Primary Rate Interface

The Primary Rate Interface ( PMxAs ), English Primary Rate Interface (PRI ), is an interface definition in ISDN, which is used mainly by companies to connect telephone equipment to the ISDN. Another connection in ISDN is the base connection.

  • 3.1 line interface between the local exchange and the network termination 3.1.1 UK2 (electric)
  • 3.1.2 UG2 (optical)
  • 3.2.1 S2M (electric)

Terms and abbreviations

Other names for the PRI are PMx port and S2M port. Common abbreviations are PMx, PMxA, PMxAs, PRI, CEPT1, E1 (in Europe), T1 ( in the U.S.), J1 (in Japan) and S2M.

Channel structure

The primary rate interface is organized into channels and is composed of at least 16 and a maximum of 30 data channels (B channels ) and one signaling channel ( D channel) and a synchronization channel. There are different channel structures:

  • E1 - 2048 kbit / s gross data rate as follows in 32 channels at 64 kbit / s divided in Europe: 30 bidirectional data channels with 64 kbit / s ( together 1920 kbit / s)
  • One signaling channel of 64 kbit / s
  • 1 synchronization channel with 64 kbit / s
  • T1 - in USA 1544 kbit / s gross data rate, depending on the signaling method is divided as follows: Common Channel Signaling (CCS) 23 bidirectional data channels with 64 kbit / s ( together 1472 kbit / s)
  • One signaling channel ( the 17th ) of 64 kbit / s
  • 1 synchronization channel ( the 1st ) of 8 kbit / s
  • 24 bidirectional data channels with 64 kbit / s
  • In each channel, one bit is used for signaling ( robbed bit ) every sixth frame. A more detailed explanation here Robbed bit signaling.

B-channel

A user channel is referred to as B - channel (of English. Bearer ). Of understanding a user channel corresponding to a communication channel, it is used, for example, a telephone call.

H channel

Several of the user channels a primary rate access can be combined to achieve a higher transmission rate (up to 1920 kbit / s). These are called H- channels.

Transmission method

The primary multiplex connection channels in the time division multiplexing ( TDM / TDMA ) is transferred, that is, the channels are transmitted one after another in the so-called time slots.

The time slots of a primary rate connection E1 may be used as follows:

  • The time slot 0 is used for synchronization and error handling with the checksum Cyclic redundancy check ( CRC, Eng. CRC).
  • In the fifteen time slots 1 to 15 voice channels are transmitted.
  • In the time slot 16, the data for controlling the ISDN communication are transmitted ( D channel).
  • In the fifteen time slots 17 to 31 voice channels are transmitted.

Thereafter, a new framework with time slot 0 begins. The frame period is 125 microseconds, the frame repetition is 8 kHz.

Line interface between the local exchange and the network termination

UK2 (electric)

The line interface between the local exchange and the network termination (Network Termination) in the house is called when using copper cables as " UK2 interface". In general, two copper pairs are used. For bridging larger distances between the exchange and network termination repeaters must be used.

UG2 (optical)

Instead of electrical UK2 interface, and the optical UG2 interface is used occasionally. Here, a fiber optic line for return direction is connected ever. Due to much more favorable damping values ​​can be with this type of connection longer distances to realize to the exchange.

Line interface between network termination and telephone system

For the network termination at the primary rate interface of NTPM used. The line interface between the NTPM and the PBX is called " S2M ".

S2M (electric)

The transfer direction for the S2M interface two wires ( one twisted pair ) is required, therefore a S2M cable contains four wires (two twisted pairs ), which may have a common shield. The line coding for the S2M interface is ternary, ie there are three electrical states. Thus, the S2M interface required for each direction of transmission has a bandwidth of only about 1 MHz, while the data transfer rate is 2048 kbit / s.

  • ISDN
Integrated Services Digital Network Basic Rate Interface European Conference of Postal and Telecommunications Administrations Common-channel signaling Bandwidth (signal processing)
660920
de