JPS6162255A - Method of measuring bit error rate of tdma circuit - Google Patents

Abstract

PURPOSE:To enable to measure bit error rate BER corresponding to the state of radio circuit by making a receiving station exclude received data code of burst signals for which starting signal is not detected correctly from object of measurement and thereby counting bit errors generated in data burst without influenced by bit errors generated in the starting code of the burst signals. CONSTITUTION:An FIFO buffer 1 is so constituted that when a starting code is not detected correctly by a control signal 103 from a receiving device, it stops writing equivalent to one data burst. A PN (pseudorandom) code generator 2 generates a PN code similar to transmission side. When a bit error occurred in the starting code during measuring, writing of data burst following the starting code in the FIFO buffer 1 is stopped. Accordingly, BER that reflects actual state of a radio circuit can be measured counting bit errors (BER) excluding data burst that generates apparent bit errors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the bit error rate of a TDMA line.

[Conventional technology]

Conventionally, the bit error rate (abbreviated as BER) has been used to evaluate the transmission quality of digital wireless lines such as PCM lines. The output of a PN code generator installed on the receiving side that generates the same PN code as that on the sending side is compared with the received reproduction code reproduced on the receiving side, and the output is compared for a certain period of time (number of focus) This is done by counting the bit errors between.

[Problems to be solved by the invention]

In recent years, time division multiple access (TDMA), such as multidirectional multiplex wireless communication lines, has been used not only in satellite communications but also in terrestrial communication systems.
As wireless lines using this TDMA system are becoming more widespread, it is necessary to evaluate the line quality of such TDMA lines. In a TDMA line, each burst signal includes a preamble part used to reproduce carrier and bit synchronization, and a start code (also called a unique word) consisting of a specific code string to confirm synchronization and identify the transmitting station.
Normally, the receiving station detects and confirms the start code before sending out the data burst to the receiving output, and does not send out the receiving output if the start code is not detected correctly. It is configured as follows. Therefore, if the BEH of a TDMA line is measured using the method used for conventional PCM lines, if an error occurs in the start code of a burst signal at the receiving station, subsequent data bursts may be completely dropped. There are 5 problems in that even if there is no abnormality in the data burst, it is counted as having a large number of errors.This means that large fluctuations occur in the measured data even if there is little change in the condition of the wireless line. Therefore, it is inappropriate for the purpose of evaluating the quality of wireless lines.The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to always obtain the same measurement data as long as there are no changes in the wireless line conditions. An object of the present invention is to provide a method for measuring the bit error rate of a TDMA line that can be used for quality evaluation of a TDMA line.

[Means to solve the problem]

The bit error rate measurement method of a TDMA line according to the present invention is as follows:
A transmitting station on a TDMA line that transmits information using the TDMA system sends a pseudorandom table code to a predetermined position of a data burst following the start code of each burst signal, and a receiving station receives and reproduces the received and regenerated code.
2. In a bit error rate measurement method in which bit errors are detected and counted by comparing the received data code at the predetermined position of the j1-st signal with the pseudorandom code generated at the own station and the same as that on the transmitting side. , the receiving station is provided with an exclusion means for excluding from the measurement target the received data code of the burst signal in which the start code is not correctly detected.

[Effect]

Next, the present invention will be described in detail with reference to the drawings.

First, the technical idea of the present invention will be explained with reference to the signal configuration diagram of FIG. Figure 1 shows an example of TDMA signal transmission in which each burst signal transmits one telephone channel, and each burst signal B, B, B, ... each has a 16-bit preamble. part Pi, a 16-bit start code Si, and a 128-bit data burst D.
It is composed of i. Now, assume that the transmitting side sends out a PN code for measurement on this telephone channel, and the receiving side collates it to determine the BER. That is, each dataverse N),,D,.

Bit errors are detected only in D, .
The BER is determined by counting (while the bit is 0'). However, as mentioned above, if a bit error occurs in the start code Si other than the target data burst Di, for example, in the start code S2 of the burst signal B,
Since the KTDMA line is configured to output the data burst signal after verifying the start code, the received output for 128 bits of data burst D2 following S is '1' or '0'. Since this is a series of either of the following, and almost half of the distributions are different from the PN code (1" and 10" distributions are 50% each), errors of 60 bits or more are counted.One method to eliminate this inconvenience is to The method is to add a means to the receiving side to exclude the data burst D of the burst signal whose start code has not been detected correctly from the measurement target, and to prevent the error of this data burst from being counted.In this way, the reception output can be used to count only the bit errors in the data burst Di to accurately reflect the status of the wireless link, and can be used to evaluate the link quality.

〔Example〕

FIG. 2 is a block diagram of the receiving side according to an embodiment of the present invention, including a first-in, first-out FIFO buffer 1 that temporarily stores received data, a PN code generator 2 that generates the same PN code as that on the transmitting side, and a clock signal. a clock control circuit 3 to control;
EX-OR circuit 4 for detecting bit errors; BER counter 5 for counting focus errors; clock counter 6 for determining counting time. It is composed of. The reception output 100 of the telephone channel used for measurement is sequentially written into the FIFO buffer 1 by the channel clock 101 (also 32) of the receiving device, and the written data is read out in the order in which it was written by the read clock 102. The output of the PN code generator 2 is compared with the EX-OR circuit 4, and if there is a difference between the two, an "1" pulse is generated and counted by the BER counter 5. The reception output 100, channel clock 101 and control signal 103 are also supplied to the receiver f and f at the start of measurement.
The read clock 102 of the FIFO buffer 1 starts writing and reads data after n data bursts (128Xn bits, n is selected to be larger than the expected number of start code errors during the counting time) are accumulated. It is controlled by the clock control circuit 3 to start. FIFO buffer 1 receives control signal 10 from the receiving device.
3, if the start code is not detected correctly, writing for one data burst is stopped. The PN code generator 2 is a PN code generator that generates the same PN code as that on the transmitting side. For example, a 1-bit PN code is added to the (2'-1) bit PN code of an m-sequence linear code generator consisting of a 7-stage shift register. It is configured to repeatedly send out a 128-bit code by adding "0" (or '1#), and is driven by the read clock 102 of the FIFO buffer 1.

The clock counter 6 counts the total number of read pulses, and is provided with a button to stop the counting of the BER counter 6 when the count reaches 107t. According to this circuit, the focus error occurs on the start code during measurement.

occurs, the data following the start code
i,... (In order to stop writing bursts to FIFO buffer 1, exclude data bursts in which apparent bit errors occur, count bit errors, and measure BER that reflects the actual state of the wireless line. I can do it.

In the embodiment shown in FIG. 2 described above, reading from the FIFO buffer 1 is performed continuously, and when a start code cannot be detected, only writing of data bursts is stopped. If a control line as shown in is added and the clock control circuit 3 is used to control the reading of 128 bits to be stopped at the same time as writing, the number of burst signals in which an error occurs in the start code will increase and n will be reduced. Even if the data burst is exceeded, the data burst written in the FIFO buffer 1 will not become empty, and the memory capacity of the buffer can be designed to be small. Furthermore, in the embodiment shown in FIG. 2, the writing and reading of data in the FIFO buffer 1 is performed using the telephone channel clock (32 phantom clock).
The data can be written not from the telephone channel output of the receiving device but from an intermediate processing stage, and can be configured to be written using a high-speed clock or written in multiple bits in parallel instead of serially. Furthermore, although the embodiment of FIG. 2 is configured to stop writing received data symbols of data bursts to be excluded from measurement using a first-out, first-in FIFO buffer, the embodiment of FIG. Although comparison and verification are performed using bits, a gate circuit may be provided on the input side of the BER counter 5 and controlled by the control signal 103, and a circuit may be constructed in which bit errors in data bursts to be excluded are not counted. In this case, it is not necessary that the same PN code be repeatedly transmitted for each burst signal as shown in FIG.

In the above explanation, each burst signal on the TDMA line is assumed to be transmitted over one telephone channel, and a PN code is sent to all data bursts for BER measurement, but all data bursts are not necessarily used for measurement. There is no problem even if you don't have it. For example, if two telephone channels are transmitted in one burst signal, each channel has 256 bits of 128 bits.
If there is a data burst of bits, the measurement PN
It is possible to measure whether the code is sent to 128 bits for one channel or 256 bits for two channels, and in either case, the same exclusion means as described above is added.
Measurement can be performed by excluding burst signals in which an error has occurred in the start code.

〔Effect of the invention〕

As explained above, according to the method of measuring the bit error rate for eight TDM cycles of the present invention, the bit error rate measurement method using the telephone channel input/output of the TDMA line can be used to measure the bit error rate by using the input/output of the telephone channel of the TDMA line. This method has the advantage of being able to count only the bit errors that occur in data bursts and measure the BER that corresponds to the state of the wireless line. Note that this method does not affect anything other than the telephone channel used for measurement, so there is no need to stop system operation (there is an advantage that the BER of the wireless line is required).

[Brief explanation of drawings]

FIG. 1 is a signal configuration diagram showing an example of a burst signal configuration of a TDMA line, and FIG. 2 is a block diagram of a receiving side measurement circuit according to an embodiment of the present invention.

Claims (2)

[Claims] (1) A transmitting station of a TDMA line that transmits information using a time division multiple access system transmits a pseudo-random code to a predetermined position of a data burst following the start code of each burst signal, and a receiving station receives and reproduces the pseudo-random code. In the bit error rate measuring method of detecting and counting bit errors by comparing the received data code at the predetermined position of the burst signal with the pseudorandom code generated at the own station and the same as that on the transmitting side, the receiving station 1. A method for measuring a bit error rate of a TDMA line, comprising an exclusion means for excluding the received data code of a burst signal whose start code has not been correctly detected from measurement targets. (2) The code length of the pseudo-random code is selected so that the same code is repeatedly transmitted for each of the burst signals, and the exclusion means includes a first-in, first-out buffer circuit, and the burst in which the start code is not correctly detected; The T according to claim 1, characterized in that it is configured to stop writing the received data code of a signal.
A method for measuring the bit error rate of a DMA line.