Enhancing the gsm voice capacity using orthogonal sub channel (osc) technique in downlink transmission

This paper presents a study of the voice services usage over Adaptive Multi-user channels on One Slot (VAMOS) for improving the voice capacity. VAMOS is an extension of the Global System for Mobile Communications (GSM) standard to enable the transmission of two GSM voice streams on the same radio resource using Orthogonal Sub Channel (OSC) technique for doubling the number of users served by one cell. The concept of VAMOS is based on multiplexing two or more users at one time slot. Therefore, it is a subject for this paper to consider the downlink transmission of GSM VAMOS systems. In this paper the feed forward transversal filter estimator is used for channel estimation. Furthermore, different values for Alpha in Alpha QPSK modulation are used to notice the performance of VAMOS system. In the downlink at each mobile station the channel coefficients and the sub-channel power imbalance ratio (SCPIR) are estimated. General Terms: Improving voice capacity for GSM networks.