CN1235364C - A multipath search method and apparatus using two layer filtration process - Google Patents
A multipath search method and apparatus using two layer filtration process Download PDFInfo
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Abstract
According to a multi-path searching method of the present invention, a communication system receiver obtains an I branch signal and a Q branch signal on each sampling phase through de-spreading and descrambling processing to a base band signal. The communication system receiver obtains a multi-path position according to the following steps: (1) the values of the I branch signal and the Q branch signal on each sampling phase which can be used as a low-pass filter respectively complete signal processing including the low-pass filter according to branches; (2) square summation operation is carried out to the I branch signal value and the Q branch signal value on each sampling phase, which are processed or are not processed through the step (1), to obtain a signal energy value on each sampling phase; (3) the signal energy value on each sampling phase completes the signal processing including the low-pass filter; (4) whether the phase is a multi-path position or not is determined according to the signal energy value on each sampling phase, which is processed through the step (3). The present invention effectively removes low frequency components in a Gaussian noise power spectrum through the two-layer processing of the low pass filter.
Description
Technical field
The present invention relates to method for receiving and processing signal and device in code division multiple access (CDMA) communication system, particularly adopt the multipath searching method and the device of two-layer Filtering Processing in the cdma receiver system.
Background technology
Compare with wire message way, wireless channel environment is comparatively abominable, have many interference such as decline, multipath, so the whether suitable of the method for receiving and processing signal of wireless communication system is the decisive factor that influences systematic function always.
So-called multipath transport phenomena, refer to from the signal of transmitter emission and arrive receiver through the different transmission path of too much bar, therefore receiver will receive the transmission signals of the mulitpath that decline degree and phase place do not wait with different time-delays, and these multipath signals can cause the multipath fading phenomenon when mixing arrival receivers.Fig. 1 and Fig. 2 show under ideal situation and the actual conditions time-delay power spectrum from a certain transmitter received signal respectively, transverse axis among the figure is represented the time that signal receives, vertical pivot is represented the energy or the power of received signal, time and power that each arrow 101～106 expression multipath signals occur on receiver.In real system, because the combined influence of factors such as the non-synchronous fully and noise of the imperfection of code length, sign indicating number, system, multipath signal is not as shown in Figure 1 discrete type vertical line on the power spectrum in time-delay, but the time dependent full curve of energy as shown in Figure 2.Still be formed with signal peak among Fig. 2 with near Fig. 1 corresponding peak value position, but the position is not accurate correspondence, and, then almost can't distinguishes for 104 and 106 two less peaks of energy.In addition, on 20 positions that indicate a false multipath signal that is caused by the higher noise energy appears also.
Although there are various noise jamming in the multipath signal of actual reception, still comprised utilizable information, therefore for example in cdma system, receiver can be by merging the signal to noise ratio that multipath signal improve received signal.The general RAKE reception technique that adopts in cdma receiver carries out diversity and merges to obtain better receptivity the multipath signal interval greater than a chip.RAKE receiver generally is made up of Multipath searching unit, despreading descrambling unit/unit group, channel estimating and compensating unit and multipath merge cells.The Multipath searching unit is used for determining to belong to from the baseband signal of input the relative time position or the phase place of each multipath signal of same transmitter or user, on the multi-path location that despreading descrambling unit/unit group is then determined in the Multipath searching unit signal is carried out the despreading scramble process to obtain each multipath signal.Because the decline degree and the phase place of each road multipath signal do not wait, therefore need they to be carried out signal compensation and correction by channel estimating and compensating unit.At last, the multipath merge cells merges each multipath signal through overcompensation to obtain to have the signal than high s/n ratio.
Above-mentioned Multipath searching unit in fact also is the synchronous basis of cdma system dedicated channel demodulation.Generally speaking, system adopts the two-stage method of synchronization, promptly at first carry out Multipath searching, each bar multipath signal in obtaining on a large scale, carry out multipath tracking then and handle, Multipath searching is handled the rough position that obtains adjust to determine accurate multi-path location and to overcome possible the moving of multipath peak position in the cycle of a Multipath searching.Therefore, Multipath searching is actually a kind of thick simultaneous techniques that obtains the multipath home position in big time range.
The general structure of Multipath searching unit as shown in Figure 3.In the Multipath searching unit, at first according to certain condition code baseband signal is carried out the despreading scramble process, thereby obtain the time-delay power spectrum of the despreading descrambling output energy of relative users on different time position (or phase place) by despreading descrambling unit/unit group 31.Phase place smooth unit 32 is carried out smoothing processing to suppress the time-delay power spectrum behind the noise to the multipath signal on each phase place.Peak filter 33 detects peak and the corresponding energy through the time-delay power spectrum after the inhibition noise processed, and exports testing result to multi-path judging unit/unit group 34.34 of multi-path judging unit/unit group determine according to predefined decision rule whether detected peak position is the multi-path location of signal, if be defined as multi-path location, then export the phase information of this multi-path location, but also transmit control signal to despreading descrambling unit/unit group 31.In above-mentioned Multipath searching unit, despreading descrambling unit/unit group 31 is with the fast speeds processing signals, can be described as the front-end processing part, phase place smooth unit 32, peak filter 33 and multi-path judging unit/unit group 34 can be described as the back-end processing part with symbol level (perhaps slower speed step) velocity process signal.
The major function of phase place smooth unit 32 be suppress ubiquitous noise to multi-path judging cause influence and sudden big noise had restriction, the general linear filter that adopts is realized for example finite impulse response (FIR) filter or infinite impulse response (IIR) filter.The most frequently used is the first order IIR filtering device, and its structure as shown in Figure 4.In this filter, finish the product calculation of intake and filter coefficient α by multiplier 71, carry out delay process and delay process result and coefficient (1-α) multiplied each other by 73 pairs of delay registers output energy by multiplier 72, by adder 74 with the output results added of multiplier 71 and 72 as exporting energy.The value of filter coefficient α has determined the performance of this filter, if factor alpha is bigger, then whole system is more stable, and false alarm probability (be about to non-multipath signal erroneous judgement and be the probability of multipath signal) is lower, but the multipath searching time is also longer; If side reaction coefficient is less, then system response is relatively sensitiveer, and the multipath searching time is also short, but erroneous judgement appears in false alarm probability also corresponding increase easily.
Multi-path judging unit/unit group 34 can adopt various decision rules to determine whether the peak position of peak filter output is multi-path location.The simplest a kind of decision rule is, if peak energy, determines then that this peak position is a multi-path location greater than predetermined threshold value T.Obviously, the size of threshold value T has determined the reliability of judgement.If T is bigger, then false alarm probability is less, but false dismissal probability (be about to the multipath signal erroneous judgement and be the probability of non-multipath signal) is bigger; Otherwise if T is bigger, then false dismissal probability is less, but false alarm probability is bigger.
In the conventional system under the prior art,, before multi-path judging, the power on the corresponding phase of time-delay power spectrum in the different search cycles is carried out infinite impulse response (IIR) Filtering Processing in order to suppress noise.But because power calculation must relate to nonlinear square operation, thereby the noise on the feasible time-delay power spectrum is rendered as nonwhite noise form as shown in Figure 5.In typical Gaussian noise power spectrum shown in Figure 5, contain a large amount of low frequency components, though therefore can effectively suppress high-frequency noise by low-pass filtering, limited to the inhibitory action of low-frequency noise.
Summary of the invention
The purpose of this invention is to provide a kind of multipath searching method and device, it can effectively suppress the low frequency component in the Gaussian noise power spectrum, thereby improves the signal to noise ratio of received signal, detects the less multi-path location of signal-to-jamming ratio.
Goal of the invention of the present invention is by wherein a kind of technical scheme realization, at the multipath searching method that is used for code division multiple address communication system according to this scheme, receiver in the described communication system obtains I branch road and Q tributary signal on each sampling phase by the despreading scramble process to baseband signal, and described receiver obtains multi-path location according to following steps:
(1) judges whether I branch road and Q tributary signal on the sampling phase can do low-pass filtering treatment, and I branch road on the sampling phase that can make low-pass filtering treatment and Q tributary signal value are finished signal processing by branch road respectively, and described signal processing comprises low-pass filtering; The signal that can not make low-pass filtering treatment is entered next step;
(2) will carry out square summation operation to obtain the signal energy value on each sampling phase through step (1) processing with without I tributary signal value and Q tributary signal value on each sampling phase of step (1) processing;
(3) the signal energy value on each sampling phase is finished signal processing, described signal processing comprises low-pass filtering; And
(4) according to determining through the signal energy value after step (3) processing whether this phase place is multi-path location on each sampling phase.
Relatively goodly be, in above-mentioned multipath searching method, the signal processing of described step (1) further comprises: will be obtained new I tributary signal value and Q tributary signal value mutually with corresponding previous I branch road cumulative signal value and previous Q branch road cumulative signal value through the I branch road of low-pass filtering treatment respectively with Q tributary signal value on each sampling phase, wherein previous I branch road cumulative signal value and previous Q branch road cumulative signal value are respectively on this sampling phase the accumulated value of the I tributary signal value of process low-pass filtering treatment and the accumulated value of Q tributary signal value before current tributary signal.
Reasonablely be, in above-mentioned multipath searching method, the signal processing of described step (3) further comprises: the signal energy value on each sampling phase that before the low-pass filtering treatment step (2) is obtained is obtained new signal energy value mutually with corresponding previous signal energy accumulated value, and wherein previous signal energy accumulated value is the accumulated value that passed through the signal energy value of low-pass filtering treatment on this sampling phase before current tributary signal.
The situation that belongs to the signal that transmits in the WCDMA system uplink physics Dedicated Control Channel for baseband signal, according to the method described above, reasonablely be, the I branch road and the Q tributary signal value that in step (1) sampling phase are arranged in the time slot pilot portion are finished signal processing by branch road respectively, and described signal processing comprises low-pass filtering; And I branch road and Q tributary signal value that sampling phase is arranged in outside the time slot pilot portion are not made low-pass filtering treatment.
During the signal that in baseband signal belongs to WCDMA system uplink physics Dedicated Control Channel, transmits, in said method, be more preferably, in step (1), adopt the single order IIR filter that I branch road and Q tributary signal value that sampling phase is arranged in the time slot pilot portion are carried out low-pass filtering treatment, if and sampling phase is arranged in time slot pilot portion start element place, then the single order IIR filter adopts less filter parameter to improve process sensitivity, if sampling phase is arranged in the non-start element of time slot pilot portion place, then the single order IIR filter adopts bigger filter parameter to improve Treatment Stability.
Goal of the invention of the present invention realizes by another technical scheme, the multipath searching device that is used for code division multiple address communication system according to this scheme is made up of front-end processing unit and back-end processing unit, described front-end processing unit obtains I branch road and Q tributary signal on each sampling phase by despreading scramble process baseband receiving signals, multi-path location is determined according to I branch road on the sampling phase and Q tributary signal in described back-end processing unit, and described back-end processing unit comprises:
The ground floor low-pass filter unit is used for the I branch road on the sampling phase of the low-pass filtering treatment done of front-end processing unit output and Q tributary signal value finished by branch road respectively and comprises low-pass filtering in interior signal processing, and described signal processing comprises low-pass filtering;
The input data selection unit, the signal that can do on the sampling phase of low-pass filtering treatment is sent into energy calculation unit after the ground floor low-pass filter unit is handled, and the signal that can not do on the sampling phase of low-pass filtering treatment is directly sent into energy calculation unit;
Energy calculation unit is used for and will handles through the ground floor filter unit and carry out square summation operation to obtain the signal energy value on each sampling phase without I tributary signal value and Q tributary signal value on each sampling phase of ground floor low-pass filter unit processing;
Second layer low-pass filter unit is used for the signal energy value on each sampling phase of energy calculation unit output is finished the time-delay power spectrum of low-pass filtering treatment to obtain to constitute by through signal energy value on each phase place after the low-pass filtering;
The peak filtering unit, the phase place and the energy value of each peak position of time-delay power spectrum that is used for determining that described second layer low-pass filter unit obtains; And
The multi-path judging unit is used for judging according to each peak position energy value of certain decision rule and the output of described peak filtering unit whether this peak position is multi-path location and exports judged result.
In above-mentioned multipath searching device, reasonablely be, described ground floor low-pass filter unit further comprises relevant accumulator module, be used for and will be obtained new I tributary signal value and Q tributary signal value mutually with corresponding previous I branch road cumulative signal value and previous Q branch road cumulative signal value through the I branch road of low-pass filtering treatment respectively with Q tributary signal value on each sampling phase, wherein previous I branch road cumulative signal value and previous Q branch road cumulative signal value are respectively on this sampling phase the accumulated value of the I tributary signal value of process low-pass filtering treatment and the accumulated value of Q tributary signal value before current tributary signal.
In above-mentioned multipath searching device, reasonablely be, described second layer low-pass filter unit further comprises the irrelevant unit that adds up, the signal energy value that is used on each sampling phase that before the low-pass filtering treatment energy calculation unit is obtained is obtained new signal energy value mutually with corresponding previous signal energy accumulated value, and wherein previous signal energy accumulated value is the accumulated value that passed through the signal energy value of low-pass filtering on this sampling phase before current tributary signal.
The situation that belongs to the signal that transmits in the WCDMA system uplink physics Dedicated Control Channel for baseband signal, in above-mentioned multipath searching device, reasonablely be, in the ground floor low-pass filter unit to sampling phase be arranged in the I branch road of time slot pilot portion and Q tributary signal value respectively by branch road finish comprise low-pass filtering signal processing and I branch road and Q tributary signal value that sampling phase is arranged in outside the time slot pilot portion are not made low-pass filtering treatment.
During the signal that in baseband signal belongs to WCDMA system uplink physics Dedicated Control Channel, transmits, in above-mentioned multipath searching device, be more preferably, the ground floor low-pass filter unit comprises the single order IIR filter and carries out low-pass filtering treatment with the I branch road and the Q tributary signal value that sampling phase are arranged in the time slot pilot portion, if and sampling phase is arranged in time slot pilot portion start element place, then the single order IIR filter adopts less filter parameter to improve process sensitivity, if sampling phase is arranged in the non-start element of time slot pilot portion place, then the single order IIR filter adopts bigger filter parameter to improve Treatment Stability.
In above-mentioned multipath searching method or device, can make I branch road on the sampling phase of low-pass filtering treatment and Q tributary signal and include but not limited to that known symbol maybe can adjudicate the signal of symbol.
In method and apparatus of the present invention, can effectively remove low frequency component in the Gaussian noise power spectrum by two-layer low-pass filtering treatment, improve the signal to noise ratio of received signal, thereby can detect the littler multi-path location of signal-to-jamming ratio.And above-mentioned two-layer low-pass filtering treatment do not increase considerably the complexity and the overhead of multipath searching device, so implementation is easy and economical.
Description of drawings
Fig. 1 is the time-delay power spectrum of ideally wireless receiving signal.
Fig. 2 is the time-delay power spectrum of wireless receiving signal under the actual conditions.
Fig. 3 is the schematic diagram of Multipath searching unit under the prior art.
Fig. 4 is the schematic diagram of single order IIR filter.
Fig. 5 is typical white Gaussian noise power spectrum schematic diagram.
Fig. 6 is the flow chart according to the multipath searching method of preferred embodiment of the present invention.
Fig. 7 is the schematic diagram according to the multipath searching device of preferred embodiment of the present invention.
Fig. 8 is the frame structure schematic diagram of WCDMA system uplink DPCH.
Fig. 9 is the flow chart according to the multipath searching method of another preferred embodiment of the present invention.
Figure 10 is the schematic diagram of the multipath searching device of realization method embodiment illustrated in fig. 9.
Embodiment
As mentioned above, the time-delay power spectrum is owing to relate to nonlinear operation, so noise is rendered as the nonwhite noise form and comprises more low frequency component, is difficult to suppress noise by low-pass filtering.For this reason, adopt two-layer low-pass filtering effectively to suppress noise component(s) in the present invention, wherein at first I branch road and the Q tributary signal on the sampling phase that calculates the low-pass filtering treatment done that before the time-delay power spectrum despreading descrambling is obtained carries out the ground floor low-pass filtering, and then the time-delay power spectrum that calculates is carried out second layer low-pass filtering.Why adopt the reason of two-layer low-pass filtering to be, because the polarity of I branch road and Q tributary signal may be reversed with wireless channel, therefore limited the output signal length of the filter that is used for tributary signal, this has restricted the performance of low pass filter.And there is not the signal counter-rotating in the signal energy value in the power spectrum, therefore can guarantee that filter output signal has enough length, thereby reach more desirable filter effect.In a word, the ground floor low-pass filtering was carried out tributary signal before calculating the time-delay power spectrum, its purpose is effectively to suppress noise when reducing signal counter-rotating influence, and second layer low-pass filtering is carried out the signal energy value of time-delay power spectrum, and its purpose is further to suppress noise.In addition, the above-mentioned tributary signal of making low-pass filtering treatment includes but not limited to known symbol or can adjudicate the signal of symbol.
Below by Fig. 6 a preferred embodiment according to the inventive method is described, suppose that in this embodiment I branch road and the Q tributary signal on each phase place that front-end processing obtains all can carry out low-pass filtering treatment.
As shown in Figure 6, in step 1, at first baseband signal is carried out front-end processing to obtain I branch road and the Q tributary signal value on each sampling phase by the despreading descrambling unit in the communication system receiver.
Then, in step 2 and 3, receiver carries out signal processing to I branch road and Q tributary signal value on each sampling phase of front-end processing acquisition.Wherein, in step 2, carry out the ground floor low-pass filtering treatment by branch road respectively, promptly, I tributary signal on each sampling phase is considered as one road signal carries out Filtering Processing, Q tributary signal on each sampling phase is considered as another road signal carries out Filtering Processing, so the Filtering Processing of two tributary signals on each sampling phase is independently to carry out.As mentioned above, the ground floor low-pass filtering should be considered the counter-rotating of I branch road and Q tributary signal, and therefore the output signal length of used filter can not be oversize.In step 3, to do relevant adding up through the tributary signal value after the Filtering Processing on each sampling phase, promptly, I branch road through low-pass filtering treatment on each sampling phase is obtained new I tributary signal value and Q tributary signal value with corresponding previous I branch road cumulative signal value and previous Q branch road cumulative signal value respectively mutually with Q tributary signal value, previous I branch road cumulative signal value here and previous Q branch road cumulative signal value are respectively the accumulated value of the I tributary signal value after process low-pass filtering treatment before the current tributary signal on this sampling phase and the accumulated value of Q tributary signal value, with the I tributary signal value on a certain phase place is example, suppose obtaining 5 before the current I tributary signal that obtains by front-end processing through the I tributary signal value after the low-pass filtering treatment, then Ci Shi previous I branch road cumulative signal value is this 5 I tributary signal value sums, also is like this for the Q branch road.It is worthy of note that when channel variation was slow, the relevant accumulation process of step 3 can further be improved the signal to noise ratio of signal on the basis of ground floor low-pass filtering, but for channel variation situation faster, then effect is very unobvious.Therefore the relevant accumulation process of step 3 is omissible, particularly when conversion speed being had relatively high expectations or receiver system when being subjected to cost and limiting.
In step 4, I branch road after adding up on each sampling phase and Q tributary signal value are made square summation operation to obtain the signal energy value E of each sampling phase according to following formula subsequently
i:
E
i＝I
i 2+Q
i 2 (1)
The subscript i here represents sampling phase numbering, I
iAnd Q
iRepresent respectively on i the sampling phase through I branch road and Q tributary signal value after the relevant accumulation process.
Then enter in the step 5, receiver is with the signal energy value E on each sampling phase
iCarry out irrelevant adding up, that is, and with this signal energy value E
iObtained new signal energy value mutually with corresponding previous signal energy accumulated value, wherein previous signal energy accumulated value is the accumulated value that passed through the signal energy value of low-pass filtering treatment on this sampling phase before current tributary signal, with the signal energy value on a certain phase place is example, suppose to have obtained before the current demand signal energy value 5 signal energy values through low-pass filtering treatment, then Ci Shi previous signal energy accumulated value is this 5 signal energy value sums.Therefore it is worthy of note that the irrelevant accumulation process of step 5 can not improve the signal to noise ratio of signal, is omissible, particularly when conversion speed being had relatively high expectations or receiver system when being subjected to cost and limiting.
After completing steps 5, promptly enter step 6,, that is, the signal energy value on each sampling phase is considered as one road signal carries out low-pass filtering treatment carrying out second layer low-pass filtering through the signal energy value after the irrelevant accumulation process on each sampling phase.As mentioned above, because there is not counter-rotating in the signal energy value, therefore the output signal length of used filter can be set longlyer.
In step 7, receiver can carry out the multi-path location judgement according to the signal energy value after step 6 second layer low-pass filtering, and in step 8, exports the multipath phase information and return step 1 according to court verdict.For the mode of the multi-path location of step 7 judgement, therefore the present invention is not limited in this respect, and non-content of the present invention, does not therefore deeply describe.Here be example only with the simplest situation, suppose not comprise in the above-mentioned processing procedure relevant adding up and the irrelevant step 3 that adds up and 5, then the multi-path location decision rule can preestablish a threshold value simply, and determine according to the comparative result of signal energy value and threshold value whether sampling phase is multi-path location, if the signal energy value is more than or equal to threshold value, then be judged to be multi-path location, otherwise be judged to be non-multi-path location.For comprising relevant adding up and the situation of the irrelevant step 3 that adds up and 5, the threshold value of this moment may be decided with the number that adds up, owing to deciding as the case may be, so do not thoroughly discuss.
Below by Fig. 7 a preferred embodiment according to multipath searching device of the present invention is described, same, suppose also that in this embodiment I branch road and the Q tributary signal on each phase place that despreading descrambling unit obtains all can carry out low-pass filtering treatment.In the embodiment shown in fig. 7, multipath searching device comprises despreading descrambling unit 41, ground floor low-pass filter unit 120, energy calculation unit 121, second layer low-pass filter unit 42, peak filter 43 and threshold value decision unit 44 successively.The function and the operation principle of each unit are below described respectively.
Despreading descrambling unit 41 obtains I branch road on each sampling phase and Q tributary signal and exports the tributary signal that obtains to ground floor low-pass filter unit 120 from baseband signal.Despreading descrambling unit 41 can adopt sliding correlation detector/correlator bank or matched filter to realize despreading descrambling function.It will be apparent to one skilled in the art that the operation principle of sliding correlation detector/correlator bank and matched filter and structure all are known, therefore repeat no more.
I branch road and Q tributary signal on each phase place of 120 pairs of despreading descramblings of ground floor low-pass filter unit unit, 41 outputs carry out the ground floor low-pass filtering treatment and export the result to energy calculation unit 121 by branch road respectively, as mentioned above, consider the counter-rotating of I branch road and Q tributary signal, so the output signal length of this used filter in unit can not be oversize.The ground floor low-pass filter unit also can comprise relevant accumulator module (not shown), it will do relevant adding up through the I branch road after the Filtering Processing respectively with Q tributary signal value on each sampling phase, its mode is similar to the step (3) in the previous embodiment, repeats no more herein.
Square summation module (not shown) in the energy calculation unit 121 will be through relevant accumulation process or is calculated signal energy value on each phase place to obtain some time-delay power spectrum and to export second layer low-pass filter unit 42 to through the tributary signal of the accumulation process of being correlated with according to following formula (1).
Second layer low-pass filter unit 42 can comprise irrelevant accumulator module (not shown), and it will do irrelevant adding up through the signal energy value after the Filtering Processing on each sampling phase in some time-delay power spectrum, and its mode is similar to the step (5) in the previous embodiment.Through irrelevant accumulation process or do not carry out low-pass filtering by the filters in the second layer low-pass filter unit 42 through the signal energy value of irrelevant accumulation process and will handle like this after the time-delay power spectrum export peak filtering unit 43 to.
Peak filtering unit 43 is determined peak and is exported peak phase and energy to multi-path judging unit 44 according to the time-delay power spectrum of second layer low-pass filter unit 42 outputs.
In the multipath searching device of the foregoing description, despreading descrambling unit 41 can be listed front-end processing unit in, and ground floor low-pass filter unit 120, energy calculation unit 121, second layer low-pass filter unit 42, peak filtering unit 43 and multi-path judging unit 44 then can be listed the back-end processing unit in.
Comprised following hypothesis in the multipath searching method of the invention described above and device: the I branch road that obtains on each sampling phase by the despreading scramble process to baseband signal all can carry out low-pass filtering treatment and relevant accumulation process with the Q tributary signal.But it is really not so in some cases, for example as known symbol or can adjudicate the signal of symbol, tributary signal on its phase place can be made low-pass filtering treatment and/or relevant accumulation process, and maybe can't adjudicate the signal of symbol for other unknown symbols, the tributary signal on its phase place but can not be done such processing.For these situations, method and apparatus of the present invention remains suitable, conspicuous processing mode is, for tributary signal, at first judge whether to make low-pass filtering treatment,, then still carry out two-layer low-pass filtering treatment of the present invention if can make low-pass filtering treatment, otherwise, then adopt other Filtering Processing mode.In a word, no matter be whole signals or the part signal that front-end processing unit is provided,, all belong in the spirit and scope of the present invention as long as adopted above-mentioned two-layer filter processing method.
Below be that example is further described with the uplink transport channel of WCDMA system.Fig. 8 shows the frame structure of WCDMA system uplink DPCH, this channel is made up of the special used for physical control channel DPCCH and the Dedicated Physical Data Channel DPDCH of parallel transmission, wherein pilot tone (pilot) signal is because known symbol, therefore the ground floor filtering that can be used for Multipath searching adds up with relevant, but the time slot of it and other information (for example TFCI territory, FBI territory and TPC territory etc.) time division multiplexing DPCCH channel as shown in Figure 8.
Below specifically describe the multipath searching method of under said circumstances, using the two-layer lowpass filtering theory of the present invention by Fig. 9.Adopt single order infinite impulse response (IIR) filter shown in Figure 4 to finish two-layer low-pass filtering treatment in the method, and for the ground floor low-pass filtering, its filter parameter α is variable, that is adopt the less parameter alpha of numerical value when, the pilot tone that is positioned at DPCCH channel time slot when sampling phase begins the chip place
2With the sensitivity of raising Filtering Processing, and adopt the bigger parameter alpha of numerical value when time on other pilot chip that is positioned at time slot
1, then adopt constant parameter alpha for second layer low-pass filtering
3To improve the stability of Filtering Processing
As shown in Figure 9, in step 1, at first baseband signal is carried out front-end processing to obtain I branch road and the Q tributary signal value on each sampling phase by the despreading descrambling unit in the receiver.Then, in step 2, receiver judges whether each sampling phase is in the pilot portion of a time slot, promptly judges whether to be in the N in each DPCCH channel time slot among Fig. 8
PilotIndividual pilot bits part.If judge to be in pilot portion, then enter step 3, otherwise directly enter step 8.In step 3, receiver judges that further the pilot chip whether sampling phase is positioned at a time slot begins the place, if not, then enter step 4, be that the first order IIR filtering device is set the bigger parameter alpha of numerical value
1, otherwise enter step 5, be the less parameter alpha of filter configuration numerical value
2Behind step 4 or 5 selected filter parameters, promptly enter step 6 and 7 successively, I branch road on each sampling phase and Q tributary signal are carried out and described identical ground floor low-pass filtering treatment embodiment illustrated in fig. 6 and signal correction accumulation process.
In step 8, the I branch road on each sampling phase after relevant the adding up and Q tributary signal value (when sampling phase is positioned at the pilot portion of time slot) or the not relevant I branch road that adds up and Q tributary signal value (when sampling phase is positioned at the non-pilot portion of time slot) according to formula (1) work square summation operation to obtain the signal energy value E of each sampling phase
i
Subsequently, in step 9, according to described mode embodiment illustrated in fig. 6 with the signal energy value E on each sampling phase
iCarry out irrelevant adding up, and in step 10, to carrying out second layer low-pass filtering through the signal energy value after the irrelevant accumulation process on each sampling phase, as mentioned above, adopting parameter here is α according to described mode embodiment illustrated in fig. 6
3The first order IIR filtering device finish low-pass filtering treatment.
Enter step 11 subsequently, receiver is according to described mode embodiment illustrated in fig. 6, carry out the multi-path location judgement according to the signal energy value after step 10 second layer low-pass filtering, and in step 12, receiver is according to court verdict output multipath phase information and return step 1.
Below by Figure 10 the multipath searching device block diagram of realizing method embodiment illustrated in fig. 9 is described.As shown in figure 10, this is applicable to that the device of WCDMA system uplink channel Multipath searching comprises despreading descrambling unit 41, ground floor low-pass filter unit 120, the relevant unit 150 that adds up, input data selection unit 151, energy calculation unit 152, the irrelevant unit 153 that adds up, second layer low-pass filter unit 154, peak filter 43, threshold judgement unit 44, ground floor low-pass filtering parameter selection unit 155 and control unit 156 successively.Below distinguish the function and the operation principle of each unit, the unit similar or identical with Fig. 7 all uses identical label to represent among the figure.
Under the control of control unit 156, ground floor low-pass filter unit 120 adopts single order infinite impulse response (IIR) filter shown in Figure 4 that I branch road on each phase place of despreading descrambling unit 41 outputs is carried out the ground floor low-pass filtering treatment and exports the result to the relevant unit 150 that adds up by branch road respectively with the Q tributary signal.The parameter alpha of filter is selected by ground floor low-pass filtering parameter selection unit 155, and when the pilot tone that is positioned at DPCCH channel time slot when sampling phase began the chip place, less parameter alpha was selected for the first order IIR filtering device in unit 155
2With the sensitivity of improve handling, and when on other pilot chip that is positioned at time slot, then select bigger parameter alpha
1To improve the stability of handling.
Relevant add up unit 150 under the control of control unit 156 with each sampling phase on through the I branch road after the ground floor Filtering Processing and Q tributary signal value do respectively relevant add up and export to import data selection unit 151, relevant accumulate mode is similar to the step (3) in the previous embodiment, repeats no more herein.
Under the control of control unit 156, it is that the output signal of despreading descrambling unit 41 or the output signal of the relevant unit 150 that adds up are delivered to energy calculation unit 152 that input data selection unit 151 is selected, particularly, if the sampling phase of tributary signal is positioned at the pilot portion of DPCCH channel time slot, then selecting to be correlated with, and the add up signal of unit 150 outputs is delivered to energy calculation unit 152, otherwise, directly the output signal of despreading descrambling unit 41 is delivered to energy calculation unit 152.
Signal energy value through irrelevant accumulation process exports peak filtering unit 43 to by the time-delay power spectrum that the first order IIR filtering device in the second layer low-pass filter unit 42 will carry out after low-pass filtering also will be handled like this.
Peak filtering unit 43 is determined peak and is exported peak phase and energy to multi-path judging unit 44 according to the time-delay power spectrum of second layer low-pass filter unit 42 outputs.Multi-path judging unit 44 judges according to peak energy and certain decision rule of the output of peak filtering unit whether peak is multi-path location, and exports judged result to the subsequent treatment unit.Equally, for the judgement mode, as mentioned above,, therefore deeply do not describe owing to do not belong to scope of the present invention.
It is worthy of note that in device shown in Figure 10, control unit 156 is relatively independent of ground floor low-pass filter unit 120, relevant unit 150 and the input data selection unit 151 and these unit are realized the control corresponding function of adding up.As another kind of substitute mode, such control unit needn't independently exist but the control corresponding function can be integrated in separately the unit to be realized.But no matter adopt which kind of mode, all do not have substantial influence for the present invention by the principle that two-layer low-pass filtering reduces the noise low frequency component, so they do not constitute the qualification to spirit and scope of the invention.
Claims (10)
1. multipath searching method that is used for code division multiple address communication system, receiver in the described communication system obtains I branch road and Q tributary signal on each sampling phase by the despreading scramble process to baseband signal, it is characterized in that described receiver obtains multi-path location according to following steps:
(1) judges whether I branch road and Q tributary signal on the sampling phase can do low-pass filtering treatment, and I branch road on the sampling phase that can make low-pass filtering treatment and Q tributary signal value are finished signal processing by branch road respectively, and described signal processing comprises low-pass filtering; The signal that can not make low-pass filtering treatment is entered next step;
(2) will carry out square summation operation to obtain the signal energy value on each sampling phase through step (1) processing with without I tributary signal value and Q tributary signal value on each sampling phase of step (1) processing;
(3) the signal energy value on each sampling phase is finished signal processing, described signal processing comprises low-pass filtering; And
(4) according to determining through the signal energy value after step (3) processing whether this phase place is multi-path location on each sampling phase.
2. multipath searching method as claimed in claim 1, it is characterized in that, the signal processing of described step (1) further comprises: will be obtained new I tributary signal value and Q tributary signal value mutually with corresponding previous I branch road cumulative signal value and previous Q branch road cumulative signal value through the I branch road of low-pass filtering treatment respectively with Q tributary signal value on each sampling phase, wherein previous I branch road cumulative signal value and previous Q branch road cumulative signal value are respectively on this sampling phase the accumulated value of the I tributary signal value of process low-pass filtering treatment and the accumulated value of Q tributary signal value before current tributary signal.
3. multipath searching method as claimed in claim 2, it is characterized in that, the signal processing of described step (3) further comprises: the signal energy value on each sampling phase that before the low-pass filtering treatment step (2) is obtained is obtained new signal energy value mutually with corresponding previous signal energy accumulated value, and wherein previous signal energy accumulated value is the accumulated value that passed through the signal energy value of low-pass filtering on this sampling phase before current tributary signal.
4. as any described multipath searching method among the claim 1-3, it is characterized in that I branch road on the described sampling phase of making low-pass filtering treatment and Q tributary signal comprise that known symbol maybe can adjudicate the signal of symbol.
5. as any described multipath searching method among the claim 1-3, it is characterized in that, described baseband signal belongs to the signal of transmission in the WCDMA system uplink physics Dedicated Control Channel, the I branch road and the Q tributary signal value that in step (1) sampling phase are arranged in the time slot pilot portion are finished signal processing by branch road respectively, and described signal processing comprises low-pass filtering; And I branch road and Q tributary signal value that sampling phase is arranged in outside the time slot pilot portion are not made low-pass filtering treatment.
6. multipath searching method as claimed in claim 5, it is characterized in that, in step (1), adopt the single order IIR filter that I branch road and Q tributary signal value that sampling phase is arranged in the time slot pilot portion are carried out low-pass filtering treatment, if and sampling phase is arranged in time slot pilot portion start element place, then the single order IIR filter adopts less filter parameter to improve process sensitivity, if sampling phase is arranged in the non-start element of time slot pilot portion place, then the single order IIR filter adopts bigger filter parameter to improve Treatment Stability.
7. multipath searching device that is used for code division multiple address communication system, form by front-end processing unit and back-end processing unit, described front-end processing unit obtains I branch road and Q tributary signal on each sampling phase by despreading scramble process baseband receiving signals, multi-path location is determined according to I branch road on the sampling phase and Q tributary signal in described back-end processing unit, it is characterized in that described back-end processing unit comprises:
The ground floor low-pass filter unit is used for I branch road and Q tributary signal value on the sampling phase of the low-pass filtering treatment done of front-end processing unit output are finished signal processing by branch road respectively, and described signal processing comprises low-pass filtering;
The input data selection unit, the signal that can do on the sampling phase of low-pass filtering treatment is sent into energy calculation unit after the ground floor low-pass filter unit is handled, and the signal that can not do on the sampling phase of low-pass filtering treatment is directly sent into energy calculation unit;
Energy calculation unit is used for and will handles through the ground floor filter unit and carry out square summation operation to obtain the signal energy value on each sampling phase without I tributary signal value and Q tributary signal value on each sampling phase of ground floor low-pass filter unit processing;
Second layer low-pass filter unit is used for the signal energy value on each sampling phase of energy calculation unit output is finished the time-delay power spectrum of low-pass filtering treatment to obtain to constitute by through signal energy value on each phase place after the low-pass filtering;
The peak filtering unit, the phase place and the energy value of each peak position of time-delay power spectrum that is used for determining that described second layer low-pass filter unit obtains; And
The multi-path judging unit is used for judging according to each peak position energy value of certain decision rule and the output of described peak filtering unit whether this peak position is multi-path location and exports judged result.
8. multipath searching device as claimed in claim 7, it is characterized in that, described ground floor low-pass filter unit further comprises relevant accumulator module, be used for and will be obtained new I tributary signal value and Q tributary signal value mutually with corresponding previous I branch road cumulative signal value and previous Q branch road cumulative signal value through the I branch road of low-pass filtering treatment respectively with Q tributary signal value on each sampling phase, wherein previous I branch road cumulative signal value and previous Q branch road cumulative signal value are respectively on this sampling phase the accumulated value of the I tributary signal value of process low-pass filtering treatment and the accumulated value of Q tributary signal value before current tributary signal.
9. multipath searching device as claimed in claim 8, it is characterized in that, described second layer low-pass filter unit further comprises the irrelevant unit that adds up, the signal energy value that is used on each sampling phase that before the low-pass filtering treatment energy calculation unit is obtained is obtained new signal energy value mutually with corresponding previous signal energy accumulated value, and wherein previous signal energy accumulated value is the accumulated value that passed through the signal energy value of low-pass filtering on this sampling phase before current tributary signal.
10. as any described multipath searching device among the claim 7-9, it is characterized in that I branch road on the described sampling phase of making low-pass filtering treatment and Q tributary signal comprise that known symbol maybe can adjudicate the signal of symbol.
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| CN101557243B (en) * | 2008-04-11 | 2013-09-11 | 中兴通讯股份有限公司 | Device and method for carrying out self-adaptive filtering to pilot channel |
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