| There has been unprecedented progress in VoIP technologies in recent years, and many telecom service providers have investigated in projects related with VoIP technologies. Their purpose is to transmit traditional analog voice signals via current IP-centric networks, because of the convenience and low-cost of IP-centric networks. Among the majority of their implementation, media access gateway(AMG) plays a very important role. It transforms the PSTN data frame format into IP packet format, and it also translate the switch signaling and protocols. The project described in this paper originates from a research project "AMG SYS6K" from Harbour Networks Inc.SYS6K implements the packet voice processing module(PVM), access manage unit(AMU) and analog line unit(ALU) to provide common telephone service access, voice coding/decoding and packet framing, and connect to uplink convergence devices or the IP-centric networks via 100M LAN ports. PVM is an optional function module located in AMU.This paper focuses on the hardware design and implementation of the packet voice processing module(PVM) within SYS6K. A brief introduction on VoIP core technologies has been presented. Although more emphasis is put on the circuit design rather than the related VoIP protocols, a survey on the parameters related with chip selection has been conducted. The design in detail includes overall project design, chip selection, related circuit design, board structure design, PCB layout design, etc. This paper concentrates on the detailed analysis on the core chips for voice coding/decoding and packet framing. Moreover, an analysis in detail on the hardware driver program and the quality of the actually tested signals has been conducted.Due to intelligence properties, the circuit design and PCB layout will not be described in further details here in this paper. However, detailed description on the implementation theories and practical application of the board have been discussed in this paper. |
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