||Nowadays, we make a broad varieties of wireless devices by new technology, which providing handheld devices with multiple variations of services, such as monitoring the state changes of the electrical appliances. The electrical appliances have a greater diversity of functions. Consequently, people life becomes more convenient and intelligent. Most of the sensors in the wireless sensor network are constrained devices. In recent year, researcher have proposed to integrate IPv6 into constrained devices, and subsequently developed a constrained application protocol (CoAP). So that a constrained device can be more easily connected to realize Internet of things. However, when the message transmissions between constrained devices are frequent, the increased power consumption will make micro-wireless devices infeasible for high loads. Therefore, saving power is the primary concern of wireless devices to communicate with each other.|
In this thesis, clients specify the period of receiving messages and inform the proxy, which allows clients to avoid excessive information, and therefore saves energy consumption. Clients confirm the connections with the proxy and the proxy maintains connections with servers. The Minimum Period (p_min) and Maximum Period (p_max), which satisfy the quality of service requirements of clients are used as the parameters of the specified periods. Clients will append these two parameters into their request messages and send them to the proxy.
Grouping algorithm groups clients by splitting clients of long periods and short periods, for avoiding situations where short-cycle clients drastically let down the maximum periods of the high-cycle groups. Next, the cache mechanism of proxy and the Max-Age selection algorithm to set the frequency at which each notification is updated in the cache ensure the clients receiving the latest notifications and the client-server connections. The merge algorithm combines notifications from the cache that are valid and have the same receiving end, to further reduce the number of times the client getting notifications.
This thesis will propose scheme to decrease the energy consumption of the overall structure by which all CoAP clients’ quality of service (QoS) requirement are satisfied. To use grouping algorithm, caching mechanism, Max-Age selection algorithm and merge algorithm substantially reduce the number of proxy transmissions, the number of messages received by the clients, and the number of server response messages. As a result, the number of messages between the clients and proxy, the number of messages between the proxy and the server, and the energy consumption of the overall architecture are greatly decreased.