Research And Design Of Voice Gateway In Trunking System IP Networking

In recent years, the police departments had built their private computer network with the Golden Shield Project working in many provinces. So the trunking system can be connected in a province using their private computer network. In this way a roaming trunking system were built in a province. Comparing to the way of renting communication wire, the transmit network can be saved; the cost of communication can be decreased and the flexibility of networking can be promoted. Under this background, the paper was proposed as a node in trunking system IP networking.IP voice gateway is a node between the communication control unit and the server of trunking system in trunking system network. Its duty is digital compress coding and packetization of the voice in trunking system. It located on the edge of the network and accessed the trunking system into IP network from the kernel network angle. The analoge voice from the trunking system was PCM coded , compressed coded , packtized and then transmitted to the server by UDP/IP link in the voice gateway. On the other hand the voice packets from the server were transmitted to the trunking system in the converse process.The paper designed a gateway with dual processor architecture, which is PowerPC processor MPC852T and voice processor AC48304. The operating system and control program run on host processor MPC852T, the voice compress codec program run on the voice processor AC48304, they communication with the host port interface. In this way the voice compression can be worked timely and the flexiblity of the control program can be insured.In the paper , the embeded process platform and voice compression moudle were introduced firstly, then host port interface circuit was designed by which the host processor MPC852T communicated with AC48304. And then EM interface and ethernet interface of the gateway were designed ,which communicatewith trunking system and server respectively. Sencondly, the driver of voice processor AC48304 was developed on Huaheng embeded Linux platform. And then the signalling process and voice packet process program was developed on the platform. Finally, the problem of packetizatized voice transmission was analized...