CN1254927C

CN1254927C - Methods and appts. for signal searching using correlation

Info

Publication number: CN1254927C
Application number: CNB998170917A
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; Nortel Networks Corp
Priority date: 1999-12-17
Filing date: 1999-12-17
Publication date: 2006-05-03
Anticipated expiration: 2019-12-17
Also published as: CA2394510A1; WO2001045288A1; KR20020055451A; CN1398460A; JP2003517247A; AU3338800A

Abstract

The present invention relates to a signal searcher of a CDMA communication system, which comprises a reference signal generator and a correlator, wherein the correlator correlates a received signal with the reference signal thereof in a short correlation interval (the signals are coherent), and the code phase of the reference signal changes in N possible code phase ranges at N continuously correlated intervals so as to form a signal scanning period. An accumulator and a buffer are used for accumulating the correlation result of the same code phase based on a large quantity of the correlated intervals in the continuous signal scanning period; according to the accumulated correlation results, a judgment unit can judges the existence and the phase of at least one target signal of the received signals. One preferable embodiment of the present invention is formed by that all the correlation results are accumulated, and other preferable embodiments are formed by that only relatively large values of the correlation results are accumulated so as to reduce the requirement of memories.

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.

Background technology

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 Fading Envioment " literary composition of Manabu Mukai and Mutsumu Serizawa, accumulation interval T _ABe divided into a large amount of m continuous short interval T _COH, make T _A=mT _COHEach T _COHEnough weak points of duration choosing at interval, signal phase be during this time every interior no significant change, thereby can be used as signal coherence at interval.At accumulation interval T _AIn, 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.Though can take to increase the time T that adds up _AAlleviate its influence, but 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 has 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: at an accumulation interval T _A=mT _COHIn, signal coherence interval T in continuous adjacent _COHInterior m relevant estimation adds up.In frequency is that the signal bandwidth of 800MHz is in the IS-95CDMA 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, at accumulation interval T _AIn, 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.

Embodiment

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 spread spectrum PN sequence or PN sign indicating number PN _IAnd PN _QObtain after the 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 PN _IAnd PN _QAnd reference frequency signal cos2 π f0t, and offer correlator 12, 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 PN _I, multiplier 28 and second input of 30 are PN sign indicating number sequence PN _Q, second input of multiplier 32 is through the inverter 40 PN sign indicating number sequence PN after oppositely _I

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 42 that adds up, and adds up, in each following signal coherence interval T _COH, produce correlation Y respectively _IAnd Y _QThese correlations through its square value of combiner 50 additions, are the signal coherence interval T after passing through

squaring cell

46 and 48 squares respectively _COHProduce the relevant Y of an estimation (Y=Y _I2+ Y _Q2).

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 Z ₁To Z _N, periodically repeat 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 by continuous signal coherence interval T _COHIndicate, compare T with fading rate _COHVery short.Use same time shaft size, what Fig. 4 represented is at total scan period NT _AIn, the judgement Z in N continuous accumulation period ₁, Z ₂... Z _NThe time interval of value, wherein each T _ACorresponding to m continuous signal coherence interval T _COHFig. 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, disturb to increase the growth of system turn-on time and the reduction of power system capacity in the system.

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 every m T _COHProduce the parameter that an output pulse changes reference signal generator 10 at interval, and timing control unit 68 is different with it, each T _COHProduce an output pulse at interval, each signal coherence all changes the parameter of reference signal generator at interval afterwards, thus every N interval T _COHFinish 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.

The output of correlator 12 produce corresponding to each signal coherence interval T _COHRelevant estimation Y as an input of combiner 62, an and output Z of serial buffer 64 _OUTAs second input of combiner 62, combiner 62 adds two inputs together, at the output Z that bears results _IN, 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, all at T _COHGap periods is by the pulse timing of supplying with clock input C.The output of the buffer level 70N at end constitutes the output Z of serial buffer 64 _OUT

Fig. 7 can compare with above-mentioned Fig. 4, and it is the result treatment of the signal searcher of Fig of Fig. 5.At each scan period (total m), i.e. each NT _COHDuration, 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 the judgement corresponding Z _iWhat (i=1 is to N) carried out adds up just to disjunct signal coherence at interval, and the influence of the signal fadeout shown in Fig. 3 is through on average being minimized like this.The correlation Z that these add up _iBe the output Z of serial buffer 64 _OUTThe serial output valve, decision unit 66 is determined one or more maximums in these accumulated values, and with a threshold value relatively after, whether and be offset (code phase) existence that detects one or heterogeneous target input signal.

Z _iValue (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, Z _iValue can upgrade repeatedly in real time at interval in N signal coherence of each scan period, rather than every N signal coherence forms a scan period at interval, the search cycle carries out in the discontinuous combination of m scan period.Can balance by existing manner reduce the signal Z that feeds back to combiner 62 this moment _OUTIn a word, can be by accumulated correlation values Z to searcher output among Fig. 5 _iAverage, 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 is each T _COHProduce an output pulse at interval, after each such signal coherence interval, change the parameter of reference signal generator, thereby every N is a T _COHFinish a scan period at interval all N position.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, buffer storage 74 comprises L the level 801 to 80L of negligible amounts usually, and each state has two storage territories, is used for storing L correlation Z ₁To Z _LWith relevant position counting i ₁To i _LEach storage territory of level 80 is at corresponding signal Z _IN, i _INInput and corresponding signal output Z _OUT, i _OUTBetween connected in series mutually, and the clock signal C that provides by data updating unit 76 respectively ₁To C _LTiming is corresponding signal Z ₁To Z _LOffer data updating unit 76.Signal Z from buffer storage 74 _OUTAnd i _OUTAlso supplying with data updating unit 76, is 0 or correlation Z thereby produce at following flow process 82 places _OUTSignal.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 Z of buffer storage 74 _INBe input to the signal i of buffer storage 74 _INCurrent position counting I by counter 72 outputs is formed.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) Z of the correlation of current storage in the buffer storage 74 _N, and the position at definite its place.If have a plurality of equal minimum values, can use any one value and position thereof.This judgement also can be at T _COHCarry out at interval, obtain current relevant estimation Y every interior during this time, because it is only relevant with the data of storage.

In step 82 subsequently, whether data updating unit 76 judgement current location counting i equal the position i of buffer storage 74 outputs _OUT(=i _L).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 Z that determines in the buffer storage 74 in step 83 _NIf, 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＞Z _N, execution in step 84 and 85 then, thus data in the buffer storage 74 upgraded according to Figure 11.For example during n=4, i.e. Z ₄It 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 Z _INShown in step 85, this value and its position counting i _IN=i exists in first level 801 of buffer storage, and the level 801 to 80n-1 of buffer storage by separately clock pulse C ₁To C _nBe displaced to state 802 to 80n.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 C _N+1To C _LLike this, N signal coherence interval T _COHFirst scan period in, L maximum relevant estimation Y and position i separately thereof exist in L grade of buffer storage 74.

If determine in the step 82 that current location i equals the output i of buffer storage 74 _OUT(=i _L), 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 Z at flow process 82 places _OUTThereby combiner shown in 86 62 is exported correlation Z set by step _IN, it is current relevant estimation Y and correlation Z _OUTAnd.Shown in step 87, by producing clock pulse C ₁To C _L, all levels of buffer storage are upgraded in displacement.It is individual corresponding to the correlation Z that is stored in the buffer storage 74 that this process operation gets up to be actually ₁To Z _LWith their position i ₁To i _LThe recirculation accumulator.

In each scan period, the parameter of reference signal generator 10 is at each T of process _COHChange at interval, have to catch up with and state 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 Z ₁To Z _LAnd position i ₁To i _LOffer decision unit 78.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 _COHSeparately, 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 is each T _COHProduce an output pulse at interval, change 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, at clock pulse line C ₁The place produces the output pulse.These C ₁Pulse 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, is used for storing each correlation Z ₁To Z _LAnd corresponding position counting j ₁To j _LThe input Z in each storage territory of level 100 _IN, j _INRespectively with output Z _OUT, j _OUTSerial links to each other mutually, and by clock pulse line C ₁On the clock signal timing.

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: each coherence interval T of correlator 12 outputs _COHRelevant estimation Y, the position counting j of clock pulse C sum counter 72 output of timing control unit 68.A maximum Y among the relevant estimation Y of the subclass of each J element of N searching position of maximum detector judgement _MAXBe worth, and export this maximal correlation estimated value Y at output _MAXAnd the value j of position counting j _MAX

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 j of the L of serial buffer 98 level 100 ₁To j _LThe quantity in individual territory also is the same, 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, can be with the relevant current content Y that estimates Y and current memory cell 104 of each input _MAXCompare.If Y＞Y _MAX, 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 stores this bigger relevant estimation Y in memory cell 104, its position counting of storage j in memory cell 106.Like this through J signal coherence interval T _COHAfter the position subclass of definition, the maximum Y of storage _MAXValue and location number j thereof _MAX(if desired, via the clock buffer that does not show among the figure) offers the unit 96 of recirculation accumulator 94.

The output signal Z of serial buffer 98 _0UTAnd j _OUTAnd the signal Y of maximum detector 92 _MAXAnd j _MAXAll offer unit 96, 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.The output signal Z of selector 116 wherein _INAnd j _INInput as serial buffer 98.Figure 18 is unit 96 run chart, comprises step 121 cited below and 125.

Comparator 108 is relatively imported j _MAXAnd j _OUTPosition counting is if both equate that then off switch 112 in step 121 judgement, relevant estimation Y _MAXDevice 114 input as a comparison, another of 114 is input as correlation Z _OUTCombiner 114 is added to its input together, obtains an output Z ₁Selector 116 is comparing Y _MAXAnd Z _INThe control of comparator 110 under, select Z ₁Or Y _MAXAs signal Z _IN, select j _OUTOr j _MAXAs signal j _INIf comparator 110 is not to judge Y _MAX＞Z ₁, 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 Z _IN=Z ₁=Z _OUT+ Y _MAX, and j _IN=j _OUT(also equal j _MAX).In a word, in the multiple scanning cycle, when maximal correlation is estimated Y _MAXOccur in the same position counting j of same position subclass _MAXThe time, add up with catching up with the similar mode of the mode of stating that these relevant are estimated.

If judge j in the step 121 _MAXBe not equal to j _OUT, then switch 112 keeps the state opened, combiner 114 output signal Z ₁=Z _OUTThis moment, comparator 110 judged whether Y in step 123 _MAX＞Z ₁, if, then control selector 116 adopt with figure in the opposite position of the switch, shown in step 124, with signal Y _MAXAnd j _MAXPass to output Z respectively _INAnd j _INOtherwise comparator 112 control selectors 116 are according to the position of the switch among the figure, shown in step 125 among Figure 18, with signal Z ₁=Z _OUTAnd j _OUtPass to output Z respectively _INAnd j _IN

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

Although according to top description, be stored in each correlated results in the serial buffer 98 only at its location number j _MAXLocation number j with storage _OUTJust be increased when identical, but be not limited only to this.On the contrary, as mentioned above, in each signal scan cycle of m signal scan cycle, maximum related value Y _MAXWith its position j _MAXCan adjudicate by maximum detector 96, and in those scan periods subsequently, positional number j in each group _MAXCorrelation Y, no matter whether be the largest correlation result of this group in this scan period, 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 that is used for code division multiple address communication system, wherein, received signal is relevant with reference signal, and reference signal has at least a parameter to change, so that be the corresponding correlated results of difference skew generation in individual may the skew of N between received signal and the reference signal, wherein N is a positive integer, comprises the steps:

In a scan period, according to being correlated with between reference signal that in each related interval, has a respective offsets and the received signal, for each skew in may being offset of N kind produces corresponding correlated results, the phase place of received signal does not produce great changes in described related interval, and described at least one parameter changes between continuous described being correlated with; And

In an independent accumulator, be a plurality of described relevant correlated results that adds up in the continuous sweep cycle, make it possible to judge signal that whether has hope and the skew of determining this signal according to the correlated results that adds up with respective offsets.

2. the method for claim 1, wherein may be offset the correlated results that adds up for all N between received signal and the reference signal.

3. the method for claim 1 may further comprise the steps: in a scan period, for N in may being offset L may be offset definite largest correlation result, wherein L is an integer less than N, wherein only is offset the correlated results that adds up for described L.

4. method as claimed in claim 3 may further comprise the steps: store the sign of described L each skew in the skew explicitly with the correlated results that adds up accordingly.

5. method as claimed in claim 3, wherein 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, determine the largest correlation result in each group in the L group, each group all comprises N J skew in may being offset, L=N/J wherein only is the correlated results that adds up of each group in the described L group.

7. method as claimed in claim 6 can may further comprise the steps: correlated results is stored the sign of each largest correlation result in the described largest correlation result explicitly with adding up accordingly.

8. the method for claim 1 can may further comprise the steps: determine the correlated results that adds up of a maximum at least, so that judge signal that whether has hope and the skew of determining this signal.

9. whether there is the method for signal with the PN code phase that detects this signal of hope in the received signal of detection cdma communication system, may further comprise the steps:

Be created in the reference signal that has N the difference possibility PN code phase in the possibility PN code phase in the serial correlation interval in inherent N the related interval of a scan period;

In described related interval, received signal and reference signal are carried out relevant so that produce corresponding correlated results;

In an independent accumulator, be at least some correlated results in the described correlated results of continuous sweep periodic accumulation; And

Judge signal that whether has hope and the skew of determining this signal according to the correlated results that adds up.

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

11. method as claimed in claim 9, it wherein only is L related interval having maximal correlation in the scan period correlated results that adds up, wherein L is the integer less than N, this method may further comprise the steps: determine the relevant of described maximum, and store the sign of each related interval in the described L related interval explicitly with the correlated results that adds up accordingly.

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, and wherein only be the related interval of one in every group of J related interval generation maximal correlation in the scan period correlated results that adds up, this method also comprises the steps: to determine described maximal correlation, and is stored in the sign that has each related interval of described maximal correlation in each group that comprises J related interval explicitly with the correlated results that adds up accordingly.

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

Timing control unit;

Reference signal generator by timing control unit control, is used for being created in the reference signal that has N the different code phases in the code phase in each related interval in N the serial correlation interval in the scan period;

Correlator is used for carrying out relevantly to each serial correlation received signal and reference signal at interval, so that produce each correlated results, each related interval is all enough short, and great changes will take place in this related interval to make the phase place of received signal; With

An independent accumulator, in response to timing control unit, be used to each related interval in a plurality of related intervals in a plurality of scan periods to add up the correlated results of autocorrelator, so that produce the correlated results that adds up accordingly, can judge signal that in received signal, whether has hope and the code phase of determining this signal according to this correlated results that adds up

A decision unit is used for determining maximum one or more correlated results that add up, thereby judges signal that whether has one or more hope in received signal and the code phase of determining this signal.

14. signal searcher of Fig as claimed in claim 13, wherein accumulator comprises a buffer, is used to each code phase in the described N code phase all to store the correlated results that adds up.

15. signal searcher of Fig as claimed in claim 13, be included in the unit of determining largest correlation result in the scan period for L code phase in N the code phase, wherein accumulator comprises buffer, be used to each code phase in the above-mentioned L code phase all to store a correlated count that adds up correlated results and identify each code phase, wherein L is an integer less than N.

16. signal searcher of Fig as claimed in claim 15, wherein the scope of N/L is about 5 to 10.

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 also comprises a detector, is used to each group that comprises J related interval in the scan period to determine largest correlation result, and the counting of corresponding related interval in each group of sign is provided, wherein accumulator comprises a buffer, is used to each group storage correlated results in L the group and the counting that is associated thereof; And combiner, be used for will adding the correlated results of the same code phase of representing with described counting for the correlated results of each the group storage in L the group at least one follow-up scan period.

18. signal searcher of Fig as claimed in claim 17, wherein have only when detector judges that correlated results by the same code phase of described counting sign is a largest correlation result for each group that comprises J related interval, combiner just increases the correlated results of storing in the corresponding follow-up scan period.

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