## 5 Network Management Architecture of the Proposed Topology  
This section presents the network management architecture and processes for the proposed logical topology. Network management is the process of managing, monitoring, and controlling the behaviour of a network. The management approach of WSNs differs from the traditional wired networks and mobile ad-hoc wireless networks due to the unique characteristics and restrictions of WSNs. Figure 19: Communications in a chain. (**a**) Control message dissemination; (**b**) Sending data towards the lower-level leader. WSN management systems can be classified according to their network architecture: centralised, distributed, or hierarchical. In centralised management systems, the BS acts as the manager station that collects information from all nodes and controls the entire network. However, this approach has some problems. First, it incurs a high message overhead (bandwidth and energy) from data polling, which limits the scalability of WSNs. Second, the central server is a single point of data traffic concentration and potential failure. Lastly, if a network is partitioned, sensor nodes that are unable to reach the central server are left without any management functionality. Distributed management systems employ multiple manager stations. Each manager controls a sub-network and may communicate directly with other manager stations in a cooperative fashion in order to perform management functions. However, this approach is complex and difficult to manage. Furthermore, distributed management algorithms may be computationally too expensive for resource-constrained sensor network nodes. Hierarchical network management is a hybrid between the centralised and distributed approach. Intermediate managers are used to distribute management functions, but do not communicate with each other directly. Each manager is responsible for managing the nodes in its sub-network. It passes information from its sub-network to its higher-level manager, and also disseminates management functions received from the higher-level manager to its sub-network. This architecture integrates the benefit of both the centralised and distributed management architecture and is more suitable for WSNs. Consequently, hierarchical network management was chosen for the proposed logical topology. For the proposed multiple chain oriented topology, a three-layer hierarchical management architecture is proposed. Figure 21 represents the relationship between the different entities of the management architecture, namely the manager, the sub-manager and the agent nodes. The manager is in the highest level of the hierarchy and is placed at the BS. The lower-level chain leaders of the proposed topology work as sub-managers, and the chain member nodes work as agent nodes. The sub-managers are used  
Figure 20: Communication from the BS to the member nodes of a chain. to distribute management functions and collect and collaborate management data. The manager has the global knowledge of the network states and gathers the global knowledge from the underlying network layers and sub-managers. The proposed logical topology arranges the nodes into groups of chains and identifies a chain leader for each chain. This allows a subset of nodes to communicate with the sink nodes, conserving energy in the nodes that no longer need to send data to the sinks. Often sink nodes are farther away from many nodes in the network. Chaining procedure abandons these long paths required for communication for smaller hops since nodes will only be communicating with neighbour nodes (except for the chain leaders). Besides energy and bandwidth conservation, there are other advantages of clustering nodes in a WSN. One advantage is that it allows for spatial reuse of resources. If two nodes exist in different non-neighbouring clusters, it may be possible for the two nodes to share the same frequency or time slot. It is also beneficial in the presence of mobility.