無線網路編碼系統中的訊號偵測

Abstract

近來實體層（無線）網路編碼因為可提高了吞吐量而引起不少研究者的興趣。在無線傳輸環境中，接收器收到的訊號常常是來自不同來源的信號和雜訊的疊加。相較於傳統接收器試圖估測其中個別的信號，在編碼網路的中繼接收機只需要估計訊號疊加之後的編碼輸出。舉例來說，假設兩個訊號波型同時被中繼接收機收到，它只要估計這兩個信號的和或差。 本篇論文主要目的是在不需要訊號源相位同步的前提下，研究當中繼接收機所收到的無線信號為二元頻率鍵移調變時的訊號檢測。首先在時間同步的情況下推導出最佳的接收機和近似架構及其錯誤率表現。接著延伸討論在固定和隨機時間偏移時如何檢測兩個信號的編碼和。我們的分析有助於瞭解實體層網路編碼在什麼樣的條件下方可提升系統吞吐量。

Physical layer network coding (PNC) has drew much attention due to its potential of bringing about significant throughput enhancement. In a wireless environment, a received signal is often resulted from the superposition of the signals and noises from various sources. Instead of detecting one or more signal, the responsibility of a relay receiver in a wireless network-coded system is to estimate the algebraic sum of the (two) incoming binary waveforms. The aim of this thesis is to solve the above signal detection problem when binary frequency-shift-keying (BFSK) modulation is used. We first derive the detector structure in a network with perfect timing synchronization and analyze the resulting bit error rate performance. We then consider the scenarios when either a fixed or a random timing offset is present. The performance analysis shows that the network throughput can indeed be improved through PNC if proper conditions are met.