CN101656702A

CN101656702A - Method for processing signals to be transmitted

Info

Publication number: CN101656702A
Application number: CN 200910092994
Authority: CN
Inventors: 陆涛; 范建晓
Original assignee: Potevio Institute of Technology Co Ltd
Current assignee: Petevio Institute Of Technology Co ltd
Priority date: 2009-09-21
Filing date: 2009-09-21
Publication date: 2010-02-24
Anticipated expiration: 2029-09-21
Also published as: CN101656702B

Abstract

The present invention discloses a method for processing signals to be transmitted, suitable for application scenes that the signal to be transmitted is a ZC sequence and the ZC sequence needs to be transformed into a corresponding DFT sequence. The method determines a multiplication inverse element u<-1> of the ZC sequence and a for making an equality of u*u<-1> = a*Nzc + 1 to be tenable accordingto a physical root sequence number u of the ZC sequence to be transmitted, and calculates a sequence sum of the ZC sequency: Xn(0) and generates a conjugation sequence x<*>u<-1>(k) of xu<-1>(k), thenjudges according to the odevity of u<-1> and a, when a is odd and u<-1> is even, a formula (I) is used as the DFT sequence of the ZC sequency, otherwise a formula (II) is used as the DFT sequence ofthe ZC sequence; wherein Cv is a cyclic shift value of the ZC sequence. By means of the invention, it is capable of reducing operation complex degrees and operation quantities of a signal transmissionterminal, and improving efficiency of signal transmission of the signal transmission terminal.

Description

Method for processing signal to be transmitted

Technical Field

The present invention relates to LTE technology, and in particular, to a method for processing a signal to be transmitted.

Background

The current fourth generation mobile communication standards are mostly based on Orthogonal Frequency Division Multiple Access (OFDMA) technology. Since OFDMA is sensitive to synchronization, it is necessary to transmit a specific synchronization signal on the subcarriers of OFDM. In view of the power and computation-constrained characteristics of mobile Stations (UEs), there is a need to provide an efficient synchronization signal generation method at the transmitting end of the uplink of a communication system (i.e., UE end). The Zadoff-chu (zc) sequence has good characteristics of ideal auto-correlation (ACF) and constant-modulus cross-correlation (CCF), wherein the constant-modulus cross-correlation characteristic can reduce interference between access users, the ideal auto-correlation characteristic facilitates a receiver to obtain an accurate uplink timing estimate, and the good characteristic of cross-correlation facilitates access detection of a physical layer. Therefore, in the LTE system, ZC sequences in the frequency domain are adopted as an uplink synchronization signal, an uplink random access signal, a downlink primary synchronization signal, and the like. The ZC sequence is briefly introduced below:

the u-th length being N_zc(N_zcPrime) is defined as follows:

in the formula (1), u represents a physical root index (physical root index) and has a value range of u belonging to [1, N ∈ [_ZC-1]。

According to the properties of the ZC sequences, the ZC sequences generated by different physical root sequence numbers have good characteristics of ideal autocorrelation and constant modulus cross correlation, and the ZC sequences obtained by performing cyclic shift on the same ZC root sequence by adopting different cyclic shift values also have good correlation characteristics. The following gives a definition of the cyclic shift of the ZC root sequence. From the u-th ZC root sequence through C_vThe bit cyclic shift can obtain a ZC sequence x (n) shown in the formula (2):

in practical application, a signal transmitting end generally needs to transform a ZC sequence shown in formula (2) to a frequency domain to obtain a ZC sequence of the frequency domain, and then perform subsequent corresponding processing on the ZC sequence of the frequency domain and transmit the ZC sequence of the frequency domain to the outside. Taking uplink transmission in the LTE system as an example, the DFT-SC-OFDM scheme is adopted, that is to say: the ZC sequence is first converted into a frequency domain by Discrete Fourier Transform (DFT), and then subjected to carrier mapping, IFFT, and Cyclic Prefix (CP) processing to be an OFDM signal, which is transmitted to the outside. The uplink signal includes: uplink access signals, uplink reference signals, and control signaling of a Physical Uplink Control Channel (PUCCH).

For example: when the UE adopts the ZC sequence of the frequency domain to carry out random access, the ZC sequence at the moment is called a random access leader sequence, firstly, the ZC sequence of the time domain shown in the formula (2) needs to be converted into the frequency domain, and then, the subsequent processing is carried out. And vice versa in other application scenarios.

When a ZC sequence in the time domain is transformed to the frequency domain using DFT transform, the ZC sequence in the frequency domain obtained by the transformation may be referred to as a DFT sequence corresponding to the ZC sequence. According to the prior art, for N_zcPoint ZC sequence x (N), N ═ 0, 1, …, N_zc-1, N thereof_zcThe point DFT transform is shown in equation (3):

at the signal receiving end, the discrete signal shown in formula (3) may be transformed from the frequency domain to the time domain by using Inverse Discrete Fourier Transform (IDFT), which is defined as shown in formula (4):

as can be seen from the equations (3) and (4), the DFT conversion of the N-point ZC sequence requires N²The number of complex multiplications and the number of N (N-1) complex additions are very large.

If one considers a transform using the Fast Fourier Transform (FFT), the FFT transform can only reduce the computational complexity to

Complex multiplications and nlog (n) complex additions. However, the FFT transform requires the number of points N of the sequence participating in the transform to be 2^p(p is an integer), therefore, for a ZC sequence with a prime length, the length of the sequence needs to be extended to 2 by performing operations such as zero padding and the like first^pLength, and resampling of the transform result of the FFT transform to obtain the desired transform result of the DFT transform. It can be seen that if FFT is used, it will result in a large redundancy complexity and require resampling.

Disclosure of Invention

In view of this, the present invention provides a method for processing a signal to be transmitted, which is suitable for an application scenario where the signal to be transmitted is a ZC sequence and the ZC sequence needs to be converted into a corresponding DFT sequence, so as to reduce the computation complexity and the computation workload of a signal transmitting end and improve the efficiency of the signal transmitting end for transmitting the signal.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a method for processing a signal to be transmitted is suitable for an application scenario in which the signal to be transmitted is a Zadoff-Chu sequence and the Zadoff-Chu sequence needs to be transformed into a corresponding Discrete Fourier Transform (DFT) sequence, and the method comprises the following steps:

A. according to the physical root sequence number of the Zadoff-Chu sequence to be sent: u, determining corresponding u^-1And a; wherein,

u*u^-1＝a*N_zc+1

u^-1is an integer, is the multiplicative inverse of u, u^-1∈[1，N_ZC-1]；

N_zcIs a prime number, is the length of the Zadoff-Chu sequence;

a is an integer;

B. calculating the sequence of the Zadoff-Chu sequence to be sent and: x_u(0)；

C. By u^-1Generating a corresponding Zadoff-Chu root sequence for the physical root sequence number:

open and close

And (3) taking conjugation to obtain a corresponding conjugated sequence:

wherein k is 0, 1, …, N_zc-1；

D. According to u^-1And parity of a, when a is odd and u is odd^-1When the number is even, will

As DFT sequence corresponding to the Zadoff-Chu sequence, otherwise, it will

As a DFT sequence corresponding to the Zadoff-Chu sequence; wherein, C_vIs the cyclic shift value of the Zadoff-Chu sequence.

The method may further comprise: prestoring logical root sequence numbers and u^-1Corresponding relation of (2), and format and N of signal to be transmitted_zcThe corresponding relationship of (a);

before A, further comprising: a0, acquiring the format and the logic root serial number of the signal to be sent through signaling interaction, and according to the acquired format of the signal to be sent and the pre-stored format and N of the signal to be sent_zcDetermining the length N of the Zadoff-Chu sequence_zcAccording to the obtainedLogical root sequence number and pre-stored logical root sequence numbers and u^-1Determining the physical root sequence number of the Zadoff-Chu sequence to be sent: u and u^-1。

Preferably, the signal to be transmitted includes: an upstream signal and a downstream signal.

The uplink signal may include: uplink random access signals, uplink reference signals and control signaling of a physical uplink control channel.

The downlink signal may include: and (3) descending the main synchronous signal.

According to the technical scheme, the periodicity and the multiplication inverse element characteristics of the ZC sequence are fully utilized, and the method only needs 2N_zcThe method can convert the ZC sequence with prime number length into the corresponding DFT sequence by the secondary complex multiplication, thereby greatly saving the operation complexity and the operation amount of the sending end and improving the signal sending efficiency of the sending end when the sending end needs to carry out DFT conversion on the ZC sequence to be sent.

Drawings

Fig. 1 is a schematic flow chart of a method for processing a signal to be transmitted according to the present invention;

fig. 2 is a flowchart illustrating a method for processing a random access preamble sequence according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and examples.

The main idea of the invention is as follows: the periodicity and multiplication inverse element characteristics of the ZC sequence are fully utilized, and a method which only needs 2N is provided_zcThe ZC sequence with prime length can be converted into corresponding sequence by multiple multiplicationThe method of DFT sequence in the invention can greatly save the operation complexity and operation amount of the sending end and improve the signal sending efficiency of the sending end when the sending end needs to carry out DFT conversion on the ZC sequence to be sent.

Two key characteristics of ZC sequences are first derived: periodicity and multiplicative inverse characteristics.

1. The periodicity is as follows: according to formula (2), there are:

x (n + N_{ZC})

because of N_zcIs prime number, so (2N + N)_zc+1) is an even number, and therefore equation (6) holds for any n.

<math> <mrow> <mi>x</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>N</mi> <mi>ZC</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>juπ</mi> <mfrac> <mrow> <mi>n</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> <msub> <mi>N</mi> <mi>ZC</mi> </msub> </mfrac> </mrow> </msup> <mo>=</mo> <mi>x</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>,</mo> <mo>&ForAll;</mo> <mi>n</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow> </math>

2. Multiplicative inverse characteristics:

from the multiplicative inverse property, for a physical root sequence number u, there is u^-1So that equation (7) holds:

u*u^-1＝a*N_zc+1 (7)

in the formula (7), u^-1And a is an integer, u^-1∈[1，N_ZC-1]。

Define suchIs a ZC sequence pair.

ZC sequence x (N), N ═ 0, 1, …, N_zcThe DFT transform of-1 is shown as formula (3), and the formula (3) is collated to obtain:

(8)

defining the sequence:

this sequence represents a ZC sequence: x is the number of_u(u^-1k) Conjugation of (1). x is the number of_u(u^-1k) Is from the u-th length to N_zcStarting at point 1 of the ZC root sequence of^-1Taking 1 point, and periodically circulating until N is enough_zcDot the resulting sequence. Since the ZC root sequence has periodicity, even in u^-1The value of k exceeds [1, N_ZC-1]In the case of ranges, the above defined sequence is still true.

The multiplication inverse element characteristic of the ZC sequence is utilized to obtain a relational expression shown in the formula (9):

the proof of equation (9) is as follows, right side of equation:

(due to the fact that

)

(10)

= X_{u} (k)

As can be seen, equation (9) holds. The second factor on the right hand side of the equation shown in equation (9) is the pair x_u(n) summing the sequences obtained after cyclic shift by a value u^-1k. Since summing the sequences after the cyclic shift is equal to summing the sequences before the cyclic shift, therefore:

= X_{u} (0)

looking again at the first factor x on the right side of the equation shown in equation (9)_u ^*(u^-1k) It is simplified according to its definition:

x_{u}^{*} (u^{- 1} k)

in the formula (12), the second part

This is equivalent to the pair

By one (1-u)^-1) Frequency offset of/2; the value of the third part is +/-1 and can be regarded as a phase correction factor. The phase correction factor

Is taken from u^-1A and k are determined together as follows:

1) when a is an even number, the number of the bits is,

2) when a is an odd number, if u^-1Is odd, then no matter k is odd or even, there is always

3) When a is an odd number, if u^-1Is even, then when k is even,

when k is an odd number, the number of the bits is,

therefore, in this case, it is equivalent to correcting the odd-numbered sequence values, and in practical use, it can be simplified to (-1)^k。

As can be seen, this part of the decision is based on u^-1The parity of a and k determines whether to adjust the sign of the value, and the complexity is very small. Wherein u is^-1And a is uniquely determined by a physical root sequence number u of the corresponding ZC root sequence.

In summary, the DFT sequence corresponding to the ZC root sequence is equivalent to:

X_{u} (k)

in practical application, ZC root sequence is often adopted to pass through C_vThe ZC sequence x (n) generated by the bit cyclic shift is subjected to frequency domain transformation to obtain a signal to be transmitted, as shown in formula (2). The following explains the principle of DFT fast conversion of ZC sequences after cyclic shift. According to formula (2):

X (k)

(according to formula (12))

Compared with the DFT sequence of the ZC root sequence shown in the formula (13), the ZC sequence after cyclic shift only needs to multiply one frequency offset factorIn the formula (14), the phase correction factorThe value of (b) is the same as that in the ZC root sequence already discussed above, and is also represented by u^-1Parity of a and k.

In summary, referring to equations (13) and (14), X is the root sequence of a specific ZC_u[0]Andis fixed, phase corrected

Fixed 1 for some root sequences, odd for a only, and u^-1Even-numbered root sequences have a corrective effect. Thus, the simplified DFT transform method described above according to the present invention is applied to each X [ k ]]Only 2 complex multiplications are required, with a total of 2N for the entire sequence_zcThe secondary complex multiplication does not need complex addition, and compared with the existing DFT conversion method and FFT conversion method, the operation complexity and the operation amount for converting the ZC sequence into the DFT sequence are greatly simplified.

The method of the present invention is described in detail below based on the conclusions derived from the above formulas.

Fig. 1 is a flow chart illustrating a method for processing a signal to be transmitted according to the present invention. Referring to fig. 1, the method is applicable to an application scenario in which a signal to be transmitted is a ZC sequence and the ZC sequence needs to be converted into a corresponding DFT sequence, and includes:

step 101: according to the physical root sequence number of the Zadoff-Chu sequence to be sent: u, determining corresponding u^-1And a; wherein,

u*u^-1＝a*N_zc+1

u^-1is an integer, is the multiplicative inverse of u, u^-1∈[1，N_ZC-1]；

N_zcIs a prime number, is the length of the Zadoff-Chu sequence;

a is an integer.

Step 102: calculating the sequence of the Zadoff-Chu sequence to be transmitted and: x_u(0)。

Step 103: by u^-1Generating a corresponding Zadoff-Chu root sequence for the physical root sequence number:and to

And (3) taking conjugation to obtain a corresponding conjugated sequence:

wherein k is 0, 1, …, N_zc-1。

Step 104: according to u^-1And parity of a, when a is odd and u is odd^-1If so, go to step 105, otherwise, go to step 106.

Step 105: will be provided with

Step 106: will be provided with

The method for processing a signal to be transmitted according to the present invention is completed. After the DFT sequence corresponding to the ZC sequence is obtained, the DFT sequence can be used to participate in subsequent corresponding processing. For example: taking the uplink transmission in the LTE system described in the background art as an example, after the DFT sequence of the ZC sequence to be transmitted is obtained by the method of the present invention, the DFT sequence can be processed by carrier mapping, IFFT, and CP to become an OFDM signal, and the OFDM signal is transmitted to the outside.

The execution order of steps 101-103 in FIG. 1 can be changed, only by ensuring that step 101 is executed before step 103 is executed, since u determined in step 101 is used in step 103^-1. For example: step 102 may be performed first, then step 101, and finally step 103.

In practical applications, some signaling interaction may be needed to obtain some information for determining u and N_zcThe sender of the signal may need to store the information together with u, and the information together with N locally_zcSo that the signal transmitting end determines u and N_zc. For example:

the method of the present invention shown in FIG. 1 can pre-store the logical root sequence number and u^-1Corresponding relation of (2), and format and N of signal to be transmitted_zcCorresponding relationship of；

And further comprising, prior to step 101: acquiring the format and the logic root serial number of a signal to be sent through signaling interaction, and according to the acquired format of the signal to be sent, the pre-stored format of the signal to be sent and the N_zcDetermining the length N of the Zadoff-Chu sequence_zcAccording to the obtained logical root serial number and the prestored logical root serial numbers and u^-1Determining the physical root sequence number of the Zadoff-Chu sequence to be sent: u and u^-1。

The signal to be transmitted of the present invention may include: the uplink signal and the downlink signal can be processed by using the technical scheme of the invention as long as the signal adopts the ZC sequence and the ZC sequence needs DFT conversion before being transmitted. The uplink signal may include: uplink random access signals, uplink reference signals, control signaling of a physical uplink control channel, and the like, where the downlink signals may include: a downlink primary synchronization signal, etc.

The following describes how to apply the technical solution of the present invention to a process of sending a random access preamble sequence by a UE in an LTE system through a specific embodiment.

In the standard discussion of LTE random access, to ensure the optimization performance of ZC sequences and reduce mutual interference, it is finally determined that for random access preamble sequence formats 0-3, a prime number 839 is taken as the length of ZC sequences, and for random access preamble sequence format 4, a prime number 139 is taken as the length of ZC sequences, and the specific generation process is specified in 3GPP TS 36.211.

Fig. 2 is a flowchart illustrating a method for processing a random access preamble sequence according to an embodiment of the present invention. Referring to fig. 2, the method includes:

step 201: according to section 5.7 of 3GPP TS 36.211, the UE obtains the format, logical root index (r) and cyclic shift parameter N of the random access preamble sequence through a high-level instruction_CS。

Typically, the UE will be pre-stored locallyStoring the corresponding relation between the format of the random access leader sequence and the length of the ZC sequence, and the logical root sequence number and u^-1Usually in the form of a table. In this embodiment, the cyclic shift parameter N_CSFor calculating cyclic shift values C as described previously_v。

Step 202: determining the length N of ZC sequence according to the format of random access leader sequence_zcAnd determining u and u by looking up corresponding tables according to the logical root sequence number^-1Thereby determining a.

Step 203: judgment of N_CSIf it is 0, go to step 205, otherwise go to step 204.

Step 204: according to N defined in 3GPP TS 36.211_CSAnd C_vCalculation of the relationship between C_vStep 206 is performed.

In particular, N_CSAnd C_vThe relationship between them is:

step 205: c is to be_vIs set to 0.

Step 206: by u^-1Generating a corresponding Zadoff-Chu root sequence for the physical root sequence number:

and to

And (3) taking conjugation to obtain a corresponding conjugated sequence:

wherein k is 0, 1, …, N_zc-1。

Step 207: calculating the sum of the sequences of the ZC sequences: x_u(0)。

Step 208: according to u^-1And parity of a, when a is odd and u is odd^-1If it is even, step 209 is performed, otherwise step 210 is performed.

Step 209: will be provided with

As a DFT sequence corresponding to a random access preamble sequence.

Step 210: will be provided with

As a DFT sequence corresponding to a random access preamble sequence.

This concludes the method for processing random access preamble sequence in this embodiment.

Taking the length of the random access preamble sequence 839 as an example, if the conventional DFT conversion is performed on the random access preamble sequence, the random access preamble sequence needs to be processedGo on to 839²The complex multiplication and 839 × 838 complex addition, using FFT, need to extend the length of the random access preamble sequence to 1024, and need to do so

Multiple complex multiplications and 1024log (1024) complex additions. The technical scheme provided by the invention is applied to processing, and only 2 x 839 times of complex multiplication are needed.

As can be seen from the above embodiments, the present invention fully utilizes the periodicity and multiplicative inverse characteristics of ZC sequences, and proposes a method that only 2N is needed_zcThe method can convert the ZC sequence with prime number length into the corresponding DFT sequence by the secondary complex multiplication, thereby greatly saving the operation complexity and the operation amount of the sending end and improving the signal sending efficiency of the sending end when the sending end needs to carry out DFT conversion on the ZC sequence to be sent.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for processing a signal to be transmitted is suitable for an application scenario in which the signal to be transmitted is a Zadoff-Chu sequence and the Zadoff-Chu sequence needs to be transformed into a corresponding Discrete Fourier Transform (DFT) sequence, and the method comprises the following steps:

u*u^-1＝a*N_zc+1

u^-1is an integer, is the multiplicative inverse of u, u^-1∈[1，N_ZC-1]；

N_zcIs a prime number, is the length of the Zadoff-Chu sequence;

a is an integer;

and to

And (3) taking conjugation to obtain a corresponding conjugated sequence:

wherein k is 0, 1, …, N_zc-1；

As DFT sequence corresponding to the Zadoff-Chu sequence, otherwise, it will

2. The method of claim 1, wherein:

the method further comprises the following steps: prestoring logical root sequence numbers and u^-1Corresponding relation of (2), and format and N of signal to be transmitted_zcThe corresponding relationship of (a);

before A, further comprising: a0, obtaining the format and logic root serial number of the signal to be sent through signaling interaction, and obtaining the format and logic root serial number of the signal to be sent according to the obtained format and logic root serial number of the signal to be sentFormat and N of signal to be transmitted stored in advance_zcDetermining the length N of the Zadoff-Chu sequence_zcAccording to the obtained logical root serial number and the prestored logical root serial numbers and u^-1Determining the physical root sequence number of the Zadoff-Chu sequence to be sent: u and u^-1。

3. The method according to claim 1 or 2, characterized in that:

the signal to be transmitted comprises: an upstream signal and a downstream signal.

4. The method of claim 3, wherein:

the uplink signal includes: uplink random access signals, uplink reference signals and control signaling of a physical uplink control channel.

5. The method of claim 3, wherein:

the downlink signal includes: and (3) descending the main synchronous signal.