CN102223696A - Cell searching method in LTE (long term evolution) system - Google Patents

Cell searching method in LTE (long term evolution) system Download PDF

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CN102223696A
CN102223696A CN2011101637969A CN201110163796A CN102223696A CN 102223696 A CN102223696 A CN 102223696A CN 2011101637969 A CN2011101637969 A CN 2011101637969A CN 201110163796 A CN201110163796 A CN 201110163796A CN 102223696 A CN102223696 A CN 102223696A
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pss
signal
sss
theta
ofdm symbol
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CN102223696B (en
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傅晓宇
叶燕龙
邹锴
胡剑浩
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电子科技大学
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Abstract

The invention discloses a cell searching method in an LTE (long term evolution) system. The method comprises the following steps specifically; a user terminal obtains a receiving signal in a PSS (primary synchronization signal) signal frequency band through a low-pass filter; the PSS is detected according to the receiving signal to obtain 5ms time synchronization and identification (ID) in a physical layer cell group; the circular prefix (CP) length is detected by utilizing the receiving signal, so as to obtain the frequency synchronization and compensate the receiving signal; an SSS (secondary synchronization signal) is detected by utilizing the compensated signal, so as to obtain 10ms time synchronization and identification (ID) in the physical layer cell group. In the method of the invention, while the user terminal and the cell obtain time and frequency synchronization, a main synchronizing signal, an auxiliary synchronizing signal, the CP and the ID of the physical layer cell are detected. By adopting the method, high correct detection probability to the PSS, the SSS and the CP is realized, and the operation complexity is low.

Description

Small region search method in a kind of LTE system

Technical field

The invention belongs to the mobile communication technology field, particularly a kind of small region search method.

Background technology

Long Term Evolution (LTE, Long Term Evolution) is third generation partner program (3GPP, The 3rdGeneration Partnership Project) the mobile communication system standard of Zhi Dinging, use OFDM (OFDM, Orthogonal Frequency Division Multiplexing) radio frequency reception technique, and the diversity antenna technology of MIMO (Multiple-Input Multiple-Output), support Frequency Division Duplexing (FDD) (FDD simultaneously, Frequency Division Duplexing) and time division duplex (TDD, Time Division Duplexing).

In the LTE system, Cell searching is a very the key link.Because it is the prerequisite that communication link is set up in user terminal (UE, User Equipment) and base station.No matter user terminal is to insert the sub-district after start, still carries out the sub-district and switch in communication process, all needs to rely on cell search process and base station to connect.Cell searching is to allow user terminal and sub-district obtain time and Frequency Synchronization, and detected cells sign (ID, process Identity).Cell searching is realized by some down channels, is comprised synchronizing channel (SCH, Synchronization Channel), broadcast channel (BCH, Broadcast Channel) and downlink reference signal (RS, Reference Signal).SCH is divided into primary synchronization channel (PSCH, the Primary Synchronization Channel) and auxiliary synchronization channel (SSCH, the Secondary Synchronization Channel) again.PSCH and SSCH are pure physical layer channel, only are used for synchronously and Cell searching, therefore be called " master sync signal " (PSS) and " auxiliary synchronous signals " (SSS).

Cell search process comprises following two steps usually: detect PSS, be used to obtain the 5ms clock, and obtain the concrete sub-district ID in the sub-district ID group; Detect SSS, be used to obtain 10ms radio frames clock, sub-district ID group.

Radio frames length is 10ms in the LTE system, and 1 radio frames comprises 10 subframes, 20 time slots.A descending time slot is divided into several OFDM symbols again, and according to the difference of CP (Cyclic Prefix) length, the quantity that comprises the OFDM symbol is also different.When using conventional CP, a descending time slot comprises 7 OFDM symbols; When using expansion CP, a descending time slot comprises 6 OFDM symbols.Under the configuration of 20MHz system bandwidth, the length N of an OFDM symbol=2048 (not containing CP), sub-carrier frequencies is spaced apart 15KHz.

LTE agreement regulation, cell search process is used following two kinds of synchronizing signals: master sync signal and auxiliary synchronous signals.The sequence of master sync signal Generate by frequency domain Zadoff-Chu sequence, promptly

S PSS ( u j ) ( n ) = e - j πu j ( n + 1 ) ( n + 2 ) 63 , n = 0,1 , . . . , 30 , e - j πu j n ( n + 1 ) 63 , n = 31,32 , . . . , 61 ,

Wherein, Zadoff-Chu sequence root sequence number u jIn (j=0,1,2) and the physical-layer cell group Corresponding one by one, when The time, u jBe respectively 25,29,34.The PSS signal length is 62 (DC subcarrier vacate need not), and the PSS signal takies the central 1.08MHz of system bandwidth, and the ZC sequence is mapped on 62 subcarriers of central authorities, about each 5 idle sub-carrier be used to provide interference protection.

Auxiliary synchronous signals by two long be that 31 binary system M sequences interweave and form, and it is carried out scrambling with master sync signal.

Wherein, s 0And s 1Be the M sequence, c 0, c 1And z 1Be scramble sequence, parameter m 0And m 1Organize by physical-layer cell ID Unique definite.

For the multiplex mode of PSS and SSS signal, the LTE regulation, under fdd mode, the PSS signal map is mapped to SSS the previous symbol of PSS to last OFDM symbol of time slot 1 and time slot 11.Under tdd mode, the PSS signal map is mapped to SSS on last symbol of time slot 1 and time slot 11 to the 3rd OFDM symbol of time slot 2 and time slot 12.

Fig. 1 shows LTE system topological figure among the present invention.Described wireless communication system comprises: base station equipment 1 and user terminal 21, user terminal 22 ... user terminal 2K.Wherein, each subscriber terminal equipment can be any can including but not limited to the mobile electronic device of wireless mode and base station communication: mobile phone, PDA, Vehicle mounted station etc.; Base station equipment 1 includes but not limited to; Base station or eNodeB, network controller etc., each subscriber terminal equipment and base station equipment can adopt mode of frequency division duplexing or time division duplex to receive and send messages.

In the existing small region search method, need obtain under the situation of Frequency Synchronization at first utilizing blind CP to detect, at frequency domain detection PSS signal to obtain the concrete sub-district ID in the sub-district ID group.Adopt incoherent relevant method, detect SSS, obtain 10ms radio frames clock, sub-district ID group.In the LTE system, it is higher to utilize blind CP to detect the complexity of obtaining Frequency Synchronization, and Nonlinear Transformation in Frequency Offset Estimation detects poor-performing, and particularly under the multiplexing situation of Multicast Channel and unicast tunnel, it is poorer that blind CP detects performance, so the PSS correct detection probability is low.The method of incoherent coherent detection SSS is at channel under the situation of low Doppler frequency shift owing to do not consider the variation of channel circumstance, and detection probability is without any improvement.

In addition, also have on time domain and do the relevant method of sliding, detect PSS to obtain the concrete sub-district ID in the sub-district ID group by local PSS signal and received signal.Because not obtain system time synchronous, so this method time domain slip related operation complexity is very high, and influenced by carrier wave frequency deviation very big for this method simultaneously, and the PSS correct detection probability is lower.

Summary of the invention

The objective of the invention is in order to solve the problem that small region search method in the prior LTE system exists, proposed small region search method in a kind of LTE system.

Technical scheme of the present invention is: small region search method in a kind of LTE system comprises the steps:

S1. user terminal obtains received signal in the PSS signal band by low pass filter;

S2. the received signal of utilizing step S1 to obtain detects the PSS signal, obtains ID in 5ms time synchronized and the physical-layer cell group;

S3. the received signal of utilizing step S1 to obtain detects CP length, obtains Frequency Synchronization, and compensates to received signal;

S4. utilize the input SSS signal after step S3 compensates, obtain 10ms time synchronized and physical-layer cell group ID.

Beneficial effect of the present invention: small region search method of the present invention allows user terminal and sub-district obtain time and Frequency Synchronization when detecting master sync signal, auxiliary synchronous signals, Cyclic Prefix and physical-layer cell identifier.Method of the present invention has higher correct detection probability to master sync signal, auxiliary synchronous signals and Cyclic Prefix, and adopts filtering and M times of down-sampling technology in master sync signal detects, and makes computational complexity be reduced to original 1/M.

Description of drawings

Fig. 1 is LTE system topological figure among the present invention.

Fig. 2 is the schematic flow sheet of small region search method in the LTE of the present invention system.

Fig. 3 is an ID testing process schematic diagram in PSS signal of the present invention and the cell set.

Fig. 4 is that CP of the present invention detects and the Frequency Synchronization schematic flow sheet.

Fig. 5 is that SSS coherent correlation of the present invention detects the schematic flow sheet that detects with cell set ID.

Fig. 6 is the schematic flow sheet that incoherent coherent detection of SSS of the present invention and cell set ID detect.

Fig. 7 method of the present invention is to PSS and the correct probability schematic diagram that detects of CP.

Fig. 8 method of the present invention is SSS detection probability schematic diagram under the TDD system.

Fig. 9 method of the present invention is SSS detection probability schematic diagram under the FDD system.

Embodiment

The invention will be further elaborated below in conjunction with accompanying drawing and specific embodiment.

Fig. 2 shows the flow chart that carry out small region search method of the present invention in the LTE system, and is specific as follows:

S1. user terminal obtains received signal r (k) in the PSS signal band by low pass filter, and the cut-off frequency of low pass filter is 0.465MHz, and promptly PSS takies half of number of sub carrier wave and subcarrier spacing product.

Those skilled in the art should understand that, the cut-off frequency 0.465MHz of above-mentioned low pass filter only just lists, but not be used to limit the present invention, in fact, the cut-off frequency of low pass filter according to actual sub-carriers at interval and PSS take number of sub carrier wave and choose other different value.

S2. the received signal of utilizing step S1 to obtain detects the PSS signal, obtains in 5ms time synchronized and the physical-layer cell group It step by step as shown in Figure 3.Specific as follows:

S21. produce three groups of time domain PSS sequences, and carry out down-sampling and segmentation;

S22. carry out down-sampling and segmentation to received signal;

S23. calculating slides is correlated with, and obtains the index of maximum related value, obtains the 5ms time synchronized;

S24. the group sequence number at maximum related value place is determined physical-layer cell ID in obtaining.

In step S21, in default physical-layer cell group With the corresponding relation of Zadoff-Chu root sequence number u, produce three groups of time domain PSS sequences

s PSS ( u j ) ( k ) = 1 N Σ n = - N / 2 - 1 S PSS ( u j ) ( n + N 2 ) e j 2 π N kn + 1 N Σ n = 1 N / 2 S PSS ( u j ) ( n + N 2 - 1 ) e j 2 π N kn , j = 0,1,2 ,

Wherein, N represents that IFFT counts.

By default down-sampling multiple With segmentation hop count M pTo signal Carry out down-sampling and segmentation.As a kind of optimal way, described N Min=64, segmentation hop count M p=2.

In step S22, by default down-sampling multiple With segmentation hop count M pR (k) carries out down-sampling and segmentation to received signal.As another kind of optimal way, described N Min=64, segmentation hop count M p=2.

In step S23, calculate through after down-sampling and the segment processing With the segmentation correlation of r (k), obtain three groups of relevant episode,

C j ( θ ) = Σ i = 0 M p - 1 | Σ k = 0 N min / M p - 1 r ( kM + θ + N min M p i ) [ s PSS ( u j ) ( kM + N min M p i ) ) ] * | 2 , j = 0,1,2 , Formula (1)

And obtain the index of maximum related value Obtain the estimated value of PSS signal original position And then get access to time synchronized;

In step S24, the group sequence number j that obtains maximum related value place in the formula (1) determines in the physical-layer cell group Promptly N ^ ID ( 2 ) = arg max j { C j ( θ ) } .

S3. the received signal of utilizing step S1 to obtain detects CP length, obtains Frequency Synchronization, and compensates to received signal; Specifically comprise step by step followingly, specifically as shown in Figure 4, specifically comprise step by step following:

S31. obtain the original position of CP under the default CP pattern;

S32. calculate under every kind of CP pattern the normalization correlation of the CP of PSS signal place symbol;

S33. calculate under every kind of CP pattern the normalization correlation of the CP of SSS signal place symbol;

S34. obtain CP length by preset rules;

S35. fractional part of frequency offset is estimated;

S36. fractional part of frequency offset compensation;

S37. in preset range, it is relevant with the slip that receives PSS to calculate frequency domain PSS;

S38. according to described slip correlation, do integer frequency offset and estimate;

S39. the integer frequency offset compensation is finished Frequency Synchronization.

In step S31, according to default two kinds CP length, i.e. first kind of conventional CP, length is L 1=144 and second kind the expansion CP, length is L 2=512, obtain the original position of PSS place OFDM symbol CP under the i kind CP pattern θ ^ CP , i 1 = θ ^ p - L i , i = 1,2 , Original position with SSS place OFDM symbol CP θ ^ CP , i 2 = θ ^ p - L i - N , i = 1,2 .

In step S32, calculate respectively under the i kind CP pattern, CP duplicates the normalization correlation of part in PSS signal place OFDM symbol CP and this OFDM symbol

M i 1 = | R i 1 | P i 1 , i = 1,2 , Formula (21)

Wherein,

R i 1 = Σ k = 0 L i - 1 r * ( k + θ ^ CP , i 1 ) r ( k + N + θ ^ CP , i 2 ) , i = 1,2 , Formula (31)

P i 1 = Σ k = 0 L i - 1 | r ( k + N + θ ^ CP , i 1 ) | 2 , i = 1,2 , Formula (41)

R I1Be illustrated under the i kind CP pattern, CP duplicates the correlation of part, P in the CP of PSS signal place OFDM symbol and this OFDM symbol I1The energy of expression OFDM symbol under i kind CP pattern, N represents the OFDM symbol lengths.

In step S33, for the FDD system, calculate respectively under the i kind CP pattern, CP duplicates the normalization correlation of part in the CP of SSS signal place OFDM symbol and this OFDM symbol,

M i 2 = | R i 2 | P i 2 , i = 1,2 , Formula (22)

Wherein,

R i 2 = Σ k = 0 L i - 1 r * ( k + θ ^ CP , i 2 ) r ( k + N + θ ^ CP , i 2 ) , i = 1,2 , Formula (32)

P i 2 = Σ k = 0 L i - 1 | r ( k + N + θ ^ CP , i 2 ) | 2 , i = 1,2 , Formula (42)

R I2Be illustrated under the i kind CP pattern, CP duplicates the correlation of part, P in the CP of SSS signal place OFDM symbol and this OFDM symbol I2The energy of expression OFDM symbol under i kind CP pattern, N represents the OFDM symbol lengths.

Calculate the average of the CP normalization correlation of PSS signal and SSS signal place OFDM symbol, promptly I=1,2, with further reduction noise jamming.

For the TDD system, do not need the CP and the interior CP of this OFDM symbol that calculate SSS signal place OFDM symbol to duplicate the normalization correlation of part, i.e. M I2=0, M then i=M I1

In step S34, obtain CP length by preset rules, preset rules is as follows:

L ^ CP = 144 , M 1 &GreaterEqual; M 2 512 , M 1 < M 2 Formula (5)

In step S35, get the phase angle of formula (31) maximum related value and, obtain the fractional part of frequency offset estimation divided by 2 π Promptly

&epsiv; ^ F = - 1 2 &pi; &angle; { max { R i 1 } }

In step S36, do the fractional part of frequency offset compensation to received signal, promptly

In step S37, at the frequency center In the individual sub-reference carrier wave, calculate frequency domain PSS signal and the slip correlation that receives frequency-region signal, promptly

&Lambda; ( &gamma; ) = &Sigma; n = - 31 31 [ S PSS ( N ^ ID ( 2 ) ) ( n ) ] * [ &Sigma; k = - N / 2 - 1 r &prime; ( k + N 2 + &theta; ^ p ) e - j 2 &pi; N ( n + &gamma; ) k + &Sigma; k = 1 N / 2 r &prime; ( n + N 2 + &theta; ^ P - 1 ) e - j 2 &pi; N ( n + &gamma; ) k ] Formula (6)

Wherein, Be maximum normalization carrier wave frequency deviation and preset according to the crystal oscillator sum of errors channel maximum doppler frequency of transmitting-receiving two-end, In the expression physical-layer cell group The sequence of master sync signal; Here, conjugation is got in " * " expression.

In step S38, by the index of formula (6) maximum related value Estimate integer-time carrier wave frequency deviation

In step S39, do the integer frequency offset compensation, So far, user terminal received signal Obtain Frequency Synchronization with base station equipment.

S4. utilize the input SSS signal after step S3 compensates, obtain 10ms time synchronized and physical-layer cell group ID.

In step S4, user terminal is according to signal Detect the SSS signal and obtain 10ms time synchronized and physical-layer cell group In this step, according to dual-mode and channel Doppler frequency shift size, SSS detects and can be divided into coherent correlation detection and incoherent coherent detection.The coherent correlation detection method comprises step S41-S49, specifically as shown in Figure 5, is applicable to low Doppler frequency shift environment and fdd mode.Described step S4 specifically comprises step by step following:

S41. according to least square criterion, estimate the PSS channel frequency response;

S42. default linear phase low pass filter;

S43. construct new PSS channel frequency response and pass through low pass filter by preset rules;

S44. brachymemma filter output is done compensation to the frequency domain SSS signal that receives;

S45. traversal produces the even number sequence of 31 groups of SSS signals in subframe 0;

S46. calculate described even number sequence and the correlation that compensates back SSS signal even number sequence;

S47. traversal produces the odd number sequence of 31 groups of SSS signals in subframe 0;

S48. calculate described odd number sequence and the correlation that compensates back SSS signal odd number sequence;

S49. according to preset rules, obtain SSS signal place subframe numbers and cell set ID.

Incoherent related detecting method comprises step S41 '-S47 ', specifically as shown in Figure 6, is applicable to high doppler shift environment and tdd mode.Specific as follows:

S41 '. according to least square criterion, estimate the PSS channel frequency response;

S42 '. the frequency domain SSS signal that receives is done compensation;

S43 '. traversal produces the even number sequence of 31 groups of SSS signals in subframe 0;

S44 '. calculate described even number sequence and the correlation that compensates back SSS signal even number sequence;

S45 '. traversal produces the odd number sequence of 31 groups of SSS signals in subframe 0;

S46 '. calculate described odd number sequence and the correlation that compensates back SSS signal odd number sequence;

S47 '. according to preset rules, obtain SSS signal place subframe numbers and cell set ID.

In step S41, because PSS time-frequency location aware utilizes the PSS frequency-region signal R that receives PSS(n) and local frequency domain PSS signal S PSS(n), estimate PSS channel frequency response under least square (LS) criterion, promptly

H ^ LS = R PSS ( n ) / S PSS ( n ) .

In step S42, the linear phase low pass filter on default L-1 rank, flora of filters postpones

As a kind of optimal way, pass band cut-off frequency w p=t Max* Δ f, wherein t MaxBe the maximum delay spread of channel, Δ f is a subcarrier spacing, stopband cut-off frequency w s=5w p

In step S43, note Be 1 * M vector, according to 1 * (M+2g) new vector of following rule structure

Will By low pass filter default among the step S42, to do frequency domain filtering and suppress the time domain noise, filter output is designated as

In step S44, according to following regular brachymemma Obtain new 1 * M vector As the channel transfer function of PSS,

To the frequency domain SSS signal R that receives SSS(n) do following compensation, obtain

In step S45, m produces the even number sequence of 31 groups of SSS signals in subframe 0 in [0,30] traversal

In step S46, get the SSS signal after the compensation among the step S44 The even index composition sequence The sequence of calculation With Correlation, and the position m of note maximum related value 01:

m 01 = arg max m &Element; [ 0,30 ] { &Sigma; n = 0 30 R ^ SSS * ( 2 n ) S SSS ( m ) ( 2 n ) } .

In step S47, m produces the odd number sequence of 31 groups of SSS signals in subframe 0 in [0,30] traversal

In step S48, get the SSS signal after step S44 compensates The odd index composition sequence The sequence of calculation With Correlation, and the position m of note maximum related value 10:

m 10 = arg max m &Element; [ 0,30 ] { &Sigma; n = 0 30 R ^ SSS * ( 2 n + 1 ) S SSS ( m ) ( 2 n + 1 ) }

In step S49,, obtain SSS signal place subframe numbers and cell set according to preset rules Preset rules is as follows: m 0=min (m 01, m 10), m 1=max (m 01, m 10).Make d=|m 01-m 10|, the physical-layer cell group

ID N ^ ID ( 1 ) = m 0 , d = 1 m 0 + 30 , d = 2 m 0 + 59 , d = 3 m 0 + 87 , d = 4 m 0 + 114 , d = 5 m 0 + 140 , d = 6 m 0 + 165 , d = 7

If m 01<m 10, then the subframe numbers at SSS signal place is 0; Otherwise be 5.So far, user terminal and base station equipment obtain the 10ms time synchronized.

In step S41 ', because PSS time-frequency location aware utilizes the PSS frequency-region signal R that receives PSS(n) and local frequency domain PSS signal S PSS(n), estimate PSS channel frequency response under the least square criterion, promptly

H ^ LS ( n ) = R PSS ( n ) / S PSS ( n ) .

In step S42 ', to the frequency domain SSS signal R that receives SSS(n) do following compensation, obtain

Step S43 '-S47 ' is consistent with step S45-S49 content.

User terminal is according in the physical-layer cell group With the physical-layer cell group Obtain the sub-district Promptly N ID cell = 3 N ^ ID ( 1 ) + N ^ ID ( 2 ) , Finishing physical-layer cell ID detects.

The beneficial effect of technical solution of the present invention is described below by emulation.Concrete simulated environment is as follows: LTE system bandwidth 20MHz, carrier frequency 2.6GHz, FFT size 2048 points, subcarrier spacing 15kHz, systematic sampling frequency 30.72MHz, crystal oscillator deviation 10ppm, channel model is expansion typical urban model (ETU, Extended Typical Urban).

Fig. 7 has showed the probability of method of the present invention to PSS and the correct detection of CP, can see that the detection probability of PSS reaches more than 98%, and noise is had very strong robustness.During greater than-2dB, the correct detection also of CP surpasses 95% in signal to noise ratio.

Fig. 8 has showed method of the present invention probability to the correct detection of SSS when the TDD system.As shown in Figure 8, under the situation of signal to noise ratio less than 0dB, the performance that non-coherent approaches (S41 '-S47 ') correctly detects SSS is better than coherent approach.Under the situation of signal to noise ratio greater than 0dB, the performance that coherent approach (S41-S49) correctly detects SSS is better than non-coherent approaches.Non-coherent approaches can effectively be resisted the influence of Doppler in the channel, signal to noise ratio during greater than 0dB detection probability greater than 90%.Coherent approach is under low Doppler's situation, and detection probability is greater than 90% during greater than 0dB in signal to noise ratio, and under the situation of high-doppler, detection probability surpasses 80%.

Fig. 9 has showed method of the present invention probability to the correct detection of SSS when the FDD system.As shown in Figure 9, under the situation of signal to noise ratio less than 0dB, the performance that non-coherent approaches correctly detects SSS is better than coherent approach.Under the situation of signal to noise ratio greater than 0dB, the performance that coherent approach correctly detects SSS is better than non-coherent approaches.Non-coherent approaches can effectively be resisted the influence of Doppler in the channel, signal to noise ratio during greater than 0dB detection probability greater than 90%.Coherent approach is under low Doppler's situation, and detection probability is greater than 90% during greater than 0dB in signal to noise ratio, and under the situation of high-doppler, detection probability surpasses 86%.As can be seen, the technical program of the present invention has higher physical-layer cell identifier detection probability.

Method of the present invention adopts M times of down-sampling technology in PSS detects, make computational complexity be reduced to original 1/M.Therefore, technical scheme of the present invention has lower computational complexity.

Those of ordinary skill in the art will appreciate that embodiment described here is in order to help reader understanding's principle of the present invention, should to be understood that protection scope of the present invention is not limited to such special statement and embodiment.Those of ordinary skill in the art can make various other various concrete distortion and combinations that do not break away from essence of the present invention according to these technology enlightenments disclosed by the invention, and these distortion and combination are still in protection scope of the present invention.

Claims (10)

1. small region search method in the LTE system is characterized in that, comprises the steps:
S1. user terminal obtains received signal in the PSS signal band by low pass filter;
S2. the received signal of utilizing step S1 to obtain detects the PSS signal, obtains ID in 5ms time synchronized and the physical-layer cell group;
S3. the received signal of utilizing step S1 to obtain detects CP length, obtains Frequency Synchronization, and compensates to received signal;
S4. utilize the input SSS signal after step S3 compensates, obtain 10ms time synchronized and physical-layer cell group ID.
2. small region search method according to claim 1 is characterized in that, the cut-off frequency of the described low pass filter of step S1 is 0.465MHz.
3. small region search method according to claim 1 is characterized in that, described step S2 specifically comprises step by step following:
S21. produce three groups of time domain PSS sequences, and carry out down-sampling and segmentation, in default physical-layer cell group With the corresponding relation of Zadoff-Chu root sequence number u, produce three groups of time domain PSS sequences
s PSS ( u j ) ( k ) = 1 N &Sigma; n = - N / 2 - 1 S PSS ( u j ) ( n + N 2 ) e j 2 &pi; N kn + 1 N &Sigma; n = 1 N / 2 S PSS ( u j ) ( n + N 2 - 1 ) e j 2 &pi; N kn , j = 0,1,2 ,
Wherein, S PSS ( u j ) ( n ) = e - j &pi;u j ( n + 1 ) ( n + 2 ) 63 , n = 0,1 , . . . , 30 , e - j &pi;u j n ( n + 1 ) 63 , n = 31,32 , . . . , 61 , , Zadoff-Chu sequence root sequence number u jIn (j=0,1,2) and the physical-layer cell group Corresponding one by one, when The time, u jBe respectively 25,29,34, N represents that IFFT counts,
By default down-sampling multiple With segmentation hop count M pTo signal Carry out down-sampling and segmentation;
S22. by default down-sampling multiple With segmentation hop count M pR (k) carries out down-sampling and segmentation to received signal;
S23. calculate through after down-sampling and the segment processing With the segmentation correlation of r (k), obtain three groups of relevant episode,
C j ( &theta; ) = &Sigma; i = 0 M p - 1 | &Sigma; k = 0 N min / M p - 1 r ( kM + &theta; + N min M p i ) [ s PSS ( u j ) ( kM + N min M p i ) ) ] * | 2 , j = 0,1,2 , Formula (1)
And obtain the index of maximum related value Obtain the estimated value of PSS signal original position And then get access to time synchronized;
S24. the group sequence number j that obtains maximum related value place in the formula (1) determines in the physical-layer cell group Promptly N ^ ID ( 2 ) = arg max j { C j ( &theta; ) } .
4. small region search method according to claim 3 is characterized in that, the N described in the step S21 Min=64, segmentation hop count M p=2.
5. according to claim 3 or 4 described small region search methods, it is characterized in that the N described in the step S22 Min=64, segmentation hop count M p=2.
6. small region search method according to claim 3 is characterized in that, described step S3 specifically comprises step by step following:
S31. according to default two kinds CP length, i.e. first kind of conventional CP, length is L 1=144 and second kind the expansion CP, length is L 2=512, obtain the original position of PSS place OFDM symbol CP under the i kind CP pattern &theta; ^ CP , i 1 = &theta; ^ p - L i , i = 1,2 , Original position with SSS place OFDM symbol CP &theta; ^ CP , i 2 = &theta; ^ p - L i - N , i = 1,2 .
S32. calculate respectively under the i kind CP pattern, CP duplicates the normalization correlation of part in PSS signal place OFDM symbol CP and this OFDM symbol
M i 1 = | R i 1 | P i 1 , i = 1,2 , Formula (21)
Wherein,
R i 1 = &Sigma; k = 0 L i - 1 r * ( k + &theta; ^ CP , i 1 ) r ( k + N + &theta; ^ CP , i 2 ) , i = 1,2 , Formula (31)
P i 1 = &Sigma; k = 0 L i - 1 | r ( k + N + &theta; ^ CP , i 1 ) | 2 , i = 1,2 , Formula (41)
R I1Be illustrated under the i kind CP pattern, CP duplicates the correlation of part, P in the CP of PSS signal place OFDM symbol and this OFDM symbol I1The energy of expression OFDM symbol under i kind CP pattern, N represents the OFDM symbol lengths;
S34. obtain CP length by preset rules, preset rules is as follows:
L ^ CP = 144 , M 1 &GreaterEqual; M 2 512 , M 1 < M 2 Formula (5)
S35. the phase angle of formula (31) maximum related value and divided by 2 π obtains fractional part of frequency offset and estimates Promptly
&epsiv; ^ F = - 1 2 &pi; &angle; { max { R i 1 } }
S36. do the fractional part of frequency offset compensation to received signal, promptly
S37. at the frequency center In the individual sub-reference carrier wave, calculate frequency domain PSS signal and the slip correlation that receives frequency-region signal, promptly
&Lambda; ( &gamma; ) = &Sigma; n = - 31 31 [ S PSS ( N ^ ID ( 2 ) ) ( n ) ] * [ &Sigma; k = - N / 2 - 1 r &prime; ( k + N 2 + &theta; ^ p ) e - j 2 &pi; N ( n + &gamma; ) k + &Sigma; k = 1 N / 2 r &prime; ( n + N 2 + &theta; ^ P - 1 ) e - j 2 &pi; N ( n + &gamma; ) k ] Formula (6)
Wherein, Be maximum normalization carrier wave frequency deviation and preset according to the crystal oscillator sum of errors channel maximum doppler frequency of transmitting-receiving two-end, In the expression physical-layer cell group The sequence of master sync signal;
S38. pass through the index of formula (6) maximum related value Estimate integer-time carrier wave frequency deviation
S39. do the integer frequency offset compensation, So far, user terminal received signal Obtain Frequency Synchronization with base station equipment.
7. small region search method according to claim 3 is characterized in that, described step S3 specifically comprises step by step following:
S31. according to default two kinds CP length, i.e. first kind of conventional CP, length is L 1=144 and second kind the expansion CP, length is L 2=512, obtain the original position of PSS place OFDM symbol CP under the i kind CP pattern &theta; ^ CP , i 1 = &theta; ^ p - L i , i = 1,2 , Original position with SSS place OFDM symbol CP &theta; ^ CP , i 2 = &theta; ^ p - L i - N , i = 1,2 .
S32. calculate respectively under the i kind CP pattern, CP duplicates the normalization correlation of part in PSS signal place OFDM symbol CP and this OFDM symbol
M i 1 = | R i 1 | P i 1 , i = 1,2 , Formula (21)
Wherein,
R i 1 = &Sigma; k = 0 L i - 1 r * ( k + &theta; ^ CP , i 1 ) r ( k + N + &theta; ^ CP , i 2 ) , i = 1,2 , Formula (31)
P i 1 = &Sigma; k = 0 L i - 1 | r ( k + N + &theta; ^ CP , i 1 ) | 2 , i = 1,2 , Formula (41)
R I1Be illustrated under the i kind CP pattern, CP duplicates the correlation of part, P in the CP of PSS signal place OFDM symbol and this OFDM symbol I1The energy of expression OFDM symbol under i kind CP pattern, N represents the OFDM symbol lengths.
S33. calculate respectively under the i kind CP pattern, CP duplicates the normalization correlation of part in the CP of SSS signal place OFDM symbol and this OFDM symbol,
M i 2 = | R i 2 | P i 2 , i = 1,2 , Formula (22)
Wherein,
R i 2 = &Sigma; k = 0 L i - 1 r * ( k + &theta; ^ CP , i 2 ) r ( k + N + &theta; ^ CP , i 2 ) , i = 1,2 , Formula (32)
P i 2 = &Sigma; k = 0 L i - 1 | r ( k + N + &theta; ^ CP , i 2 ) | 2 , i = 1,2 , Formula (42)
R I2Be illustrated under the i kind CP pattern, CP duplicates the correlation of part, P in the CP of SSS signal place OFDM symbol and this OFDM symbol I2The energy of expression OFDM symbol under i kind CP pattern, N represents the OFDM symbol lengths;
Calculate the average of the CP normalization correlation of PSS signal and SSS signal place OFDM symbol, promptly M i = 1 2 &times; &Sigma; k = 1 2 M ik , i = 1,2 ;
S34. obtain CP length by preset rules, preset rules is as follows:
L ^ CP = 144 , M 1 &GreaterEqual; M 2 512 , M 1 < M 2 Formula (5)
S35. the phase angle of formula (31) maximum related value and divided by 2 π obtains fractional part of frequency offset and estimates Promptly
&epsiv; ^ F = - 1 2 &pi; &angle; { max { R i 1 } }
S36. do the fractional part of frequency offset compensation to received signal, promptly
S37. at the frequency center In the individual sub-reference carrier wave, calculate frequency domain PSS signal and the slip correlation that receives frequency-region signal, promptly
&Lambda; ( &gamma; ) = &Sigma; n = - 31 31 [ S PSS ( N ^ ID ( 2 ) ) ( n ) ] * [ &Sigma; k = - N / 2 - 1 r &prime; ( k + N 2 + &theta; ^ p ) e - j 2 &pi; N ( n + &gamma; ) k + &Sigma; k = 1 N / 2 r &prime; ( n + N 2 + &theta; ^ P - 1 ) e - j 2 &pi; N ( n + &gamma; ) k ] Formula (6)
Wherein, Be maximum normalization carrier wave frequency deviation and preset according to the crystal oscillator sum of errors channel maximum doppler frequency of transmitting-receiving two-end, In the expression physical-layer cell group The sequence of master sync signal;
S38. pass through the index of formula (6) maximum related value Estimate integer-time carrier wave frequency deviation
S39. do the integer frequency offset compensation, So far, user terminal received signal Obtain Frequency Synchronization with base station equipment.
8. according to claim 6 or 7 described small region search methods, it is characterized in that described step S4 specifically comprises step by step following:
S41. utilize the PSS frequency-region signal R that receives PSS(n) and local frequency domain PSS signal S PSS(n), estimate PSS channel frequency response under the least square criterion, promptly
H ^ LS = R PSS ( n ) / S PSS ( n ) ;
S42. preset the linear phase low pass filter on L-1 rank, flora of filters postpones
S43. remember Be 1 * M vector, according to 1 * (M+2g) new vector of following rule structure
Will By low pass filter default among the step S42, to do frequency domain filtering and suppress the time domain noise, filter output is designated as
S44. according to following regular brachymemma Obtain new 1 * M vector As the channel transfer function of PSS,
To the frequency domain SSS signal R that receives SSS(n) do following compensation, obtain
S45.m produces the even number sequence of 31 groups of SSS signals in subframe 0 in [0,30] traversal
S46. get the SSS signal after the compensation among the step S44 The even index composition sequence The sequence of calculation With Correlation, and the position of note maximum related value m 01 = arg max m &Element; [ 0,30 ] { &Sigma; n = 0 30 R ^ SSS * ( 2 n ) S SSS ( m ) ( 2 n ) } ;
S47.m produces the odd number sequence of 31 groups of SSS signals in subframe 0 in [0,30] traversal
S48. get the SSS signal after step S44 compensates The odd index composition sequence The sequence of calculation With Correlation, and the position m of note maximum related value 10:
m 10 = arg max m &Element; [ 0,30 ] { &Sigma; n = 0 30 R ^ SSS * ( 2 n + 1 ) S SSS ( m ) ( 2 n + 1 ) } ;
S49. according to preset rules, obtain SSS signal place subframe numbers and cell set Preset rules is as follows: m 0=min (m 01, m 10), m 1=max (m 01, m 10), make d=|m 01-m 10|, the physical-layer cell group
ID N ^ ID ( 1 ) = m 0 , d = 1 m 0 + 30 , d = 2 m 0 + 59 , d = 3 m 0 + 87 , d = 4 m 0 + 114 , d = 5 m 0 + 140 , d = 6 m 0 + 165 , d = 7
If m 01<m 10, then the subframe numbers at SSS signal place is 0; Otherwise be 5, so far, user terminal and base station equipment obtain the 10ms time synchronized.
9. according to claim 6 or 7 described small region search methods, it is characterized in that described step S4 specifically comprises step by step following:
S41 '. utilize the PSS frequency-region signal R that receives PSS(n) and local frequency domain PSS signal S PSS(n), estimate PSS channel frequency response under the least square criterion, promptly
H ^ LS ( n ) = R PSS ( n ) / S PSS ( n ) ;
S42 '. to the frequency domain SSS signal R that receives SSS(n) do following compensation, obtain
S43 ' .m produces the even number sequence of 31 groups of SSS signals in subframe 0 in [0,30] traversal
S44 '. get the SSS signal after the compensation among the step S44 The even index composition sequence The sequence of calculation With Correlation, and the position m of note maximum related value 01:
m 01 = arg max m &Element; [ 0,30 ] { &Sigma; n = 0 30 R ^ SSS * ( 2 n ) S SSS ( m ) ( 2 n ) } ;
S45 ' .m produces the odd number sequence of 31 groups of SSS signals in subframe 0 in [0,30] traversal
S46 '. get the SSS signal after step S44 compensates The odd index composition sequence The sequence of calculation With Correlation, and the position m of note maximum related value 10:
m 10 = arg max m &Element; [ 0,30 ] { &Sigma; n = 0 30 R ^ SSS * ( 2 n + 1 ) S SSS ( m ) ( 2 n + 1 ) } ;
S47 '. according to preset rules, obtain SSS signal place subframe numbers and cell set Preset rules is as follows: m 0=min (m 01, m 10), m 1=max (m 01, m 10), make d=|m 01-m 10|, the physical-layer cell group
ID N ^ ID ( 1 ) = m 0 , d = 1 m 0 + 30 , d = 2 m 0 + 59 , d = 3 m 0 + 87 , d = 4 m 0 + 114 , d = 5 m 0 + 140 , d = 6 m 0 + 165 , d = 7
If m 01<m 10, then the subframe numbers at SSS signal place is 0; Otherwise be 5, so far, user terminal and base station equipment obtain the 10ms time synchronized.
10. small region search method according to claim 8 is characterized in that, the pass band cut-off frequency w described in the step S42 p=t Max* Δ f, wherein t MaxBe the maximum delay spread of channel, Δ f is a subcarrier spacing, stopband cut-off frequency w s=5w p
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