ATM was never designed with wireless mobile applications in mind. Indeed the procedure of setting up connections is still on inheritance of the circuit-switching technology even of it has been optimized to the maximum, to reduce the switching overhead associated with the POTS. Studies have been performed on different algorithms that integrate mobile wireless application and more specially that HO. Indeed, one could be inspired by the actual mobile principles and keep a centralized track of the topology of the network, also requiring special switches (roots) that can deal with nobility requirements. The root would then reserve resources for every leaf (Virtual Connection Tree). Another would useful meshing between the access points and enhanced switches called anchor points. It is obvious that this procedure cannot be sealed to large networks.
|Medical Consulting User Trial|
The most promising protocol investigated at K.U. Leuben in detail is the Lcaf Initiated join (LIJ) HO concept. In this case, only the mobile terminals and the mobile BSS need a specific radio interface. This is based on the UNO 4.0 protocol, which is originally implemented to minimize bandwidth requirements for multicast (or point-to-multipoint) connections (late join source route trees). There, a leaf can request to join the tree, without any intervention of any centralized root or anchor point. The different possibilities of HO are investigated and compared (e.g. forward) backward, soft, hard), from the viewpoint of recovering the order of the cells and the delays involved. All options are only making use of the LIJ capabilities of the switches. Simulations on 60 GH2 and 155 Megabits data rate show that QOS can be maintained using standard buffers (with delays less than 1 ms in a71 percent load situation)[TDVV99]. The delay was essentially due to the number of switches between the branches, and not the size of the packets, further work, which is performed within the framework of the [NEDIANACTS] project and also supported by the network technologies programme of the Flemish governments, is focusing on the release algorithms for the worm connections, as well as more complex traffic configurations than a mere HO.