Cycle-slip detection method and apparatus, and receiver

Patent metadata

Field	Value
Publication number	US-2016134449-A1
Application number	US-201614995855-A
Country	US
Kind code	A1
Filing date	Jan 14, 2016
Priority date	Jul 15, 2013
Publication date	May 12, 2016
Grant date	—

Abstract

The present invention provides a cycle-slip detection method and apparatus, and a receiver. If an absolute value of a first difference obtained by subtracting a phase of a first symbol in a k th training sequence cycle from a phase of a last symbol in a (k−1) th training sequence cycle in a received signal is greater than a cycle-slip determining threshold, it is determined that a cycle-slip occurs in the k th or (k−1) th training sequence cycle. Further, if a second difference obtained by subtracting a phase of the first symbol in the (k+1) th training sequence cycle from a phase of the last symbol in the k th training sequence cycle is greater than the cycle-slip determining threshold, and signs of the first difference and the second difference are opposite, it is determined that a cycle-slip occurs in all symbols in the k th training cycle.

First claim

What is claimed is:

1 . A cycle-slip detection method, comprising:
for a received signal on which phase estimation processing has been performed, calculating a first difference by subtracting a phase of a first symbol in a k th training sequence cycle from a phase of a last symbol in a (k−1) th training sequence cycle in the received signal, and determining whether an absolute value of the first difference is greater than a set cycle-slip determining threshold, wherein the received signal comprises several training sequence cycles, and k is an integer greater than or equal to 2; and if yes, determining that a cycle-slip occurs in the k th or (k−1) th training sequence cycle; calculating a second difference by subtracting a phase of the first symbol in the (k+1) th training sequence cycle from a phase of the last symbol in the k th training sequence cycle; and determining whether an absolute value of the second difference is greater than the set cycle-slip determining threshold, and whether plus and minus signs of the first difference and the second difference are opposite; if yes, determining that a cycle-slip occurs in all symbols in the k th training cycle; or if not, determining that a cycle-slip occurs in a data symbol in the (k−1) th training sequence cycle, and locating a position of the cycle-slip.

2 . The method according to claim 1 , wherein locating a position of the cycle-slip comprises:
performing short-time Fourier transform or N ffi -point fast Fourier transform on a phase estimation sequence corresponding to the (k−1) th training sequence cycle, and using a value of the p th frequency as an output L 1−N of a cycle-slip detection operator corresponding to the (k−1) th training sequence cycle, wherein N is equal to a length of each training sequence cycle; the p th frequency is a low frequency from which a direct current component has been removed; and the phase estimation sequence corresponding to the (k−1) th training sequence cycle comprises phases that correspond to training sequence symbols and data symbols in the (k−1) th training sequence cycle; starting from the first symbol in the (k−1) th training sequence cycle, sequentially comparing a cycle-slip detection operator corresponding to each symbol with a cycle-slip detection operator corresponding to a next symbol, and when it occurs for the first time that a cycle-slip detection operator corresponding to a symbol is less than a cycle-slip detection operator corresponding to a next symbol, recording the cycle-slip detection operator corresponding to the symbol as L idx _ start ; starting from the last symbol in the (k−1) th training sequence cycle, sequentially comparing a cycle-slip detection operator corresponding to each symbol with a cycle-slip detection operator corresponding to a previous symbol, and when it occurs for the first time that a cycle-slip detection operator corresponding to a symbol is less than a cycle-slip detection operator corresponding to a previous symbol, recording the cycle-slip detection operator corresponding to the symbol L idx _ end ; and determining a maximum value L idx between L idx _ start and L idx _ end , and determining that a symbol, corresponding to the maximum value L idx , in the (k−1) th training sequence cycle is the position at which the cycle-slip occurs in the (k−1) th training sequence cycle.

3 . The method according to claim 1 , wherein after determining that a cycle-slip occurs in all symbols in the k th training cycle, the method further comprises :
if the first difference is greater than 0 and the second difference is less than 0, increasing phases corresponding to all the symbols in the k th training sequence cycle by θ; or if the first difference is less than 0 and the second difference is greater than 0, decreasing phases corresponding to all the symbols in the k th training sequence cycle by θ; and wherein θ is a cycle-slip angle corresponding to a modulation mode of the received signal.

4 . The method according to claim 2 , wherein after determining that a symbol, corresponding to the maximum value L idx , in the (k−1) th training sequence cycle is the position at which the cycle-slip occurs in the (k−1) th training sequence cycle, the method further comprises :
comparing a phase value φ k, idx corresponding to the symbol in which the cycle-slip occurs with a phase φ k, idx−1 corresponding to a previous symbol; and
if φ k, idx −φ k, idx− >0, in the (k−1) th training sequence cycle, decreasing phases φ k, idx˜N corresponding to symbols startingl from the symbol in which the cycle-slip occurs to the last symbol by θ; or
if φ k, idx −φ k, idx−1 <0, in the (k−1) th training sequence cycle, increasing phases φ k, idx˜N corresponding to symbols starting from the symbol in which the cycle-slip occurs to the last symbol by θ; and
wherein 0 is a cycle-slip angle corresponding to a modulation mode of the received signal.

5 . The method according to claim 1 , wherein when the received signal uses a quadrature phase shift keying (QPSK) or 16 quadrature amplitude modulation (QAM) modulation mode, the cycle-slip determining threshold is π/4, and the cycle-slip angle θ is 90 degrees.

6 . A cycle-slip detection apparatus, comprising:
a calculation module, configured to:
for a received signal on which phase estimation processing has been performed, calculate a first difference by subtracting a phase of a first symbol in a k th training sequence cycle from a phase of a last symbol in a (k−1) th training sequence cycle in the received signal, wherein the received signal comprises several training sequence cycles, and
when it is determined that a cycle-slip occurs in the k th or (k−1) th training sequence cycle, calculate a second difference by subtracting a phase of the first symbol in the (k+1) th training sequence cycle from a phase of the last symbol in the k th training sequence cycle, wherein k is an integer greater than or equal to 2;
a determining module, configured to : determine whether an absolute value of the first difference is greater than a set cycle-slip determining threshold; if yes, determine that a cycle-slip occurs in the k th or (k−1) th training sequence cycle; and determine whether an absolute value of the second difference is greater than the set cycle-slip determining threshold, and whether plus and minus signs of the first difference and the second difference are opposite; if yes, determine that a cycle-slip occurs in all symbols in the k th training cycle; or if not, determine that a cycle-slip occurs in a data symbol in the (k−1) th training sequence cycle; and a location module, configured to: when a cycle-slip occurs in a data symbol in the (k−1) th training sequence cycle, locate a position of the cycle-slip.

7 . The apparatus according to claim 6 , wherein the location module comprises:
a cycle-slip operator output submodule, configured to perform short-time Fourier transform or N fft -point fast Fourier transform on a phase estimation sequence corresponding to the (k−1) th training sequence cycle, and use a value of the p th frequency as an output L 1˜N of a cycle-slip detection operator corresponding to the (k−1) th training sequence cycle, wherein N is equal to a length of each training sequence cycle, the p th frequency is a low frequency from which a direct current component has been removed, and the phase estimation sequence corresponding to the (k−1) th training sequence cycle comprises phases that correspond to training sequence symbols and data symbols in the (k−1) th training sequence cycle; and a cycle-slip position location submodule, configured to : starting from the first symbol in the (k−1) th training sequence cycle, sequentially com

Assignees

• Huawei Tech Co Ltd

Inventors

• Liu Ling
• Li Liangchuan

Classifications

• H04L2027/0046

  Open loops · CPC title

• H04B10/6165

  Estimation of the phase of the received optical signal, phase error estimation or phase error correction · CPC title

• H04L2027/0095

  in a preamble or similar structure · CPC title

• H04L27/3827

  in which the carrier is recovered using only the demodulated baseband signals · CPC title

• H04L27/0014 Primary

  Carrier regulation (of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657) · CPC title