Kulyk A.Y., Polic A. A.

Vinnitsia national technical university

Adaptation of the device transmitting information to the parameters chennel in terms of its unsymmetrical

for control and measurement system

 

The main problem during the transfer of information is that increasing the probability of requiring speed reduction transmission, and reduces the possibility of increasing the speed [1 ,2]. During the analysis of communication channels is that channels are symmetric, ie the probability of distortion of zeros and ones in the communication channel p (0 / 1) and p (1 / 0) are the same. Accordingly, the chart looks like the signal levels is shown in Fig. 1, a threshold level identification signal is set at half its amplitude.

 

 

Fig. 1. Diagram of signal levels for symmetric communication channel

 

However, in real systems and networks more often asymmetrical channels for which the conditional probability distortion symbols p (0 / 1) and p (1 / 0) unequal. Given the large number of factors influence analytically calculate the numerical values of these probabilities is difficult. Consider symmetric channels means immediately enter methodological error, worsening terms of the identification signal.

The positive effect is testing transmission channels sequences of zeros and ones with the definition of probabilities and the determination of optimal threshold levels identify logical "zero" and "unit Because to date to facilitate the analysis of communication channels was assumed that they are symmetrical, then this task is not put into practice and not considered for theoretical studies, although it is very real for unipolar transmission mode. For bipolar mode, these probabilities are converted to the probability of errors of the first ð²  and  ð²²  second kind.

Given the large number of independent factors that affect the signals during their formation, transfer, recovery and identification, it is highly likely to be considered, the voltage signal in the communication channel is a random variable with normal distribution. It centered on U, when transmitted "one", and to 0 when transmitted "zero" for the first case under consideration or under when transmitting an information signal and in his absence for the second case. Therefore, conditional probability of receiving a symbol "0" when transferred to "1" equals the probability that the voltage at the input of the receiver is below the threshold of Us. The expression for this probability will be:

 

.                          (1)

Similarly, the conditional probability of receiving a symbol "1" when handed over to "0" will be:

.                    (2)

Substitution variables can get the formula:

,                                     (3)

.                                      (4)

If an asymmetric channel, the conditional probability distortion character data for the specific conditions of transfer are related:

.                                         (5)

Then, taking into account formulas (5.46) - (5.49)

                                        (6)

From the expression (5.51) can be obtained

U - Us =  × Us                                              (7)

 ,                                                 (8)

where U - the amplitude of the signal in the communication channel.

Because of the same communication channel ratio will vary depending on the speed of transmission, signal amplitude, etc., then the test channel, you must perform in those conditions that will be implemented to transmit informative data.

Based on the foregoing, the implementation of this method requires the adaptation of a list of actions:

- allocate a channel of communication through the serial interface and modem binary test sequence;

- accept from a selection of system test results communication channel;

- read from the media PC data to be transmitted;

- transfer in sequential code to interface data;

at the receiving side:

- obtained from the channel of communication via modem and serial interface binary test sequence;

- determine the coefficient unsymmetrical communication channel according to formula (6);

- calculate the threshold level identification signal according to formula (8);

- pass on the transmission side of the results, which indicate the end of the first stage;

- determine in accordance with the speed of transmission time intervals identification of informative signals and record them in a timer;

- measured at fixed intervals voltage levels in the communication channel;

- read measurement information;

- compare with the specified voltage threshold level and identify the level of the signal;

- write the information to the media PC.

Implement this method using classical micro structure [2]. In this case, the proposed mode survey software channels, although the implementation can be done with certain changes and for any other.

Scheme of the device shown in Fig. 2.

 

Fig. 2. The structure of the device implementation method adaptive information transfer

 

When you turn the power on the transmission of the CPU 7 personal computer 9 performs the initialization of the device so that the serial interface 4 programmatically configured to set the transmission speed information channel C parallel interface 6 - for output, and channels A and B - on data input, programmable timer 5 is configured to interrupt the terminal mode counting.

The first stage is testing a communication channel, for which it via serial modem 4 and 2 passed the test sequence of "zeros" and "units" that are at the receiving side of the modem 2 arriving on serial interface 4.

The CPU 7 9 PC reads data from serial interface 4 and writes them to the operational storage units 11, and then calculates the ratio unsymmetrical channel according to formula (5.50).

According to formula (5.53) calculate the optimal value of threshold voltage identification signals Us, that the real value of noise in the communication channel 1. These results are transmitted to the transmitting part, which indicates the completion of testing communication channel 1. At the second stage of the CPU 7 9 PC reads data bytes from the storage medium 10 and by a serial interface 4 and 2 modem transmits them to the communication channel 1.

On the receiving side, based on the speed of transmission time intervals calculated levels of identification signals from the communication channel 1. To counter the programmable timer, 5 recorded a number that is calculated by the formula:

,                                        (9)

where f0 - clock frequency programmable timer counter 5;

τi - i-th time interval identification signal communication channel 1;

υ - speed transmission of information communication channel 1.

The first high level voltage signal coming from a communication channel indicates that it will come after zero bytes and information. Controlling time intervals identification data by using the programmable timer 5 in reading mode "on the fly." When the counter value in Ni is launched analog-digital converter 3 by a signal "Start" channel through C parallel interface 6. The signal "End of conversion" that comes from analog to digital converter channel 3 on a parallel interface 6, shows the complete measurement of the current value signal Ui and install the channel A parallel interface 6 voltage value in digital form:

 .                                     (10)

Observed values of the signal is compared with threshold Ui Us and identified as "zero" or "unit" depending on the amplitude. Local cycle continues until the eight informative bits of bytes will not be identified, then the data byte written to the operational storage units 11 PC 9.

The process continues for as long as all information will be obtained, after which it is written to the storage medium 10 PC 9.

The method was tested during the implementation of the NTB, as well as at "Navionika", "VinnytsyaHaz" and bank "Petrocommerce-Ukraine".

The method will be implemented based on the MSP430 microcontroller developed by Texas Instruments. This is due to the fact that the microcontroller (MC) MSP430 made on the basis of 16-bit RISC LAC with 27 instructions and 7 addressing modes, peripherals and flexible synchronization. Power controller connected tires and tire data address the total Fon-neymanovskoyi memory (MAB and MDB respectively). Combining modern CIE with modular analog and digital peripherals on MSP430 MCUs orients mixed signal processing applications. MSP430 is a very economical MK, because they are widely distributed in the 8 - and 16 bit measurement applications with battery powered.

 

References:

1.                 Êóëèê À.ß. Àäàïòàö³ÿ ïðèñòðîþ ïåðåäàâàííÿ ³íôîðìàö³¿ äî ïàðàìåòð³â êàíàëó â óìîâàõ éîãî íåñèìåòðè÷íîñò³ / À.ß. Êóëèê // Âåñòíèê Õåðñîíñêîãî ãîñóäàðñòâåííîãî òåõíè÷åñêîãî óíèâåðñèòåòà. – 2004. – ¹ 1 (19). – Ñ. 418 – 422.

2.                 Ïàòåíò 71202À Óêðà¿íè, ÌÏÊ7 Í03Ì 13/00. Ñïîñ³á ïåðåäàâàííÿ äèñêðåòíî¿ ³íôîðìàö³¿ ç àäàïòàö³ºþ äî óìîâ ïåðåäàâàííÿ òà ïðèñòð³é äëÿ éîãî ðåàë³çàö³¿ / Êóëèê À.ß. (Óêðà¿íà); ÂÍÒÓ. – ¹ 20031210868; çàÿâë. 01.12.2003, îïóáë. 15.11.2004, Áþë. ¹ 11. – 7 ñ.

3.                 MSP430x2xx Family User’s Guide - Austin: Texas Instruments Incorporated, 2008 – 693c.

4.                 Ìèêðîêîíòðîëëåðû MSP430 êîìïàíèè Texas Instruments c Flash-ïàìÿòüþ [Åëåêòðîíèé ðåñóðñ]: (Êàçóñ) – Ðåæèì äîñòóïó: http://www.e-tools.info/ index.php?page= component_detail&id=10880

5.                 MSP430FG4618 - îïèñàíèå [Åëåêòðîííèé ðåñóðñ]: (Êîìïýë) – Ðåæèì äîñòóïó: http://mcu.compel.ru/mcu/MSP430FG4618IZQW

6.                 Ïðîãðàììèðîâàíèå ÷åðåç èíòåðôåéñ JTAG [Åëåêòðîííèé ðåñóðñ]: (Ðûíîê ìèêðîýëåêòðîíèêè) – Ðåæèì äîñòóïó: http://www.gaw.ru/html.cgi/txt/doc/micros/ avr/arh128/19_3.htm