Optimization and verification of the TR-MAC protocol for wireless sensor networks

Energy-efficiency is an important requirement in the design of communication protocols for wireless sensor networks (WSN). TR-MAC is an energy-efficient medium access control (MAC) layer protocol for low power WSN that exploits transmitted-reference (TR) modulation in the physical layer. The underlying TR modulation in TR-MAC provides faster synchronization and signal acquisition without requiring channel estimation and complex rake receiver in the receiver side. TR modulation also enables multiple access for a pair of nodes using different frequency offsets. This paper introduces an explicit expression that allows the TR-MAC protocol to minimize its energy consumption, depending on the experienced traffic load. Furthermore, an implementation of the protocol in the OMNeT++ simulator with MiXiM simulation framework is introduced, and analytical results introduced in [13] are verified by simulation results obtained using the simulator

A multi-channel multiple access scheme using frequency offsets — Modelling and analysis

A system using frequency offset based transmit- reference (TR) modulation allows multiple nodes to transmit simultaneously and asynchronously without any mutual timing coordination. Thus, such a system provides inherent capabilities for a multiple access in the medium access control (MAC) layer to coordinate the shared use of the common wireless medium among the nodes of the wireless sensor network (WSN). However, certain characteristics of a frequency offset based system limits its performance, for example, the number of available frequency offsets is limited as it depends on several system parameters, and the number of simultaneous communications using different frequency offsets is limited due to inter-user interference. In this paper, we introduce an extended version of the performance model of a basic slotted- Aloha system, that captures the basic phenomena of a multi- channel system with a limited set of channels and a limit to the number of simultaneously used channels. An analysis of this model reveals the potential of a MAC protocol for TR modulation with frequency offsets