Efficient Multi-hop Broadcast Data Dissemination for IoT and Smart Cities Applications

In the last years, due to the growing interest in smart cities and Internet of Things (IoT) applications, several innovative types of networks, such as Vehicular Ad-hoc NETworks (VANETs) and Opportunistic (such as pedestrian or Machine-to-Machine, M2M) ad-hoc networks, have been deeply investigated. In this type of networks, broadcasting is a very important transmission strategy which allows fast data dissemination. For example, this type of communication assumes a particular importance in the so-called Service Discovery mechanisms (e.g., ZeroConf). Widely exploited in IoT scenarios, these mechanisms provide that nodes advertise, through broadcast/multicast communications, a particular offered service. In this way nodes and associated services can be automatically and dynamically discovered without human intervention. Another example where broadcasting assumes a key role is represented by routing protocols for Mobile Ad-hoc NETworks (MANETs) (e.g., Ad-hoc Ondemand Distance Vector (AODV) [9] and Dynamic Source Routing (DSR) [2])). In fact, these protocols perform multihop broadcasting, based on the flooding technique, in order to find a route to a desired destination or send control messages to all nodes in the network. According to flooding each node is required to retransmit packets when received for the first time. The flooding strategy, because of highly redundant transmissions, can lead to serious inefficiencies, related to the high channel contention level which results in collisions and interference. This problem, referred to as Broadcast Storm Problem (BSP) [7] in the literature, is more exacerbated in IoT and smart cities scenarios where a great amount of densely deployed nodes are typically present. In general, there are many approaches that can be used in order to reduce the redundancy introduced by flooding—the interested reader is referred to [7] for a possible classification— and, thus, design energy-efficient broadcast mechanisms. In order to achieve efficient multi-hop broacast communications in these years we have investigated the so-called probabilistic broadcast techniques. In simple terms, when a node receives a packet, it rebroadcasts it with probability p and takes no