CN1110921C - Method and device of realizing code synchronization in spread spectrum communication - Google Patents
Method and device of realizing code synchronization in spread spectrum communication Download PDFInfo
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- CN1110921C CN1110921C CN99119488A CN99119488A CN1110921C CN 1110921 C CN1110921 C CN 1110921C CN 99119488 A CN99119488 A CN 99119488A CN 99119488 A CN99119488 A CN 99119488A CN 1110921 C CN1110921 C CN 1110921C
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Abstract
The present invention relates to a method and a device for realizing code synchronization in spread spectrum communication. The method comprises the following steps: making input signals orderly enter a shift memory; using control information obtained by a coarse synchronization module to determine the initial address of a reading pointer of the shift memory; utilizing an advancing pointer and a lagging pointer to obtain the address adjustment amount of the reading pointer; using the initial address and the address adjustment amount to generate the address of the reading pointer; adjusting the address of the reading pointer of the shift memory according to the address. The present invention can realize synchronization between the input signals and local codes, and make the whole searching and tracking system use the same clock. The realization of the present invention is visual and simple.
Description
The present invention relates to realize method and the device that sign indicating number is synchronous in a kind of spread spectrum communication, especially relate to a kind of shift memory pointer that utilizes and make synchronous method and the implement device thereof of realization between input signal and local code.
In the spread spectrum communication field, make input signal and local code realize that synchronous prior art mainly contains two kinds: a kind of is with the error signal control voltage controlled oscillator through loop filtering, the output of voltage controlled oscillator as local code generator clock, referring to US00536550A, Nov.15,1994, " INITIAL SYNCHRONIZATION AND TRACKING CIRCUITS FORSPREAD SPECTRUM RECEIVES ".Another kind is that local code generator clock is constant, uses the sampling clock of the output of voltage controlled oscillator as input signal, referring to Jia-Chin LIN
+AndLin-Shan LEE
+" A Modified Code Tracking Loop for Direct-SequenceSpread-Spectrum Systems on Frequency-Selective Fading Channels ", IEICETRANS.COMMUN., Vol.E80-B, NO.7, JULY1997.
Fig. 1 realizes the technical schematic diagram of tracking by adjusting local code generator clock in the prior art.As shown in Figure 1, advanced code 17 that input signal 11 and local code generator 10 produce and hysteresis sign indicating number 18 are respectively after multiplier 1 and 2 multiplies each other, through correlator 3 and 4, pass through squarer 5 and 6 again, coherent signal 12 and 13 after obtaining square, anti-phase addition in adder, obtain error signal 14, error signal 14 obtains through low pass error signal 15 after level and smooth through loop filters 8, error signal 15 control voltage controlled oscillator clockings 16, clock signal 16 is as the clock of local code generator 10.According to the relevant phase characteristic of sign indicating number, utilize error signal 15 compressions and expansion clock signal 16, make that the spreading code in local code and the input signal is synchronous.
In Fig. 1, tracking means utilizes the auto-correlation function characteristic of sign indicating number, finishes the task of tracking according to the principle of delay lock loop.The leading sequence of the real-time sequence that produces with the local code generator is relevant with input signal respectively with late sequences, suppose the corresponding t constantly of real-time sequence of local code generator, the corresponding t+ △ constantly of then leading sequence, the corresponding t-△ constantly of late sequences, wherein the value size of △ is generally 0 to 1 chip period.In order to remove the influence of data-modulated, carrier residual phase place etc., signal after relevant will carry out square, the correlation that deducts leading sequence with the correlation of late sequences obtains error signal then, error signal has very big shake because of noisy influence, so need to carry out smoothing processing through loop filter, loop filter is a low pass filter, error signal after level and smooth is as control voltage of voltage-controlled oscillator, when error signal was zero, voltage controlled oscillator produced the pulse signal of a fixed frequency; When error signal was non-vanishing, voltage controlled oscillator will produce the pulse signal that frequency increases and frequency reduces along with the polarity and the size of error signal, and this pulse signal is as the read pulse of local code generator.Suppose that when local code hysteresis input signal error signal is for just, the output frequency of voltage controlled oscillator increases, the pulse frequency that produces increases, the reading speed of local code is accelerated, and makes the original local code that lags behind catch up with input signal gradually, till local code and input signal are synchronous; When the leading input signal of local code, error signal is for negative, and the output frequency of voltage controlled oscillator reduces, the pulse frequency that produces reduces, the reading speed of local code slows down, and makes original leading local code be transfused to signal gradually and catch up with, till local code and input signal are synchronous.
Fig. 2 realizes the technical schematic diagram of tracking by adjusting the receiving terminal sampling clock in the prior art.In Fig. 2, advanced code 17 that input signal 11 and local code generator 10 produce and hysteresis sign indicating number 18 are respectively after multiplier 1 and 2 multiplies each other, through correlator 3 and 4, pass through squarer 5 and 6 again, coherent signal 12 and 13 after obtaining square, anti-phase addition in adder, obtain error signal 14, error signal 14 obtains through low pass error signal 15 after level and smooth through loop filters 8, error signal 15 control voltage controlled oscillator clockings 16, clock signal 16 is as input signal 11 sampling clocks.According to the relevant phase characteristic of sign indicating number, utilize error signal 15 compressions and expansion clock signal 16, make that spreading code and the local code in the input signal is synchronous.
These two kinds of trackings of the prior art are respectively by adjusting the local code clock and adjusting the input signal sampling clock and realize that sign indicating number synchronously, but these two kinds of methods all need to change clock, make that timing relationship becomes complicated in the receiver, and implement also relatively difficulty.
The objective of the invention is to overcome the shortcoming of above-mentioned prior art, provide and realize method and the implement device thereof that sign indicating number is synchronous in a kind of spread spectrum communication, the present invention can utilize the shift memory pointer realize between input signal and local code synchronously, make whole system use same clock, and implement more simple.
Realize the method that sign indicating number is synchronous in the spread spectrum communication of the present invention, it may further comprise the steps:
(1) make input signal enter shift memory successively;
(2) control information that obtains with thick synchronization module determines the initial address of shift memory read pointer;
(3) data that the leading read pointer of shift memory and hysteresis read pointer are read are relevant with local code, obtain the address adjustment amount of shift memory read pointer;
(4) initial address is entered read pointer controller with the address adjustment amount, produce the address of shift memory read pointer;
(5) address that produces according to step (4) makes read pointer controller adjust the address of shift memory read pointer, makes that input signal and local code that real-time read pointer is read are synchronous.
Wherein step (3) further may further comprise the steps:
(1) the leading pointer of shift memory and hysteresis pointer and local code are multiplied each other respectively in multiplier;
(2) two coherent signals after obtaining square through correlator and squarer respectively then;
(3) the anti-phase addition in adder of two coherent signals is obtained error signal;
(4) error signal is carried out smoothing processing through loop filter again;
(5) error signal after smoothing processing is passed through the accumulator accumulation process again.
Wherein in the step (4), the address of shift memory read pointer equals initial pointer and adds the address adjustment amount.
Wherein the concrete steps of adjusting in the step (5) are: when the address adjustment amount is non-vanishing, the read pointer of shift memory just moves on to corresponding position according to initial address and address adjustment amount, the distance that the size decision read pointer of initial pointer and address adjustment amount sum moves, the direction that its positive and negative decision read pointer moves promptly is to reach or move backward; When the address adjustment amount was zero, the address of the read pointer of shift memory remained unchanged.
Realize the device that sign indicating number is synchronous in the spread spectrum communication of the present invention, comprise local code generator 10, multiplier 1,2, correlator 3,4, squarer 5,6, loop filter 8, shift memory 28, read pointer controller 23, thick synchronization module 21 and accumulator 19, the input termination input signal 11 of shift memory 28, the output of its leading read pointer 25 connects multiplier 1 successively, correlator 3, squarer 5 and adder 7, the output 27 of its hysteresis read pointer connects multiplier 2 successively, correlator 4, squarer 6 and adder 7, the output of adder 7 be T-Ring path filter 8 and accumulator 19 successively; The input 31 and 32 of read pointer controller connects the output of thick synchronization module 21 and accumulator 19 respectively, and its output 30 connects the control input end 24 of shift memory.
Search tracking and the device thereof that utilizes the shift memory pointer of the present invention, the initial position of the phase information control shift memory read pointer that thick synchronization module is obtained, tracking means can accurately be controlled read the drift that hour hands are followed the tracks of input signal, make input signal and local code realize making whole system use same clock synchronously.And when the present invention is used for pectination (RAKE) receiver, merge more simple.
Below in conjunction with accompanying drawing the search tracking of shift memory pointer and the device thereof of utilizing of the present invention described in further detail.
Fig. 1 realizes the technical schematic diagram of tracking by adjusting local code generator clock in the prior art;
Fig. 2 realizes the technical schematic diagram of tracking by adjusting the receiving terminal sampling clock in the prior art;
Fig. 3 is circuit theory diagrams of realizing the search tracking with memory pointer of the present invention;
Fig. 4 is the schematic diagram of Multipath searching during band spread receiver RAKE merges.
In Fig. 3, shift memory 28 has a write pointer, one group of read pointer: leading read pointer 25, real-time read pointer 26 and hysteresis read pointer 27 are respectively applied for the anticipating signal, live signal and the delay signal that read input signal.When needs were followed the tracks of a plurality of random sequence simultaneously, shift memory can have many group read pointers.
As shown in Figure 3, input signal 11 enters shift memory 28 successively, and shift memory 28 makes input signal 11 constantly be shifted under the driving of clock.According to the required precision of tracking means, the sample rate of input signal can be 2 times of spreading rates or higher.
Enter input signal 11 constantly displacement under the driving of clock of shift memory 28, when not having error signal, it is motionless that the write pointer of shift memory and read pointer keep, and just the address of pointer is constant.When error signal, it is motionless that write pointer still keeps, but read pointer just moves on to corresponding position according to thick synchronically controlling information or error adjustment information, the distance that the size decision read pointer of thick synchronizing information or error adjustment information moves, the direction that its positive and negative decision read pointer moves promptly is to reach or move backward.When read pointer moved, the relativeness of three pointers remained unchanged in one group of read pointer, that is to say that three pointers do same moving.
The initial position (being initial address) of the control information 22 decision shift memory read pointers that thick synchronization module 21 obtains after initial position is determined, utilizes the leading read pointer 25 of shift memory and hysteresis read pointer 27 to follow the tracks of.In the leading 25 leading moment of read pointer 26 △ in real time of read pointer, hysteresis read pointer 27 lags behind real-time read pointer 26 △ constantly, and the magnitude range of △ is between 0 to 1 chip period.The local code 29 that number that leading read pointer 25 and hysteresis read pointer 27 are read and local code generator 10 produce multiplies each other in multiplier 1 and 2, then through correlator 3 and 4 and the coherent signal 12 and 13 of squarer 5 and 6 after obtaining square, the two anti-phase addition in adder 7 obtains error signal 14, error signal 15 after obtaining smoothly through loop filter 8, error signal 15 produces control signal 20 after adding up through accumulator 19, and control signal 20 comprises the error adjustment information.The effect of accumulator is equivalent to the integrator in the analog circuit, is exactly in order to reduce the adjustment amount that error need be done through the error signal after add up (integration).Control signal 20 enters read pointer controller 23 with the control information 22 that thick synchronization module 21 produces, and adjusts by the read pointer of 23 pairs of shift memories of read pointer controller.
The address that read pointer controller 23 produces the shift memory read pointer, the foundation of generation are that the control information that slightly provides synchronously adds the error adjustment information that tracking means provides.Concrete adjustment process is: thick synchronization module provides the initial address of read pointer, tracking means provides the error adjustment information, the error adjustment information is exactly the address adjustment amount of read pointer, and the address of shift memory read pointer just equals initial address and adds the address adjustment amount like this.Synchronous by input signal and local code that the address of adjusting the shift memory read pointer just can make real-time read pointer read, and the clock of local code generator need not adjust.The adjustment step-length of tracking means can be chip period 1/2nd or littler, tracking means just can be on thick synchronous basis like this, the drift of accurate tracking input signal changes.
Further concrete application the of the present invention is that the search to multipath was followed the tracks of during band spread receiver RAKE merged, the tracking means utilization tracking means as shown in Figure 3 in every footpath, and the shift memory among Fig. 3 adopts the form of Fig. 4.Shift memory has the output of many group read pointers, has the tracking means of similar number corresponding with it corresponding to the group number of read pointer, and output of each group read pointer all is the input of an independent tracking means, the footpath that each tracking means correspondence will be followed the tracks of.Multipath searching be exactly among Fig. 3 thick synchronously, the sample rate of input signal is 4 times of spreading rates.
Multipath searching is promptly at first found out the initial position of the corresponding shift memory read pointer in each footpath, as shown in Figure 4, the leading read pointer in every footpath is read real-time pointer one half chip period in advance among Fig. 4, the hysteresis read pointer real-time read pointer one half chip period that lags behind, the length of shift memory select to want to guarantee Multipath searching to the corresponding maximum pointer offset in each footpath can not shift out the scope of memory, the step-length of search is an one half chip period, each frame update of Multipath searching is once distributed to each footpath to the pointer position of the several most powerful paths that search out.In every footpath, because variation, the variation of mobile environment and the influence of various interference of channel delay, drift all can take place in each footpath, so in each footpath, a tracking means is arranged all, finely tune the position of the corresponding reading of the shift memory as shown in Figure 4 pointer in each footpath by tracking means, follow the drift in footpath, reach tracking every footpath.The data read rates of demodulating unit is one times of spreading rate.Because the adjustment of every footpath time delay is carried out in shift memory, so the data in every footpath all are synchronous, when RAKE merges, can directly merge like this, and whole receiver to be with a unified clock, relation simply is convenient to realization.
Though the present invention is with most preferred embodiment openly as above, yet be not in order to qualification the present invention, any those skilled in the art, modifications or improvements on basis of the present invention all do not exceed scope of the present invention.
Claims (8)
1. realize the method that sign indicating number is synchronous in a spread spectrum communication, it is characterized in that, may further comprise the steps:
(1) make input signal enter shift memory successively;
(2) control information that obtains with thick synchronization module determines the initial address of shift memory read pointer;
(3) data that the leading read pointer of shift memory and hysteresis read pointer are read are relevant with local code, obtain the address adjustment amount of shift memory read pointer, specifically comprise:
(a) the leading pointer of shift memory and hysteresis pointer and local code are multiplied each other respectively in multiplier;
(b) two coherent signals after obtaining square through correlator and squarer respectively then;
(c) the anti-phase addition in adder of two coherent signals is obtained error signal;
(4) initial address is entered read pointer controller with the address adjustment amount, produce the address of displacement storage Ic device read pointer, in this step, the address of shift memory read pointer equals initial pointer and adds the address adjustment amount;
(5) address that produces according to step (4) makes read pointer controller adjust the address of shift memory read pointer, makes that input signal and local code that real-time read pointer is read are synchronous,
And in the leading moment of pointer △ in real time of described leading pointer, the hysteresis pointer lags behind real-time pointer △ constantly, and the magnitude range of described △ is between 0 to 1 chip period.
2. realize the method that sign indicating number is synchronous in the spread spectrum communication according to claim 1, it is characterized in that described error signal is carried out smoothing processing through loop filter.
3. realize synchronous method in the spread spectrum communication according to claim 2, it is characterized in that the error signal after smoothing processing is passed through the accumulator accumulation process again.
4. realize the method that sign indicating number is synchronous in the spread spectrum communication according to claim 1, it is characterized in that, the concrete steps of adjusting in the described step (5) are: when the address adjustment amount is non-vanishing, the read pointer of shift memory just moves on to corresponding position according to initial address and address adjustment amount, the distance that the size decision read pointer of initial pointer and address adjustment amount sum moves, the direction that its positive and negative decision read pointer moves promptly is to reach or move backward; When the address adjustment amount was zero, the address of the read pointer of shift memory remained unchanged.
5. realize the method that sign indicating number is synchronous in the spread spectrum communication according to claim 1, it is characterized in that the sample rate of described input signal is 2 times of spreading rates or higher.
6. realize the method that sign indicating number is synchronous in the spread spectrum communication according to claim 1, it is characterized in that, the step-length of adjusting in the described step (5) be chip period 1/2nd or still less.
7. realize the method that sign indicating number is synchronous in the spread spectrum communication according to claim 1, it is characterized in that, described method can be used in the Multipath searching in the band spread receiver RAKE merging, promptly be by finely tuning the position of every pairing shift memory read pointer in footpath, follow the drift in footpath, reach tracking, the input signal in every footpath and local code are all realized synchronously every footpath.
8. realize the device that sign indicating number is synchronous in a spread spectrum communication, comprise local code generator (10), multiplier (1,2), correlator (3,4), squarer (5,6) and loop filter (8), it is characterized in that, it also comprises shift memory (28), read pointer controller (23), be used to produce the thick synchronization module (21) and the accumulator (19) of control information, the input termination input signal (11) of described shift memory (28), the output of the leading read pointer (25) that it is used to follow the tracks of in advance connects multiplier (1) successively, correlator (3), squarer (5) and adder (7), the output (27) of its hysteresis read pointer of following the tracks of of being used to lag behind connects multiplier (2) successively, correlator (4), squarer (6) and adder (7), the output of adder (7) be T-Ring path filter (8) and accumulator (19) successively; The input of read pointer controller (31) and (32) connect the output of thick synchronization module (21) and accumulator (19) respectively, its output auspicious (30) connects the control input end (24) of shift memory, and the output of local code generator (10) links to each other with the input of multiplier (1,2) respectively.
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