TAILIEUCHUNG - Báo cáo hóa học: " Research Article Clear Channel Assessment in Integrated Medical Environments"

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 Clear Channel Assessment in Integrated Medical Environments | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2008 Article ID 821756 8 pages doi 2008 821756 Research Article Clear Channel Assessment in Integrated Medical Environments Bin Zhen 1 Huan-Bang Li 1 Shinsuke Hara 2 and Ryuji Kohno3 1 National Institute of Information and Communications Technology NICT 3-4 Hikarino-oka Yokosuka 239-0847 Japan 2 Osaka City University 3-3-138 Sugimoto Osaka 530-0001 Japan 3 Yokohama National University 79-5 Tokiwadai Yokohama 240-8501 Japan Correspondence should be addressed to Bin Zhen Received 16 July 2007 Accepted 24 November 2007 Recommended by Yi-Bing Lin Complementary WLAN and WPAN technologies as well as other wireless technologies will play a fundamental role in the medical environments to support ubiquitous healthcare delivery. This paper investigates clear channel assessment CCA and its impact on the coexistence of WLAN IEEE high rate direct sequence spread spectrum HR DSSS PHY and WPAN IEEE in the GHz industrial scientific and medical ISM band. We derived closed-form expressions of both energy-based CCA and feature-based CCA. We qualified unequal sensing abilities between them and termed this inequality asymmetric CCA which is different from the traditional hidden node or exposed node issues in the homogeneous network. The energy-based CCA was considered in the considered integrated medical environment because the GHz ISM band is too crowded to apply feature-based CCA. The WPAN is oversensitive to the HR DSSS signals and the WLAN is insensitive to the signals. Choosing an optimal CCA threshold requires some prior knowledge of the underlying signals. In the integrated medical environment we considered here energy-based CCA can effectively avoid possible packet collisions when they are close within the heterogeneous exclusive CCA range HECR . However when they are separated beyond the HECR WPAN can still sense

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