Wireless telemetry systems are gradually becoming more widespread in industrial and utility facilities. Using a wireless data channel has a number of advantages over traditional wired lines. The main one was the lack of the need for cabling between the control room and the telemetry facility. In modern realities, laying any long cable route is very expensive, especially if the route crosses existing communications or natural barriers. A huge number of necessary approvals complicate and increase the cost of the task even more. The cable itself also represents a bottleneck in the system. It is subject to mechanical damage, and can also be trite stolen. The use of ready-made telephone or similar communication lines is not always advantageous in view of the poor quality of communication and the high subscription fees charged by telecom operators.
The solution to the problem of providing communication lines is the use of wireless data transmission. To date, the two types of similar systems that differ in some operating principles are most widely used. The first of them uses data transmission at a frequency of 433 MHz, the second is based on the use of GSM cellular stations.
The main advantages of communication at a frequency of 433 MHz is the complete absence of information transmission costs. With the right equipment, a license to use the frequency is not required. The user only needs to mount the communication means and start transmitting data. The negative side of this approach will be the limited allowed transmitter power and, accordingly, the low communication range. Also in some regions, this channel is very noisy with a lot of working devices.
433MHz equipment is relatively cheap and easy to use. A modern radio modem is a ready-made communication device, which is enough to connect to the equipment via the COM port and make a little configuration. After that, he is ready to work with data. But in addition to the modem, in most cases, a special antenna is required, characterized by many features of the installation.
Communication via the GSM channel is somewhat more complicated, although the user may not notice this. It also does not require any permissions, just purchase a GSM modem and SIM card. But unlike direct communication, it is necessary to conclude a contract for communication services, on the basis of which the operator will require regular payments. Often the size of this board depends on the amount of information transmitted, which can be very expensive. The second negative point is the dependence of communication quality on the work of the operator. Today, it is not uncommon for network congestion, failure of cellular base stations and other negative situations. And the operator himself can suddenly turn off the transmitter. The likelihood of such events increases during periods of mass holidays and riots, as well as natural disasters, that is, at a time when high-quality communication may be urgently needed. Also, the GSM channel does not provide for continuous operation. If continuous transmission of information for a long time is required, it is better to choose another method. With all this, communication according to the GSM standard has a lot of advantages. It allows you to transmit information over long distances, without spending on additional equipment. A wide coverage area makes it possible to provide a stable signal in hard-to-reach places, for example, in urban areas. Also, the GSM-channel does not require a solid antenna economy and allows for telemonitoring of moving objects. Continuous improvement of technologies leads to a constant increase in the data transfer rate via GSM, which can also be a significant advantage.
In terms of equipment cost, both communication methods are at approximately the same level, which does not allow using this criterion for the final choice. Summing up, it can be said that if it is possible to periodically poll remote devices, GSM communication will be a good choice, and for nearby objects in direct visibility, you can use radio modems operating at a frequency of 433 MHz.