Performance analysis of slotted aloha based cellular access networks with different stabilization schemes

Abstract

This thesis work is concerned with the performance analysis of slotted Aloha based various generations cellular access networks such as GSM (2G), GPRS (2G+) and WCDMA (3G). Slotted Aloha is the most primary and simplest protocol for uplink access technique. In this work computer simulation. is carried. out to study the channel behavior of a slotted Aloha based random access channel employing diffcrcnt performancc optimization schcmes to improve the stability, carrier sensing capability, collision detection techniques and capacity etc. of such a system. The combined effcCt of capture and retransmission algorithm on the stability and all various quality parameters, such as system throughput, maximum allowable new and gross traFfic, access delay, rejection probability etc. have been formulatcd in this work. Optimum values of different system parameters for a slotted Aloha based random access scheme have been determined .Various performance improvement techniques are also analyzed to find the optimum QoS parameters by maintaining a stable radio access system. Different network parameters are also evaluated for both finite and infinite users cases. The impact of the number of RACH (Random Access Channel) slots has been analyzed on the performance of the GSM systems both in a low-capture and in no-capture environment. It has also been found that the performance in a low-capture environment is better than no-capture environment for both the GSM and GPRS standards. Further stable operation of random access procedure are also analyzed in a multi service based 3G WCDMA system. Suitable and appropriate power control schemes, power ramping, ramping steps, capture environment, signature choice procedures are chosen for different traffic classes to enhance the system performance. Various values of RACH (Random Access Channel) parameters are used for real and non-real time services to optimize the utilization of radio resource as well as to keep the system stable and appropriate RACH parameters are evaluated and the mechanism of controlling access load has been discussed considering finite and infinite users.