# Energy Aware and Quality of Service Routing Mechanism for Hybrid Internet of Things Network
## 2 Related Works  
Existing research on energy optimization and QoS service routing in wireless multi-hop networks are drawing significant attention in the research community. The authors in [15] presented a routing protocol that supports the transmission of multimedia stream in WMMSN. The routing protocol makes packet forwarding decisions based on the position of sensors nodes to the destination of the nodes. The mechanism uses the load balancing technique in a multipath-to-destination to distribute the load and increase the lifetime of the network. Similarly, the authors in [16; 17; 18; 19] employ load balancing techniques in networks for increasing the lifetime of a network. Most of the proposed solutions are based on uniformly distributing a load over the network, thereby maximizing the lifetime of the networks without compromising the performance. However, distributing load uniformly over a network is not necessarily energy efficient in terms of the global energy saving of the network. This is because the mechanism forces nodes in the network to remain turned on even if it is transmitting a small amount of data. Therefore, this research focused on global energy consumption savings in multi-hop mesh networks, while maintaining a certain amount of QoS.  
The authors in [11] proposed a throughput and energy-aware routing mechanism for IEEE 802.11-based mesh networks. It is a centralized routing mechanism, which requires a global view of the network. The proposed solution is based on integer linear programming to maximize the number of nodes that can be turned off while guaranteeing throughput. However, the solution applied an iterative algorithm in order to find the optimum solution that left as many routers as possible switched off.  
The authors in [20] proposed a routing mechanism that allows flows to be aggregated over a minimum number of nodes for any set of source and destination nodes in a multi-hop wireless network. The authors proposed a solution based on integer linear optimization to route flows over a minimum number of nodes while respecting QoS in terms of throughput. Aggregating a set of flows over a minimum number of nodes allows some flows to take a longer path to their destination. Considering the ideal wireless channel, a longer path incurs longer delay in the flows to the destination. Therefore, in the case of large node deployment; it has a significant negative impact on delay-sensitive applications such as video transmission.  
Therefore, this paper proposes a centralized energy-aware and QoS routing algorithm for mesh-connected visual sensor nodes in a hybrid IoT network, as proposed in [6]. The routing algorithm allows the routing of a set of video streams to the gateway with guaranteed bandwidth and limited delay (with the assumption that the end-to-end packet transmission delay is proportional to the number of hops in a path) while using as few visual sensor nodes as possible in the network. This allows for only those nodes that are involved in the surveillance and routing to be turned on, while turning off (or putting in a complete shutdown mode) the idle nodes that are not involved in the routing and surveillance.  
Table 1 shows a summary of the related research by different authors and our proposal according to energy consumption reduction, interference considerations, and QoS guarantees.