EE Department Seminar

Fall 2010

Tuesday, Nov. 23

10:00am, Rm. 521, Physics Building

Information Theory for Wireless Networks

J. Rockey Luo

Assistant Professor

ECE, Colorado State University

 

       Abstract: Information Theory is the theoretical foundation of digital communication. Its channel coding theory characterizes the “capacity region” of a communication system. If information rate vector is kept within the capacity region, then error probability of message delivery can be taken arbitrarily close to zero. Classical channel coding theory was developed under the fundamental assumptions that users in a communication system can jointly determine their channel codes and information rates, and can communicate continuously over long time duration without unexpected disturbance. In a wireless networking environment, however, when users have bursty short messages that require timely dissemination, joint channel coding often becomes infeasible or impractical.

       In this talk, we introduce a new channel coding theory for time-slotted random multiple access networks, where users cannot jointly design their channel codes. We assume each user individually chooses a set of codes each corresponding to a different rate option. In each time slot, a user chooses a communicate rate, which is the number of data bits encoded in a packet, depending on data availability and the link layer protocol. The rate information is shared neither between the users nor with the receiver. The receiver decodes the messages only when an error probability requirement is satisfied, otherwise the receiver reports a packet collision. We find that, fundamental performance of the system can be characterized by an achievable rate region in the following sense. If the communication rate vector happens to be inside the rate region, the receiver can reliably decode all messages, while if the communication rate vector happens to be outside the rate region, the receiver can reliably detect a collision. Although defined quite differently, we find the rate region equal Shannon information rate region without a convex hull operation.

       Bio: J. Rockey Luo received the Ph.D. degree in Electrical and Computer Engineering from University of Connecticut in 2002. From 2002 to 2006, he was a Research Associate with the Institute for Systems Research (ISR), University of Maryland, College Park. In 2006, he joined the Electrical and Computer Engineering Department of Colorado State University as an Assistant Professor. His current research focuses on cross-layer interactions in wireless communication networks with an emphasis on the bottom layers.

Contact: Prof. Bo Hu, bohu@fudan.edu.cn

The presentation is written in English, but the talk will be given in Chinese.

 

电子工程系学术讲座

2010年秋季

11月23日，星期二

上午10:00, 物理楼521会议室

信息论与无线网络

罗杰  （J. Rockey Luo）

科罗拉多州立大学，电子工程系，助理教授

 

       摘要：信息论是数字通信的理论基础。其中的信道编码理论给出了一个通信系统的“信道容量”。如果通信系统的通信速率在信道容量之内，那么我们可以设计信道编码使得通信的误码率无限接近于零。传统的信道编码理论中有一个本质的假设，那就是通信系统中的用户可以联合设计信道编码以及通信速率，用户也可以长时间在没有意外干扰的情况下持续占用信道。可是，在无线网络环境中，当用户需要及时传送突发产生的短信息时，多用户联合设计信道编码在很多情况下变得不可实现，或者效率低下。

       在这个讲座中，我们介绍一种新的适用于random multiple access通信模式的信道编码理论。Random access通信模式的核心假设就是各个用户之间不能够设计联合编码。我们假设每个用户单独选定一组信道编码，其中每一个编码对应于一个通信速率选项。在一个时间块内，每个用户根据自己的所拥有的数据以及链路层的网络协议来选择一个通信速率，也就是一个数据包中所编入的数据比特率。用户的通信速率信息既不互相共享，也不事先通知接收机。接收机只有在误码率能够达到预先设定的要求的前提下，才对用户传送的信息进行解码，否则，接收机报告数据包冲突。我们发现，在这种通信模式下，系统的本质性能可以用一个“速率区域”来表征。当用户的通信速率恰巧在速率区域之内的时候，接收机可以可靠地对所有用户的信息进行解码，而当用户的通信速率恰巧在速率区域之外的时候，接收机可以可靠地检测到数据包冲突。虽然速率区域的定义和传统的编码理论有很大的不同，我们发现系统的最大速率区域等同于没有凸包围操作的信息论信道容量。

       简历: 罗杰(J. Rockey Luo)于2002年在康涅狄克大学电子工程系获得博士学位。在2002到2006年间，他是马里兰大学系统研究所的博士后研究员。2006年秋季，他加入科罗拉多州立大学电子工程系成为助理教授。他的科研主要侧重于无线网络理论的研究。

       联系人: 胡波 教授, bohu@fudan.edu.cn   

       这个讲座将用中文演讲，但是幻灯将用英文书写。