OFDM無線網路之合作通訊---子計畫四：合作式多使用者多輸入多輸出正交分頻多工系統(I)

Abstract

在本子計劃中我們將合作的概念應用於多輸入多輸出正交分頻(MIMO-OFDM) 系統，除 了一般的使用者之間的合作，我們將進一步的考慮基地台之間的合作，希望能藉由基 地台之間的合作能進一步提升系統性能。由於合作的機制大部分需要使用者間通道的 資訊，在第一年工作項目中，我們首先研究通道資訊之回傳機制，由於通道為時變及 估計易有誤差因此需要通道的預測與濾波。另外不同通道特性將影響回傳的資訊量及 通道估計與預測，因此我們也將研究及建立MIMO 通道的通道模型。在第二年的工作項 目中，我們將探討合作式的MIMO-OFDM 之系統特性與性能表現。基於前述合作式通道 估計，我們可對使用者間進行髒污紙張編碼(dirty paper coding); 如此一來不同的 基地台所發射給不同使用者的信號不會互相干擾; 此外，我們將研究合作式波束成型 (cooperative beamforming) 演算法。在第三年的工作中，我們利用通道估計的資訊， 設計合作系統之最佳功率/位元的配置演算法及事前編碼(pre-coding)。我們同時也 考慮合作式多重輸入輸出中繼系統(cooperative MIMO relay system)，研究放大後傳 送(amplify-and-forward)以及解碼後傳送(decode-and-forward)之出相關演算法。

In this sub-project, we consider cooperation in MIMO-OFDM systems. Apart from the cooperation for users, we would further take the cooperation among base-stations into account. We hope in such a way the overall performance can be enhanced further. However, cooperation mechanism is mostly based on the channel information of users. Therefore, in the first year we investigate the channel feedback mechanism, channel prediction, and channel filtering to cope with time-varying channel or the error of channel estimate. Note that channel characteristics will greatly influence the amount of feedback channel data and the mechanisms of channel estimation and prediction. Thus we have to study and built MIMO channel models. For the second year, we will study system performance for cooperative MIMO-OFDM system. Also, we can conduct dirty paper coding for users based on the above cooperative channel estimate. Then, the transmitted signals from distinct base stations to different users will not interfere each other. Furthermore, we will investigate cooperative beamforming algorithm. For the third year, we study using channel estimate to design the algorithm for optimal power/bit allocation and pre-coding. We would also develop the algorithm for cooperative MIMO relay system with amplify-and-forward or decode-and-forward operation.