ATM over ADSL Technology

Asymmetric Digital user line ADSL technology is widely used by telecom network operators, telecom equipment manufacturers, and semiconductor chip developers as a solution for broadband access. As a technology based on twisted pair copper wires, ADSL can transmit downlink 8 Mb/s data at a rate of 640kb/s on a pair of twisted pair wires. The transmission distance can reach more than 2km, this overcomes the bandwidth bottleneck for user access and achieves high-speed access for broadband users in the real sense. At the same time, it also has an incomparable advantage over broadband optical fiber access network.
As the end of the broadband network, the access network is closely integrated with the core network and the ATM technology, which is becoming an important trend in the development of ADSL. At present, the ITU-T, ANSI, ADSL forum, and ATM Forum are all closely concerned and are conducting research work on ATMoverADSL.
The following issues should be taken into account in the integration of ADSL and ATM technologies: flexibility. The combination of ADSL and ATM should ensure the flexibility to carry various high-level information, so as to provide users with various services flexibly; economy, the bandwidth and equipment price provided by ADSL to users should be fully taken into account in the combination of ADSL and ATM. According to the relationship between operation costs, the device price of ATMoverADSL is the key to the wide development of ADSL technology; scalability: the ATM-based ADSL system should be seamlessly connected to various service interfaces of the core network (such as ATM access switches and routers), so as to provide various users (such as ATM and IP addresses) provides high-speed access channels.
The Access Node consists of the ATM layer function module and the local ADSL Transceiver ATU-C array. The ATM layer function module maps ATM cells and ADSL frames in the downstream direction, and implements ATM addressing/demultiplexing, ing between ADSL frames and ATM cells in the uplink direction, and multiplexing/centralization of ATM code elements.
The broadband network terminal (B-NT) is composed of the ATM layer function module and the remote ADSL Transceiver ATU-R, the ATM layer function module maps/unmaps ADSL frames to ATM cells, and encapsulates/unencapsulates ATM cells in high-level protocols.
In an ATM environment, ADSL should support two types of applications: ATM cells to the desktop and LAN applications based on IP packets.
For the application of ATM cells to the desktop (ATM todesktop), The ADSL system is completely transparent to the ATM cells. For the ATM end-to-end system, the network should support PVC and SVC. For SVC mode, the ADSL system can adopt the signaling tunnel mode, that is, ADSL transparently transmits user signaling to the ATM switch without any processing. The ADSL system should support various user signaling capabilities such as ATMFUNI3.0/3.1/4.0 and Q.2931, and ensure the implementation of various QoS-related ATM services such as CBR, rtVBR, VBR, UBR, and ABR.