Abstract In a digital transmission system for transmitting in parallel a plurality of information channels, and including a plurality of relay stations, a technique for detecting faults and particularly for distinguishing between faults in individual channels and a fault common to all channels which may arise due to rainfall attenuation. The method involves determining a first fault threshold level which is proportional to the level of interfering signals on a channel caused by the signals on neighboring channels and a second fault threshold level proportional to the level of noise signals on a channel resulting from channel components. At at least one relay station, a monitoring signal is developed for each channel which is representative of the level of the incoming signal to the relay station for the corresponding channel and the level of the monitoring signal is compared to the first and second threshold levels. If the monitoring signal level falls below the first threshold level, it is an indication of a single channel fault. If it is determined that the levels of the monitoring signals on all the channels fall below the first threshold level, it is an indication of a common fault to all of the channels. If only a single channel fault is determined, the incoming channel signal is switched to a standby channel. If, on the other hand, a common fault to all of the channels is determined, a switch-over to an alternate route is effected when the monitoring signal level falls below the second threshold signal level. Apparatus for developing the monitoring signals, for comparing the monitoring signals with the threshold levels and for effecting the appropriate switch-overs are described.
In a digital transmission system comprising a plurality of relay stations each receiving a plurality of signal channels in parallel, a method for detecting channel faults comprising the steps of: a. determining a first reference level corresponding to the level of interference signals expected on a channel from neighboring channels, b. determining a second reference level corresponding to the noise signal level on each channel caused by the circuit components in each channel and c. at least one relay station, monitoring the incoming signal level for each channel with respect to said first and second reference levels to develop an indication of a fault.
Claim 2
Dependent Claim
104 words
In a digital transmission system comprising a plurality of relay stations each receiving a plurality of signal channels in parallel, a method for detecting channel faults comprising the steps of: a. determining a first reference level corresponding to the level of interference signals expected on a channel from neighboring channels, b. determining a second reference level corresponding to the noise signal level on each channel caused by the circuit components in each channel and c. at least one relay station, monitoring the incoming signal level for each channel with respect to said first and second reference levels to develop an indication of a fault.
Claim 3
Dependent Claim
48 words
The method of claim 1 wherein said monitoring step includes the step of detecting in each channel if the level of the incoming signal is higher than said first reference level or lies between said first and second reference levels or is lower than said second reference level.
Claim 4
Dependent Claim
62 words
The method of claim 2 further including the step of switching at least one signal channel to a stand-by channel of said plurality of signal channels when the incoming signal of said at least one channel falls below said first reference level when it is detected that the incoming signal levels of any other channel is higher than said first reference level.
Claim 5
Dependent Claim
70 words
The method of claim 2 further including the step of switching at least one signal channel to a stand-by channel of said plurality of signal channels when the incoming signal of said at least one channel falls below said second reference level even if it is detected that the income signal levels of all other channels have fallen between said first and second reference levels caused by extensive channel faults.