Shanghai Bell Data Communication Cablelink 2000

Shanghai Bell Company's Cablelink Cable modem system provides high-speed asymmetric data communication services to users through the fiber coaxial hybrid network. The asymmetry of its connections requires high-speed communications in one direction, such as network browsing, Internet file transfer, and ideally in the opposite direction with a lower-rate delivery service. The TDMA access method used in Cablelink 2000 system can make the system more flexible when it is enlarged. On the front end, the Cablelink 2000 system and industry-standard router connections enable users ' computers to connect to local servers, WANs, and the Internet, which can connect to hubs, routers, and local servers through up to three 10BaseT two-way Ethernet interfaces. The 30Mbps data channel is available to the cable data modem when all is in use. A cable modem is an external device that is connected to a user's computer through an Ethernet adapter. The Shanghai Bell Cablelink 2000 system is fully compatible with the international MCNs standard. Cablelink 2000 system in the downlink using QAM modulation, uplink using QPSK modulation. Using these techniques, the downlink rate of the asymmetric cable modem system can be as high as 30Mbps and the uplink speed can reach 2.56Mbps. It includes a plurality of cable digital modems Cablelink cm2000d and one or more cable modem front-end system cablelinkhs2000d on the front end of the CATV. The hs2000d includes an RF modulation and demodulation module and a channel control module. The minimal configuration of the hs2000d can support approximately 2000 cm2000d. The whole system is very well expandable, and it is very convenient to increase the user.



　　



Cable modem Front-End System Cablelink hs2000d

The front-end unit includes a cable modem front-end system CMHS and a NMS for the network management system. Connected to a remote server or ISP via a switched hub (hub) with a local server and then through a router. It is actually the connecting device between hub and CATV network, and is responsible for maintaining the two-way communication of each cable modem through CATV network.

The Ethernet frame received from the router is encapsulated in the mpeg-ts frame and transmitted to the cable modem using the 64QAM modulation downlink. The QPSK modulation time slot received on uplink is then converted to Ethernet frame and transmitted to Internet access router. CMHS is also responsible for the management of cable modem corrections and the allocation of TDMA time slots to the cable modem.

Network management software NMS Cablelink nms2000d

The network management software of the asymmetric data modem system runs on the Windows95 platform and connects with the PC through a RS232 port.

Its main functions include:

Management of cable data modems.

Remote status monitoring of all CMHS front-end and cable modems.

Remote configuration and control of all CMHS front-end and cable modems.

SNMP managers are used to control such things as routers, local servers, and so on.

The NMS calculates the system frame or time slot error rate by mpeg2-ts the downlink frame count. Each modem maintains the number of TDMA slots received and not received in the time slot sent according to the signaling information in the downlink frame.

Cable modem client Cablelink cm2000d

The client includes cable Modem, user PC with standard 10BaseT Ethernet card and internet browsing software. Cable modem is used to connect the user's PC to the CATV network. It maintains the two-way communication between the user card and the front-end CMHS. Signals received from CMHS are demodulated and converted to Ethernet frames, which are then passed to the user's network card. Cable Modem adopts the media access control (MAC) process based on TDMA to access uplink transmission channel, and the transmission power and time synchronization are adjusted by constant correction.