Analysis of UMTS radio channel access delay

We present an analysis of delay encountered in successfully accessing the Random Access Channel (RACH) of Universal Mobile Telecommunication System (UMTS) Radio Interface by User Equipments (UE) that want to initiate data transfer. The process of random channel access is described and the MS state modeled as a DTMC in order to derive the delay. We evaluate the variation of the channel access delay with the preamble power, preamble detection threshold, maximum attempts, inter-attempt time interval, number of mobile users, number of slots, persistence level, rate of incoming data and rate of retransmissions. We also derive the capture probability of preambles sent in the same slot by multiple UEs in the presence of Rayleigh fading.