利用接收分集的分散式多用戶多輸入多輸出網絡

Abstract

多用戶多輸入多輸出是一項正蓬勃發展的技術。利用配置在不同使用者上的天線，多用戶多輸入多輸出技術可以讓多個使用者同時傳送資料。然而，現有的多用戶多輸入多輸出協定設計主要都是針對如何達到更高的多路複用增益，但卻未能有效利用到多用戶多輸入多輸出系統下的分集增益。在這篇論文中，我們提出Multiplex-Diversity Medium Access (MDMA)，一種多用戶多輸入多輸出協定，可以同時達到多路複用增益和接收分集增益。MDMA的設計概念是讓多個競爭的使用者共享空間多工資源，而不是讓其中一個使用者占有所有的空間資源。因此MDMA可以利用配備在不同接收節點上的天線，來獲得接收分集增益，並且同時確保多路複用增益。我們透過在軟體定義無線電上實作MDMA的原型以及模擬一般情況下的MDMA運作，來展示MDMA的吞吐量與接收分集增益。

While MIMO technologies are rapidly adopted in 802.11, mobile devices increasingly have different numbers of antennas. Several multiuser MIMO (MU-MIMO) MAC protocols have recently been proposed to allow multiple nodes to exploit their MIMO capabilities to transmit concurrently. Though those protocols better utilize the available degrees of freedom, they however do not give concurrent streams any receive diversity. This paper introduces Multiplexing-Diversity Medium Access (MDMA), a distributed MU-MIMO MAC protocol that achieves both the multiplexing and receive diversity gains at the same time. Instead of letting a node pair use its full degrees of freedom, MDMA allows as many contending node pairs as possible to transmit concurrently and share all the available degrees of freedom. It hence exploits more antennas equipped at different receiving nodes to provide concurrent streams more receive diversity, without sacrificing the multiplexing gain. We show via both testbed experiments and simulations that MDMA leverages receive diversity and produces a higher throughput than the existing protocol that enables only spatial multiplexing.