RF signals (waves) travel almost forever and pass through many solid materials (though their strength does get reduced due to path loss and absorption). Therefore, they cannot be easily contained within a desired space, nor can we ignore the effects of radio signals transmitted by devices located in a long distance, even thousands of feet, away. These devices can interfere with your RF system, and your system can interfere with them. These types of interferences affect the performance of an RF system. They may, depending on their relative strength, reduce the read range of your system or render the system inoperable.
Another reason to control RF transmission is to avoid injuries to humans and animals. RF devices transmit and receive RF energy. For example, Wi-Fi devices operating at 2.4 GHz range, which is the same frequency a microwave oven uses, can seriously damage human tissue if they transmit a signal at a very high level. In a low strength, they are considered harmless. A regulation must be established as to the level of safe exposure, and some mechanism has to be created to certify and monitor compliance.
RF regulations typically vary from one country to another or from one region to another, due to the legacy usage of various portions of RF spectrum. In the technology’s early years, various countries or regions assigned different chunks of the RF spectrum for different uses. No worldwide standard was available, and even now none exist for many parts of the spectrum. Finding a worldwide RF range for new RF applications is a problem. For example, in the US, the UHF RFID systems are allocated a frequency range of from 902 to 928 MHz, but in European countries, that range was already assigned to other uses and is therefore not available. In Europe, UHF RFID systems are assigned frequency range of 865 to 868 MHz. As a result, a tag designed for the US will have problems being read in Europe and vice versa. To overcome these problems, RFID systems must be designed to incorporate all the frequency ranges (within the UHF band) used all over the world. This has been accomplished by EPCglobal Gen-2 and ISO 18000-6C standards. Readers and tags designed according to these standards will interoperate anywhere in the world.