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

该项目的目的是开发一套多用户分集驱动的分组调度和局部路由算法，并在多媒体无线系统中获得一些覆盖原则。特别是，将研究分层多用户分集(HMD)驱动的多媒体业务的下行链路和上行链路接入方案。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。具体地说，该提案针对这样的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。将时延容限作为一种网络资源，对HMD驱动的直接传输和中继传输调度进行了研究，包括单小区设置和蜂窝网络。此外，由于移动性，还将针对慢衰落信道和快衰落信道开发局部化的路由算法。在与基于码分多址(CDMA/HMD)上行链路接入方案相关的项目部分，该项目将包括明确考虑不同多媒体业务的时延约束的接入方案的研究，尤其是上行链路。由于上行链路是多址信道，因此将在码分多址的背景下探讨多用户分集。具体而言，将基于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、公平性和切换到新的继电器可能造成的损失相关的关键问题。最后，对HMD和CDMA的权衡进行了研究，目的是开发一种混合方案，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.