Multiplex communications – Wide area network – Packet switching
Patent
1983-12-01
1986-12-16
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
371 22, H04J 300, H04J 600, H04B 1700
Patent
active
046302662
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an equipment for measuring digital channels multiplexed by packets in an analog or digital signal. Certain constant time intervals in the signal can randomly include packets to the extent of one packet per time interval. Each packet is conventionally made up of a heading including the address of the respective digital channel and a data block composed of words having a predetermined number of bits; the numbers of words in the data blocks differ from one packet to another.
Such a signal, particularly analog, mixed with packet mode digital channels can be the video signal from a television station link in which the digital channels are designed to transmit bulletins relating to various services. The packets are generally inserted at the line period at least in the active portions of free lines in the field synchronizing signal, where said free lines define time intervals having a constant duration.
The transmission of this multiplex signal through the various items of transmission medium between the transmitter connected to the television station link studio and for example the television receiver of a subscriber or a videotransmission relay generates certain abnormalities that can give rise to modifications in the data words or losses of packets which are more of a source for concern. The use of multiplex signals therefore requires an equipment for monitoring that the data packets are indeed received, by comparing at the transmission studio phase for instance, the packets transmitted and those received through the transmission medium. By interpreting these comparisons, it is possible to guide the technicians to certain probably defective devices in the transmission medium.
It is thus an object of the present invention to provide an equipment for measuring digital channels multiplexed by packets in an analog or digital signal with a view to detecting in particular the number of packets received in each digital channel through the transmission medium during a predetermined measurement time.
Accordingly, the measuring equipment is characterized in that it comprises in combination for a respective digital channel, means for detecting the address of the respective digital channel in the packets of the signal such as an analog or digital video signal and means for counting the number of received packets included in the respective digital channel in response to the detected addresses of the respective digital channel over a predetermined time, control means each for assigning address detecting means to one of the digital channels, and means for displaying said number of received packets after said predetermined time.
In accordance with other features of the invention, the measuring equipment can also display for each digital channel selected in the signal after said cyclic predetermined time:
the number of erroneous received packets responsive to detection of a fault in a particular word included in the heading of each packet and comprising a redundancy portion in accordance with a predetermined code;
the number of not received lost packets;
the number of received data words;
the number of received erroneous data words.
Preferably, the displaying means comprises a conventional television receiver fitted with a peritelevision socket and a known alphanumeric message decoder for converting the measurement results into characters displayable on the screen of the television receiver. The displaying means thus make it possible to reduce the cost of the measuring equipment since the equipment does not make use of the specific display means.
Additionally, the measuring equipment can, in shared time, monitor different multiplexed digital channels in several analog or digital signals. These signals can be video signals from various television station links.
Other features and advantages of the present invention will be more clearly apparent from the following description of several embodiments of the invention in reference to the corresponding accompanying drawings in which:
FIG. 1 shows a l
REFERENCES:
patent: 4363123 (1982-12-01), Grover
patent: 4413335 (1983-11-01), Clements et al.
patent: 4475192 (1984-10-01), Fernow et al.
Didon: Diffusion de Donnees par Paquet, Etat de la Technique, Radio-Diffusion-Television Magazine, Dec. 1980, Paris by Joseph Blineay, Guy Dublet, Yves Noirel and Jean-Calude Vardo.
Deparis Georges
Duverne Jacques
Meillan Philippe
Olms Douglas W.
Scutch III Frank M.
The Establissement Public Telediffusion de France
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