A Beacon-Aware Device For The Interconnection of Zig Bee Networks

Sensor networks based on the IEEE 802.15.4 standard are simple and low-cost. The IEEE 802.15.4 standard provides two modes of connections : beacon enabled mode and non-beacon enabled mode. The beacon enabled mode can offer a transmission determinism thanks to Guaranteed Time Slots (GTSs). The non-beacon enabled mode does not offer any guarantee on traffic determinism. Contrary to the non-beacon enabled mode, the beacon enabled mode does not allow us to form mesh topology in order to interconnect several beacon networks. The current solution to interconnect beacon networks is to use a mesh network made of non-beacon devices that can compromise the determinism of GTSs. In this paper, the notion of “beacon-aware” device is introduced. A beacon aware device acts as an interface between an in range beacon network and a mesh network. Unlike a non-beacon device, a beacon aware device gives priority to the in range beacon traffic, in order to avoid any perturbations of the beacon traffic. This priority is obtained with a modification of the slotted CSMA/CA algorithm, implemented on the beacon aware device. The beacon aware uses a modified CSMA/CA to send traffics issued from a mesh network having for destination in range beacon devices. The beacon aware device uses the simple CSMA/CA algorithm (unslotted version) otherwise.