CN1398460A

CN1398460A - Methods and appts. for signal searching using correlation

Info

Publication number: CN1398460A
Application number: CN99817091A
Authority: CN
Inventors: R·R·王; M·G·埃尔－塔胡尼; A·V·加莫诺夫; G·S·克拉夫特索瓦; N·I·舒金
Original assignee: Nortel Networks Ltd
Current assignee: Nortel Networks Ltd
Priority date: 1999-12-17
Filing date: 1999-12-17
Publication date: 2003-02-19
Anticipated expiration: 2019-12-17
Also published as: KR20020055451A; AU3338800A; CN1254927C; CA2394510A1; WO2001045288A1; JP2003517247A

Abstract

A signal searcher for a CDMA communications system has a reference signal generator and a correlator to correlate a reference signal with a received signal in short (signal-coherent) correlation intervals. The code phase of the reference signal is changed through all of N possible code phases in N successive correlation intervals constituting one signal scan cycle. The correlation results for the same code phase for a plurality of the correlation intervals are accumualted over successive signal scan cycles using a combiner and buffer, and the presence and code phase of one or more desired signals in the received signal are determined by a decision unit in dependence upon the accumulated correlation results. In one embodiment all of the correlation results are accumulated; in other embodiments memory requirements are reduced by a accumulating only larger values of the correlation results.

Description

Signal search method and apparatus based on correlation

Technical field

The method and apparatus technical field that the present invention relates to utilize the correlation of received signal and reference signal that signal is searched for is specifically related in the cdma wireless cellular system whether the broadband signal of using CDMA (code division multiple access) existed and the detection technique of code phase.

Technical background

The communication system of using the CDMA signal is in message capacity, frequency planning, and all there is advantage in communication quality to aspects such as the confidentiality of undelegated access and anti-interferences.Yet, in cdma system design, needing to solve a major issue, the echo signal and the local reference signal that produces that comprise in promptly needing are to received signal carried out synchronously accurate.Wherein first step is a signal search process, in this process, one or more parameters are as the frequency of code phase with pseudo noise (PN) signal of forming reference signal, change, and the supposition of echo signal existence is progressively estimated.This uses considerable timing and hardware resource in the cdma system receiver.

Specifically, to may making up of each reference signal parameter value, i.e. each deviation post, or each state of reference signal, all to carry out associative operation, the correlation of gained is adjudicated, judge whether to exist to have the pairing echo signal of respective offsets or position with received signal.

As everyone knows, the signal of communication in the cdma wireless cellular communication system is subject to influence of fading, and the RF signal amplitude of decay and the variation of phase place can cause the mis-behave of signal search process.

In order to resist the quick variation of signal phase, or rapid fading, as IEEE 0-7803-2742-X/95, pages 281-285,1995, described in " DS-SS Code Acquisition in a Rapid Fad ing Envioment " literary composition of Manabu Muka i and Mutsumu Serizawa, accumulation interval TA is divided into a large amount of m continuous short interval T COH, makes TA=mTCOH.Enough weak points of each TCOH duration choosing at interval, signal phase be during this time every interior no significant change, thereby can be used as signal coherence at interval.In accumulation interval TA, be irrelevant adding up corresponding to the correlated results of the reference signal of each skew or position.The correlated results that adds up is used for adjudicating each skew place echo signal and whether exists, yet slow fading may cause that the correlated results that adds up is greatly different with its long-time accumulated value, has so just increased input failure or wrong possibility.Alleviate its influence though can take to increase the time T A that adds up, but increased the unnecessary signal search time.

The influence of slow fading can alleviate by using diversity technique, for example in space diversity reception to communicate, has the signal of relatively independent fading characteristic to be received by two or more space antenna, merges the correlated results of these signals.But space diversity reception to communicate has increased the complexity of receiver, and to use a large amount of space antennas be unpractical, especially little for volume portable receiver.

The U.S. Patent number 5 of distribution on August 27th, 1996,550,811, exercise question compensates the slow fading influence for having told about a kind of time domain diversity apparatus in the article of " SyncAcquisition and Tracking Circuit for DS/CDMA Receiver ": periodically the correlated results of each position or parameter set is offered combiner with a selector switch and carry out noncoherent accumulation.The cycle of switch is according to deciding fading period, thereby the average of the correlated results that adds up asked in the relative signal decay.The shortcoming of this device is that complexity is installed, and needs selector switch and control device thereof, and with the as many combiner of quantity of parameters collection or position.For example, in the IS-95 cdma wireless cellular communication system when travelling carriage search during from pilot signal of base station, total N=32768 possible PN code phase or position.

Andrew J.Viterbi, Addison-wesley Communication Series, provided a kind of signal search method among " CDMA Principles of Spread Spectrum Communications " chapters and sections 3.4.1 " Single-Pass Serial Search " of nineteen ninety-five: in an accumulation interval TA=mTCOH, the m in the signal coherence interval T COH of continuous adjacent relevant estimation added up.In frequency is that the signal bandwidth of 800MHz is in the IS-95 cdma system of 1.25MHz, and the Rayleigh fading cycle is about 20 to 50 milliseconds, and the length of access channel signal accumulation interval may be from 1.2 milliseconds to 2.4 milliseconds.Therefore, in accumulation interval TA, the signal amplitude that can occur causing because of decline changes, thereby has increased input failure or wrong possibility.

The purpose of this invention is to provide the method and apparatus that in communication system such as cdma system, can make things convenient for signal search.

Summary of the invention

According to an aspect of of the present present invention content, the signal searcher of Fig of cdma communication system produces at least one reference signal, and reference signal and received signal are carried out associative operation, and its related interval should enough be lacked, thereby the phase place of received signal does not have marked change in this related interval.The add up correlated results of same code phase of a plurality of above-mentioned related intervals, according to the existence of one or more echo signals in the correlated results judgement received signal that adds up whether and code phase.The code phase of reference signal change in may code phases at N serial correlation all N in the time, forms a signal scan cycle, and correlated results is stored, and adds up in a plurality of signal scan cycle being used for.This part content of the present invention also provides the device of finishing these functions, for example digital signal processor.

The present invention's content has on the other hand provided a kind of method of signal search, wherein received signal is correlated with reference signal, at least one parameter of reference signal changes, produce received signal and the individual different corresponding correlated results that may be offset of the N between reference signal, may further comprise the steps: in a scan period, by being correlated with between received signal and the reference signal in a related interval, produce N and may be offset pairing correlated results separately, the corresponding skew of each related interval, phase of received signal does not have marked change in this related interval, and above-mentioned continuous relevant between, at least one parameter changes; A plurality of above-mentioned correlated results that respective offsets is arranged that in the continuous sweep cycle, add up, thus can be whether and side-play amount according to the existence of the correlated results judgement echo signal that adds up.

In a preferred embodiment of the method for the invention, the correlated results that all N between the received signal that adds up and the reference signal may skew place.Another preferred embodiment of this method, be in a scan period, determine N may skew place wherein L maximum correlated results, L is an integer less than N, above-mentioned L correlated results that is offset only adds up.Another one preferred embodiment on this basis is, in a scan period the possible side-play amount of N kind is divided into the L group, and wherein each group all comprises J side-play amount, and promptly L=N/J in a scan period, determines each maximum related value of organizing in this L group.The largest correlation result of each group in the above-mentioned L group that only adds up then.In superincumbent latter two preferred embodiment, the sign of each skew as location number, can be stored with the correlated results that adds up separately.

Whether and the method for PN code phase the present invention further content has provided a kind of existence that detects the echo signal in the received signal in cdma communication system.May further comprise the steps: the reference signal that is created in corresponding N different possible PN code phase in the N continuous related interval in scan period; In above-mentioned related interval, carry out relevantly with reference signal to received signal, produce correlated results separately; Whether and code phase the correlated results of at least a portion that adds up in the continuous sweep cycle, the existence of judging echo signal according to the correlated results that adds up.

In each scan period, the correlated results of all N related interval that can add up.Perhaps, only be accumulated in L interior correlated results of related interval that has maximum related value in the scan period, wherein L is an integer less than N, and the step of this method comprises: determine L correlation of above-mentioned maximum and the sign of an above-mentioned L related interval and correlated results are separately stored.On this basis, can further take following method: in a scan period, related interval is divided into the L group, wherein each group all comprises J related interval, wherein, L and J are integer, and L=N/J, and the correlated results of a related interval in J the related interval of each group that only adds up, thereby obtain maximum correlation value in the scan period, the method further may further comprise the steps: determines above-mentioned maximum correlation value and stores a sign, provide maximum correlation value in each J related interval organizing, and the correlated results that adds up separately.

The present invention also provides the signal searcher of Fig in a kind of CDMA (code division multiple access) communication system, and it comprises: a control unit; Reference signal generator by control unit control is used for producing the reference signal that a different N code phase was arranged in the N continuous related interval in the scan period; A correlator is used for to carrying out relevantly in the reference signal and the received signal of serial correlation at interval, and to produce corresponding correlated results, each related interval is enough lacked, thereby makes the phase place of received signal change not obvious in related interval; An accumulator, be used for response control unit, correlated results to each correlator of corresponding related intervals a large amount of in a large amount of scan periods adds up, and produces the correlated results that adds up separately, and whether and code phase the existence of echo signal in the judgement received signal.

In first preferred embodiment of the searcher of mentioning below, accumulator comprises the buffer of each correlated results that adds up of the above-mentioned N of a storage code phase.In second preferred embodiment, signal searcher of Fig comprises the decision unit of determining L maximum correlated results in N the code phase from a scan period, accumulator comprises a buffer and an auxiliary counter of indicating each code phase of storing each correlated results that adds up of L above-mentioned code phase, and wherein L is the integer less than N.

In the 3rd preferred embodiment, in each scan period, related interval comprises the L group, each group all comprises J related interval, wherein L and J are integers, and L=N/J, signal searcher of Fig also comprises a detector, be used for determining in a scan period in each group the largest correlation result in J the related interval, a counting is provided simultaneously, be used for indicating corresponding related interval in each group, wherein accumulator comprises a buffer, is used for storing in correlation computations result and the L group and counts accordingly in every group; A combiner is used at least one scan period subsequently the correlated results of the same code phase that above-mentioned counting indicated is added in the correlated results of respectively organizing pairing storage in the L group.At this moment, in each scan period subsequently, having only detector is in each group during the largest correlation result in J related interval at the correlated results of judging the same code phase that is indicated by above-mentioned counting, and combiner just can increase the correlated results of storage.

Signal searcher of Fig can comprise a decision unit, is used for judging one or more maximums in the correlated results that adds up, thereby whether has one or more echo signals and code phase thereof in the judgement received signal.

Compare with above-mentioned existing technology, the preferred embodiment of the present invention has bigger advantage.Concrete, the preferred embodiments of the present invention are easy to install, aspect input failure or the error probability bigger improvement is being arranged, and because the ability of stronger relatively opposing fading environment is arranged, thereby the detection that makes a plurality of echo signals becomes easy, as coming from the detection of the pilot signal of numerous base stations in the cdma cellular communication system.Simultaneously, describe below second and the 3rd preferred embodiment have reduced the requirement to memory, and this counts N at code phase particularly important meaning when very big.

Description of drawings

The present invention's description of middle example in conjunction with the accompanying drawings sharpens understanding.Wherein similar parts are represented by same reference number among each figure, wherein:

Fig. 1 is existing signal searcher of Fig structured flowchart;

Fig. 2 is the structured flowchart that is used in the existing correlator among Fig. 1;

Fig. 3 is the time-domain diagram of signal fadeout;

Fig. 4 is the time-domain diagram of illustrating the operating process of Fig. 1 signal searcher of Fig;

Fig. 5 is the structured flowchart according to the signal searcher of Fig of first preferred embodiment of the present invention;

Fig. 6 is the example of the serial buffer of signal searcher of Fig among Fig. 5;

Fig. 7 is the time-domain diagram of signal searcher of Fig operating process among Fig. 5;

Fig. 8 is the structured flowchart according to the signal searcher of Fig of second preferred embodiment of the present invention;

Fig. 9 is the buffer storage example of signal searcher of Fig among Fig. 8;

Figure 10 is the flow chart of Data Update algorithm;

Figure 11 and 12 is the Data Update figure that illustrate signal searcher of Fig operating process among Fig. 8;

Figure 13 is a signal searcher of Fig performance comparison diagram among Fig. 8 and Fig. 1;

Figure 14 is the structured flowchart according to the signal searcher of Fig of the 3rd preferred embodiment of the present invention;

Figure 15 is the serial buffer example of signal searcher of Fig among Figure 14;

Figure 16 is the maximum detector example of signal searcher of Fig among Figure 14;

Figure 17 is the comparison and the merge cells example of signal searcher of Fig among Figure 14;

Figure 18 is the flowchart illustration of signal searcher of Fig operating process among Figure 14.

Describe in detail

With reference to accompanying drawing, Fig. 1 has illustrated a kind of existing wideband signal searcher, for example detects as the signal in the cdma cellular communication system.This signal searcher of Fig comprises one with reference to 14, one decision units 16 of 12, one accumulators of 10, one correlators of PN signal generator and a timing control unit 18.

Signal searcher of Fig is used for the target RF signal of input 20 of detection correlator 12, and this RF signal has nominal carrier frequency f0, it comprise the I of quadrature in phase and Q road component and, I and Q road component are respectively by obtaining after spread spectrum PN sequence or PN sign indicating number PNI and the PNQ modulation.

In general, as described below, the PN code phase is as the timing parameters that carries out signal search.But, also can comprise other additional parameter, as frequency input signal f.In a word, in order to carry out signal search, must in hunting zone or uncertain zone, provide with the corresponding N of each parameter set skew, position or state (refering in particular to the balance of position); When a PN code phase search, each PN code phase values is corresponding with each position institute, and the distance between the PN code phase of adjacent position mostly is a basic symbol of this communication system, perhaps chip most in N position.Reference signal generator 10 produces PN sign indicating number sequence PNI and PNQ and reference frequency signal cos2 π f0t, and offers correlator 12, and wherein represented time of t is consistent with the commutator pulse that timing control unit 18 provides.

As shown in Figure 2, correlator 12 comprises

multiplier

22,24,26,28,30,32, quadrature phase shifter 34, low pass filter (LPF) 36 and 38, inverter 40, add up

combiner

42 and 44, squaring

cell

46 and 48 and combiner 50.Reference frequency signal cos2 π f0t follows the signal multiplication of the input 20 of multiplier 22 on the one hand, multiply each other through the input 20 of the value after phase shifter 34 phase shifts on the other hand with multiplier 24, after LPF 36 and 38 low-pass filtering are passed through in the output of these multipliers respectively, produce I road and Q road demodulated channel signal respectively.These channel signals are supplied with the first input end of multiplier 26,38 and the first input end of

multiplier

28,32 respectively; Second input of multiplier 26 is PN sign indicating number sequence PNI, and multiplier 28 and second input of 30 are PN sign indicating number sequence PNQ, and second input of multiplier 32 is through the PN sign indicating number sequence PNQ of inverter 40 after oppositely.

Multiplier 26 and 28 output merge through the combiner 42 that adds up, and add up, and the output of multiplier 26,28 merges through the combiner 44 that adds up, and adds up, and each the signal coherence interval T COH following produces correlation YI and YQ respectively.After these correlations pass through

squaring cell

46 and 48 squares respectively,, be that signal coherence interval T COH produces a relevant Y (Y=YI2+YQ2) of estimation through its square value of combiner 50 additions.

The relevant estimation Y of m continuous coherence interval is added to one in (incoherent) accumulator 14 (Fig. 1), produce accumulated value Z, be input in the decision unit 16, produce a court verdict that whether detects echo signal (for example can by relatively obtaining) with a threshold value at the output of signal searcher of Fig.If do not detect echo signal, the parameter of reference signal generator 10 should change to next position by the control of timing control unit 18, repeats above-mentioned search procedure.This process is carried out successively N position, produces continuous value Z1 to ZN, periodically repeats then, till detecting echo signal.

The curve 52 of Fig. 3 is indicated be the amplitude of echo signal under the fading environment with the functional relation between the time, time shaft is to be indicated by continuous signal coherence interval T COH, compares with fading rate, TCOH is very short.Use same time shaft size, what Fig. 4 represented is in total scan period NTA, the judgement Z1 in N continuous accumulation period, and Z2 ... in the time interval of ZN value, wherein each TA is corresponding to m continuous signal coherence interval TCOH.Fig. 4 is the situation of m=6.

A shortcoming of above-mentioned existing signal searcher of Fig and method is that the Z value separately of N position correspondence needs could determine through m continuous signal coherence interval.In fading environment, in the cdma cellular communication system, signal fadeout can badly influence judgement in the continuous like this time interval, cause the change at random (each position long-term average relatively) of decision value Z, thereby causes the increase of input failure or wrong possibility.For reducing this unfavorable factor, need to increase the value of m, this is with corresponding increase signal search time and scan period length.The result who causes like this is in the cdma cellular communication system, the increase of disturbing in the system, the growth of system turn-on time and the reduction of power system capacity.

The signal searcher of Fig of first preferred embodiment of the present invention is referring to Fig. 5, comprise: reference signal generator 10, correlator 12 (10 and 12 all can with above-mentioned), by the recirculation accumulator 60 that combiner 62 and serial buffer 64 are formed, decision unit 66 and timing control unit 68.Timing control unit 18 among Fig. 1 is that every m TCOH produces the parameter that an output pulse changes reference signal generator 10 at interval, and timing control unit 68 is different with it, each TCOH produces an output pulse at interval, each signal coherence all changes the parameter of reference signal generator at interval afterwards, thereby every N interval T COH finishes a scan period that covers all N position or state.The output pulse of timing control unit 68 is also imported C as the clock of serial buffer 64.

Relevant input estimating Y as combiner 62 corresponding to each signal coherence interval T COH of the output generation of correlator 12, and an output ZOUT of serial buffer 64 is as second input of combiner 62, combiner 62 adds two inputs together, at the output ZIN that bears results, as an input of serial buffer 64.Fig. 6 is a serial buffer 64, and it comprises that each relevant buffer status that adds up and be worth of N storage 701 forms to 70N, is serially connected with the form of shift register, is all imported the pulse timing of C by the supply clock in the TCOH gap periods.The output of the buffer level 70N at end constitutes the output ZOUT of serial buffer 64.

Fig. 7 can compare with above-mentioned Fig. 4, and it is the result treatment of the signal searcher of Fig of Fig. 5.Each scan period (total m), it is the duration of each NTCOH, also promptly form N signal coherence in the period at interval, reference signal generator 10 changes its all N position, content periodic shift in buffer of the level 70 of serial buffer 64, each corresponding each reference signal generator position moves into the current relevant estimation Y that accumulator 62 adds up.The initial value of the buffer stage 70 of serial buffer 64 can be made as 0, after m scan period m signal coherence value is at interval added up.Yet, Figure 7 shows that adding up just that judgement corresponding Z i (i=1 is to N) carried out to disjunct signal coherence interval, the influence of the signal fadeout shown in Fig. 3 is through on average being minimized like this.The correlation Zi that these add up is the serial output valve of the output ZOUT of serial buffer 64, decision unit 66 is determined one or more maximums in these accumulated values, and with a threshold value relatively after, whether and skew (code phase) existence that detects one or more target input signals.

The value of Zi (to suitable N value) also can with concurrently or string and the mode of combination from buffer 64, export supply decision unit 66, and be not only with serial mode.Further, the value of Zi can be upgraded at interval in real time repeatedly in N signal coherence of each scan period, rather than every N signal coherence forms a scan period at interval, and the search cycle carries out in the discontinuous combination of m scan period.Can balance by existing manner reduce the signal ZOUT that feeds back to combiner 62 this moment.In a word, can be by to the accumulated correlation values Zi of searcher output among Fig. 5 average, reduce the adverse effect that above-mentioned signal fadeout causes.

Signal searcher of Fig in second preferred embodiment of the present invention comprises reference signal generator 10, correlator 12 referring to Fig. 8, combiner 62 and timing control unit 68 (above 4 can with previously described identical), counter 72, buffer storage 74, data updating unit 76 and decision unit 78.As mentioned above, timing control unit 68 produces an output pulse at interval for each TCOH, change the parameter of reference signal generator after each such signal coherence interval, thereby every N TCOH finishes a scan period to all N position at interval.The input of C and counter 72 is also imported in the output of timing control unit 68 as a clock of data updating unit 76.Counter 72 is the modulo-N counters that these pulses are counted, and by its output that links to each other with data updating unit 76, provides a position counting i of current location in the expression scan period.

Buffer storage 74 sees Fig. 9 for details.Different with the above-mentioned serial buffer that the N level is arranged 64, usually buffer storage 74 comprises L the level 801 to 80L of negligible amounts, and each state has two to store territories, be used for storing L correlation Z1 to ZL and relevant position counting i1 to iL.Each storage territory of level 80 is at corresponding signal ZIN, iIN input and corresponding signal output ZOUT, connected in series mutually between the iOUT, and clock signal C 1 to the CL timing that provides by data updating unit 76 respectively, corresponding signal Z1 is offered data updating unit 76 to ZL.Signal ZOUT and iOUT from buffer storage 74 also supply with data updating unit 76, are 0 or the signal of correlation ZOUT thereby produce at following flow process 82 places.This signal at flow process 82 places is as second input of combiner 62, and first input of combiner 62 is above-mentioned current relevant estimation Y, and output has been formed the signal ZIN of buffer storage 74.The signal iIN that is input to buffer storage 74 is made up of the current position counting I of counter 72 outputs.Current relevant estimation Y also offers data updating unit 76.

As described below, the magnitude of numerical value L can be positional number N 1/5 or 1/10 on, the capacity of buffer storage 74 just is far smaller than the capacity of serial buffer 64 like this.This is significant when N is big.

The signal searcher of Fig course of work among Fig. 8 can be further with reference to the flow chart of Figure 10.It is made up of step 81 to 87, and in Figure 11 and 12 the Data Update block diagram, upper part and lower part are before representative data upgrades respectively and the content of the buffer-stored level after upgrading.

In step 81, data updating unit 76 is determined minimum value (but non-vanishing) Zn of the correlation of current storage in the buffer storage 74, and determines the position at its place.If have a plurality of equal minimum values, can use any one value and position thereof.This judgement also can be carried out in the TCOH interval, obtains current relevant estimation Y every interior during this time, because it is only relevant with the data of storage.

In step 82 subsequently, data updating unit 76 judgement current locations counting i whether equal buffer storage 74 outputs position iOUT (=iL).If be not equal to, for example in first scan period that comprises N position, whether data updating unit 76 is adjudicated current relevant estimation Y and is less than or equal to and is stored in the minimum value Zn that determines in the buffer storage 74 in step 83.If, then current location counting I is not carried out Data Update, withdraw from the flow chart among Figure 10.

If in step 83, determine Y＞Zn, execution in step 84 and 85 then, thus upgrade data in the buffer storage 74 according to Figure 11.For example during n=4, promptly Z4 is the minimum value that step 81 is determined.This moment, data updating unit 76 produced a zero-signal at flow process 82 places, thereby set by step shown in 84, the current relevant estimation Y of combiner 62 outputs is as correlation ZIN.Shown in step 85, this value and its position counting iIN=i exist in first level 801 of buffer storage, and the clock pulse C1 by separately of the level 801 to 80n-1 of buffer storage is displaced to state 802 to 80n to Cn.The previous content of buffer state memory 80n=804 is rewritten, and buffer storage level 80n+1 does not change to the content of 80L, and this is because do not generate clock pulse Cn+1 to CL.Like this, in first scan period of N signal coherence interval T COH, the relevant estimation Y of L maximum and position i separately thereof exist in L the level of buffer storage 74.

If determine in the step 82 current location i equal the output iOUT of buffer storage 74 (=iL), execution in step 86 and 87 is then upgraded the data of buffer storage 74 according to Figure 12.This moment, data updating unit 76 produced correlation ZOUT at flow process 82 places, thus 62 output correlation ZIN of combiner shown in 86 set by step, it be current relevant estimation Y and correlation ZOUT's and.Shown in step 87, by producing clock pulse C1 to CL, all levels of buffer storage are upgraded in displacement.This process operation gets up to be actually corresponding to the recirculation accumulator of correlation Z1 to ZL and their position i1 to iL that is stored in the buffer storage 74.

In each scan period, the parameter of reference signal generator 10 changes after through each TCOH interval, has to catch up with and states the same advantage aspect decline of first preferred embodiment.Through m the scan period of expectation, L position in N the position add up maximum related value and location number i thereof have been comprised in the buffer storage 74.As shown in Figure 8, buffer storage 74 serially or concurrently or string and in combination (similar) with previously described mode these accumulated correlation values Z1 is offered decision unit 78 to ZL and position i1 thereof to iL.Decision unit 78 is determined one or more maximums from these values, can be by comparing with a threshold value, whether and skew (code phase) existence that detects one or more target input signals delivers to output with correlation (if desired) and the positional information i that obtains simultaneously.

As mentioned above, in the signal searcher of Fig operation of Fig. 8, the serial correlation that adds up and store of each position correspondence is estimated by N signal correction interval T COH separately, has so just reduced the influence of decline.But because first scan period is used for determining the relevant position of adding up estimated, so increased the detection failed probability, this probability is with positional number N and to cushion the ratio of memory span L relevant.Figure 13 is the computer artificial result that this is carried out, and the detection probability of failure of rayleigh fading channel is with the functional relation of m when being N=675.Top curve 88 is performances of existing signal searcher of Fig among Fig. 1, and 3 following curves 90 are signal searcher of Fig improved performances in different L/N ratios among Fig. 8.Performance has bigger improvement aspect the probability of failure detecting for these curve shows, the signal searcher of Fig of Fig. 8, does not have bigger deterioration at L during greater than N/10, thereby can greatly reduce the capacity of buffer storage.

The signal searcher of Fig of the 3rd preferred embodiment of the present invention is referring to Figure 14, comprise reference signal generator 10, correlator 12, timing control unit 68, location counter 72 and decision unit, below all with the part of aforementioned correspondence, except the location counter 72 of this moment is that the counter (wherein J is an integer, will introduce in the back) of a mould J and the position of decision unit 78 are determined also to have done to change (will introduce in the back).As mentioned above, timing control unit 68 produces an output pulse at interval for each TCOH, changes the parameter of reference signal generator 10 in each back, such signal coherence interval.Location counter 72 is counted these pulses at clock pulse line C place, produces the output pulse at clock pulse line C1 place.These C1 pulses also can directly be provided by timing control unit 68.

The signal searcher of Fig of Figure 14 also comprises maximum detector 92 and recirculation accumulator 94.Recirculation accumulator 94 comprises that comparison merge cells 94 and serial buffer 96 form.As shown in figure 15, serial buffer 98 comprises L level 1001 to 100L, and each level all has two storage territories, be used for storing each correlation Z1 to ZL and accordingly position counting j1 to jL.The input ZIN in each storage territory of level 100, with output ZOUT, the mutual serial of jOUT links to each other jIN respectively, and by the clock signal timing on the clock pulse line C1.

When N was very big, the signal searcher of Fig among Figure 14 was useful especially, and for example N=32768, and needs detects a large amount of signals just can finish search, detects the pilot signal of several base stations as needs.Under latter instance, the PN code phase of different pilot signal is cut apart by the J in N the position; As J=64 in the Forward Pilot Channel in the IS-95 cellular communication system.Integer J, L, the pass of N is J=N/L, in the time of necessary, the value that can increase N guarantees that J and L are integer.

In the signal searcher of Fig of Figure 14, the input of maximum detector 92 has: the relevant estimation Y of each coherence interval TCOH of correlator 12 outputs, the position counting j of clock pulse C sum counter 72 outputs of timing control unit 68.The relevant of subclass of each J element of N searching position of maximum detector judgement estimated maximum among a Y YMAX value, and exports the value jMAX of this maximal correlation estimated value YMAX and position counting j thereof at output.

At last, as shown in figure 16, maximum detector comprises the memory cell 104 of 102, one relevant Y of estimation of storage of a comparator and the memory cell 106 of a storage relevant position j.Memory cell 106 needs the maximum J numbers of storage, needs less relatively bit number (as J=64, need 6 bits, and N=32768 needing 15 bits) with respect to N positional number of needs storage.The j1 of the L of serial buffer 98 level 100 also is the same to the quantity in jL territory, has reduced the memory span requirement to memory location count.

The input of comparator 102 is respectively the input and output of memory cell 104, the current content YMAX of each input relevant estimation Y and current memory cell 104 can be compared.If Y＞YMAX, the output of comparator starts the input E of memory cell 104 and 106, and the value of clock signal C as the input W of input value write, thereby in memory cell 104, store this bigger relevant estimation Y, its position counting of storage j in memory cell 106.Like this after the position subclass through J signal coherence interval T COH definition, the maximum YMAX value of storing and location number jMAX thereof (if desired, via among the figure not the clock buffer of demonstration) are offered the unit 96 of recirculation accumulator 94.

The signal YMAX and the jMAX of the output signal ZOUT of serial buffer 98 and jOUT and maximum detector 92 all offer unit 96, and Figure 17 is wherein a kind of mode.As described in Figure 17, unit 96 comprises

comparator

108 and 110, switch 112, combiner 114 and selector 116.Wherein the output signal ZIN of selector 116 and jIN are as the input of serial buffer 98.Figure 18 is unit 96 run chart, comprises step 121 cited below and 125.

Comparator 108 is relatively imported jMAX and jOUT position counting, if both equate that then off switch 112 in step 121 judgement, a relevant estimation YMAX input of device 114 as a comparison, another of 114 is input as correlation ZOUT.Combiner 114 is added to its input together, obtains an output Z1.Selector 116 selects Z1 or YMAX as signal ZIN under the control of the comparator 110 that compares YMAX and ZIN, selects jOUT or jMAX as signal jIN.If comparator 110 is not to judge YMAX＞Z1, the position of the switch of selector 116 is exactly the position shown in Figure 17 so.At this moment, shown in Figure 18 block diagram, the switch of selector 116 position shown in the figure, output ZIN=Z1=ZOUT+YMAX, and jIN=jOUT (also equaling jMAX).In a word, in the multiple scanning cycle, when maximal correlation estimates that YMAX occurs in the same position counting jMAX of same position subclass, with catching up with these the relevant estimations that add up of the similar mode of the mode of stating.

Be not equal to jOUT if judge jMAX in the step 121, then switch 112 keeps the state opened, combiner 114 output signal Z1=ZOUT.This moment, comparator 110 judged whether YMAX＞Z1 in step 123, if, then control selector 116 adopt with figure in the opposite position of the switch, shown in step 124, signal YMAX and jMAX are passed to output ZIN and jIN respectively.Otherwise comparator 112 control selectors 116 according to the position of the switch among the figure, shown in step 125 among Figure 18, are passed to output ZIN and jIN respectively with signal Z1=ZOUT and jOUt.

Through m above-mentioned scan period (each scan period includes N signal coherence interval T COH), the content serial of serial buffer 98 offer decision unit 78, determine one or more maximum ZI, wherein I is an integer from 1 to L, represent a position in the subclass of position, and corresponding with buffer status 100, and with ZI and threshold value comparison, whether judgement detects one or more signals.The code phase of the signal that each is such or position are J (I-1)+jI, and wherein jI is the peaked location number/value jOUT that rules out.

Although according to top description, each correlated results that is stored in the serial buffer 98 only just is increased when its location number jMAX is identical with the location number jOUT that stores, and is not limited only to this.On the contrary, as mentioned above, in first signal scan cycle of m signal scan cycle, maximum related value YMAX and its position jMAX can be by maximum detector 96 judgements, and in those scan periods subsequently, no matter whether the correlation Y of positional number jMAX be the largest correlation result of this group in this scan period in each group, can add up.But may cause the mis-behave of great detection probability, this is because the selection of maximum position is just based on first scan period in each subclass, does not have to utilize the reason that adds up.

Though physical equipment that above combination is detailed such as counter, comparators etc. have been described the preferred embodiments of the present invention, but can substitute this, if use one or more digital signal processors or application-specific integrated circuit (ASIC), the preferred embodiments of the present invention can easier execution.

Can make multiple modifications and changes in conjunction with the preferred embodiment of case description to the present invention, and without prejudice to the limited range of claims of the present invention.

Claims

1. signal search method, wherein, received signal is relevant with reference signal, and reference signal has at least a parameter to change, and produces between received signal and the reference signal corresponding to N the correlated results separately that may be offset, and comprises the steps:

In a scan period, by the correlation of received signal with reference signal with each skew that is in the related interval, draw the correlated results of corresponding N kind possibility side-play amount, the few of variation of the phase place of received signal in related interval, but at least a parameter can change in above-mentioned adjacent related interval;

Be accumulated in a plurality of above-mentioned relevant correlated results that the respective offsets amount was arranged in the continuous sweep cycle, whether and side-play amount the existence of judging echo signal according to the correlated results that adds up.

2. the method for claim 1, wherein be accumulated in all N between received signal and the reference signal may skew place correlated results.

3. the method for claim 1 may further comprise the steps: determine L maximum correlated results in a scan period from N possible skew, wherein L is an integer less than N, and described L correlated results that is offset wherein only adds up.

4. method as claimed in claim 3 and may further comprise the steps: store the flag information of each described L skew, and the correlated results that adds up separately.

5. method as claimed in claim 3 can be: the scope of N/L is approximately 5 to 10.

6. the method for claim 1, can may further comprise the steps: in a scan period, the maximum related value in the judgement L group in each group, each group all comprises J side-play amount in the possible side-play amount of N kind, L=N/J, every group maximum related value in the above-mentioned L group that wherein only adds up.

7. method as claimed in claim 6 can may further comprise the steps: store the flag information of maximum related value in above-mentioned every group and the correlated results that adds up thereof.

8. the method for claim 1 can may further comprise the steps: determine the accumulation result that at least one is maximum, whether and side-play amount the existence of judgement echo signal.

9. detect whether echo signal in the received signal of cdma communication system exists and the method for code phase, may further comprise the steps:

In N the serial correlation interval in a scan period, produce the reference signal of N possibility PN code phase:

In above-mentioned related interval, carry out relevantly with reference signal to received signal, produce each correlated results;

In the continuous sweep cycle, the correlated results of at least a portion that adds up; And

Whether the judgement echo signal exists and code phase from the correlated results that adds up.

10. method as claimed in claim 9, wherein, the correlated results of all N related interval of each scan period of adding up.

11. method as claimed in claim 9, wherein, the correlated results of L related interval of the interior correlation maximum of a scan period that only adds up, wherein L is the integer less than N, the method may further comprise the steps: determine above-mentioned maximum correlation value, store the flag information of an above-mentioned L related interval and the correlated results that adds up accordingly thereof.

12. method as claimed in claim 9, wherein, in each scan period, related interval comprises the L group, each group all comprises J related interval, L wherein, J is integer, and L=N/J, the correlated results of only getting a related interval in every group of J related interval adds up, produce a maximum correlation value in the scan period, the method further comprises the steps: to determine above-mentioned maximum correlation value, stores the flag information and the correlated results that adds up thereof that participate in this related interval of the above-mentioned maximum related value of composition in every group J the related interval.

13. a kind of signal searcher of Fig of code division multiple address communication system.Comprise:

Control unit;

Reference signal generator by control unit control, is used for producing the reference signal that is separated with a corresponding N different code phase between interior N serial correlation of a scan period;

Correlator, be used for to each serial correlation at interval in received signal and reference signal carry out relevantly, produce each correlated results, each related interval time is all enough short, makes the phase place of received signal change not obvious in so short related interval;

Accumulator, response control unit, in a large amount of scan periods, the correlated results of exporting for correlator corresponding to each related interval adds up, and produces each correlated results that adds up, and can determine that therefrom whether desired signal exists and code phase in the received signal.

14. method as claimed in claim 13, wherein, accumulator comprises a buffer, is used in the above-mentioned N code phase each all to store the correlated results that adds up.

15. signal searcher of Fig as claimed in claim 13 comprises the unit of L correlated results of a maximum in interior N the code phase of decision scan period, wherein accumulator comprises buffer, can all store a correlated results and discern the correlated count of each code phase of adding up for each of an above-mentioned L code phase, wherein L is an integer less than N.

16. signal searcher of Fig as claimed in claim 15, wherein N/L is on 5 to 10 these magnitudes.

17. signal searcher of Fig as claimed in claim 13, wherein, in each scan period, related interval comprises L group, wherein each group all comprises J related interval, L wherein, J is integer, and L=N/J, this signal searcher of Fig further comprises a detector, in a scan period, adjudicate every group of largest correlation result that J related interval is interior in the scan period, and the count flag of corresponding related interval in each group is provided.Wherein, accumulator comprises a buffer, is used for storing counting of respectively organizing in the L group of correlated results and correspondence thereof; Combiner is used for the correlated results of the same code phase at least one follow-up scan period above-mentioned count flag indicated and is added in the L group of storage in every group of pairing correlated results.

18. signal searcher of Fig as claimed in claim 17, have only wherein that to judge the correlated results of the same code phase that above-mentioned counting is indicated when detector be when respectively organizing the largest correlation result of J related interval, combiner just can increase the correlated results of storage in each follow-up scan period.

19. signal searcher of Fig as claimed in claim 17, wherein N=32768 and J=64.

20. signal searcher of Fig as claimed in claim 13 can comprise a decision unit, the result of one or more maximums in the correlated results that is used for determining to add up, thus judge that whether one or more echo signals exist and code phase in the received signal.

21. the signal searcher of Fig of a code division multiple address communication system, comprise with lower device, produce the device of at least one reference signal, the device of marked change does not take place in the phase place of in each enough short related interval thereby reference signal and received signal being carried out relevant received signal in related interval, be the add up device of correlated results of the same code phase of a plurality of above-mentioned related intervals, whether exist and the device of code phase according to one or more echo signals in the correlated results that the adds up judgement received signal, it is characterized in that, in forming a N serial correlation N at interval possible code phase scope of a signal scan cycle, change the control device of reference signal code phase, correlated results is stored to add up in a plurality of signal scan cycle.