The Quality Of Voice Service Guarantee In B3G System

Although 3G system can offer both voice and data services with higher transmission rate than 2G system, but it still can not meet the increasing number of users and more varied application demands. Therefore, the next generation of mobile communication system(B3G) should provide higher bandwidth and spectrum utilization. B3G mobile communication system is an all IP based network with 100Mbps peak transmission rate, which will achieve global seamless roaming and adaptive resources allocation. Because of the time varying feature of the wireless channel, B3G system will inevitably face frequency and time selective channel fading. To meet the QoS requirement of the B3G system, This paper adopts related technologies in physical and data link layer to solve the problems brought by high bit error rate in B3G system.Since voice service is the most fundamental application in B3G system, the research on the enhancement of the voice service performance in the IP network is very important for the B3G system. This paper proposed a new QoS control method of voice service. On one hand, it uses adaptive transmission strategy, such as AMC, power control, sub-carrier allocation and antenna selection, to realize the reliable transmission in physical layer. On the other hand, it adopts ARQ and RRM in the data link layer to control the time delay and jitter of voice services.This paper analyzed how the retransmission strategy of ARQ to the delay of the voice service, and determined the best retransmission time which will allow the highest packet error rate based on theoretical analysis and simulation results, which can guarantee the QoS of voice even in bad channel environment. Moreover, this paper also analyzed how the radio resource management strategy realized the QoS control of voice service through transmission rate adjustment and resource allocation strategy. The transmission rate adjustment and bandwidth allocation based on physical layer information can provide the best match of channel capacity and transmission rate. Together with limited retransmission of ARQ, B3G system can guarantee the QoS of voice service.