With the technological advancements in the field of Wireless Sensor Networks (WSNs) in the last decade, a number of remote monitoring and health care applications have made their presence felt through implanted and wearable biosensors. These biosensors can be used for real time patient monitoring creating a Wireless Body Area Sensor Network (WBASN). These biosensors are equipped with limited battery creating a requirement for energy-efficient schemes for WBASN protocols. The biosensor nodes are heterogeneous in terms of buffer size, traffic type, inter-arrival time and payload size. The data generated by these nodes may have different requirements based on their quality parameters. A biosensor node generating electroencephalography (EEG) reading may require reliable transmission of data and same way some other biosensor node may generate delay sensitive data. Differing requirements of these biosensor nodes lead to the requirement of QoS aware schemes for WBASN. In this paper, an energy-efficient Quality of Service (QoS) aware time slot allocation scheme is proposed for WBASN Media Access Control (MAC) layer. This scheme takes heterogeneity of biosensor nodes under consideration. Slot allocation is based on QoS aware priority classes. Unlike most of the existing schemes, time slot duration is traffic adaptive in this sch eme and variable length slots are allocated based on different payload sizes of the sensor nodes. This scheme improves the energy efficiency by reducing the chances of packet drops and energy wastage due to idle listening. Sleep time for sensor nodes is increased leading to lower energy consumption. The proposed time slot allocation scheme is compared with slot allocation scheme of eMC-MAC protocol. Simulation result shows a significant improvement in energy efficiency over eMC-MAC slot allocation scheme.

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