ATM-based TH-SSMA network for multimedia PCS

摘要

Personal communications services (PCS) promise to provide anvariety of information exchanges among users with any type of mobility,nat any time, in any place, through any available device. To achieve thisnambitious goal, two of the major challenges in the system design are:n(i) to provide a high-speed wireless subsystem with large capacity andnacceptable quality-of-service (QoS) and (ii) to design a networknarchitecture capable of supporting multimedia traffic and various kindsnof user mobility. A time-hopping spread-spectrum wireless communicationnsystem called ultra-wide bandwidth (UWB) radio is used to providencommunications that are low power, high data rate, fade resistant, andnrelatively shadow free in a dense multipath environment. Receiver-signalnprocessing of UWB radio is described, and performance of suchncommunications systems, in terms of multiple-access capability, isnestimated under ideal multiple-access channel conditions. A UWB-signalnpropagation experiment is performed using the bandwidth in excess of 1nGHz in a typical modern office building in order to characterize thenUWB-signal propagation channel. The experimental results demonstrate thenfeasibility of the UWB radio and its robustness in a dense multipathnenvironment. A ATM network is used as the backbone network due to itsnhigh bandwidth, fast switching capability, flexibility, andnwell-developed infrastructure. To minimize the impact caused by usernmobility on the system performance, a hierarchical network-controlnarchitecture is postulated. A wireless virtual circuit (WVC) concept isnproposed to improve the transmission efficiency and simplify the networkncontrol in the wireless subsystem. The key advantage of this networknarchitecture and WVC concept is that the handoff can be done locallynmost of the time, due to the localized behavior of PCS users