RFID tags and readers communicate with each other via radio frequency waves. The bands used vary from country to country and the deployed hardware. As a general rule individual countries have their own regulator and differing frequency bands. The American rules for using radio frequency identification differ from those in Europe. RFID tags in the USA can use frequencies between 902 and 915 MHz. This permits companies to use different frequencies for different purposes. The European regulations are stricter. Specific frequencies are reserved for mobile communications or medical services. Second generation RFID transponders can be read at frequency bands between 860 and 960 MHz which allow them to be used almost anywhere in the world. The readers have to therefore be built to use the corresponding band for the country they are intended to be used in and this, of course would increase manufacturing costs. The ideal solution would be a worldwide uniform RFID frequency band.

A number of organizations are involved in developing standards and guidelines for using RFID in Europe. Three of which are, the European Commission, (ec.europa.eu) the European Conference of Postal and Telecommunications Administrations (CEPT) (www.cept.org) and the European Telecommunications Standards Institute (ETSI) (www.etsi.org) RFID users and technology developers are currently working with ETSI to make the frequency that the transponder standard EPC Class 1/Gen. 2 currently uses, the industry / country standard. Basically there are four frequency bands that can be used: Low, High, Ultra High and Microwave frequency.

These different frequencies have specific advantages and disadvantages. Companies deploy them for tagging palettes, transport packaging or single products according to their features. In logistics and warehousing, METRO Group relies on ultra-high frequency bands (865 - 868 MHz). The advantage of these tags is that they can be read from a distance of up to several meters. The new, more efficient EPC Class1/Gen. 2 chip standard, the so-called, second generation transponder along with further advances in the interface technology have led to a marked improvement in both readability and speed. Physical interference problems with liquids and metals have been significantly reduced. Both frequencies have difficulties to operate in the presence of large amounts of metals, as these can either reflect or absorb the radio waves.

The trading company needs a special systems infrastructure to orchestrate the interactions between RFID tags, readers and the local infrastructure.

The software entitled RFID middleware works on the principle of an adaptor. RFID middleware communicates with readers and applications using different interfaces and processes the information so that it can be read by the end-device. If we get back to our initial example: if a palette which has been sent by a supplier is accepted into the warehouse, RFID middleware takes over three main tasks. Firstly: it pools data. It receives the information which was recorded by the readers at the goods entry of the warehouse and derives a list of goods, which were delivered with the palette. Secondly: in many cases goods entry is equipped with sensors, which notify when a palette is delivered or picked up. Then the middleware also activates or deactivates the reader. This is particularly important in Europe, because it is prohibited to keep readers activated around the clock. The RFID middleware takes on a monitoring role. Thirdly: the software is a kind of a entry gate to the information and stock management system of the trading company on the one hand and to the external EPC network on the other.

The Object Naming Service (ONS) is a kind of directory. It allocates the Electronic Product Code (EPC) with a so-called, Uniform Resource Locator (URL) which identifies it in a databank and enables access to further information about the product, box or palette from this databank.

The EPC Information Services (EPCIS) computer system sends the product description to the end-device, which initiated the enquiry. The system uses a specific language: the Physical Markup Language [bitte mit dem nächsten Absatz verlinken]. EPCIS supports users in a range of questions such as: Is an Electronic Product Code referring to a product, box or palette? Which path has the tagged palette taken? What are the palette dimensions? Was the specified temperature exceeded? If yes, at which point in the supply chain?

The Physical Markup Language (PML) is a language which was developed by the Auto-ID Center and describes products. Humans and computers alike “understand“ this language. The PLM creates a uniform, standardized vocabulary to display and send information about tagged products, boxes and palettes. This information is needed by trading companies for their warehouse management and for tracing merchandise. Companies can only draw on the advantages of RFID with this interaction between software and hardware.