Energy-efficient medium access control for transmit reference modulation

A Wireless Sensor Network (WSN) consists of sensor nodes distributed across an area to collect and communicate information. Research in the field of WSNs became interesting in recent times because of the challenges and constraints these WSNs impose, e.g., limited available energy, achieve low complexity and low cost. These research challenges and the applications of WSNs require robust communication with low power consumption in the MAC layer, as well as in the physical layer. Transmit reference (TR) modulation in the physical layer offers a simple low power receiver architecture, achieves fast synchronization with short signal acquisition time, and provides multiple frequency offsets that can be used for multiple simultaneous communications.

The main contributions of this dissertation are motivated by the research question of how to design a medium access control protocol to exploit the features of the underlying transmit reference modulation to provide energy-efficiency, traffic-adaptive behavior, and robust medium access control in a shared wireless environment.

We introduce a new energy-efficient MAC protocol, called TR-MAC, which exploits the benefits of the TR modulation in the underlying physical layer, and minimizes its drawbacks. The analysis of this thesis improves the understanding of the frequency offset based transmit reference modulation, and proposes a medium access control protocol customized for this unique modulation technique, named as the TR-MAC protocol. The TR-MAC protocol exploits the fast synchronization capabilities of the underlying frequency offset based transmit reference modulation. Energy- efficiency is achieved in this TR-MAC protocol by using transceiver duty cycling mechanism and preamble sampling technique. Furthermore, this TR-MAC protocol achieves traffic-adaptive behavior while maintaining energy-efficiency by using a duty cycle adaptation algorithm. The multi-channel multiple access model using frequency offsets and the performance analysis of the TR-MAC protocol in a multiple access scenario show that the TR-MAC protocol together with frequency offset based TR modulation increases the throughput and efficiency of the system while maintaining energy-efficiency. The TR-MAC protocol is suitable for low data rate and low-duty-cycle sparse WSN scenarios, for example, monitoring and tracking applications.