# US 9,521,022 B2 · Cycle-slip detection method and apparatus, and receiver > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,521,022 B2 - Document ID: US9521022B2 - Status: Granted - Kind: B2 - Application number: 14/995,855 - Filed: 2016-01-14 - Published: 2016-05-12 - Granted: 2016-12-13 - Earliest claimed: 2013-07-15 - Assignees: Huawei Technologies Co., Ltd. - Applicants: Huawei Technologies Co., Ltd. - Inventors: Ling Liu; Liangchuan Li - Web page: https://patentgrep.com/patent/US9521022B2 ## CPC - H04L 27/0014: {Carrier regulation (of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657)} - H04B 10/6165: {Estimation of the phase of the received optical signal, phase error estimation or phase error correction} - H04L 27/3827: {in which the carrier is recovered using only the demodulated baseband signals} - H04L 2027/0046: {Open loops} - H04L 2027/0067: {Phase error detectors} - H04L 2027/0095: {in a preamble or similar structure} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## 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 kth 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 kth 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 kth 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 kth training cycle. ## Claims ### Claim 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 kth 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; in response to the absolute value of the first difference being greater than the set cycle-slip determining threshold: determining that a cycle-slip occurs in the kth 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 kth 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; in response to the absolute value of the second difference being greater than the set cycle-slip determining threshold, and in response to the plus and minus signs of the first difference and the second difference being opposite: determining that a cycle-slip occurs in all symbols in the kth training cycle; and in response to the absolute value of the second difference not being greater than the set cycle-slip determining threshold, or in response to the plus and minus signs of the first difference and the second difference not being opposite: 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. ### Claim 2 (depends on 1) The method according to claim 1, wherein locating a position of the cycle-slip comprises: performing short-time Fourier transform or Nfft-point fast Fourier transform on a phase estimation sequence corresponding to the (k−1)th training sequence cycle, and using a value of the pth frequency as an output L1˜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 pth 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 Lidx_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 as Lidx_end; and determining a maximum value Lidx between Lidx_start and Lidx_end, and determining that a symbol, corresponding to the maximum value Lidx, 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. ### Claim 3 (depends on 1) The method according to claim 1, wherein after determining that a cycle-slip occurs in all symbols in the kth 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 kth 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 kth training sequence cycle by θ; and wherein θ is a cycle-slip angle corresponding to a modulation mode of the received signal. ### Claim 4 (depends on 2) The method according to claim 2, wherein after determining that a symbol, corresponding to the maximum value Lidx, 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 φk, idx corresponding to the symbol in which the cycle-slip occurs with a phase φk, idx-1 corresponding to a previous symbol; and if φk, idx-φk, idx-1>0, in the (k−1)th training sequence cycle, decreasing phases φk, idx˜N corresponding to symbols starting from the symbol in which the cycle-slip occurs to the last symbol by θ; or if φk, idx-φk, idx-1<0, in the (k−1)th training sequence cycle, increasing phases φk, idx˜N corresponding to symbols starting from the symbol in which the cycle-slip occurs to the last symbol by θ; and wherein θ is a cycle-slip angle corresponding to a modulation mode of the received signal. ### Claim 5 (depends on 1) 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. ### Claim 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 kth 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 kth 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 kth 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; in response to the absolute value of the first difference being greater than the set cycle-slip determining threshold: determine that a cycle-slip occurs in the kth 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; in response to the absolute value of the second difference being greater than the set cycle-slip determining threshold, and in response to the plus and minus signs of the first difference and the second difference being opposite: determine that a cycle-slip occurs in all symbols in the kth training cycle; and in response to the absolute value of the second difference not being greater than the set cycle-slip determining threshold, or in response to the plus and minus signs of the first difference and the second difference not being opposite: 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. ### Claim 7 (depends on 6) 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 Nfft-point fast Fourier transform on a phase estimation sequence corresponding to the (k−1)th training sequence cycle, and use a value of the pth frequency as an output L1˜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 pth 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 compare 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, record the cycle-slip detection operator corresponding to the symbol as Lidx_start; starting from the last symbol in the (k−1)th training sequence cycle, sequentially compare 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, record the cycle-slip detection operator corresponding to the symbol as Lidx_end; and determine a maximum value Lidx between Lidx_start and Lidx_end, and determine that a symbol, corresponding to the maximum value Lidx, 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. ### Claim 8 (depends on 6) The apparatus according to claim 6, further comprising a first cycle-slip correction module, configured to: if the first difference is greater than 0 and the second difference is less than 0, increase phases corresponding to all the symbols in the kth training sequence cycle by θ; or if the first difference is less than 0 and the second difference is greater than 0, decrease phases corresponding to all the symbols in the kth training sequence cycle by θ; and wherein θ is a cycle-slip angle corresponding to a modulation mode of the received signal. ### Claim 9 (depends on 7) The apparatus according to claim 7, further comprising a second cycle-slip correction module, configured to: compare a phase value φk, idx corresponding to the symbol in which the cycle-slip occurs with a phase φk, idx-1 corresponding to a previous symbol; and if φk, idx-1−φk, idx-1>0, in the (k−1)th training sequence cycle, decrease phases φk, idx˜N corresponding to symbols starting from the symbol in which the cycle-slip occurs to the last symbol by θ; or if φk, idx−φk, idx-1<0, in the (k−1)th training sequence cycle, increase phases φk, idx˜N corresponding to symbols starting from the symbol in which the cycle-slip occurs to the last symbol by θ; and wherein θ is a cycle-slip angle corresponding to a modulation mode of the received signal. ### Claim 10 A cycle-slip detection apparatus comprising: a non-transitory memory; and a processor coupled to the memory and configured with processor-executable instructions to perform the following: 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 kth 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; in response to the absolute value of the first difference being greater than the set cycle-slip determining threshold: determining that a cycle-slip occurs in the kth 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 kth 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; in response to the absolute value of the second difference being greater than the set cycle-slip determining threshold, and in response to the plus and minus signs of the first difference and the second difference being opposite: determining that a cycle-slip occurs in all symbols in the kth training cycle; and in response to the absolute value of the second difference not being greater than the set cycle-slip determining threshold, or in response to the plus and minus signs of the first difference and the second difference not being opposite: 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. ### Claim 11 (depends on 10) The apparatus according to claim 10, wherein the processor is configured with processor-executable instructions to perform the following: performing short-time Fourier transform or Nfft-point fast Fourier transform on a phase estimation sequence corresponding to the (k−1)th training sequence cycle, and using a value of the pth frequency as an output L1˜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 pth 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 Lidx_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 as Lidx_end ; and determining a maximum value Lidx between Lidx_start and Lidx_end , and determining that a symbol, corresponding to the maximum value Lidx, 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.