PaderMAC: A Low-Power, Low-Latency MAC Layer with Opportunistic Forwarding Support for Wireless Sensor Networks

Abstract. Modern medium access control (MAC) protocols for wire-less sensor networks (WSN) focus on energy-efficiency by switching a node’s radio on only when necessary. This intoduced rendezvous prob-lem is gracefully handled by modern asynchronous approaches to WSN MAC’s, e.g. X-MAC, using strobed preambles. Nevertheless, most MAC layer ignore the possible benefits in energy consumption and end-to-end latency, supporting opportunistic routing can provide. In this paper we present PaderMAC, a strobed preamble MAC layer which supports cross-layer integration with an arbitrary opportunistic routing layer. This work specifies the PaderMAC protocol, explains its implementation using TinyOS and the MAC layer architecture (MLA), and presents the results of a testbed performance study. The study compares PaderMAC in con-junction with opportunistic routing to X-MAC in conjunction with path-based routing and shows how PaderMAC reduces the preamble length, better balances the load and further improves the end-to-end latency within the network.

Efficient Vector-Based Forwarding for Underwater Sensor Networks

Underwater Sensor Networks (UWSNs) are significantly different from terrestrial sensor networks in the following aspects: low bandwidth, high latency, node mobility, high error probability, and 3-dimensional space. These new features bring many challenges to the network protocol design of UWSNs. In this paper, we tackle one fundamental problem in UWSNs: robust, scalable, and energy efficient routing. We propose vector-based forwarding (VBF), a geographic routing protocol. In VBF, the forwarding path is guided by a vector from the source to the target, no state information is required on the sensor nodes, and only a small fraction of the nodes is involved in routing. To improve the robustness, packets are forwarded in redundant and interleaved paths. Further, a localized and distributed self-adaptation algorithm allows the nodes to reduce energy consumption by discarding redundant packets. VBF performs well in dense networks. For sparse networks, we propose a hop-by-hop vector-based forwarding (HH-VBF) protocol, which adapts the vector-based approach at every hop. We evaluate the performance of VBF and HH-VBF through extensive simulations. The simulation results show that VBF achieves high packet delivery ratio and energy efficiency in dense networks and HH-VBF has high packet delivery ratio even in sparse networks