β _uBe that ratio is regulated, be used to make Z _{U, m}(k, average transmit power d) (at whole mobile device antennas, all average between the frequency, and if applicable, average between All Time) are 1 (perhaps some power level) arbitrarily.

Notice that for the sake of simplicity, equation 6 and 7 can be write as does not have explicit time mark, that is:

$Z_u\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,u}}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}\left(k\right)q_u\left(k\right)\mathrm{\δ}\left({(k+1-(l-1)M_{m,u}-m)}_{M_{m,u}{M}_b}\right)$

And

$Z_{u,m}\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}\left(k\right)q_{u,m}\left(k\right)\mathrm{\δ}\left({(k+1-l)}_{M_b}\right)$

Note, if M _bBe 2 or more, determine that then a plurality of channel estimating of a plurality of subcarriers can comprise: determine channel estimating corresponding to more than first subcarrier of source communication unit first transmission (for example, from first antenna); And the channel estimating of determining to transmit more than second subcarrier of (for example, from second antenna) corresponding to source communication unit second.

Method 2 can also be called as the separability (decimatedsubcarrier type of separability) that extracts the subcarrier type, this is because the effect of delta function is to place on some subcarrier zero, thereby for the subcarrier set of extracting, channel estimating is beamed back.Other channel estimating set (such as for 1 different values, or for different mobile devices) assignment can be given and be set to zero subcarrier (as shown in Figure 6).Method 1 can also be called as the separability of using the cyclic shift type, and this is because based on α _uEquation 5 in phase ramp in the time-domain representation of channel, introduced cyclic shift (as shown in Figure 5).

From the mathematical notation of method 1 and 2 as can be seen, method 1 and method 2 have all produced channel waveform based on a plurality of channel estimating.Because channel waveform comprises a plurality of channel estimating in their structure, therefore, can think that channel waveform comprises the combination of a plurality of channel estimating.Equally, q _{U, m}(k, d) and S _{U, m, l}(k d) is known sequences, and therefore, channel waveform can be regarded as comprising the channel estimating by the known array modulation.For example, preferably, q _{U, m}(k is that (for example, BPSK) sequence can be any known sequences still to binary system d).

After producing channel waveform, can launch it, so that transfer channel knowledge or auxiliary source communication unit are determined the channel estimating of a plurality of subcarriers.

Method 3: the feedback of quadrature on the frequency of time domain channel

The other method of feedback is at frequency domain or in time domain the time domain channel of estimating to be beamed back.The work of this method is substantially similar to the previously described method that is used to send the frequency domain channel of extraction, and difference is, frequency domain channel estimates to replace with that time domain channel is estimated or response.Therefore, Fig. 6 remains effectively, but the representative now of the channel among the figure is time domain channel.Another option has been shown among Fig. 7, wherein on continuous block of sub-carriers, has sent each time domain channel response of a transmitting antenna and mobile device antenna.With equation form, the continuous blocks version of feedback is expressed as (wherein mobile device u has single transmitting antenna):

$Z_u(n+(m-1)L+(l-1){\mathrm{LM}}_{m,u},d)={\mathrm{\β}}_u{\hat{h}}_{u,m,l}(n,b)q_u(k,d)---\left(8\right)$

For 0≤n≤L-1,1≤l≤M _b, 1≤m≤M _{M, u}

Wherein, L is the time domain channel length of hypothesis, q _u(k d) is any sequence (for example, constant mould random sequence is such as BPSK code element at random), and β _uBe that ratio is regulated, be used to make Z _u(k, and average transmit power d) (all average between the frequency, and if applicable, average between All Time) be 1 (perhaps some other desirable value).When mobile device u had a plurality of transmitting antenna, the coding waveforms of mobile device transmitting antenna m was given:

$Z_{u,m}(n+(l-1)L,d)={\mathrm{\β}}_u{\hat{h}}_{u,m,l}(n,b)q_{u,m}(k,d)---\left(9\right)$

For 0≤n≤L-1 and 1≤l≤M _b

Wherein, q _{U, m}(k d) is any sequence (for example, constant mould random sequence is such as BPSK code element at random), and β _uBe that ratio is regulated, be used to make Z _{U, m}(k, and average transmit power d) (all average between mobile device antenna, the whole frequency, and if applicable, average between All Time) be 1 (perhaps some other arbitrary value).

Notice that described whole encoding schemes not necessarily can limit the dynamic range of the channel that is encoded.In fact, the expectation channel has limited dynamic range, but in certain embodiments, mobile device will need encoding channel to be in to be suitable in the narrower dynamic range of its transmitter design and realization.Therefore, can further handle the encoding channel waveform, thereby consequential signal is suitable within the dynamic range of mobile device transmitter requires.Be used to guarantee that the multiple technologies that the encoding channel waveform is suitable in the dynamic range are feasible, such as (but being not limited to): the encoding channel waveform that surpasses some value or voltage is carried out slicing, the encoding channel waveform is mapped to some symbol constellations, and the coding waveforms that makes amplitude be lower than the sample place of threshold value makes zero.Equally, before generating synthetic feedback (channel) waveform, these processing methods can directly apply to channel estimating (for example, if

Be lower than threshold value, then it can be made zero, if its value is higher than threshold value, then it can clipped wave, and perhaps its amplitude and/or phase place may need to be quantized).The other method that can be used for controlling dynamic range or may improve performance in noisy condition be right

Value is carried out companding.At BS receiver place, the companding operation can be reversed alternatively, to recover some dynamic range.

Explain for the sake of simplicity, in preamble, from channel knowledge that the whole K of an ofdm system subcarrier is provided or some aspect of the present invention, extraction subclass aspect of an ofdm system K subcarrier.This situation can take place, and this is typically to allow at the MS place whole subcarriers to be estimated because of the pilot frequency code element from BS.But,, also can ask MS only to feed back the channel knowledge (for example, the selected subcarrier in selected subcarrier or the specific subcarrier scope) of sub-carrier subset even like this.In this case, the subcarrier that is used for surveying uplink channel and launching code channel waveform by MS does not need and is complementary by the subcarrier of BS request channel knowledge, as long as BS knows this feedback is corresponding to which subcarrier.In one example, (that is when, sub-band) channel knowledge was fed, above mentioned three kinds of methods that are used to produce the encoding channel waveform all can be used when the continuous piece of subcarrier.But in this example, third party's method (that is, the feedback of quadrature on the frequency of time domain channel) is preferably come the response of modeling sub-bands of frequencies by following time domain channel, that is, this time domain channel has the channel tap interval greater than complete bandwidth situation.In another example, when the channel knowledge that breaks away from the subcarrier set was fed, MS can be in the mode of subcarrier one by one, and each feedback is perhaps carried out simultaneously, as is similar to the transmission of MIMO corresponding to a channel of each BS antenna.

Can also there be some environment, wherein with low SNR or C/I environment received code channel waveform.In order to improve feedback quality, can carry out by (on time and/or frequency) and have the transmission that the mobile device of the encoding channel waveform of repetition carries out, to improve feedback quality.Replacedly, be different from and repeat whole encoding channel waveform, can before producing the encoding channel waveform, estimate by interactive channel.For example, the method for quadrature (Fig. 6) on frequency will be fed back " subcarrier M in hypothesis _bThe channel of last antenna 1 " the subcarrier place, " channel of the antenna 1 on the subcarrier 0 " can be sent once more.The balance that improves the quality on the subcarrier 0 is the extraction factor that increases in the frequency domain, and this is because subcarrier M _bOn channel will not be launched.Except these are used to improve the technology of feedback quality, by right at the SS place

Value is used contrary compandor (or expander) (restriction that preferably has the output value) and by put upside down the operation at BS place after receiving feedback, can be reduced The noise on the feedback channel.Input-output characteristic that can designed spreader is with some SNR of improving the inverse operation output of BS place or other quality metrics (for example, on frequency average SNR or MSE, handle the beam shaping that feeds back based on institute and gain or the like).

Note, in alternative embodiment of the present invention, can send other signals, rather than the channel estimating of aforementioned any feedback method

Notice that method 1 and 3 may be required in the signal that frequency domain is fed and has the time-domain representation of equal value that has the finite time span.For example, reciprocal channel (inverse channel) that can transmitting channel, so that auxiliary this array technique, such as array calibration.Another example is a tranmitting frequency SNR level optionally on each subcarrier, is used for using in the power loading technology at BS place.

Feedback when whole mobile devices have single transmitting antenna receives the decode

BS receives such signal, and this signal comprises channel waveform (Z), the channel with a plurality of channel estimating described above Waveform, wherein a plurality of channel estimating comprise: at least one channel estimating of each subcarrier in a plurality of subcarriers.Note, these a plurality of subcarriers need not be each subcarrier in the ofdm system, it can be the subclass of subcarrier, and such as the set of for example adjacent sub-carriers or the set of non-adjacent sub-carriers (for example subcarrier of Chou Quing), and the subcarrier set can be crossed over any part of channel width.BS is preferably based on the pilot signal that receives with channel waveform, the receive channel of estimating received signal, and, recover the estimation that these a plurality of letters are estimated based on the signal of this reception and the receive channel of this estimation.Below will provide more detailed example, wherein receive N by BS about some aspect of this point _uIndividual channel waveform.

N _uIndividual mobile device is launched their coded sequence simultaneously, and the M of the receive channel waveform at expression BS place _b* 1 received signal vector is given:

$R(k,d)=\underset{u=1}{\overset{N_u}{\mathrm{\Σ}}}{G}_u(k,d)Z_u(k,d)+N(k,d)---\left(10\right)$

G wherein _u(k d) is the M at and time d place last for the subcarrier k of mobile device u _b* 1 up link (reception) channel vector, and N (k is the Gaussian noise of adding d), and it has by σ _n ²I _MbThe covariance matrix that provides, (I wherein _nBe n * n unit matrix).

Estimation for the uplink waveforms of recovering each mobile device

BS can utilize the following MMSE combined weighted of mobile device u:

$w_u(k,d)={(\underset{l=1}{\overset{N_u}{\mathrm{\Σ}}}{\hat{G}}_l(k,d){\hat{G}}_l^H(k,d)+{\mathrm{\σ}}_n^2{I}_{M_b})}^{-1}{\hat{G}}_u(k,d)---\left(11\right)$

Wherein, Be up link (reception) channel estimating that sends the pilot frequency code element acquisition of (with receiving) from each mobile device according to handling, be used to estimate receive channel by BS.Note channel estimating

Normally plural, and can be called as the estimation complex channel gain.

The uplink waveforms of mobile device u is estimated to be given:

${\hat{Z}}_u(k,d)=w_u^H(k,d)R(k,d)---\left(12\right)$

Use this estimation and the coding strategy of mobile device u (promptly whether to send the estimation of frequency domain or time domain channel, and the time of whether having used go up the coding of quadrature on separable or the frequency, if BS points out that to MS which ad hoc approach is used to provide feedback in message, then BS will know this point), BS can obtain (recovery) channel estimating, this channel estimating be measure at each mobile device place and be used to produce channel waveform by the mobile device emission.Notice that the standard channel estimation procedure can be used in this step, to help to obtain gain to noise-plus-interference according to the channel of a plurality of BS antennas is encoded together.Now, BS has Downlink channel estimation, is used for carrying out TxAA operation (for total feedback stand-by period of t-b OFDM code element) at time t.

Feedback when whole mobile devices have a plurality of transmitting antenna receives the decode example

N _uIndividual mobile device is launched the coded sequence in their transmitting antennas simultaneously, and the M at expression BS place _b* 1 received signal vector is given:

$R(k,d)=\underset{u=1}{\overset{N_u}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,u}}{\mathrm{\Σ}}}{G}_{u,m}(k,d)Z_{u,m}(k,d)+N(k,d)---\left(13\right)$

G wherein _{U, m}(k d) is the M at and time d place last for the subcarrier k of m transmitting antenna of mobile device u _b* 1 uplink channel vector, and N (k is the Gaussian noise of adding d), and it has by σ _n ²I _MbThe covariance matrix that provides, (I wherein _nBe n * n unit matrix).

Estimation for the uplink waveforms of recovering each mobile device

BS can utilize the following MMSE combined weighted of the transmitting antenna m of mobile device u place:

$w_{u,m}(k,d)={(\underset{l=1}{\overset{N_u}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,l}}{\mathrm{\Σ}}}{\hat{G}}_{l,m}(k,d){\hat{G}}_{l,m}^H(k,d)+{\mathrm{\σ}}_n^2{I}_{M_b})}^{-1}{\hat{G}}_{u,m}(k,d)---\left(14\right)$

Wherein,

It is the uplink channel estimation that obtains since the pilot frequency code element of each mobile device transmission.

The uplink waveforms of m transmitting antenna of mobile device u is estimated to be given:

${\hat{Z}}_{u,m}(k,d)=w_{u,m}^H(k,d)R(k,d)---\left(15\right)$

Use this estimation and the coding strategy (promptly whether sent frequency domain or time domain channel and estimated, and the time of whether having used is gone up the coding of quadrature on separable or the frequency) of mobile device u, BS can obtain the channel estimating in each mobile device place measurement.Notice that the standard channel estimation procedure can be used in this step, to help to obtain gain to noise-plus-interference according to the channel of a plurality of BS antennas is encoded together.Now, BS has Downlink channel estimation, is used for carrying out TxAA operation (for total feedback stand-by period of t-b OFDM code element) at time t.

Receiving the decode of repeater place feedback

As described previously, the unit of receiving feedback signals unit can be repeater/transponder.In this case, the repeater operation/processing on institute's receive channel waveform basically with BS in identical.

Another aspect of the present invention is a method of communicating signals of supporting the efficient channel feedback method.The example of embodiment is an IEEE 802.16e/D5 preliminary specifications, wherein be provided with a kind of method, be used to allow subscriber station (SS) send channel on up link to survey waveform, estimate uplink channel responses between each SS antenna and each the BS antenna to allow the base station.This uplink channel detection method in the Section 8.4.6.2.7.1of the IEEE 802.16e/D5 preliminary specifications can be made amendment, to incorporate into and to support effective feedback method of communicating signals of the present invention.Notion is to use and the identical uplink channel detection method of Section 8.4.6.2.7.1 of the IEEE 802.16e/D5 preliminary specifications, to allow BS estimating uplink channel response.Yet, each code element in the detecting area (up link (UL) frame, wherein the part of SS emission detection waveform), send each symbol interval that UL surveys waveform and can follow the symbol interval that can send feedback waveform (channel waveform) by the SS of emission detection waveform.UL surveys waveform makes BS can estimate the UL channel, and it is used to estimate feedback (channel) waveform launched then, and this has embodied effective feedback method of the present invention.

Below be that first example that the present invention effectively feeds back is incorporated into by in the defined communication system of IEEE 802.16e/D5 preliminary specifications.Uplink channel detection method among the Section 8.4.6.2.7 of IEEE 802.16e is made amendment, thereby it is surveyed the waveform except comprising, also comprise instruction, be used for the optional direct transmission of the DL channel coefficients (channel estimating) of a plurality of subcarriers.This modification has been expanded UL channel detection signal and has been transmitted, and to allow the closed loop transmission in FDD system and the TDD system, does not wherein carry out the calibration of BS array transceiver.This modification is made up of the added field among the UL_Sounding_Command_IE (), and it is the message that BS could be configured and be transmitted into SS, is used for pointing out or instructs whether channel coefficients will be launched with the detection waveform of detecting area.When use was used for this function of the direct transmission of channel coefficients, by the detection waveform permission BS estimation UL channel of probe command appointment, then, BS used it to estimate the DL channel coefficients that is sent by SS in detection waveform feedback fraction.Then, can use the DL channel coefficients of these estimations, to carry out closed loop transmission by BS.Can be used to order or instruction SS sends effective feedback waveform, as follows by an example of the message of BS configuration and emission:

Table 1:UL_Sounding_Command_IE ()

Grammer	Size	Note
			UL_Sounding_Command_IE(){
Expansion UIUC	4 bits	0x09
			Length	4 bits	Variable
Detection _ type	1 bit	0=type A1=type B
			Send and survey the report sign	1 bit
If (detection _ type==0)
			Comprise the feedback code element		0=does not have feedback code element 1=and comprises feedback code element (seeing Section 8.4.6.2.7.3)
Number _ detection _ code element	3 bits	The detection code element total number that distributes in this detecting area order, from 1 (" 000 ") to 2 3＝8(“111”)

Separable type	1 bit	0: take the whole subcarriers 1 of indication in wearing: the subcarrier that takies extraction
			If (separability type==0)		(using the separability of cyclic shift)
Largest loop displacement mark P	2 bits	00:P=4; 01:P=8; 10:P=16,11:P=32
			Else{		(using the separability that extracts)
Decimation value D	3 bits	Every D subcarrier of surveying in distributing surveyed.Decimation value D is 2 (2 add this value) power, therefore, and 4,8, reach maximum 64.
			Extract the skew randomization	1 bit	0=does not have the randomization 1=of the skew extracted with the definite extraction skew of pseudo-random fashion
}
			For (i=0; I＜number _ detection _ code element; I++)
The acquisition code meta-tag	3 bits	Code element mark in the detecting area, from 1 (bit " 000 ") to 2 3=8 (bit " 111 ")
			The CID number	4 bits	The shared CID number that should survey distribution
For (j=0; J＜CID number; J++)
			The basic CID that shortens	12 bits	The 12LS bit of the basic CID value of MSS
Start frequency band	7 bits	From maximum 96 bands (depending on the size of FFT)
			Number of frequency bands	7 bits	What be used to survey is mutually related
The power assignment method	2 bits	The equal constant power of 0b00=; 0b01=reserves; 0b10=depends on interference.Every sub-carrier power restriction; 0b11=depends on interference.The gross power restriction
			Power ascension	1 bit	The 0=inactivity promotes 1=power ascension
Many days line index	1 bit	0=MSS only surveys the first antenna 1=MSS and surveys whole antennas

If (separability type==0)
			Mark m is shifted circulation timei	5 bits	By a plurality of (from 0 to P-1) N/P cyclic shift time domain code element, wherein N=FFT size, and P=largest loop displacement mark.
Else{
			Extract offset d	6 bits	The relative start offset position of the subcarrier that first detection occupies in surveying distribution
}
			Periodically	2 bits	The single order of 00=, aperiodicity or periodicity stop the every frame of 01=and repeat to survey once up to stopping the per 4 frame repetitive instructions of 10=of the per 2 frame repetitive instructions of 10=once
}
			}
Else{
			Displacement	2 bits	The displacement of the optional FUSC displacement of 0b00=PUSC displacement .0b01=FUSC displacement .0b01=.0b11=adjacent sub-carriers
IDcell	6 bits
			Number _ detection _ code element	3 bits
For (i=0; I＜number _ detection _ code element; I++)
			The CID number	7 bits
For (j=0; J＜CID number; J++)
			The basic CID that shortens	12 bits	The 12LS bit of the basic CID value of MSS
Subchannel offset	7 bits	Be used to carry the minimum mark subchannel of bursting, originate in subchannel 0
			Subchannel number	3 bits	Subchannel number with follow-up mark is used for carrying and bursts

Periodically	2 bits	The single order of 00=, aperiodicity or periodicity stop the every frame of 01=and repeat to survey once up to stopping the per 4 frame repetitive instructions of 11=of the per 2 frame repetitive instructions of 10=once
			The power assignment method	2 bits	The equal constant power of 0b00=; 0b01=reserves; 0b10=depends on interference.Every sub-carrier power restriction; 0b11=depends on interference.The gross power restriction
Power ascension	1 bit	The 0=inactivity promotes 1=power ascension
			}
}
			}
Fill	Variable	IE is filled into the eight bit byte border.Bit should be set to 0
			}

Notice that the instruction among the IE can be specified special code meta-tag and specific separability type or from the method for a plurality of methods that are used for making up channel waveform.If field " comprise feedback code element " is set to 1, then UL probe command IE () allows or instruction SS (MSS) carries out to direct transmission BS, DL channel coefficients and UL detection waveform.This function provides downlink channel status information to BS in the FDD system and TDD system that do not carry out the calibration of BS array transceiver.After enabling this function or instruction, the DL channel coefficients is encoded, as described below, and this DL channel coefficients to be launched in one or more feedback code elements, this feedback code element is immediately following after being used to launch each code element of UL detection waveform.In this case, use this UL to survey waveform,, thereby can estimate by BS by the feedback code element of SS emission with estimation UL channel by BS.Then, the feedback code element of coding can be used to allow the closed loop transmission on the down link.

There are two kinds of situations in the value that depends on separability type field/instruction.First kind of situation, if the separability type is 0 (surveying the cyclic shift separation property in the waveform), then single feedback code element is followed after being assigned each detection code element of UL_Sounding_command_IE ().In this feedback code element, the SS antenna of emission detection is with the feedback waveform of launching code in surveying code element, and this waveform has taken and distributed to the identical surveying tape of detection waveform.U (wherein, u is the cyclic shift mark in the SS probe command) the encoder feedback waveform of individual SS is defined as two kinds of situations: first kind of situation is: but SS has single transmitting antenna has a plurality of reception antennas, and the probe command of being told IE is to survey whole antennas (" many days line index " is set to 1).In this case, single transmission antennas transmit is surveyed waveform, and this detection waveform is applicable at the single transmitting antenna of surveying on the code element, and feeds back waveform below the symbol interval emission at next:

$Z_u\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,u}}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}\left(k\right)s_u\left(k\right)\exp \{-j2\mathrm{\πk}(m-1+(l-1)M_{m,u})/{\mathrm{\α}}_u\}$

Wherein

For the estimation DL channel coefficients (channel estimating) between m the reception antenna of subcarrier k, a l BS transmitting antenna and u SS; β _uBe that ratio is regulated, be used to make Z _uThe average transmit power of feedback waveform (k) (all average between the frequency) is 1; s _u(k) be the detection sequence (known array) of Section 8.4.6.2.7.1; M _{M, u}Be that u SS goes up the reception antenna number; α _uBe M _{M, u}M _bAnd M _bIt is the number of BS transmitting antenna.

Second kind of situation is, for the separability type that is 0, when SS has the number of transmit antennas that equals the reception antenna number.In this case, by encoder feedback waveform be in the SS antenna emission of the cyclic shift mark of UL probe command middle finger dispensing u:

$Z_u\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}{\hat{H}}_{u,l}\left(k\right)s_u\left(k\right)\exp \{-j2\mathrm{\πk}(l-1)/{\mathrm{\α}}_u\}$

Wherein For subcarrier k, a l BS transmitting antenna and the estimation DL channel coefficients (channel estimating) between the SS antenna of the cyclic shift mark of UL probe command middle finger dispensing u; β _uBe that ratio is regulated, be used to make Z _uThe average transmit power of feedback waveform (k) (all average between the frequency) is 1; s _u(k) be the detection sequence (known array) of Section 8.4.6.2.7.1; α _uBe M _bAnd M _bIt is the number of BS transmitting antenna.

When the separability type in the UL probe command is 1 (surveying the extraction separability in the waveform), then the detection code element of each distribution is followed the feedback number of symbols that equals the BS number of antennas.In this case, will launch the DL channel coefficients of i antenna for base station to this SS antenna of following k subcarrier on the subcarrier k of i the feedback code element of distribute after surveying code element at the SS antenna of launching on the subcarrier k that surveys code element.With equation form, will launch on l code element following surveying after the code element at the SS that surveys emission detection signal on the subcarrier k of code element

Wherein

It is DL channel coefficients from l BS antenna to this SS antenna.

Notice that the UL probe command is that BS is the message of target communication unit (SS) configuration, and wherein, this message has pointed out to be used for obtaining from the target communication unit of a plurality of subcarriers the ad hoc approach of channel estimating.For example, an ad hoc approach is to comprise having the feedback code element that extracts the type separability.As another example, having the detection waveform that extracts the type separability is another ad hoc approach.After target communication unit was launched this message, target communication unit received this message at BS, made up channel waveform according to this ad hoc approach, and launched this channel waveform to BS, provided channel knowledge with the BS to a plurality of subcarriers.BS receives from channel waveform target communication unit, that make up according to ad hoc approach, and can determine the channel estimating of a plurality of subcarriers based on the channel waveform that is received then, and is described above.

Shall also be noted that UL probe command message can be arranged to a plurality of target communication unit, instruct in a plurality of target communication unit each, with while send channel waveform.When BS received a plurality of channel waveform, it can determine in a plurality of target communication unit the channel estimating of each subsequently, as former description.

Can following additional options or its combination be incorporated into effective feedback method of the present invention by the above example in the defined communication system of IEEE 802.16e/D5 preliminary specifications and can make amendment:

Designator can be added in the table, whether the feedback waveform that is used to specify by a plurality of SS antenna emissions takies identical feedback symbol interval (and will be separated by the BS with the processing of common symbol estimation/SDMA type receiver), perhaps whether take different feedback code element (wherein BS can decode them, and does not have any mutual interference).If the feedback waveform by SS antenna emission will take different feedback code elements, then the SS antenna is determined will be shifted by the circulation timei of this SS antenna among the probe command IE value of mark value of the particular feedback code element that takies.

Designator can be added in the table, be used to specify the phase-shift coding that will have or not have at the channel coefficients that feedback be launched in the code element in the previous equations.If will do not had phase-shift coding by the channel coefficients of launching in the feedback code element, then the feedback channel coefficient of each BS and each SS antenna and given subcarrier will emission individually on subcarrier combination and feedback symbol interval.Another designator can be added in this table, be used to specify the M of given SS antenna _bIndividual channel coefficients is launched in specific feedback symbol interval, and the M of this SS antenna _bThe M of each in the individual BS antenna _bThe continuous N of individual coefficient in this feedback symbol interval _bLaunch on the individual subcarrier.In this case, the designator of the item that had before increased the weight of can point out whether the feedback code element of different SS takies (with receiving processing in the SDMA at BS place classification) identical or different feedback symbol intervals.

Should be noted that importantly the separability type (circulation or extraction) that is used for surveying code element not necessarily is used for one or more follow-up feedback code elements.For effective feedback strategy of the present invention, survey code element and be used to allow BS to estimate the UL channel response simply, thereby the feedback waveform of launching in follow-up feedback symbol interval can be decoded.Can use any combination of coding method that is used to survey waveform that utilizes the coding method of feedback waveform.

Fig. 8 shows the device 800 that is used for transfer channel knowledge.As shown in the figure, device 800 comprises: receiver 801, channel estimation circuit 803, channel waveform circuit 805 and transmitter 807.Receiver circuit 801 is provided for receiving the signal from the source communication unit that comprises a plurality of subcarriers.Channel estimation circuit determines to be received from a plurality of channel estimating of a plurality of subcarriers of source communication unit, and waveform circuit 805 is provided for producing channel waveform based on a plurality of channel estimating.Then, this channel waveform is transmitted into source communication unit, so that provide channel knowledge to source communication unit.

Fig. 9 is the flow chart of device 800 operations of Fig. 8.Especially, Fig. 9 shows the required step that is used for target communication unit to source communication unit transfer channel (for example, downlink channel) knowledge.As previously discussed, this channel comprises a plurality of subcarriers.Logic flow starts from step 901, wherein received signal (for example, down link signal).In step 903, determine a plurality of channel estimating of this signal.Especially, for each subcarrier of received signal, determine at least one channel estimating.In step 905, produce channel waveform.As previously discussed, this channel waveform is based on this a plurality of channel estimating.At last,, this channel waveform is transmitted into source communication unit, so that transmit downlink channel knowledge in step 907.

Figure 10 is the device 1000 that is used to recover channel estimating (for example Downlink channel estimation).As shown in the figure, device 1000 comprises: emittor/receiver 1001, channel estimation circuit 1003, channel waveform restore circuit 1005.Emittor/receiver circuit 1001 is used to receive the signal that comprises waveform, and is used to launch message, and this message has been specified a method of a plurality of possibility methods that are used for making up channel waveform.Described above, channel waveform comprises a plurality of channel estimating, and wherein these a plurality of channel estimating comprise in a plurality of subcarriers at least one channel estimating of each.Estimating circuit 1003 is provided for the receive channel (for example, uplink channel) of estimating received signal.At last, channel waveform restore circuit 1005 is provided for the receive channel based on received signal and estimation, recovers the estimation of a plurality of channel estimating.

Figure 11 is the flow chart that device 1000 operations are shown.Logic flow starts from step 1101, wherein receiving uplink signal (for example, uplink signal).Described above, uplink signal comprises channel waveform, and this channel waveform has a plurality of channel estimating (for example, Downlink channel estimation), and wherein a plurality of channel estimating comprise in a plurality of subcarriers at least one channel estimating of each.In step 1103, the estimating circuit 1003 by uplink channel carries out channel estimating.Especially, in order to recover information, need suitably estimate channel from uplink signal.In case suitably estimated channel, can recover information from uplink signal.Like this, in step 1105, circuit 1005 is by recovering to be embedded in the channel waveform in the uplink signal, recover the Downlink channel estimation in the uplink signal, and estimate (for example, as required, putting upside down the channel waveform cataloged procedure) channel estimating from channel waveform.Persons of ordinary skill in the art will recognize that channel estimating can be used for the auxiliary source communication unit and customize to the transmission characteristic of the subsequent transmission of target communication unit.Example includes but not limited to that definite and application emission weighting is used for transmit beam-forming or imports more/export more (MIMO) transmission; Carrying out frequency selective scheduling, frequency band selection, modulation and code rate selects or the like.

Should be noted that above discussion provides a kind of method, being used for provides channel knowledge to the transmitter that is used for closed loop transmission effectively.Mobile device is encoded to a plurality of broad-band channels, to transmit in single or minority OFDM code element.A plurality of mobile devices are launched its feedback in the identical time, and the base station uses its aerial array, are used to separate the feedback from a plurality of users.Should be appreciated that above employed equation is used to provide the example of various embodiments.Persons of ordinary skill in the art will recognize that and can replace other equation, and without departing from the spirit and scope of the present invention.In addition, those skilled in the art will recognize that, under situation without departing from the spirit and scope of the present invention, can carry out multiple modification, change, combination to the foregoing description, and these modifications, change and combination should be regarded as within the scope of the present invention.Can expect that these modifications, change and combination are all in following claim institute restricted portion.

Claims (12)

1. method is used for target communication unit and transmits the knowledge of the channel that comprises a plurality of subcarriers to source communication unit, said method comprising the steps of:

Determine to be received from a plurality of channel estimating of a plurality of subcarriers of described source communication unit;

Based on described a plurality of channel estimating, produce channel waveform; And

By launching described channel waveform, transmit the knowledge of described channel to described source communication unit.

2. according to the process of claim 1 wherein that described channel waveform comprises the combination of described a plurality of channel estimating.

3. according to the process of claim 1 wherein that described channel waveform is based at least one in the following content:

$Z_u\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,u}}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}\left(k\right)s_u\left(k\right)\exp \{-j2\mathrm{\πk}(m-1+(l-1)M_{m,u})/{\mathrm{\α}}_u\};$

$Z_u\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}{\hat{H}}_{u,l}\left(k\right)s_u\left(k\right)\exp \{-j2\mathrm{\πk}(l-1)/{\mathrm{\α}}_u\};$

$Z_u\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,u}}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}\left(k\right)q_u\left(k\right)\mathrm{\δ}\left({(k+1-(l-1)M_{m,u}-m)}_{M_{m,u}{M}_b}\right);$ And

$Z_{u,m}\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}\left(k\right)q_{u,m}\left(k\right)\mathrm{\δ}\left({(k+1-l)}_{M_b}\right);$

Wherein

It is the channel estimating between the reception antenna of mark m at the described sources traffic transmitting antenna of subcarrier, mark l for mark k and described target communication unit place;

Be the subcarrier for mark k, the source communication unit transmitting antenna of mark l and the channel estimating between the destinations traffic place reception antenna; The δ if n equals zero (n) is 1, and δ (n) is 0 in other cases; β _uIt is scale factor; q _{U, m}(k), q _{U, m}(k) and s _u(k) be known array; M _{M, u}It is the reception antenna number at described target communication unit place; α _uIt is translocation factor; And M _bIt is the number of transmit antennas at described source communication unit place.

4. according to the method for claim 1, further may further comprise the steps: survey waveform and channel waveform to described source communication unit send channel.

5. method that is used to obtain channel estimating comprises:

Reception comprises the signal of channel waveform, and described channel waveform has a plurality of channel estimating, and wherein said a plurality of channel estimating comprise: at least one channel estimating of each in a plurality of subcarriers;

Estimate the receive channel of described received signal; And

Based on the receive channel of described received signal and described estimation, recover the estimation of described a plurality of channel estimating.

6. method as claimed in claim 5 further may further comprise the steps:

Receive pilot signal; And

The step of wherein estimating described receive channel may further comprise the steps: based on the pilot signal of described reception, estimate described receive channel.

7. one kind is used for the transfer channel estimation approach, may further comprise the steps:

Receive message, described message is pointed out following at least ad hoc approach, that is, this method is used for providing channel estimating from the target communication unit of a plurality of subcarriers;

Make up channel waveform according to described ad hoc approach, so that the channel estimating of a plurality of subcarriers to be provided; And

Launch described channel waveform, determine the channel estimating of described a plurality of subcarriers with the auxiliary source communication unit.

8. according to the method for claim 7, wherein said channel waveform comprises at least one in the following content:

Survey waveform; And

A plurality of channel estimating of a plurality of subcarriers.

9. method that is used for obtaining at the source communication unit place channel estimating said method comprising the steps of:

Configuration is used for the message of target communication unit, and described message is pointed out following at least ad hoc approach, that is, this method is used for obtaining channel estimating from the described target communication unit of a plurality of subcarriers;

Launch described message to described target communication unit;

Reception wherein makes up described channel waveform according to described ad hoc approach from described target communication unit channel waveform; And

Based on the channel waveform of described reception, determine the channel estimating of described a plurality of subcarriers.

10. according to the method for claim 9, wherein said channel waveform comprises at least one in the following content:

Survey waveform; And

A plurality of channel estimating of a plurality of subcarriers.

11. a device that is used for transfer channel knowledge, described device comprises:

Receiver circuit is used to receive the signal from the source communication unit that comprises a plurality of subcarriers;

Channel estimation circuit is used to determine be received from a plurality of channel estimating of a plurality of subcarriers of described source communication unit;

The channel waveform circuit is used for based on described a plurality of channel estimating, produces channel waveform; And

Transmission circuit is used for described channel waveform is transmitted into described source communication unit, so that provide channel knowledge to described source communication unit.

12. according to the device of claim 11, wherein said channel waveform is based in the following content at least one:

$Z_u\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,u}}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}\left(k\right)s_u\left(k\right)\exp \{-j2\mathrm{\πk}(m-1+(l-1)M_{m,u})/{\mathrm{\α}}_u\};$

$Z_u\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}{\hat{H}}_{u,l}\left(k\right)s_u\left(k\right)\exp \{-j2\mathrm{\πk}(l-1)/{\mathrm{\α}}_u\};$

$Z_u\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}\underset{m=1}{\overset{M_{m,u}}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}\left(k\right)q_u\left(k\right)\mathrm{\δ}\left({(k+1-(l-1)M_{m,u}-m)}_{M_{m,u}{M}_b}\right);$ And

$Z_{u,m}\left(k\right)={\mathrm{\β}}_u\underset{l=1}{\overset{M_b}{\mathrm{\Σ}}}{\hat{H}}_{u,m,l}\left(k\right)q_{u,m}\left(k\right)\mathrm{\δ}\left({(k+1-l)}_{M_b}\right);$

Wherein

It is the channel estimating between the reception antenna of mark m at the described sources traffic transmitting antenna of subcarrier, mark l for mark k and described target communication unit place;

Be the subcarrier for mark k, the source communication unit transmitting antenna of mark l and the channel estimating between the destinations traffic place reception antenna; The δ if n equals zero (n) is 1, and δ (n) is 0 in other cases; β _uIt is scale factor; q _{U, m}(k), q _{U, m}(k) and s _u(k) be known array; M _{M, u}It is the reception antenna number at described target communication unit place; α _uIt is translocation factor; And M _bIt is the number of transmit antennas at described source communication unit place.

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