PERFORMANCE OF AUGMENTED GENERALIZED QUALITY BASED POWER CONTROL IN ' SOFT HANDOVER

Abstract

The control of transmit power has been recognized as an essential requirement in the design of CDMA systems. Power control allows for mobile users to share radio resources equitably and efficiently in a multi-cell environment, so there has been a increase in effort to design efficient power control techniques. Soft handover is implemented in CDMA systems as, the typical distance for frequency reuse is equal to 1, i.e. all the mobile terminals use the same frequency. This allows maintaining a communication active through more than one radio path, with different base stations, makes it possible to implement the handover procedure without any critical constraint. In downlink, the application of the soft handover procedure requires an increase in the number of connections in order to serve the same number of users in the system. During soft handover there is a need of power control algorithm that has a faster convergence rate. In this dissertation, the focus is on the downlink (from base Station to Mobile Station) power control in soft handover for CDMA systems. Convergence rate and outage probability are the critical parameters for an efficient power control algorithm. In this dissertation a new algorithm-Augmented Generalized Power Control (AGQBPA) is proposed which converges, faster than the existing power control algorithm for downlink. The fast convergence is achieved by modifying the early detection rule proposed earlier for the uplink. The modified early detection rule is implemented on the Quality Based Power Control Algorithm (QBPA). The proposed algorithm also exhibits better outage probability for multimedia traffic by using a removal policy based on ranking multimedia services according to their priority. The performance of the proposed algorithm is also evaluated under the effect of the soft handover. The parameters for which the performance is evaluated are the active set size, threshold for adding BS into the active set, and the downlink orthogonality factor. iii