以部份傳輸序列平移改善正交分頻多工訊號峰均比

PAPR Reduction for OFDM Signal by Partial Transmit Sequence Translation

黃敬文(Ching-Wen Huang)

指導教授 ： 李穎

元智大學/電機通訊學院/通訊工程學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00138

摘要

OFDM訊號具有高功率峰均值比(PAPR)的特性。在傳輸端通過放大器時，瞬時功率高的訊號容易進入非線性區，會造成帶內訊號失真和帶外頻譜干擾。因此如何有效降低OFDM訊號的PAPR為一研究主題。線性相位變化法(Linear Phase Variation)的觀念是對頻域子載波區塊訊號序列加上線性相位，其效果等同於對時域部份傳輸訊號序列(Partial Transmit Sequence)做平移，故線性相位變化法又可稱為部份傳輸序列平移(Partial Transmit Translation，PTST)。
線性相位變化法在[Hsi05][LH06]中第一次被提出時，在訊號格式、分區塊方式和性能評估方面結果有限，只對PSK-OFDM訊號進行降PAPR性能模擬，分區塊方式，全部採用adjacent分區。本論文延續線性相位變化法的觀念，做進一步的研究。訊號格式採用PSK-OFDM與QAM-OFDM。分區塊方式包含adjacent、interleaved與pseudo random三種。在性能評估方面，PSK-OFDM與QAM-OFDM訊號在子區塊數目2且相位變化總數為4，各相位變化法在PAPR CCDF為10-3時，PAPR reduction大約2dB。子載波數為8的QPSK-OFDM訊號窮盡測試選取低PAPR序列百分比，最多可達72.27%。錯誤率比較顯示，PTST較PTS具有強健性。整體而言在各項性能評估成果中，PTST表現均為最佳。

關鍵字

部份傳輸序列 ； 正交分頻多工 ； 訊號功率峰均比 ； 線性相位變化法

並列摘要

OFDM signals may possess high peak to average power ratios (PAPR). While transmitting through an amplifier, high instantaneous power signals may enter the nonlinear region and result in in-band signal distortion and out-band interference. PAPR reduction for OFDM signals is therefore an important research topic. The idea using of linear phase variation to reduction PAPR is to apply linear phase shifts to sub-blocks of sub-carriers in the frequency domain. This is equal to translating (cyclic shifting) partial transmit signal sequences in the time domain. In this thesis, linear phase variation is also called partial transmit sequence translation (PTST).
The concept of using linear phase variation for PAPR reduction was first introduced in [Hsi05] [LH06]. The signal modulation, method of sub-blocks splitting, and performance evaluation results are all limited. Only adjacent subcarrier sub-blocks and PSK-OFDM signal are considered in their simulations. This thesis extends the idea of linear phase variation with PSK-OFDM and QAM-OFDM signals. Methods of grouping subcarriers into sub-blocks include adjacent, interleaved, and pseudo-random. In performance evaluation, PSK-OFDM and QAM-OFDM signals are split into two sub-blocks and four linear phase variations are possible. In each case, when PAPR CCDF equals 10-3, the PAPR can be reduced by about 2dB. Exhaustive tests were also conducted for 8-subcarrier QPSK-OFDM signals split into two sub-blocks and optimized over four linear phase variations. Our results show that the percentage of lowest PAPR sequences selected is 72.27%. Symbol error rate comparison shows that PTST is more robust than PTS. In conclusion, PTST performance the best in all our performs evaluation categories.

並列關鍵字

PTS ； PAPR ； OFDM ； PTST

參考文獻

[BFH96] R.W. Bauml, R.F.H. Fischer, J.B. Huber, “Reducing the peak-to-average power ratio of multicarrier modulation by selected mapping,” Electronics Letters, Volume 32, Issue 22, Oct. 24 , 1996 Page(s):2056 – 2057.

[CHL04] Yang Chan Cho, Seung Hee Han, and Jae Hong Lee, “ Selected Mapping Technique with Novel Phase Sequences for PAPR Reduction of an OFDM Signal,” Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th,Volume 7, 26-29 Sept. 2004 Page(s):4781 - 4785 Vol. 7.

[CS99] L. J. Cimini, Jr., N. R. Sollenberger, “Peak-to-average power ratio reduction of an OFDM signal using partial transmit sequences,” Communications, 1999. ICC '99. 1999 IEEE International Conference, Volume 1, 6-10 June 1999 Page(s):511 - 515 vol.1.

[CS00] L. J. Cimini, Jr., N. R. Sollenberger, “Peak-to-average power ratio reduction of an OFDM signal using partial transmit sequences with embedded side information,” Global Telecommunications Conference, 2000. GLOBECOM '00. IEEE ,Volume 2, 27 Nov.-1 Dec. 2000 Page(s):746 - 750 vol.2.

[DJ99] J. A. Davis, J. Jedwab, “Peak-to-mean power control in OFDM, Golay complementary sequenced and Reed-Muller codes,” IEEE Transactions on Information Theory, Volume 45, Issue 7, Nov. 1999 Page(s):2397 – 2417.