The triune essence of two-way communication. What is a car alarm starline b62 Remote control door locks

Methods for monitoring the state of the communication channel differ primarily in the criteria used to assess the state of the communication channel. Such criteria can be the type of the impulse response, the error rate per element, etc. In the latter case, it is reasonable to talk about the evaluation of the quality of a discrete channel, meaning by this an assessment of the degree of suitability of a channel for transmitting discrete messages. Direct and indirect methods can be used to determine the error rate.

The direct method involves determining the error rate by counting the number of erroneous elements in a sequence of elements known in advance at the reception in the analysis interval

where is the number of erroneous elements in the analysis interval; N is the number of elements transmitted in time T. The error rate is an estimate of the error probability, denoted in the following

Indirect methods for estimating the quality of channels are based on using the relationship between errors and distortions of the waveform and involve counting the number of distorted signals with subsequent determination. Regardless of which method is used, the task is to obtain a short time an estimate of the probability of error. The accuracy of the resulting estimate can be characterized by the variance of the error probability estimate. Obviously, the best of the two considered methods for estimating the quality of the channel will be the one that, for a given sample size (analysis interval), gives a smaller value of the variance of the estimate.

At direct method over the channel it is required to transmit a sequence known at the reception, which is called a test. Therefore, the method is often called a test method. Indirect methods do not require the transmission of a test sequence over the channel, and therefore are called testless. The use of testless methods for estimating the quality of channels is more preferable, since in this case the quality of the channel is evaluated in the process of operation and on the basis of working signals.

When transmitting a test sequence over a discrete channel

where if there are errors otherwise. The resulting estimate is unbiased, i.e., the mathematical expectation of the random variable is equal to The variance of the estimate is determined by the expression

The assessment of the channel quality when using the testless method, as already noted, is carried out based on the results of receiving working signals.

Let for each of N single elements in the analysis interval, it is possible to determine the conditional probability of incorrect reception , where H - means incorrect (erroneous) reception, and Y - signal at the reception. Then

The resulting estimate is also unbiased, and the variance of this estimate, as shown in , is less than that of the test method. Thus, when using the test-free method, it is possible to obtain a smaller value of the estimate variance for a given analysis time or, for a given value of the estimate variance, to obtain an estimate for the error probability in less time.

Consider another simple indirect method for estimating the quality of a channel based on counting the number of erased single elements in the analysis interval . Let us assume that fluctuation interference with a known dispersion acts in the channel. In this case, let the error probability be determined by the formula (see Chap. 6)

Let where ( - signal distribution density at the demodulator output when transmitting "0" and "1", respectively (Fig. 8.2). Then

where is the Krump function. For a given erasure threshold A, the probability of erasing a single element

The error probability is a function of a or o. The erasure probability also depends on the threshold A. Determining the number of erasures v on the analysis interval of N elements, we can find an estimate for the element erasure probability and from the equation

for given values ​​of a and A, determine a.

Rice. 8.3. Error probabilities for three channel states

Substituting the found value a in (8.1), we determine the error probability

Data on the number of erasures in the analysis interval can also be used to separate channel states. Let the channel be in one of L states, each of which is characterized by an error probability per element . We also assume that the erasures are independent. Then the probability that the number of erasures for the channel state is equal to v in the transmission interval of N 1s is given by

where is the element erasure probability for the channel state. Typical dependency graphs in the case when the channel can be in one of the three states are shown in Fig. 8.3. The graphs correspond to the case From the graphs it follows that if the number of erasures then it is most likely that the channel is in state I (the error probability is equal to since With the number of erasures, it is advisable to assume that the channel is in state II.

Thus, we believe that the first state corresponds to the second and third wrong decision about the state of the channel. For example, if a decision is made that the channel is in the first state, then in fact it, however, could be less likely to be in state II and even III. To evaluate the quality of channel state separation, a matrix can be used where is the probability to decide that the channel is in a state when in fact the state is.

When separating the three channel states

The ideal separation of channel states corresponds to the case when and all other elements of the matrix are equal to zero. Of course, such a separation is not possible.

The considered methods for assessing the quality of channels are far from exhausting all possible ones, the description of which is devoted to many articles and monographs.

According to the place of inclusion of control devices, they distinguish adaptive systems PDS with control devices switched on for transmission, reception or transmission and reception at the same time. Most often, control devices are turned on at the reception, and information about the results of control (if necessary) is sent via a feedback channel to the transmitting end.

According to the analysis time of the channel state, PDS systems with constant and variable analysis time are distinguished. In the latter case, the analysis interval depends on the quality of the channel, while the higher the error rate, the faster the decision on the quality of the channel can be made.

Monitoring can be carried out in order to make a decision about the quality of the channel only on the monitoring interval. This is the so-called current control. It can be interpreted as signal quality control. An example of such control is the determination of the correctness of its reception in relation to each code combination. Monitoring can also be carried out in order to determine the quality of the channel in the stationarity section based on the results of measurements over a time interval significantly shorter than the stationarity interval. In this case, the task of monitoring is to predict the state of the channel

If the current control, as a rule, is intended to improve the conditions for receiving the signal, based on the results of the analysis of which a decision was made about its quality, then the prediction is aimed at changing the PDS system, providing the required quality indicators of the system after the decision is made.

Use of control results. According to the results of the control, the parameters of the UPS or RCD, or both devices at the same time, can change. The issues of adaptation related to the UPS were discussed in Chap. 6.

When adapting at the RCD level, there are: adaptive coding and adaptive decoding. With adaptive coding, the structure of the code changes in accordance with the state of the channel - the ratio between the number of information and check elements, the length of the block, etc. A variant of the simplest adaptive coding is to repeat the code combination when an error is detected in it. Systems in which the repetition of code combinations occurs when errors are detected in them are systems with an OS. These systems are most often used in practice, so they are discussed in detail below.

If, in non-adaptive decoding, the decision on the type of transmitted code combination was made unambiguously at the reception, since each syndrome was assigned one most probable combination of errors, then in adaptive decoding, each syndrome corresponds to N variants of a combination of errors, where N is the number of channel states. Thus, the decision on the accepted combination for the same syndrome depends on the state of the channel.

Since errors are possible when making a decision about the state of the channel, then optimal solution about the code combination can be accepted with a probability different from unity and depending in turn on the quality of the channel (signal) quality control device.

Recently, I suddenly caught myself thinking: I haven’t heard a sound for a long time car siren... But just recently, falling asleep, I regularly heard the howl of one or two sirens in the vicinity of my house.

And after all, there were no fewer cars, on the contrary, if earlier it was not difficult to park near the house, now it is a whole problem. And almost every car must have an alarm ... And then it dawned on me - after all, the alarms now in the bulk have become two-way. So now the owner of the car does not rely on "mythical" passers-by who will frighten off the car thief upon hearing the siren, especially since it is somehow hard to believe. And today, by the way, on the way to work, I generally witnessed a comic picture: some young man tried to open the windows with a ruler, apparently, of his own, not very new foreign car. And passers-by walked by, not paying the slightest attention to him. So, in the current conditions, you can only rely on yourself and your quickness.

So, car alarms have become two-way, and the main notification channel is no longer a siren, but a two-way pager channel. That's what we'll be talking about.

Undoubtedly, the majority of car owners, looking at the painted car on the screen of their "Bilarm" alarm system, are convinced that now they have become the owners of the most modern security system with two-way communication.

But few people think about what this very two-way connection generally depends on.

But this is an ordinary radio channel, which is subject to all the effects of radio magnetic interference inherent in a big city. And believe that the air in any big city extremely polluted (like the whole environment around us). Radio interference in a big city reaches such a level (checked, and not just checked, but carried out a whole series of tests) that it is generally incomprehensible how anything can work at all. But it works! It just works differently...

And the ether is really polluted, and for notification there is only one single frequency with a band of 433.92 + 0.4%. And this despite the fact that there are more and more cars, and, accordingly, the workload of the radio air is simply unprecedented. And there is nothing to say about the radio broadcast around hypermarkets.

So it turns out that it directly depends on the quality of the radio channel, or rather, on the presence of a stable and long-range radio channel (subject to the presence of automatic control of this very radio channel), whether the signaling will fulfill its purpose or not.

In general, it is necessary to clarify that the radio channel has 2 ranges:

  • pager range (alert range)
  • command range (control range).

The pager range should be considered security function, since it directly depends on this very range whether you receive an alarm message or not. And this is the most important thing. And the command range should be considered a service function, because it is used to perform actions such as remote start engine and more.

Thus, it depends on the quality of the radio channel whether you receive an alarm at this very moment of truth (that is, at the time of a criminal attempt on your car) or not! That is, it is the quality of the radio channel that now determines the quality of the two-way signaling itself.

Channel control

Now it makes sense to turn to the history (of the radio channel). The pager communication itself and, accordingly, the channel control has been around for about 15 years. Why haven't security systems with this same channel control become widespread yet? Although it is obvious that two-way systems are needed in order to be sure that my car is in the coverage area of ​​two-way communication (more precisely, its pager component, which determines the alert range) and, accordingly, I will be guaranteed to be warned about a criminal encroachment on my car.

Otherwise, why do we need two-way communication at all?

So: in view of the fact that the circuitry solutions of that time were unsatisfactory, the connection was also unstable, and since the pager lost connection all the time, this naturally caused irritation and a legitimate desire to turn off this source of anxiety.

But time does not stand still. Over 15 years of continuous and hard work, the engineers of Magic Systems managed to solve this problem, and at present an outstanding connection in terms of stability has been achieved, which made it possible to implement automatic channel control ( automatic check location of the key fob in the reception area alarms from the alarm installed on the car).

Automatic channel control and only automatic (and not forced, which, without further ado, invented by some manufacturing companies) gives absolute confidence that at the right time the necessary information will be reported to the owner, and the absence of messages ensures that everything is in order with the car.

And it is important to remember that in order for the radio channel control to work stably, two conditions must be met: range + noise immunity.

Now let's calculate: channel control is sending a radio signal once every 90 seconds, which is displayed on the key fob with a glowing antenna icon. This means that the channel is checked once every 90 seconds. As a result, we get 40 connection checks per hour, and 320 per night, for a total of 320 x 365 = 116816 per year.

So: my alarm system Stalker-600 NBV never woke me in vain for a year, although the car was parked 300-500 meters from the entrance. This is what I call a stable connection and a stable radio channel.

Now a little about the parameters: the range of the pager channel of the Stalker is 3 km, and the range of the command channel is up to 1200 meters. Many people ask me: why do you need a range (alerts) of 3 km - after all, you still won’t have time to run? (Although, if my car is in danger, then I will run!)

I answer competently: in the conditions of the city, the radio signal is significantly weakened compared to ideal conditions, in which the range of car alarms is measured, which is indicated in the instructions and on the packaging.

In general, three main factors affect the transmission of a radio signal:

  • radio channel quality
  • interference on the air
  • the presence of obstacles (in the form of houses, buildings, etc.)

And if we can still deal with interference by improving the radio channel, then obstacles, whatever one may say, can weaken the radio signal by 2-3, or even 10 times.

Therefore, if your alarm has a communication range of 3 km, then even in the worst conditions, you will have a reliable connection of 300 meters, which is quite suitable for parking, which cannot be said about alarms with a declared range of, say, 500 m.

Thus, we can state the following: who has a more long-range channel in open field, it will be long-range and in real urban conditions.

The whole difficulty is that parameters such as range and noise immunity are technical parameters, and the consumer does not have the opportunity to explicitly touch them, feel them, unlike, say, from appearance keychain, which, by the way, the buyer very often leads, making his choice of alarm design (which is often the main selection criterion for most consumers), the keychain they like!

What a game!

So it turns out that it is possible to evaluate them (range and noise immunity) only in practice (and practice, as you know, is the criterion of truth!), only in comparison ... Which was done by a number of St. Petersburg independent campaigns that tested the most popular brands of two-way alarms for range . You can read more about the testing itself and its results.

After analyzing the results of this study, we can state: firstly, the control of the radio channel is vital. Secondly, in order for the channel control to be efficient, it is necessary that it has a high range and noise immunity. Moreover, noise immunity is, perhaps, of decisive importance.

How did you manage to solve the problem of noise immunity in Stalker? First: it is a narrow band (there is less chance of interference). Secondly, mathematical processing is used with the help of an expensive processor using noise-like signals.

Summing up

It turns out that only now, for the first time in the entire existence of channel control (15 years), Magic Systems managed to create an outstanding radio channel in terms of range and noise immunity, implemented in the Stalker-600 NBV.

And now it’s enough just to look at the key fob (on which the antenna icon is lit) to be absolutely sure that everything is in order with your car, which means that the presence of such a radio channel gives absolute peace of mind to the owner of a car equipped with such a system.

And at the end of the article, you can return to the title: "The Triune Essence of Two-Way Communication" and summarize once again that the first thing you need to ask when buying a two-way system is:

  • the presence of channel control (automatic);
  • significant range of the communication channel (3 km for notification and 1000 m for control);
  • high noise immunity of the radio channel (see study).

In general, it turns out that today channel control has become one of the main criteria for choosing two-way car alarms.

Automotive Star Line alarm B62 is equipped with a dialog box to authorize the owner. It may also be included in anti-theft complex like "Win". Via security system StarLine B62 Dialog can reliably protect the car, because it is equipped with automatic control over the communication channel, it is very convenient and easy to use, it provides complete protection for the vehicle.

Both main and additional key rings alarms are very reliable and ergonomic, the reliability of their design provides a hidden antenna and innovative design. Instructions for Starline operation B62 is informative, and it is useful to read it not only for beginners, but also for professionals. After all, the instructions can tell in detail about the installation and configuration of the security system.

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This car security system provides a full set of security, service functions, as well as interactive authorization. So, dialog code control with personal keys 128 bits long is able to exclude intelligent electronic hacking, it is resistant to all available code grabbers. In order to protect the code, the most advanced algorithm is currently used dialog coding, as well as the innovative frequency hopping method. In this method, when transmitting commands, a specialized transceiver changes frequencies many times according to a special program at the moment of each message.

A solution of this level, also known as such technical term: "a method of possible spreading of the spectrum with frequency hopping" is used for the first time in a car alarm control system and is a significant complication of attempts to crack the existing code.

Megapolis mode

The possibility of increasing the immediate range of control and notification, as well as confident operation in urban radio interference is provided by the use of a 512-channel narrow-band transceiver with frequency modulation, a narrow bandwidth.

Availability specialized program signal processing, narrow-band filters, as well as receive and transmit channels optimally distributed along the edges of the 433.92 MHz band, made it possible to improve the signal-to-noise ratio signal and increase the range and noise immunity.

Automatic link control

The verification of the location of the key fob in the zone of direct action of the alarm transceiver is provided and the receipt of alarm signals from the vehicle is guaranteed. If necessary, it is possible to select the frequency of transmission of control signals every 3, 5, 7 minutes. or temporarily disable communication control.

Ergonomic, reliable keychain

Keychains have an innovative design, hidden antenna location. This makes it possible to increase the reliability of the key fob design and implement an ergonomic control method. So, in the new 4-button control interface, the principle of the “main button” is used. The main button, which is easily found, performs such main team alarms, such as arming.

Comfort

Key fobs implement an intuitive and easy control principle. The pictograms presented on the keychain are in Russian. Via LED backlight comfortable work with information data on the display is provided.

Complete protection

We use the encryption code both mainly and in additional keychain. Available additional functions. User functions have been added to detect the voltage of the car battery, view the history of alarms with a direct indication of the time of the event, select the volume of the key fob and select the melody. For the first time in alarm systems, it is possible to receive quiet confirmation signals on conventional 12 V sirens.

Benefits of installing a car alarm

The algorithm for direct programming of functions has been modernized. Online on the key fob display you can now see the function number itself with its programmed value.

The management of existing additional channels has been modernized, which made it possible to install StarLine system B62 for all modern cars.

In order to increase anti-theft protection, digital wireless interlock relays can be connected.
Any of the 4 additional channels can be programmed to generate any number of control pulses, which makes it easier to install alarms on current cars and implement additional service functions without the use of external components.

Car alarm kit:

  • central block;
  • key fob with two-way communication with LCD;
  • key fob with two-way communication without LCD;
  • 2-level shock sensor;
  • hood button;
  • transceiver;
  • service button;
  • Light-emitting diode;
  • set of wires;
  • user memo;
  • installation instructions;
  • user manual.

This is what the StarLine B62 car alarm is famous for.

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