Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Patent
1996-04-19
1998-06-02
Chin, Stephen
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
375220, 375347, 370225, 370228, 370248, 34082516, H04B 702
Patent
active
057612455
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of International application PCT/FI94/00372, filed Aug. 24, 1994.
BACKGROUND OF THE INVENTION
This invention relates to a method and a system for performing redundancy control of baseband primary channel interfaces of mutually substantially identical receivers in a digital transmission device, such as a radio link.
Redundant transmission devices, which typically use two identical transmitters and receivers connected in parallel, e.g. a radio link, and a baseband branching means connected to them (so-called 1+1 redundancy), operate in both the inbound and outbound direction of a telecommunications network. The selection of the radio device to be used in each particular instance usually depends on which one of the devices produces the signal of the highest quality.
In so-called frequency redundancy, device redundancy is realized by having two signals of different frequencies propagating between the near end and far end, i.e. the system comprises two transmitter-receiver pairs operating at different frequencies. So-called polarization redundancy is analogous, but it carries two signals having different polarizations.
By using a changeover control method, the control of device redundancy of a radio link jump secured by frequency or polarization redundancy is effected, i.e. a reliable and simple device redundancy (not hitless) for the radio link jump.
In the prior-art changeover control methods, the signal received by the less faulty receiver is selected as a line signal. At the far end, it may happen that one of the transmitters is faulty, and therefore forwards an alarm signal AIS (Alarm Indication Signal), whereas the stand-by transmitter is completely faultless. A drawback of the known methods is that as radio links do not usually identify the information content of a signal to be transmitted, a received AIS signal will not bring about failure detection in the radio link, and so it is quite possible that the AIS signal is selected for transmission to the line, even though the stand-by signal would be faultless.
SUMMARY OF THE INVENTION
The object of this invention is to eliminate the draw backs of the above-mentioned known methods. To achieve this, the method according to the invention is characterized in that the method comprises the following steps: transmission direction at the far end; receivers; the receivers on the basis of the failure situation comparison so that the signal with higher quality of the output signals of the receivers will be transmitted towards the primary channel.
The method according to the invention has the following advantages: and simple device redundancy to be realized for a radio link jump with no other external changeover control means than a passive baseband branching means and cabling between the redundant pair; redundant link jump, whereby transmission of one pair and reception of the other pair may fail without a break in the connection in either direction; and device using a baseband branching means and a connection between far-end and near-end control means.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be described more fully by way of example with reference to the attached drawing, in which FIG. 1 shows two mutually communicating radio links forming part of a baseband network.
DETAILED DESCRIPTION
FIG. 1 shows a redundant system which comprises four identical transmitter-receiver radios A, B, C and D, which form two redundant pairs A, B and C, D; and two passive baseband branching means 1 and 2. The structure of suitable baseband branching means is described more closely e.g. in the Finnish Patent No. 87 123. A signal LT1 from a line L1 is branched in the baseband branching means 1 to the radio units A and B, while a signal LT2 from a line L2 is branched in the branching means 2 to the units C and D. Correspondingly, either one of signals RA or RB received by the radio unit A or B is selected through the branching means 1 as a signal LR1 to be transmitted to the line L1, and either one of signals RC or
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Haukkavaara Ilkka
Ihatsu Jari
Chin Stephen
Le Amanda T.
Nokia Telecommunications Oy
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