應用於多基地台合作MIMO-OFDM系統之渦輪等化

Abstract

在蜂巢式無線系統中，細胞邊緣的手機使用者常常會受到從其他細胞來的訊號干擾，因此LTE-A系統提出協調式多點傳送與接收(coordinated multipoint process; CoMP)之技術被來解決此問題，在CoMP中，參與協調的手機使用者與基地台的天線會形成一個大型的多輸入多輸出(multiple-input-multiple-output; MIMO)系統，經由協調我們可以避免干擾或可以把干擾成訊號估計。在本論文中，我們研究MIMO-OFDM系統下場域間CoMP之渦輪等化，在我們的方法中，接收機包含一個MIMO等化器跟一個通道解碼器，隨著等化器與解碼器間的遞迴次數增加，偵測的效能會逐漸的提高，此渦輪等化在遞迴期間可以藉由從其它的基地台資訊交換更進一步被提高。然而，因為基地台是被設置於不同的場域，資料交換變成一個很有挑戰性的問題，本論文提出數種交換策略，使得我們可以在效能與交換資料量上做一個適當的權衡。在很多情況下，我們能用有限的資料交換量來達到很好的效能提升。

In cellular systems, the users in cell edge often suffer from the interference from interfering cells. In LTE-A, coordinated multipoint processing(CoMP) has been proposed to solve the problem. In CoMP, antennas between involved users and basestations can form a large multiple-input-multiple-output (MIMO) system such that interference can be either avoided or estimated as desired signals via joint processing. In the thesis, we study turbo equalization for MIMO-OFDM systems with inter-site CoMP. In our approach, the receiver consists of an MIMO equalizer and a channel decoder. With the iteration between the equalizer and the decoder, the detection performance can be progressively enhanced. The performance of the turbo equalization can be further improved by exchanging data with other base stations during its iteration. However, since base stations are located in different sites, data exchange becomes a challenging problem. We then propose several exchanging strategies such that the performance and exchanging data can have a good trade-off. In many cases, we can have a great performance enhancement while the amount of data exchanged is limited.