High-Level System Design of IEEE 802.11b Standard-Compliant Link Layer for MATLAB-Based SDR

Abstract

Software-defined radio (SDR) allows the 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 paper, our contribution is the design of a bidirectional transceiver that runs on the commonly used USRP platform and implemented in MATLAB using standard tools like MATLAB Coder and MEX to speed up the processing steps. We outline strategies on how to create a state-action-based design, wherein the same node switches between transmitter and receiver functions. Our design allows the optimal selection of the parameters toward meeting the timing requirements set forth by various processing blocks associated with a differential binary phase shift keying physical layer and CSMA/CA/ACK MAC layer, so that all the operations remain functionally compliant with the IEEE 802.11b standard for the 1 Mb/s specification. The code base of the system is enabled through the Communications System Toolbox and incorporates channel sensing and exponential random back-off for contention resolution. The current work provides an experimental testbed that enables the creation of new MAC protocols starting from the fundamental IEEE 802.11b standard. Our design approach guarantees consistent performance of the bi-directional link, and the three-node experimental results demonstrate the robustness of the system in mitigating packet collisions and enforcing fairness among nodes, making it a feasible framework in higher layer protocol design.

Keywords

• Software Defined Radio
• IEEE 802.11b
• CSMA/CA/ACK
• Energy Detection
• Exponential Random Back-off
• MEX