Cross-Layer Performance Analysis of Multiclass Services in a Multi-Time-Hopping PPM UWB System with Rake Receivers

A multi-time-hopping (MTH) binary pulse position modulation (PPM) ultra-wideband (UWB) system with Rake receivers is considered. Based on the system capacity, an admission scheme at the connection level is formulated to relate the number of multipath fingers to the number of different classes of users that can be supported and to the blocking probability of each class in the system. With this analytical framework, the minimum number of multipath fingers that are needed in the physical layer while maintaining prescribed outage probability requirements in the link layer and prescribed blocking probability requirements at the connection level in the network layer for each traffic class can be determined. The outage probability in terms of bit error rate specification, with Gaussian monocycles supporting variable bit rate (VBR) multiclass services, is presented. The analytical framework is formulated for the general case in which different traffic classes have different varying bit rates. Closed- form expressions for the signal at the correlator's output during a frame interval and the power of the interference resulting from one of the active time hopping sequences from the interfering users on one pulse are explicitly derived. The indoor channel model used is based on IEEE 802.15.3a.