Research And Implementation Of Mac Communication Mechanism To Support Voice Transmission Based On WSN

Increasing concern is paid on the wireless multi-media sensor networks since it not only possesses features of the traditional sensor networks like self-organization,selfmanagement,but also realizes the fine-grained,accurate information monitoring by bringing in multi-media information like audio and video.Wireless multi-media sensor networks have many problems to be solved, medium access control(MAC) protocol,which determines the use of the wireless channels,is one of the crucial factors for the design of the wireless multi-media sensor networks. Based on the idea of variable frame length,this paper proposes a MAC communication mechanism which supports the voice transmission to satisfy the demand for wireless voice communications.According to the characteristics of voice transmission,the quality of service(QoS) requirements for voice transmission were analyzed,the QoS quantitative indicators for evaluating the voice transmission were selected,and the performance of the MAC protocol was designed.As for the quality of the sevice and guarantee mechanism MAC layer QoS were analyzed and summarized too.Then the demand for wireless sensor networks which support voice transmission was analyzed.This paper presents a low-cost,low-power hardware platform for voice processing,providing a hardware foundation for running and testing MAC protocol.A MAC communication mechanism which supports the voice transmission(VTDMA) was designed in the paper.The protocol collects the time slot allocation information within two hop neighborhood by using greedy algorithm for slot selection,and reserves time slot by REQ-REP-ACK mechanism. The frame length can be expanded or shrinked dynamically by the number of nodes within two hop neighborhood during the call,which can achieve the good utilization of the channels,reduce delays and improve throughput.According to the characteristics of high requirements of the real-time voice transmission.This protocol restricts the maximum frame length when it extensions,ensuring to meet the delay requirements. An one reservation-multiple transmission mechanism was designed,thus reduced the transmission of control messages, and further improved the throughput.And the performances of the protocol were analyzed theoretically.Finally,simulation and practical test for the MAC protocol were carried on.The results demonstrated that the QoS quantitative indicators of V-TDMA can meet the QoS requirements for voice communication,which achieved an excellent performance for voice communication.