CN1211968C - Match filter for CDMA communication system - Google Patents
Match filter for CDMA communication system Download PDFInfo
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- CN1211968C CN1211968C CN01815337.2A CN01815337A CN1211968C CN 1211968 C CN1211968 C CN 1211968C CN 01815337 A CN01815337 A CN 01815337A CN 1211968 C CN1211968 C CN 1211968C
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- Prior art keywords
- matched filter
- shift register
- accumulator
- output
- sign indicating
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/709—Correlator structure
- H04B1/7093—Matched filter type
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/16—Code allocation
Abstract
The present invention discloses a matched filter which is suitable for spread spectrum code words with complementary characteristics. The present invention comprises a first memory, a second memory, a first shift register, a first accumulator, a second accumulator, a second shift register and a processor. The present invention utilizes the complementary characteristics of the code words to fully embody the ideal correlativity of the code words. The performance of the code words is improved according to the matched filter of the present invention to make the code words more suitable for the synchronization acquisition requirements of a synchronous CDMA communication system.
Description
Technical field
The present invention relates to the receiving equipment of a kind of code division multiple access (CDMA) communication system, particularly a kind of matched filter that is used for cdma communication system.
Background of invention
As everyone knows, the code division multiple access CDMA technology has been acknowledged as the basic fundamental of 3G (Third Generation) Moblie, and cdma communication system is owing to have big capacity, soft capacity, soft handover, high speech quality and low transmitting power and special advantages such as anti-interference and secret is developed rapidly it.
In cdma communication system, because the information that transmitting terminal sends is through the signal after the specific spreading code spread spectrum, therefore to demodulates information be come out at receiving terminal, the information that receives need be multiplied by an identical spreading code that is sent with transmitting terminal, this just requires transmitting terminal spread spectrum code word and receiving terminal spread spectrum code word to realize bit synchronization.Trap setting is used for addressing this problem synchronously.
CDMA is a kind of modulation and multiple access interconnection technique based on spread spectrum communication.In cdma communication system, the used signal of different user transmission information is not to distinguish by frequency difference or time slot difference, but distinguishes with different separately coded sequences.Receiver can be selected the signal that uses the predetermined codes type with correlator in a plurality of CDMA signals.Other signal that uses different sign indicating number types is because different with the local sign indicating number type that produces of receiver and can not be by demodulation.
Usually in cdma system, no matter be base station transmitter or travelling carriage transmitter all with the digital information spread-spectrum of spreading code to transmission, and receiver utilizes local spreading code to the relevant despreading of spread-spectrum signal, solves Useful Information.To realize exactly synchronously local spreading code and the spreading code that receives structurally, in full accord on frequency and the phase place.Cdma system except carrier synchronization that general digital communication system is arranged, bit synchronization, frame synchronization, spreading code be that it is peculiar synchronously.Therefore, the stationary problem of spread spectrum system is more even more important than general digital communication system.
In general, in transmitter and receiver, adopt the clock frequency source of high accuracy and high stability, can remove the unsteadiness of many frequencies and phase place.But owing to objectively exist many prior inestimable uncertain factors, especially in mobile communication, these uncertain factors all have randomness, can not compensate in advance, can only eliminate by synchro system.Therefore, synchro system is indispensable in cdma system, and is very important.
Fig. 1 shows the structure of synchronous trap setting of the cdma system of prior art.As shown in Figure 1, the synchronous trap setting of Chang Gui cdma system comprises antenna 11, accurate synchronizing indicator 12, A/D converter 13, local spreading code word generator 141, correlator 142, memory 15, level detector 16.This device is correctly estimated the phase information of the spread spectrum code word of the information that receives, as the time reference of receiving terminal despreading.Wherein, antenna 11 is used to receive the signal that is sent by transmitting terminal; Accurate synchronizing indicator 12 becomes baseband signal with the signal that receives; A/D converter 13 is transformed to digital signal to baseband signal; Local spreading code word generator 141 is the spread spectrum code word that correlator 142 produces related operation; Correlator 142 is used to calculate the correlation of digital signal and the local spread spectrum code word that produces after the A/D conversion; Memory 15 is used to store the correlation of correlator output, and its memory length is the one-period of spread spectrum code word; Level detector 16 is used for detecting the maximum related value in this cycle, determines the timing of spread spectrum code word thus.
Correlator 142 among Fig. 1 can be sliding correlation detector or matched filter.For sliding correlation detector, it stores receiving symbol, the multiplication mutually that carries out contraposition with the spread spectrum code word that this locality produces, the multiplied result of a spreading code word cycle is carried out addition, behind each chip (chip), the spread spectrum code word step-by-step that this locality is produced is shifted, and still carries out phase multiplication and sum operation, and addition result is exported.
Another implementation of correlator 142 is a matched filter.It stores the spread spectrum code word of the one-period that this locality produces, and makes related operation with input signal.
Fig. 2 is the structure chart of traditional matched filter.Referring to Fig. 2, this matched filter comprises the long shift register in N position 21, long local spreading code word memory 22 and the accumulator 23 in N position.The signal of shift register 21 storage input carries out once displacement to the right after each chip; The local spreading code word memory 22 that the N position is long, it from left to right deposits N position, the N-1 position of local spreading code successively ... the 1st, the multiplication mutually that it carries out contraposition with the signal in leaving shift register 21 in; Accumulator 23 carries out addition with each multiplied result, and is correlation output with the result.
Be PCT/CN00/00028 at application number, invent artificial Li Daoben, denomination of invention in " a kind of spread spectrum multiple access coding method " PCT patent application with zero correlation window, a kind of spread spectrum multiple address code with zero correlation window is disclosed, be called the LS sign indicating number, because the LS sign indicating number is made up of C sign indicating number and S sign indicating number two parts, therefore be called the CS sign indicating number again.The generation method of LS sign indicating number has a detailed description in PCT/CN00/00028, is omitted at this, quotes this document at this as a reference.
The spread spectrum code word that adopts when communication system is to adopt by two sign indicating numbers with orthogonal complement, when the mode of two middle zero paddings of sign indicating number constitutes, such as the spread spectrum multiple address code that discloses in the PCT/CN00/00028 patent application (because the special complementary characteristic of this code word with " zero correlation window ", the structure of sliding correlation detector and traditional matched filter no longer is fit to the requirement of its related operation, therefore, need a kind of novel correlator to realize desired related operation.
The coding method of this new spread spectrum multiple address code that in the PCT/CN00/00028 patent application, provides, have the correlation properties of " zero correlation window " according to the formed spread spectrum multiple address code of this method, promptly the cross-correlation function of each address intersymbol does not have submaximum in zero correlation window, thereby eliminate multiple access and disturb (MAI) and intersymbol interference (ISI), make its corresponding bi-directional synchronization code division multiple access (CDMA) system not have fatal " near-far interference " of traditional code division multiple access (CDMA) system, lay the foundation for setting up jumbo radio digital communication system.The above-mentioned spread spectrum multiple address code with " zero correlation window " has following two characteristics:
The first, the auto-correlation function of each spectrum-spreading address code is zero except that initial point everywhere, and promptly it has optimal characteristic.From the viewpoint of orthogonality, each spectrum-spreading address code and himself are except that locating for zero relative time delay, to any non-zero all complete quadrature in relative time delay.
The second, there is a zero correlation zone in the cross-correlation function between spectrum-spreading address code near initial point.From the orthogonality viewpoint, be completely orthogonal in relative time delay during less than the width of this zero correlation zone between each spectrum-spreading address code.
Owing in the spread spectrum multiple access coding method of PCT/CN00/00028 patent application, utilize the transmission channel of the synchronous fading of two quadratures, transmit two groups of spectrum-spreading address codes respectively, the character of these two groups of spectrum-spreading address codes is opposed each other and yet also complement each other when operation, thereby make its correlation properties have zero correlative window characteristic, promptly the correlation function of each address intersymbol and cross-correlation function do not have submaximum in zero correlation window.And, make sliding correlation detector of the prior art or matched filter no longer be fit to the synchronization acquistion of the spectrum-spreading address code of orthogonal complement characteristic just because of the spreading code characteristic of this kind uniqueness.
Summary of the invention
For solving the above-mentioned problems in the prior art and defective, the object of the present invention is to provide a kind of matched filter that is applied to code division multiple access (CDMA) communication system, be specially adapted to the code division multiple address communication system that is constituted by spectrum-spreading address code word according to the matched filter of the present invention design with orthogonal complement.
Matched filter provided by the invention, it is improved on the basis of existing matched filter structure, makes it more be applicable to the related operation of the spreading code that is made of the sign indicating number with orthogonal complement.
A kind of matched filter that is used for code division multiple address communication system is characterized in that, comprising:
First memory and second memory, storage constitutes two code words with complementary characteristic of local spreading code respectively;
First shift register is used for input signal is shifted;
First accumulator is used for the contraposition multiplied result with the code word of storing in the input signal of first shift register and the first memory, carries out addition;
Second accumulator is used for the contraposition multiplied result with the code word of storing in the input signal of first shift register and the second memory, carries out addition;
Second shift register, the output of first accumulator that is used to be shifted;
Processor is used for the output of second shift register and the output of second accumulator are handled.
By adopting this matched filter of the present invention's design, solve the problem that the relevant device of matched filter of the prior art or slip can not be applicable to the code division multiple address communication system of use " zero correlation window " characteristic spreading code on the one hand, also fully realized the characteristic of this " zero correlation window " orthogonal complement code character on the other hand.
By the description of following execution mode and accompanying drawing, it is clearer that the other objects and features of the invention will become, and identical label is represented same or similar parts in the accompanying drawing.
Accompanying drawing and this explanation one as a part of the present invention are used from the explanation embodiments of the invention, are used to explain principle of the present invention.
Description of drawings
Fig. 1 shows the structure of synchronous trap setting of the cdma system of prior art.
Fig. 2 shows the structure chart of a traditional matched filter.
Fig. 3 shows the structured flowchart according to the matched filter of first embodiment of the invention.
Fig. 4 shows the structured flowchart according to the matched filter of second embodiment of the invention.
Fig. 5 A shows the auto-correlation output according to the matched filter of first embodiment of the invention;
Fig. 5 B shows the auto-correlation output according to the matched filter of second embodiment of the invention;
Fig. 6 A shows the cross-correlation output according to the matched filter of first embodiment of the invention;
Fig. 6 B shows the cross-correlation output according to the matched filter of second embodiment of the invention.
Embodiment
First execution mode
Fig. 3 shows the structured flowchart according to the matched filter of first embodiment of the invention.The realization of the matched filter of present embodiment is to be that example is described with the LS sign indicating number.About the LS sign indicating number, can be referring to the detailed description among the PCT/CN00/00028.
The spreading code that supposing the system adopts is by preceding N position C sign indicating number, back N position S sign indicating number, middle N position 0 formation of mending.Matched filter according to the present invention comprises: length is that be shifted first shift register 31, the length of input signal of being used to of N is that the first memory 32 that is used to store local spread spectrum codes C sign indicating number, the length of N is that the second memory 33, first accumulator 34, second accumulator 35, the length that are used to store local spreading code S sign indicating number of N is second shift register 36 and the adder 37 of 2N.Wherein, first shift register 31 is used to store input signal and moves into a received signal behind each chip; First memory 32 is used to store local spread spectrum code word C sign indicating number, and its storage mode is for being followed successively by from left to right: N position, N-1 position ..., the 1st; Second memory 33 is used to store local spread spectrum code word S sign indicating number, and its storage mode is for being followed successively by from left to right: N position, N-1 position ..., the 1st; First memory 32 carries out contraposition multiplication mutually with first shift register 31, and first accumulator 34 carries out addition with every multiplied result; Second memory 33 carries out contraposition multiplication mutually with first shift register 31, and second accumulator 35 carries out addition with every multiplied result; The result of calculation input of first accumulator 34 moves second shift register 36, makes it to postpone to export behind the 2N.The effect of this second shift register 36 is that the C sign indicating number is handled with corresponding S sign indicating number and S ' sign indicating number correlation simultaneously with the correlation of input C ' sign indicating number; Adder 37 is obtained the correlation of whole codeword with the output of second shift register 36 and the results added of second accumulator 35.The result that this filter calculates is input signal and the local range value that produces the correlation of code word.
Fig. 5 A shows the auto-correlation output according to the matched filter of first embodiment of the invention, it be long with the position be that (preceding 32 is the C sign indicating number for 96 LS sign indicating number, 32 of backs are the S sign indicating number, 32 0 of middle benefits) be example, carry out the output of auto-correlation computation through matched filter shown in Figure 3 when adopting one group of spread spectrum code word.
Fig. 6 A shows according to the output of the cross-correlation of the matched filter of first embodiment of the invention, and it is still long with the position to be that 96 LS sign indicating number is an example, during two groups of spread spectrum code words of employing, carries out the output of computing cross-correlation through matched filter shown in Figure 3.
Second execution mode
Fig. 4 shows the structured flowchart according to the matched filter of second embodiment of the invention.Referring to Fig. 4, comprise also that according to the matched filter of present embodiment length is that be shifted first shift register 31, the length of input signal of being used to of N is that the first memory 32 that is used to store local spread spectrum codes C sign indicating number, the length of N is that the second memory 33, first accumulator 34, second accumulator 35, the length that are used to store local spreading code S sign indicating number of N is second shift register 36 of 2N, be with matched filter structure difference shown in Figure 3, also comprise a multiplier 47 according to the matched filter of second execution mode.Its result of calculation is equivalent to the energy value of correlation.Use the matched filter of this structure further to improve the autocorrelation performance of code word, because, when carrying out auto-correlation computation:
2N is output as before the matched filter: 0 * R
SC=0, and be output as 0+R according to the matched filter shown in Figure 3 of first embodiment of the invention
SC=R
SC, be not 0;
Middle 2N is output as: R
CC(τ) * R
SS (τ)
When τ is 0: R
CC(0)=R
SS(0)=and N, so output main peak value is N
2, and be 2N according to the auto-correlation main peak value of the matched filter shown in Figure 3 of first embodiment of the invention.
When τ was not 0: the output of matched filter all was less than or equal to 0.And be output as 0 according to the matched filter shown in Figure 3 of first embodiment of the invention;
2N is output as behind the matched filter: R
CS* 0=0, and be output as R according to the matched filter shown in Figure 3 of first embodiment of the invention
CS+ 0=R
CS, be not 0.
Fig. 5 B shows the auto-correlation output according to the matched filter of second embodiment of the invention, it be long with the position be that (preceding 32 is the C sign indicating number for 96 LS sign indicating number, 32 of backs are the S sign indicating number, 32 0 of middle benefits) be example, carry out the output of auto-correlation computation through matched filter shown in Figure 4 when adopting one group of spread spectrum code word.
Fig. 6 B shows according to the output of the cross-correlation of the matched filter of second embodiment of the invention, and it is still long with the position to be that 96 LS sign indicating number is an example, during two groups of spread spectrum code words of employing, carries out the output of computing cross-correlation through matched filter shown in Figure 4.By Fig. 5 B and Fig. 6 B as can be seen, improved the autocorrelation performance of code word, and do not had for the peak value size of the cross-correlation of code word and to change, just changed the position of " zero window " according to the matched filter of second embodiment of the invention.
Do not depart from the scope of the present invention and conceive and to make many other change and remodeling.Should be appreciated that the present invention is not limited to certain embodiments, scope of the present invention is defined by the following claims.
Claims (4)
1. a matched filter that is used for code division multiple address communication system is characterized in that, comprising:
First memory and second memory, storage constitutes two code words with complementary characteristic of local spreading code respectively;
First shift register is used for input signal is shifted;
First accumulator is used for the contraposition multiplied result with the code word of storing in the input signal of first shift register and the first memory, carries out addition;
Second accumulator is used for the contraposition multiplied result with the code word of storing in the input signal of first shift register and the second memory, carries out addition;
Second shift register, the output of first accumulator that is used to be shifted;
Processor is used for the output of second shift register and the output of second accumulator are handled;
Described code word with complementary characteristic is the LS sign indicating number, and its preceding N position is the C sign indicating number, and back N position is the S sign indicating number, and middle N position is 0.
2. matched filter as claimed in claim 1 is characterized in that described processor is an adder, is used for addition is carried out in the output of second shift register and the output of second accumulator.
3. matched filter as claimed in claim 1 is characterized in that described processor is a multiplier, is used for the output of second shift register and the output of second accumulator are multiplied each other.
4. matched filter as claimed in claim 1 is characterized in that, described second shift register postpones to export behind the 2N position to the result of first accumulator.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/CN2001/001169 WO2003007519A1 (en) | 2001-07-11 | 2001-07-11 | A match filter for code division multiple access communication system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1452823A CN1452823A (en) | 2003-10-29 |
| CN1211968C true CN1211968C (en) | 2005-07-20 |
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ID=4574831
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN01815337.2A Expired - Fee Related CN1211968C (en) | 2001-07-11 | 2001-07-11 | Match filter for CDMA communication system |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN1211968C (en) |
| WO (1) | WO2003007519A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101242195B (en) * | 2007-12-28 | 2011-11-30 | 清华大学 | A constitution and its operation method for frequency spreading tracking loop |
| CN103152075A (en) * | 2013-02-04 | 2013-06-12 | 太原理工大学 | Digital matching filter for WCDMA (wideband code division multiple access) communication |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3884115B2 (en) * | 1996-12-10 | 2007-02-21 | 三菱電機株式会社 | Digital matched filter |
| EP0936748A3 (en) * | 1998-02-12 | 2003-07-23 | Yozan Inc. | Matched filter bank CDMA communication |
| JP2000078058A (en) * | 1998-06-15 | 2000-03-14 | Katsuyoshi Azeyanagi | Matched filter output analysis and interference wave control type cdma communication system |
| US6345069B1 (en) * | 1998-10-16 | 2002-02-05 | Texas Instruments Incorporated | Simplified cell search scheme for first and second stage |
-
2001
- 2001-07-11 CN CN01815337.2A patent/CN1211968C/en not_active Expired - Fee Related
- 2001-07-11 WO PCT/CN2001/001169 patent/WO2003007519A1/en active Application Filing
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| Publication number | Publication date |
|---|---|
| WO2003007519A1 (en) | 2003-01-23 |
| CN1452823A (en) | 2003-10-29 |
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