Towards better understanding of the behaviour of Bluetooth networks distributed algorithms

摘要

The use of frequency hopping spread spectrum in Bluetooth significantly differentiates its networks from classical radio networks. In order to observe such differences, we studied basic algorithms, in particular neighbour discovery and message exchange algorithms. Some of the major differences are found in the procedures of device discovery and link establishment, which are studied in this paper. We focus on their impact on Bluetooth networks' distributed algorithms. We show through detailed simulation experiments that minor modifications to the Bluetooth specifications or their implementation may significantly affect the performance of well-known neighbour discovery algorithms. We then study the impact of the procedures of link establishment with the purpose of finding time-efficient implementations of communication rounds for Bluetooth networks. We study OrderedExchange and RandomExchange as both algorithms implement communication rounds in Bluetooth, but use the PAGE and PAGE SCAN states differently. Theoretical analysis shows that RandomExchange has a better time complexity, while simulation experiments show that OrderedExchange significantly outperforms RandomExchange in networks with a practical size (110 nodes and less). We use the previous results to improve the time efficiency of Bluetooth scatternet formation algorithms through the introduction of the time-efficient algorithm OrderedExchangeCMIS. We believe that the study of some other basic algorithms (such as broadcasting, spanningtree and election) will lead to a better understanding of Bluetooth networks, and as a consequence, to more efficient algorithms that fully leverage the strength of this type of network.