An energy-efficient Service Discovery protocol for the IoT based on a multi-tier WSN architecture

The Internet of Things is expected to foster billions of heterogeneous sensors and actuators that support a wide range of applications. Maximizing the utilization of these sensors is hinged upon the ability to discover their capabilities (ex: measured attributes, location, accuracy, etc.). This process is known as Service Discovery (SD), and can have a local scope (SD within a bounded area), or a global scope. Traditionally, SD is performed using a dedicated gateway that is always active and connected to the Internet. This gateway stores the attributes of sensors within its area. However, this approach may be too expensive in the presence of billions of sensors. In this paper, a novel protocol for local SD is proposed that eliminates the need for a dedicated gateway. The protocol utilizes a multi-tier network architecture in order to achieve two main objectives: energy efficiency and high success rate in satisfying service requests. Energy efficiency is achieved by limiting the number of hops that an SD request has to traverse before being satisfied, while a high success rate is guaranteed using a hierarchical structure of Distributed Hash Tables (DHTs), where information regarding sensor capabilities is stored. Extensive computer simulations are used to evaluate the performance of the proposed protocol in comparison to single level architectures and gateway-based solutions. The results show that the proposed protocol achieves energy efficiency without sacrificing success rate of serving requests.