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 Cross-Layer Design in Dynamic Spectrum Sharing Systems | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2010 Article ID 458472 8 pages doi 2010 458472 Research Article Cross-Layer Design in Dynamic Spectrum Sharing Systems A. Shadmand K. Nehra and M. Shikh-Bahaei Department of Electronic Engineering Division of Engineering King s College London WC2R2LS London UK Correspondence should be addressed to K. Nehra Received 15 January 2010 Revised 28 May 2010 Accepted 9 August 2010 Academic Editor Hyunggon Park Copyright 2010 A. Shadmand 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. We consider a dynamic spectrum sharing system consisting of a primary user whose licensed spectrum is allowed to be accessed by a secondary user as long as it does not violate the prescribed interference limit inflicted on the primary user. Assuming the Nakagami-m block-fading environment we aim at maximizing the performance of secondary user s link in terms of average spectral efficiency ASE and error performance under the specified packet error rate PER and average interference limit constraints. To this end we employ a cross-layer design policy which combines adaptive power and coded discrete M-QAM modulation scheme at the physical layer with a truncated automatic repeat request ARQ protocol at the data link layer and simultaneously satisfies the aforementioned constraints. Numerical results affirm that the secondary link of spectrum sharing system combining ARQ with adaptive modulation and coding AMC achieves significant gain in ASE depending on the maximum number of retransmissions initiated by the ARQ protocol. The results further indicate that the ARQ protocol essentially improves the packet loss rate performance of the secondary link. 1. Introduction The rapidly growing demand for wireless .
