Adaptive infrared time division multiple access (AIR TDMA) for an in-house wireless hybrid LAN

We present two versions of access methods that are TDMA variants for a network composed of a wired backbone and of infrared cells. This in-house network has been studied to make mobile stations communicate with fixed stations in an industrial context. The access to the wireless medium is managed by the distribution of time slots by a specific wired station that knows the distribution of the mobiles within the installation. The first variant of TDMA consists of grouping the cells into classes in such a way that all the cells of the same class could have access to the wireless channel during the same time slot. The right of access to the wireless medium is then distributed among those classes where at least one cell has a mobile in range. In the second method, time slots are distributed to cells that will actually use this slot to communicate with some mobiles. The originality of this method lies in the way it can adapt to the evolution of the mobiles position inside this cellular network. The simulation results presented allow us to compare the access frequency to the wireless channel. They show the advantages of the second method.