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WBANs are a network of small size, lightweight, low power, wearable/implantable sensors. These sensors monitor human’s physiological activities like Patient’s Heartbeat, blood pressure, Electrocardiogram (ECG), EMG, etc. WBANs allow connectivity in between heterogeneous body sensor to a portable hub devise that provide a connection to the external internet. There are a variety of applications of the WBANs. Military can use it to monitor the physical location, physical condition, and vital signs of a field person. In the medical perspective, we can keep track patient’s physiological condition, to provide medical facilities [1]. On a single body, multiple sensors can be placed and these nodes used to form a single WBAN. Each WBAN has a centralized entity called Personal Server (PS). It gathers data from other sensors and acts as a gateway. PS has a connection to RBS directly or with multiple hops. Communication of two types, intra-WBAN and inter-WBAN occurs in the WBANs. Intra-WBAN is a communication within the sensors of a single WBAN. On the other hand, Inter-WBAN is communication among multiple WBANs. Information collected by the sensors is transmitted to the remote Medical-Server, which is situated in the hospital. Inter-WBAN communication provides dynamic access when patients are doing their normal routine work (during movement in home, office, market or playground). In this case, sensor residing on the human body may or may not be in the range of RBS. So cooperation of multiple WBANs is required for hop-to-hop communion, to reach the RBS. RBS is responsible for further transmission to Medical-Server via the internet. WBANs are capable of protecting human lives by detecting patient’s critical conditions at its early stages. Many human lives are dependent on the performance of the WBAN. Routing strategy is the key to network efficiency. There are different routing mechanisms of inter-BAN and intra-BAN communication. Each WBAN needs to be connected to the external network with the help of a gateway.

This gateway can be a Cellular device, a computer system, or a router which is capable of establishing a connection between inter-WBAN nodes and external internet. The problem arrives when WBAN do not have access to gateway device due to some reason. It is a common experience in a crowded area, like in stadium of international games or any kind of international event, where a huge amount of people access the same network and share their photos and videos. Due to congestion, degradation in the performance of network occurs. Although nowadays cellular networks provide a highly efficient network, it is not enough in some cases, that’s why a separate public safety radio system is used by police, firefighters and emergency medical technicians. It operates in separate portions of the 800 MHz band, which consists of a spectrum at 806–824 MHz paired with spectrum at 851–869 MHz. Another scenario is the battlefield where there is no Access Point available in the vicinity of every soldier as shown in Figure 3.1.

Figure 3.1 Base station is not in access of some WBANs.

Inter-WBAN communication can be useful in both of the cases. As WBAN consists of low power energy nodes, we required an efficient energy consumption routing technique. Clustering is one of the best solutions for efficient routing, where a cluster head is responsible for the transmission of data of multiple WBANs. Network efficiency is dependent on the cluster’s lifetime. In this paper, we proposed an optimization technique of clusters formation using Evolutionary Algorithms. Each cluster head (CH) is a gateway in between cluster members (PSs) of multiple WBANs and the external network. CHs are selected on the bases of fitness.