Multiplex communications – Wide area network – Packet switching
Patent
1987-02-18
1989-02-28
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370100, H04Q 1104
Patent
active
048092592
DESCRIPTION:
BRIEF SUMMARY
TECHNICIAL FIELD
The present invention relates to an arrangement for establishing a wide band connection in a switching network in telecommunication equipment operating with pulse code modulation and time division multiplexing, where the connection comprises two or more channels.
BACKGROUND ART
The invention is intended for use in telecommunication systems which divide the bit flow up into a plurality of channels for a predetermined number of bits, e.g. 64 kbit channels, which applies to such as the AXE type of system.
In such systems is a need of being able to establish high quality connections, e.g. connections for video transmission. This means, inter alia that a sampling rate must be enabled which is higher than that applicable to the basic system.
The problem is solved by two or more channels being combined and thus creating a so-called wide band connection. Such channels which form a wide band connection must be monitored on establishing communication in the switching network so that the respective contents/samples are not mutually delayed, since there is distortion in the transmitted information if this delay takes place.
For solving this problem it would be possible to modify the group selector (switching network in the respective station/exchange, where its modification would mean that the selection of internal time slots must be controlled for the wide band connection.
The time slots must then be selected so that writing into/reading from the speech memories of the channels included in the connections is carried out with the information kept together. Such a modification can be performed entirely in the software.
DISCLOSURE OF INVENTION
The solution proposed above also involves large disadvantages, however, since the internal time slots cannot be at free disposal, which causes the probability of congestion to increase. The probability of congestion also appears to be dependent on the mutual relationship of incoming and outgoing time slots. The increased probability of congestion will thus extend the mean connection time.
An alternative way of solving the problem mentioned is that when local or transit nodes are through-connected, a possible mutual delay is allowed to take place, due to the transfer between external and internal time slots, and to equalise the possible delay between the contents of the channels after the through connection has been completed in the switching network.
The invention comes to grips with this complex problem and proposes that during a connection establishment stage the switching network input is supplied with specific information as to the respective phase position of the channel contents, and that at the output of the network this specific information is detected and delays are regulated in means for equalising the contents of the channels.
What may be more concretely considered as characterizing for the new arrangement is, inter alia, that a marking means is disposed at the switching network input such that during a connection establishment stage the means applies markings in a plurality of successive frames of the respective contents in the time slots utilized by the connection channels, and that a scanning means is disposed at the output of the switching network such that the scanning means detects a pattern formed by said markings, and with the aid of it determines a possible delay between the respective contents of the channels, due to the through connection process in the switching network. A further characterizing feature is that scanning means controls delay equilising means in the channels so that the equalising means ensures that, after the connection establishment stage, the contents of the channels/time slots regain their mutually synchronized positions in spite of the possible, mutual delay.
In a preferred embodiment, the content in each affected time slot in a first frame is assigned a first marking, the content in each affected time slot in a second frame a second marking, and so on. The number of frames marked thus is selected such that it is e
REFERENCES:
patent: 4154984 (1979-05-01), Murason
patent: 4500991 (1985-02-01), Lubcke et al.
patent: 4543652 (1985-09-01), Amada et al.
Olms Douglas W.
Telefonaktiebolaget L M Ericsson
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