OPTIMAL POWER CONTROL LAW FOR MULTI-MEDIA MULTI-RATE CDMA SYSTEMS - Vehicular Technology Conference, 1996. 'Mobile Technology for the Human Race'., IEEE 46th

This paper considers the optimal reverselink power control law for multi-media multi-rate DS/CDMA systems which offer services with different transmission rates (VBR or CBR) and quality of service (Qos) requirements. In the multi-media multi-rate CDMA system, the transmission power of a mobile station (MS) is proportional to a power control law, which is a function of its distance to the base station (BS), the transmission rates and interference level (number of active users). Each transmitted signal from MS will be affected by path loss, Rayleigh fading and log-normal shadowing in the reverse link. Bit error probability of the asynchronous multi-rate CDMA system that takes MS locations into account is derived first in order to derive the optimum power control functions. By applying the optimal power control functions to mobile stations, the &os (bit error probability) requirements can be met, the system capacity (number of simultaneously transmitted users) can be maximized, and power consumptions can be minimized. Since the difficulty of deriving the optimal power control law in closed form, we discretize the power control function so that the dynamic programming (DP) can be utilized to obtain the optimal solution. The numerical results show that the optimal power control law can increase system capacity and decrease power consumption compared with other power control laws (eg. equal received bit energy) in the multi-media multi-rate CDMA system.