# US 9,521,025 B1 · System and method for detecting ternary sequences > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,521,025 B1 - Document ID: US9521025B1 - Status: Granted - Kind: B1 - Application number: 14/730,479 - Filed: 2015-06-04 - Granted: 2016-12-13 - Earliest claimed: 2014-06-05 - Assignees: Marvell International Ltd. - Applicants: Marvell International Ltd. - Inventors: Jin Zhang; Kok-Wui Cheong - Web page: https://patentgrep.com/patent/US9521025B1 ## CPC - H04L 27/2613: {Structure of the reference signals} - H04B 10/60: Receivers - H04L 25/4923: {using ternary codes (H04L25/4927 takes precedence)} - H04L 27/2647: {Arrangements specific to the receiver only (equalisation H04L27/01)} - H04L 27/2663: {Coarse synchronisation, e.g. by correlation} - H04L 27/2697: {in combination with other modulation techniques} - H04L 5/003: {Arrangements for allocating sub-channels of the transmission path} - H04L 27/2671: {Time domain} - H04L 27/2675: {Pilot or known symbols} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## Abstract Systems and methods for detection of a ternary sequence are provided. An example apparatus includes a receiver configured to receive an OFDM signal comprising a plurality of OFDM Resource Elements (REs). A processor is coupled to the receiver and is configured to detect a presence of a known ternary sequence in the received OFDM signal. The processor is configured to detect the ternary sequence by determining a correlation between a first set of the OFDM REs and a first set of symbols of the ternary sequence. A power of each RE of a second set of the OFDM REs is determined. A sum of the powers is determined. A detection value is based on the correlation and the sum. The ternary sequence is determined to be present in the signal based on a comparison of the detection value to a threshold. ## Claims ### Claim 1 An apparatus comprising: a receiver configured to receive an Orthogonal Frequency Division Multiplexing (OFDM) signal comprising a plurality of OFDM Resource Elements (REs); and a processor coupled to the receiver, wherein the processor is configured to detect a presence of a known ternary sequence in the received OFDM signal, wherein the known ternary sequence is defined via a ternary alphabet of −1, 0, and +1, and wherein the processor is configured to detect the known ternary sequence by at least determining a correlation between (i) a first set of the OFDM REs, and (ii) a first set of symbols of the known ternary sequence, determining a power of each RE of a second set of the OFDM REs, determining a sum of the powers, determining a detection value based on the correlation and the sum, and determining that the known ternary sequence is present in the received OFDM signal based on a comparison of the detection value to a predetermined threshold. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the determining of the power of each RE of the second set comprises: determining an absolute value of each RE of the second set of the OFDM REs, and squaring each of the absolute values, wherein the sum is determined by summing the squared absolute values. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein each OFDM RE has a time-frequency slot position that comprises a frequency interval of one OFDM sub-carrier and a time interval of one OFDM symbol. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein: the first set of symbols of the known ternary sequence have values of −1 or +1, and a second set of symbols of the known ternary sequence have a value of 0, the first set of the OFDM REs have time-frequency slot positions that correspond to positions of the first set of symbols in the known ternary sequence, and the second set of the OFDM REs have time-frequency slot positions that correspond to positions of the second set of symbols in the known ternary sequence. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the determining of the correlation between the first set of the OFDM REs and the first set of symbols of the known ternary sequence comprises: multiplying each RE of the first set of the OFDM REs by a corresponding symbol of the first set of symbols to determine a product, the multiplied REs having time-frequency slot positions that correspond to positions of the first set of symbols in the known ternary sequence; and summing the products. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein the determining of the correlation comprises: determining an absolute value of the sum of the products, wherein the OFDM signal contains unknown carrier phase rotations. ### Claim 7 (depends on 5) The apparatus of claim 5, wherein the determining of the correlation comprises: determining a real number portion of the sum of the products, wherein the OFDM signal does not contain unknown carrier phase rotations. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the detection value is based on O_P=(2*Corr)−Sum, where O_P is the detection value, Corr is the correlation, and Sum is the sum. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the ternary sequence in the received OFDM signal is a burst marker sequence, the burst marker sequence indicating a start of a data burst in the OFDM signal or indicating an end of a data burst in the OFDM signal. ### Claim 10 (depends on 1) The apparatus of claim 1, wherein the determining that the known ternary sequence is present in the received OFDM signal is based on a determination that the detection value is greater than or equal to the predetermined threshold. ### Claim 11 An apparatus comprising: a receiver configured to receive an Orthogonal Frequency Division Multiplexing (OFDM) signal comprising a plurality of OFDM Resource Elements (REs); and a processor coupled to the receiver, wherein the processor is configured to detect a presence of a known ternary sequence in the received OFDM signal, wherein the known ternary sequence is defined via a ternary alphabet of −1, 0, and +1, and wherein the processor is configured to detect the known ternary sequence at least by determining a correlation between (i) a first set of the OFDM REs, and (ii) a first set of symbols of the known ternary sequence, the first set of symbols having values of −1 or +1, and the first set of the OFDM REs having time-frequency slot positions that correspond to positions of the first set of symbols in the known ternary sequence, determining an absolute value of each RE of a second set of the OFDM REs, the second set of the OFDM REs having time-frequency slot positions that correspond to positions of symbols in the known ternary sequence having a value of 0, squaring each of the absolute values, determining a sum of the squared absolute values, scaling the determined correlation by a factor of two, combining the scaled correlation and the sum to determine a detection value, and determining that the known ternary sequence is present in the received OFDM signal based on a determination that the detection value is greater than or equal to a predetermined threshold. ### Claim 12 A method comprising: receiving an Orthogonal Frequency Division Multiplexing (OFDM) signal comprising a plurality of OFDM Resource Elements (REs); and detecting a presence of a known ternary sequence in the received OFDM signal, wherein the known ternary sequence is defined via a ternary alphabet of −1, 0, and +1, and wherein detecting the presence of the known ternary sequence in the received OFDM signal includes determining a correlation between (i) a first set of the OFDM REs, and (ii) a first set of symbols of the known ternary sequence, determining a power of each RE of a second set of the OFDM REs, determining a sum of the powers, determining a detection value based on the correlation and the sum, and determining that the known ternary sequence is present in the received OFDM signal based on a comparison of the detection value to a predetermined threshold. ### Claim 13 (depends on 12) The method of claim 12, wherein the determining of the power of each RE of the second set comprises: determining an absolute value of each RE of the second set of the OFDM REs, and squaring each of the absolute values, wherein the sum is determined by summing the squared absolute values. ### Claim 14 (depends on 12) The method of claim 12, wherein each OFDM RE has a time-frequency slot position that comprises a frequency interval of one OFDM sub-carrier and a time interval of one OFDM symbol. ### Claim 15 (depends on 14) The method of claim 14, wherein: the first set of symbols of the known ternary sequence have values of −1 or +1, and a second set of symbols of the known ternary sequence have a value of 0, the first set of the OFDM REs have time-frequency slot positions that correspond to positions of the first set of symbols in the known ternary sequence, and the second set of the OFDM REs have time-frequency slot positions that correspond to positions of the second set of symbols in the known ternary sequence. ### Claim 16 (depends on 12) The method of claim 12, wherein the determining of the correlation between the first set of the OFDM REs and the first set of symbols of the known sequence comprises: multiplying each RE of the first set of the OFDM REs by a corresponding symbol of the first set of symbols to determine a product, the multiplied REs having time-frequency slot positions that correspond to positions of the first set of symbols in the known ternary sequence; and summing the products. ### Claim 17 (depends on 16) The method of claim 16, wherein the determining of the correlation comprises: determining an absolute value of the sum of the products, wherein the OFDM signal contains unknown carrier phase rotations. ### Claim 18 (depends on 16) The method of claim 16, wherein the determining of the correlation comprises: determining a real number portion of the sum of the products, wherein the OFDM signal does not contain unknown carrier phase rotations. ### Claim 19 (depends on 12) The method of claim 12, wherein the detection value is based on O_P=(2*Corr)−Sum, where O_P is the detection value, Corr is the correlation, and Sum is the sum. ### Claim 20 (depends on 12) The method of claim 12, wherein the ternary sequence in the received OFDM signal is a burst marker sequence, the burst marker sequence indicating a start of a data burst in the OFDM signal or indicating an end of a data burst in the OFDM signal. ### Claim 21 (depends on 12) The method of claim 12, wherein the determining that the known ternary sequence is present in the received OFDM signal is based on a determination that the detection value is greater than or equal to the predetermined threshold.