稀疏增強通道誤匹配模型族及其於無線異質網路中穩健傳輸之應用

Abstract

由於缺乏精準的通道資訊，干擾通道上的傳輸需要穩健的預編碼(Precoder)，而穩健預編碼的效能通常取決於誤匹配模型的保守程度。習知的確定性誤匹配模型通常過於保守，而隨機性誤匹配模型又在錯誤假設其機率密度函數及參數的情況下易於產生錯誤。為了解決習知確定性誤匹配模型過於保守的問題，本論文提出三種確定性誤匹配模型，分別是結構式誤匹配模型 (SMM)、稀疏增強誤匹配模型(SEMM)以及反式稀疏增強誤匹配模型(SEMMR)。不同於以往的確定性誤匹配模型，本論文所提出的誤匹配模型善加利用通道本身固有的結構性以及稀疏性，使得應用於預編碼上具有相較於傳統秩球型誤匹配模型(NBMM)較佳的傳輸效能。通道本身固有的稀疏性可利用基底擴張模型(BEM)來建模(Model)出通道，其中本論文使用ADR以及Eigenmod作為MIMO通道的基底，並利用DPSS作為時間選擇、頻率選擇及雙選擇SISO通道的基底。另外，本論文同時提出一種應用於雙選擇SISO通道並利用SEMMR的二階段收發機設計。本論文包含優於傳統NBMM預編碼分析及模擬結果。

Transmission over interference channel often relies on the use of robust precoder due to a lack of accurate channel state information, with performance often depending on the conservativeness of the mismatch model. Previously proposed mismatch models either have been deemed too conservative (deterministic models) or are prone to error due to inaccuracy in the probability density function (pdf) and corresponding parameters (stochastic models). Deterministic mismatch models called Structure Mismatch Model (SMM), Sparsity Enhanced Mismatch Model (SEMM), and SEMM - Reverse discrete prolate spheroidal sequence, or SEMMR, are proposed herein in an attempt to alleviate this problem. Different from all previously deterministic models, the proposed models exploit the structure property or the inherent sparse characteristics of interference channels and outperform precoding only incorporating conventional norm ball mismatch model (NBMM). The inherent sparsity in the channel is brought forth by modeling the channel using basis expansion models (BEM), where angular domain representation (ADR) and eigenmode is utilized as basis for modeling multiple input, multiple output (MIMO) non-selective/flat-fading channels and discrete prolate spheroidal sequence (DPSS) is used as a basis for single input, single output time-, frequency-, and doubly-selective fading (DSF) channels. A two-stage robust transceiver design using SEMM - Reverse discrete prolate spheroidal sequence (SEMMR) is also proposed in SISO-DSF channel scenario. Analytical and simulation results are provided to validate the performance gains of the SMM and SEMM precoder, and the SEMMR transceiver over the conventional NBMM precoder.