A NEW PROTOCOL TO DESIGN CELLULAR SYSTEMS WITH VARIABLE SPREADING FACTORS

الملخص

The emerging M-commerce (mobile +e-commerce) needs more support in operating systems in order to be successful over a wireless environment. The system needs to support a seamlessintegrati n to support voice, audio and conventional data. It should also support many users with guaranteed quality. In this paper, a new effective design protocol for Code Division Multiple Access(CDMA) mobile systems with Variable Spreading Factor (VSF) is presented, such that various Quality of Service (QoS) based on different traffic types can be provided. Increasing spreading factors can benefit the system because it will increase the desired signal strength linearly. The measured Bit Error Rate (BER) can be reduced 75 times with a long spreading factor. By taking advantage of this benefit, switching the spreading factors dynamically is proposed, based on the current load with multimedia traffic.These proposals are implemented in mobile and base stations, and the system performance measured. The results indicated that the proposed system can always maintain a desired quality forall voice connections.