ITR/SI: Wireless Transmission Optimization for Bursty Data Traffic

ITR/SI：突发数据流量的无线传输优化

• 批准号: 0111818
• 负责人: Rohit Negi
• 金额: $ 30.57万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-10-01 至 2004-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0111818&HistoricalAwards=false
• 关键词: ITR; SI; Wireless; Transmission; Optimization

The wireless channel is expected to play as dominant a role as the wired internet, in providing seamless information 'super-highway'. In the future, wireless data traffic will be increasingly dominated by a variety of multimedia, such as real-time video, email, web downloads, as opposed to voice transmission. "Tether-free communication and networking', as envisioned by the Information Technology Research program, requires intensive research into handling the transmission of multimedia over the wireless channel. Various multimedia have very different traffic characteristics than voice, being characterized by different delay constraints and burstiness. Handling bursty data has been addressed primarily in the networking communit. The community has focussed on the relationship among the traffic delay constraint, the packet loss rate (which is assumed to be the packet drop rate), and the channel capacity, captured by measures such as "Effective bandwidth'. Networking problems in wired (fiber, copper, etc.) media have been successfully solved by this approach, because this channel is inherently a low-error channel. However, the networking community has by and large ignored the fact that there is a very real, non-idea physical channel on which this data is carried. Therefore, the migration of these approaches to the wireless medium meets a significant obstacle- the fact that the wireless channel is inherently a very noisy, non-robust channel. Thus for wireless channels, it is important to consider the effect on packet loss of both, burstiness and channel errors. Researchers have been approaching the issue of considering both these effects in (the PI believes) an ad hoc manner. This proposal intends to approach the issue in a systematic and logical manner. Specifically, the PI proposes to introduce a joint measure of burstiness and channel condition, and use the measure to solve the key problem of allocating scarce resources among competing users of a wireless system. The proposed joint approach is a fundamental change in paradigm, since it attempts to synthesize ideas from the Networking and Communication Theory communities. The reason why source burstiness as well as channel errors (due to noise, fading, etc.) affect the standard notions of channel capacity, is due to the requirement of finite delay in the data communication. The PI has therefore developed an initial set of measures (details in the full proposal) that relate the delay and packet loss. The measure is based on the random coding error exponent approach, developed in an information theoretic setting. To reduce the packet drop probability, the wireless transmitter must transmit at as high a data rate as possible. But a high rate of transmission would imply a high packet error probability on the wireless channel, due to transmission errors. The measure developed by the PI attempts to capture this trade-off. Preliminary analysis indicates that using this measure indeed offers a substantial benefit (in terms of designing an optimum system) for bursty traffic transmission over fading wireless channels. The first step in the current research would be to refine the developed joint measure. This would involve using more sophisticated source traffic models, more sophisticated fading channel models, and practical channel coding schemes. The developed measure will then be used to design optimal or robust schemes (as the need may be) to allocate wireless resources to competing streams of data traffic. This will involve developing scheduling flow control algorithms, and the associated adaptive channel coding schemes, using the joint measure. In summary, this research will introduce a fundamentally new paradigm for transmission optimization of bursty data traffic over wireless channels, and then demonstrate the usefulness of the new paradigm in practical situations.

无线信道预计将在提供无缝信息“超级高速公路”方面发挥与有线互联网一样的主导作用。 未来，无线数据流量将越来越多地以各种多媒体为主，例如实时视频、电子邮件、网络下载，而不是语音传输。 正如信息技术研究计划所设想的那样，“无线通信和网络”需要对处理无线信道上的多媒体传输进行深入研究。各种多媒体具有与语音截然不同的流量特性，其特点是不同的延迟约束和突发性处理突发数据主要是在网络社区中解决的，重点是通过测量捕获的流量延迟约束、丢包率（假设为丢包率）和信道容量之间的关系。例如“有效带宽”。有线（光纤、铜线等）介质中的网络问题已通过这种方法成功解决，因为该通道本质上是低错误通道。 然而，网络社区基本上忽略了这样一个事实：存在一个非常真实的、非想法的物理通道来承载这些数据。 因此，这些方法向无线介质的迁移遇到了一个重大障碍——无线信道本质上是一个噪声很大、不鲁棒的信道。 因此，对于无线信道，重要的是要考虑突发性和信道错误对数据包丢失的影响。 研究人员一直在以（PI 认为）临时的方式来考虑这两种影响。 该提案旨在以系统和逻辑的方式处理该问题。 具体来说，PI建议引入突发性和信道条件的联合测量，并使用该测量来解决在无线系统的竞争用户之间分配稀缺资源的关键问题。 所提出的联合方法是范式的根本性改变，因为它试图综合网络和通信理论界的想法。 源突发性以及信道错误（由于噪声、衰落等）影响信道容量的标准概念的原因是由于数据通信中有限延迟的要求。 因此，PI 制定了一套与延迟和数据包丢失相关的初始措施（完整提案中的详细信息）。 该测量基于在信息论背景下开发的随机编码误差指数方法。 为了降低丢包概率，无线发射器必须以尽可能高的数据速率进行传输。 但由于传输错误，高传输速率意味着无线信道上的高数据包错误概率。 PI 制定的措施试图捕捉这种权衡。 初步分析表明，使用这种措施确实为衰落无线信道上的突发流量传输提供了实质性的好处（就设计最佳系统而言）。 当前研究的第一步是完善已制定的联合措施。 这将涉及使用更复杂的源业务模型、更复杂的衰落信道模型和实用的信道编码方案。 然后，所开发的措施将用于设计最佳或稳健的方案（根据需要），以将无线资源分配给竞争的数据流量流。 这将涉及使用联合测量来开发调度流控制算法以及相关的自适应信道编码方案。 总之，本研究将介绍一种全新的范式，用于无线信道上突发数据流量的传输优化，然后证明该新范式在实际情况中的有用性。