tailieunhanh - Báo cáo hóa học: " Research Article Code Design for Multihop Wireless Relay Networks"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Code Design for Multihop Wireless Relay Networks | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2008 Article ID 457307 12 pages doi 2008 457307 Research Article Code Design for Multihop Wireless Relay Networks Frederique Oggier and Babak Hassibi Department of Electrical Engineering California Institute of Technology Pasadena CA 91125 USA Correspondence should be addressed to F. Oggier frederique@ Received 2 June 2007 Revised 21 October 2007 Accepted 25 November 2007 Recommended by Keith Q. T. Zhang We consider a wireless relay network where a transmitter node communicates with a receiver node with the help of relay nodes. Most coding strategies considered so far assume that the relay nodes are used for one hop. We address the problem of code design when relay nodes may be used for more than one hop. We consider as a protocol a more elaborated version of amplify-and-forward called distributed space-time coding where the relay nodes multiply their received signal with a unitary matrix in such a way that the receiver senses a space-time code. We first show that in this scenario as expected the so-called full-diversity condition holds namely the codebook of distributed space-time codewords has to be designed such that the difference of any two distinct codewords is full rank. We then compute the diversity of the channel and show that it is given by the minimum number of relay nodes among the hops. We finally give a systematic way of building fully diverse codebooks and provide simulation results for their performance. Copyright 2008 F. Oggier and B. Hassibi. 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. 1. INTRODUCTION Cooperative diversity is a popular coding technique for wireless relay networks 1 . When a transmitter node wants to communicate with a receiver node it uses its neighbor .