用於Hybrid ARQ之資料傳輸損害估計

Payload Damage Estimation for Hybrid ARQ

王偉震(Wei-Chen Wang)

指導教授 ： 許大山

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.03334

摘要

混合自動重發請求是一個在缺乏通道狀態資訊下重要的傳輸技巧，當重傳封包收到後，相對於簡單自動重發請求，混合自動重發請求將所有收到的傳輸封包用來共同決定一般根本的封包。這使得發送器更積極地選擇傳輸速率，直覺上，發送器需要投入在重傳封包以修補先前錯誤傳輸的封包所付出的資源，取決於先前傳輸封包所受到的損害。如果資料傳輸損害資訊可以被發送器所得知，將得以顯著地改善重傳的效率，相對於典型的混合自動重發請求模式，一個可知資料傳輸損害資訊的混合自動重發請求傳送機制需要在接收器的損害估計與描述，以及對應的資源分配決策模式用於發送器。
在這篇碩士論文中，我們研究接收器如何估計錯誤封包所遭受的損害以及其效能。首先，為了達到估計損害的終極效能，我們直接從收到的封包本身來估計損害。藉由輔助的信號和收到的封包被用在估計通道狀態的過程中，我們在本篇論文中顯示，基本上這樣的方法無法達到最佳程度的損害估計。接下來，我們研究如何從收到的訊號本身直接估計封包所受到的損害，我們最主要的方法是仔細地檢查收到訊號鄰近的幾何空間來評價潛在的損害，收到訊號的鄰近訊號空間可以藉由多輸出的解碼器像是列表解碼器來估計。為了說明這樣的想法可以在實際上運用，我們將簡單但等效的損害估計用於渦輪碼編碼之正交頻分複用技術，通過頻率選擇性衰減的通道。我們可以計算出收到訊號的等效最小距離，將此結果用來協助設計重傳機制，我們也討論了列舉解碼器的輸出型態於剩餘論文中。

關鍵字

混合自動重發請求 ； 資料傳輸損害估計 ； 通道狀態資訊 ； 多輸出解碼器 ； 頻率選擇性衰減通道 ； 多輸出解碼器

並列摘要

Hybrid automatic retransmission request (HARQ) is an important technique for communications without CSI. When the retransmission arrives, as opposed to simple ARQ, in HARQ all the received transmissions for a payload are used together to determine the common underlying payload. This could allow the transmitter to be more aggressive in its selection of the transmission rate. Intuitively, the amount of resources that a transmitter needs to invest in a retransmission to repair a previously failed transmission depends on how severely the prior transmission is damaged. If the payload damage information (PDI) can be made available at the transmitter, it could signi‾cantly improve the effciency of retransmission. Compared to a typical HARQ scheme, a PDI-available HARQ transmission scheme requires the estimation and description of damage at the receiver and a corresponding resource allocation determination scheme at the transmitter. In this thesis, we investigate the problem of how and how well a receiver can estimate the damage suffered by a failed payload. First, we will show that in order to achieve the ultimate performance in damage estimation, one must estimate damage from the received signal itself. Auxiliary signals and the received payload can be used in the process of channel state estimation. As will be shown in this paper, fundamentally this type of approach cannot reach the optimal level of damage estimation. Next, we look at how the payload damage is to be estimated directly from the received signal. Our main approach is to carefully examine the geometrical space around the received signal to assess potential damage. The constellations near the received signal can be estimated using a multiple-output decoder such as a list decoder. To illustrate how the idea can be applied in practice, we introduce a simple yet effective damage estimator for an convolutionally-coded OFDM link over a frequency selective medium. We can compute the effective minimum distance of the received signal and apply this result to assist in designing retransmission mechanism. We also discuss the output patterns of list decoder in the rest of this thesis.

並列關鍵字

hybrid ARQ ； payload damage estimation ； channel state information ； frequency selective fading channel ； multi-output decoder

參考文獻

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