Research On MAC Layer Of IEEE 802.15.4 Multi-hop Network

IEEE 802.15.4 is a new protocol defined for LR-WPANs (low-rate wirelesspersonal area networks), which supports small, cheap, power-efficient devicesoperating on battery power in short range. The standard can be used in manyapplications such as home automation, industrial sensing and control, medicaltreatment, agriculture and so on. So it has good market outlook for numerous productsolutions.The standard 802.15.4 supports two topologies: the star topology network andthe mesh networking topology. Many researches have proved that the star topologyhas good performance. However, in many applications, the star topology is notsufficient. Compared to 802.15.4 network based on star topology, the multi-hop802.15.4 network has some shortcomings. In beacon enabled network, there areserious beacon collision problem. And the hidden terminal problem of 802.15.4non-beacon enabled network is not handled well in the multi-hop environment.According to beacon enabled network and non-beacon enabled network, twoalgorithms are proposed. In beacon enabled network, it is called beacon collisionavoidance algorithm. In non-beacon enabled network, it is called MARCHmechanism.Extensive NS2 simulations of Linux are used to verify the two proposedschemes. Since the two schemes can avoid the collisions mostly, the results show thatthe proposed schemes can solve the problem availably and can achieve much betterperformance and higher throughput than the previous standard.