# US 8,787,505 B1 · Preamble detection with multiple receive antennas > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,505 B1 - Document ID: US8787505B1 - Status: Granted - Kind: B1 - Application number: 14/066,191 - Filed: 2013-10-29 - Granted: 2014-07-22 - Earliest claimed: 2006-05-31 - Assignees: Marvell International Ltd. - Applicants: Marvell International Ltd. - Inventors: Jungwon Lee; Hui-Ling Lou - Web page: https://patentgrep.com/patent/US8787505B1 ## CPC - H04L 27/2655: {Synchronisation arrangements} - H04L 27/2657: {Carrier synchronisation} - H04L 27/2675: {Pilot or known symbols} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A system including a differential demodulation module that generates differentially demodulated signals based on having differentially demodulated received signals. A first summing module generates a combined signal, including a plurality of symbols, by adding the differentially demodulated signals. A second summing module generates a plurality of sums for each of a plurality of derived preamble sequences, which are derived from preamble sequences. Each of the derived preamble sequences includes a plurality of derived symbols. One of the plurality of sums generated for one of the derived preamble sequences is a sum of a first portion of one of the plurality of symbols of the combined signal and a second portion of one of the derived symbols of the one of the derived preamble sequences. ## Claims ### Claim 1 A system comprising: a differential demodulation module configured to generate differentially demodulated signals by differentially demodulating received signals; a first summing module configured to generate a combined signal by adding the differentially demodulated signals, wherein the combined signal includes a plurality of symbols; and a second summing module configured to generate a plurality of sums for each of a plurality of derived preamble sequences, wherein the derived preamble sequences are derived from preamble sequences, wherein each of the derived preamble sequences includes a plurality of derived symbols, wherein one of the plurality of sums generated for one of the derived preamble sequences is a sum of (i) a first portion of one of the plurality of symbols of the combined signal and (ii) a second portion of one of the derived symbols of the one of the derived preamble sequences, wherein one of the derived symbols of one of the derived preamble sequences has a first binary value when a corresponding symbol and a symbol adjacent to the corresponding symbol in a corresponding one of the preamble sequences have opposite binary values, and wherein the one of the derived symbols has a second binary value that is opposite to the first binary value when the corresponding symbol and the symbol adjacent to the corresponding symbol have the same binary value. ### Claim 2 (depends on 1) The system of claim 1, wherein: the first portion of the one of the plurality of symbols includes a polarity of a real portion of the one of the plurality of symbols; the second portion of the one of the derived symbols includes a reversed polarity of the one of the derived symbols; and the sum is a modulo-2 sum. ### Claim 3 (depends on 1) The system of claim 1, wherein the second summing module is configured to generate cross-correlation values for the derived preamble sequences based on the plurality of sums, wherein one of the cross-correlation values generated for one of the derived preamble sequences is a sum of the plurality of sums generated for the one of the derived preamble sequences. ### Claim 4 (depends on 3) The system of claim 3, further comprising a control module configured to: select a largest cross-correlation value from the cross-correlation values, and detect one of the preamble sequences in the received signals in response to the largest cross-correlation value being greater than or equal to a predetermined threshold, wherein the predetermined threshold is based on a signal strength of the received signals. ### Claim 5 (depends on 4) The system of claim 4, wherein the control module is configured to identify, based on the detected preamble sequence, a segment of a base station that transmitted the received signals. ### Claim 6 (depends on 3) The system of claim 3, further comprising: a correlation module configured to generate correlation values, in response to two or more of the cross-correlation values being greater than or equal to a predetermined threshold, by correlating (i) the differentially demodulated signals and (ii) the derived preamble sequences that caused the two or more of the cross-correlation values to be greater than or equal to the predetermined threshold, wherein the predetermined threshold is based on a signal strength of the received signals. ### Claim 7 (depends on 6) The system of claim 6, further comprising a control module configured to: select one of the correlation values having a largest real portion, detect one of the preamble sequences in the received signals based on the largest real portion, and identify, based on the detected preamble sequence, a segment of a base station that transmitted the received signals. ### Claim 8 (depends on 6) The system of claim 6, further comprising a control module configured to: select one of the correlation values having a largest magnitude, detect one of the preamble sequences in the received signals based on the largest magnitude, and identify, based on the detected preamble sequence, a segment of a base station that transmitted the received signals. ### Claim 9 A method comprising: generating differentially demodulated signals by differentially demodulating received signals; generating a combined signal by adding the differentially demodulated signals, wherein the combined signal includes a plurality of symbols; and generating a plurality of sums for each of a plurality of derived preamble sequences, wherein the derived preamble sequences are derived from preamble sequences, wherein each of the derived preamble sequences includes a plurality of derived symbols, wherein one of the plurality of sums generated for one of the derived preamble sequences is a sum of (i) a first portion of one of the plurality of symbols of the combined signal and (ii) a second portion of one of the derived symbols of the one of the derived preamble sequences, wherein one of the derived symbols of one of the derived preamble sequences has a first binary value when a corresponding symbol and a symbol adjacent to the corresponding symbol in a corresponding one of the preamble sequences have opposite binary values, and wherein the one of the derived symbols has a second binary value that is opposite to the first binary value when the corresponding symbol and the symbol adjacent to the corresponding symbol have the same binary value. ### Claim 10 (depends on 9) The method of claim 9, wherein: the first portion of the one of the plurality of symbols includes a polarity of a real portion of the one of the plurality of symbols; the second portion of the one of the derived symbols includes a reversed polarity of the one of the derived symbols; and the sum is a modulo-2 sum. ### Claim 11 (depends on 9) The method of claim 9, further comprising generating cross-correlation values for the derived preamble sequences based on the plurality of sums, wherein one of the cross-correlation values generated for one of the derived preamble sequences is a sum of the plurality of sums generated for the one of the derived preamble sequences. ### Claim 12 (depends on 11) The method of claim 11, further comprising: selecting a largest cross-correlation value from the cross-correlation values, and detecting one of the preamble sequences in the received signals in response to the largest cross-correlation value being greater than or equal to a predetermined threshold, wherein the predetermined threshold is based on a signal strength of the received signals. ### Claim 13 (depends on 12) The method of claim 12, further comprising identifying, based on the detected preamble sequence, a segment of a base station that transmitted the received signals. ### Claim 14 (depends on 11) The method of claim 11, further comprising: generating correlation values, in response to two or more of the cross-correlation values being greater than or equal to a predetermined threshold, by correlating (i) the differentially demodulated signals and (ii) the derived preamble sequences that caused the two or more of the cross-correlation values to be greater than or equal to the predetermined threshold, wherein the predetermined threshold is based on a signal strength of the received signals. ### Claim 15 (depends on 14) The method of claim 14, further comprising: selecting one of the correlation values having a largest real portion, detecting one of the preamble sequences in the received signals based on the largest real portion, and identifying, based on the detected preamble sequence, a segment of a base station that transmitted the received signals. ### Claim 16 (depends on 14) The method of claim 14, further comprising: selecting one of the correlation values having a largest magnitude, detecting one of the preamble sequences in the received signals based on the largest magnitude, and identifying, based on the detected preamble sequence, a segment of a base station that transmitted the received signals.