## 4 Performance Evaluation, Analysis and Discussion
Figure 17 provides comparative analysis when nodes are 100% active, means with DC value 100%. It is noticed that ECG and EEG nodes provide high packet reception with almost 90% packet delivery ratio in GTSon mode, whereas their performance is low in GTSoff mode. The reason is that these nodes generate many small packets in a limited time and there is no guarantee whether they get a channel access or not as the other nodes are also contending; therefore, the packet lost ratio is high on queues due waiting time and limited space in queues. On the other hand when GTS mode is used for ECG and EEG they provide high number of received packets as in every superframe they get three GTS  
Figure 16: Maximum throughput analysis. Figure 15: Received packets analysis for aggregation in GTSon mode. slots each. It is also noticed that in the hybrid mode (with usage of GTS slots) the node which does not use GTS can provide a lower number of received packets in comparison with a node which only uses slotted CSMA/CA like SpO2 sensor node. The reason for low received packets in the hybrid mode is that superframe is divided in 16 slots, GTS uses six slots (three for ECG and three for EEG) and 10 slots left for seven remaining nodes, these nodes content for the channel and SpO2 gets less number of channel accesses. On the other hand, in non-hybrid mode (all nodes use slotted CSMA/CA for channel access), nine nodes content for all the available slots, where SpO2 gets more slots than in the hybrid mode. The other remaining sensors including BP, respiration, diabetes, temp and accelerometer are sending data at low rate, therefore there is no critical issue involve with them. Figure 10.0 Received packet analysis for individual node without DC. Figure 10.1 Received packet analysis for individual node with DC. Figure 18 provides the analysis regarding suitability of a hybrid MAC for the proposed patient monitoring system. However, the DC mechanism is not considered in scenario relevant to Figure 10.2 Figure 18 provides the similar scenario in Figure 17 but with DC value 2/4 (25% active) to evaluate the performance by considering an energy efficient mechanism. It is noted that due to the usage of DC mechanism in hybrid mode the number of received packets reduces almost up to 50%. The reason is the less awaken interval of the nodes. The overall received packet rate for each senor is affected due to DC mechanism. To overcome the issue presented in Figure 18, we apply the frame aggregation mechanism. Figure 19 provides comparative analysis of received packets of individual sensors under four modes i.e., GTSoff, GTSon, GTSon_Agg_2 and GTSon_Agg_4. Moreover, the DC mechanism is considered with the value of 25%. It is noted that the frame aggregation mechanism increases the number of received packets significantly for each node. We use IEEE 802.15.4 with operating band of 2.4 GHz that may also receive signals as interference from coexisting IEEE 802.11 deployed wireless networks and some unknown wireless networks. The device like Series 2 Xbee-PRO 52B of Digi International which uses Ember (Silicon Labs, Global Headquarters, Digi International, 11001 Bren Road East, Minnetonka, MN, USA) EM250 as the radio chip which is IEEE 802.15.4-complaint transceiver and operates at 2.4 GHz ISM band with 250 kbps data rate. It provides 16 different operating channels. The proposed aggregation mechanism provides efficiency in terms of delay, throughput and energy utilization to accommodate patient monitoring applications. In the above mentioned scenarios and analysis the data is collected from multiple sensors, for this scenario we consider that each patient consists of a WBASN and there are multiple WBASNs in a location like a hospital ward. For such scenario, the nodes may face interference from nearby WBANs and already deployed wireless LANs (WLANs) which works on 2.4 GHz band.