State-Action Based Link Layer Design for IEEE 802.11b Compliant MATLAB-Based SDR

Abstract

Software defined radio (SDR) allows unprecedented levels of flexibility by transitioning the radio communication system from a rigid hardware platform to a more user-controlled software paradigm. However, it can still be time consuming to design and implement such SDRs as they typically require thorough knowledge of the operating environment and a careful tuning of the program. In this work, we describe a systems contribution and outline strategies on how to create a state-action based design in implementing the CSMA/CA/ACK MAC layer in MATLAB® that runs on the USRP® platform, a commonly used SDR. Our design allows optimal selection of the parameters so that all operations remain functionally compliant with the IEEE 802.11b standard (1Mbps specification). The code base of the system is enabled through the Communications System ToolboxTM and incorporates channel sensing and exponential random back-off for contention resolution. The current work provides a testbed to experiment with and enables creation of new MAC protocols starting from the fundamental IEEE 802.11b compliant standard. Our system design approach guarantees the consistent performance of the bi-directional link and we include the experimental results for the three node system to demonstrate the robustness of the MAC layer in mitigating packet collisions and enforcing fairness among nodes.