| 单词 | H channel (High-speed channel) |
| 释义 | H channel (High-speed channel) In the integrated service digital network (ISDN), a high-speed channel comprising multiple aggregated low-speed channels to accommodate bandwidth-intensive applications such as file transfer, videoconferencing, and high-quality audio. An H channel is formed of multiple bearer (B) channels bonded together in a primary rate access (PRA) or primary rate interface (PRI) frame in support of applications with bandwidth requirements that exceed the B channel rate of 64 kbps. The channels, once bonded, remain so end-to-end, from transmitter to receiver, through the ISDN network. The feature is known variously as multirate ISDN, Nx64, channel aggregation, and bonding. ISDN standards define H channels at the following levels: • H : An aggregate bit rate of 384 kbps, which is the equivalent of six B channels (6 × 64 kbps = 384 kbps). • H : A full DS-1, with no framing overhead.This channel is sensitive to the specifics of the DS-1 implementation. In a North American PRI implementation where non-facility associated signaling (NFAS) is in place, the aggregate bit rate is 1.536 Mbps, which is the equivalent of 24 B channels. In a European PRA implementation, H supports an aggregate bit rate of 1.920 Mbps, which is the 1 equivalent of 30 B channels. • H : An aggregate bit rate of 1.472 Mbps, which is the sum of the 23 B channels (23 × 64 kbps = 1.472 Mbps) in a baseline PRI implementation in which channel 24 is devoted to the D channel. H applies in North America and Japan, and is based on T1 and J-1, respectively. 10 • H : An aggregate bit rate of 1.536 Mbps, the sum of all 24 B channels for the North American and 11 Japanese versions, which is based on T1 and J-1, respectively. H relies on non-facility associated sig-11 naling (NFAS) to provide a D channel on an H facility for signaling and control. 10 • H : An aggregate bit rate of 1.920 Mbps, the sum of all 30 B channels for the European PRA, which 12 is based on E-1. See also bandwidth, B channel, bonding, channel, D channel, DS-1, E-1, frame, J-1, NFAS, overhead, PRA, PRI, and T1. |
| 随便看 |
|
科学参考收录了5291条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。