JPS605098B2 - Signal quality verification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal quality verification method for data transmission, and particularly to a signal quality verification method that enables simple signal quality detection.

In recent years, as the amount of transmitted information has increased, high-speed transmission has become possible.

For example, 9600 bps (bits per second) for a telephone channel
Examples include transmission. In such highly efficient transmission, the error rate increases depending on the condition of the line, and there may be cases where it becomes unusable. In such a case, it is necessary to notify the terminal that the signal quality is poor. The present invention has been made in view of the above points, and it is an object of the present invention to provide a signal quality verification method that enables simple signal quality detection. It is common knowledge that modems are equipped with automatic equalizers for high-efficiency transmission as described above.

Furthermore, in order to make the automatic equalizer work effectively, it is well known to perform exclusive OR (hereinafter referred to as XOR) on a signal with a pseudo-random code to randomize the signal. On the receiving side, if the received code is XORed with the same pseudo-random code, the original signal is decoded. , and the signal must be random to accurately measure the error rate.

The present invention has been made in consideration of the above and focusing on the following facts.

In other words, in a modem that sends a randomized signal,
Even if the transmitted signal is held at ``1'' for example, the transmitted signal is randomized, and if a code error occurs during transmission, the erroneous bit will be changed to 0'' in the received signal after decoding. Therefore, if the transmitted signal is 1″ for a certain period of time,
(or 0"), and the received decoded signal's "0"
'' (or 1'') by counting the number of pulses with a counter, the error rate can be determined. . FIG. 1 is a block diagram for explaining one embodiment of the verification method according to the present invention. When a "transmission request" is received from a terminal, a transmission timer 1 operates, and its output A causes a carrier signal of a transmission circuit 15 to be transmitted. is generated and supplied to the transmission line.

Of the other two outputs of the transmission timer 1, B is supplied to the random signal generation circuit 12, and the other C is supplied to the first AND circuit 13 together with a transmission signal from a transmission terminal (not shown). Then, the output of this first AND circuit 13 and the output of the aforementioned random signal generation circuit 12 are combined into a first
By supplying the first XOR circuit 14 to the input thereof, the output of the first XOR circuit 14 is supplied to the transmission line 16 via the transmitting circuit 15. Further, this transmitted signal is received by a receiving circuit 17 and branched into two branches, one of which is supplied to an automatic equalizer 18 and the other to a preprocessed signal detection circuit 19. The output of this preprocessed signal detection circuit 19 is supplied to two reception timers, and this reception timer 20 is operated. Of the three outputs of the reception timer 20, B' is sent to the automatic equalizer 18 and the random signal generation circuit 21, C' is sent to the second AND circuit 22, and the other output D is sent to the third A.
The signal is supplied to the ND circuit 23. The respective outputs of the automatic equalizer 18 and the random signal generation circuit 21 are
The output of the second XOR circuit 24 is supplied to the other inputs of the second and third AND circuits 22 and 23. The output of the second AND circuit 22 is supplied as a received signal, and the output of the third AND circuit 23 is supplied via the counter 25 to the counting result discrimination circuit 26, and the output of the counting result discrimination circuit 26 is Provided as a signal quality detection signal. The block diagram shown in FIG. 1 will be explained in detail with reference to FIG. 2.

That is, on the transmitting side, when a "transmission request" signal F is received from the terminal, the modem carrier is generated for the period shown in FIG.
The random signal generating circuit 12 is operated during the period shown in FIG. 1 to generate a random signal.

Furthermore, after T2 elapses after the random signal is generated, the transmission timer 1 sends a "send ready" signal G to the terminal and
The AND gate of the transmission signal is opened for a period of , and the transmission signal is XORed with a random signal, randomized, and transmitted. Here, until the transmission signal is sent, there is no transmission signal (a binary signal of 0'' is transmitted), and a random signal is output as is.Then, the first XOR
The output of 14 is modulated by the transmitting circuit 15 and transmitted to the transmission line 1.
6. Before transmitting the random signal, a second preprocessed signal is sent to inform the receiving side of the random signal generation timing, etc.
As shown in Figure E, the time is extremely short, but time is added. On the receiving side, the receiving circuit 17 detects the carrier during time T3 and demodulates it.

A baseband signal is thus obtained. Further, the preprocessed signal detection circuit 19 detects the preprocessed signal and operates the reception timer 20. By detecting the preprocessed signal, the random signal generating circuit 21 is operated for the period shown in FIG. 2B, and the tap convergence operation of the automatic equalizer 18 is started. After generating a random signal on the transmitting side and after a time margin T2 that is larger than the time T4 required for the taps of the automatic equalizer on the receiving side to converge to a value sufficiently close to the optimum value, a "R transmission ready" signal is sent to the transmitting terminal. The transmitting side timer and the receiving side timer 11 and 2 are set so that the terminal device starts transmitting a transmission signal during the period shown in Figure 2, C and O.

The output of the automatic equalizer 18 is a random signal as well as a second X
The output of the second XOR circuit 24 and the signal shown in FIG. This is a case where 1'' is received by mistake even though 0'' is being sent.Furthermore, the counting result discrimination circuit 26 discriminates the counter result of the counter 25, and if it is above a certain value, the signal quality is Make the terminal report it as bad.The second X gated with waveform C'
The output of the OR 24 goes to the receiver end as a received signal. Therefore, before sending out the transmission signal on the transmitting side, the transmission signal is set to "0".
If there is no transmission error between L and L after the automatic equalizer starts working on the receiving side, n0'',
If there is a transmission error, .1'' will appear as the received signal.

If we take an appropriate period during this period, for example 1 second, if there is one error in 960 dish ps transmission, the error rate will be 10-4, and if there are 10 errors, the error rate will be 10-3. Therefore, it is possible to count the number of output "1"s during this period and, for example, if it is 10 or more, the modem can notify the receiving terminal that the signal quality is poor. Furthermore, by sending back information to the transmitting side that the signal quality is poor, it is possible to start over again from the beginning or to transmit at a lower transmission speed. Furthermore, after receiving information that the signal quality is good on the transmitting side, it is also possible to set the signal to be "transmissible". As explained above, in a transmission method in which signals are randomized using pseudo-random signals and then transmitted, on the receiving side, two of the signals received at a certain time before the signal from the transmitting terminal are sent.
It is possible to count the number of one level of the value and determine that the signal quality is poor if the number is greater than a certain number.

According to the method of the present invention, since the quality of the signal is determined using a completely random signal, the determination can be made based on probability and statistics, and can be accurately determined in a short period of time. Furthermore, the present invention does not require any special equipment to generate such a random signal, and the determination can be made using a short period of time before the signal is transmitted, so the structure is extremely simple and practical.
Furthermore, according to this method, the degree of tap convergence of the automatic equalizer can also be determined. Incidentally, in the above embodiment, the state in which there is no transmission signal is defined as 0'', but it goes without saying that during this period, ``1'' may be sent as the transmission signal and the receiving side may count ``0''.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram for explaining one embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation in FIG. 1. Power/Figure O 2

Claims (1)

[Claims] 1. A transmitting side is constituted by a signal source that supplies a signal, a randomizing means that randomizes a signal from this signal source, and a transmitting means that transmits a signal from this means, and a transmitting side that receives a signal from this transmitting means. equalizing means for automatically equalizing the signal obtained by the receiving means; decoding means for derandomizing the signal obtained by the equalizing means; and a receiving side that treats the received signal as a received signal, the transmitting side transmits the signal to the signal source after a predetermined first period has elapsed after receiving a request to transmit the signal from the signal source. means for supplying a clear-to-send signal to permit the transmission; and means for fixing the signal supplied to the randomizing means to a particular signal mode within a predetermined second period before the clear-to-send signal is supplied by the means. and on the receiving side, within the second period in which the signal is fixed on the transmitting side, and after a predetermined third period has elapsed since processing by the equalization means was started. means for counting the number of signals obtained by the decoding means that are in a signal format other than the specific signal format,
A signal quality testing method characterized by evaluating signal quality based on the counting results obtained by this means.