Transmitted reference modulation for TR-MAC protocol

Transmitted reference modulation for TR-MAC protocol

Low-power wireless sensor devices have gained popularity in past decade. These low-power devices have to deploy an efficient medium access control protocol together with an efficient modulation technique in the underlying physical layer to enable low power operation. Transmitted reference (TR) modulation is such a low-power spread-spectrum technique where the transmitter sends the unmodulated carrier signal together with the modulated signal in the wireless medium separated by a frequency offset already known to the receiver. The receiver restores the original signal using the known frequency offset by performing self-correlation with the frequency-shifted version of the same signal. Hence the receiver enjoys faster synchronization with reduced signal acquisition time without the need of a complex rake receiver or channel estimation or power-hungry stable oscillators. Moreover, multiple frequency offsets using TR modulation can provide implicit addressing as link identifiers. As a result, the TR modulation with its simplified receiver architecture enabling low power, low data rate and low duty cycle operations provides more flexibility to the upper MAC layer for WSNs. However, the transmitter using TR modulation consumes more power than a general modulation technique to transmit individual bits since the reference signal is also sent.

The DACS group is working on one such MAC layer protocol under the WALNUT project - which aims to design an energy-efficient MAC layer protocol called TR-MAC suitable for TR modulation. The TR-MAC protocol has already been proposed and partially implemented using OMNeT++ simulator using MiXiM simulation framework. OMNeT++ is a C++ based extensible, modular and component-based discrete event simulator that enables analyzing a protocol by means of events occurring at discrete time instances. And MiXiM framework provides some example protocol stacks for all the layers of the OSI model. The TR modulation technique has been studied in detail by the TE group and a working implementation in Matlab is already available.

Goal of the assignment

The task of the student would be to implement the operating characteristics of transmitted reference modulation in the OMNeT++ simulator using MiXiM simulation framework to be compatible with TR-MAC protocol. The student need to have working knowledge about C++ and Matlab.