Beacon Advertising in an IEEE 802.15.4e TSCH Network for Space Launch Vehicles
Résumé
In space launch vehicles, a NASA study shows that the mass per channel of 0.45 kg for a wiring approach can be reduced to 0.09 kg for a wireless approach. 8 A question arises: which wireless technology is able to meet the requirements of space launch vehicles in terms of latency, throughput and robustness. The IEEE 802.15.4e amendment has been designed to meet such requirements. More specifically, the Time Slotted Channel Hopping (TSCH) mode has been designed for industrial automation, process control and equipment monitoring. It supports multichannel and multihop communications and uses a slotted medium access on several channels. In this paper, we focus on the time needed by a joining node to detect beacons advertising the TSCH network. An Enhanced beacon is a TSCH frame that contains information on synchronization, channel hopping and timeslot used in the advertised network. However, the advertising policy is left unspecified by the IEEE 802.15.4e standard and is under the responsibility of a layer upper than the MAC one. Since beacons are broadcast, they are lost in case of collisions: the vital information they carry is lost. The main problem is how to avoid collisions between two devices that are not neighbors. In this paper, we propose a Deterministic Beacon Advertising Algorithm, called DBA. The goal of DBA is to ensure that beacons are transmitted on all frequencies used by the TSCH network, regularly and without collision. With DBA, the exact value for the maximum time for a joining node to detect a beacon can be computed easily. We use the NS3 Simulator to evaluate this time as well as the the number of message losses, considering different network topologies (star or multihop). We compare the performance of DBA with this of two algorithms existing in the state of the art.
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