## 2 Relevant Work
Priority-based Fairness Rate Control (PFRC) adjusts data rates for non-real time traffic based on the network congestion [27]. The priority of traffic as well as the fair assignment of bandwidth are used for allocating resources. Tree topology has been used and priority has been assigned to the nodes based on their level in the hierarchy. Hence, the three units of Differential Rate Adjustment Unit (DRAU), Congestion Detection Unit (CDU), Priority Adjustment Unit (PAU) and Fairness Control Unit (FCU) provide input for rate control decision making. The major limitations of the protocol lie in its priority assignment based on the node level rather than the traffic type in the node. Furthermore, it is also not possible for the nodes in PFRC to interrupt the ongoing transmission. Priority-based Adaptive MAC (PA-MAC) is developed for (WBAN) in order to customize the IEEE 802.15.4 for medical applications [21]. PA-MAC dynamically allocates slots and contention window to the traffic based on its priority level. Different categories of traffic such as emergency, on-demand, normal, non-medical have been assigned priority based on their delay tolerance level. The major performance gap in PA-MAC is the lack of interruption opportunity for the emergency traffic and the sharing of transmission slots between the high & low priority data. Priority-Based Data Gathering Framework for WSN using Unmanned Aerial Vehicles (UAV) has been developed in [28], with the aim of improving the data gathering method. The nodes have been assigned different priorities based on their locations within the UAV coverage area. The priorities have been assigned to nodes, using different contention window values. The authors have also proposeda supporting routing protocol to optimize the energy performance of network. The interruption for ongoing traffic is also not included in this approach. Interrupt-MAC (I-MAC) has been developed for WBANs by inserting short interruption slots in the super frame which could reduce the data delivery delay for urgent medical traffic [29]. Most of the time slots are allocated to the nodes which have regular periodic data, however, during the short interruption slot, the coordinator can break the executing super frame to start the new one with real-time requirement. Although I-MAC provides a higher chance for emergency traffic to access the channel as compared to conventional super frame-based schemes, the nodes still need to wait for the coordinator to interrupt the ongoing transmission and they could not send data on their own. Game theory-based approach has been used to assign priorities to the nodes in WBAN in order to efficiently deal with critical data [30]. The gap identified by the authors is that conventional protocols in WBAN deal similarly with the packets with regular health monitoring data and packets with critical data, which results in high average time for the data with critical information. Hence, the authors proposed Priority-based Allocation of Time Slots (PATS) which assigns priority to the nodes based on the criticality of information. Hawk-dove game model has been used for priority assignments. The proposed scheme may guarantee low average delay for the critical health monitoring data; however, the complexity of the scheme is relatively higher as compared to other proposed schemes. The miniature WSN nodes can only handle limited complexity due to the limit on computing resources. Furthermore, no support for interrupting the ongoing low priority transmission is offered. RushNet focuses on efficient delivery of heterogeneous data in the saturated WSN [8], where the rate of data generation is assumed to be close to the available network bandwidth. The high priority data has been assumed to be sporadic but urgent, whereas the authors classified low priority traffic with high volume but to be delay tolerant. The protocol does not need co-ordination of schedules and is designed to perform well for the large scale WSN. The two schemes of bulk transfer and capture effects have been used.