CN1155186C - A method for constructing user training sequences - Google Patents

Abstract

The present invention discloses a method for structuring a user training sequence, which selects a plurality of basic codes with the same cycle according to the requirements of the actual transmission environment of a communication system and the number of users for structuring a user training sequence, namely that the user training sequence is formed by deducing the different basic codes. The error of the channel estimation, which is caused by the too wide distribution of the multipath time delay of a user channel or a synchronization error, can be avoided by using the user training sequence which is obtained by the present invention to carry out channel estimation so as to enhance the accuracy of the channel estimation.

Description

A kind of method of structuring user's training sequence

Technical field

The present invention relates to the method for structuring user's training sequence in a kind of wireless communication system.

Background technology

At present, channel estimation methods based on training sequence can pass through accomplished in many ways, the the 39th to 50 page be entitled as in european telecommunication and the correlation technique collection of thesis optimum and the suboptimum channel estimation methods of joint-detection " in the CDMA mobile communication systems up link based on " (" Optimum and suboptimum Channel Estimation for the Uplink ofCDMA Mobile Radio System With Joint Detection ", Europen Trans.Telecommun.Related Techniques (ETT), Vo1.5, No.1, Jan.-Feb., 39-50) proposed to utilize a basic cycle sign indicating number to construct the method for the middle pilot tone (midamble sign indicating number) of different user, thereby made the maximum likelihood channel estimating to realize by the correlator of a circulation.In this method, each user's middle pilot code (midamble sign indicating number) all is the periodic extension of basic code, the middle pilot code of different user (midamble sign indicating number) all is that the cyclic shift by same sign indicating number obtains, and difference just is the difference of number of shift bits.If the difference of the number of shift bits of supposition neighboring user is a W chip, when receiving terminal utilizes this training sequence to carry out channel estimating, as long as the multidiameter delay maximum of actual user's channel is no more than W chip, the maximum likelihood channel estimating just can guarantee certain accuracy so.But because the complexity of communication environment, actual multipath maximum delay is W chip incessantly, and at this moment each user's channel estimating must be subjected to the interference of previous user's multipath channel, thereby causes the inaccurate of channel estimating.In addition, because the training sequence of different user is to utilize the cyclic shift of same sign indicating number to obtain in this method, this point is had higher requirement synchronously to system.If in a certain user's of receiving terminal synchronous appearance dislocation, this user's first footpath just is estimated as last footpath of adjacent previous user probably mistakenly.

At the problems referred to above, the purpose of this invention is to provide a kind of interference that can reduce between user's multipath channel, improve the method for the structuring user's training sequence of channel estimation accuracy.

Summary of the invention

For achieving the above object, the technical solution used in the present invention is, a kind of method of structuring user's training sequence, and this method is carried out according to the following step:

(1) cycle of selected basic code is the family;

(2) according to the value τ of actual transmissions environment multidiameter delay maximum possible _MaxDetermine the minimum value W that the cyclic shift number difference between the training sequence of two different users is allowed _Min

(3) according to the W that determines in number of users K and the above-mentioned steps (2) _Min, the number A of selected basic code;

(4) according to above-mentioned steps (3) W _MinValue, select can be used for the function of structuring user's training sequence, promptly satisfy expression formula $\left|\underset{l\≠n}{\min }(f(k_{a,l},i)-f(k_{a,n},i))\right|\≥W_{\min }$ Function;

(5) function of selecting according to above-mentioned steps (4) that can be used for structuring user's training sequence is according to expression formula $m_i^{\left(k_a\right)}=m_{f(k_a,i)}^{b_a}$ The training sequence of structure different user.

Wherein: f (k _{A, l}, i) being the subscript function, i the element that it has indicated l the user of a user in organizing training sequence is taken as the f (k of basic code _{A, l}, i) individual element;

F (k _{A, n}, i) being the subscript function, i the element that it has indicated the nth user of a user in organizing training sequence is taken as the f (k of basic code _{A, n}, i) individual element;

m _i ^(ka)Be k _aI element in individual user's the training sequence;

m _{F (ka, i)} ^BaBe b _aF (k in the individual basic code _a, i) individual element.

The minimum value W that cyclic shift number difference between described user's the training sequence is allowed _MinBe set to value τ greater than actual transmissions environment multidiameter delay maximum possible _MaxDivided by the arbitrary value of duration of each chip, that is: W _Min＞τ _Max/ T _c, T wherein _cBe the duration of each chip.

The number of described basic code is set to be not less than the minimum value W that the cyclic shift number difference between number of users K and user's the training sequence is allowed _MinLong-pending again divided by the arbitrary value of the cycle P of basic code, that is: A 〉=KW _Min/ P.

Because the present invention selects identical basic code of a plurality of cycles according to the needs and the number of users of actual transmissions environment, in order to the training sequence of structure different user, promptly user's training sequence is derived by a plurality of different basic codes.For identical number of users, along with the increase in order to the number of the basic cycle sign indicating number of structuring user's training sequence, the minimum value W that the cyclic shift number difference between the training sequence of different user is allowed _MinCan be provided with greatlyyer, thereby system can suitable environment maximum delay also increase, thereby reduced the influence that multipath that channel estimating is subjected to user's interchannel disturbs, even increase when number of users, the system that still can guarantee is suitable in the bigger environment of multidiameter delay.Simultaneously, because the training sequence of neighboring user is to obtain with different cycle sign indicating number structures, difference between the two is the difference of sign indicating number, can not occur mistake because of synchronous dislocation and estimate that therefore, the present invention can improve accuracy of channel estimation.

The present invention is further illustrated below in conjunction with drawings and Examples.

Description of drawings

Fig. 1 is a schematic flow sheet of the present invention;

Fig. 2 is the burst structure figure of TD-SCDMA system transmissions.

Embodiment

At first the present invention is described in detail in conjunction with TD SDMA (TD-SCDMA) system.

With reference to figure 2, this figure is burst (burst) structure of a kind of transmission of TD-SCDMA system.Comprise two data segments and a training sequence section in each burst structure.Supposing has K wireless user in the system, k user's training sequence code is

${\underset{\‾}{m}}^{\left(k\right)}={(m_1^{\left(k\right)},m_2^{\left(k\right)}...m_{L_m}^{\left(k\right)})}^T,k=1...K$

Wherein, L _mBe the length of user's training sequence.In the method, K user's training sequence code is obtained by A basic cycle sign indicating number structure, and we can be divided into the group into A by user's sequence number with whole users, wherein the sequence number k of each user in a group _aSatisfy

k _a?∈{ylmod(y，A)＝a，1≤a≤A，1?≤?y≤K}。The training sequence of all users in each group is derived by same basic cycle sign indicating number and is obtained, and the difference of the training sequence in same group between the different user is cyclic shift number difference.

If m ^B1, m ^B2... mouthful m ^BARepresent A basic cycle sign indicating number respectively, its cycle all is P, wherein:

K then _aI element of individual user's training sequence is:

$m_i^{\left(k_a\right)}=m_{f(k_a,i)}^{b_a}$

And

$m_i^{b_a}=m_{i+P}^{b_a},i=1\·\·\·j{L}_m.$

Above-mentioned m _{F (ka, i)} ^BaBe b _aF (k in the individual basic code _a, i) individual element.

Function f (k _a, form i) can have a variety of, the minimum value W that it can be allowed according to the cyclic shift number difference between the training sequence of two different users in same group given in advance _MinSet, the functional form that then satisfies following formula can serve as the function of training sequence structure,

$\left|\underset{l\≠n}{\min }(f(k_{a,l},i)-f(k_{a,n},i))\right|\≥W_{\min }$

K wherein _{A, l}Represent l user in a group, k _{A, n}Represent the nth user in a group, f (k _{A, l}, i) being the subscript function, i the element that it has indicated the training sequence of l user in a group is taken as the f (k of basic code _{A, l}, i) individual element, f (k _{A, l}, also be the subscript function i), it has indicated k _aI element of individual user's (this user belongs to a group) training sequence is taken as the f (k of basic code _a, i) individual element.

In this building method, W _MinSetting be very important.The multidiameter delay maximum of supposing each subscriber channel is no more than W chip, have only when the cyclic shift number difference between the training sequence of any two different users is not less than W, the estimated result of each subscriber channel just can not be subjected to the interference of other user's multipath channel.In order to reduce the interference between user's multipath channel, W _MinShould be set to be not less than the numerical value of W as far as possible, i.e. W _Min〉=W.In addition, W _MinSetting also be subjected to the influence of system synchronization precision.If occur the mistake of d chip synchronously, so W _MinMust be not less than W+d, i.e. W _Min〉=W+d.From these two angles, W _MinIt is more greatly suitable being provided with.

Utilizing a plurality of basic cycle sign indicating number structure length to be L _mUser's training sequence the time, constitution step is as follows: with reference to figure 1.

In step 1, the cycle of selected basic code is P;

In step 2, according to the value τ of actual transmissions environment multidiameter delay maximum possible _MaxDetermine the minimum value W that the cyclic shift number difference between the training sequence of two different users is allowed _Min, make W _MinT _c＞τ _Max, T wherein _cBe the duration of each chip;

In step 3, according to the W that determines in number of users K and the above-mentioned steps 2 _Min, the number A of selected basic code makes AP 〉=KW _Min

In step 4, according to above-mentioned steps (3) W _MinValue, select can be used for the function of structuring user's training sequence, promptly satisfy expression formula $\left|\underset{l\≠n}{\min }(f(k_{a,l},i)-f(k_{a,n},i))\right|\≥W_{\min }$ Function;

In step 5, according to the function that can be used for structuring user's training sequence of above-mentioned steps 4 selections, according to expression formula $m_i^{\left(k_a\right)}=m_{f(k_a,i)}^{b_a}$ The training sequence of structure different user.

Below in conjunction with prior art the present invention is done further analysis.

Utilizing the basic cycle during sign indicating number structuring user's training sequence, the difference of the cyclic shift number of different user training sequence is very big for the influence of channel estimating.The number difference of cyclic shift is big more, and the distribution of the multidiameter delay of subscriber channel is also just more little to the influence of channel estimating.For identical number of users, along with the increase of A, W _MinThe maximum that can be provided with increases, thereby the maximum delay of system's environment that can be suitable for also increases, thereby has reduced the influence that channel estimating is disturbed by the multipath of user's interchannel, has improved accuracy of channel estimation.

In addition, utilizing one-period to be basic cycle of P during the sign indicating number structuring user's training sequence, W _MinBe subjected to the restriction of number of users.Number of users is many more, the W that is allowed _MinMaximum just more little.If adopt a plurality of basic cycle sign indicating number structuring user's sequences, then W _MinStill can get a bigger numerical value.Like this, when number of users more for a long time, the system that can also guarantee still can be suitable in the bigger environment of multidiameter delay.

If training sequence only adopts a basic code to construct, the difference of each user's training sequence only is the difference of cyclic shift number so.In case in a certain user's of receiving terminal synchronous appearance dislocation, this user's the second footpath signal is taken as the first footpath signal to carry out synchronously, then this user's first footpath just is estimated as adjacent previous user's signal mistakenly.In the present invention, the training sequence of neighboring user is to obtain with different cycle sign indicating number structures, and difference between the two is the difference of sign indicating number, therefore can not occur above-mentioned wrong situation about estimating because of synchronous dislocation.

Be the advantage of sign indicating number structuring user's training sequence of a plurality of basic cycle of example analysis and utilization below with A=2.The maximum number of user that the system of setting up departments is allowed is K, and the multidiameter delay maximum of each subscriber channel is no more than W chip.Under the condition of A=2, if selecting the cycle of basic code is P=KW, the minimum value of cyclic shift number can be set to 2W, it is the time-delay that the training sequence of different user can differ 2W chip, in this case, as long as the multidiameter delay of subscriber channel is no more than 2W chip in the actual transmissions process, the multipath that the estimated value of each subscriber channel can not be subjected to other subscriber channel disturbs.If but user's training sequence is to utilize a basic cycle sign indicating number to derive to obtain, training sequence between the different user only differs the time-delay of W chip, in case the multidiameter delay of subscriber channel surpasses W chip in the transmission, the multipath that the estimated value of each subscriber channel can be subjected to previous neighboring user channel disturbs.In fact, the multidiameter delay of subscriber channel may surpass W chip in the transmission course, as seen adopts a plurality of basic cycle sign indicating numbers to carry out the structure of user's training sequence, can reduce in the channel estimation process, multipath between the subscriber channel disturbs, and improves accuracy of channel estimation.

Being applied to the TD-SCDMA system with the present invention below is that example is further elaborated the present invention.

According to agreement TS_C102 V3.2.0 version, user's training sequence is that the midamble sign indicating number has 144 chip lengths, and the cycle of alternative basic cycle sign indicating number is P=128.Utilize the present invention, the constitution step of user's training sequence is as follows:

(1) a maximum multipath time delay W=8 chip of supposition subscriber channel for fear of the phenomenon that causes channel estimation error owing to timing error, is chosen W _MinBe 16;

(2) set up departments the system maximum allow that number of users is K=16, select two groups of the basic cycle sign indicating numbers that the cross-correlation performance is good, i.e. A=2;

(3) according to W _MinValue, select can be used for the function of structuring user's training sequence, promptly satisfy expression formula $\left|\underset{l\≠n}{\min }(f(k_{a,l},i)-f(k_{a,n},i))\right|\≥W_{\min }$ The subscript function count f (k _a, i), for:

f(k _a，i)＝i+(K-k _a)W

(4) the subscript function of selecting according to above-mentioned steps (3) that can be used for structuring user's training sequence obtains constructing expression formula:

And the training sequence of structuring user's in view of the above.

At receiving terminal, this user's training sequence both can be used for the maximum likelihood channel estimating, also can be used for the matched filtering channel estimating, and channel estimation results is subjected to the multipath interference effect of channel little.

This invention is equally applicable in other communication system, as the TDD-CDMA system.

Claims (3)

1, a kind of method of structuring user's training sequence is characterized in that, this method may further comprise the steps:

(1) cycle of selected basic code is the family;

(2) according to the value τ of actual transmissions environment multidiameter delay maximum possible _MaxDetermine the minimum value W that the cyclic shift number difference between the training sequence of two different users is allowed _Min

(3) according to the W that determines in number of users K and the above-mentioned steps (2) _Min, the number A of selected basic code;

(4) according to above-mentioned steps (3) W _MinValue, select can be used for the function of structuring user's training sequence, promptly satisfy expression formula $\left|\underset{l\≠n}{\min }(f(k_{a,l},i)-f(k_{a,n},i))\right|\≥W_{\min }$ Function;

(5) function of selecting according to above-mentioned steps (4) that can be used for structuring user's training sequence is according to expression formula $m_i^{\left(k_a\right)}=m_{f(k_a,i)}^{b_a}$ The training sequence of structure different user;

Wherein: f (k _{A, l}, i) being the subscript function, i the element that it has indicated l the user of a user in organizing training sequence is taken as the f (k of basic code _{A, l}, i) individual element;

F (k _{A, n}, i) being the subscript function, i the element that it has indicated the nth user of a user in organizing training sequence is taken as the f (k of basic code _{A, n}, i) individual element;

m _i ^(ka)Be k _aI element in individual user's the training sequence;

m _{F (ka, i)} ^BaBe the f (k in ba the basic code _a, i) individual element.

2, the method for structuring user's training sequence according to claim 1 is characterized in that, the minimum value W that the cyclic shift number difference between described user's the training sequence is allowed _MinDetermine according to following method: above-mentioned minimum value W _MinBe value τ greater than actual transmissions environment multidiameter delay maximum possible _MaxDivided by the arbitrary value of duration of each chip, that is: W _Min＞τ _Max/ T _c, T wherein _cBe the duration of each chip.

3, the method for structuring user's training sequence according to claim 1, it is characterized in that the number of described basic code is to determine according to following method: the number of above-mentioned basic code is to be not less than the minimum value W that the cyclic shift number difference between number of users K and user's the training sequence is allowed _MinLong-pending again divided by the arbitrary value of the cycle P of basic code, that is: A 〉=KW _Min/ P.

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