在本論文中，我們針對在系統架構雙用戶MISO廣播通道(Two-user MISO broadcast channel)中結合延遲傳送端通道資訊(Delayed CSIT)去處理不平衡接收端雜訊比(Unequal received SNRs)的問題，在此系統中，我們使用了三階段重傳機制(Three-phase retransmission)搭配傳送端具延遲的通道資訊，在第一(Phase I)和第二階段(Phase II)中，傳送端分別廣播了用戶一和用戶二要的資訊，但因為廣播通道(Broadcast channel)的關係，用戶端皆會在這兩個階段收到對他有用和沒有用的訊息，並在估測通道資訊(Channel state information)後回傳給傳送端，在第三階段(Phase III)時，傳送端會將這兩個誤送的訊息(Mis-sent signals)加起來重送給兩個用戶，收到重送訊息(Retransmitted signal)後，兩用戶皆扣掉在前兩個階段因為廣播通道誤送且沒有用的訊息後，可以拿到自己有用但因為廣播通道誤送給對方的訊息，並使這誤送給對方的訊息成為解出訊息的旁資訊(Side Information)。由於非對稱通道的關係，我們提出在第三階段使用了逐次精煉方法(Successive refinement)編碼重送訊息成共同索引(Common index)和精鍊索引(Refinement index)，使擁有較好通道的用戶(Stronger receiver)執行連續干擾消除(Successive interference cancellation)並拿到這兩個索引資訊，可以得到比因為通道較差而只能拿到共同索引這一個資訊的用戶(Weaker receiver)得到較好的解碼，也就是較低的失真(MSE, distortion)。不過使用逐次精鍊編碼和連續干擾消除會個別帶來均方誤差選擇(MSE selection)和能量分配(Power allocation)的問題。模擬結果會顯示出使用我們提出的方法(Proposed compression)會比傳統的壓縮方法(Conventional compression)達到更好的總傳輸量(Sum-rate)。

In this thesis, we focus on the problem of unequal received SNR to the system of two-user multiple-input single-output (MISO) complex Gaussian broadcast channel (BC) at fast Rayleigh fading scenario. In the system, we apply a signaling strategy with cooperating delayed knowledge of channel state information at transmitter (CSIT). In Phase I and Phase II, the transmitter broadcasts messages intended for user 1 and user 2 respectively. The receivers save those received messages without decoding them and send the CSI back to the base station (BS). During each of these phases, the transmitter would mis-send the messages to the unintended receivers because of the BC. In Phase III, the transmitter will retransmit a signal of common interest for receivers utilized linear combination of previous mis-sent signals and delayed CSIT to the receivers, and help receivers decode the messages. To deal with the unequal received SNR, the transmitter quantize the retransmitted signal using successive refinement (SR) into common index and refinement index in Phase III. The stronger receiver which has a better channel can obtain two indexes with performing successive interference cancellation (SIC), and the weaker receiver only obtain the common index. Thus, the stronger receiver can have better reconstruction in quantized signals with lower MSE distortion than weaker receiver. But applying SR and SIC would cause the problems of choosing proper power allocation and MSE distortions. Simulation results show that our proposed compression can achieve higher sum-rate than conventional compression.

[1] A. Vahid, M. A. Maddah-Ali, and A. S. Avestimehr, "Approximate capacity of the two-user MISO broadcast channel with delayed CSIT," Communication, Control, and Computing (Allerton), 2013 51st Annual Allerton Conference on, pp. 1136-1143, 2013.
[2] W. Nam, S. Chung, and Y. H. Lee, "Capacity of the Gaussian two-way relay channel to within 1/2 bit," Information Theory, IEEE Transactions on, vol. 56, pp. 5488-5494, 2010.
[3] A. Sezgin, A. S. Avestimehr, M. A. Khajehnejad, and B. Hassibi, "Divide-and-Conquer: Approaching the capacity of the two-pair bidirectional Gaussian relay network," Information Theory, IEEE Transactions on, vol. 58, pp. 2434-2454, 2012.
[4] M. A. Maddah-Ali and D. Tse, "Completely stale transmitter channel state information is still very useful," Information Theory, IEEE Transactions on, vol. 58, no. 7, pp. 4418-4431, 2012.
[5] S. Cheng and Z. Xiong, "Successive refinement for the Wyner-Ziv problem and layered code design," Signal Processing, IEEE Transactions on, vol. 53, no. 8.
[6] D. Tse and P. Viswanath, Fundamentals of Wireless Communications. Cambridge University Press, 2004.
[7] S. C. Lin and I. H. Wang, "On two-pair two-way relay channel with an intermittently available relay," Information Theory (ISIT), IEEE International Symposium on, pp. 1901-1905, 2015.
[8] E. T. Ar and I. E. Telatar, "Capacity of multi-antenna Gaussian channels," European Transactions on Telecommunications, vol. 10, pp. 585-595, 1999.
[9] A. E. Gamal and Y.-H. Kim, Network Information Theory. Cambridge University Press, 2012.