## 5 Conclusions  
Aiming at patient monitoring applications of WBASNs, a frame aggregation mechanism has been proposed at the MAC layer in this paper to improve the channel access mechanisms as well as to meet strict time deadlines, provide reliable data delivery and fulfill energy efficiency requirements at the same time. For the patient monitoring system, we have selected ten different bio-medical sensor devices, including a coordinator and deployed them in a star topology. The devices include ECG, EEG, EMG, accelerometer, gyroscope, pulse oximeter, blood pressure, temperature, barometer and heart rate monitoring, etc. The sensors periodically collect data from the body and send towards monitoring station through the coordinator node. The periodic, high prioritized and emergency data demand a  
Figure 21: Multiple WBASN communication scenario.  
Figure 20: RSSI with interference.  
different set of QoS when they are integrated in a patient monitoring system. To address the mentioned challenges, initially we have provided traffic pattern analysis of these devices to understand their communication requirements. From the traffic pattern analysis, it is observed that these biomedical sensor devices generate many small packets in a limited time. The IEEE 802.15.4 standard supports the maximum frame size up to 127 bytes including 25 bytes of MAC header and 102 bytes of payload and a successful packet transmission involves the overheads like random backoff delay, two times CCA, 802.15.4 header with each frame, SIFS and acknowledgement transmission time. The maximum packet size from these bio-medical sensor devices used in the patient monitoring system is 17 bytes for a single frame including headers. Each frame contents the channel to send the data, so a node which wins the channel transmits a small packet and for the next packet transmission, it needs to content the channel again. Therefore, on getting a channel, a node is under utilizing the available maximum packet size capacity which is 127 bytes for a MAC frame and only transmits up to 17 bytes. To address these issues, we have used the frame aggregation mechanism, which will send multiple MAC frames under a single PHY header within a single successful channel access. The concept of frame aggregation makes a huge difference in throughput and delay performance by efficiently utilization in channel access mechanism. The proposed mechanism is initially evaluated through numerical modeling. In the next step, simulation is conducted in NS 2.29 and CASTALIA 3.2 with OMNeT++. The evaluation is conducted for both modes i.e., CAP and CFP. The evaluating parameters include number of received packet, average delay and energy consumption. Various constraints are considered in the simulations including SO/BO combinations (DC), GTSon, GTSoff, network performance evaluation and individual node performance evaluation.  
The authors would like to thank Erasmus Mundus Fusion Project (545831-EM-1-2013-1-ITERAMUNDUSEMA21) and Boumemouth University for partially funding the research. We acknowledge the contribution of all the participants who involved in this work. The cost of in open access is also covered by the project.  
[PERSON], [PERSON] and [PERSON] conceived and designed the experiments; [PERSON] performed the experiments, [PERSON], [PERSON], and [PERSON] analyzed the data and analysis. All authors contributed writing and reviewing the paper.  
The authors declare no conflict of interest.