非同調通訊位元分散編碼調變系統之應用與設計

位元分散編碼調變系統是由通道編碼器、分散器及調變星座映射器所組合而成。透過位元分散編調變之迭代解碼系統可以增進其系統效能，但必須運作在完美的同步機制下如相位、頻率偏差都已完整估計及補償才會得到良好的系統效能，因此要克服位元分散編碼調變之迭代解碼系統運作於未知相位資訊下是一個很大的挑戰任務。在此篇論文裡我們將探討非同調位元分散編碼調變在未使用任何前導訊號協助估計下克服未知相位的問題。在第一個非同調位元分散編碼調變設計中，我們考慮在粗略估計頻率偏差及相位同步未啟用的通訊環境下執行非同調通訊系統。其非同調通訊系統傳送端是由通道編碼器、分散器、相位星座映射器及差分編碼器所組合而成。在非同調通訊系統接收端部分透過擴展籬柵的設計讓擴展籬柵的設計不只表示其差分編碼的路徑也同時呈現差分編碼可能的相位變化路徑，藉由擴展籬柵的設計同時解決頻率偏差與相位雜訊對於系統效能影響。在第二個非同調位元分散編碼調變設計中，我們探討 16/64角度差分正交幅度調變設計應用在頻率偏差的情況下，我們結合四次方演算法與泰勒內差演算法來克服頻率偏差對於系統效能影響。

關鍵字

位元分散編調變之迭代解碼；差分編碼；非同調通訊；相位模糊；四次方演算法；頻率偏差估計

並列摘要

Bit-interleaved coded modulation (BICM), is a coded modulation system constructed by serially concatenating a channel encoder, an interleaver and a symbol mapper. BICM has the structure of the serial concatenated turbo code which can be decoded in an iterative way using message passing. The impressive performance of BICM-ID implicitly assumes perfect synchronization, i.e., the carrier phase, frequency offset can be recovered accurately before data detection. To overcome the unknown carrier phase for BICM-ID systems is yet a very challenging task since the receiver usually operates at extremely low SNR values. In this thesis, we study BICM system for noncoherent communication without pilots which can overcome the unknown carrier phase. For the first design, we consider a noncoherent communication system that can be used in the communication environment in which the frequency estimation is only roughly obtained and the phase synchronization is not employed. The transmitter side has the serial turbo coding structure composed of a convolutional encoder followed by an interleaver, an MPSK signal mapper and a differential modulator. At the receiver side an expanded trellis is employed to represent not only the possible code paths but also the paths resultant from the possible phase variations due to the frequency offset and the phase noise. For the second design, we study a new two/three-level differentially encoded 16/64QAM (TD16/64QAM) design which is suitable for tackling the CFO problem. This new TD16/64QAM is superior to the previously known TD16/64QAM in the bit-interleaved coded modulation (BICM) system corrupted by CFO. For overcoming the carrier frequency problem, we also address the problem of carrier frequency offset estimation for the BICM using TD QAM, in which the symbol phase can be roughly estimated by the $4th$ power method without pilots and can be more correctly estimated by the Taylor series algorithm.

並列關鍵字

BICM-ID ； Differential modulation ； noncoherent communications ； phase ambiguity ； 4th power algorithm ； frequency offset estimation

參考文獻

[1] G. Caire, G. Tarico, E. Bigieri , “Bit-interleaved coded modulation,” IEEE Trans.Inform. Theory, vol. 44, no. 3, pp. 927-946, May 1998.

[2] E. Zehavi, “8-PSK Trellis codes for Rayleigh channel,” IEEE Trans. Commun.,vol. 40, no. 5, pp. 873-884, May 1992.

[3] G. Montorsi, S. Benedetto, D. Divsalar and F. Pollara “Serial concatenation of interleaved code: Performance analysis, design , and iterative decoding,” IEEE

Trans. Inform. Theory., vol. 44, no. 3, pp. 909-926, May. 1998.

[4] K.R. Narayanan, and G. Stuber “A serial concatenation approach to iterative demodulation and decoding,” IEEE Trans. Commun. Theory., vol. 47, no. 7, pp. 956-961, June. 1999.

國際替代計量

非同調通訊位元分散編碼調變系統之應用與設計

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