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V5.2 Protocol Architecture

V5.2 is a way of interfacing the Access Network (AN) to the Local Exchange (LE)

The protocol stack of V5.2 interface is used to connect the Access Networks (AN) to Local Exchanges (LE) or TDM Digital Switch.

Diagram of Network Application V5.2 AN System Connection to TDM switch or Local Exchange

Figure 1. Example V5.2 AN System Connection to TDM switch or Local Exchange (LE)

Requirements to V5.2 interface protocols were defined in ETSI, and ETS 300-347-1 standards and G.965 ITU-T recommendations.
V5.2 interface contains from 1 to 16 Е1 ports with 2,048 kbps transfer rate and provides for subscriber load concentration.
One V5.2 interface can support up to 3,000 PSTN ports or 1,500 ISDN basic access ports. In addition both PSTN and ISDN ports can use the same E1 interfaces.

Access Methods

What is V5.2 interface? This is an interface that supports user access to telecommunications networks.
V5.2 interface is used with the following access methods:

  • Access over analog lines
  • Access over ISDN BRI channels
  • Access over ISDN PRI (V5.2) channels
  • Other analog or digital access systems for semi-permanent connections without associated signaling information that is transmitted over the separate channel (outbound).

V5.2 interface uses 2,048 kbps channels and it can work with 16 such channels at a time.
When analog access is used then signaling on the PSTN user port is converted into the functional part of V5.2 protocol to be transmitted to the LE side.
The control protocol is defined for ISDN users in V5.2 stack to exchange specific functions and messages that are required to provide coordination with the call control procedures in the LE.
To support the higher-level traffic and dynamic channel allocation the V5.2 protocol supports the following additional functions:

  • The reference channel establishment protocol provides establishment and restoration of connections on requests identified by signaling messages under LE control
  • The channel control protocol is used to control channel identification and blocking as well as error processing for multichannel systems
  • The security protocol used with two channels for security reasons controls switching of the communication channel security system when failures occur

The following protocols are defined on different V5.2 stack levels: LAPV5-EF, LAPV5-DL, V5-Link Control (Channel Control), V5-BCC, V5-PSTN, V5-Control (Control), V5-Protection (Protection).

V5.2 Functional Levels and Protocols

V5.2 provides for various protocols of 3 functional levels – physical, data link and network.
Physical level is a standard 2,048 kbps digital transfer system represented by E1 (120 Ohm) interface.
Electrical parameters of E1 ports in V5.2 interface should meet ITU-T G.703 and G.704 recommendations as well as ETS 300-166 standard.
V5.2 interface can contain up to 16 E1 links (2,048 kbps) and support load concentration.
Data link level is represented by LAPV5 protocol whose task is to transfer network level messages.
Network level is represented by the following protocols:

  • PSTN signaling support protocol
  • user port control service protocol (Port Control Protocol)
  • common control service protocol (Common Control Protocol)
  • bearer channel assignment service protocol (BBC – Bearer Channel Connection)
  • interface link control service protocol (Link Control Protocol)
  • protection service protocol (Protection Protocol)

V5.2 Interface Protocol Architecture

The following figure is a block diagram of V5.2 interface protocol architecture related to functional levels and position within the telecommunications network.

V5.2 Interface Protocol Architecture Block Diagram

Figure 2. V5.2 Interface Protocol Architecture

These protocols allow the telecommunications equipment to operate in LE (Local Exchange) or AN (Access Network) modes as well as support access to analog phone services (PSTN) and ISDN basic channels.
When this architecture is compared to client-server machines its LE side is more similar to the switch server while the AN side switches the clients.
LE side provides centralized control of the system while AN side processes the distributed subscriber interface.
Please note that PSTN protocol and control protocol operate in V5.1 and V5.2 interfaces and the remaining protocols operate in V5.2 interface only.

V5.1 Protocol Architecture

V5.1 protocol is a variant of V5 interface. It differs from V5.2 in the way the digital channels are used.
V5.1 interface contains one 2,048 kbps E1 port only and it can service up to 30 PSTN subscribers or up to 15 ISDN basic access channels without concentrating the load (static multiplexing).
V5.1 and V5.2 interface architectures differ in the number of the used protocols. PSTN protocol and control protocol only operate in V5.1 interface.
Figure 3 shows the architecture of V5.1 interface protocols.

V5.1 Interface Protocol Architecture Block Diagram

Figure 3. V5.1 Interface Protocol Architecture

V5.2 protocol is a variant of V5 interface. It differs from V5.1 in the way the digital channels are used.
V5.1 interface contains one 2,048 kbps E1 link only without load concentration (static multiplexing).

Key Differences Between V5.1 and V5.2

V5.1 and V5.2 interfaces differ in the following key functionalities/features:

  • V5.1 contains one E1 link only while V5.2 can contain up to 16 E1 links
  • V5.1 does not support ISDN primary rate user access ports
  • V5.2 uses more service protocols such as Channel Assignment Protocol (BCC), Protection Protocol and Channel Control Protocol
  • V5.2 uses additional reserved channel intervals to improve communication security

Incorporation or Integration of V5.2 AN Systems in IP Network

As modern communication methods emerge it is important to incorporate and integrate the existing V5.2 TDM equipment in VoIP networks and Softswitch.
Dedicated V5.2 VoIP gateways can perfectly cope with this task.

Terratel VoIP Gateway allows to connect V5.2 AN systems to IP network and Softswitch

Figure 4. Terratel VoIP Gateway allows to connect V5.2 AN systems to IP network or Softswitch

In addition Terratel V5.2 VoIP gateways can work simultaneously with the required number of PCM lines from AN and LE side.
This product can be used also as V5.2 to SS7 converter.