Subscriber connection net for the connection of subscriber...

Details Subscriber connection net for the connection of subscriber... Subscriber connection net for the connection of subscriber...

1998-06-09

2001-02-13

Hunter, Daniel S. (Department: 2684)

Telecommunications

Radiotelephone system

Zoned or cellular telephone system

C455S423000, C455S424000

Reexamination Certificate

active

06188893

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a subscriber connection network for connecting subscriber stations to a telecommunications switching office, which network comprises a radio system for establishing the connections.
Accordingly, a radio system is required whose air interface is between fixed subscriber connection units for subscriber terminals or mobile subscriber terminals and radio base stations which are each configured to serve a plurality of subscriber terminals and are connected via a transmission link to radio control units which are near to the switching office.
The connection of a subscriber terminal to the switching office can be established here optionally via at least two of the radio base stations. In addition, it is possible for a changeover to another radio base station without interruption during an existing connection.
Communications systems quite generally, and accordingly such a subscriber connection system, require that the failure of a function unit must lead to the failure of a communications facility or to the interruption of active connections for only a specific number of subscribers. In practice, this may be, for example, 64 subscribers. A further requirement consists in the fact that such a failure of a function unit must entail only a specific level of traffic losses which it is to be possible for the operator to define within certain limits.
The aforesaid requirements are, on the other hand, to be fulfilled with the lowest possible expenditure on manufacture and development. A concept with redundant function units or a large number of small function units which serve only a small number of subscribers is subject to limits owing to the manufacturing costs. The possibility of equivalent circuitry to maintain existing connections in the event of the failure of a function unit is, if a relatively large number of connections will be affected, possible only with high development costs.
In a known subscriber connection network of the abovementioned type, for which the terms RLL (Radio Local Loop) or RITL (Radio In The Loop) are also used, every subscriber has optional access to any base stations and, furthermore, it is possible, in the course of an existing connection, to change over without interruption from one base station to another if the quality of the radio connection has diminished (Ericsson Review 2, 1994, A DECT Solution For Radio Access Application). In this known subscriber connection network there are transmission links for 2 Mbit/s signals between a central device of the radio system and the telecommunications switching office. The failure of one of the transmission links leads to a total failure of the subscriber stations which can be reached via it.
SUMMARY OF THE INVENTION
The object of the invention consists in configuring a subscriber connection network, in such a way that in terms of the abovementioned aspects, namely the lowest possible development and manufacturing expenditure, total failures are limited to, at most, prescribed numbers of subscriber stations and it is also possible, to a certain extent, to save existing connections when function units fail.
According to the present invention, at least one interface unit, conceived as a downtime unit, for connecting a connection line which leads to the telecommunications switching office and whose database contains the subscriber data is provided as a component of the radio control units. In addition, on the subscriber side, at least two interface units are provided for connecting a transmission link which connects to a radio base station and whose database contains the data of the respective radio base stations. In addition, an interface unit for connecting a system for operational and maintenance tasks is provided, from which system, inter alia, subscriber data and/or data of the radio base stations are input into the database of the aforesaid database units. Finally, a multiple bus system for connecting the interface units to whose individual bus systems the interface units have access to differing degrees is provided as a further component of the radio control units.
Owing to the configuration according to the invention, the failure of an switching office-side interface can lead only to the loss of the connections routed via it, which, however, meets the requirements relating to the upper limit in the case of a total failure since these interface units are conceived as a downtime unit.
In the event of a failure of a subscriber-side interface unit or the transmission link connecting the latter to a radio base station, which is a fault situation which is to be expected significantly more frequently than the failure of an switching office-side interface unit, there continues to be the possibility of a connection setup for all the subscribers, even if with a reduced level of traffic quality. Here, it is neither necessary to provide redundancy nor to set up a so-called hot standby mode in order to save existing connections, which also makes the solution according to the invention correspondingly cost-effective.
In an advantageous functional distribution of procedures during the connection setup owing to an outgoing seizure and an incoming seizure distribution leads to a relatively simple structure of the interface units.


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Ericsson Review, No. 2, (1994), Guy M. Campbell et al, DCT 1800—A DECT Solution for Radio Access Application, pp. 84-92.

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