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The IEEE 802.15.6 standard is an emerging technology that supports low data rate, short-range wireless communication. Medical Body Area Networks (MBAN) are a special type of wireless communication where multiple sensor nodes are deployed on the human body to measure vital parameters. The data is sent by the nodes to a coordinator, the latter aggregates the data and sends it to a central server using standard protocols. The coordinator allows the nodes to access the channel using different access modes-beacon mode with the super frame, non-beacon mode with super frame and non-beacon mode without super frame. The standard allows different user priorities to be assigned to the nodes. The nodes may access the channel using scheduling done by the coordinator (scheduled access) or may randomly access the channel using the CSMA/CA (for narrowband PHY) or Slotted Aloha for UltraWideBand (UWB PHY) protocols. In this work we have conducted an analytical study to understand the performance parameters of different user priority nodes using CSMA/CA protocol and operating in the Beacon access mode with super frame boundaries. Parameters like the probability of successful transmission (reliability) which in turn depend on the probability of packet drop due to channel access failure and the probability of failure due to insufficient time slot available have been studied. This study reveals that once a channel is assessed by a node, then the probability of sufficient time slot of 60% yields the best packet transmission probability. The successful delivery of the packet also depends on back off counter. Markov chain models for nodes with different priorities have been developed using backoff stage and backoff counter as parameters.

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