Research On The Key Technologies Of Trunking Duplex Voice Communication Based On Mobile Terminals In WLAN

In traditional trunking communication system, people carry on simplex or half duplex communication in a specific frequency band using walkie talkie. This communication mode not only occupies the precious frequency resource, but also requires heavy radio device, which is really inconvenient. Due to the low effi-ciency, it doesn't match the requirements of real-time communication. Meanwhile, with the development of network communication technologies, especially VoIP, people can conveniently realize voice communication at a low cost. In this paper, a new way to construct a trunking communication system based on smart phones and free WiFi is proposed.Based on the construction.a method to optimize the system resource allocation is implemented.And after discussing the multi-thread model and reactor model,a combination of the two event handling mechanism is provided.This paper proposes a new scheme to fast construct trunking duplex voice communication system in WLAN. Here all modules are highly reusable. The scheme is based on C/S model, following the hierarchical design principles, organizing user interaction, data transmission, data storage, access control, resource allo-cation, speech synthesis to complete the system. All the modules are loosely coupled in order to ensure the system a stable and reusable architecture, which can be easily extended.Acoustic echo cancellation is always required in a voice communication system. When transplanting the AEC module to a trunking communication system, the problem of synchronization of near end and far end signals at different threads needs to be solved. Therefore, a signal synchronization method based on SessionId is realized, which ensures the normal operation of the AEC module.To optimize the resource allocation in the situation of users'dynamic access and exit, an allocation s-trategy based on cache is implemented. In trunking communication system, users access and exit the system dynamically, causing frequent distribution and destruction of data and processing resource, which is ex-tremely time consuming and results in user's access delay, which affects the user experience. To improve this situation, this paper implements a method, using an integer indexed list to cache the exiting user's resource. When a new user come to access, the server checks the list to see if there are available resources, if any, allocating directly to the user. This method not only speeds up the speed of users access to the system, but also avoids the frequent destruction and creation of the resources, which is conductive to the stable operation of the system.In addition, this paper introduces multi-thread model and reactor model respectively. To combine the advantages of the two event processing mechanism, a new combined model is provided. In the combined model, the system dynamically adjusts the mechanism to receive requests and handle events. Therefore, the system can ensure smooth data flow when there are fewer users, and timely access when there are more users.Through the test, the method to construct trunking duplex voice communication system in WLAN is convenient and effective. Users can access the server in high speed and low failure rate. The whole mecha-nism processes smoothly without any acoustic echo, which has high application value in certain fields.