Study Of Smart Phones Voice Communication System Based On Wrieless Ad Hoc Networks

As a kind of non-center, multi-hop and self-organizing network, Ad Hoc is suitable for the emergency requirements of communications, which has broad application prospects. In recent years, mobile phones have developed rapidly in many kinds of applications. The mobile phones become more intelligent and diversiform, and turn into an indispensable part of daily life. In order to meet the communication demands anytime and anywhere, combined with the rapidly developed VoIP technology, this thesis proposes to use the phone to set up Ad hoc networks for voice communications, not only to meet the communication in case of emergency needs, but also to save the voice communication costs, which can provide communication service more convenient and practical.Different from traditional wired networks, the wireless ad hoc networks have many problems in voice communication using VoIP technology, which communication quality is the focus of our attention. In this paper, we analyze the relevant technologies used in the system, including characteristics of the ad hoc networks, the voice coding technology used in VoIP and real-time transmission technology. Our work concentrates on the study and improvement of wireless self-organizing network routing protocols and voice encoding scheme. And the linguistic quality evaluation standards are introduced in this thesis.Firstly, due to the random variation of link status of the wireless self-organizing network which would seriously affect the quality of voice calls, we analyze voice encoding technologies for voice communications and propose a self-adapting voice coding solution. The destination node calculates the end-to-end packet delay, jitter, packet loss ratio periodically, and determines the network load conditions by metering the network parameters, then sends the results periodically to the source node. The source node selects coding scheme adaptively according to the feedback of network status. The encoding solution of low compression rate is selected when the network condition is good, and the low-rate voice coding solution is selected when congestion happens. It’s helpful to improve call service quality of the entire network by considering the two aspects of network load and voice quality.When we set up ad hoc network by mobile phones, the energy issues of the entire network must be consider because of the limit of phone battery. In this thesis, EP-AODV, an energy-saving strategy of routing in wireless ad hoc networks, is proposed on the basis of the AODV.The protocol considers the node’s lifetime and the total energy cost. In path selection, the path which has longer lifetime and less energy cost should be selected, by which to reduce the network delay, jitter and packet loss rate and improve the overall performance of the network. Meanwhile, the feedback model of network status is added to the routing protocols in order to complete the periodic feedback of network conditions.The improved EP-AODV protocol is simulated with NS-2 in this paper, and a result compare to the AODV protocol is conducted. The analysis of the simulation results proves that the improved routing algorithm is better to extend the network life cycle and reduce network energy consumption. According to the simulation results, a framework of the mobile voice communication system is designed based on the ad hoc networks. Meanwhile, the thesis also introduces the hierarchical structure of the network, the process of voice communication, the functional partition of system module and the process of communication. In the end, some of the features are realized on the Android platform.