多重天線系統的容量已被證明大幅超越於傳統的單一天線系統，而用於多重天線系統的通道碼稱為空時(space-time)碼，其中的么正(unitary)空時調變為一種非同調(noncoherent)空時區塊(block)碼，有許多學者投入研究。對於非同調編碼，以往我們已經得到一些相當不錯的研究成果。然而，我們一直使用的多層編碼(multilevel coding)所建構的非同調區塊編碼調變，當區塊短時其錯誤率並不理想。當區塊越短時，如果作同調解碼，其通道估測所需的嚮導(pilot)訊號造成的速率損失(rate loss)就越大，因此短的非同調區塊碼相當重要。本計畫的第一年將研究短非同調區塊碼（包括么正空時調變在內）。在本計畫中，我們不再使用多層編碼，而將用演算法去尋找一群碼字來組成碼，以讓它們具有大的最小非同調距離。可能的作法為從選定的星座圖找碼字，或從給定的最小非同調距離找碼字。從我們對單天線的非同調區塊碼所做的初步結果發現，這樣得到的碼有不錯的最小非同調距離及錯誤率，值得再進一步深入研究。在本計畫的第二年，我們將對第一年所得到的短區塊碼及演算法作進一步的應用，包括適合串接外部(outer)碼的較長非同調區塊碼（包括么正空時調變）、非同調籬柵(trellis)編碼調變及相差編碼(differential encoding)這些方向。我們打算用第一年得到的短碼字擺在籬柵分支(branch)上，去設計或搜尋有籬柵結構的非同調區塊碼和非同調籬柵碼，使整個系統有優良的錯誤效能。另一方面，非同調區塊碼如果可以像相差編碼一樣不用傳第一個訊號（可視為廣義(generalized)相差編碼），可以比傳統相差編碼有更好錯誤率。我們打算修改第一年得到的演算法，去尋找適合廣義相差編碼的短區塊碼（包含空時碼）。It has been shown that the multiple-antenna system has superior capacity to the single-antenna system. Among the channel codes for the multiple transmitter antennas system, which are called space-time codes, unitary space-time modulation which is a kind of noncoherent space-time block codes attracts much attention. We have obtained some satisfactory results of noncoherent coding. However, noncoherent block-coded modulation which is based on multilevel coding has bad error rate if the block is short. Short noncoherent block codes are important since in the case of short blocks, the rate loss caused by the pilot signal for coherent decoding is significant. In the first year of this project, we will study short noncoherent block codes. Instead of using multilevel coding, we will use algorithms to find codewords of a code which has large minimum noncoherent distance. Possible approaches include to find codewords based on the chosen constellation, or based on the given minimum noncoherent distance. According to our initial results, the obtained noncoherent block codes for the single-antenna system have excellent minimum noncoherent distance as well as error rates, so further research on this subject is necessary. In the second year of this project, we will do further applications of the obtained short block codes and algorithms, including longer noncoherent block codes serially concatenated with outer codes, noncoherent trellis coded modulation and differential encoding. We will search for noncoherent block and trellis codes whose symbols of trellis branches are codewords of short block codes obtained in the first year, and modify algorithms to find short noncoherent block codes suitable for generalized differential encoding. 研究期間：10008 ~ 10107
