Basic rate interface

Basic rate interface

Basic rate interface (BRI, 2B+D, 2B1D) is an Integrated Services Digital Network (ISDN) configuration defined in the physical layer standard I.430 produced by the ITU. This configuration consists of two 64 kbit/s "bearer" channels (B channels) and one 16 kbit/s "data" channel (D channel). The B channels are used for voice or user data, and the D channel is used for any combination of: data, control/signalling and X.25 packet networking. The two B channels can be bonded together giving a total data rate of 128 kbit/s. BRI is the kind of ISDN interface most likely to be found in residential service.

The I.430 protocol defines 48-bit packets comprising 16 bits from the B1 channel, 16 bits from B2 channel, 4 bits from the D channel, and 12 bits used for synchronization purposes. These packets are sent at a rate of 4 kHz, giving the data rates listed above for a maximum possible throughput of 144 kbit/s.

Two modulation methods are used to deliver U-Interface signals over an ordinary copper pair: 2B1Q in North America, and 4B3T elsewhere.

2B1Q line coding

2B1Q coding is the standard used in North America. 2B1Q means that two bits are combined to form a single Quaternary line state (symbol). 2B1Q combines two bits at a time to be represented by one of four signal levels on the line. The signal rate, therefore, is 80 kilobaud and the line rate 160 Kbit/s. It operates with a maximum frequency range (bandwidth) of 40 kHz.

2B1Q coding is defined in ANSI T1.601 and ETR 080, Annex A. It can operate at distances up to about 18,000 feet (5.5 km) with loss up to 42 dB. An internal termination impedance of 135 ohms is presented to the line at each end of the U-interface. Echo cancellation techniques allow full-duplex operation on the line.

2B1Q transmission can be simply described as an amplitude modulation scheme for DC pulses.

4B3T line coding

4B3T is a standard used in Europe and elsewhere in the world. 4B3T is a "block code" that uses Return-to-Zero states on the line. 4B3T converts each group of 4 data bits into 3 "ternary" line signal states (3 symbols). The symbol rate is 3/4ths of the data rate (120 kbaud).

4B3T is defined in ETR 080, Annex B and other national standards, like Germany's 1TR220. 4B3T can be transmitted reliably at up to 4.2 km over 0.4 mm cable or up to 8.2 km over 0.6 mm cable. An internal termination impedance of 150 ohms is presented to the line at each end of the U-interface. Echo cancellation techniques allow full-duplex operation on the line.

In 4B3T coding, there are three states presented to line: a positive pulse (+), a negative pulse (-), or a zero-state (no pulse: 0). An analogy here is that operation is similar to B8ZS or HDB3 in T1/E1 systems, except that there is an actual gain in the information rate by coding 16 possible binary states to one of 27 ternary states.

There are many ways to perform this conversion, but BRI standards define a code known as MMS43 (Modified Monitoring State 43).

One requirement for line transmission is that there should be no DC build-up on the line, so there are some code substitutions based upon the transmission of the previous bits.

Physical interfaces

In ISDN technology there are three main types of interfaces for ISDN Basic Rate interface:

*S/T Interface (S0). Uses four wires with a separate pair of wires for the uplink and another pair for the downlink. The most used of the three interfaces
*Up Interface. Uses one wire pair using the half duplex "ping-pong" protocol. Used by many PABX systems that use ISDN technology. Depending of the possible cable range there are two varieties called UpN and Up0.
*Uk0 Interface. one wire pair with echo cancellation. Used for the long last mile cable between the telephone exchange and the network terminator.


ee also

*Primary Rate Interface

Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • Basic Rate Interface — Pour les articles homonymes, voir BRI. Suite de protocoles RNIS Couche Protocoles Canal D Protocoles Canal B Signali sation Paquet Télémétrie …   Wikipédia en Français

  • Primary rate interface — The primary rate interface (PRI) is a telecommunications standard for carrying multiple DS0 voice and data transmissions between two physical locations.All data and voice channels are ISDN and operate at 64 kbit/s.T1 vs. E1 SystemsNorth America… …   Wikipedia

  • Bit rate — Bit rates Decimal prefixes (SI) Name Symbol Multiple kilobit per second kbit/s 103 megabit per second Mbit/s 106 gigabit per second Gbit/s 109 …   Wikipedia

  • Line rate — The line rate of a communications link is the data rate of its raw bitstream, including all framing bits and other physical layer overhead. Fact|date=June 2007 For example, the line rate of a T1 data link is 1.544 Mbit/s, of which 1.536 Mbit/s is …   Wikipedia

  • Basic reproduction number — In epidemiology, the basic reproduction number (sometimes called basic reproductive rate or basic reproductive ratio) of an infection is the mean number of secondary cases a typical single infected case will cause in a population with no immunity …   Wikipedia

  • V5 interface — V5 is a family of telephone network protocols defined by ETSI which allow communications between the telephone exchange, also known in the specifications as the local exchange (LE), and the local loop. With potentially thousands of subscribers… …   Wikipedia

  • S interface — S interface: For basic rate access in an Integrated Services Digital Network (ISDN) environment, a User Network Interface reference point that (a) is characterized by a 4 wire, 144 kbit/s (2B+D) user rate, (b) serves as a universal interface… …   Wikipedia

  • T-interface — A T interface is used for basic rate access in an Integrated Services Digital Network (ISDN) environment. It is a User Network Interface reference point that is characterized by a four wire, 144 kbit/s (2B+D) user rate.Other characteristics of a… …   Wikipedia

  • U interface — U interface: For basic rate access in an Integrated Services Digital Network (ISDN) environment, a user to network interface reference point that is characterized by the use of a 2 wire loop transmission system that (a) conveys information… …   Wikipedia

  • Digital Visual Interface — (DVI) A male DVI D (single link) connector. Type Digital and analog computer video connector Production history …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”