A Low-Delay Routing-Integrated MAC Protocol for Wireless Sensor Networks

In this article, we propose a low-delay routing-integrated MAC (LDRI-MAC) protocol for wireless sensor networks (WSNs). In the LDRI-MAC protocol, we first assign a parameter termed as grade to each node. The grade of a node represents the minimum hop distance between the node and the sink. Then, we partition each node’s possible senders into disjoint sets (DSs) of size
$\alpha $
. We allow all
$\alpha $
nodes of a DS for data transmission in a cycle if a node of the DS succeeds in channel contention in the cycle. Thus, we allow
$\alpha -1$
nodes for data transmission even when they failed in channel contention in the same cycle. In this way, we reduce the channel access competition and the energy consumption in control overhead, overhearing, and idle listening. For performance evaluation, we develop a discrete-time Markov-chain (DTMC) model and drive closed-form expressions for packet delivery ratio (PDR), event-reporting delay
$(D)$
, and average energy consumption of a sensor node per received data packet at the sink (AEC). We also develop an algorithm to determine the value of
$\alpha $
that minimizes
$D$
. The results show that LDRI-MAC provides higher PDR, lower
$D$
, and greater energy efficiency, than H-MAC and JRAM protocols, in a multihop WSN.