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Advances in Multimedia
Volume 2007, Article ID 74591, 9 pages
http://dx.doi.org/10.1155/2007/74591
Research Article

Location-Aware Cross-Layer Design Using Overlay Watermarks

1Communications Research Centre Canada, 3701 Carling Avenue, P.O. Box 11490, Station H, Ottawa, ON K2H 8S2, Canada
2School of Engineering Science, Simon Fraser University, Burnaby, BC V5A 1S6, Canada

Received 28 December 2006; Accepted 7 March 2007

Academic Editor: Jianwei Huang

Copyright © 2007 Xianbin Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A new orthogonal frequency division multiplexing (OFDM) system embedded with overlay watermarks for location-aware cross-layer design is proposed in this paper. One major advantage of the proposed system is the multiple functionalities the overlay watermark provides, which includes a cross-layer signaling interface, a transceiver identification for position-aware routing, as well as its basic role as a training sequence for channel estimation. Wireless terminals are typically battery powered and have limited wireless communication bandwidth. Therefore, efficient collaborative signal processing algorithms that consume less energy for computation and less bandwidth for communication are needed. Transceiver aware of its location can also improve the routing efficiency by selective flooding or selective forwarding data only in the desired direction, since in most cases the location of a wireless host is unknown. In the proposed OFDM system, location information of a mobile for efficient routing can be easily derived when a unique watermark is associated with each individual transceiver. In addition, cross-layer signaling and other interlayer interactive information can be exchanged with a new data pipe created by modulating the overlay watermarks. We also study the channel estimation and watermark removal techniques at the physical layer for the proposed overlay OFDM. Our channel estimator iteratively estimates the channel impulse response and the combined signal vector from the overlay OFDM signal. Cross-layer design that leads to low-power consumption and more efficient routing is investigated.