From Theory to Practice: An Overview of Multi-hop Relaying Technology for Next Generation Broadband Wireless Systems

Ozgur Oyman

July 13, 2006

Abstract

The very high data rates envisioned for fourth-generation (4G) wireless systems in reasonably large or densely populated areas do not appear to be feasible with the conventional cellular architectures. In this context, distributed communication techniques, multi-hop relaying in particular, could provide a leverage for better capacity, coverage and reliability without requiring significant infrastructure deployment costs. With this motivation, there has been recently a growing interest both in academia and industry in the concept of relaying in infrastructure-based wireless networks such as next generation cellular (B3G, 4G), wireless local area networks (WLANs) (802.11, WiFi, HyperLAN) and broadband fixed wireless (802.16, WiMax, HyperMAN) networks. The development of novel PHY and MAC layer algorithms to support multi-hop relaying technology plays a key role for facilitating its standardization and use in design of commercial systems. The first part of the talk shall provide an overview of current research challenges and ongoing standardization activities with specific focus on 802.16-based broadband wireless networks. In the second part of the talk, we shall present an information-theoretic analysis of multi-hop communications in wireless networks under the joint consideration of power and bandwidth efficiency and reliability constraints. In particular, we study the power-bandwidth tradeoff in a one-dimensional multi-hop relay network assuming a non-ergodic fading model. We characterize the impact of multi-hopping on the statistical properties of the end-to-end conditional mutual information (conditioned on the specific values of the channel fading parameters and therefore treated as a random variable) and on the power and bandwidth efficiency measures computed from the conditional mutual information. Our non-ergodic power-bandwidth tradeoff analysis focuses on two asymptotic regimes: (i) Power-limited (low signal-to-noise ratio (SNR)) regime and (ii) Bandwidth-limited (high SNR) regime. In both regimes, we investigate the performance of open-loop (fixed-rate) and closed-loop (rate-adaptive) multi-hop relaying mechanisms in terms of their power-bandwidth tradeoffs and end-to-end outage probabilities. Interestingly, our analysis reveals the new notion of "multi-hop diversity" toward enhancing link reliability in diversity-limited fading environments.

Speaker Bio

Dr. Ozgur Oyman is a senior research scientist in the Corporate Technology Group at Intel Corporation in Santa Clara. He holds M.S. (2002) and Ph.D. (2005) degrees from Stanford University and a B.S. (2000) degree from Cornell University. At Stanford, he was a member of the Smart Antenna Research Group within the Information Systems Laboratory. He was a visiting researcher at the Communication Theory Group within the Swiss Federal Institute of Technology (ETH Zurich) in 2003. His prior work experience includes internships at Qualcomm (2001), Beceem Communications (2004) and Intel (2005). His research interests are in applications of communication and information theory to wireless communications, with special emphasis on multiple-input multiple-output (MIMO) antenna systems and mesh/adhoc communication architectures.

LM Seminar Series
Fundamentals of Networking Lab

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