Abstract
Wireless sensor networks (WSNs) have been used for environmental monitoring and reporting for many decades. Energy consumption is a significant research topic because wireless sensor nodes are battery-operated to be highly energy-constrained. Several strategies have been introduced in routing and MAC (Medium Access Control) layer protocols to facilitate energy saving. At the routing layer, an energy-efficient routing protocol, known as opportunistic routing (OR), has been designed to improve efficiency. OR achieves energy efficiency via load-balancing, which forwards packets along multiple routes over WSNs. At the MAC layer, an energy-efficient MAC protocol known as the asynchronous duty-cycled MAC (ADCM) protocol achieves energy saving by turning on and off a sensor node’s transmitter and receiver to eliminate unnecessary energy wastage. These protocols each have their own advantages and disadvantages. OR achieves energy efficiency at the routing layer but it raises an issue at the MAC layer. ADCM achieves energy efficiency at the MAC layer, but it hinders the packet forwarding efficiency of the OR. To attain better energy efficiency, a combination of these two ideas led to the development of OR with asynchronous duty-cycled MAC (OR-ADCM). However, even with better energy efficiency, limitations still exist in combining load-balancing and duty-cycling due to conflicts in the inherent properties of OR and ADCM. In this paper, we present a survey of the evolution of OR-ADCM over WSNs to help the reader better understand and appreciate the details of this tradeoff, which we hope will lead to the development of better protocol designs.
Highlights
Wireless communication has made huge contributions to modern technology and information communication
We present a survey of the evolution of opportunistic routing (OR)-asynchronous duty-cycled MAC (ADCM) over wireless sensor networks (WSNs) to help the reader better understand and appreciate the details of this tradeoff, which we hope will lead to the development of better protocol designs
We have discussed their main contributions and limitations regarding energy consumption; We have presented a literature review of opportunistic routing protocols and their evaluation, while explaining their base MAC mechanisms; We have focused on energy consumption, and have analyzed and compared the OR protocols based on their addressed challenges, deployed networks, base MAC functionalities, decision metrics, advantages and disadvantages
Summary
Wireless communication has made huge contributions to modern technology and information communication. We have highlighted the significant improvements made in the area of wireless sensor networks (WSNs) regarding the routing mechanisms underlying energy-constrained sensor nodes. The duty cycle [1] mechanism, which was introduced to reduce the energy consumption of sensor nodes, is arguably one of the greatest milestones in the development of WSNs. When one node performs packet transmission, other nodes in its neighborhood hold themselves from transmitting. Because our concern is in minimizing the energy consumption of sensor nodes, we consider traditional unicast routing to be too expensive for duty-cycled WSNs. In conventional unicast routing, nodes must wait for the destined node until it wakes up, which costs additional energy and time. We further describe the basic concepts underlying the opportunistic routing protocol, point out important issues related to opportunistic routing when applied to asynchronous WSNs, discuss recent advancements, and provide a comparison between these advancements
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