Low Complexity Rotation Algorithm for Reducing PAPR in Partial Transmits

: High peak to average power ratio (PAPR) is considered as a prime challenge in orthogonal frequency 17 division multiplexing. The partial transmits sequence (PTS) technique is one of the most effective methods for 18 restraining the PAPR pattern. This study proposes a novel approach for enhancing PAPR reduction performance 19 in a PTS by partitioning each subblock into two parts then exchanging the first sample with the last selection in 20 each part of the subblock to generate a new partitioning scheme. The proposed algorithm is analysed and applied 21 to typical traditional segmentation schemes, namely, the adjacent, interleaving and pseudo-random schemes. 22 Moreover, simulation is conducted with two scenarios in which the number of subcarriers is set to 128 and 256. 23 In both systems, the improved segmentation schemes demonstrate PAPR reduction performance that is superior 24 to that of the traditional strategies. Furthermore, the computational complexity level of the enhanced adjusted PTS 25 scheme is low compared with that of the conventional schemes.


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subblock lengths on the adjacent (Ad) partitioning scheme and found that fixed subblock lengths can realise PAPR reduction performance better than varying subblock lengths [5]. Vidya   which was suggested by Muller in 1997, is the most efficient reduction method [15]. The PTS algorithm can lessen In an OFDM system, baseband subcarriers are often modulated using an Inverse Fast Fourier transform (IFFT) algorithm. Hence, the OFDM signal is expressed as (Kim, 2016)  89 The PAPR problem should be resolved before the OFDM signal is transmitted. The PTS technique is 90 among the methods that can diminish high PAPRs effectively. The mechanism of the PTS technique involves the 91 partitioning of the input data symbol into V subblocks. Next, the N-IFFT block is utilised to modulate the N-of each subblock to produce a set of candidate signals. Given the influence of the phase coefficients, the candidate signals will exhibit different PAPR value levels. Accordingly, the candidate signal that achieves a low PAPR is sent to the receiver side [20] as shown in Figure 1.    Table 1. However, the signal obtained from every subblock is restored via row-wise mapping based on the divide-and-conquer approach.

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where 1 ≤ ≤ and 1 ≤ ≤ represent the elements of the -th row and -th column of y(q,p), respectively.

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The active subcarriers are located only at the v row depending on the IL property of the IL-PTS method; therefore, (13) The CC of the IL-PTS is the lowest among the traditional schemes [24]. This result is because the IL-

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PTS method requires few IFFT stages to transform the subblocks in the TD depending on the Cooley-Tukey IFFT 169 algorithm.

Pseudo-random Segmentation Scheme (PR-PTS) 172
The PR-PTS algorithm is the most convenient traditional segmentation scheme with PAPR reduction 188

Adjacent Segmentation Scheme (Ad-PTS) 189
The Ad-PTS algorithm involves a simple partitioning process, but its PAPR reduction performance is lower than that of the PR-PTS scheme. N/V consecutive subcarriers are assigned sequentially inside the subblocks  (17)

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In this section, a new segmentation method is proposed to enhance PAPR reduction capacity. In OFDM 202 systems, the input data symbol has a noticeable correlation with its elements; thus, the transmitted OFDM signal In which, Next, the first element is exchanged with the last element in each part of the subblocks. Therefore, the 218 two parts of a subblock can be expressed as: The rotation process is implemented for all the subblocks in the PTS matrix. Therefore, the new matrix 221 of the R-PTS method can be expressed as: In which, The R-PTS algorithm exchanges the terminal samples within the subblocks; thus, the correlation among 227 the samples will be lower than that in the original matrix. Accordingly, the PAPR reduction gain of the PTS 228 technique will be improved. In this study, the R-PTS algorithm is applied to the three conventional segmentation 4.1.

Rotation IL-PTS Scheme
algorithm is called the R-IL-PTS, as we can see in Figure 5. better than that of the Ad-PTS method. However, the CC of the R-IL-PTS algorithm in Figure 5 is calculated using the divide-and-conquer approach with the Cooley-Tukey algorithm as well as the subblock arrangement in Table 1, where half of the subblocks in the R-IL-PTS algorithm are needed to compute two R-IFFT functions and

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As mentioned previously, the Ad-PTS algorithm is deemed the most straightforward implementation 251 among the segmentation methods. The PAPR reduction capability of the Ad-PTS method is better than that of the 252 IL-PTS but worse than that of the PR-PTS. In this section, the R-PTS algorithm is utilised with the Ad-PTS (R-times complex multiplications. Accordingly, the number of the addition and multiplication complexities of the R-

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In this study, we classify the PR-PTS as the best partitioning scheme among the ordinary segmentation

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The PAPR reduction performance of the standard and enhanced algorithms is analysed. In terms of the 284 parameters utilised in the simulation, the subblock number V is 4, the subcarrier numbers N are 128 and 256, the 285 oversampling factor L equals 4 and the number of the different phase coefficient vectors W is 4. The CCDF is 286 employed to evaluate the PAPR pattern of the input symbols, and 16-QAM is adopted for constellation mapping.

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Firstly, simulation is conducted to evaluate the three ordinary segmentation schemes, as shown in Figures 8 and   288 9. In case the number of subcarriers is 128, the PAPR value of the PR-PTS is 7.11 dB, that of the IL-PTS is 8.24 291 dB and 11.07 dB, respectively, as shown in Figure 9. As a result, the PR-PTS algorithm is the best segmentation 292 scheme, whereas the Ad-PTS algorithm demonstrates a lower reduction performance compared with the PR-PTS.

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By contrast, the IL-PTS algorithm is the worst segmentation scheme in terms of PAPR reduction efficiency.

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By 0.28 dB. Meanwhile, the R-IL-PTS and Ad-PTS achieve the same PAPR performance at 8.24 dB, as 303 demonstrated in Figure 11. Therefore, the PAPR reduction capacity of the proposed method, that is, the R-IL-

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PTS, is better than that of the IL-PTS and the same as that of the Ad-PTS. proposed and corresponding traditional schemes can be expressed as [26] in Eq. (32) below. 338

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The results of the simulation indicate that the enhanced schemes, that is, R-IL-PTS and R-Ad-PTS, can accomplish mathematical calculation model states that the CC level of the R-IL-PTS is higher than that of the IL-PTS, whereas 363 the number of the process complexity for the R-Ad-PTS algorithm is lower than that for the Ad-PTS. However, the R-PR-PTS approach and PR-PTS scheme demonstrate the same PAPR reduction efficiency and CC level.