SU843282A1 - Device for simulating discrete communication channel - Google Patents

Description

(54) DEVICE FOR MODELING DISCRETE

COMMUNICATION CHANNEL

one

The invention relates to telecommunications and can be used for testing of noise-resistant coding and decoding in conditions close to the conditions of testing in real communication channels.

A device for simulating a discrete communication channel comprising a noise source connected in series with a driver and a first match element, a second match element and a clock generator, the outputs of which are connected to the first inputs of the match elements 1, is known.

However, the known device has low accuracy, modeling error statistics of real communication channels and does not provide thorough testing of error-correcting coding-decoding devices.

The purpose of the invention is to improve the accuracy of modeling.

To do this, in a device for modeling a discrete communication channel, containing, its noise source, connected in series with the former and the first element of the match, the second element of the match and

the clock generator, the outputs of which are connected to the first inputs of the coincidence elements, are connected in series, an attenuator, an additional driver and a wait, a multivibrator, a switch and a shift register, the outputs of which are connected to the corresponding inputs of the switch. The input of the shift register is connected to the output of the second coincidence element, the input of which is connected to the output of the waiting multivibrator, in addition, the output of the noise source is connected to the input of the attenuator, and the output of the first matching element to the corresponding input of the switch.

The drawing shows a diagram of the proposed device.

The device for simulating a discrete communication channel comprises a noise source 1, a driver 2, a first coincidence element 3, a clock generator 4, a switch 5, a shift register 6, a second coincidence element 7, an attenuator 8, an additional driver 9, and a waiting multivibrator 10.

Claims (1)

The device works as follows. The source of the Shuma 1 generates a noise signal, which in the shaper 2 containing the threshold element turns into a sequence of pulses of random duration. When the threshold is exceeded, a single impulse of random duration appears at the input of the first coincidence element 3, the instantaneous value of the noise signal at the output of the threshold element. From the output of element 3 of coincidence, the channel sequence, with the errors introduced, is fed to the input of switch 5, which, depending on the signals at the control inputs B, inverts the sequence arriving at its input, or leaves it unchanged. From the output of the switch 5, the channel sequence is fed to the input of the decoder of the error-correcting code, for which the proposed device is intended to be tested. With the help of switch 5, the phenomenon of reverse operation is simulated, which takes place in phase shift keying demodulators. . Serially connected attenuator 8, driver 9, standby multivibrator 10, second matching element 7 and cyclic shift register 7 represent the control circuit of switch 5. Forming signals to the clock input of cyclic shift register 6 is performed as follows. The signal from the output of the Schuma source 1, attenuated in the attenuator 8, in the shaper 9, is converted into a random stream of short pulses that occur at the moments when the threshold value of the shaper 9 is exceeded by the instantaneous value of the shuma. From the output of the imaging unit 9, a random stream of short pulses enters the input of the multivibrator 10. The number of pulses depends on the noise level at the output of noise source 1, the attenuation of the attenuator 8 and the threshold value 9 of the imager, and determines the total number of simulated coherent oscillations in the demodulator . Since communication systems usually operate at such signal-to-noise ratios, that the conditional probability of a coherent oscillation phase jump is several orders of magnitude lower than the probability of a channel error, the number of pulses input to the standby multivibrator 10 should be small compared to the number of pulses coming from the output 2 shaper. For this, the noise signal input to the driver 9 is attenuated in the attenuator 8. By changing the attenuation coefficient of the attenuator 8, which in the simplest case is a resistive voltage divider, you can change the total number of simulated phase jumps, which depends on the signal-to-noise ratio in the channel and other parameters. Impulses of infinitesimally short duration from the output 9 of the driver are fed to the input of the waiting multivibrator 10, at the output of which pulses are formed, the duration of which depends on the parameters of the waiting multivibrator circuit and can vary within wide limits. From the output of the standby multivibrator 10, the pulses go to one of the inputs of the second coinciding element 7, to the second input of which pulses come from the output of the clock generator 4, whose frequency is several times (10-20) higher than the clock frequency of the channel sequence passing through the series-connected element 3 matches and switch 5. Thus, at the output of the match element 7, a packet of high-frequency pulses is formed, the duration of which is equal to the duration of the pulse coming from the output of the standby multivibrator 10 The said packet of high-frequency pulses arriving at the input of the cyclic shift register 6 creates the effect of random phase jumps on the control inputs of the switch 5, which corresponds to tracking failure and trapping. The last high-frequency pulse in the packet cyclic shift register 6 is set to the state corresponding to the phase of the reference oscillation 0 ° or 180 ° and will remain in this state until the next short pulse arrives at the input of the waiting multivibrator 10. Since the duration of the pulses generated by the waiting multivibrator 10 Unstable and the number of high-frequency pulses in the packet is quite large, then the state of the switch 5, corresponding to the phase of coherent oscillation 0 ° or 180 ° for a long time will be equal to about tny. The duration of the pulses generated by the waiting multivibrator 10 varies within 10-100 channel pulse durations, which allows simulating the various inertia of the PLL system. It is necessary to simulate the effects associated with phase jumps of coherent oscillation in a demodulator of double phase shift keying signals or in some other demodulator leading to changes in the circuit diagram of switch 5 and cyclic shift register b. Thus, the use of the proposed device for simulating a discrete communication channel makes it possible to carry out comprehensive tests of the encoder in conditions as close as possible to the real ones, without the use of sophisticated equipment and acceleration of the tests. Apparatus of the Invention A device for modeling a discrete communication channel, containing a source of noise, connected in series with the former and the first element of the match, the second element of the match and the clock generator, the outputs of which are connected to the first inputs of the match elements, characterized in that, in order to improve the accuracy of the simulation, An attenuator, an additional driver and a waiting multivibrator, a switch and a shift register, the outputs of which are connected to the corresponding switch inputs, register input AND- the shift is connected to the output of the second coincidence element, the input of which is connected to the output of the waiting multivibrator, in addition, the output of the noise source is connected to the input of the attenuator, and the output of the first matching element to the corresponding input of the switch. Sources of information taken into account in the examination 1. USSR Author's Certificate No. 417914, cl. H 04 L 9/04, 1972 (prototype).