The Research Of PSTN-LAN Gateway Based On FPGA And ARM

With the rapid development of information technology, transport networks, as the carrier of information, are going to combine each other when they become stronger. Many new technologies appear, which integrate the advantages of each transport networks, and provide service between them. It's in the great demands to realize the intercommunication between PSTN and LAN, which can make good use of the network resource. So the The Research of PSTN-LAN gateway is very important.With the research and compare of the present equipments and technique paths, A custom voice data encapsulation mode is proposed according to the practical applications of PSTN-LAN gateway in LAN.Furthermore, the technique solution is designed and implemented, deploying FPGA and embedded system based on ARM, to achieve network communication between PSTN with LAN.The voice data encapsulation policy is that MAC address is acted as addressing object when voice data is encapsulated; network interface is directly drived to receive/send voice data packet by system, through which redundant IP header is wiped off; compressing algorithm for voice data is not adopted during encapsulation to avoid long additional time delay.The low-cost FPGA is adopted to implement communication interface to PSTN, primarily including encode/decode module for El line, distilling and inserting voice data in time slot, resolving strict time-control problem required by constant bit rate line and achieving high processing speed. Ethernet communication interface adopts micro-processor of ARM kernel S3C4510B and embedded OS uClinux.The encapsulation of data under voice into Ethernet MAC data packet is complete According to Ethernet standard protocol,and it extends system management functions and application in high layer.The scheme proposed in this thesis predigests voice processing policy, syncretizes two current developing techniques, which is of some theory value.