Abstract
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 802.11 high rate direct sequence spread spectrum (HR/DSSS) PHY) andWPAN (IEEE 802.15.4b) in the 2.4 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 integratedmedical environment because the 2.4 GHz ISM band is too crowded to apply feature-based CCA. The WPAN is oversensitive to the 802.11 HR/DSSS signals and the WLAN is insensitive to the 802.15.4b 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 the 802.11 HR/DSSS signals, but WLAN loses its sense to the 802.15.4b signals. The asymmetric CCA leads to WPAN traffic in a position secondary to WLAN traffic.
Highlights
Advances in biotechnologies and micro/nano-technologies, information and communication technologies enable revolutionary pervasive healthcare delivery in hospital, small clinic, residential care center, and home [1,2,3]
We studied the hybrid of 802.11 high rate direct sequence spread spectrum (HR/DSSS) and 802.15.4b as examples
We have shown and qualified the asymmetric clear channel assessment (CCA)
Summary
Advances in biotechnologies and micro/nano-technologies, information and communication technologies enable revolutionary pervasive healthcare delivery in hospital, small clinic, residential care center, and home [1,2,3]. There is a desire to use IEEE version of WLAN and WPAN technologies in the unlicensed industrial, scientific, and medical (ISM) bands as a common communication infrastructure [2, 3]. The former is typically used for officeoriented applications and patient connection to the outside world, while the latter is usually used for wearable sensors around patient to collect vital information [2,3,4,5]. The use of complementary heterogeneous WLANs and WPANs in ISM band in the integrated medical environment brings into picture coexistence, interference, and spectrum utilization issues.
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