CN101453237B - Method and apparatus for searching downlink synchronous code - Google Patents

Abstract

The invention discloses a method and a device for searching a downlink synchronous code. The method comprises: each first SYNC_DL code is subjected to frequency translation to correspondingly obtain each second SYNC_DL code; each second SYNC_DL code is adopted to search and calculate the SYNC_DL code in a baseband signal; and each relevant peak value obtained through calculation is compared so as to obtain the SYNC_DL code corresponding to the largest relevant peak value as a search result. With the method, as the SYNC_DL code is subjected to frequency translation, the SYNC_DL code can be searched near a plurality of frequency points. Even if the frequency deviation of the baseband signal is large, and the frequency deviation value always drops near a certain frequency point in the plurality of the frequency points, thereby the baseband signal is searched. The invention also discloses a device for searching the SYNC_DL code.

Description

Method and device for searching downlink synchronous code

Technical Field

The present invention relates to a signal search technology in a mobile communication system, and in particular, to a method and an apparatus for searching a downlink synchronization code (SYNC _ DL).

Background

Cell search refers to the process by which a User Equipment (UE) must search for a suitable cell and access (often referred to as landing) the cell to use the services provided by the network as soon as possible while the UE is powered on or in a mobile state. SYNC _ DL code for UE to perform cell initial search is set in time division synchronous code division multiple access (TD-SCDMA) system. Since the network side only sends the SYNC _ DL code in the downlink pilot time slot (DwPTS), after the UE determines the SYNC _ DL code in the subframe data through searching, the DwPTS can be determined, and then logging is carried out. Fig. 1 shows the structure of SYNC _ DL code. The length of the SYNC _ DL code is 64 chips (chip) with 4 symbols, and guard slots (GP) are arranged at the front and the back of the SYNC _ DL code. The SYNC _ DL code is preceded by a GP of 48 chips with a length of 3 symbols for trailing protection of a normal slot 0(TS 0); the SYNC _ DL code is followed by a GP of 96 chips of length 6 symbols.

Currently, commonly used search algorithms for searching the SYNC _ DL code include a direct correlation method and a characteristic window method.

The direct correlation method is to perform correlation calculation on a received baseband signal and 32 SYNC _ DL codes in a SYNC _ DL code set, compare the obtained 32 correlation peak values, determine the SYNC _ DL code corresponding to the maximum correlation peak value as the SYNC _ DL code adopted by the current cell, and determine the position of DwPTS according to the position of the maximum correlation peak value.

The characteristic window method is that firstly, the power distribution characteristics of SYNC _ DL codes in a frame structure of a TD-SCDMA system and GP at two sides are utilized, and a power characteristic window is used for determining the position range of the SYNC _ DL codes; and then, carrying out correlation calculation on the data in the position range and 32 SYNC _ DL codes in the SYNC _ DL code set respectively, then comparing the obtained correlation peak values, wherein the SYNC _ DL code corresponding to the maximum correlation peak value is the SYNC _ DL code adopted by the current cell, and determining the position of the DwPTS according to the position of the maximum correlation peak value. Compared with the direct correlation method, the characteristic window method can save the calculation amount.

Because the length of the SYNC _ DL code in the TD-SCDMA system is shorter, only 64 chips exist, which causes that the orthogonality performance between the SYNC _ DL codes is not ideal. When the search algorithm is directly adopted for calculation, in order to obtain an accurate result, the frequency offset of the baseband signal is required to be within a certain range. The frequency offset here refers to a distance of a frequency point of the baseband signal from a frequency point of 0Hz when viewed from the spectrum.

To ensure that the frequency offset of the baseband signal is within a certain range, it is common practice to limit the frequency offset of the local VCO within the range. To ensure that the frequency offset of the VCO is limited within this range, it is often necessary to use an expensive voltage controlled temperature compensated crystal oscillator (VCTCXO). The use of a VCTCXO can significantly increase the manufacturing cost of the UE. Furthermore, the frequency offset of the VCO will increase with the aging time of the VCTCXO, which means that the lifetime of the UE will be limited by the aging time of the device, shortening the lifetime of the UE.

Disclosure of Invention

In view of this, the technical problem solved by the present invention is to provide a method for searching SYNC _ DL code, so as to remove the limitation of the current algorithm on the frequency offset of the baseband signal, thereby achieving that even under a large frequency offset, an accurate calculation result can be obtained by directly adopting the current algorithm, and completing the search of SYNC _ DL code. Furthermore, the frequency offset limitation of the VCO is removed, so that the manufacturing cost of the UE can be effectively reduced, and the service life of the UE can be prolonged.

The invention provides a device for searching SYNC _ DL code.

Therefore, the technical scheme provided by the invention is as follows:

a method of searching for SYNC _ DL codes, the method comprising:

carrying out frequency shifting on each first SYNC _ DL code to obtain corresponding second SYNC _ DL codes;

calculating SYNC _ DL codes in the searched baseband signals by adopting the second SYNC _ DL codes;

and comparing the correlation peak values obtained by calculation to obtain the SYNC _ DL code corresponding to the maximum correlation peak value as a search result.

In some embodiments, the first SYNC _ DL codes are shifted to a plurality of frequency points for covering frequency offset of the baseband signal, respectively.

In some embodiments, each first SYNC _ DL code is shifted to frequency points a × (2 × i-1) and-a × (2 × i-1), respectively;

wherein i represents the forward order of frequency points, i 1

Presentation pair

The operation result of (2) is an upward integer;

y represents the maximum frequency offset value of the baseband signal, and a represents the maximum frequency offset value of the baseband signal that is allowed to obtain an accurate calculation result.

In some embodiments, each first SYNC _ DL code is shifted to frequency points a and-a, respectively;

where a is the maximum frequency offset of the baseband signal that is allowed to obtain an accurate calculation result.

In some embodiments, the baseband signal is simultaneously and respectively searched with the second SYNC _ DL codes of each frequency point.

In some embodiments, the frequency shifting of the first SYNC _ DL code is achieved by frequency shifting each chip of the first SYNC _ DL code.

In some embodiments, the pass operation

<math><mrow> <msubsup> <mi>s</mi> <mrow> <mi>i</mi> <mo>_</mo> <mi>x</mi> </mrow> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msubsup> <mi>s</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mi>i</mi> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> </mrow></math> T_cFor a chip duration, every chip s of the first SYNC _ DL code_i ^(l)Frequency shifting is carried out to obtain the chips s of the corresponding second SYNC _ DL code_{i_x} ^(l)；

Where x denotes a frequency point for moving to, l denotes a number of SYNC _ DL code, and i denotes a chip order.

The invention provides another method for searching SYNC _ DL code, which comprises the following steps:

carrying out frequency shifting on each first SYNC _ DL code to obtain corresponding second SYNC _ DL codes;

calculating SYNC _ DL codes in the searched baseband signals by adopting the first SYNC _ DL codes, comparing the calculated correlation peak values, and determining a first maximum correlation peak value;

calculating SYNC _ DL codes in the searched baseband signals by adopting the second SYNC _ DL codes, comparing the correlation peak values obtained by calculation, and determining a second maximum correlation peak value;

and taking the SYNC _ DL code corresponding to the larger value of the first maximum correlation peak value and the second maximum correlation peak value as the search result.

In some embodiments, the first SYNC _ DL codes are shifted to a plurality of frequency points for covering frequency offset of the baseband signal, respectively.

In some embodiments, each first SYNC _ DL code is shifted to frequency points a × 2 × i and-a × 2 × i, respectively;

wherein i represents the forward order of frequency points, i 1

Presentation pair

The operation result of (2) is an upward integer;

y represents the maximum frequency offset value of the baseband signal, and a represents the maximum frequency offset value of the baseband signal that is allowed to obtain an accurate calculation result.

In some embodiments, each first SYNC _ DL code is shifted to frequency points 2a and-2 a, respectively;

where a is the maximum frequency offset of the baseband signal that is allowed to obtain an accurate calculation result.

Another technical problem to be solved by the present invention is to provide an apparatus for searching for SYNC _ DL code, comprising:

a frequency shifting unit for performing frequency shifting on each first SYNC _ DL code to obtain corresponding second SYNC _ DL codes;

the searching and calculating unit is used for calculating the SYNC _ DL code in the searching baseband signal by adopting each second SYNC _ DL code obtained by the frequency shifting unit; and

and the first search result unit is used for comparing the correlation peak values obtained by the calculation of the search calculation unit to obtain the SYNC _ DL code corresponding to the maximum correlation peak value as a search result.

In some embodiments, the frequency shifting unit shifts each of the first SYNC _ DL codes to a plurality of frequency points for covering frequency offset of the baseband signal, respectively.

In some embodiments, the frequency shifting unit shifts each first SYNC _ DL code to frequency points a × (2 × i-1) and-a × (2 × i-1), respectively;

wherein i represents the forward order of frequency points, i 1

Presentation pair

The operation result of (2) is an upward integer;

y represents the maximum frequency offset value of the baseband signal, and a represents the maximum frequency offset value of the baseband signal that is allowed to obtain an accurate calculation result.

Preferably, the frequency shifting unit shifts each first SYNC _ DL code to frequency points a and-a, respectively;

where a is the maximum frequency offset of the baseband signal that is allowed to obtain an accurate calculation result.

In some embodiments, the search calculation unit performs search calculation on the baseband signal simultaneously and respectively with each second SYNC _ DL code of each frequency point.

In some embodiments, the frequency shifting unit shifts the frequency of the first SYNC _ DL code by frequency shifting each chip of the first SYNC _ DL code.

In some embodiments, the frequency shifting unit operates by

<math><mrow> <msubsup> <mi>s</mi> <mrow> <mi>i</mi> <mo>_</mo> <mi>x</mi> </mrow> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msubsup> <mi>s</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mi>i</mi> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> </mrow></math> T_cFor a chip duration, every chip s of the first SYNC _ DL code is encoded_i ^(l)Frequency shifting is carried out to obtain the chips s of the corresponding second SYNC _ DL code_{i_x} ^(l)；

Where x denotes a frequency point for moving to, l denotes a number of SYNC _ DL code, and i denotes a chip order.

The invention provides another device for searching SYNC _ DL code, which comprises:

a frequency shifting unit for performing frequency shifting on each first SYNC _ DL code to obtain corresponding second SYNC _ DL codes;

the first searching unit is used for calculating SYNC _ DL codes in the searched baseband signals by adopting the first SYNC _ DL codes, comparing the correlation peak values obtained by calculation and determining a first maximum correlation peak value;

the second searching unit is used for calculating SYNC _ DL codes in the searched baseband signals by adopting the second SYNC _ DL codes, comparing the correlation peak values obtained by calculation and determining a second maximum correlation peak value; and

and the second search result unit is used for comparing the first maximum correlation peak value with the second maximum correlation peak value and taking the SYNC _ DL code corresponding to the larger value as the search result.

In some embodiments, the frequency shifting unit shifts each of the first SYNC _ DL codes to a plurality of frequency points for covering frequency offset of the baseband signal, respectively.

In some embodiments, the frequency shifting unit shifts each first SYNC _ DL code to frequency points a × 2 × i and-a × 2 × i, respectively;

wherein i represents the forward order of frequency points, i 1

Presentation pairThe operation result of (2) is an upward integer;

y represents the maximum frequency offset value of the baseband signal, and a represents the maximum frequency offset value of the baseband signal that is allowed to obtain an accurate calculation result.

In some embodiments, the frequency shifting unit shifts each first SYNC _ DL code to frequency points 2a and-2 a, respectively;

where a is the maximum frequency offset of the baseband signal that is allowed to obtain an accurate calculation result.

When the method provided by the invention is adopted, the SYNC _ DL code is subjected to frequency shift, so that the SYNC _ DL code can be searched near a plurality of frequency points. No matter how large the frequency offset of the baseband signal is, the frequency offset value always falls in the vicinity of a certain frequency point among the plurality of frequency points, and is thus searched. It can be seen that the present invention actually expands the spectrum range of searching for SYNC _ DL codes by moving SYNC _ DL codes to multiple frequency points. Accordingly, the frequency offset limitation of the VCO is also removed. Because the frequency offset limitation of the VCO is removed, the expensive VCTCXO can be not used any more, thereby reducing the manufacturing cost of the UE, eliminating the influence of aging of the device and prolonging the service life of the UE.

Drawings

FIG. 1 is a diagram of SYNC _ DL code structure in TD-SCDMA system;

FIG. 2 is a flowchart of an embodiment of a method for searching SYNC _ DL code provided by the present invention;

fig. 3-1 is a diagram of the effective search range of the second SYNC _ DL code on the spectrum;

FIGS. 3-2 and 3-3 are two diagrams illustrating frequency shifting of the first SYNC _ DL code, respectively;

FIG. 4 is a flow chart of another embodiment of a method for searching SYNC _ DL code provided by the present invention;

FIG. 5 is a diagram of an embodiment of an apparatus for searching SYNC _ DL code provided by the present invention;

FIG. 6 is a diagram of another embodiment of an apparatus for searching SYNC _ DL codes according to the present invention;

fig. 7-1 and fig. 7-2 are schematic diagrams of two other apparatuses for searching SYNC _ DL codes according to the present invention.

Detailed Description

The basic concept of the invention is as follows: the SYNC _ DL codes in the SYNC _ DL code set are subjected to frequency shifting in advance so as to expand the search range, and no matter how large the frequency offset of the baseband signal is, the frequency offset value always falls near one of the frequency points so as to be searched.

In order to make those skilled in the art better understand the present invention, the method for searching for SYNC _ DL code provided by the present invention is described in detail below with reference to specific embodiments.

Fig. 2 shows a flow of searching for SYNC _ DL code.

For simplicity, the frequency shifted SYNC _ DL codes are collectively referred to as "second SYNC _ DL codes", and the non-frequency shifted SYNC _ DL codes in the set of SYNC _ DL codes are collectively referred to as "first SYNC _ DL codes".

In step 201, frequency shifting is performed on each first SYNC _ DL code to obtain corresponding second SYNC _ DL codes.

In practical applications, the frequency offset of the baseband signal is also random, and may be positive or negative, under the influence of the frequency offset of the VCO. Therefore, when frequency shifting is performed, both positive and negative shifting is required. The forward direction is a direction larger than 0Hz in a spectrum view; the negative direction means a direction less than 0Hz in the spectrum.

In a preferred embodiment, two frequency points (x, -x) that are opposite to each other are divided into a group of frequency points and then shifted in groups.

When frequency shifting is performed on the SYNC _ DL code, each chip of the SYNC _ DL code may be shifted according to equation (1):

<math><mrow> <msubsup> <mi>s</mi> <mrow> <mi>i</mi> <mo>_</mo> <mi>x</mi> </mrow> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msubsup> <mi>s</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mi>i</mi> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow></math>

wherein s is_i ^(l)Chip, s representing the first SYNC _ DL code_{i_x} ^(l)Chip representing the frequency shifted second SYNC _ DL code; t is_cIn the symbol duration, x represents the shifted frequency point, l represents the number of SYNC _ DL code, and i represents the sequence of symbols in SYNC _ DL code. Currently, there are 32 SYNC _ DL codes in the SYNC _ DL code set, so the value range of l is [1, 32 ]](ii) a SYNC _ DL code consists of 64 chips, so that the value range of i is [0, 63 ]]。

If it is used $\left\{s^{\left(l\right)}\right\}=(s_0^{\left(l\right)},s_1^{\left(l\right)},......,s_{63}^{\left(l\right)})$ Denotes a first SYNC _ DL code, where l 1, 2.

Then, after moving the first SYNC _ DL code to frequency point x, the obtained second SYNC _ DL code can be represented as:

<math><mrow> <mo>{</mo> <msubsup> <mi>s</mi> <mi>x</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>}</mo> <mo>=</mo> <mrow> <mo>(</mo> <msubsup> <mi>s</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>0</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <msubsup> <mi>s</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>1</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msubsup> <mi>s</mi> <mn>63</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>63</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>)</mo> </mrow> </mrow></math>

wherein, l 1, 2.

After moving the first SYNC _ DL code to frequency point-x, the obtained second SYNC _ DL code can be represented as:

<math><mrow> <mo>{</mo> <msubsup> <mi>s</mi> <mrow> <mo>-</mo> <mi>x</mi> </mrow> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>}</mo> <mo>=</mo> <mrow> <mo>(</mo> <msubsup> <mi>s</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>0</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <msubsup> <mi>s</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>1</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msubsup> <mi>s</mi> <mn>63</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>63</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>)</mo> </mrow> </mrow></math>

wherein, l 1, 2.

The effective search range of the second SYNC _ DL code on the frequency spectrum is shown in fig. 3-1, where a represents the maximum frequency offset value of the baseband signal allowed by the search algorithm.

In step 202, the second SYNC _ DL codes are used to calculate the SYNC _ DL codes in the search baseband signal.

In step 202, a direct correlation method, a characteristic window method, or other algorithm for searching the SYNC _ DL code may be used for calculation.

Then, in step 203, the correlation peak values obtained by calculation are compared to determine the maximum correlation peak value.

After the maximum correlation peak is obtained, in step 204, the SYNC _ DL code corresponding to the maximum correlation peak is used as the search result.

Next, a specific application of the present embodiment will be described in further detail.

In a specific application, the frequency spectrum range and the frequency point of the search SYNC _ DL code should be pre-defined according to the maximum frequency offset that may be generated by the baseband signal.

Assuming that the actual maximum frequency offset value of the baseband signal is y; when the search algorithm is directly adopted for calculation, the maximum frequency offset value of the allowed SYNC _ DL code is a.

As can be seen in conjunction with fig. 3-1, to ensure that the search algorithm does not have search blind areas and obtains the maximum search range, frequency points should be set in a × (2 × i-1) and-a × (2 × i-1), where i represents the forward order of the frequency points. When i is 1, the value of the 1 st frequency point should be a; when i is 2, the value of the 2 nd frequency point should be a × 3; and so on. By forward order is meant the order of frequency points in the direction greater than 0Hz, viewed spectrally.

To cover the frequency deviation range [0, y]The value of i should be in the range of [1,

]. Wherein,

presentation pair

The operation result of (2) is an integer.

When y ≦ 35kHz and a ≦ 10kHz, a search should be performed near two frequency points of 10kHz and 30kHz, and correspondingly, search should also be performed near two frequency points of-10 kHz and-30 kHz, as shown in fig. 3-2.

After defining the frequency points, the 32 first SYNC _ DL codes can be moved to each frequency point. The second SYNC _ DL codes shifted to 10kHz, 30kHz, -10kHz and-30 kHz can be respectively expressed as:

<math><mrow> <mo>{</mo> <msubsup> <mi>s</mi> <mrow> <mn>10</mn> <mi>k</mi> </mrow> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>}</mo> <mo>=</mo> <mrow> <mo>(</mo> <msubsup> <mi>s</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>10</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>0</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <msubsup> <mi>s</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>10</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>1</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mo></mo> </mrow> </mrow></math>

<math><mrow> <msubsup> <mi>s</mi> <mn>63</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>10</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>63</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>)</mo> <mo>;</mo> </mrow></math> <math><mrow> <mo>{</mo> <msubsup> <mi>s</mi> <mrow> <mn>30</mn> <mi>k</mi> </mrow> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>}</mo> <mo>=</mo> <mrow> <mo>(</mo> <msubsup> <mi>s</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>30</mn> <mo>&times;</mo> <mn>1</mn> <msup> <mn>0</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>0</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> </mrow> </mrow></math>

<math><mrow> <msubsup> <mi>s</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>30</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>1</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msubsup> <mi>s</mi> <mn>63</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>30</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>63</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>)</mo> <mo>;</mo> </mrow></math>

<math><mrow> <mo>{</mo> <msubsup> <mi>s</mi> <mrow> <mo>-</mo> <mn>10</mn> <mi>k</mi> </mrow> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>}</mo> <mo>=</mo> <mrow> <mo>(</mo> <msubsup> <mi>s</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>10</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>0</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <msubsup> <mi>s</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>10</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>1</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> </mrow> </mrow></math>

<math><mrow> <msubsup> <mi>s</mi> <mn>63</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>10</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>63</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>)</mo> <mo>;</mo> </mrow></math>

<math><mrow> <mo>{</mo> <msubsup> <mi>s</mi> <mrow> <mo>-</mo> <mn>30</mn> <mi>k</mi> </mrow> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>}</mo> <mo>=</mo> <mrow> <mo>(</mo> <msubsup> <mi>s</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>30</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>0</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <msubsup> <mi>s</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>30</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>1</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> </mrow> </mrow></math>

<math><mrow> <msubsup> <mi>s</mi> <mn>63</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mn>30</mn> <mo>&times;</mo> <msup> <mn>10</mn> <mn>3</mn> </msup> <mo>&times;</mo> <mn>63</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>)</mo> <mo>;</mo> </mrow></math>

wherein, l 1, 2.

After receiving the signal sent by the network side, the UE down-converts the received radio frequency signal at the radio frequency part by using the frequency of the VCO to obtain a baseband signal.

The baseband signal is simultaneously and respectively associated with each second SYNC _ DL code of each frequency point, i.e. { s }_10k ^(l)}、{s_30k ^(l)}、{s_-10k ^(l)And { s }_-30k ^(l)Correlation calculation is performed, and the obtained 32 × 4 — 128 correlation peaks are compared to obtain the first maximum correlation peak.

The baseband signal is simultaneously and respectively correlated with the second SYNC _ DL codes of each frequency point, and the method has the advantages of realizing parallel processing of data and effectively shortening the searching time.

It can be seen that, in the above embodiment, since the SYNC _ DL code is shifted to a plurality of frequency points, the SYNC _ DL code can be searched in the vicinity of the plurality of frequency points. No matter how large the frequency offset of the baseband signal is, the frequency offset value always falls in the vicinity of a certain frequency point among the plurality of frequency points, and is thus searched. It can be seen that moving the SYNC _ DL code to multiple frequency points actually expands the spectrum range of the search SYNC _ DL code. Accordingly, the frequency offset limitation of the VCO is also removed. Because the frequency offset limitation of the VCO is removed, the expensive VCTCXO can be not used any more, thereby reducing the manufacturing cost of the UE, eliminating the influence of aging of the device and prolonging the service life of the UE.

As can be seen from the above description of the embodiment, the first SYNC _ DL code can be regarded as a special second SYNC _ DL code, i.e., a second SYNC _ DL code obtained by shifting the first SYNC _ DL code to a frequency point of 0 Hz. Based on this, the present invention provides another method for searching for SYNC _ DL code, and the flow of the method is shown in fig. 4.

In step 401, each first SYNC _ DL code is frequency shifted to obtain a corresponding second SYNC _ DL code.

When frequency shifting is performed on the SYNC _ DL code, each chip of the SYNC _ DL code may be shifted as in equation (1).

In step 402, each first SYNC _ DL code is used to perform calculation for searching for SYNC _ DL codes in the baseband signal, and each correlation peak value obtained by calculation is compared to determine a first maximum correlation peak value.

The calculation may be performed by using a direct correlation method, a characteristic window method, or another algorithm for searching the SYNC _ DL code.

While step 402 is executed, in step 403, the second SYNC _ DL codes are used to perform calculation of the SYNC _ DL codes in the search baseband signal, and the correlation peak values obtained by calculation are compared to determine a second maximum correlation peak value.

The execution procedure of step 403 is the same as that of steps 202 and 203 in the previous embodiment, and the description is not repeated here.

After the first maximum correlation peak and the second maximum correlation peak are obtained, in step 404, the first maximum correlation peak and the second maximum correlation peak are compared to determine the larger value thereof.

In step 405, the SYNC _ DL code corresponding to the larger value is used as the search result.

Next, a specific application of the present embodiment will be described in further detail.

In a specific application, the frequency spectrum range and the frequency point of the search SYNC _ DL code should be pre-defined according to the maximum frequency offset that may be generated by the baseband signal.

Assuming that the actual maximum frequency offset value of the baseband signal is y; when the search algorithm is directly adopted for calculation, the maximum frequency offset value of the allowed baseband signal is a.

For searching using the first SYNC _ DL code, it can be seen from fig. 3-1 that, in order to ensure that the search algorithm does not have a search blind area and obtain the maximum search range, frequency points should be set at a × 2 × i and-a × 2 × i, where i represents the forward order of the frequency points. When i is 1, the value of the 1 st frequency point should be a × 2, and the corresponding negative frequency point is — a × 2; when i is 2, the value of the 2 nd frequency point should be a × 4, and the corresponding negative frequency point is — a × 4; and so on.

To cover the frequency deviation range [0, y]The value of i should be in the range of [1,]. Wherein,

presentation pair

The operation result of (2) is an integer.

When y ≦ 35kHz and a ≦ 10kHz, a search should be performed near two frequency points of 20kHz and 40kHz, and correspondingly, search should also be performed near two frequency points of-20 kHz and-40 kHz, as shown in fig. 3-3.

After defining the frequency points, the 32 first SYNC _ DL codes can be moved to each frequency point. The subsequent processing is the same as that in the previous embodiment, and is not described in detail.

In practical applications, the frequency offset of the VCO is usually less than 20kHz, so to cover the frequency offset range [0, y ], i is usually 1. That is, in general, the frequency offset range of the VCO can be covered by moving the first SYNC _ DL code to a and-a, or 2a and-2 a, respectively.

Based on the method described in the above embodiment, the present invention further provides a device for searching for SYNC _ DL codes.

The apparatus, as shown in fig. 5, includes a frequency moving unit S51, a search calculating unit S52, and a first search result unit S53.

The frequency shifting unit S51 is configured to perform frequency shifting on each first SYNC _ DL code to obtain each corresponding second SYNC _ DL code.

In practical applications, the frequency offset of the baseband signal is also random, and may be positive or negative, under the influence of the frequency offset of the VCO. Therefore, when frequency shifting is performed, both positive and negative shifting is required. In a preferred embodiment, two frequency points (x, -x) that are opposite to each other are divided into a group of frequency points and then shifted in groups. When frequency shifting is performed on the SYNC _ DL code, each chip of the SYNC _ DL code may be shifted as in equation (1).

If it is used $\left\{s^{\left(l\right)}\right\}=(s_0^{\left(l\right)},s_1^{\left(l\right)},......,s_{63}^{\left(l\right)})$ Denotes a first SYNC _ DL code, where l ═ is1，2，......，32。

Then, after moving the first SYNC _ DL code to frequency point x, the obtained second SYNC _ DL code can be represented as:

<math><mrow> <mo>{</mo> <msubsup> <mi>s</mi> <mi>x</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>}</mo> <mo>=</mo> <mrow> <mo>(</mo> <msubsup> <mi>s</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>0</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <msubsup> <mi>s</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>1</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msubsup> <mi>s</mi> <mn>63</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>63</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>)</mo> </mrow> </mrow></math>

wherein, l 1, 2.

After moving the first SYNC _ DL code to frequency point-x, the obtained second SYNC _ DL code can be represented as:

<math><mrow> <mo>{</mo> <msubsup> <mi>s</mi> <mrow> <mo>-</mo> <mi>x</mi> </mrow> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>}</mo> <mo>=</mo> <mrow> <mo>(</mo> <msubsup> <mi>s</mi> <mn>0</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>0</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <msubsup> <mi>s</mi> <mn>1</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>1</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msubsup> <mi>s</mi> <mn>63</mn> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>&times;</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mn>2</mn> <mi>&pi;</mi> <mo>&times;</mo> <mi>x</mi> <mo>&times;</mo> <mn>63</mn> <mo>&times;</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> </mrow> </msup> <mo>)</mo> </mrow> </mrow></math>

wherein, l 1, 2.

The effective search range of the second SYNC _ DL code on the frequency spectrum is shown in fig. 3-1, where a represents the maximum frequency offset value of the baseband signal allowed by the search algorithm.

The search calculation unit S52 is configured to perform calculation for searching for the SYNC _ DL code in the baseband signal by using each second SYNC _ DL code obtained by the frequency shifting unit S51.

The search calculation unit S52 may perform calculation using a direct correlation method, a characteristic window method, or another algorithm for searching for the SYNC _ DL code.

The first search result unit S53 is configured to compare the correlation peak values obtained by the search calculation unit S52, and use the SYNC _ DL code corresponding to the obtained maximum correlation peak value as the search result.

The specific application of the device shown in fig. 5 will now be described in further detail.

In a specific application, the frequency spectrum range and the frequency point of the search SYNC _ DL code should be pre-defined according to the maximum frequency offset that may be generated by the baseband signal.

Assuming that the actual maximum frequency offset value of the baseband signal is y, when the search algorithm is directly adopted for calculation, the allowed maximum frequency offset value of the baseband signal is a.

As can be seen in conjunction with fig. 3-1, to ensure that the search algorithm does not have search blind areas and obtains the maximum search range, frequency points should be set in a × (2 × i-1) and-a × (2 × i-1), where i represents the forward order of the frequency points. When i is 1, the value of the 1 st frequency point should be a; when i is 2, the value of the 2 nd frequency point should be a × 3; and so on. By forward order is meant the order of frequency points in the direction greater than 0Hz, viewed spectrally.

To cover the frequency deviation range [0, y]The value of i should be in the range of [1,

]. Wherein,

presentation pair

The operation result of (2) is an integer.

When y is less than or equal to 20kHz and a is 10kHz, i is 1, i should be searched near the frequency point of 10kHz, and correspondingly, should also be searched near the frequency point of-10 kHz.

After the frequency points are defined, the 32 first SYNC _ DL codes can be moved to 10kHz and-10 kHz respectively.

After receiving the signal sent by the network side, the UE down-converts the received radio frequency signal at the radio frequency part by using the frequency of the VCO to obtain a baseband signal.

The search calculation unit S52 combines the baseband signal with the second SYNC _ DL codes of each frequency point, i.e., { S }, respectively_10k ^(l)And { s }_-10k ^(l)Performing correlation calculation on the obtainedThe 32 x 2-64 correlation peaks are compared to determine the maximum correlation peak. In this case, the apparatus shown in fig. 5 can be equivalently transformed into the apparatus shown in fig. 7-1. It can be seen that in the apparatus shown in FIG. 7-1, the forward frequency shifting unit S71 is used for shifting SYNC _ DL code to frequency point 10kHz to obtain each second SYNC _ DL code, i.e., { S }_10k ^(l)}. The forward search calculation unit S72 is used to compare the baseband signal with each second SYNC _ DL code with frequency point of 10kHz, i.e. { S }_10k ^(l)And performing correlation calculation to obtain 32 correlation peak values. The negative frequency shifting unit S73 is used to shift SYNC _ DL code to frequency point-10 kHz to obtain each second SYNC _ DL code, i.e., { S }_-10k ^(l)}. The negative search calculation unit S74 is used to compare the baseband signal with the second SYNC _ DL codes with the frequency point of-10 kHz, i.e. { S }_-10k ^(l)And performing correlation calculation to obtain 32 correlation peak values.

The baseband signal is simultaneously and respectively correlated with the second SYNC _ DL codes of each frequency point, and the method has the advantages of realizing parallel processing of data and effectively shortening the searching time.

It can be seen that in the apparatus shown in fig. 5, since the SYNC _ DL code is shifted to a plurality of frequency points, the SYNC _ DL code can be searched in the vicinity of the plurality of frequency points. No matter how large the frequency offset of the baseband signal is, the frequency offset value always falls in the vicinity of a certain frequency point among the plurality of frequency points, and is thus searched.

It can be seen that the first SYNC _ DL code can be regarded as a special second SYNC _ DL code, i.e. the second SYNC _ DL code obtained by shifting the first SYNC _ DL code to a frequency point of 0 Hz. Based on this, the present invention provides another apparatus for searching SYNC _ DL code.

As shown in fig. 6. The apparatus includes a frequency shift unit S51, a first search unit S61, a second search unit S62, and a second search result unit S63.

The frequency shifting unit S51 is configured to perform frequency shifting on each first SYNC _ DL code to obtain each corresponding second SYNC _ DL code.

The first searching unit S61 is configured to perform calculation for searching for the SYNC _ DL code in the baseband signal by using each first SYNC _ DL code, compare each correlation peak obtained by the calculation, and determine a first maximum correlation peak. The second searching unit S62 is configured to perform calculation for searching for the SYNC _ DL code in the baseband signal by using each second SYNC _ DL code, compare each correlation peak obtained by the calculation, and determine a second maximum correlation peak. The second search result unit S63 is configured to compare the first maximum correlation peak value with the second maximum correlation peak value, and use the SYNC _ DL code corresponding to the larger one of the first maximum correlation peak value and the second maximum correlation peak value as the search result.

The specific application of the device shown in fig. 6 will now be described in further detail.

In a specific application, the frequency spectrum range and the frequency point of the search SYNC _ DL code should be pre-defined according to the maximum frequency offset that may be generated by the baseband signal.

Assuming that the actual maximum frequency offset value of the baseband signal is y, when the search algorithm is directly adopted for calculation, the allowed maximum frequency offset value of the baseband signal is a.

For searching using the first SYNC _ DL code, it can be seen from fig. 3-1 that, in order to ensure that the search algorithm does not have a search blind area and obtain the maximum search range, frequency points should be set at a × 2 × i and-a × 2 × i, where i represents the forward order of the frequency points. When i is 1, the value of the 1 st frequency point should be a × 2, and the corresponding negative frequency point is — a × 2; when i is 2, the value of the 2 nd frequency point should be a × 4, and the corresponding negative frequency point is — a × 4; and so on.

To cover the frequency deviation range [0, y]The value of i should be in the range of [1,

]. Wherein,

presentation pairThe operation result of (2) is an integer.

When y is less than or equal to 30kHz and a is 10kHz, i is 1, i is to cover the frequency offset range [0, 30kHz ], i is to search near the frequency point of 20kHz, and correspondingly, search is to be performed near the frequency point of-20 kHz.

After the frequency points are defined, the 32 first SYNC _ DL codes can be moved to 20kHz and-20 kHz respectively.

After receiving the signal sent by the network side, the UE down-converts the received radio frequency signal at the radio frequency part by using the frequency of the VCO to obtain a baseband signal.

The first search calculation unit S61 combines the baseband signal with the first SYNC _ DL codes, i.e. { S } at the same time^(l)And performing correlation calculation, and comparing the obtained 32 correlation peak values to determine a first maximum correlation peak value.

The second search calculation unit S52 combines the baseband signal with the second SYNC _ DL codes of each frequency point, i.e., { S }_20k ^(l)And { s }_-20k ^(l)And performing correlation calculation, and comparing the obtained 64 correlation peak values to determine a second maximum correlation peak value. In this case, the apparatus shown in fig. 6 can be equivalently transformed into the apparatus shown in fig. 7-2. It can be seen that in the apparatus shown in FIG. 7-2, the forward frequency shifting unit S71 is used for shifting SYNC _ DL code to frequency point 10kHz to obtain each second SYNC _ DL code, i.e., { S }_10k ^(l)}. The forward search calculation unit S72 is used to compare the baseband signal with each second SYNC _ DL code with frequency point of 10kHz, i.e. { S }_10k ^(l)And performing correlation calculation to obtain 32 correlation peak values. The negative frequency shifting unit S73 is used to shift SYNC _ DL code to frequency point-10 kHz to obtain each second SYNC _ DL code, i.e., { S }_-10k ^(l)}. The negative search calculation unit S74 is used to compare the baseband signal with the second SYNC _ DL codes with the frequency point of-10 kHz, i.e. { S }_-10k ^(l)And performing correlation calculation to obtain 32 correlation peak values. Ratio ofThe comparing unit S75 is configured to compare the 64 correlation peak values obtained by the positive search computing unit S72 and the negative search computing unit S74, and determine the maximum correlation peak value.

In practical applications, the frequency offset of the VCO is usually less than 20kHz, so to cover the frequency offset range [0, y ], i is usually 1. That is, in general, the frequency offset range of the VCO can be covered by moving the first SYNC _ DL code to a and-a, or 2a and-2 a, respectively.

It can be seen by those skilled in the art that all the embodiments provided above are not limited to TD-SCDMA systems, but can also be used for SYNC _ DL search in FDD systems and other similar systems.

Those of skill in the art will understand that the various exemplary method steps and apparatus elements described in connection with the embodiments disclosed herein can be implemented as electronic hardware, software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative steps and elements have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative elements described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method described in connection with the embodiments disclosed above may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a subscriber station. In the alternative, the processor and the storage medium may reside as discrete components in a subscriber station.

The disclosed embodiments are provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope or spirit of the invention. The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A method for searching downlink synchronization codes, comprising:

performing frequency shifting on each first downlink synchronization (SYNC _ DL) code to obtain corresponding second downlink synchronization (SYNC _ DL) codes; the frequency shifting of each first downlink synchronization (SYNC _ DL) code is to shift the frequency of the first SYNC _ DL code by shifting the frequency of each chip of the first SYNC _ DL code, wherein each first SYNC _ DL code is shifted to frequency points a × (2 × i-1) and-a × (2 × i-1), respectively, where i represents the forward order of the frequency points,

presentation pair

The operation result of (a) is an integer, y represents the maximum frequency offset value of the baseband signal, and a represents the maximum frequency offset value of the baseband signal allowed by obtaining an accurate calculation result;

calculating SYNC _ DL codes in the searched baseband signals by adopting the second SYNC _ DL codes;

and comparing the correlation peak values obtained by calculation to obtain the SYNC _ DL code corresponding to the maximum correlation peak value as a search result.

2. The method as claimed in claim 1, wherein the baseband signal is simultaneously searched and calculated with the second SYNC _ DL codes of each frequency point.

3. The method of claim 1, operated on by

T_cFor chip duration, every chip of the first SYNC _ DL code

Frequency shifting is carried out to obtain the corresponding chip of the second SYNC _ DL code

Where x denotes a frequency point for moving to, l denotes a number of SYNC _ DL code, and i denotes a chip order.

4. A method for searching downlink synchronization codes, comprising:

performing frequency shifting on each first downlink synchronization (SYNC _ DL) code to obtain corresponding second downlink synchronization (SYNC _ DL) codes; each chip of the first SYNC _ DL codes is shifted to frequency points a × 2 × i and-a × 2 × i, respectively, where i denotes a forward order of frequency points,

presentation pair

The operation result of (a) is an integer, y represents the maximum frequency offset value of the baseband signal, and a represents the maximum frequency offset value of the baseband signal allowed by obtaining an accurate calculation result;

calculating SYNC _ DL codes in the searched baseband signals by adopting the first downlink synchronous (SYNC _ DL) codes, comparing the calculated correlation peak values, and determining a first maximum correlation peak value;

calculating SYNC _ DL codes in the searched baseband signals by adopting the second downlink synchronous (SYNC _ DL) codes, comparing the calculated correlation peak values, and determining a second maximum correlation peak value;

and taking the SYNC _ DL code corresponding to the larger value of the first maximum correlation peak value and the second maximum correlation peak value as the search result.

5. An apparatus for searching downlink synchronization codes, comprising:

a frequency shifting unit, configured to perform frequency shifting on each first downlink synchronization (SYNC _ DL) code to obtain each corresponding second downlink synchronization (SYNC _ DL) code; the frequency shifting unit shifts the frequency of each chip of the first SYNC _ DL code to realize the frequency shifting of the first SYNC _ DL code, and the frequency shifting unit shifts each first SYNC _ DL code to a frequency point respectivelya × (2 × i-1) and-a × (2 × i-1), where i represents the forward order of frequency bins,

presentation pair

The operation result of (a) is an integer, y represents the maximum frequency offset value of the baseband signal, and a represents the maximum frequency offset value of the baseband signal allowed by obtaining an accurate calculation result;

the searching and calculating unit is used for calculating the SYNC _ DL code in the searching baseband signal by adopting each second downlink synchronous (SYNC _ DL) code obtained by the frequency shifting unit; and

and the first search result unit is used for comparing the correlation peak values obtained by the calculation of the search calculation unit to obtain the SYNC _ DL code corresponding to the maximum correlation peak value as a search result.

6. The apparatus as claimed in claim 5, wherein the searching unit performs the searching calculation on the baseband signal simultaneously with the second SYNC _ DL codes of each frequency point.

7. The apparatus of claim 5, wherein the frequency shifting unit operates by

T_cFor chip duration, every chip of the first SYNC _ DL code

Frequency shifting is carried out to obtain the corresponding chip of the second SYNC _ DL code

Where x denotes a frequency point for moving to, l denotes a number of SYNC _ DL code, and i denotes a chip order.

8. An apparatus for searching downlink synchronization codes, comprising:

a frequency shifting unit, configured to perform frequency shifting on each first downlink synchronization (SYNC _ DL) code to obtain each corresponding second downlink synchronization (SYNC _ DL) code; the frequency shifting unit shifts each chip of each first SYNC _ DL code to frequency points a x 2 x i and-a x 2 x i, respectively, wherein i represents the forward order of the frequency points, presentation pair

The operation result of (a) is an integer, y represents the maximum frequency offset value of the baseband signal, and a represents the maximum frequency offset value of the baseband signal allowed by obtaining an accurate calculation result;

the first searching unit is used for calculating SYNC _ DL codes in the searching baseband signal by adopting the first downlink synchronous (SYNC _ DL) codes, comparing each correlation peak value obtained by calculation and determining a first maximum correlation peak value;

the second searching unit is used for calculating SYNC _ DL codes in the searching baseband signal by adopting the second downlink synchronous (SYNC _ DL) codes, comparing each correlation peak value obtained by calculation and determining a second maximum correlation peak value; and

and the second search result unit is used for comparing the first maximum correlation peak value with the second maximum correlation peak value and taking the SYNC _ DL code corresponding to the larger value as the search result.

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