+ PETERSTAR - Internet and Data Services - Leased Lines - Technologies

		xDSL (ADSL, RDSL, SDSL, HDSL)

		ISDN

		HPNA

ISDN

1. Brief Technical Information

The PeterStar ISDN network is built on digital 5ESS switches made by Lucent Technologies. Connections within the PeterStar ISDN network are organized under the ISDN PRI protocol being an intelligent high-speed protocol of exchange interaction.

Subscriber’s line equipment can be installed both within the 5ESS service zone (in this case they are called ISLU - Integrated Services Line Unit) and on remote units RISLU (Remote Integrated Services Line Unit). That’s why the PeterStar ISDN network coverage gradually expands. At present PeterStar is capable of providing ISDN base rate services by copper pair in practically any district of St. Petersburg, while in April 1997, when the service was announced, it was available in the central districts and Vassilievski Island only.

PeterStar provides two levels of accessing the ISDN network: base rate access (ISDN BRI, 2B+D) and primary rate access (ISDN PRI, 30B+D) over a digital E1 trunk.

In case of base rate access the ISDN network terminal is an NT1 device (Network Terminal type 1). In case of primary rate access a NT2 terminal is used which is usually a large PBX with the ISDN functions (for instance, a PBX Definity made by Lucent Technologies) or ISP access servers.

User devices (ISDN modems, telephones, video terminals) are connected after a network terminal. These connections are synchronous, serial and duplex and provide data transmission in the digital form across the whole segment between subscribers at a data speed divisible by 64 Kbps.

At the OSI model level (for transmitting “user/network” service signals) the PeterStar ISDN network uses the SS7 (Signaling System 7) protocol.

Base Rate Access

Base rate access is provided via the interface arranged by copper pair similar to that used for a usual telephone line. By means of multiplexing three channels are created for a user. A traditional configuration represents two 64Kbps B-channels (Bearer channels) and one 16Kbps D-channel.

User information is transferred over B-channels. This can be voice communication, video or data depending on the operation mode of terminal equipment used. D-channel transfers service information to coordinate the work of users’ terminal equipment connected to the ISDN network. User information in the form of data packages can be also transferred over a D-channel.

isdn_bri

Primary Rate Access

Supports data speeds of up to 2.048Kbps. A primary rate trunk comprises 31 channel, 30 out of which are equivalent to B-channels of a base rate trunk with a speed of 64Kbps, and the remaining D-channel provides internetworking of information B-channels.

Primary rate interface is used in cases when a high channel capacity is required to run applications. A PRI trunk is mainly used for connecting PBX’s and access servers, by that increasing 15-20% the efficiency of their using compared to the connection by digital telephone 2Mb trunk (ICM-30).

ISDN PRI connection is of interest of large offices and Internet service providers (ISP), for they can be able to offer end users all advantages of being connected to the ISDN network via the 2B+D interface, listed below.

isdn_pri

2. Technology Advantages

At present the PeterStar ISDN network allows the provision of a full range of up-to-date digital communication. The basic advantages of this technology are:

Highest quality and reliability of communication
Immediate connection with your subscriber
High data rate
Possibility of connecting to the ISDN network over a usual copper pair, with this considerably reducing the cost of solution
Possibility of concurrently making telephone calls and transmitting data
High-speed Internet access and access to other information resources
Saving on reducing the time required to send a certain data traffic volume compared to that when connecting via analog modems

Quality and Reliability of Communication

Higher reliability and quality of communication under ISDN technology compared to the analog PSTN (Public Switched Telephone Network) is ensured by data represented in the digital form across the whole route from the subscriber-source to the subscriber-receiver. When data is transmitted in the PSTN using analog modems, being transmitted over long distances the analog signal from the modem output attenuates and requires further amplification. Along with the signal noise is amplified as well, resulting in errors occurring on the receiving side at the signal analog-digital conversion. In this case the data speed is fundamentally limited to 33.6 Kbps.

Speed of Connection

ISDN technology makes it possible to establish a connection quicker and more reliable due to service information being transmitted over a separate D-channel. Having pressed the last digit of your subscriber number, the connection will be established almost immediately or it will be determined that the number is busy, irrespective of the distance between the subscribers. Moreover, any error is practically excluded in dialing the number.

Data Rate

When using the BRI interface two 64 Kbps channels are available for you, and the maximum data rate makes 128 Kbps. But this is not the limit, for by means of multiplexing it is possible to combine in one session several ISDN BRI lines to obtain higher data rates.

ISDN opens new opportunities provided by interactive communication for both individuals and large international corporations and global markets. The number of opportunities revealed continuously expands.

3. Typical Technology Applications

Establishing telephone communication in a small office (SOHO)
Combining local area networks
Conducting full-screen videoconferences