CN1992542B - Implementation method of multipath search in CDMA - Google Patents
Implementation method of multipath search in CDMA Download PDFInfo
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- CN1992542B CN1992542B CN2005101325783A CN200510132578A CN1992542B CN 1992542 B CN1992542 B CN 1992542B CN 2005101325783 A CN2005101325783 A CN 2005101325783A CN 200510132578 A CN200510132578 A CN 200510132578A CN 1992542 B CN1992542 B CN 1992542B
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Abstract
This invention discloses a CDMA multi-path search method, including the following steps: sliding correlation; current time delay expansion average; time delay expansion accumulation; peak search; path filter; remaining air path processing path detection by path detection module; path test: path test to every air path, and if the current time delay expansion has maximum value or convex inflexion point near this path, considering that this path exists, otherwise this path disappeared, and removing this path; indication peak distribution: obtaining the air path from path detection module, and according to the shortest time delay distribution principle, allocating the air path to the indication peak of RAKE receiver. The method of the invention is based on the time delay expansion average, and uses time delay expansion accumulation, significantly reducing the time delay expansion noise, increasing time delay expansion SNR, thus making multi-path search more accurate and reducing the false alarm; meanwhile, it can increase the frequency of indication perk flush, and in favor of reducing error code rate.
Description
Technical field
The present invention relates to a kind of multipath searching method of CDMA receiver side, in particular a kind of as the Multipath searching function among WCDMA and the TD-SCDMA, comprise time delay expansion calculating, the method for path detection and finger peak distribution etc.
Background technology
In the mobile communication of prior art, the signal that sends from the base station propagates into the user along different propagation paths, because the length difference of these propagation paths, so these signals arrival users' time is also different, has time delay each other.Generally speaking, the spreading rate of cdma system is very high, and scrambler has good autocorrelation in addition, thereby has very strong multi-path resolved rate, can make full use of the intrinsic frequency diversity of multipath channel, improves the error performance of system.
The Multipath searching function of cdma receiver is the signal of receiving by despreading, forms the time delay expansion, and aerial path is determined in expansion according to time delay, and follows the tracks of the variation in aerial path, gives the finger peak of RAKE receiver aerial path allocation.RAKE receiver is carried out despreading according to finger peak information to the data in every aerial path, again all these is referred to that the pairing despread data in peak merges by high specific.Can effectively improve receptivity like this.
At present multipath searching method mainly comprises and slides relevantly, and the time delay expansion is average, and time delay expansion peak value searching refers to the peak protection, refers to that the peak refreshes and refers to step such as peak distribution.
The relevant I to receiving of slip, the Q data are slided relevant with scrambler and spreading code, obtain the time delay expansion.
The time delay expansion on average adds up to a plurality of time delay expansions of calculating in the frame and asks average, eliminates white noise and obtains the higher time delay expansion of signal to noise ratio.
Refer to that the peak refreshes according to the result who refers to the peak protection, refreshes the time delay information that refers to the peak.
The current average method of time delay expansion mainly is to calculate a plurality of time delay expansions in every frame, and asks the average of these time delay expansions, and then the time delay expansion of multiframe is on average asked average again, further eliminates white noise.
Yet there is defective in the method for eliminating white noise like this, in order to obtain higher signal to noise ratio, obtain the aerial path delay of time accurately, just need to increase the quantity of the time delay expansion of participating in average computation, can refer to that the peak calculates more time delay expansion in the refresh cycle at one, also can refer to the peak refresh cycle by prolongation, increase and participate in average time delay expansion quantity, yet so just need or increase system resource, or reduction refers to the refreshing frequency at peak, increase the rising that system resource can cause product cost, if it is reduce the refreshing frequency that refers to the peak, well-known, the propagation path of signal is change in real time, therefore propagation path might occur and change, and refer to that the peak position in time do not refresh, cause the error rate height of the data that the RAKE receiver despreading comes out.
Refer to the frequency that the peak refreshes if improve, just need to reduce the frame number of time delay expansion accumulation, and so, the signal to noise ratio of time delay expansion has just reduced, the power of the power of noise greater than signal might occur, even some signal is too low owing to power, the number of peaks of peak value searching searching functions is limited, and can not find these paths, these paths are lost.The peak value that peak value searching obtains is not aerial path entirely yet, and some is a noise.Leach these noises amplitude or signal-noise ratio threshold normally are set,, just think that this is an aerial path, thinks noise on the contrary when the amplitude of peak value or signal to noise ratio during greater than this thresholding.Because the signal to noise ratio of time delay expansion is not very high, therefore has the phenomenon of noise power greater than signal power, cause thresholding to be difficult for being provided with, if threshold setting is too high, false-alarm can reduce, and fails to report and can increase.If threshold setting is too low, to fail to report and can reduce, false-alarm can increase.
Therefore, prior art access defective, and await improving and development.
Summary of the invention
The object of the present invention is to provide a kind of implementation method of the CDMA of being used for Multipath searching, on the average basis of time delay expansion, utilize the method for time delay expansion accumulation again, significantly improve the signal to noise ratio of time delay expansion, searching route in the expansion of accumulation time delay, in current time delay expansion, confirm the multipath searching method in path, thereby obviously reduce false-alarm and fail to report, even under the situation of signal power less than noise power, also can extract correct signal, and remove noise signal, and need not to reduce and refer to the peak refreshing frequency, even can refer to that the peak refreshes by every frame.
Technical scheme of the present invention comprises:
A kind of implementation method that is used for the CDMA Multipath searching, it may further comprise the steps:
A, slip are correlated with; The I with scrambler and spreading code to receiving, the Q data are slided relevant, obtain the time delay expansion;
B, current time delay are expanded on average: the several time delays expansions to present frame ask average, improve the signal to noise ratio that time delay is expanded, and on average path detection module and time delay expansion accumulation module are given in the time delay expansion after respectively;
C, time delay expansion accumulation: the accumulation of the time delay expansion after finishing on average, further eliminate the white noise that time delay is expanded;
D, peak value searching: the maximum of time delay expanded search specified quantity to accumulation, whenever find after the maximum, the amplitude of 0.75 chip in the right both sides of this maximum point and the left side thereof is changed to 0, no longer considering this path in the peak value searching process next time;
E, path filtering: check whether the peak value that the peak value searching module obtains satisfies as the requirement in path in the air, the thresholding of set path energy and the ratio of accumulation time delay expansion most powerful path energy, the peak value that is higher than this thresholding is regarded aerial path as, the peak value that is lower than this thresholding is considered to noise, and deleted; Remaining aerial path is fed to the path detection module and does path detection;
F, path detection: path detection is done in every aerial path, if the expansion of current time delay has maximum or protruding flex point near this path, if the energy of this maximum point or protruding flex point is expanded the thresholding of the ratio of most powerful path energy greater than a setting with current time delay, think that then this path also exists, otherwise think that this path disappears, deletes this path;
G, refer to that the peak distributes: obtain aerial path from the path detection module, and give finger peak in the RAKE receiver with aerial path allocation by prolonging distribution principle the most in short-term.
Described method wherein, also is included in and calculates a plurality of time delay expansions in the same frame, and give current time delay with the time delay expansion and expand average module.
Described method, wherein, the formula of described accumulation comprises:
Z[K]=Z[K-1]+(Y[K]-Z[K-1])/N (formula 1)
Z[K wherein] be the current time delay expansion accumulating value that obtains, Z[K-1] be the result of last time delay expansion accumulation, Y[K] be that current time delay is expanded, N is an adjustable parameter, can find an only N by emulation.
A kind of implementation method that is used for the CDMA Multipath searching provided by the present invention by on the average basis of time delay expansion, increases time delay expansion accumulation, obviously reduced the noise of time delay expansion, improve the signal to noise ratio of time delay expansion, thereby made Multipath searching more accurate, reduced false-alarm; Improved the frequency that the finger peak refreshes simultaneously, when aloft the path changes, in time refreshed the finger peak position, thereby reduced the error rate.
Description of drawings
Fig. 1 is the Multipath searching configuration block diagram of the inventive method;
Fig. 2 is the Multipath searching main flow chart of the inventive method;
Fig. 3 adds up for the relevant homophase of the inventive method, average schematic diagram;
Fig. 4 is the path detection schematic flow sheet of the inventive method;
Fig. 5 is the finger peak allocation flow schematic diagram of the inventive method;
Fig. 6 is aerial path of the inventive method and the delay inequality tabular drawing between the current finger peak position;
Fig. 7 is aerial path of the inventive method and the delay inequality tabular drawing between the distribution back, current finger peak position.
Embodiment
Below in conjunction with accompanying drawing, will carry out comparatively detailed explanation to each preferred embodiment of the present invention.
The implementation method that is used for the CDMA Multipath searching of the present invention, its signal that sends from the base station is through behind the high frequency receiving circuit, sampling transfers digital signal to through A/D, gives respectively to refer to that the peak receives and the Multipath searching module, and the Multipath searching of the inventive method comprises the steps:
A, slip are correlated with: the I to receiving with scrambler and spreading code, the Q data are slided relevant, obtain the time delay expansion.In order to improve the signal to noise ratio of time delay expansion, can in same frame, calculate a plurality of time delay expansions, and give current time delay with the time delay expansion and expand average module.
B, current time delay are expanded average: the several time delays expansions to present frame ask average, improve the signal to noise ratio that time delay is expanded.Path detection module and time delay expansion accumulation module are given in time delay expansion after average respectively.
C, time delay expansion accumulation: finish the accumulation of time delay expansion, further eliminate the white noise of time delay expansion.The accumulation formula is as follows:
Z[K]=Z[K-1]+(Y[K]-Z[K-1])/N (formula 1)
Z[K in the formula] be the current time delay expansion accumulating value that obtains, Z[K-1] be the result of last time delay expansion accumulation, Y[K] be current time delay expansion, N is an adjustable parameter, can find an only N by emulation.
D, peak value searching: to the maximum of time delay expanded search specified quantity of accumulation.Whenever find after the maximum, the amplitude of 0.75 chip of this maximum point and the left side thereof and 0.75 chip in the right is changed to 0, do not considering this path in the peak value searching process next time.
E, path filtering: check whether the peak value that the peak value searching module obtains satisfies as the requirement in path in the air, can the set path energy and the thresholding of the ratio of accumulation time delay expansion most powerful path energy, the peak value that is higher than this thresholding can be regarded as aerial path, the peak value that is lower than this thresholding is considered to noise, and deleted.Remaining aerial path is fed to the path detection module and does path detection.
F, path detection: path detection is done in every aerial path, if the expansion of current time delay has maximum or protruding flex point near this path, if the energy of this maximum point or protruding flex point is expanded the thresholding of the ratio of most powerful path energy greater than a setting with current time delay, think that then this path also exists, otherwise think that this path disappears, deletes this path.
G, refer to that the peak distributes: obtain aerial path from the path detection module, and give finger peak in the RAKE receiver with aerial path allocation by prolonging distribution principle the most in short-term.
As shown in Figure 1, realize an example of Multipath searching for the inventive method.Have 12 and refer to the peak in this example, over-sampling rate is 4, and the width of search window is a symbol, i.e. 1024 sampling points.The flow chart of example is seen shown in Figure 2.
Slip correlation module as shown in fig. 1, the I of the A/D that learnt from else's experience sampling, the Q data, each activates the sub-district, and every frame calculates 4 time delay expansions, and the width of time delay expansion is a symbol, i.e. 1024 sampling.The expansion of each time delay is done homophase by the correlated results of 4 symbols and is added up and be averaged and obtain, and is the computational process of a time delay expansion as Fig. 3.The symbol that the participation homophase adds up is designated as correlation1, correlation2, correlation3, correlation4 respectively.After the slip correlation module has calculated 4 time delay expansions,, ask average, deliver to time delay again and expand average module its addition.
The average step-length of described time delay expansion gets 2, is about to continuous 2 frames, and totally 8 time delays expansion additions ask average.Give time delay expansion accumulation module with the time delay expansion that obtains after average.
Described time delay expansion accumulation module accumulates the time delay expansion that each activates the sub-district according to formula 1, and per 2 frames accumulation is once preserved Z[K after the accumulation] be used for accumulating next time, and with Z[K] give the peak value searching module.Z[K] initial value be made as zero.
Described time delay expansion peak value search module is in whole search window, the maximum of 1024 the interior search of sampled point scope specified quantities, the corresponding aerial path of each maximum point, search out a maximum point after, this point of shielding and 3 on the left side and the right 3 points in the time delay expansion.After search is finished, the amplitude of the left point of time delay expansion is asked on average as average noise, with the position and the amplitude of all maximum points, average noise is given the path filtering module at last.
Described path filtering module is at first calculated the ratio of all aerial paths and most powerful path, and the thresholding according to setting leaches the aerial path that energy does not reach thresholding, gives the path detection module with remaining aerial path.
Described path detection module all detects every aerial path that the path filtering module is sent here, if the path is found in current time delay expansion, be that this place, path time delay exists maximum point or protruding flex point in current time delay expansion, and the energy of this point is expanded the ratio of the energy of going up most powerful path greater than a thresholding of setting with current time delay, then keep this path participation and refer to that the peak distributes, the setting of this thresholding is a benchmark can enroll available path.Do not find if in current time delay expansion,, illustrate that then this path disappears, deletes this path.
Testing process figure in the inventive method sees shown in Figure 4, it is phase place according to aerial path, on the same phase place of current time delay expansion and 2 on a left side and right 2 totally 5 points, this power of 5 is sorted from big to small, begin to check that this point is a maximum point then from prominent point?
◆ if maximum point represents that this aerial path is found.
◆ if not maximum point, check then whether this point is protruding flex point.
● if protruding flex point represents that this aerial path is found.
● if not protruding flex point, represent that this aerial path disappears.
If the path is found, whether the energy of checking this point satisfies the thresholding of setting with the ratio that the energy of most powerful path is gone up in current time delay expansion, if satisfy the thresholding of setting, represent that this path also exists, with each 3 point about this point, the amplitude of totally 7 sampling points is changed to 0, directly returns, and needn't check other sampling points.If path energy does not satisfy the thresholding of setting, repeat above-mentioned steps, check all the other sampled points.
If the path is not found, repeat above-mentioned steps, check all the other sampled points.If the path also exists, keep this path, otherwise delete this path.
Step above repeating is done path detection to all aerial paths, and remaining aerial path is given and referred to the peak distribution module.
The described finger of the inventive method peak distribution module is finished the distribution that refers to the peak, in order to guarantee to refer to the continuity at peak, reduces the error rate, adopts the minimal time delay difference to join principle, and the course of work is as follows:
At first calculate the delay inequality between every aerial path and the current finger peak position, suppose to have 12 aerial paths and 12 finger peaks, therefore calculate 144 delay inequalities altogether, see chart shown in Figure 6.Minimum value of search refreshes the position at the finger peak of this minimal time delay difference correspondence with the aerial path position of this minimal time delay difference correspondence in these 144 time delay differences, finishes the distribution at a finger peak.With all positions of the row and column at this minimal time delay difference place, be changed to maximum (for example 2000), as shown in Figure 7, refer in the peak assigning process at the next one like this, do not considering that this refers to peak and aerial path.
Repeat above-mentioned steps, refer to that up to all the peak assigns, the flow chart of described finger peak distribution module is seen shown in Figure 5.
The implementation method that is used for the CDMA Multipath searching of the present invention by on the average basis of time delay expansion, increases time delay expansion accumulation, obviously reduced the noise of time delay expansion, improve the signal to noise ratio of time delay expansion, thereby made Multipath searching more accurate, reduced false-alarm; Improved the frequency that the finger peak refreshes simultaneously, when aloft the path changes, in time refreshed the finger peak position, thereby reduced the error rate.
Should be understood that above-mentioned explanation at embodiment is comparatively detailed, can not therefore be interpreted as the restriction to scope of patent protection of the present invention, scope of patent protection of the present invention should be as the criterion with claims.
Claims (4)
1. implementation method that is used for the CDMA Multipath searching, it may further comprise the steps:
A, slip are correlated with; The I with scrambler and spreading code to receiving, the Q data are slided relevant, obtain the time delay expansion;
B, current time delay are expanded on average: the several time delays expansions to present frame ask average, improve the signal to noise ratio that time delay is expanded, and on average path detection module and time delay expansion accumulation module are given in the time delay expansion after respectively;
C, time delay expansion accumulation: the accumulation of the time delay expansion after finishing on average, further eliminate the white noise that time delay is expanded;
D, peak value searching: the maximum of time delay expanded search specified quantity to accumulation, whenever find after the maximum, the amplitude of 0.75 chip in the right both sides of this maximum point and the left side thereof is changed to 0, no longer considering this path in the peak value searching process next time;
E, path filtering: check whether the peak value that the peak value searching module obtains satisfies as the requirement in path in the air, the thresholding of set path energy and the ratio of accumulation time delay expansion most powerful path energy, the peak value that is higher than this thresholding is regarded aerial path as, the peak value that is lower than this thresholding is considered to noise, and deleted; Remaining aerial path is fed to the path detection module and does path detection;
F, path detection: path detection is done in every aerial path, if the expansion of current time delay has maximum or protruding flex point near this path, if the energy of this maximum point or protruding flex point is expanded the thresholding of the ratio of most powerful path energy greater than a setting with current time delay, think that then this path also exists, otherwise think that this path disappears, deletes this path;
G, refer to that the peak distributes: obtain aerial path from the path detection module, and give finger peak in the RAKE receiver with aerial path allocation by prolonging distribution principle the most in short-term.
2. method according to claim 1 is characterized in that, also is included in to calculate a plurality of time delay expansions in the same frame, and gives current time delay with the time delay expansion and expand average module.
3. method according to claim 1 is characterized in that, the formula of described accumulation comprises:
Z[K]＝Z[K-1]+(Y[K]-Z[K-1])/N
Z[K wherein] be the current time delay expansion accumulating value that obtains, Z[K-1] be the result of last time delay expansion accumulation, Y[K] be that current time delay is expanded, N is an adjustable parameter, can find an only N by emulation.
4. whether method according to claim 1 is characterized in that, expands enterprising walking along the street path search in the time delay of accumulation, directly detect and confirm and exist and expand enterprising walking along the street in current time delay.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1459930A (en) * | 2002-05-20 | 2003-12-03 | 上海贝尔有限公司 | Ruike receiver multipath searching device using energy estimation and multipath searching method |
| CN1492610A (en) * | 2002-10-24 | 2004-04-28 | 华为技术有限公司 | Multipath searching method and device in CDMA system |
| CN1684373A (en) * | 2004-04-13 | 2005-10-19 | 上海明波通信技术有限公司 | Multipath searching method and its device in mobile communication system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1459930A (en) * | 2002-05-20 | 2003-12-03 | 上海贝尔有限公司 | Ruike receiver multipath searching device using energy estimation and multipath searching method |
| CN1492610A (en) * | 2002-10-24 | 2004-04-28 | 华为技术有限公司 | Multipath searching method and device in CDMA system |
| CN1684373A (en) * | 2004-04-13 | 2005-10-19 | 上海明波通信技术有限公司 | Multipath searching method and its device in mobile communication system |
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Effective date of registration: 20151112 Address after: Dameisha Yantian District of Shenzhen City, Guangdong province 518085 Building No. 1 Patentee after: SHENZHEN ZTE MICROELECTRONICS TECHNOLOGY CO., LTD. Address before: 518057, Guangdong Shenzhen hi tech Industrial Park Nanshan District science and technology south road ZTE building 6 floor of the Ministry of law Patentee before: ZTE Corporation |
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Application publication date: 20070704 Assignee: Xi'an Chris Semiconductor Technology Co. Ltd. Assignor: SHENZHEN ZTE MICROELECTRONICS TECHNOLOGY CO., LTD. Contract record no.: 2019440020036 Denomination of invention: Implementation method of multipath search in CDMA Granted publication date: 20110511 License type: Common License Record date: 20190619 |
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