# US 2010/0166105 A1 · Transmitter and the Method Therefor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2010/0166105 A1 - Document ID: US20100166105A1 - Status: Published application - Kind: A1 - Application number: 12/643,042 - Filed: 2009-12-21 - Published: 2010-07-01 - Earliest claimed: 2008-12-31 - Assignees: Industrial Technology Research Institute - Inventors: Jia-Hao Wu; Yun-Yi Shih; Pang-An Ting; Ming-Che Lin - Web page: https://patentgrep.com/patent/US20100166105A1 ## CPC - H04L 27/262: {Reduction thereof by selection of pilot symbols} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A transmitter and the method therefor are provided. The transmitter is applied in an orthogonal frequency division multiplexing (OFDM) based or other multicarrier communication systems. The transmitter uses N sub-carriers. Among the N sub-carriers, L sub-carriers (or tones) are reserved for PAPR reduction. L is less than N. The method includes the following steps. Original frequency domain data symbols are generated and fed into the reserved-tone symbol generation unit. The reserved-tone symbols are generated by using pure frequency domain signal processing. Then the reserved-tone symbols are combined with original data symbols to generate combined PAPR reduction signal. The resultant PAPR reduction signal can be fed into reserved-tone symbol generation unit iteratively to obtain updated reserved-tone symbols. For proper iterations, the original data symbols combined with L frequency domain reserved-tone symbols will result in lower PAPR transmit signal. ## Claims ### Claim 1 A method for reducing a peak-to-average power ratio (PAPR), the method being applied by using N sub-carriers, L sub-carriers of the N sub-carriers being reserved sub-carriers, L being less than N, the method comprising: receiving a data signal, the envelope power of the data signal having a constant power and a fluctuant power; generating L reserved sub-carrier symbols of the L sub-carriers located in the reserved sub-carriers; modifying the L reserved sub-carrier symbols according to the data signal, and generating a to-be-combined signal accordingly; and combining the to-be-combined signal into the data signal in frequency domain. ### Claim 2 (depends on 1) The method according to claim 1, wherein the data signal has N data symbols located in the N sub-carriers, the N data symbols correspond to an aperiodic auto-correlation function (AACF) vector, the L reserved sub-carrier symbols correspond to a reserved sub-carrier symbol vector, and in the step of modifying the L reserved sub-carrier symbols, the L reserved sub-carrier symbols are modified according to a gradient or any other algorithmic methods of the square of the absolute value of the AACF vector at the reserved sub-carrier symbol vector, or modified according to the absolute value for the AACF vector to the pth power, wherein p is larger than 0. ### Claim 3 (depends on 2) The method according to claim 2, wherein a set of sub-carrier indices of the L sub-carriers of the reserved sub-carriers is denoted as U, wherein U={k0, k1, . . . kL−1}, the N data symbols of the data signal are denoted as X0, X1, . . . XN−1 and the data vector is defined as X=[X0, X1, . . . , XN−1]T, wherein Xi is the ith data symbol, and i is an integer between 0 to N−1, before the data is combined into the reserved sub-carrier symbol, if iεU, Xi=0 the AACF vector is denoted as ρ, the L reserved sub-carrier symbols are denoted as Xk0, Xk1, . . . , XkL−1, the reserved sub-carrier symbol vector is denoted as XR=[Xk0, Xk1, . . . , XkL−1]T, XR(n+1) denotes an n+1th modified XR, and XR(n) denotes an n+1th pre-modified XR, then it is derived that ρ = [ ρ  ( 1 ) , ρ  ( 2 ) , …  , ρ  ( N - 1 ) ] T , and X R ( n + 1 ) = X R ( n ) - μ  ∇ X R   ρ  2   X R ( n ) ,  wherein   ρ  ( u ) = ∑ k = 0 N - u - 1   X k  X k + u *   for   1 ≤ u ≤ N - 1. ### Claim 4 (depends on 1) The method according to claim 1, wherein the step of modifying the L reserved sub-carrier symbols comprises modifying the L reserved sub-carrier symbols by iteration means. ### Claim 5 (depends on 1) The method according to claim 1, wherein the L reserved sub-carrier symbols are divided into several groups of reserved sub-carrier symbols, and in the step of modifying the L reserved sub-carrier symbols, the several groups of reserved sub-carrier symbols are modified sequentially so as to modify the L reserved sub-carrier symbols. ### Claim 6 (depends on 1) The method according to claim 1, wherein the L reserved sub-carrier symbols are divided into several groups of reserved sub-carrier symbols, and in the step of modifying the L reserved sub-carrier symbols, the several groups of reserved sub-carrier symbols are modified in parallel so as to modify the L reserved sub-carrier symbols. ### Claim 7 (depends on 1) The method according to claim 1, wherein the transmitter comprises a filter, the filter has a frequency response function denoted as H, Hk denotes the frequency response coefficient at the kth sub-carrier, the data signal has N data symbols located in N sub-carriers, and the step of modifying the L reserved sub-carrier symbols comprises the following steps: multiplying the N data symbols with a corresponding Hk, respectively; modifying the L reserved sub-carrier symbols according to the N data symbols being multiplied with Hk; and multiplying the to-be-combined signal with 1/Hk; wherein the to-be-combined signal being multiplied with 1/Hk is served as the to-be-combined signal for use in combining with the data signal. ### Claim 8 A transmitter, applied in an orthogonal frequency division multiplexing (OFDM) based system, the transmitter using N sub-carriers, L sub-carriers of the N sub-carriers being reserved sub-carriers, L being less than N, the transmitter comprising: a modulation unit, for outputting a data signal, the envelope power of the data signal having a constant power and a fluctuant power; a reserved sub-carrier symbol generation unit, for generating L reserved sub-carrier symbols of the L sub-carriers located in the reserved sub-carriers, for modifying the L reserved sub-carrier symbols according to the data signal and generating a to-be-combined signal accordingly; and a combination unit, for combining the to-be-combined signal into the data signal in frequency domain. ### Claim 9 (depends on 8) The transmitter according to claim 8, wherein the data signal has N data symbols located in the N sub-carriers, the N data symbols correspond to an aperiodic auto-correlation function (AACF) vector, the L reserved sub-carrier symbols correspond to a reserved sub-carrier symbol vector, and the modulation unit modifies the L reserved sub-carrier symbols according to a gradient or any other algorithmic methods of the square of the absolute value of the AACF vector at the reserved sub-carrier symbol vector, or according to the absolute value for the AACF vector to the pth power, wherein p is larger than 0. ### Claim 10 (depends on 9) The transmitter according to claim 9, wherein a set of sub-carrier indices of the L sub-carriers of the reserved sub-carriers is denoted as U, wherein U={k0, k1, . . . , kL−1}, the N data symbols of the data signal are denoted as X0, X1, . . . XN−1 and the data vector is defined as X=[X0, X1, . . . , XN−1]T, wherein Xi is the ith data symbol, and i is an integer between 0 to N−1, before the data is combined into the reserved sub-carrier symbol, if iεU, Xi=0, the AACF vector is denoted as ρ, the L reserved sub-carrier symbols are denoted as Xk0, Xk1, . . . , XkL−1, the reserved sub-carrier symbol vector is denoted as XR=[Xk0, Xk1, . . . , XkL−1]T, XR(n+1) denotes an n+1th modified XR, and XR(n) denotes an n+1th pre-modified XR, then it is derived that ρ = [ ρ  ( 1 ) , ρ  ( 2 ) , …  , ρ  ( N - 1 ) ] T , and X R ( n + 1 ) = X R ( n ) - μ  ∇ X R   ρ  2   X R ( n ) ,  wherein   ρ  ( u ) = ∑ k = 0 N - u - 1   X k  X k + u *   for   1 ≤ u ≤ N - 1. ### Claim 11 (depends on 8) The transmitter according to claim 8, wherein the modulation unit modifies the L reserved sub-carrier symbols by iteration means. ### Claim 12 (depends on 8) The transmitter according to claim 8, wherein the L reserved sub-carrier symbols comprise several groups of reserved sub-carrier symbols, and the modulation unit modifies the L reserved sub-carrier symbols sequentially, so as to modify the L reserved sub-carrier symbols. ### Claim 13 (depends on 8) The transmitter according to claim 8, wherein the L reserved sub-carrier symbols comprise several groups of reserved sub-carrier symbols, and the modulation unit modifies the L reserved sub-carrier symbols in parallel, so as to modify the L reserved sub-carrier symbols. ### Claim 14 (depends on 8) The transmitter according to claim 8, wherein the data signal has N data symbols located in N sub-carriers, and the transmitter further comprises: a filter, having a frequency response function denoted as H, wherein Hk denotes the frequency response coefficient at the kth sub-carrier a first multiplier, for multiplying the N data symbols with a corresponding Hk, respectively, wherein the reserved sub-carrier symbol generation unit modifies the L reserved sub-carrier symbols according to the N data symbols being multiplied with Hk, and generating the to-be-combined signal accordingly; a second multiplier, for multiplying the to-be-combined signal with 1/Hk, and for outputting the multiplied signal to the combination unit; and a conversion unit, for converting the data signal being processed by the combination unit into a time-domain transmitting signal, and for outputting the transmitting signal to the filter.