Prevention of Beacons Collision in IEEE 802.15.6 under Coexistence

Abstract

IEEE 802.15.6 standard is designed for Wireless Body Area Network (WBAN). WBAN connects wireless sensor nodes in/on or around the human body. WBAN is specially designed for monitoring e-health applications like temperature, blood pressure and fever etc. One of the basic concerns in IEEE 802.15.6 networks is coexistence of multiple BANs. This is a natural phenomenon as multiple BANs while coexisting can be within the transmission range of each other. For example, in a sitting room, conference room, stadium and hospital BANs attached with different peoples can be within the radio range of each other. When multiple BANs coexist then the performance of an individual BAN is degraded due to interference with neighboring BANs. Interference causes unsuccessful transmission of data, thus lowering the throughput, and energy of devices is wasted which is an important resource for WBAN devices. This work is amid at studying the coexistence issues within the WBANs. IEEE 802.15.6 proposes different solutions including beacon shifting, channel hoping, and superframe interleaving for solving the issue of coexistence. In beacon shifting the collision of beacons is avoided by transmitting the beacons at different offsets in a superframe instead of start of every superframe. Beacon shifting defined by IEEE 802.15.6 allows BANs to select a sequence index that is not being used by another BAN. As only eight different sequence indexes are defined so it can supports only eight BANs. In this study, a beacon shifting scheme is proposed to solve the issue of beacons collision under coexistence by adding a beacon phase to the superframe of IEEE 802.15.6. The scheme adjusts the transmission time of beacons in the beacon phase for all coexisting BANs and allows BANs to transmit their beacons in allocated time slot in the beacon phase. Hence, instead of assigning different sequence indexes which has overlapping patterns, the proposed scheme allocates time slots in beacon phase to avoid beacon collision. Detailed simulation analysis using OPNET, concludes that proposed scheme provides greater beacon delivery ratio and higher throughput than beacon shifting technique used in IEEE 802.15.6.