Link Layer Design and Implementation for Software Defined Radios (June 2012 - Jan 2016)
The link layer, with its main functionality of regulating channel access, is a critical component of a communication network. It ensures fair transmission opportunities in a distributed environment through its medium access control (MAC) protocol, ensures correct packet delivery to the next hop, and facilitates coordination and control exchange among the neighboring nodes.
The advent of flexible software defined radio platforms (SDRs) has enabled fine-grained and adaptive control over the various functions of the link and physical protocol stack layers. Thus, transmission power, frequency, error correcting codes, packet scheduling, data rate, modulation, among others, can be varied based on the specific environment in which the radio operates. As the underlying hardware gets more powerful, these different degrees of freedom regarding transmission parameters contribute towards an increasing search space, from which, the optimal configuration of the radio must be chosen. The end-user prefers transparent operation of the device, thereby delegating the task of adapting these parameters to an intelligent link layer. The objectives of the proposed research are as follows:
- To understand and address the challenges in implementing an adaptive link layer for SDRs, and proposing a 802.11-like medium access control (MAC) protocol design that is sensitive to timing and synchronization concerns within the SDRs
- To integrate optimization strategies in the design that allow the link layer to respond to external sources of interference and other channel-induced effects
- To identify the time-critical building blocks of the MAC protocol and explore how to speed up the processing by exploring parallelism, using standard tools like the MATLAB Coder and MEX, and studying the tradeoffs between communication and computation costs.