Time synchronization method, apparatus, and system

Abstract

In various embodiments, a method is provided. In this method, a first signal is received from a master node, and is sampled to obtain a first sample. The first sample is then quantized to obtain a quantized form of the first sample. A first synchronization sequence is detected from the quantized form of the first sample at T2. First information is received from the master node and the first information is used to indicate a moment T1 at which the master node sends the first synchronization sequence. A second synchronization sequence is sent to the master node at T3. Second information received from the master node and the second information is used to indicate a moment T4 at which the master node detects a quantized form of the second synchronization sequence. Time synchronization is performed based on T1, T2, T3, and T4.

What is claimed is: 
     
         1 . A time synchronization method, comprising:
 receiving, by a slave node, a first signal from a master node, wherein the first signal comprises a first synchronization sequence;   detecting, by the slave node, the first synchronization sequence from the first signal, wherein a moment of detecting the first synchronization sequence is T2;   receiving, by the slave node, first information from the master node, wherein the first information indicates a moment T1 at which the master node sends the first synchronization sequence;   sending, by the slave node, a second synchronization sequence to the master node, wherein a moment of sending the second synchronization sequence is T3, and the second synchronization sequence is inserted at the channel layer of the slave node;   receiving, by the slave node, second information from the master node, wherein the second information indicates a moment T4 at which the master node detects a quantized form of the second synchronization sequence; and   performing, by the slave node, time synchronization between the slave node and the master node based on T1, T2, T3, and T4.   
     
     
         2 . The method according to  claim 1 , wherein the detecting, by the slave node, of the first synchronization sequence from the first signal comprises:
 sampling, by the slave node, the first signal to obtain a first sample;   quantizing, by the slave node, the first sample to obtain a quantized form of the first sample; and   detecting, by the slave node, the first synchronization sequence from the quantized form of the first sample.   
     
     
         3 . The method according to  claim 2 , wherein detecting, by the slave node, of the first synchronization sequence from the quantized form of the first sample comprises:
 performing, by the slave node, correlation peak detection of the first synchronization sequence on the quantized form of the first sample.   
     
     
         4 . The method according to  claim 2 , wherein the first signal further comprises a third synchronization sequence used for group synchronization, and a first offset exists between a first element of the third synchronization sequence and a first element of the first synchronization sequence; and
 detecting, by the slave node, of the first synchronization sequence from the quantized form of the first sample comprises:   determining, by the slave node, a first location, wherein the first location is a location of the first element of the third synchronization sequence in the quantized form of the first sample;   determining, by the slave node, a second location based on the first location and the first offset, wherein the second location is a location of the first element of the first synchronization sequence in the quantized form of the first sample;   obtaining, by the slave node, a quantized form of a second sample based on the second location, wherein the first sample comprises the second sample; and   detecting, by the slave node, the first synchronization sequence from the quantized form of the second sample.   
     
     
         5 . The method according to  claim 4 , wherein the determining, by the slave node, of the first location comprises:
 performing, by the slave node, correlation peak detection of the third synchronization sequence on the quantized form of the first sample to determine the first location; and   detecting, by the slave node, the first synchronization sequence from the quantized form of the second sample comprises: performing, by the slave node, correlation peak detection of the first synchronization sequence on the quantized form of the second sample.   
     
     
         6 . The method according to  claim 1 , wherein the sending, by the slave node, of the second synchronization sequence to the master node comprises:
 generating, by the slave node, an encoded codeword;   inserting, by the slave node, the second synchronization sequence into the encoded codeword;   processing, by the slave node, the encoded codeword into which the second synchronization sequence is inserted, to generate a second signal; and   sending, by the slave node, the second signal to the master node.   
     
     
         7 . The method according to  claim 6 , further comprising:
 inserting, by the slave node into the encoded codeword, a fourth synchronization sequence used for group synchronization, wherein a second offset exists between a first element of the fourth synchronization sequence and a first element of the second synchronization sequence.   
     
     
         8 . A time synchronization method, comprising:
 sending, by a master node, a first signal to a slave node, wherein the first signal comprises a first synchronization sequence, and the first synchronization sequence is inserted at a channel layer of the master node;   sending, by the master node, first information to the slave node, wherein the first information indicates a moment T1 at which the master node sends the first synchronization sequence;   receiving, by the master node, a second signal from the slave node, wherein the second signal comprises a second synchronization sequence;   detecting, by the master node, the second synchronization sequence from the second signal, wherein a moment of detecting the second synchronization sequence is T4; and   sending, by the master node, second information to the slave node, wherein the second information indicates T4, and T1 and T4 are used for time synchronization between the master node and the slave node.   
     
     
         9 . The method according to  claim 8 , wherein the detecting, by the master node, of the second synchronization sequence from the second signal comprises:
 sampling, by the master node, the second signal to obtain a third sample;   quantizing, by the master node, the third sample to obtain a quantized form of the third sample; and   detecting, by the master node, the second synchronization sequence from the quantized form of the third sample.   
     
     
         10 . The method according to  claim 9 , wherein detecting, by the master node, of the second synchronization sequence from the quantized form of the third sample comprises:
 performing, by the master node, correlation peak detection of the second synchronization sequence on the quantized form of the third sample.   
     
     
         11 . The method according to  claim 9 , wherein the second signal further comprises a fourth synchronization sequence used for group synchronization, and a second offset exists between a first element of the fourth synchronization sequence and a first element of the second synchronization sequence; and
 detecting, by the master node, of the second synchronization sequence from the quantized form of the third sample comprises:   determining, by the master node, a third location, wherein the third location is a location of the first element of the fourth synchronization sequence in the quantized form of the third sample;   determining, by the master node, a fourth location based on the third location and the second offset, wherein the fourth location is a location of the first element of the second synchronization sequence in the quantized form of the third sample;   obtaining, by the master node, a quantized form of a fourth sample based on the fourth location, wherein the third sample comprises the fourth sample; and   detecting, by the master node, the second synchronization sequence from the quantized form of the fourth sample.   
     
     
         12 . The method according to  claim 11 , wherein the determining, by the master node, of the third location comprises:
 performing, by the master node, correlation peak detection of the fourth synchronization sequence on the quantized form of the third sample to determine the third location; and   detecting, by the master node, of the second synchronization sequence from the quantized form of the fourth sample comprises: performing, by the master node, correlation peak detection of the second synchronization sequence on the quantized form of the fourth sample.   
     
     
         13 . The method according to  claim 8 , wherein the sending, by a master node, of the first signal to a slave node comprises:
 generating, by the master node, an encoded codeword;   inserting, by the master node, the first synchronization sequence into the encoded codeword;   processing, by the master node, the encoded codeword into which the first synchronization sequence is inserted to generate the first signal; and   sending, by the master node, the first signal to the slave node.   
     
     
         14 . The method according to  claim 13 , further comprising:
 inserting, by the master node into the encoded codeword, a third synchronization sequence used for group synchronization, wherein a first offset exists between a first element of the third synchronization sequence and a first element of the first synchronization sequence.   
     
     
         15 . A node, comprising:
 a memory configured to store a computer program instruction; and   a processor coupled to the memory, wherein the computer program instruction causes the node to be configured to:   receive a first signal from a master node, wherein the first signal comprises a first synchronization sequence;   detect the first synchronization sequence from the first signal, wherein a moment of detecting the first synchronization sequence is T2;   receive first information from the master node, wherein the first information indicates a moment T1 at which the master node sends the first synchronization sequence;   send a second synchronization sequence to the master node, wherein a moment of sending the second synchronization sequence is T3, and the second synchronization sequence is inserted at the channel layer of the slave node; and   receive second information from the master node, wherein the second information is used to indicate a moment T4 at which the master node detects a quantized form of the second synchronization sequence; and   perform time synchronization between the slave node and the master node based on T1, T2, T3, and T4.   
     
     
         16 . The node according to  claim 14 , wherein the computer program instruction further causes the node to be configured to:
 sample the first signal to obtain a first sample;   quantize the first sample to obtain a quantized form of the first sample; and   detect the first synchronization sequence from the quantized form of the first sample.   
     
     
         17 . The node according to  claim 15 , wherein the computer program instruction causes the node to be configured to:
 perform correlation peak detection of the first synchronization sequence on the quantized form of the first sample.   
     
     
         18 . The node according to  claim 16 , wherein the first signal further comprises a third synchronization sequence used for group synchronization, and a first offset exists between a first element of the third synchronization sequence and a first element of the first synchronization sequence; and
 the computer program instruction further causes the node to be configured to:   determine a first location, wherein the first location is a location of the first element of the third synchronization sequence in the quantized form of the first sample;   determine a second location based on the first location and the first offset, wherein the second location is a location of the first element of the first synchronization sequence in the quantized form of the first sample;   obtain a quantized form of a second sample based on the second location, wherein the first sample comprises the second sample; and   detect the first synchronization sequence from the quantized form of the second sample.   
     
     
         19 . The node according to  claim 17 , wherein the computer program instruction causes the node to be configured to:
 perform correlation peak detection of the third synchronization sequence on the quantized form of the first sample to determine the first location; and   perform correlation peak detection of the first synchronization sequence on the quantized form of the second sample.   
     
     
         20 . The node according to  claim 15 , wherein the computer program instruction causes the processor to be configured to:
 generate an encoded codeword;   insert the second synchronization sequence into the encoded codeword;   process the encoded codeword into which the second synchronization sequence is inserted to generate a second signal; and   send, by the slave node, the second signal to the master node.   
     
     
         21 . The node according to  claim 20 , wherein the computer program instruction further causes the processor to be configured to: insert a fourth synchronization sequence used for group synchronization, wherein a second offset exists between a first element of the fourth synchronization sequence and a first element of the second synchronization sequence. 
     
     
         22 . A node, comprising:
 a memory configured to store a computer program instruction; and   a processor coupled to the memory, wherein the computer program instruction causes the node to be configured to:   send a first signal to a slave node, wherein the first signal comprises a first synchronization sequence, and the first synchronization sequence is inserted at a channel layer of the master node;   send first information to the slave node, wherein the first information indicates a moment T1 at which the master node sends the first synchronization sequence;   receive a second signal from the slave node, wherein the second signal comprises a second synchronization sequence;   detect the second synchronization sequence from the second signal, wherein a moment of detecting the second synchronization sequence is T4; and   send second information to the slave node, wherein the second information indicates T4, and T1 and T4 are used for time synchronization between the master node and the slave node.