A Scalable and Energy-Efficient MAC Protocol for Linear Sensor Networks

Abstract

Linear topologies arise naturally in the context of Internet-of-Things (IoT) applications for smart cities, where the infrastructure itself commonly has a linear or semi-linear structure. This is the case of buildings, public transportation systems, road infrastructure, and utility distribution networks. Given the prevalence of this type of topologies, several Medium Access Control (MAC) protocols have been designed to take advantage of their particular properties. Unfortunately, most of them do not scale well as the node density and the distance in hops to the sink increases. The result is that packets generated many hops away from the sink tend to experience unacceptable high end-to-end delay and low delivery probabilities. This paper introduces HP-MAC, a synchronized duty-cycled MAC protocol for Linear Sensor Networks (LSNs) that assigns transmission priorities to nodes to avoid collisions, through the implementation of distributed elections based on hash functions. HP-MAC also implements a packet queuing scheme that acts as a mechanism to control the amount of network resources allocated to data flows generated at different distances to the sink. This way, packets can reach their destination with loss probability and end-to-end delay that do not depend on their distance to the sink. We use a Discrete-Time Markov Chain (DTMC) to model the performance of the proposed protocol. Numerical solutions of this model show that HP-MAC outperforms state-of-the-art representatives in terms of throughput, end-to-end delay, power consumption, and packet loss probability. These results are validated through extensive discrete-event simulations.INDEX TERMS Linear sensor networks (LSN), synchronized duty-cycled MAC protocol, collision-free MAC protocol, Markov chain, energy-efficient Internet of Things (IoT).

Distance-Based Queuing for Scalable and Reliable Linear Wireless Sensor Networks in Smart Cities

“…Considering the same network topology, the authors of [15] propose an improvement to PRI-MAC by incorporating three algorithms that eliminate contention among nodes located within the same interference range; as a result, the performance in all the evaluated parameters improves significantly. In [13], the authors propose HP-MAC, which eliminates collisions by implementing distributed elections based on hash functions. The network nodes acquire transmission priorities, and only the node with the highest priority can transmit.…”

“…In [20,21], the authors analyze strictly linear WSNs, i.e., networks that consist of a single line of nodes (whereas in [13][14][15][16][17][18][19] the LWSN is assumed to be dense). The authors propose a routing algorithm that uses implicit acknowledgments to provide reliability and connectivity with energy efficiency, low latency, and fault tolerance.…”

“…The DBQ scheme is specifically suited for LWSNs that operate with synchronized Duty-Cycled, Pipelined-Forwarding (DCPF) MAC protocols [13][14][15][16][17][18][19]. In these networks, each node belongs to a grade i ∈ [1, I], where i is the node's hop distance to the sink and I is the total number of grades in the network, i.e., the network length, as illustrated in Figure 2.…”

“…Nodes at grade 1 Similar to [13][14][15][16][17][18][19], we consider a dense LWSN, in which more than one node can exist in each grade. Such a topology differs from strictly linear WSNs, e.g., [20,21], in which there exists only one line of nodes.…”

“…Previous works from multiple research groups, including ours, have proposed energyefficient MAC protocols that take advantage of the fact that in LWSN data packets flow hop by hop from the node where the sensory data are generated towards the sink node located at one end of the network [13][14][15][16][17][18][19][20][21]. Despite the relevance of these works, they only focus on improving the overall network performance at the expense of the high packet loss probability (PLP) experienced by the data packets that have to travel through multiple relay nodes before reaching the sink.…”