基於幾何方法欠定多輸入多輸出系統之高效率解碼演算法

Abstract

在多輸入多輸出系統中，高效率且低功率消耗之接收機的設計為關鍵議題之ㄧ。在多輸入多輸出系統中，球型解碼器是能有效提供最大似然的接收器。然而，典型球型解碼器無法運用在傳送天線個數大於接收天線個數的欠定系統中。針對此類系統，通用球型解碼被提出，但它的解碼複雜度隨著天線個數差的增加而呈現指數增加。在本論文中，針對此類欠定系統，吾人提出具有低解碼複雜度的解碼器。該解碼器包含了兩個步驟：1.藉由所提出的高效率的平面候選點搜尋器將所有所需的候選點一一找出。2.針對這些候選點集合進行平面交集的動作並配合動態半徑調整機制來快速地找出該問題的解。吾人亦提出一可與所提出解碼器結合之通道矩陣行向量的排序策略，進而提供低運算需求及近似最大似然搜尋的解碼性能。模擬結果顯示吾人提出方法的有效性。

The design of high-performance and low-power consumption receiver is one of the key issues of MIMO systems. The sphere decoding algorithm (SDA) is an effective detector for MIMO systems. However, typical SDA fail to work in underdetermined MIMO systems where the number of transmit antennas is larger than the number of receive antennas. The generalized sphere decoder (GSD) had been proposed for underdetermined MIMO systems. However, its decoding complexity is exponentially increasing with the antenna number difference. In this thesis, we propose a decoder for underdetermined MIMO systems with low decoding complexity. The proposed decoder consists of two stages: 1. Obtaining all valid candidate points efficiently by slab decoder. 2. Finding the optimal solution by conducting the intersectional operations with dynamic radius adaptation to the candidate set obtained from Stage 1. We also propose a reordering strategy that can be incorporated into the proposed decoding algorithm to provide a lower computational complexity and near-ML decoding performance for underdetermined MIMO systems. Simulations confirm the effectiveness of the proposed methods.