CN101795155A - Method and device for synchronizing wireless communication system - Google Patents

Abstract

The invention discloses a method and a device for synchronizing a wireless communication system. The method comprises the following steps: receiving a sequence, determining a search interval according to a CRC verification result, and only calculating complex related power values of the search interval; and comparing the complex related power values of the search interval, taking a sequence position corresponding to the maximum complex related power value as a synchronous position, and demodulating the whole frame sequence by using the position as a reference point, wherein the CRC verification result is determined by performing CRC verification on the data demodulated after the last synchronous operation. Compared with the traditional synchronous scheme, the method and the device greatly reduce the length of the search interval so as to greatly reduce the calculation overhead. Because of the reduction of the search range, the synchronous probability is greatly improved so that the wireless communication system can adapt to the condition of low signal-to-noise ratio.

Description

The method for synchronous of wireless communication system and device

Technical field

The present invention relates to wireless communication technology field, relate in particular to a kind of method for synchronous and device of wireless communication system.

Background technology

In wireless communication system, be the basis of all communications synchronously, have only accurately synchronously could guarantee correct demodulation performance.In existing communication system, synchronized algorithm mostly is to utilize local synchronizing sequence and receiving sequence to carry out multiple correlation to seek peak-peak, and maximal peak point is judged to synchronous points.The schematic diagram of this synchronization scenario is referring to Fig. 1.Its main process comprises: step 1, and sequence buffer receiving sequence, wherein, sequence length is the length of one frame+synchronizing sequence; Step 2, complex correlator is slided sequence and local synchronizing sequence relevant, and calculates every bit related power value; Step 3, the related power value that the decision device comparison is had a few as sync bit, is sent into the position of maximal correlation power correspondence demodulator and is carried out demodulation with this sync bit whole frame sequence of naming a person for a particular job as a reference then.

In wireless communication system, general terminal all moves, or even high-speed mobile, for example, the maximum relative speed of portable terminal can reach 5000km/h in the airborne communication system.In this case, for a certain specific receiving terminal, the sync bit of the different subframes of same launch terminal can be different along with relatively moving of transceiver terminal, so, need carry out at each received frame of launch terminal synchronously, this just needs to reuse synchronized algorithm, just, all whole receiving sequences is searched at each frame of launch terminal.Because each frame all is to the full sequence correlation computations of sliding, so this mode computation complexity is higher, in addition, because search sequence is longer, under low signal-to-noise ratio (signal power is less) situation, the related power point of asynchronous position is judged to the probability (false alarm probability) of sync bit and probability (false dismissal probability) that sync bit does not detect all can increase, and causes synchronous probability lower.

Summary of the invention

The invention provides a kind of method for synchronous and device of wireless communication system, can realize low amount of calculation, high synchronous probability, be particularly suitable for the scene that receiving terminal moves.

For this reason, the embodiment of the invention adopts following technical scheme:

A kind of method for synchronous of wireless communication system comprises: receiving sequence, and determine the region of search according to CRC (CyclicalRedundancy Check, CRC) check results, and only calculate the multiple correlation performance number of the region of search; The multiple correlation performance number in comparison search interval, with the sequence location of maximum multiple correlation performance number correspondence as sync bit, with this position as whole frame sequence being carried out demodulation with reference to point; Wherein, described CRC check result to last simultaneous operation after demodulated data carry out CRC check and determine.

Wherein, describedly determine that according to the CRC check result region of search comprises:, come to determine the region of search at interval according to the maximum relative velocity and the frame emission of launch terminal and receiving terminal if the CRC check is correct; If CRC check mistake is then determined the region of search according to errors number.

When CRC checks when correct, determine the region of search by following formula:

[search_min，search_max]＝[pos_last-L _max，pos_last+L _max]

Wherein, pos_last is last sync bit, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\·T_{\mathrm{interval}}}{C\·T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

When the CRC check mistake, determine the region of search by following formula:

$\mathrm{search}\_\min =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}-(n+1)L_{\max },& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }\&GreaterEqual;0\\ 0,& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }<0\end{array}\right.$

$\mathrm{search}\_\max =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}+(n+1)L_{\max },& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }\&le;L-1\\ L-1,& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }>L-1\end{array}\right.$

Wherein, pos_last is last sync bit, and n is the wrong continuously number of times of CRC check, and L is the length of multiple correlation value cor, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

Determine that according to the region of search [search_min, search_max] length of search sequence is:

L _search＝search_max-search_min

The multiple correlation performance number of the described region of search is according to L _SearchSize determine.

A kind of synchronizer of wireless communication system, comprise sequence buffer, complex correlator, decision device and demodulator, also comprise the CRC check ultramagnifier, wherein: described CRC check ultramagnifier, determine this CRC check result in subsynchronous according to the CRC check of demodulating data after the last simultaneous operation; Described complex correlator, the CRC check result of the last back synchronously demodulating data that provides according to the CRC check ultramagnifier determines region of search that this is subsynchronous, and only calculates the multiple correlation performance number of the region of search at the sequence that described sequence buffer provides; Described decision device, the multiple correlation performance number in comparison search interval, with the sequence location of maximum multiple correlation performance number correspondence as sync bit, and inform described demodulator with this position as whole frame sequence being carried out demodulation with reference to point.

Described complex correlator comprises the correct corresponding subelement of verification, the corresponding subelement of check errors and multiple correlation performance number computation subunit, wherein, the correct corresponding subelement of described verification, check when correct at CRC, come to determine the region of search at interval according to the maximum relative velocity and the frame emission of launch terminal and receiving terminal; The corresponding subelement of described check errors when the CRC check is wrong, is then determined the region of search according to errors number.

The correct corresponding subelement of described verification, determine the region of search by following formula:

[search_min，search_max]＝[pos_last-L _max，pos_last+L _max]

Wherein, pos_last is last sync bit, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

The corresponding subelement of described check errors, determine the region of search by following formula:

$\mathrm{search}\_\min =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}-(n+1)L_{\max },& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }\&GreaterEqual;0\\ 0,& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }<0\end{array}\right.$

$\mathrm{search}\_\max =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}+(n+1)L_{\max },& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }\&le;L-1\\ L-1,& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }>L-1\end{array}\right.$

Wherein, pos_last is last sync bit, and n is the wrong continuously number of times of CRC check, and L is the length of multiple correlation value cor, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

Described multiple correlation performance number computation subunit determines that according to the region of search [search_min, search_max] length of search sequence is:

L _search＝search_max-search_min

And according to L _SearchSize determine the multiple correlation performance number of the described region of search.

As seen, the present invention adopts the CRC check result to indicate synchronized result, and determines the region of search that this is subsynchronous according to correctness, and traditional search whole sequence length is changed into smaller interval of search.When the CRC check mistake, the present invention expands the region of search of last time to be twice, and the bound that surpasses former search sequence up to the region of search just no longer enlarges.

To sum up, the present invention has reduced the length of the region of search greatly than the conventional synchronization scheme, thereby has also just reduced computing cost greatly.Because reducing of hunting zone also improved synchronous probability greatly, makes wireless communication system can adapt to the situation of low signal-to-noise ratio.

Description of drawings

Fig. 1 is a prior art wireless communication system synchronization scenario schematic diagram;

Fig. 2 is a wireless communication system synchronization scenario schematic diagram of the present invention;

Fig. 3 is a wireless communication system synchronization method flow chart of the present invention.

Embodiment

For certain terminal A, if particular terminal B is correct synchronously when present frame receiving terminal A data, when then arriving next frame emission of terminal A, terminal B only need search for one near the sync bit in last time and get final product among a small circle, based on above-mentioned analysis, the present invention proposes a kind of wireless communication system synchronization method, can realize low amount of calculation, high synchronous probability, is particularly suitable for the scene that receiving terminal moves.

Referring to Fig. 2, be wireless communication system synchronization scenario schematic diagram of the present invention, compare with existing scheme, the present invention program has increased the CRC check feedback module, complex correlator can be determined the size of the region of search that this is subsynchronous according to last hyposynchronous CRC check result, reducing search length, thereby can reduce the amount of calculation of complex correlator, increase synchronous probability.

Referring to Fig. 3, the method for synchronous flow chart for wireless communication system of the present invention comprises:

S301: sequence buffer receiving sequence, offer complex correlator behind the buffer memory, wherein, the length of the sequence that receives is the length of one frame+synchronizing sequence;

S302: complex correlator is determined the region of search according to the CRC check result, and only calculates the multiple correlation performance number of the region of search, and offers decision device;

Wherein, the CRC check ultramagnifier is that the check results that demodulator institute demodulated data after the last synchronizing process is carried out after CRC deciphers and will decipher is sent to complex correlator.

Wherein, the computational process of multiple correlation performance number is: complex correlator is slided sequence in the region of search and local synchronizing sequence relevant, determines the related power value of the region of search then.

S303: the multiple correlation performance number in decision device comparison search interval as sync bit, sends to the position of maximal correlation performance number correspondence demodulator and carries out demodulation with this position whole frame sequence of naming a person for a particular job as a reference then.

Below the embodiment of the invention is described in detail.

The operation principle of each module is as follows:

(1) complex correlator

Complex correlator of the present invention increases to some extent with respect to the complex correlator function in traditional synchronization scenario: do not obtain when synchronous complex correlator of the present invention and traditional similar with launch terminal at receiving terminal; Receiving terminal and launch terminal synchronously after, complex correlator is different, is described in detail as follows:

Before not synchronous

Assumes synchronization sign indicating number SYNC is $S=(s_0,s_1,...,s_{L_{\mathrm{sync}}-1}),$ Sequence to be searched is e=(e ₀, e ₁..., e _L-1), then the region of search is:

[search_min，search_max]＝[0，L-1]

... ... .. formula 1

Wherein the region of search is that the maximum communication distance (the frame protection at interval) that allows according to network determines.

S is mended 0 to L obtain S_fft, it is as follows then e and S_fft to be carried out the multiple correlation computing:

cor＝IFFT(FFT(e)·*conj(FFT(S_fft)))

... ... .. formula 2

Wherein conj represents to get conjugation, " .* " expression sequence dot product, and cor length is L.

It is as follows to calculate related power power_cor:

power_cor _i＝|cor _i| ²，i＝0，1，…，L-1

... ... .. formula 3

Synchronously

A determines the region of search

● if the CRC check is correct, then illustrate for same launch terminal, receiving terminal on this launch terminal a frame be correct synchronously, at this moment only need come at interval to determine that the region of search gets final product according to the maximum relative velocity and the frame emission of launch terminal and receiving terminal, method is as follows:

If the maximum relative velocity of launch terminal and receiving terminal is V, the light velocity is C, and the time of a chip is T _c, for same terminal, the largest interval of adjacent frame emission is T _Interval, then should the time interval in the pairing number of chips of ultimate range increment of launch terminal and receiving terminal:

$L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c}$

... ... formula 4

If last sync bit is pos_last, determine that then this region of search is:

[search_min，search_max]＝[pos_last-L _max，pos_last+L _max]

● if CRC check mistake is then determined the region of search according to errors number, method is as follows:

If the sync bit of last accurate synchronization is pos_last, the wrong continuously number of times of CRC check is n, and then this region of search is determined according to following rule:

$\mathrm{search}\_\min =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}-(n+1)L_{\max },& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }\&GreaterEqual;0\\ 0,& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }<0\end{array}\right.$

... ... formula 5

$\mathrm{search}\_\max =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}+(n+1)L_{\max },& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }\&le;L-1\\ L-1,& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }>L-1\end{array}\right.$

... ... formula 6

The b multiple correlation is calculated

The length that can be obtained search sequence by the region of search [search_min, search_max] is

L _search＝search_max-search_min

... ... formula 7

The multiple correlation algorithm can be according to L _SearchSize determine: if L _SearchLess, then can utilize the method for direct calculating correlation to calculate multiple correlation value cor in the region of search [search_min, search_max]; If L _SearchBigger, then can calculate cor according to the method for " not preceding synchronously ".Calculate multiple correlation power power_cor then.

(2) CRC check ultramagnifier

The CRC check ultramagnifier exactly with last time decoded CRC check result feed back in the complex correlator, how this operates the indication complex correlator in subsynchronous at this.

(3) decision device

Seek the maximal correlation performance number in the region of search [search_min, search_max], the position judgement that it is corresponding is sync bit pos_final.

Corresponding with said method, the present invention also provides a kind of synchronizer of wireless communication system, this device can pass through hardware, software or software and hardware combining to be realized, particularly, this device comprises sequence buffer, complex correlator, decision device and demodulator, especially, this device also comprises the CRC check ultramagnifier, below each module is introduced in detail:

The CRC check ultramagnifier is determined this CRC check result in subsynchronous according to the CRC check of demodulating data after the last simultaneous operation;

Complex correlator, the CRC check result of the last back synchronously demodulating data that provides according to the CRC check ultramagnifier determines region of search that this is subsynchronous, and only calculates the multiple correlation performance number of the region of search at the sequence that described sequence buffer provides;

Decision device, the multiple correlation performance number in comparison search interval, with the sequence location of maximum multiple correlation performance number correspondence as sync bit, and inform described demodulator with this position as whole frame sequence being carried out demodulation with reference to point.

Wherein, described complex correlator comprises the correct corresponding subelement of verification, the corresponding subelement of check errors and multiple correlation performance number computation subunit, wherein,

The correct corresponding subelement of verification is checked when correct at CRC, comes to determine the region of search at interval according to the maximum relative velocity and the frame emission of launch terminal and receiving terminal;

The corresponding subelement of check errors when the CRC check is wrong, is then determined the region of search according to errors number.

Particularly, the correct corresponding subelement of verification, determine the region of search by following formula:

[search_min，search_max]＝[pos_last-L _max，pos_last+L _max]

Wherein, pos_last is last sync bit, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

Particularly, the corresponding subelement of check errors, determine the region of search by following formula:

$\mathrm{search}\_\min =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}-(n+1)L_{\max },& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }\&GreaterEqual;0\\ 0,& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }<0\end{array}\right.$

$\mathrm{search}\_\max =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}+(n+1)L_{\max },& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }\&le;L-1\\ L-1,& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }>L-1\end{array}\right.$

Wherein, pos_last is last sync bit, and n is the wrong continuously number of times of CRC check, and L is the length of multiple correlation value cor, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

Particularly, multiple correlation performance number computation subunit determines that according to the region of search [search_min, search_max] length of search sequence is:

L _search＝search_max-search_min

And according to L _SearchSize determine the multiple correlation performance number of the described region of search.

As seen, the present invention adopts the CRC check result to indicate synchronized result, and determines the region of search that this is subsynchronous according to correctness, and traditional search whole sequence length is changed into smaller interval of search.When the CRC check mistake, the present invention expands the region of search of last time to be twice, and the bound that surpasses former search sequence up to the region of search just no longer enlarges.

To sum up, the present invention has reduced the length of the region of search greatly than the conventional synchronization scheme, thereby has also just reduced computing cost greatly.Because reducing of hunting zone also improved synchronous probability greatly, makes wireless communication system can adapt to the situation of low signal-to-noise ratio.

One of ordinary skill in the art will appreciate that, the process of the method for realization the foregoing description can be finished by the relevant hardware of program command, described program can be stored in the read/write memory medium, and this program is carried out the corresponding step in the said method when carrying out.Described storage medium can be as ROM/RAM, magnetic disc, CD etc.

The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (10)

1. the method for synchronous of a wireless communication system is characterized in that, comprising:

Receiving sequence, and determine the region of search according to the CRC check result, and only calculate the multiple correlation performance number of the region of search;

The multiple correlation performance number in comparison search interval, with the sequence location of maximum multiple correlation performance number correspondence as sync bit, with this position as whole frame sequence being carried out demodulation with reference to point;

Wherein, described CRC check result to last simultaneous operation after demodulated data carry out CRC check and determine.

2. according to the described method of claim 1, it is characterized in that, describedly determine that according to the CRC check result region of search comprises:

As if the CRC check correctly, maximum relative velocity and the frame emission according to launch terminal and receiving terminal comes to determine the region of search at interval;

If CRC check mistake is then determined the region of search according to errors number.

3. according to the described method of claim 2, it is characterized in that, when CRC checks when correct, determine the region of search by following formula:

[search_min，search_max]＝[pos_last-L _max，pos_last+L _max]

Wherein, pos_last is last sync bit, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

4. according to the described method of claim 2, it is characterized in that, when the CRC check mistake, determine the region of search by following formula:

$\mathrm{search}\_\min =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}-(n+1)L_{\max ,}& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }\&GreaterEqual;0\\ 0,& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }<0\end{array}\right.$

$\mathrm{search}\_\max =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}+(n+1)L_{\max ,}& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }\&le;L-1\\ L-1,& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }>L-1\end{array}\right.$

Wherein, pos_last is last sync bit, and n is the wrong continuously number of times of CRC check, and L is the length of multiple correlation value cor, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

5. according to claim 3 or 4 described methods, it is characterized in that, determine that according to the region of search [search_min, search_max] length of search sequence is:

L _search＝search_max-search_min

The multiple correlation performance number of the described region of search is according to L _SearchSize determine.

6. the synchronizer of a wireless communication system comprises sequence buffer, complex correlator, decision device and demodulator, it is characterized in that, also comprises the CRC check ultramagnifier, wherein:

Described CRC check ultramagnifier is determined this CRC check result in subsynchronous according to the CRC check of demodulating data after the last simultaneous operation;

Described complex correlator, the CRC check result of the last back synchronously demodulating data that provides according to the CRC check ultramagnifier determines region of search that this is subsynchronous, and only calculates the multiple correlation performance number of the region of search at the sequence that described sequence buffer provides;

Described decision device, the multiple correlation performance number in comparison search interval, with the sequence location of maximum multiple correlation performance number correspondence as sync bit, and inform described demodulator with this position as whole frame sequence being carried out demodulation with reference to point.

7. according to the described device of claim 6, it is characterized in that described complex correlator comprises the correct corresponding subelement of verification, the corresponding subelement of check errors and multiple correlation performance number computation subunit, wherein,

The correct corresponding subelement of described verification is checked when correct at CRC, comes to determine the region of search at interval according to the maximum relative velocity and the frame emission of launch terminal and receiving terminal;

The corresponding subelement of described check errors when the CRC check is wrong, is then determined the region of search according to errors number.

8. according to the described device of claim 7, it is characterized in that the correct corresponding subelement of described verification is determined the region of search by following formula:

[search_min，search_max]＝[pos_last-L _max，pos_last+L _max]

Wherein, pos_last is last sync bit, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

9. according to the described device of claim 7, it is characterized in that the corresponding subelement of described check errors is determined the region of search by following formula:

$\mathrm{search}\_\min =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}-(n+1)L_{\max ,}& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }\&GreaterEqual;0\\ 0,& \mathrm{pos}\_\mathrm{last}-(n+1)L_{\max }<0\end{array}\right.$

$\mathrm{search}\_\max =\left\{\begin{array}{cc}\mathrm{pos}\_\mathrm{last}+(n+1)L_{\max ,}& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }\&le;L-1\\ L-1,& \mathrm{pos}\_\mathrm{last}+(n+1)L_{\max }>L-1\end{array}\right.$

Wherein, pos_last is last sync bit, and n is the wrong continuously number of times of CRC check, and L is the length of multiple correlation value cor, L _MaxThe pairing number of chips of ultimate range increment for launch terminal and receiving terminal: $L_{\max }=\frac{V\&CenterDot;T_{\mathrm{interval}}}{C\&CenterDot;T_c};$

Wherein, V is that the maximum relative velocity of launch terminal and receiving terminal is, C is the light velocity, T _cBe the time of a chip, T _IntervalIt is largest interval for the adjacent frame emission of same terminal.

10. according to Claim 8 or 9 described devices, it is characterized in that described multiple correlation performance number computation subunit determines that according to the region of search [search_min, search_max] length of search sequence is:

L _search＝search_max-search_min

And according to L _SearchSize determine the multiple correlation performance number of the described region of search.

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