CN1535065A - Method of detecting expanding frequency code in channel - Google Patents

Abstract

A method for detecting the frequency spreading code in channel includes obtaining the active intermediate code in channel while obtaining the impact responses of various channels, finding the possible frequency spreading code as the one to be determined, intercepting a data segment, detecting it by known and undetermined frequency spreading codes to obtaine the de-spread-data relative to frequency-spreading code, calculating the power of the de-spread data relative to each frequency-spreading code, calculating the ratio of the data power for the frequency-spreading code to the data power for known code, and determining that the frequency spreading code to be determined is just the active one if the ratio is greater than predefined threshold.

Description

A kind of method that detects the spreading code in the channel

Technical field

The present invention relates to moving communicating field, particularly the method for the spreading code of all uses in the detection descending time slot in TD-SCDMA (time-division-synchronously multiple access insert) CDMA mobile communication systems.

Background technology

In CDMA bandspread communication system, many users share same carrier frequency, and system relies on specific signature waveform to distinguish each user.These signature waveforms generally all are mutually orthogonal sign indicating numbers.But because the influence of multipath, the orthogonality of intersymbol is destroyed.Traditional multiuser detection generally adopts methods such as MMSE and PIC to calculate.And the TD-SCDMA system adopts associated detection technique.Since adopt associated detection technique, advanced technologies such as smart antenna and software radio, and the performance of TD-SCDMA system and the utilance of frequency spectrum all increase.This is a big advantage of TD-SCDMA system.

In the TD-SCDMA communication system, the signal r=Ad+n (t) of receiving terminal, wherein, A is a sytem matrix, and d is the user data vector, and n (t) is an additive white noise.And the joint-detection that adopts in the TD-SCDMA communication system mainly is based on the signal that the computing of A matrix obtains receiving terminal, disturbs to eliminate MAI and ISI.And the A matrix is to be obtained by user's the spreading code and the convolution of channel, because user's spreading code is known in base station side, each user's channel parameter, base station also can obtain by intermediate code (Midamble) part is carried out computing, so joint-detection is easier to accomplish at the base station side ratio.If but joint-detection is applied to mobile terminal side, because amount of calculation is big, comparatively difficulty just becomes.Because user to be detected does not also know that how many users are arranged in the system, do not know what the used spreading code of each user is yet.Go to obtain required parameter so must do some detections,, then, could carry out joint-detection again, to obtain the symbol that transmit leg is sent to obtain the used spreading code of each user in end side.

Summary of the invention

The object of the present invention is to provide a kind of method that in the descending time slot signal, detects spreading code, adopt the information of these spreading codes, just can carry out joint-detection in terminal.

For realizing purpose of the present invention, we provide a kind of method that detects the spreading code that uses in the descending time slot, and it comprises the steps: a) to obtain effective intermediate code in the channel, obtains the impulse response of each channel simultaneously; B) corresponding relation according to intermediate code and spreading code finds possible spreading code as spreading code undetermined; C) the intercepting one piece of data carries out joint-detection to spreading code known and undetermined, obtains the despread data of corresponding spreading code; D) calculate the power of the despread symbols data of each spreading code correspondence; E) calculate the power of spreading code despread symbols undetermined and the ratio of known code data power, if greater than predetermined threshold value, then this uncertain sign indicating number is effective spreading code.

As from the foregoing, by the method for the above-mentioned detection spreading code in the time slot channel, we can carry out the detection of spreading code easily in terminal, and its amount of calculation is little, and is simple to operate.

Description of drawings

Fig. 1 is the corresponding relation figure between expression intermediate code and the spreading code;

Fig. 2 is the schematic diagram of a time slot of TD-SCDMA of the present invention system;

Fig. 3 is the flow chart that realization of the present invention detects the spreading code undetermined in the time slot.

Embodiment

Below in conjunction with accompanying drawing specific embodiments of the invention are described.Need to prove that at this present invention is not limited to the following examples, the following examples are exemplary explanation.

In the TD-SCDMA system, our known distribution method that 3 kinds of intermediate codes (midamble) are arranged, it is respectively:

1) terminal is specified the distribution of intermediate code;

2) distribution method of default intermediate code;

3) distribution method of common intermediate code.

Below we are example with the distribution method of default intermediate code:

In the TD-SCDMA system, system will broadcast in a time slot the maximum intermediate code that can support that what different times are offset, and this value can only be even number, as 2,4, and 6,8,10,12,14,16.

Carry out joint-detection, how many different intermediate codes at first will know has in channel and each user's channel parameter, and then obtains each user's spreading code.

There are what different intermediate codes to obtain in the channel by a sliding correlation detector or by LS (least square method) algorithm.Because the intermediate code that each user receives part all is to move same basic intermediate code by circulating to obtain.Can do to slide by this basic midamble code at user side so and be correlated with, we can obtain having in the system intermediate code of what different time shifts like this.After obtaining effective intermediate code, next step is the spreading code that how to obtain each user.

Owing to adopt the distribution method of default intermediate code, between intermediate code and the spreading code corresponding relation arranged.Referring to Fig. 1, Fig. 1 is 6 o'clock the intermediate code and the corresponding relation of spreading code for time delay intermediate code number.But these corresponding relations can not the perfect representation intermediate code and spreading code between one-to-one relationship, because, in a time slot, can support different during system broadcasts, numerical value is respectively 2,4,6,8,10,12,14 and 16 intermediate code, at this, be that 6 o'clock corresponding relation is an example only with intermediate code.

As shown in Figure 1, C ₁₆ ⁽¹⁾And C ₁₆ ⁽²⁾All corresponding m ⁽¹⁾, C ₁₆ ⁽³⁾And C ₁₆ ⁽⁴⁾All corresponding m ⁽²⁾... while C ₈ ⁽¹⁾Also corresponding m ⁽¹⁾If system adopts 8 spread spectrum codes C ₈ ⁽¹⁾, so according to the characteristic of OVSF (variable spread spectrum is than orthogonal code) sign indicating number, 16 spread spectrum codes C ₁₆ ⁽¹⁾And C ₁₆ ⁽²⁾All can not in system, exist.

Describe in detail below and how to remove to define what users and employed spreading code, because according to the number of the corresponding relation of the spreading code of above-mentioned existence and intermediate code and known effective intermediate code, we can adopt and come to determine effective spreading code in the following method.The fraction data of the intermediate code front of a time slot of intercepting, the size that how much has determined its amount of calculation of these data, referring to Fig. 2, as can be seen from Figure 2,352 chips were arranged, as can be known before intermediate code by simulation test, the partial data of this intercepting is a 16-352 chip, but preferred chip lengths is 64 chips, because this moment, operand was not very big, and has certain accuracy.By using known spreading code (because active user's spreading code is known) to do joint-detection, can obtain one group of despread data then corresponding to each spreading code with the spreading code undetermined that may adopt.These group data comprise the data of N spreading code.

${\hat{d}}_s^{\left(k\right)}=\[{\hat{d}}_{S,1}^{\left(k\right)},\·\·\·\·\·\·{\hat{d}}_{S,M}^{\left(k\right)}\],---k=1,......N$

Can calculate the power of the despread data of each spreading code correspondence then, as follows formula:

$P_s^{\left(k\right)}={\left|\right|{\hat{d}}_s^{\left(k\right)}\left|\right|}^2,---k=1,......N$

If the ratio of sign indicating number undetermined and the corresponding despreading data power of spreading code to be detected is greater than certain amplitude, as greater than 1, just can think that this spreading code is effective (supposing that k=1 is user to be detected), formula as follows:

$f_s=\frac{P_s^{\left(k\right)}}{P_s^{\left(1\right)}},---k=1,......N$

Note that sometimes that in order to improve verification and measurement ratio we can be made as 0.6-0.8 with the ratio of the power of this despread data.

Flow chart below in conjunction with accompanying drawing 3 illustrates the method that detects spreading code in descending time slot of the present invention that realizes.

As can be seen from Figure 3, the method that detects the spreading code of all uses in descending time slot of the present invention comprises the steps: at first, find in the channel effectively the quantity of time delay intermediate code-promptly determine number of users by LS algorithm or other algorithm, obtain the impulse response (S31) of each channel simultaneously;

Secondly, the corresponding relation by intermediate code and spreading code finds the spreading code (S32) that may exist as spreading code undetermined;

The 3rd, the intercepting one piece of data carries out joint-detection to spreading code known and undetermined, obtains the despread data (S33) of corresponding spreading code;

The 4th, calculate the power (S34) of the despread data of each spreading code correspondence;

The 5th, calculate the power of spreading code despread data undetermined and the ratio of known spreading code despread data power, if greater than certain threshold value, then this spreading code undetermined is effective spreading code (S35).

Below we specify method of the present invention by specific embodiment:

Embodiment 1:

If terminal records 6 effective time delay basic midamble codes (midamble) are arranged in the descending time slot, according to this corresponding relation, we can do following analysis:

Have in the system and adopt 16,8, the user of 4 spread spectrum coefficients (SF-spreading factor).According to the characteristic of ovsf code, can not have in the system and adopt 2 or the long spreading code of 1 bit code.

If user's to be detected spreading code is the long C of 8 bit codes ₈ ⁽¹⁾(this sign indicating number is known spreading code) has the spreading code that uses 8 bit codes long so in the system, spreading code may be C ₈ ⁽²⁾..., C ₈ ⁽⁸⁾Also might be the spreading code that adopts 16 bit codes long, spreading code may be C ₁₆ ⁽³⁾... .., C ₁₆ ⁽¹⁶⁾, also may be the user C that adopts 4 bit codes long ₄ ⁽²⁾... C ₄ ⁽⁴⁾These sign indicating numbers all are spreading code undetermined.

To this, we can use C by the said method step ₈ ⁽¹⁾, C ₄ ⁽²⁾, C ₄ ⁽³⁾, C ₄ ⁽⁴⁾Doing joint-detection goes to determine whether contain C in the time slot ₈ ⁽²⁾, C ₄ ⁽³⁾, C ₄ ⁽⁴⁾Spreading code.

We re-use C ₈ ⁽²⁾..., C ₈ ⁽⁸⁾Doing joint-detection goes to determine in the time slot whether C is arranged ₈ ⁽²⁾..., C ₈ ⁽⁸⁾Deng the long spreading code of 8 bit codes.

We re-use C ₁₆ ⁽³⁾... .., C ₁₆ ⁽¹⁶⁾Doing joint-detection goes to determine whether contain C in the time slot ₁₆ ⁽³⁾... .., C ₁₆ ⁽¹⁶⁾Deng the long spreading code of 16 bit codes.

Embodiment 2

If 4 effective midamble are arranged, m in the system ⁽¹⁾, m ⁽²⁾, m ⁽³⁾, m ⁽⁴⁾And user's to be detected spreading code is the long C of 8 bit codes ₈ ⁽¹⁾According to this corresponding relation, we can do following analysis:

Have the spreading code that uses 8 bit codes long in the system, spreading code may be c ₈ ⁽²⁾..., C ₈ ⁽⁸⁾Also might be the spreading code that adopts 16 bit codes long, spreading code may be C ₁₆ ⁽³⁾... .., C ₁₆ ⁽¹⁸⁾These sign indicating numbers all are spreading code undetermined.

To this embodiment 2, we can use C by the said method step ₈ ⁽¹⁾, C ₈ ⁽²⁾, C ₈ ⁽³⁾, C ₈ ⁽⁴⁾Doing joint-detection goes to determine in the time slot whether the C of containing is arranged ₈ ⁽²⁾, C ₈ ⁽³⁾, C ₈ ⁽⁴⁾Spreading code.

We re-use C ₁₆ ⁽³⁾... C ₁₆ ⁽⁸⁾Doing joint-detection goes to determine whether contain C in the time slot ₁₆ ⁽³⁾... .., C ₁₆ ⁽⁸⁾Deng the long spreading code of 16 bit codes.

By low volume data is done joint-detection, we can determine effective spreading code in the time slot channel.Can not detect effectively to such an extent as to some users' of disturbing power is very little, very little when doing the joint-detection of whole time slot data so then because the power ratio of disturbing is less to the detection influence of data, can ignore.

Effectively spreading code and channel impulse response parameter accordingly in the time slot have been arranged, and terminal just can be carried out joint-detection so.

In sum, description of the invention, describe in detail and above-mentioned accompanying drawing be not be used for limiting of the present invention.To those skilled in the art, under instruction of the present invention, can carry out various corresponding modification and can not exceed the spirit and scope of the present invention, not only can be applied to terminal installation as above-mentioned method, but also can be applied to the base station, but this variation should be included within claim of the present invention and the equivalent scope thereof.

Claims (8)

1. method that detects the spreading code in the time slot channel, it comprises the steps:

A) obtain employed basic midamble code and time shift thereof in the descending time slot on the same carrier frequency in this sub-district, obtain the impulse response of each channel simultaneously;

B) corresponding relation according to intermediate code and spreading code finds possible spreading code, as spreading code undetermined;

C) the intercepting one piece of data uses spreading code known and undetermined to carry out joint-detection, obtains the despread data of corresponding spreading code;

D) calculate the power of the despread data of each spreading code correspondence;

E) calculate the power of spreading code despread data undetermined and the ratio of known code despread data power, if greater than predetermined threshold value, then this uncertain sign indicating number is effective spreading code.

2. the method for the spreading code in the detection descending time slot as claimed in claim 1, wherein said step a) also comprises the step that obtains effective intermediate code by correlator or least square method.

3. the method for the spreading code in the detection descending time slot as claimed in claim 1 or 2, the corresponding relation of wherein said intermediate code and spreading code are the pairing relation of distribution method of default intermediate code.

4. the method for the spreading code in the detection descending time slot as claimed in claim 1 or 2, the chip lengths of the partial data of wherein said intercepting are 16-352 chip.

5. the method for the spreading code in the detection descending time slot as claimed in claim 4, the chip lengths of the partial data of wherein said intercepting are preferably 64 chips.

6. the method for the spreading code in the detection descending time slot as claimed in claim 1 or 2, wherein said predetermined threshold value are 1 value.

7. the method for the spreading code in the detection descending time slot as claimed in claim 1 or 2, wherein said predetermined threshold value is 0.6～0.8.

8. the method for the spreading code of detection descending time slot as claimed in claim 1 or 2, wherein said time slot channel are the descending time slots that Time Division-Synchronous Code Division Multiple Access inserts (TD-SCDMA) mobile communication system.