A Reconfigurable Random Access MAC Implementation for Software Defined Radio Platforms

Wireless communications technology ranging from satellite communications to sensor networks has benefited from the development of flexible, SDR platforms. SDR is used for military applications in radio devices to reconfigure waveforms, frequency, and modulation schemes in both software and hardware to improve communication performance in harsh environments. In the commercial sector, SDRs are present in cellular infrastructure, where base stations can reconfigure operating parameters to meet specific cellular coverage goals. In response to these enhancements, industry leaders in cellular (such as Lucent, Nortel, and Motorola) have embraced the cost advantages of implementing SDRs in their cellular technology. In the future, there will be a need for more capable SDR platforms on inexpensive hardware that are able to balance work loads between several computational processing elements while minimizing power cost to accomplish multiple goals.

This thesis will present the development of a random access MAC protocol for the IRIS platform. An assessment of different SDR hardware and software platforms is conducted. From this assessment, we present several SDR technology requirements for networking research and discuss the impact of these requirements on future SDR platforms. As a consequence of these requirements, we choose the USRP family of SDR hardware and the IRIS software platform to develop our two random access MAC implementations: Aloha with Explicit ACK and Aloha with Implicit ACK. A point-to-point link was tested with our protocol and then this link was extended to a 3-hop (4 nodes) network. To improve our protocols' efficiency, we implemented carrier sensing on the FPGA of the USRP E100, an embedded SDR hardware platform. We also present simulations using OMNeT++ software to accompany our experimental data, and moreover, show how our protocol scales as more nodes are added to the network.