CN1160868C - Multi path despreading method for spread spectrum communication system - Google Patents
Multi path despreading method for spread spectrum communication system Download PDFInfo
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- CN1160868C CN1160868C CNB001194429A CN00119442A CN1160868C CN 1160868 C CN1160868 C CN 1160868C CN B001194429 A CNB001194429 A CN B001194429A CN 00119442 A CN00119442 A CN 00119442A CN 1160868 C CN1160868 C CN 1160868C
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Abstract
A multi-path despreading method for a spread spectrum communication system comprises the following steps: data from n signal channels are quantized respectively by an analogue-to-digital conversion circuit; then, the quantized data are stored in respectively corresponding data storage devices; afterwards, the multi-path despread is carried out after the multi-path data of the n signal channels are read out from different positions of each data storage device in sequence according to multi-path peak values and multi-path delay values. The multi-path despread comprises the following steps: firstly, despreading the data in advance; secondly, accumulating the despreading secondarily; thirdly, accumulating the despreading for many times; finally, outputting the multi-path despreading data of the n signal channels. The present invention saves hardware sources desired for realizing a digital circuit.
Description
Technical field
The present invention relates to a kind of multi path despreading method of spread spectrum communication system.
Background technology
When carrying out radio communication, the multipath transmisstion that signal produces can produce harmful multipath and disturb.RAKE in the spread spectrum communication system (multipath) receiver can separate and merge these multipath signals, realizes rake, to improve the performance of system.The RAKE receiver system generally all is by multipath signal being searched for, regularly and follow the tracks of, thereby obtains the energy peak A1 of different multipaths, A2, and A3 ... and the time t1 of multidiameter, t2, t3 ....It then is to select the high several multipaths of energy to carry out the multipath merging according to A that obtains and t that last RAKE merges.Because in the process of the signal of spread spectrum communication emission, modulation symbol has passed through the modulation of frequency expansion sequence, so should carry out remerging after the despreading to the multipath data earlier before the multipath merging.
What suppose that modulated terminal adopts is two-channel QPSK (four phase frequency shift keyings) band spectrum modulation, and the despreading method of multichannel band spectrum modulation mode to other also is similar so.
As shown in Figure 1, be the general implementation structure of multi path despreading.Receive I, Q circuit-switched data from antenna and at first quantize, then being kept in the data storage through the data after quantizing through mould/number (A/D) change-over circuit.According to the peak A of RAKE receiver search, the multipath that traces into and the value of multipath delay t, by the diverse location of storage control section control from data storage data are read out afterwards, this just is equivalent to obtain each multipath data.Respectively these multipaths are carried out despreading, then the multipath after the despreading is carried out energy and merge.In despreading process, the despreading of multipath can adopt the method for flowing water to make several the shared same set of despreading resources of multipath, as shown in Figure 1.Despreading process is the process that an integration adds up, and its realization has utilized an adder and a shift register, and the length of shift register is the length of multipath number in the modulated process.Shift register also can adopt RAM to replace.
The length of supposing the frequency expansion sequence that modulated terminal is used is 32, employing is extended to the spectrum spreading method of 32 chips to a modulation symbol, then just need do to adjudicate after the adding up of 32chip the back to the received signal to recover the modulation symbol before the modulation in despreading.
According to the nyquist sampling law, the sample rate of A/D part is at least 2 times chip (chip) speed 2fc.The sampling rate of supposing the A/D part is 4fc, and quantified precision is 4bit (bit), and then the clock rate of storage is 4fc, and the width of memory is 4bit.If needing the number of the multipath of RAKE merging is 4, because the shared same set of despreading resource of multipath, then the clock rate of the clock rate of reading of data and shift register all is 4fc from memory.Structure according to Fig. 1, the order of the data of reading from data storage cell is: f0d0 (the 0th data of the 0th of multipath the chip), f1d0 (the 1st data of the 0th of multipath the chip), f2d0 (the 2nd data of the 0chip of multipath), f3d0 (the 3rd data of the 0th of multipath the chip), f0d1 (the 0th data of the 1st of multipath the chip), f1d1, f2d1, f3d1, f0d2, f1d2 .....
After local frequency expansion sequence PNI that produces of these data and demodulating end and PNQ multiply each other, deliver to the integration despread unit that adds up and finish the despreading that receives data.The output of last shift register has been exactly the flowing water data flow of the multipath after the despreading.
What Fig. 1 drew is the I of two channels, the despreading schematic diagram of Q two-way, when also having more a plurality of channels to need despreading together, can increase by a same hardware resource of cover by the method for parallel expansion and realize.
The resource of the digital circuit that the function of above-mentioned realization multi path despreading expends is more.Each bar despreading branch road all need expend a lot of shift registers in order to finish the integration cumulative process.By with upper type, if be 4 times of speed and through four bit quantizations through the data rate behind the A/D, needing the multipath number of despreading is 4, and the length of frequency expansion sequence is 32, and the demodulation of each channel needs 72 registers at least so.When the number of channel that needs demodulation and multipath number increase, the number of register also will increase in proportion.For the quantity of the register that reduces use, can use RAM to replace register to finish the process that despreading adds up.Like this, the despreading of a channel just all will be used two RAM, and the use amount of RAM is too many.
Summary of the invention
The object of the present invention is to provide a kind of multi path despreading method of spread spectrum communication system, it can effectively utilize the resource of register and RAM, has saved the hardware resource of realizing required digital circuit.
To achieve these goals, the present invention, it is a kind of multi path despreading method of spread spectrum communication system, it is realized by following method: will quantize through mould/number conversion circuit respectively from the data of n channel, then being kept in each corresponding data storage through the data after quantizing, search for according to multipath receiver afterwards, the peak value of the multipath that traces into and the value of multipath delay, after reading the multipath data of n channel by storage control section control from the diverse location of each data storage, carry out this multi path despreading, n is a natural number, it is characterized in that: above-mentioned storage control section control from the order of the k bar multipath data flow that the diverse location of each data storage is read is: the data of preceding several chips of the 0th multipath, article 1, the data of preceding several chips of multipath, .... the data of preceding several chips of k bar multipath, k is a natural number; Article 0, the data of several chips that continue of the data of several chips that continue of multipath, the 1st multipath .... the data of several chips that continue of k bar multipath; ...., described multi path despreading is divided into following steps to carry out: at first carry out first despreading, the multipath data flow that n the channel that above-mentioned order is arranged walks abreast is after the frequency expansion sequence with this locality generation multiplies each other respectively, several chips adds up before finishing separately, the data flow that multipath data after afterwards several chips of each correspondence of n channel being added up walk abreast through formation m road after the data recombination (m＜n, and be natural number); Next carries out the secondary despreading and adds up, the data flow that above-mentioned m road is parallel, through adding up and data recombination after form j circuit-switched data stream (j＜m, and be natural number); Moreover carry out repeatedly despreading and add up, constantly repeat above-mentioned secondary despreading and add up, to form the data flow of less branch road; At last, the multi path despreading data of n channel of output.
The multi path despreading branch multistep of above-mentioned spread spectrum communication system is carried out suddenly, the first despreading process can use less resource to finish pre-cumulative process, and reduce the data rate on each each road of channel, make through each circuit-switched data behind the first despreading through despreading that can shared back level after data recombination unit that adds up.Repeatedly despreading adds up and uses RAM to replace register to finish adding up of despreading in addition.So data can make the shared RAM at different levels of multiplex data stream add up through behind the first despreading, the utilance height of RAM has been saved the resource that realizes.
The present invention is further illustrated below in conjunction with embodiments of the invention and accompanying drawing.
Description of drawings
Fig. 1 is the multi path despreading procedure chart of existing a kind of spread spectrum communication system;
Fig. 2 is the multi path despreading procedure chart of a kind of embodiment of the present invention.
Embodiment
Suppose that through the data rate behind the A/D also be 4 times of speed and through four bit quantizations, needing the multipath number of despreading is 4, the length of frequency expansion sequence is 32, as shown in Figure 2, when n=2, the i.e. despreading schematic diagram of the I of two channels, Q two-way, the method that reads the multipath data from data storage cell is as follows:
The data flow that P1, P2, P3, P4 are ordered all is the data of reading from data storage cell, and they belong to the I of two channels, the data on Q road respectively.The data arrangement of these points is followed successively by: the data f0d0 of preceding 4 (0 ~ 3) chip of the 0th multipath, f0d1, f0d2, f0d3, article 1, the data f1d0 of preceding 4 (0 ~ 3) chip of multipath, f1d1, f1d2, f1d3, article 2, the data f2d0 of preceding 4 (0 ~ 3) chip of multipath, f2d1, f2d2, f2d3, article 3, the data f3d0 of preceding 4 (0 ~ 3) chip of multipath, f3d1, f3d2, f3d3, ...., article 0, the data f0d4 of back 4 (4 ~ 7) chip that continue of multipath, f0d5, f0d6, f0d7, article 1, the data f1d4 of back 4 (4 ~ 7) chip that continue of multipath, f1d5, f1d6, f1d7, article 2, the data f2d4 of back 4 (4 ~ 7) chip that continue of multipath, f2d5, f2d6, f2d7, article 3, the data f3d4 of back 4 (4 ~ 7) chip that continue of multipath, f3d5, f3d6, f3d7 .....
According to this data arrangement, these data flow are at first passed through the first despreading unit after multiplying each other with frequency expansion sequence PNI and PNQ, finish adding up of four chip.Multipath data after afterwards the I of two channels, Q road 4chip being added up are passed through after the data recombination and are become the circuit-switched data stream at P5 point place, finish the process of multi path despreading after this circuit-switched data process secondary despreading adds up.The data of last P6 point output are the data interlace arrangements behind the multi path despreading on two channel I, Q road.
Can see from the process that realizes, data rate after the data rate of four demodulation branch roads of two channels (comprising I, Q two-way) after adding up through first despreading quantizes than A/D has reduced by four times, just can be arranged in circuit-switched data stream to this four circuit-switched data by flowing water, thereby make can shared secondary despreading the add up structure of unit of this four circuit-switched data by data recombination.
In sum, if through the data after the A/D quantification all is 4 bits, the number of multipath all is 4, the length of frequency expansion sequence is 32 words, on the structure of Fig. 2 as can be seen, adder and the register that the unit uses that add up in advance all is 6 bits, and the despreading adder of using that adds up is 9 bits, has used the adder of 33 bits, 48 registers and a RAM altogether.The length of each shift register of Fig. 1 is 4, and width is 9 bits, and the figure place of each adder all is 9 bits, shared adder and 144 registers of 36 bits; If use a RAM to replace the register resources of a certain despreading branch road, yet need 108 registers again.Can it is evident that according to above comparison digital circuit resource that the implementation method of the despreading that this patent proposes uses is all far fewer than existing implementation.
First despreading reduces the speed of each circuit-switched data, make multichannel data can be shared the resource of a cover secondary despreading, realize used resource thereby reduce.
The structure of above-mentioned two step despreadings, according to this thought, can be generalized to and use three despreadings, four despreadings, ... the structure of despreading repeatedly, in the prime despread unit, use less resource to finish first despreading, and the reduction data rate, make more multi channel despreading can be shared the resource of back level despread unit, improved the utilance of resource.
Claims (1)
1. the multi path despreading method of a spread spectrum communication system, realize by following step:
To quantize through mould/number conversion circuit respectively from the data of n channel, then being kept in each corresponding data storage through the data after quantizing, afterwards according to the peak value of multipath receiver search, the multipath that traces into and the value of multipath delay, after reading the multipath data of n channel by storage control section control from the diverse location of each data storage, carry out multi path despreading, n is a natural number, it is characterized in that:
Above-mentioned storage control section control from the order of the k bar multipath data flow that the diverse location of each data storage is read is:
Article 0, the data of preceding several chips of the data of preceding several chips of multipath, the 1st multipath, until the data of preceding several chips of k bar multipath, k is a natural number;
Article 0, the data of several chips that continue of the data of several chips that continue of multipath, the 1st multipath are until the data of several chips that continue of k bar multipath;
The data of reading each multipath successively according to above order are up to this time despreading end cycle;
Described multi path despreading is divided into following steps to carry out:
At first, first despreading
The multipath data flow that n the channel that above-mentioned order is arranged walks abreast is after the frequency expansion sequence with this locality generation multiplies each other respectively, several chips adds up before finishing separately, multipath data after afterwards several chips of each correspondence of n channel being added up are through forming the parallel data flow in m road after the data recombination, m＜n, and be natural number;
Secondly, the secondary despreading adds up
The data flow that above-mentioned m road is parallel, through adding up and data recombination after form j circuit-switched data stream, j＜m, and be natural number;
Moreover repeatedly despreading adds up
Constantly repeat above-mentioned secondary despreading and add up, to reduce the data flow of branch road;
At last, the multi path despreading data of n channel of output.
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| CNB001194429A CN1160868C (en) | 2000-07-11 | 2000-07-11 | Multi path despreading method for spread spectrum communication system |
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| CNB001194429A CN1160868C (en) | 2000-07-11 | 2000-07-11 | Multi path despreading method for spread spectrum communication system |
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| CN105763295B (en) * | 2014-12-19 | 2019-09-13 | 深圳市中兴微电子技术有限公司 | A kind of data processing method and device |
| CN107015063B (en) * | 2017-03-21 | 2019-08-30 | 中国科学院国家天文台 | Wide band multi-channel Correlation receiver and method of reseptance |
| CN113346968B (en) * | 2021-03-02 | 2022-09-23 | 西安电子科技大学 | Multipath time delay estimation method based on Lasso problem |
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