PERFORMANCE STUDY AND CAPACITY ANALYSIS OF A TWO-TIER CDMA SYSTEM

Electronics and Communications Engineering Department, Faculty of Engineering, Mansoura

University, Mansoura, EGYPT

One of the main factors that affects the performance of a Code Division Multiple Access

(CDMA) system is the out of-cell interference. While the in-cell interference is controlled

within each cell using a power control algorithm, the out of -cell interference is not and can

greatly impact network coverage and the total user capacity, so that CDMA capacity is an

interference limited capacity. One design technique to reduce the effect of the out of-cell

interference in cellular CDMA systems is to use cells of different radii, hierarchically

organized in overlapping layers, this is the multitier system. In this paper the user capacity on

the reverse link direction of a certain two-tier CDMA system that consists of a small

microcell embedded in a larger macrocell, i.e. a two cell system is examined. The effect of the

users' mobility on the call blocking and call dropping probability is examined depending on

the system feasibility. With the proposed scheme for forced call termination the simulation

results show that at different call arrival rates the system capacity is increased. The results are

satisfactory as compared with the previous work where stationary users were assumed. The

dominant parameters affecting the system performance are the users' velocity and the distance

between the two cells.