寬頻混合波束成型系統下的低複雜度用戶排程演算法

Abstract

本文考慮將一種低複雜度的用戶排程方案應用於寬頻多用戶毫米波系統。由於射頻鏈的高成本，為了減少射頻鏈的數量，全數字化波束成型轉變為混合波束成型，結合了數字波束成型和模擬波束成型。在混合波束成型寬頻系統中，使用OFDM 將整個頻帶切割成多個子載波，並且為所有子載波設計一個共用的模擬預編碼器。很少有文獻討論用戶排程應用在混合波束成型寬頻系統。在以前的論文中使用了最大速率作為排程標準，並根據用戶的傳送速率選擇用戶。但是，這種方法的複雜度太高需要大量的時間，所以我們採用正交投影的方法來選擇用戶。模擬結果表明，所提出的演算法的最大速率可以達到了以前的提出的論文的最大速率，並且複雜度降低了射頻鏈數量的倍數。

This thesis considers applying a low complexity user scheduling scheme to a wideband multi-user millimeter wave (mmWave) system. Due to the high cost of the RF chain, to reduce the number of RF chains, the fully digital beamforming is transformed into hybrid beamforming that combines digital beamforming and analog beamforming. In hybrid beamforming wideband systems, OFDM is used to cut the entire frequency band into multiple sub-carriers, and a common analog precoder is designed for all sub-carriers. Little literature discusses the user scheduling in hybrid beamforming wideband systems. In the previous work, the authors used maximum sum rate as the scheduling criterion and selected users based on their rates. However, the complexity of calculating user rates is too high and takes a lot of time, so we use the orthogonal projection method to select users. The simulation results show that the achieved sum rate of the proposed algorithm can reach that of the previous work, and the complexity is reduced by a multiple of the number of RF chains.