Poster: ContikiMAC, some critical issues with the CC2420 Radio

During experimental evaluations of RPL on a network with some 20 Zolertia Z1 motes running Contiki version 2.6, inconsistent Packet Delivery Ratios (PDR) and message latencies were frequently observed. Replacing ContikiMAC by NullRDC brought consistency, proving that the problem had to be found in the Radio Duty Cyling (RDC) protocol. Two implementation issues of ContikiMAC were found guilty. The first is the timing of the inter-packet interval related to the interval between two successive Clear Channel Assessment (CCA) probes. The second is the choice of the value of the CCA threshold. These issues will be analyzed in this poster, a satisfactory work-around has been implemented and some to be tested alternatives are proposed.