Abstract-Wireless Body Area Networks (WBANs) are one of the key technologies that support the development of digital health care, which has attracted increasing attention in recent years. Compared with general Wireless Sensor Networks (WSNs), WBANs have more stringent requirements on reliability and energy efficiency. Though WBANs are applied within limited transmission range, the on-body channel condition can be very challenging because of blocking or absorbing of signal. In this paper, we are looking into the design of Medium Access Control (MAC) protocols and propose an opportunistic scheduling scheme by applying heuristic scheduling and dynamic superframe length adjustment to improve the system performance. The simulations have been supplemented to show the advantages of the proposed solutions in outage rate performance, compared with existing solutions.
I. INTRODUCTION Inspired by the development of Internet-of-Things [5], [6],Wireless Body Area Networks (WBANs), which collect and transfer real time body signals for medical care purpose, play a fundamental role in future health applications. In such a network, energy efficiency and transmission reliability are major concerns. Reducing outage rate is thus crucial since it indicates less retransmissions, which will save energy and reduce transmission delay.Though WBANs are applied within limited range, the unpredictable channel environment through human body is a challenge for wireless communication [2]. The reason is that the transmission power of sensors need to keep low to save energy and avoid impairing body tissues. At the same time, body parts can block and absorb the signals, making the link status vulnerable. Opportunistic scheduling can take channel state into consideration and since the channel fluctuation is a major influence on the performance of WBANs, it has the potential of improving the system performance to a large extent by selecting good channels.A survey [1] provides a comprehensive summary on opportunistic scheduling. So far, the opportunistic scheduling research largely focuses on cellular networks, which are not necessarily suitable for WBANs. WBANs have special requirements of extremely low energy consumption and high reliability that are not considered by the methods in [1].Several solutions have been proposed focusing on opportunistic scheduling to WBANs. [8], [9], [11] focus on applying Markov chain model to forecast the channel condition based on the previous transmissions. In [8], [9], the