ITR: Cross-Layer Optimization For 4G Wireless Networks: Heavy-Tailed Traffic, Multiuser Channels, and Pseudocells

这个项目涉及无线网络理论和实践的一些基本方面。 一个综合的方法，combiningphysical层的创新与新的协议介质访问控制和调度，同时考虑到应用程序的要求和传输协议的动态，是用来解决所确定的研究问题。 两个主要的研究重点被认为是。 在第一个研究重点中，"伪蜂窝“无线网络的概念，它联合收割机结合了蜂窝和自组织网络的最佳特征，被认为是即插即用的第四代（4G）无线网络的范例。 这种灵活的架构对于在紧急情况下快速建立无线网络显然是至关重要的，在紧急情况下，固定的或者甚至可能是移动的基站被部署在方便的（但未优化的）站点，以服务于缓慢移动和快速移动的用户。 然而，它也是我们实现无线链路速度量子跳跃的愿景的关键因素，通过超越当前1-2 GHz的蜂窝频段，达到数十GHz频段的大带宽。 这样的频带中的路径损耗很高，一方面迫使使用密集的基站网络，另一方面实现更积极的频率重用。 研究的重点是支持一个组合的用户移动性，以及实时和非实时应用的组合，在一个分组的伪蜂窝基础设施。 这种设置与传统蜂窝网络的不同之处在于，小区大小很小，并且小区可能具有大量重叠。 它与无线局域网（WLAN）的不同之处在于，它允许快速移动的用户，尽管小区大小很小。 代替传统的分层结构（即，用于快速移动用户的大小区，覆盖在用于慢速移动用户的小小区上）来处理移动范围，考虑将MIMO和基于预留的媒体接入控制相结合的以移动为中心的方法以允许灵活的部署。要研究的一个新颖的思想是支持保留信道上的优先级，以便允许例如具有正在进行的实时呼叫的高度移动的用户在进入新的伪小区时快速保留资源，从而隐含地实现越区切换。另一个重要的问题是收发器优化的预留通道，这需要解决新的问题，在多用户communications.The第二个研究重点是由著名的观察，互联网流量有一个重尾分布，这通常要求更保守的资源配置比传统的马尔可夫交通模型的动机。 由于过度配置是没有吸引力的资源受限的无线环境中，所考虑的方法是采用一种新的服务质量（QoS）的框架，允许foraggressive资源利用率，通过服务的大部分的thetactions（这是短）迅速，并惩罚的一小部分长事务，有助于沉重的尾巴。实现这一目标的调度学科与流行的循环赛或公平竞争者有很大的不同，并且在三十多年前的竞争理论文献中被考虑过。 这些结果的影响重尾Internettraffic探索第一次（尽我们所知）在这个项目中。 调度策略扩展到一个共享的无线信道，公平性是权衡对systemefficiency，与后者规定，用户看到最好的信道是那些应该得到链路接入。 权衡预计将偏向于效率，以有效地减少拖尾流量。 调度和TCP连接（TCP是Internet数据传输协议，大多数事务都在其上运行）的动态之间的相互作用进行了探索，请记住，由于重复超时和速率削减，缺乏网络资源的TCP连接可能会被锁定在网络之外。 最后，调度对移动性的依赖性进行了探讨，与高度mobileusers（谁有一个较小的机会获得访问的链接在他们逗留期间，在一个给定的伪小区）的优先级分配的概念，同时保持整体的QoS和公平性。 我们开发的调度方法高度重视整体系统效率，因此非常适合于统一费率定价，这可以说是一种有效的机制，促进无线数据网络的使用增长。

This project addresses some fundamental aspects of the theory and practice of wireless networking. An integrated approach, combiningphysical layer innovations with new protocols for medium access control and scheduling, while accounting for application requirements and transport protocol dynamics, is employed for solving the research problems that are identified. Two major research thrusts are considered. In the first research thrust, the concept of ``pseudocellular'' wireless networks, which combine the best features of cellular and ad hoc networks, is considered as a paradigm for plug-and-play fourth generation (4G) wireless networks. Such a flexible architecture is clearly critical for quick set-up of wireless networks in emergency situations, in which stationary, or perhaps even mobile, base stations are deployed at convenient (but not optimized)sites to serve both slow-moving and fast-moving users. However, it is also a key ingredient of our vision of achieving a quantum jump in wireless link speeds, by going beyond the current cellular frequency bands of 1-2 GHz to the large bandwidths available in frequency bands in the 10s of GHz. The path loss in such bands is high, forcing the use of a dense network of base stations on the one hand, and enabling more aggressive frequency reuse on the other. The focus of the research is to support a mix of user mobilities, and a mix of real-time and non real-time applications, over a packetized pseudocellular infrastructure. This setting differs from conventional cellular networks, in that the cell sizes are small, and cells may have substantial overlap. It differs from wireless Local Area Networks (WLANs), in that it allows for rapidly mobile users despite the small cell sizes. Instead of a conventional hierarchical structure (i.e., large cells for fast-moving users, overlaid on small cells for slow-moving users) to deal with a range of mobility, a mobile-centric approach, which combines handoffs and reservation-based medium access control, is considered to allow for flexible deployment. A novel idea to be investigated is the support of priorities on the reservation channel, so as to allow, for example, highly mobile users with real-time calls in progress to rapidly reserve resources when entering a new pseudocell, thus implicitly achieving a handoff. Another important issue is transceiver optimization of the reservation channel, which requires solution of new problems in multiuser communications.The second research thrust is motivated by the well-known observation that Internet traffic has a heavy-tailed distribution, which typically calls for more conservative resource provisioning than for traditional Markovian traffic models. Since overprovisioning is unattractive in resource-constrained wireless environment, the approach considered is toemploy a new Quality of Service (QoS) framework that allows foraggressive resource utilization, by serving the bulk of thetransactions (which are short) rapidly, and penalizing the small fraction of long transactions that contribute to the heavy tails. Scheduling disciplines that achieve this goal are very different frompopular round robin or fair queueing schedulers, and were considered in the queueing theory literature more than three decades ago. The implication of these results for heavy-tailed Internettraffic is explored for the first time (to the best of our knowledge) in this project. The scheduling strategy is extended to a shared wireless channel, where fairness is traded off against systemefficiency, with the latter dictating that users seeing the best channels are the ones that should get link access. The tradeoff is expected to be biased towards efficiency in order to supportheavy-tailed traffic effectively. The interaction between scheduling and the dynamics of TCP connections (TCP is the Internet data transport protocol on top of which most transactions run) is explored, keeping in mind that a TCP connection that is starved of network resources can get locked out of the network due to repeated timeouts and rate cutbacks. Finally, the dependence of scheduling on mobility is explored, with the concept of assigning priority to highly mobileusers (who have a smaller chance of getting access to the link during their sojourn in a given pseudocell), while keeping overall QoS and fairness in mind. The scheduling methods we develop place a high importance on overall system efficiency, and are therefore well-suited to flat rate pricing, which is arguably an effective mechanism of promoting usage growth in wireless data networks.