# US 8,787,483 B1 · Method and apparatus for detecting a desired signal in the presence of an interfering signal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,483 B1 - Document ID: US8787483B1 - Status: Granted - Kind: B1 - Application number: 13/659,709 - Filed: 2012-10-24 - Granted: 2014-07-22 - Earliest claimed: 2011-10-25 - Assignees: Marvell International Ltd. - Applicants: Marvell International Ltd. - Inventors: Yakun Sun; Krishna Srikanth Gomadam; Jiwoong Choi; Raphael Cendrillon; Hui-Ling Lou; Yan Zhang - Web page: https://patentgrep.com/patent/US8787483B1 ## CPC - H04L 1/0048: {in conjunction with detection of multiuser or interfering signals, e.g. iteration between CDMA or MIMO detector and FEC decoder (for spatial equalizer H04L25/03286)} - H04L 25/03248: {Arrangements for operating in conjunction with other apparatus} - H04L 25/03891: {Spatial equalizers (MIMO diversity systems H04B7/0413)} - H04L 27/0012: {arrangements for identifying the type of modulation} - H04B 7/0413: MIMO systems - H04L 1/06: using space diversity - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## Abstract In accordance with an embodiment, there is provided a method comprising receiving, at a receiver, a desired signal and an interfering signal, wherein the interfering signal was transmitted with a modulation unknown to the receiver; identifying a likely modulation corresponding to the modulation with which the interfering signal was transmitted; and decoding the desired signal using a modulation dependent multiple-input multiple output (MIMO) detection, wherein the modulation dependent MIMO detection is based at least in part on the identified likely modulation corresponding to the modulation with which the interfering signal was transmitted, wherein the modulation dependent MIMO detection includes maximum likelihood (ML) detection. ## Claims ### Claim 1 A method, comprising: receiving, at a receiver, a desired signal and an interfering signal, wherein the interfering signal was transmitted with a modulation unknown to the receiver; identifying a likely modulation corresponding to the modulation with which the interfering signal was transmitted; and decoding the desired signal using a modulation dependent multiple-input multiple output (MIMO) detection, wherein the modulation dependent MIMO detection is based at least in part on the identified likely modulation corresponding to the modulation with which the interfering signal was transmitted, wherein the modulation dependent MIMO detection includes maximum likelihood (ML) detection. ### Claim 2 (depends on 1) The method of claim 1, wherein identifying the likely modulation comprises arbitrarily selecting a modulation from a set of possible modulations. ### Claim 3 (depends on 1) The method of claim 1, wherein identifying the likely modulation comprises calculating a superposition of multiple possible modulations of the interfering signal. ### Claim 4 (depends on 1) The method of claim 1, wherein identifying the likely modulation comprises applying a linear receiver to the interfering signal to identify the likely modulation. ### Claim 5 (depends on 4) The method of claim 4, further comprising: detecting the interfering signal using the linear receiver multiple times, such that for each time of the multiple times, a corresponding possible modulation from a set of modulations is assumed while detecting the interfering signal using the linear receiver for the corresponding time; and maximizing an a-posteriori probability of each of the possible modulations from the set of modulations. ### Claim 6 (depends on 5) The method of claim 5, wherein maximizing the a-posteriori probability of the possible modulation from the set of modulations and detecting the interfering signal using the linear receiver is based at least in part on assuming that the possible modulation is simplified by minimizing a minimum distance offset by a value that is based on one or both of the possible modulation and a residual noise. ### Claim 7 (depends on 5) The method of claim 5, wherein maximizing the a-posteriori probability of the possible modulation from the set of modulations and detecting the interfering signal using the linear receiver is based at least in part on assuming that the possible modulation is simplified by maximizing at least in part a sum of largest K conditional probabilities. ### Claim 8 (depends on 5) The method of claim 5, wherein an a-priori probability of the possible modulation is scaled at least in part in accordance with a distribution of the interfering signal detected by the linear receiver assuming the possible modulation. ### Claim 9 (depends on 1) The method of claim 1, wherein: identifying the likely modulation comprises decoding the interfering signal multiple times using different modulations from a set of possible modulations; and determining which of the modulations results in accurate decoding of the interfering signal. ### Claim 10 (depends on 1) The method of claim 1, wherein identifying the likely modulation and decoding the desired signal comprise maximizing an a-posteriori probability of the desired signal and a possible modulation from a set of modulations. ### Claim 11 (depends on 10) The method of claim 10, wherein maximizing the a-posteriori probability is simplified at least in part by minimizing a minimum distance offset by a value, and wherein the value is based on one or more of the possible modulation, a noise power, and a condition of a channel. ### Claim 12 (depends on 10) The method of claim 10, wherein maximizing the a-posteriori probability is simplified by maximizing at least in part a sum of the largest K conditional probabilities. ### Claim 13 (depends on 1) The method of claim 1, wherein identifying the likely modulation further comprises selecting at least in part a subset of the received signal. ### Claim 14 (depends on 1) The method of claim 1, wherein identifying the likely modulation further comprises: determining a reliability of the likely modulation identified; and replacing the modulation dependent MIMO detection by a linear receiver. ### Claim 15 (depends on 1) The method of claim 1, wherein the interfering signal is a first interfering signal, and wherein the method further comprises: receiving, at the receiver, a plurality of interfering signals including the first interfering signal, wherein each of the plurality of interfering signals were transmitted with a respective modulation unknown to the receiver; and identifying a plurality of likely modulations corresponding to a plurality of modulations with which the plurality of interfering signals were respectively transmitted, wherein the modulation dependent MIMO detection is based at least in part on the identified plurality of likely modulations corresponding to the plurality of modulations with which the plurality of interfering signals were respectively transmitted. ### Claim 16 A system comprising: one or more antennas configured to receive a desired signal and an interfering signal, wherein the interfering signal was transmitted with a modulation unknown to the system; and a data processing unit coupled to the one or more antennas, wherein the data processing unit is configured to (i) identify a likely modulation corresponding to the modulation with which the interfering signal was transmitted, and (ii) decode the desired signal using a modulation dependent detection, wherein the modulation dependent detection is based at least in part on the identified likely modulation corresponding to the modulation with which the interfering signal was transmitted, wherein the modulation dependent detection includes maximum likelihood (ML) detection. ### Claim 17 (depends on 16) The system of claim 16, wherein the data processing unit is further configured to identify the likely modulation by arbitrarily selecting a modulation from a set of possible modulations. ### Claim 18 (depends on 16) The system of claim 16, wherein the data processing unit is further configured to identify the likely modulation by calculating a superposition of multiple possible modulations of the interfering signal. ### Claim 19 (depends on 16) The system of claim 16, wherein the data processing unit is further configured to identify the likely modulation by applying a linear receiver to the interfering signal. ### Claim 20 (depends on 16) The system of claim 16, wherein the data processing unit is further configured to identify the likely modulation by (i) detecting the interfering signal using the linear receiver multiple times, such that for each time of the multiple times, a corresponding possible modulation from a set of modulations is assumed while detecting the interfering signal using the linear receiver for the corresponding time, and (ii) maximizing an a-posteriori probability of each of the possible modulations from the set of modulations. ### Claim 21 (depends on 20) The system of claim 20, wherein the data processing unit is further configured to maximize the a-posteriori probability of the possible modulation and detect the interfering signals by: minimizing at least in part a minimum distance offset by a value, wherein the value is based on one or more of the possible modulation and a residual noise. ### Claim 22 (depends on 20) The system of claim 20, wherein the data processing unit is further configured to maximize the a-posteriori probability of the possible modulation and detect the interfering signals by: maximizing at least in part a sum of the largest K conditional probabilities. ### Claim 23 (depends on 20) The system of claim 20, wherein the data processing unit is further configured to scale an a-priori probability of the possible modulation based at least in part on a distribution of the interfering signal detected by the linear receiver assuming the possible modulation. ### Claim 24 (depends on 16) The system of claim 16, wherein the data processing unit is further configured to identify the likely modulation by (i) decoding the interfering signal multiple times using different modulations from a set of possible modulations and (ii) determining which of the modulations results in accurate decoding of the interfering signal. ### Claim 25 (depends on 16) The system of claim 16, wherein the data processing unit is further configured to identify the likely modulation and decode the desired signal by maximizing an a-posteriori probability of the desired signal and a possible modulation from a set of modulations. ### Claim 26 (depends on 25) The system of claim 25, wherein the data processing unit is further configured to simplify maximizing the a-posteriori probability at least in part by minimizing the minimum distance offset by a value, and wherein the value depends on one or more factors that are the possible modulation, the noise power, the channels. ### Claim 27 (depends on 25) The system of claim 25, wherein the data processing unit is further configured to simplify maximizing the a-posteriori probability by maximizing at least in part a sum of the largest K conditional probabilities. ### Claim 28 (depends on 16) The system of claim 16, wherein the data processing unit is further configured to select at least in part a subset of received signals to identify the likely modulation. ### Claim 29 (depends on 16) The system of claim 16, wherein the data processing unit is further configured to (i) determine a reliability of the likely modulation, and (ii) based on determine the reliability of the likely modulation, replace the modulation dependent MIMO detection with a detection using a linear receiver.