Frame synchronization method and apparatus

• US 10,523,487 B2
• Filed: 11/02/2016
• Issued: 12/31/2019
• Est. Priority Date: 05/04/2014
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Huang, Huang, Yan, Xi, Li, Sainan
• Primary Examiner(s): George, Ayanah S
• Application Number:
  US15/341,543
• Publication Number:
  US 20170048093A1
• Time in Patent Office: 1,154 Days
• CPC Class Codes: H04L 27/26 Systems using multi-frequency codes H04L27/32 takes precedence
• CPC Class Codes: H04L 27/2656 Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols
• CPC Class Codes: H04L 7/0016 correction of synchronization errors
• CPC Class Codes: H04W 56/004 compensating for timing error of reception due to propagation delay

Abstract

Embodiments of the present invention provide a frame synchronization method and apparatus, which can reduce impact of a carrier frequency offset. In those embodiment, a solution is provided and the solution includes: obtaining a received signal of a receiving antenna; calculating an auto-correlation value of the received signal and determining a time corresponding to the auto-correlation value that is of the received signal and that meets a first preset condition, as an initial estimation time; obtaining a carrier frequency offset estimation value according to the initial estimation time, the received signal, and a frequency offset estimation algorithm, and performing frequency offset compensation on the received signal by using the carrier frequency offset estimation value; calculating a cross-correlation value and an auto-correlation value of the received signal on which the frequency offset compensation has been performed. The embodiments of the present invention are used for frame synchronization.

Claims

1. A frame synchronization method, comprising:

obtaining a received signal of a receiving antenna;

obtaining an auto-correlation value of the received signal according to the received signal and an auto-correlation algorithm;

determining a time corresponding to the auto-correlation value that is of the received signal and that meets a first preset condition, as an initial estimation time;

obtaining a carrier frequency offset estimation value according to the initial estimation time, the received signal, and a frequency offset estimation algorithm, and performing frequency offset compensation on the received signal by using the carrier frequency offset estimation value;

obtaining, according to the received signal on which the frequency offset compensation has been performed, a preamble signal that is sent by a transmitting antenna and that meets a second preset condition, using a cross-correlation algorithm, and the auto-correlation algorithm, to computer a cross-correlation value and an auto-correlation value of the received signal on which the frequency offset compensation has been performed; and

determining a time corresponding to the cross-correlation value and the auto-correlation value that are of the received signal on which the frequency offset compensation has been performed and that meet a third preset condition, as a frame synchronization time, and demodulating data according to the frame synchronization time to complete frame synchronization;

wherein the second preset condition comprises;

2. The method according to claim 1, wherein the obtaining the auto-correlation value of the received signal according to the received signal and an auto-correlation algorithm comprises:

calculating the auto-correlation value of the received signal according to a first auto-correlation value formula, wherein the first auto-correlation value formula comprises;

3. The method according to claim 1, wherein the determining the time corresponding to the auto-correlation value that is of the received signal and that meets a first preset condition, as an initial estimation time comprises:

comparing the auto-correlation value of the received signal with a first preset threshold; and

if the auto-correlation value of the received signal is greater than or equal to the first preset threshold, determining the time corresponding to the auto-correlation value of the received signal as the initial estimation time.

4. The method according to claim 1, wherein the obtaining the carrier frequency offset estimation value according to the initial estimation time, the received signal, and a frequency offset estimation algorithm, and performing frequency offset compensation on the received signal by using the carrier frequency offset estimation value comprises:

calculating the carrier frequency offset estimation value according to a frequency offset estimation formula, wherein the frequency offset estimation formula comprises;

5. The method according to claim 1, wherein the obtaining, according to the received signal on which the frequency offset compensation has been performed, the preamble signal that is sent by a transmitting antenna and that meets a second preset condition, a cross-correlation algorithm, and the auto-correlation algorithm, the cross-correlation value and the auto-correlation value of the received signal on which the frequency offset compensation has been performed comprises:

calculating, according to a cross-correlation value formula, the cross-correlation value of the received signal on which the frequency offset compensation has been performed, wherein the cross-correlation value formula comprises;

6. The method according to claim 1, wherein the determining the time corresponding to the cross-correlation value and the auto-correlation value that are of the received signal on which the frequency offset compensation has been performed and that meet a third preset condition, as a frame synchronization time comprises:

comparing the cross-correlation value of the received signal on which the frequency offset compensation has been performed with a second preset threshold, and comparing the auto-correlation value of the received signal on which the frequency offset compensation has been performed with a third preset threshold; and

if the cross-correlation value of the received signal on which the frequency offset compensation has been performed is greater than or equal to the second preset threshold and the auto-correlation value of the received signal on which the frequency offset compensation has been performed is greater than or equal to the third preset threshold, determining the time corresponding to the cross-correlation value and the auto-correlation value of the received signal on which the frequency offset compensation has been performed, as the frame synchronization time, and demodulating the data according to the frame synchronization time to complete frame synchronization.

7. The method according to claim 6, wherein the second preset threshold comprises:

a value obtained by multiplying, by a preset coefficient, a maximum value of L continuous cross-correlation values of the received signal on which the frequency offset compensation has been performed, wherein L is the length of the preamble signal.

8. A frame synchronization apparatus, wherein the apparatus comprises:

a communications interface, a memory, and a processor, wherein the communications interface is configured to communicate with a network element;

the memory is configured to store computer code; and

the processor is configured to execute the computer code to;

obtain a received signal of a receiving antenna;

obtain an auto-correlation value of the received signal according to the received signal and an auto-correlation algorithm;

determine a time corresponding to the auto-correlation value that is of the received signal and that meets a first preset condition, as an initial estimation time;

obtain a carrier frequency offset estimation value according to the initial estimation time, the received signal, and a frequency offset estimation algorithm, and perform frequency offset compensation on the received signal by using the carrier frequency offset estimation value. obtain, according to the received signal on which the frequency offset compensation has been performed, a preamble signal that is sent by a transmitting antenna and that meets a second preset condition, using a cross-correlation algorithm, and the auto-correlation algorithm, to computer a cross-correlation value and an auto-correlation value of the received signal on which the frequency offset compensation has been performed; and

determine a time corresponding to the cross-correlation value and the auto-correlation value that are of the received signal on which the frequency offset compensation has been performed and that meet a third preset condition, as a frame synchronization time, and demodulate data according to the frame synchronization time to complete frame synchronization;

wherein the second preset condition comprises;

9. The apparatus according to claim 8, wherein the processor is further configured to execute the computer code to:

calculate the auto-correlation value of the received signal according to a first auto-correlation value formula, wherein the first auto-correlation value formula comprises;

10. The apparatus according to claim 8, wherein the processor is further configured to execute the computer code to:

compare the auto-correlation value of the received signal with a first preset threshold; and

if the auto-correlation value of the received signal is greater than or equal to the first preset threshold, determine the time corresponding to the auto-correlation value of the received signal as the initial estimation time.

11. The apparatus according to claim 8, wherein the processor is further configured to execute the computer code to:

calculate the carrier frequency offset estimation value according to a frequency offset estimation formula, wherein the frequency offset estimation formula comprises;

12. The apparatus according to claim 8, wherein the processor is further configured to execute the computer code to:

calculate, according to a cross-correlation value formula, the cross-correlation value of the received signal on which the frequency offset compensation has been performed, wherein the cross-correlation value formula comprises;

13. The apparatus according to claim 8, wherein the processor is further configured to execute the computer code to:

compare the cross-correlation value of the received signal on which the frequency offset compensation has been performed with a second preset threshold, and compare the auto-correlation value of the received signal on which the frequency offset compensation has been performed with a third preset threshold; and

if the cross-correlation value of the received signal on which the frequency offset compensation has been performed is greater than or equal to the second preset threshold and the auto-correlation value of the received signal on which the frequency offset compensation has been performed is greater than or equal to the third preset threshold, determine the time corresponding to the cross-correlation value and the auto-correlation value of the received signal on which the frequency offset compensation has been performed, as the frame synchronization time, and demodulate the data according to the frame synchronization time to complete frame synchronization.

14. The apparatus according to claim 13, wherein the second preset threshold comprises:

a value obtained by multiplying, by a preset coefficient, a maximum value of L continuous cross-correlation values of the received signal on which the frequency offset compensation has been performed, wherein L is the length of the preamble signal.