Collaborative Research: Opportunistic Scheduling for Multimedia Wireless Systems

该合作项目侧重于利用无线环境时变特性的网络级解决方案，以提高系统的整体性能，同时考虑到多媒体无线系统的服务质量（QoS）和公平性。所提出的算法被归类为“机会主义”，因为它们考虑了信道条件（以及每个用户效用的相关定义）。本文将重点开展以下研究活动：具有和不具有明确延迟要求的机会调度以及频域的机会调度。与无明确延迟要求的机会调度相关的目标是开发调度算法，利用无线信道的时变特性来优化不同公平性要求下的网络性能。特别是，将探讨信道估计问题，为此将开发通过随机近似类型的技术来有效跟踪系统参数的快速方法。对于具有明确延迟要求的机会调度，目标将是为语音和视频等实时应用开发调度机制，其目标不仅是根据用户的信道条件和公平性约束来调度用户，而且还基于用户的截止日期。特别地，我们将研究没有单独QoS约束的机会调度问题和具有单独QoS要求的机会调度问题。为此目的，将制定离线最优调度解决办法，为评价其他方案提供基准。另一方面，考虑网络流量统计的在线算法将得到发展，并在实用性上得到验证。最后，与频域机会调度相关的活动将考虑在无线系统中利用时域和频域分集。特别是，将探讨的问题是，目标将是最大化系统性能，其中功率可能是一个明确的约束或惩罚函数。这里将探讨的其他类型的问题将处理在性能约束下最小化传输功率的问题。

This collaborative project focuses on network-level solutions for exploiting the time-varying nature of the wireless environment to increase the overall performance of the system taking into account quality of service (QoS) and fairness for Multimedia Wireless Systems. The proposed algorithms are classified "opportunistic" since they consider channel conditions (and related definitions of per-user utility). The following research activities will be particularly pursued: opportunistic scheduling with and without explicit delay requirements as well as opportunistic scheduling in the frequency domain. The objective related to opportunistic scheduling without explicit delay requirements is to develop scheduling algorithms that exploit the time-varying nature of the wireless channel to optimize network performance under different fairness requirements. In particular, the channel estimation problem will be explored for which fast methodologies to effectively track the system parameters through stochastic approximation types of techniques will be developed. For opportunistic scheduling with explicit delay requirements, the goal will be to develop scheduling mechanisms for real-time applications such as voice and video where the objective is not only to schedule users based on their channel conditions and fairness constraints, but also based on their deadlines. In particular, the problems of opportunistic scheduling without individual QoS constraints and problems of opportunistic scheduling with individual QoS requirements will be studied. For that purpose, the off-line optimal scheduling solutions that provide benchmarks in evaluating other schemes will be developed. On the other hand, the on-line algorithms that take into account network traffic statistics will be developed and proven on practicability. Finally, the activities related to opportunistic scheduling in the frequency domain will consider taking advantage of both time-domain and frequency-domain diversity in wireless systems. In particular, the problems will be explored where the objective will be to maximize the system performance where power could be an explicit constraint or a penalty function. Other types of problems that will be explored here will deal with minimizing the transmitted power subject to performance constraints.