CDMA/HMD (Hierarchical Multiuser Diversity) Access Schemes for Multimedia Wireless Networks

本计画旨在发展一套多使用者分集驱动的封包排程与局部路由演算法，并获得多媒体无线系统中的一些基本原则。特别是，分层多用户分集（HMD）驱动的多媒体业务的下行链路和上行链路接入方案的问题进行了研究。与HMD驱动的下行链路接入方案相关的目标是设计用于下行链路的高效分组传输方案，利用多用户无线系统中的多用户分集增益。具体地，该提议提出了这样的HMD方案，其中每个用户可以选择直接传输模式或中继传输模式。将时延容忍度视为网络资源，分别针对单小区环境和蜂窝网络，研究了HMD驱动的直接传输和中继传输调度。此外，本地化路由算法将开发慢衰落信道和快衰落信道，由于移动性。在与基于码分多址（CDMA/HMD）的上行链路接入方案有关的项目部分中，该项目将包括接入方案的研究，该接入方案明确地考虑到不同多媒体业务的延迟约束，特别关注上行链路。由于上行链路是一个多址信道，多用户分集将在CDMA的背景下进行探讨。特别地，将基于跨用户的信道条件来优化同时传输的数量。该项目还将解决与缓冲、抖动、公平性和切换到新中继时可能出现的损失相关的关键问题。最后，研究了HMD和CDMA之间的折衷，旨在发展一种混合方案，在获得多用户分集增益的同时保证用户的最小吞吐量要求。

This project aims at developing a suite of multiuser diversity driven algorithms for packet scheduling and localized routing, and to obtain some overriding principles in multimedia wireless systems. In particular, the issues of hierarchical multiuser diversity (HMD) driven downlink and uplink access schemes for multimedia traffic will be studied. The objective related to HMD driven downlink access schemes is to devise efficient packet transmission schemes for the downlink, exploiting multiuser diversity gain in a multiuser wireless system. Specifically, the proposal addresses such an HMD scheme in which each user can choose either a direct transmission mode or a relay transmission mode. Treating delay tolerance as a network resource, the HMD-driven scheduling for both direct trans-mission and relay transmission is then explored for both single-cell setting and cellular networks. Also the localized routing algorithms will be developed for both slowly fading channels and fast fading channels, due to mobility. In the part of the project related to based on code division multiple access (CDMA/HMD) uplink access schemes, the pro-ject will include studies of access schemes taking into account explicitly the delay con-straints of different multimedia traffic, with particular focus on the uplink. Since the up-link is a multi-access channel, the multiuser diversity will be explored in the context of CDMA. In particular, the number of simultaneous transmissions will be optimized, based on the channel conditions across the users. The project will also address the critical issues related to the buffering, jitter, fairness and possible loss due to switching to a new relay. Finally, the trade-off between HMD and CDMA will be studied, with the aim at develop-ing a hybrid scheme that achieves multiuser diversity gain and guarantee the user's minimal throughput requirement as the same time.