# US 7,610,028 B2 · Method and system for reduction of peak-to-average power ratio of transmission signals comprising overlapping waveforms > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,610,028 B2 - Document ID: US7610028B2 - Status: Granted - Kind: B2 - Application number: 10/358,257 - Filed: 2003-02-05 - Published: 2003-07-17 - Granted: 2009-10-27 - Earliest claimed: 1999-06-02 - Assignees: AT&T Corp. - Inventors: Leonard Joseph Cimini, Jr.; Nelson Ray Sollenberger - Web page: https://patentgrep.com/patent/US7610028B2 ## CPC - H04L 27/2623: {Reduction thereof by clipping} - H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)} - H04B 7/2628: {using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] (H04B7/2618 takes precedence)} - H04L 27/2614: {Peak power aspects} - H04L 27/2621: {Reduction thereof using phase offsets between subcarriers} - H04B 2201/70706: with means for reducing the peak-to-average power ratio - 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 method and system for reducing the peak to average power ratio (PAP) of a signal with low computational complexity. According to one embodiment, the present invention is applied to reduce the PAP of an OFDM signal. According to an alternative embodiment, the present invention is applied to reduce the PAP of a CDMA signal. Rather than seeking the optimum solution, which involves significant computational complexity, the present invention provides for a number of sub-optimal techniques for reducing the PAP of an OFDM signal but with much lower computational complexity. In particular, according to one embodiment utilizing the PTS approach, an iterative technique is used to assign phase factors to each of a set of partial transmit sequences from a set of possible phase factors. Experimental results using the iterative technique showed only a slight degradation (1 dB) from the optimal approach using the same number of subblocks and subcarriers. In an alternative embodiment, which avoids feedback required by the iterative approach, a sequence of phase factors are generated randomly and assigned to each of a set of partial transmit sequences. This procedure is repeated for a predetermined number of trials and the random sequence generating the lowest PAP is selected. In a third embodiment, a set of phase factors is generated using a structured sequence such as a Walsh sequence. ## Claims ### Claim 1 A method for reducing a peak to average power ratio (PAP) of a signal comprising steps of: (a) assigning a phase factor from a set of possible phase factors to each of a plurality of vectors; (b) calculating a first PAP value of a combined signal comprising a linear combination of each of the vectors multiplied by its assigned phase factor; and (c) for each of the plurality of vectors executing the step of assigning a final phase factor to the vector, wherein the final phase factor is selected from the set of possible phase factors on a basis that it minimizes a PAP of a combined signal. ### Claim 2 (depends on 1) The method according to claim 1, wherein the signal is an orthogonal frequency division multiplexed (OFDM) signal. ### Claim 3 (depends on 1) The method according to claim 1, wherein the signal is a wireless signal transmitted using code division multiple access (CDMA). ### Claim 4 (depends on 1) The method according to claim 1, wherein the signal is a wireless signal transmitted using multicode CDMA. ### Claim 5 (depends on 1) The method according to claim 1, wherein the plurality of vectors are partial transmit sequences. ### Claim 6 A wireless transmission system with reduced PAP of transmitted signals comprising: (a) a wireless transmitter including: (i) a transponder device; (ii) a memory; (iii) a processor adapted to: A. assign a phase factor from a set of possible phase factors to each of a plurality of vectors; B. calculate a first PAP value of a combined signal comprising a linear combination of each of the vectors multiplied by its assigned phase factor; C. for each of the plurality of vectors, assign a final phase factor to the vector, wherein the final phase factor is selected from the set of possible phase factors on a basis that it minimizes a PAP of a combined signal; and (b) a wireless receiver including: (i) a transponder; (ii) a memory; (iii) a processor. ### Claim 7 A wireless transmission with reduced PAP of transmitted signals comprising: (i) a transponder; (ii) a memory; and (iii) a processor adapted to: A. assign a phase factor from a set of possible phase factors to each of a plurality of vectors; B. calculate a first PAP value of a combined signal comprising a linear combination of each of the vectors multiplied by its assigned phase factor; C. for each of the plurality of vectors, assign a final phase factor to the vector, wherein the final phase factor is selected from the set of possible phase factors on a basis that it minimizes a PAP of a combined signal.