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 Downlink Coexistence Performance Assessment and Techniques for WiMAX Services from High Altitude Platform and Terrestrial Deployments | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2008 Article ID 291450 7 pages doi 2008 291450 Research Article Downlink Coexistence Performance Assessment and Techniques for WiMAX Services from High Altitude Platform and Terrestrial Deployments Z. Yang 1 A. Mohammed 1 T. Hult 1 and D. Grace2 1 Department of Signal Processing Blekinge Institute of Technology BTH 372 35 Ronneby Sweden 2 Department of Electronics University of York YorkYO10 5DD UK Correspondence should be addressed to Z. Yang zya@ Received 1 November 2007 Revised 30 April 2008 Accepted 6 August 2008 Recommended by Shlomi Arnon We investigate the performance and coexistence techniques for worldwide interoperability for microwave access WiMAX delivered from high altitude platforms HAPs and terrestrial systems in shared GHz frequency bands. The paper shows that it is possible to provide WiMAX services from individual HAP systems. The coexistence performance is evaluated by appropriate choice of parameters which include the HAP deployment spacing radius directive antenna beamwidths based on adopted antenna models for HAPs and receivers. Illustrations and comparisons of coexistence techniques for example varying the antenna pointing offset transmitting and receiving antenna beamwidth demonstrate efficient ways to enhance the HAP system performance while effectively coexisting with terrestrial WiMAX systems. Copyright 2008 Z. Yang 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. 1. INTRODUCTION High altitude platforms HAPs are either quasi-stationary airships or aircraft operating in the stratosphere 17-22 km 72 000 ft above the ground and have been suggested as a way of providing the third generation 3G and mm-wave broadband wireless access BWA 1-3 . A HAP trial held by .
