Differences and connection between ADSL and Cable Modem

Both ADSL and Cable Modem technology groups can provide a variety of services and meet the needs of current broadband services. The bandwidth of ADSL is lower than that of Cable Modem. However, the stability, reliability, power supply, and operation and maintenance systems of the Network Using Cable Modem and HFCs all have some problems. In addition, because the bandwidth of the network line is shared, after a user reaches a certain scale, it is actually unable to provide broadband data services, and the bandwidth shared by the user is very limited. The two technologies are compared below.

Security. Because all user signals of Cable Modem are transmitted on the same coaxial Cable, there is a risk of wire eavesdropping. (There will be a fatal defect in implementing e-commerce in the future) to solve the problem of wire eavesdropping, we should first protect the cables, and secondly, we should understand the set parameters established during the line initialization process, the latter is technically hard to solve. But ADSL does not have this problem.

Reliability. Because CATV is a tree-like network, it is very easy to cause single point of failure, such as cable damage, amplifier failure, and Transmitter failure, which will cause the interruption of user services on the entire node. ADSL uses a star network. The fault of an ADSL device only affects one user.

Stability. Early users of Cable Modem can enjoy excellent services, because the bandwidth and frequency band of the line are abundant when there are few users. However, the addition of each Cable Modem user will increase noise, occupy channels, reduce reliability, and affect the existing user service quality on the road. This will be a major challenge that Cable Modem urgently needs to solve. ADSL will not be affected by the number of users and traffic in the access network. Of course, if the egress bandwidth of DSLAM is smaller than the total bandwidth that all users may need, there will be congestion during peak hours, but this problem can be solved by increasing the egress bandwidth.

Compatibility. Although both Cable Modem and ADSL have introduced technical specifications and standards, the products of different manufacturers are not compatible yet, which brings difficulties to the market expansion.

Networking costs. In terms of networking costs, the cost of ADSL equipment is obviously higher than that of Cable Modem, but the latter must be applied only after the transformation of HFCs is completed. At present, most of China's HFCs can only meet the bandwidth requirements of 450MHz, while the two-way service provided by HFCs requires at least MHz of bandwidth. This clearly requires replacement of all non-conforming coaxial cables. At the same time, to achieve two-way HFCs, You need to replace the one-way amplifier currently used on the cable TV network. This part of the transformation cost is also quite high.

In fact, the biggest advantage of using a telecom network to access the INTERNET is not the speed of user access, but the speed at which users access websites. The use of some network providers that claim to have 10 m access speed to the INTERNET may start due to a small number of users, the speed is acceptable, but as the number of users increases, the speed will decrease quickly or enjoy the services of its own network, but the access speed to many well-known sites is slower than that of MODEM. In this sense, it is just a large LAN, not a wide area network. China Telecom is proud to be proud of its full-process network. It occupies more than 90% of the country's outbound bandwidth and will continue to expand. The Provincial Trunk Lines will also reach all directions, connecting to the INTERNET through a telecom network is your best choice.

Related Articles]

• ADSL Technology Zone

• Development and Application of ADSL Technology