Department: Electronic And Computer Engineering
Ufoaroh, S. U.
The need for high performance and improved Quality of Service (QoS) in wireless mobile communication system such as Wideband Code Division Multiple Access (WCDMA) has been increasing exponentially in the last decade. This is because of the user mobility and flexibility particularly on the communication link between the mobile terminals and the base stations (otherwise known as the uplink) which cannot be provided in wired line communication system.This complexity in the cellular system periodically contributes to different interference levels, high or low, resulting in the degradation of the system capacity. Transmitter power control (TPC) is an efficient technique to mitigate the effect of interference under fading conditions;it combats the Near-Far problem and conserves the battery life of mobile unit. Thus, aneffective implementation of power control algorithms in cellular radio communication systems offers a significant improvement in the Quality of Service (QoS) to all the users.In this work,an enhancement algorithm was developedon the existing adaptive power control algorithm based on the concept of hysteresis to mitigate oscillations observed at low outage probabilities in the existing adaptive power control algorithm.The algorithm was based on a modificationof the transmitted power update step size. Instead of thepresently implemented fixed value, the step size was modifieddynamically in order to guarantee more adapted powervariations.Simulationswere carried out in matlab platform using empirical measurements from existing WCDMA network in Onitsha, South-East Nigeria to verify the developed algorithm, “Modified Adaptive Power Control (MAPC) algorithm”. The MAPCcontrolled transmit power level of mobile station, which in turn improved the capacity of WCDMA mobile network.This improvement allows the WCDMA system to accommodate more users, thus achieving coverage extension, which is an improvement in the QoS of the network and also increased network capacity.When compared withAdaptive Step Power Control(ASPC), MAPC converge rapidly at 16th iteration, while the ASPC is still in outage even after 20 iterations. MAPC at an outage probability of 10-3 has about 83.61% active users, compare to Fixed Step Power Control (FSPC), Multiple Step Signal to Interference Ratio (SIR) Based Power Control(MSPC) and ASPC with 67.39%, 73.04%, and 76.09% active users respectively. Also Oscillations at low outage percentages have been mitigated using this modified Algorithm.