CN1351427A - Method and equipment for fast channel estimation with training sequence - Google Patents

Abstract

A method and device for using the training sequence to fastly estimate channel is disclosed. The array G determined by the used training sequence and the measured received signal e is used to determine the estimated pulse response value h of channel. The array M defined by equation h=M.e is calculated in advance according to chosen training sequence and stored in storage. After the received signal e is measured, the estimated pulse response value h of channel can be determined according to h=M.e.

Description

Utilize training sequence to carry out the method and apparatus of channel estimating fast

The present invention relates to the digital mobile communication technical field, particularly relate to the reception technique in the wireless communication system receiver, especially relate to the channel estimation technique in the wireless communication system.

Be different from simple TDMA and cdma system, the TD-CDMA system includes several code channels in each time slot, is used to distinguish the different user in the identical time slot.The multi-access mode that adopts TDMA and CDMA to mix is compared the advantage that has on the performance with the system of simple employing TDMA or CDMA.In the receiver of TD-CDMA system, both need to separate the time slot in every frame, also needed to separate the different code channels (can adopt relevant processing method) in the same time slot.Utilize these methods, just can be separately at receiving terminal with different channel region.After signal that system's transmitting terminal sends was through transmission, the time varying channel in space can add corresponding the interference to transmission signals, and the multipath of mobile channel disturbs and channel also can cause intersymbol interference (ISI) and multiple access interference (MAI).Therefore in order to recover correct transmitting at receiving terminal, must correctly obtain the impulse response of channel, utilize the signal and the resulting channel impulse response that receive correctly to estimate the signal of being launched then.The channel estimating quality has very important influence for systematic function.

In modern wireless communication systems, data-signal is through behind the wireless channel, because the influence of multipath fading and time delay expansion, the decline of signal occurrence frequency selectivity, the time selective fading that receive, signal waveform deforms, and when signal to noise ratio is low, is difficult to the correct signal that recovers emission.In many systems, adopt training sequence (, being called Preamble sign indicating number or Midamble sign indicating number) to realize channel estimating according to the position difference.So-called training sequence is the one group of known code that is used for carrying out channel estimating, and transceiver both sides are known to training sequence.The basic principle of utilizing training sequence to carry out channel estimating is, that utilizes that originator sends is both sides' training sequence in common knowledge, the signal of the training sequence that arrives with destination's actual measurement, calculate channel pulsion phase should, also promptly channel conditions has been carried out effective estimation.

In existing research to the synchronous CDMA system channel estimating, prior art [1] (BerndSteiner and Paul Walter Baier for example, " Low Cost Channel Estimation in the UplinkReceiver of CDMA Mobile Radio Systems ", FREQUENZ 47 (1993) 11-12p292-298.) in, adopted channel estimating, promptly used the midamble sign indicating number as training sequence based on the midamble sign indicating number.Channel estimation methods has adopted no bias estimation, promptly

, wherein

It is the estimated value of h.

, G wherein ^*The conjugation of representing matrix G, G ^TThe transposition of representing matrix G, the channel estimating that this formula obtains are not have partially to estimate, also are least-squares estimation simultaneously.

Certainly, channel estimation methods is not limited in and uses above formula

Carry out.Also have other channel estimating formula, as when traditional matched filter is used for channel estimating, channel estimating is:

, this is that h a kind of has inclined to one side estimation.

In the prior art, behind the signal e that the actual reception that goes out base station measurement arrives, when utilizing the channel estimating formula to carry out channel estimating, need utilize matrix G, after with the soft hardware equipment of base station matrix being carried out complicated calculations such as transposition, conjugation, do multiplying with actual measured signal e again, can obtain channel estimation value.

But, because the base station needs simultaneously the channel of all travelling carriages in this cell/section to be estimated, very complicated, very a large amount of calculating need be finished in the base station in the extremely short time like this, cause the software and hardware demand of base station very high, cost increases, but even so, also be difficult for making instant channel estimating.

The object of the present invention is to provide a kind of method and device that utilizes training sequence to carry out channel estimating fast, feasible software and hardware demand to the base station reduces significantly, and can realize channel estimating more quickly.

According to an aspect of the present invention, provide a kind of method of utilizing training sequence to carry out channel estimating fast, utilized, determined the impulse response estimated value of channel by the matrix G that training sequence determined that is adopted, the received signal e that measures

, it is characterized in that, by formula Defined matrix M is come out according to selected training sequence calculated in advance, is stored in the memory device of base station, and after measuring received signal e, direct basis

Determine the impulse response estimated value of signal.

According to another aspect of the present invention, provide a kind of device that utilizes training sequence to carry out channel estimating fast, utilized, determined the impulse response estimated value of channel by the matrix G that training sequence determined that is adopted, the received signal e that measures

, it is characterized in that, by formula

Defined matrix M is come out according to selected training sequence calculated in advance, is stored in the memory device, and after measuring received signal e, direct basis

Determine the impulse response estimated value of signal.

The present invention directly will be by formula Defined matrix M is come out according to selected training sequence calculated in advance, be stored in the memory device of base station, thereby reduced the base station and carried out a large amount of complicated matrix computations, reduced the software and hardware requirement, not only reduce cost, and can estimate the channel of all travelling carriages in the sub-district rapidly in time.

For making the purpose, technical solutions and advantages of the present invention clearer, by the following examples, and with reference to accompanying drawing, the present invention is described in more detail.

Fig. 1 shows the burst structure of a kind of transmission of TDD cdma system.

Technology involved in the present invention is a key technology in the wireless communication system receiver.Fig. 1 has provided the burst structure of a kind of transmission of TDD cdma system, comprises the structure of frame, time slot, pilot tone, data symbol.Comprise two data blocks and a training sequence piece in each burst structure.The present invention is not limited to the TDD cdma system, it can be applicable to any use training sequence and carries out in the system of channel estimating, although and the situation that is employing midamble sign indicating number as training sequence illustrated in fig. 1, but the present invention is not limited thereto, and it also can be that the preamble sign indicating number waits other modes.

Below the model of channel estimating and principle are described in detail.

Supposing has K wireless user in the system, then promptly comprise K wireless channel in the system model of being discussed, and supposes that the impulse response of its complex value is: $h^{\left(k\right)}={(h_1^{\left(k\right)},h_2^{\left(k\right)}...h_W^{\left(k\right)})}^T,k=1...K---\left(1\right)$ Its length is W.K user's channel response is written as vector form:

H=(h ^{(1) T}, h ^{(2) T}... h ^{(K) T}) ^T(2) number altogether of Unknown Channel coefficient is:

U=KW (a 3) k user's training sequence is: $m^{\left(k\right)}={(m_1^{\left(k\right)}.m_2^k...m_{L+W-1}^{\left(k\right)})}^T,k=1...K---\left(4\right)$

Because the length of supposition channel impulse response is W, therefore the channel intersymbol interference originates from last W-1 element of the data symbol in the data block, initial W-1 sampling in the received signal is subjected to the influence of the time delayed signal of training sequence, promptly there is intersymbol interference (ISI), not as the part of channel estimating.Therefore, the energy of initial W-1 the element of each midamble also not exclusively is used for channel estimating.By the well-determined received signal of training sequence itself L element only arranged.If actual received signal is:

e＝(e ₁，e ₂...e _L) ^T (5)

According to the training sequence m in (4) ^(k), the matrix of L * W is: $G^{\left(k\right)}=\left(G_{\mathrm{ij}}^{\left(k\right)}\right),k=1...K---\left(6a\right)$ $G_{\mathrm{ij}}^{\left(k\right)}=m_{W+i-j}^{\left(k\right)},=1...L;j=1...W---\left(6b\right)$ That is: $G^{\left(k\right)}=\left[\begin{array}{cccc}{m}_W^{\left(k\right)}& m_{W-1}^{\left(k\right)}& ...& m_1^{\left(k\right)}\\ m_{W-1}^{\left(k\right)}& m_W^{\left(k\right)}& ..& m_2^{\left(k\right)}\\ ...& ...& ...& ...\\ m_{W+L-1}^{\left(k\right)}& m_{W-L}^{\left(k\right)}& ...& m_L^{\left(k\right)}\end{array}\right]$ Thereby L * U matrix G is

G=(G ⁽¹⁾, G ⁽²⁾... G ^(K)(7) the added stationary noise of its zero-mean is

N=(n ₁, n ₂... n _L) ^T(8) thus received signal is expressed as

e＝Gh+n (9)

Thereby the problem of channel estimating in fact quite with known formula (9) in G, e obtains the process of h.

Estimate for the impulse response to channel accurately, proposed various channel estimation methods in the prior art.For example the channel estimation methods in the prior art [1] has adopted no bias estimation, promptly

, wherein

It is the estimated value of h.

, it is not estimated for having partially, is least-squares estimation simultaneously yet.

Certainly, channel estimation methods is not limited in and uses above formula

Carry out.Also have other channel estimating formula, as when traditional matched filter is used for channel estimating, channel estimating is:

, this is that h a kind of has inclined to one side estimation.

Because for particular cell/sector, the training sequence that is adopted is generally fixed, therefore core concept of the present invention is, will be by formula Defined matrix M is come out according to selected training sequence calculated in advance, is stored in the memory device of base station.After measuring received signal e, the direct basis in base station

Determine the impulse response estimated value of signal.Thereby avoided complicated matrix operation, and can reach the purpose that the channel of all travelling carriages in the cell/section is estimated fast.

Preferable, when the training sequence of all users in the same sub-district all is when being obtained by cyclic shift by same basic code, matrix (G ^{* T}G) be the Toeplitz matrix of positive definite, i.e. skew symmetric matrix, any one leading diagonal element is identical, and the matrix identical with element on each parallel diagonal of leading diagonal all is the Toeplitz matrix.At this moment, matrix M also is the Toeplitz matrix of positive definite.Simple in order to calculate, value that can the ToepIitz matrix is relevant is calculated earlier, exist in the internal memory, because the Toeplitz matrix is symmetry and antisymmetric matrix simultaneously, so inverse matrix also is symmetry and antisymmetric matrix, therefore as long as storage 1/4 matrix element just can store M, this 1/4 matrix element can be or be equivalent to: any one in four delta-shaped regions dividing by two diagonal of Toeplitz matrix, thus saved internal memory.Concrete when finding the solution the Toeplitz equation group, division arithmetic wherein etc. also can store in advance.

Preferably, when reducing the amount of calculation of base station in channel estimating, in order also to reduce the amount of calculation of travelling carriage in channel estimating, when travelling carriage activates or switches to base station corresponding district/sector, the pairing matrix M of this cell/section sends travelling carriage to by the base station, carry out channel estimating for travelling carriage, thereby reduce the amount of calculation of travelling carriage and the demand of software and hardware, be more conducive to reduce the volume and weight of travelling carriage.

Institute it should be understood that the above only is better embodiment of the present invention, and it is only in order to explain the present invention, and it is unrestricted, except that the above channel does not have inclined to one side estimation formulas and has the inclined to one side estimation formulas, also adopt other channel estimating formula, it is non-to be content of the present invention.

The present invention is applicable to the C/TDMA system, especially be applicable to WCDMD TDD and TD-SCDMA system in the present 3-G (Generation Three mobile communication system), but be understood that, though technical scheme of the present invention is primarily aimed at the wireless communication system of code division multiple access, but be applicable to the frequency division multiple access of the similar transmission structure of employing and the system of time division multiple access too, any engineer with knowledge background such as signal processing, communications, can design corresponding channel estimation methods and device according to the present invention, it all should be included in thought of the present invention and the scope.

Claims (5)

1, a kind of method of utilizing training sequence to carry out channel estimating is fast utilized by the matrix G that training sequence determined that is adopted, the received signal e that measures, and determines the impulse response estimated value of channel

, it is characterized in that, by formula

Defined matrix M is come out according to selected training sequence calculated in advance, is stored in the memory device, and after measuring received signal e, direct basis

Determine the impulse response estimated value of signal.

2, the method for utilizing training sequence to carry out channel estimating fast as claimed in claim 1, it is characterized in that, under the situation that the training sequence of all users in same sub-district obtains by cyclic shift by same basic code, only 1/4 matrix element with matrix M is stored in the memory device, and this 1/4 matrix element is or is equivalent to: any one in four delta-shaped regions being divided by two diagonal of matrix M.

3, the method for utilizing training sequence to carry out channel estimating fast as claimed in claim 1, it is characterized in that, when travelling carriage switched to base station corresponding district/sector, the pairing matrix M of this cell/section was transmitted to travelling carriage, carried out channel estimating for travelling carriage.

4, a kind of device that utilizes training sequence to carry out channel estimating fast utilizes by the matrix G that training sequence determined that is adopted, the received signal e that measures, and determines the impulse response estimated value of channel

, it is characterized in that, by formula

Defined matrix M is come out according to selected training sequence calculated in advance, is stored in the memory device, and after measuring received signal e, direct basis Determine the impulse response estimated value of signal.

5, the device that utilizes training sequence to carry out channel estimating fast as claimed in claim 4, it is characterized in that, under the situation that the training sequence of all users in same sub-district obtains by cyclic shift by same basic code, only 1/4 matrix element with matrix M is stored in the memory device, and this 1/4 matrix element is or is equivalent to: any one in four delta-shaped regions being divided by two diagonal of matrix M.

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