CN101005477A - Synchronous signal sending and detecting method for orthogonal frequency division complex system - Google Patents

Abstract

In the invention, the transmitting method comprises: with cyclic shift, letting the peak value of cyclic convolution of circular convolution made for the synchronous signals roughly synchronized at receiving terminal and the local reference signals to be at different positions. The detection method comprises: when making synchronous timing, simultaneously using said positions to detect the cyclic prefix type. By the invention, in the process of getting the synchronous signal timing, the mobile station simultaneously gets the cyclic prefix length type of OFDM symbol so as to have no need to take extra steps used for detecting the cyclic prefix type.

Description

A kind of synchronizing signal of ofdm system sends and detection method

Technical field

The present invention relates to ofdm system, relate to the synchronizing signal that has multiple Cyclic Prefix particularly and send and detection method based on ofdm system.

Background technology

In ofdm system, each OFDM (OFDM) symbol all comprises two parts: Cyclic Prefix part and data division.Cyclic Prefix partly is the copy of data division aft section, and it has the double action that resists intersymbol interference and inter-carrier interference.Generally speaking, the Cyclic Prefix partial data is long more, and its ability that resists intersymbol interference and inter-carrier interference is also just strong more.But negative effect is also arranged, and the Cyclic Prefix partial data is long more, and the expense of system is also just big more.In actual applications, in order to reduce this negative effect of Cyclic Prefix, system supports multiple circulating prefix-length usually.System can be according to environment, and the difference of type of service is selected the length of Cyclic Prefix flexibly, such as in the ETURA system, just supports two kinds of length type of cyclic prefix to adapt to different demands.

But the flexible selection of circulating prefix-length has brought adverse effect for travelling carriage and system synchronization.。Because travelling carriage also needs additionally to know the length type of cyclic prefix of synchronizing signal use in synchronizing process.Usually, the length type of cyclic prefix that obtains the synchronizing signal use has dual mode: a kind of blind checking method that is called, the basic ideas of this method are: travelling carriage is attempted all possible length type of cyclic prefix, according to the calculating measurements of every kind of length type of cyclic prefix, determine the most suitable length type of cyclic prefix.Another mode is that the regulation synchronizing signal only sends on the OFDM of a certain specific cyclic prefix length type symbol.This method needs the support of standard, and synchronizing signal just is to send on the part carrier wave of OFDM symbol usually, and this mandatory provision makes troubles for synchronizing signal and the multiplexing of other signal.

Summary of the invention

The synchronizing signal that the technical issues that need to address of the present invention provide a kind of ofdm system sends and detection method, carries out cyclic prefix type during and detect when obtaining synchronization timing, avoids extra cyclic prefix type during detection overhead.

Above-mentioned technical problem of the present invention solves like this, provides a kind of synchronizing signal of ofdm system to send and detection method, and receiving terminal carries out cyclic prefix type during synchronously simultaneously and detects, and may further comprise the steps:

1.1) transmitting terminal carries out cyclic shift to the data division of synchronizing signal by cyclic prefix type during makes it be positioned at diverse location at the peak value that receiving terminal and local reference signal carry out circular convolution;

1.2) receiving terminal distinguishes according to described diverse location in carrying out the synchronization timing process and restore described cyclic prefix type during.

According to transmission provided by the invention and detection method, described synchronization timing process is used local reference sync signal x ^*(0), x ^*(N-1), x ^*(N-2) ... x ^*(1), comprise following concrete steps:

2.1) utilize standard sync signal time domain repeat property to determine the thick timing data r (0) of synchronizing signal ... r (N-1), r (N) ... r (2N-1);

2.2) calculate that to measure c1:c1 be r (0) ... .r (N-1) and local reference sync signal x ^*(0), x ^*(N-1), x ^*(N-2) ... x ^*(1) circular convolution;

2.3) calculate and measure c, c=|c1| ², | x| represents the mould of x, and x is any expression formula;

2.4) calculate the index k measure greatest member correspondence among the c, according to the thin timing position and the cyclic prefix type during of the rule of correspondence decision synchronizing signal of the number range of k and the development of described circular convolution peak value rule.

According to transmission provided by the invention and detection method, described step 2.2) comprise that also it is r (N) that c2:c2 is measured in calculating ... .r (2N-1) and local reference sync signal x ^*(0), x ^*(N-1), x ^*(N-2) ... x ^*(1) circular convolution; Described step 1.3) and 1.4) in measure c=|c1| ²+ | c2| ²

According to transmission provided by the invention and detection method, described step 2.1) comprising:

2.1.1) calculate and measure M (k): $M\left(k\right)={\left|\underset{p=0}{\overset{N-1}{\mathrm{\Σ}}}{r}^{*}(n+k+p)r(n+k+p+N)\right|}^2,$ k＝0，1....2N-1；

2.1.2) calculate the index that obtains maximum correspondence among the M (k), be made as m, then r (n+m) is exactly the thick timing position of synchronizing signal;

2.1.3) obtain the thick timing data of synchronizing signal according to thick timing position: r (0) ... r (N-1), r (N) ... r (2N-1).

According to transmission provided by the invention and detection method, described circular convolution is:

$c1=\left(\begin{array}{c}c1\left(0\right)\\ c1\left(1\right)\\ c1\left(2\right)\\ ...\\ c1(N=1)\end{array}\right)=\left(\begin{array}{ccccc}{x}^{*}\left(0\right),& x^{*}\left(1\right),& x^{*}\left(2\right)& ...& x^{*}(N-1)\\ x^{*}(N-1),& x^{*}\left(0\right),& x^{*}\left(1\right)& ...& x^{*}(N-2)\\ x^{*}(N-2),& x^{*}(N-1),& x^{*}\left(0\right)& ...& x^{*}(N-3)\\ ...& & & & \\ x^{*}\left(1\right),& x^{*}\left(2\right),& x^{*}\left(3\right)& ...& x^{*}\left(0\right)\end{array}\right)\×\left(\begin{array}{c}\begin{array}{c}r\left(0\right)\\ r\left(1\right)\\ r\left(2\right)\\ ...\\ r(N-1)\end{array}\end{array}\right)$

According to transmission provided by the invention and detection method, described cyclic prefix type during is two kinds, circulating prefix-length is respectively L1 and L2, corresponding described cyclic shift is respectively 0 and the m+1 position that moves to left, corresponding described data division is respectively ideal synchronisation signal x (0), x (1) ... the .x (2N-1) and the synchronizing signal x (m+1) that moves to left ... .x (2N-1), x (0) ... .x (m); M=L2+D, 0≤D≤N-L1-L2-2,2N are the length of described data division.

According to transmission provided by the invention and detection method, D gets optimal value:

Expression rounds up to x;

_ x_ represents x is rounded downwards;

According to transmission provided by the invention and detection method, described cyclic prefix type during is two kinds, and corresponding described cyclic shift is respectively 0 and when moving to left the m+1 position, and the described rule of correspondence is:

k	Judgment rule
		0≤k≤L1	Cyclic prefix type during 1, and received signal r (0) is with respect to the leading k of a desirable timing position sampling point of synchronizing signal.
L1+1≤k≤N-L2-D-2	Cyclic prefix type during 2, and received signal r (0) delays (N-L2-D-1-k) individual sampling point with respect to the desirable timing position of synchronizing signal.
		N-L2-D-1≤k≤N-D-1	Cyclic prefix type during 2, and received signal r (0) is with respect to leading (k+L2+D-N) the individual sampling point of the desirable timing position of synchronizing signal.
N-D≤k≤N-1	Cyclic prefix type during 1, and received signal r (0) is with respect to synchronously

The desirable timing position of signal is delayed (N-k-1) individual sampling point.

According to transmission provided by the invention and detection method, described cyclic prefix type during can be three kinds, and circulating prefix-length is respectively L1, L2 and L3, and corresponding described cyclic shift is respectively 0, the m+1 position and the p+1 position that moves to left move to left, m=N-L1-D-1, p=N-L1-L2-2D-2;

Expression rounds up to x;

_ x_ represents x is rounded downwards.

According to transmission provided by the invention and detection method, the described rule of correspondence is:

k	Judgment rule
		0≤k≤L1	Cyclic prefix type during 1, and received signal r (0) is with respect to the leading k of a desirable timing position sampling point of synchronizing signal.
L1+1≤k≤L1+D	Cyclic prefix type during 2, and received signal r (0) delays (L1+D+1-k) individual sampling point with respect to the desirable timing position of synchronizing signal.
		L1+D+1≤k≤L1+D+1+L2	Cyclic prefix type during 2, and received signal r (0) is with respect to leading (k-L1-D-1) the individual sampling point of the desirable timing position of synchronizing signal.
L1+L2+D+2≤k≤L1++L2+2D+1	Cyclic prefix type during 3, and received signal r (0) delays (L1+L2+2D+2-k) individual sampling point with respect to the desirable timing position of synchronizing signal.
		L1++L2+L3+2D+3≤k≤L1+L2+L3+2D+2	Cyclic prefix type during 3, and received signal r (0) is with respect to leading (k-L1-L2-2D-2) the individual sampling point of the desirable timing position of synchronizing signal
L1+L2+2D+3≤k≤L1+L2+L3+3D+2	Cyclic prefix type during 1, and received signal r (0)

Delay (L1+L2+L3+3D+3-k) individual sampling point with respect to the desirable timing position of synchronizing signal

According to transmission provided by the invention and detection method, described transmitting terminal is the base station, and described receiving terminal is a travelling carriage.

The synchronizing signal of ofdm system provided by the invention sends and detection method, and travelling carriage obtains to have obtained the length type of cyclic prefix of synchronizing signal place OFDM symbol simultaneously in the synchronizing signal process regularly.Need not cyclic prefix type during be detected extra step.Because it is to do that travelling carriage obtains synchronizing signal step regularly, so travelling carriage of the present invention need not increase the cyclic prefix type during that expense just can obtain synchronizing signal; In addition, compare the mode that cyclic prefix type during carries out blind Detecting, method provided by the invention also has easy realization, detects high accuracy for examination.

Description of drawings

Further the present invention is described in detail below in conjunction with the drawings and specific embodiments.

Fig. 1 is the OFDM schematic symbol diagram;

Fig. 2 has first kind of Cyclic Prefix in OFDM System schematic symbol diagram;

Fig. 3 has second kind of Cyclic Prefix in OFDM System schematic symbol diagram;

Fig. 4 comprises the generation schematic diagram of the synchronizing signal of the present invention of corresponding diagram 2;

Fig. 5 comprises the generation schematic diagram of the synchronizing signal of the present invention of corresponding diagram 3;

Fig. 6 comprises synchronization signal detection flow chart of the present invention.

Embodiment

At first, be the synchronizing signal transmission and detection method committed step that the example explanation the present invention is based on orthogonal frequency division multiplexi with two kinds of cyclic prefix type durings:

(1) send: in this system, the size of establishing FFT is 2N, and two kinds of Cyclic Prefix are arranged, and is respectively cyclic prefix type during 1 and type 2, and the sampling point number that comprises in the Cyclic Prefix is respectively: L1, L2.Be without loss of generality, for cyclic prefix type during 1, the synchronizing signal that the system of setting up departments sends sends in an OFDM symbol, its data division is: x (0), x (1) ... .x (2N-1). and satisfy following condition: x (n)=x (n+N), n=0,1...N-1. promptly, this signal is repetition in time domain.If x (0), x (1) ... the x (N) and the cross-correlation R (u) of its cyclic shift are:

$R\left(u\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)x^{*}\left((n+u)\mathrm{mod}N\right)$

When u ≠ 0, Be a very little number, desirable,

R (u) cross-correlation should satisfy following condition:

$R\left(u\right)=\{\begin{array}{c}N,u=0;\\ 0,u\≠0;\end{array}$

For cyclic prefix type during 2, synchronizing signal also sends in an OFDM symbol, and its data division is:

x(m+1)....x(2N-1)，x(0)....x(m).

Wherein, m is a constant, satisfies following condition

m＝L2+D (1)

Wherein, D also is a constant, satisfies following condition:

0≤D≤N-L1-L2-2 (2)

The preferred values of D is:

Expression rounds up to x; (3)

_ x_ represents x is rounded downwards;

(2) receive: at mobile station side, the step that travelling carriage detects synchronizing signal can be described as:

1. thick regularly detect: utilize the time domain repeat property of synchronizing signal to determine the thick timing of synchronizing signal.This step belongs to prior art.This step can be limited in the timing error of synchronizing signal in the Cyclic Prefix scope usually.

2. thin regularly the detection with length type of cyclic prefix detected:

If:

A. the local reference sync signal of travelling carriage is: x ^*(0), x ^*(N-1), x ^*(N-2) ... x ^*(1).

B. according to a thick synchronization signal data that regularly obtains being: r (0) ... r (N-1), r (N) ... r (2N-1). the thin step that detects with length type of cyclic prefix that regularly detects of travelling carriage can be described as:

2.1 calculate and measure c1, c1 is r (0) ... the circular convolution of .r (N-1) and local reference sync signal;

2.2 calculate and measure c2, c2 is r (N) ... the circular convolution of .r (2N-1) and local reference sync signal;

Measure c, c=|c1| 2.3 calculate ²+ | c2| ², | x| represents the mould of x.

2.4 calculate the index of measuring greatest member correspondence among the c: establishing the index of measuring greatest member correspondence among the c is k, 0≤k≤N-1.Travelling carriage can be determined the thin timing position and the cyclic prefix type during of synchronizing signal according to following table:

k	Judgment rule
		0≤k≤L1	Cyclic prefix type during 1, and received signal r (0) is with respect to the leading k of a desirable timing position sampling point of synchronizing signal.
L1+1≤k≤N-L2-D-2	Cyclic prefix type during 2, and received signal r (0) delays (N-L2-D-1-k) individual sampling point with respect to the desirable timing position of synchronizing signal.
		N-L2-D-1≤k≤N-D-1	Cyclic prefix type during 2, and received signal r (0) is with respect to leading (k+L2+D-N) the individual sampling point of the desirable timing position of synchronizing signal.
N-D≤k≤N-1	Cyclic prefix type during 1, and received signal r (0) delays (N-k-1) individual sampling point with respect to the desirable timing position of synchronizing signal.

Table 1

Second step was the example explanation principle of the invention and detailed step with two kinds of cyclic prefix type durings in conjunction with the accompanying drawings:

(1) cyclic prefix type during

Fig. 1 is the OFDM schematic symbol diagram, and the part of filling left oblique line among Fig. 1 in the rectangle frame is the Cyclic Prefix of OFDM symbol.That does not fill content in the rectangle frame is the data division of OFDM symbol, the normally repetition of data division back one piece of data of Cyclic Prefix part.At receiver end, during receiver demodulating ofdm signal, the content of Cyclic Prefix part all can be received machine usually and abandon, and therefore, before demodulation, receiver must obtain the position of the data division of OFDM symbol in advance.

Because the difference of environment, type of service, different cyclic prefix type durings can be selected by system.Fig. 2 sign be a subframe that adopts short Cyclic Prefix (cyclic prefix type during 1), wherein, the part of filling left oblique line in the rectangle frame is the Cyclic Prefix of OFDM symbol, that does not fill content in the rectangle frame is the data division of OFDM symbol; Fig. 3 sign be a subframe that adopts long loop prefix (cyclic prefix type during 2), wherein, the part of filling left oblique line in the rectangle frame is the Cyclic Prefix of OFDM symbol, that does not fill content in the rectangle frame is the data division of OFDM symbol.As shown in Figures 2 and 3, because the difference of circulating prefix-length has 6 OFDM symbols in the subframe of employing long loop prefix, in the subframe of the short Cyclic Prefix of employing 7 OFDM symbols are arranged.LTE system based on the OFDM technology has just adopted and Fig. 2 and the similar frame structure of Fig. 3.For the application scenarios that super covering far away or multicast, broadcast message transmit, system can select the subframe of long loop prefix for use, and at this moment, each subframe has 6 symbols, can reduce the received signal intersymbol interference; For general application, system can select the subframe of short Cyclic Prefix for use, and at this moment, each subframe has 7 symbols, can improve the throughput of system.

(2) send:

Fig. 4 and Fig. 5 adopt the generation schematic diagram of synchronizing signal of the present invention.If the size of FFT is 2N, two kinds of circulation Cyclic Prefix are arranged, be respectively cyclic prefix type during 1 and type 2, the sampling point number that comprises in the Cyclic Prefix is respectively: L1, L2.For cyclic prefix type during 1, the synchronizing signal that system sends sends in an OFDM symbol, and its data division is: x (0), x (1) ... .x (2N-1). and satisfy following condition: x (n)=x (n+N), n=0,1...N-1. promptly, this signal is repetition in time domain.The last L1 of a data division data are copied to the Cyclic Prefix part, as shown in Figure 4.In addition, data x (0), x (1) ... .x (2N-1) satisfies following condition: x (n)=x (n+N), n=0,1...N-1. promptly, this signal is repetition in time domain.If x (0), x (1) ... the x (N) and the cross-correlation R (u) of its cyclic shift are:

$R\left(u\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)x^{*}\left((n+u)\mathrm{mod}N\right)$

When u ≠ 0,

Be a very little number, desirable,

R (u) cross-correlation should satisfy following condition: $R\left(u\right)=\{\begin{array}{c}N,u=0;\\ 0,u\≠0;\end{array}$

Fig. 5 has then provided the generation schematic diagram of synchronizing signal under cyclic prefix type during 2 situations, and for cyclic prefix type during 2, synchronizing signal also sends in an OFDM symbol, and its data division is:

x(m+1)....x(2N-1)，x(0)....x(m).

Here, m is a constant, satisfies following condition:

m＝L2+D (1)

Wherein, D also is a constant, satisfies following condition:

0≤D≤N-L1-L2-2 (2)

The preferred values of D is:

Expression rounds up to x; (3)

_ x_ represents x is rounded downwards:

From top description as can be seen, the data division of the synchronizing signal under cyclic prefix type during 2 situations is the cyclic shift version of data division under cyclic prefix type during 1 situation.Utilize this characteristics, when thick synchronous synchronizing signal and local reference signal carry out circular convolution, for dissimilar Cyclic Prefix, the peak value of circular convolution will be positioned at different positions, and what this can be perfectly clear when the receiving terminal travelling carriage utilizes local reference signal to carry out thin timing finds out.

(3) receive:

At mobile station side, travelling carriage detects synchronizing signal, specifically as shown in Figure 6, may further comprise the steps:

1. synchronously thick:

In step 601, travelling carriage carries out the synchronously thick of synchronizing signal.This step mainly utilizes the time domain repeat property of synchronizing signal to finish.This step belongs to prior art, is summarized as follows, establishing the signal that travelling carriage receives is r (n), r (n+1) ... ...The thick timing of travelling carriage comprises the steps:

1. be calculated as follows and measure:

$M\left(k\right)={\left|\underset{p=0}{\overset{N-1}{\mathrm{\Σ}}}{r}^{*}(n+k+p)r(n+k+p+N)\right|}^2,k=\mathrm{0,1}....2N-1---\left(4\right)$

2. calculate the index that obtains maximum correspondence among the M (k), be made as m, then r (n+m) is exactly the thick timing position of synchronizing signal.

Be without loss of generality, establish

A. the synchronization signal data that obtains according to the thick timing position of synchronizing signal is:

r(0)...r(N-1)，r(N)...r(2N-1).

B. the local reference sync signal sequence of travelling carriage is: x ^*(0), x ^*(N-1), x ^*(N-2) ... x ^*(1).

2. thin regularly detection: the thin timing detection of synchronizing signal and length type of cyclic prefix detect can use step 602～605 to describe:

In step 602, calculate and measure c1, measure c1 and equal r (0) ... the circular convolution of .r (N-1) and local reference sync signal.If c1=(c1 (0), c1 (1) ... c1 (N-1)) ^T, the computing formula of c1 is as follows:

$\mathrm{cl}=\left(\begin{array}{c}c1\left(0\right)\\ \mathrm{cl}\left(1\right)\\ \mathrm{cl}\left(2\right)\\ ...\\ c1(N-1)\end{array}\right)=\left(\begin{array}{ccccc}{x}^{*}\left(0\right),& x^{*}\left(1\right),& x^{*}\left(2\right)& ...& x^{*}(N-1)\\ x^{*}(N-1),& x^{*}\left(0\right),& x^{*}\left(1\right)& ...& x^{*}(N-2)\\ x^{*}(N-2),& x^{*}(N-1),& x^{*}\left(0\right)& ...& x^{*}(N-3)\\ ...& & & & \\ x^{*}\left(1\right),& x^{*}\left(2\right),& x^{*}\left(3\right)& ...& x^{*}\left(0\right)\end{array}\right)\×\left(\begin{array}{c}r\left(0\right)\\ r\left(1\right)\\ r\left(2\right)\\ ...\\ r(N-1)\end{array}\right)---\left(5\right)$

For ease of understanding the method for transmitting synchronizing signal that proposes previously, if the cyclic prefix type during of synchronizing signal is a cyclic prefix type during 1, the synchronization signal data that obtains according to the thick timing position of synchronizing signal is a timing advance version of ideal synchronisation signal, for ease of discussing, this does not consider the influence of channel, if r (0) ... r (N-1),=x (N-m), x (N-m+1) ... x (N-1) ... x (N-m-1), m=0,1.2...L1. observe the circular convolution formula (5) of front, utilize the relevant character of previously described synchronizing signal cyclic shift

When u ≠ 0,

Be a very little number, desirable,

( $R\left(u\right)=\{\begin{array}{c}N,u=0;\\ 0,u\≠0;\end{array}$ ), can find, as x (N-m), x (N-m+1) ... x (N-1) ... after .x (N-m-1) carries out circular convolution with local reference signal, the peak value of circular convolution c1 will be positioned at m the element position place of c1.

See another hypothesis again, if the cyclic prefix type during of synchronizing signal is a cyclic prefix type during 1, the synchronization signal data that obtains according to the thick timing position of synchronizing signal is a version behind the fixed response time of ideal synchronisation signal, if r (0) ... r (N-1),=x (p), x (p+1) ... x (N-1), x (0) ... .x (p-1) .p=1,2...P. (P is a number behind the fixed response time of maximum possible, it may be noted that the time, the synchronizing signal that is used to send has the time domain repeat property, travelling carriage is according to the thick synchronizing signal that regularly obtains, overwhelming majority situations are timing advance versions of ideal synchronisation signal, because previously described coarse synchronization signal belongs to ripe algorithm, no longer it are carried out deep description here) observe the circular convolution formula (5) of front, can find, as x (N-p), x (N-p+1) ... x (N-1) ... after .x (N-p-1) carries out circular convolution with local reference signal, the peak value of circular convolution c1 will be positioned at (N-p) individual element position place of c1.

See the third hypothesis again, if the cyclic prefix type during of synchronizing signal is a cyclic prefix type during 2, the data division of establishing the synchronizing signal of transmission is: x (L2+D+1) ... .x (N-1), x (0) ... x (L2+D), x (L2+D+1) ... .x (N-1), x (0) ... x (L2+D).The synchronization signal data that obtains according to the thick timing position of synchronizing signal is a timing advance version of ideal synchronisation signal, establishes

r(0)...r(N-1)，＝x(L2+D+1-m)，x(L2+D+1-m+1)...x(N-1)，x(0)....x(m-1).M＝0，1....L2。Observe the circular convolution formula (5) of front, can find, as x (L2+D+1-m), x (L2+D+1-m+1) ... x (N-1), x (0) ... after .x (m-1) carries out circular convolution with local reference signal, the peak value of circular convolution c1 will be positioned at (N-L2-D-1+m) individual element position place of c1.

See the 4th kind of hypothesis again, if the cyclic prefix type during of synchronizing signal is a cyclic prefix type during 2, the data division of establishing the synchronizing signal of transmission is: x (L2+D+1) ... .x (N-1), x (0) ... x (L2+D), x (L2+D+1) ... .x (N-1), x (0) ... x (L2+D).The synchronization signal data that obtains according to the thick timing position of synchronizing signal is a version behind the fixed response time of ideal synchronisation signal, establishes

R (0) ... r (N-1),=x (L2+D+1+p), x (L2+D+1+p+1) ... x (N-1), x (0) ... .x (L2+D+p). observe the circular convolution formula (5) of front, can find, as x (L2+D+1+p), x (L2+D+1+p+1) ... x (N-1), x (0) ... after .x (L2+D+p) carries out circular convolution with local reference signal, the peak value of circular convolution c1 will be positioned at (N-L2-D-1-p) individual element position place of c1.

From top analysis as can be seen, the synchronizing signal by rational design cycle prefix types 2 is with respect to the time-delay of cyclic prefix type during 1, and travelling carriage can carry out carefully obtaining length type of cyclic prefix in regularly to synchronizing signal.As previously mentioned, travelling carriage is according to the thick synchronizing signal that regularly obtains, and most situations are timing advance versions of ideal synchronisation signal, therefore, needs emphasis to consider for the situation of this timing advance.When timing advance, for cyclic prefix type during 1, the peak value index range of circular convolution c1 is [0, L1].For fear of obscuring, for cyclic prefix type during 2, the peak value index expected range of circular convolution c1 should be [L1+1, N-1], and in order to reach this purpose, cyclic prefix type during 2 should satisfy following relation with respect to the cyclic shift number of cyclic prefix type during 1:

L2≤m≤N-L1-2 (6)

Do not lose generality, establish m=L2+D, D then needs to satisfy above-mentioned formula (2), that is:

0≤D≤N-L1-L2-2

At this moment, for cyclic prefix type during 2, the peak value index range of circular convolution c1 is [N-L2-D-1, N-D-1].

Also have N-L1-L2-2 position can be used for the situation of constant time lag is judged this moment, when D gets preferred values (formula 3), that is:

Expression x rounds up;

_ x_ table does not round downwards x;

The scope of the maximum constant time lag that travelling carriage can be judged is identical for cyclic prefix type during 1/2.

Certainly, according to digital signal processing theory, r (N-1) ... .r (0) can utilize Fourier transform efficiently to realize with the circular convolution of local reference sync signal.

In step 603, calculate and measure c2, r (N) ... the circular convolution of .r (2N-1) and local reference sync signal.Computational methods and step 402 are identical.

What need part is, this step is not must step, such as, the signal to noise ratio of the residing channel of travelling carriage is very high, and this step just can omit.

In step 604, calculate and measure c, c=|c1| ²+ | c2| ², | x| represents the mould of x.When step 403 is omitted, c=|c1| ²

In step 605, calculate the index of measuring greatest member correspondence among the c: establishing the index of measuring greatest member correspondence among the c is k, 0≤k≤N-1.Because the synchronizing signal that cyclic prefix type during 2 sends is the cyclic shift version of cyclic prefix type during 1, cyclic prefix type during, received signal r (0) the synchronism deviation binary function with respect to the desirable timing position of synchronizing signal can be thought in the index of measuring greatest member correspondence among the c, and travelling carriage can be determined the thin timing position and the cyclic prefix type during of synchronizing signal according to following table:

k	Judgment rule
		0≤k≤L1	Cyclic prefix type during 1, and received signal r (0) is with respect to the leading k of a desirable timing position sampling point of synchronizing signal.
L1+1≤k≤N-L2-D-2	Cyclic prefix type during 2, and received signal r (0) delays (N-L2-D-1-k) individual sampling point with respect to the desirable timing position of synchronizing signal.
		N-L2-D-1≤k≤N-D-1	Cyclic prefix type during 2, and received signal r (0) is with respect to leading (k+L2+D-N) the individual sampling point of the desirable timing position of synchronizing signal.
N-D≤k≤N-1	Cyclic prefix type during 1, and received signal r (0) delays (N-k-1) individual sampling point with respect to the desirable timing position of synchronizing signal.

Table 1

At last, the present invention is not restricted to two kinds of cyclic prefix type durings, can any multiple cyclic prefix type during, and the most preferred embodiment with three kinds of cyclic prefix type durings is that example further specifies the present invention below:

(1) cyclic shift

If the size of FFT is 2N, three kinds of Cyclic Prefix are arranged, be respectively cyclic prefix type during 1,2 and 3, the sampling point number that comprises in the Cyclic Prefix is respectively: L1, L2, L3.Be without loss of generality,

1. for cyclic prefix type during 1, the synchronizing signal that the system of setting up departments sends sends in an OFDM symbol, and its data division is: x (0), x (1) ... .x (2N-1). and satisfy following condition: x (n)=x (n+N), n=0,1...N-1. promptly, this signal is repetition in time domain.If x (0), x (1) ... the x (N) and the cross-correlation R (u) of its cyclic shift are:

$R\left(u\right)=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(n\right)x^{*}\left((n+u)\mathrm{mod}N\right)$

When u ≠ 0, Be a very little number, desirable,

R (u) cross-correlation should satisfy following condition:

$R\left(u\right)=\{\begin{array}{c}N,u=0;\\ 0,u\≠0;\end{array}$

2. for cyclic prefix type during 2, synchronizing signal also sends in an OFDM symbol, and its data division is:

x(m+1)....x(2N-1)，x(0)....x(m).

Wherein, m preferred values is:

m＝N-L1-D-1.

Expression rounds up to x;

_ x_ represents x is rounded downwards;

(1’)

3. for cyclic prefix type during 3, synchronizing signal also sends in an OFDM symbol, and its data division is:

x(p+1)....x(2N-1)，x(0)....x(p).

Wherein, p preferred values is:

p＝N-L1-L2-2D-2.

Expression rounds up to x;

_ x_ represents x is rounded downwards;

(1”)

(2) rule of correspondence

k	Judgment rule
		0≤k≤L1	Cyclic prefix type during 1, and received signal r (0) is with respect to the leading k of a desirable timing position sampling point of synchronizing signal.
L1+1≤k≤L1+D	Cyclic prefix type during 2, and received signal r (0) delays (L1+D+1-k) individual sampling point with respect to the desirable timing position of synchronizing signal.
		L1+D+1≤k≤L1+D+1+L2	Cyclic prefix type during 2, and received signal r (0) is with respect to leading (k-L1-D-1) the individual sampling point of the desirable timing position of synchronizing signal.
L1+L2+D+2≤k≤L1++L2+2D+1	Cyclic prefix type during 3, and received signal r (0) delays (L1+L2+2D+2-k) individual sampling point with respect to the desirable timing position of synchronizing signal.
		L1++L2+L3+2D+3≤k≤L1+L2+L3+2D+2	Cyclic prefix type during 3, and received signal r (0) is with respect to leading (k-L1-L2-2D-2) the individual sampling point of the desirable timing position of synchronizing signal
L1+L2+2D+3≤k≤L1+L2+L3+3D+2	Cyclic prefix type during 1, and received signal r (0) delays (L1+L2+L3+3D+3-k) individual sampling point with respect to the desirable timing position of synchronizing signal

。

Table 2

Claims (10)

1, a kind of synchronizing signal of ofdm system sends and detection method, it is characterized in that, receiving terminal carries out cyclic prefix type during synchronously simultaneously and detects, and may further comprise the steps:

1.1) transmitting terminal carries out cyclic shift to the data division of synchronizing signal by cyclic prefix type during makes it be positioned at diverse location at the peak value that receiving terminal and local reference signal carry out circular convolution;

1.2) receiving terminal distinguishes according to described diverse location in carrying out the synchronization timing process and restore described cyclic prefix type during.

According to described transmission of claim 1 and detection method, it is characterized in that 2, described synchronization timing process is used local reference sync signal x ^*(0), x ^*(N-1), x ^*(N-2) ... x ^*(1), comprise following concrete steps:

2.1) utilize standard sync signal time domain repeat property to determine the thick timing data of synchronizing signal

r(0)...r(N-1)，r(N)...r(2N-1)；

2.2) calculate that to measure c1:c1 be r (0) ... .r (N-1) and local reference sync signal

x ^*(0), x ^*(N-1), x ^*(N-2) ... x ^*(1) circular convolution;

2.3) calculate and measure c, c=|c1| ², | x| represents the mould of x, and x is any expression formula;

2.4) calculate the index k measure greatest member correspondence among the c, according to the number range of k and described

The thin timing position and the cyclic prefix type during of the rule of correspondence decision synchronizing signal of circular convolution peak value rule development.

3, according to described transmission of claim 2 and detection method, it is characterized in that described step 2.2) comprise that also it is r (N) that c2:c2 is measured in calculating ... .r (2N-1) and local reference sync signal x ^*(0), x ^*(N-1), x ^*(N-2) ... x ^*(1) circular convolution; Described step 1.3) and 1.4) in measure c=|c1| ²+ | c2| ²

4, according to described transmission of claim 2 and detection method, it is characterized in that described step 2.1) comprising:

2.1.1) calculate and measure M (k): $M\left(k\right)={\left|\underset{p=0}{\overset{N-1}{\mathrm{\Σ}}}{r}^{*}(n+k+p)r(n+k+p+N)\right|}^2,k=\mathrm{0,1}....2N-1;$

2.1.2) calculate the index that obtains maximum correspondence among the M (k), be made as m, then r (n+m) is exactly the thick timing position of synchronizing signal;

2.1.3) obtain the thick timing data of synchronizing signal according to thick timing position: r (0) ... r (N-1), r (N) ... r (2N-1).

According to described transmission of claim 2 and detection method, it is characterized in that 5, described circular convolution is:

$c1=\begin{array}{}\end{array}\left[\begin{array}{c}c1\left(0\right)\\ c1\left(1\right)\\ c1\left(2\right)\\ \…\\ c1(N-1)\end{array}\right]=\left[\begin{array}{ccccc}{x}^{*}\left(0\right),& x^{*}\left(1\right),& x^{*}\left(2\right)& \…& x^{*}(N-1)\\ x^{*}(N-1),& x^{*}\left(0\right),& x^{*}\left(1\right)& \…& x^{*}(N-2)\\ x^{*}(N-2),& x^{*}(N-1),& x^{*}\left(0\right)& \…& x^{*}(N-3)\\ \…& & & & \\ x^{*}\left(1\right),& x^{*}\left(2\right),& x^{*}\left(3\right)& \…& x^{*}\left(0\right)\end{array}\right]\×\left[\begin{array}{c}r\left(0\right)\\ r\left(1\right)\\ r\left(2\right)\\ \…\\ r(N-1)\end{array}\right].$

6, according to described transmission of claim 1 and detection method, it is characterized in that, described cyclic prefix type during is two kinds, circulating prefix-length is respectively L1 and L2, corresponding described cyclic shift is respectively 0 and the m+1 position that moves to left, corresponding described data division is respectively ideal synchronisation signal x (0), x (1) ... the .x (2N-1) and the synchronizing signal x (m+1) that moves to left ... .x (2N-1), x (0) ... .x (m); M=L2+D, 0≤D≤N-L1-L2-2,2N are the length of described data division.

7, according to described transmission of claim 5 and detection method, it is characterized in that D gets optimal value:

Expression rounds up to x;

_ x_ represents x is rounded downwards.

8, according to claim 2,4 or 6 described transmission and detection methods, it is characterized in that the described rule of correspondence is:

K Judgment rule 0≤k≤L1 Cyclic prefix type during 1, and received signal r (0) is with respect to the leading k of a desirable timing position sampling point of synchronizing signal. L1+1≤k≤N-L2-D-2 Cyclic prefix type during 2, and received signal r (0) delays (N-L2-D-1-k) individual sampling point with respect to the desirable timing position of synchronizing signal N-L2-D-1≤k≤N-D-1 Cyclic prefix type during 2, and received signal r (0) is with respect to synchronously

Leading (k+L2+D-N) the individual sampling point of the desirable timing position of signal. N-D≤k≤N-1 Cyclic prefix type during 1, and received signal r (0) delays (N-k-1) individual sampling point with respect to the desirable timing position of synchronizing signal.

According to described transmission of claim 1 and detection method, it is characterized in that 9, described cyclic prefix type during can be three kinds, circulating prefix-length is respectively L1, L2 and L3, corresponding described cyclic shift is respectively 0, move to left the m+1 position and the p+1 position that moves to left, m=N-L1-D-1, p=N-L1-L2-2D-2;

Wherein,

Expression rounds up to x;

_ x_ represents x is rounded downwards.

10, according to claim 2 or 9 described transmission and detection methods, it is characterized in that the described rule of correspondence is:

k Judgment rule 0≤k≤L1 Cyclic prefix type during 1, and received signal r (0) is with respect to the leading k of a desirable timing position sampling point of synchronizing signal. L1+1≤k≤L1+D Cyclic prefix type during 2, and received signal r (0) delays (L1+D+1-k) individual sampling point with respect to the desirable timing position of synchronizing signal. L1+D+1≤k≤L1+D+1+L2 Cyclic prefix type during 2, and received signal r (0) is with respect to leading (k-L1-D-1) the individual sampling point of the desirable timing position of synchronizing signal. L1+L2+D+2≤k≤L1++L2+2D+1 Cyclic prefix type during 3, and received signal r (0) delays (L1+L2+2D+2-k) individual sampling point with respect to the desirable timing position of synchronizing signal.

L1++L2+L3+2D+3≤k≤L1+L2+L3+2D+2 Cyclic prefix type during 3, and received signal r (0) is with respect to leading (k-L1-L2-2D-2) the individual sampling point of the desirable timing position of synchronizing signal L1+L2+2D+3≤k≤L1+L2+L3+3D+2 Cyclic prefix type during 1, and received signal r (0) delays (L1+L2+L3+3D+3-k) individual sampling point with respect to the desirable timing position of synchronizing signal

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