New Capacity-Expanding Technology Of Circuit Service Based On GSM Investigation For VAMOS

GSM(Global System for Mobile Communications) is the second generation of digital mobile communication system. It is based on narrowband Time Division Multiple Access technology(TDMA) which allows 8 groups of phone calls at the same time under one radio frequency. With its large capacity, flexibility to provide voice service and other technical characteristics, GSM has become the most successful mobile communication system that is for commercial use. Since its advent in 1991,GSM has owned a huge user base, coverage, spectrum and improved network infrastructure.Though LTE(Long Term Evolution) is being widely deployed worldwide with its spectral efficiency, high speed and the excellent support to data service, it still can’t support the voice service efficiently today. Since GSM can support the voice service perfectly, the question that how to improve the current system in order to make it carry more voice service increase the usage of spectrum more effectively and expand the system capacity of GSM network is always the top topic of research at home and abroad.The current methods of capacity expansion such as cell splitting, half rate and the adaptive multi-rate speech coding are all based on single-slot single-user system and have the problem of the less efficient wireless channel. VAMOS (Voice services over Adaptive Multi-user channels on One Slot) is a new idea for GSM network expansion. This paper focuses on the research in VAMOS technology’s application to GSM system. By improving the existing downstream modulated process in voice service mode, introducing a new low-level associated training sequence and other technologies, the quality of the network is transformed into the network capacity which allows the reusing one slot for two uplink and downlink voice users. At the same time, through the use of non-equilibrium power allocation, joint-power control and other technologies, the problem of voice quality degradation has been reduced caused by the introduction of VAMOS. So the acceptable voice quality is ensured on the premise that the system voice capacity is multiplied.This article provides the theoretical analysis and experimental result of the key technology-wireless resource allocation and power control in VAMOS. The experimental result shows that after the introduction of VAMOS, the GSM voice capacity has increased by 100% which gives a basis for the implementation and promotions of VAMOS technology in the GSM network.