There are different standards that regulate the use of UHF RFID throughout the world. The two main regulations are: FCC and ETSI. Whilst the protocol remains the same, the frequency and technique to communicate with the tag are different. Here is a summary of the two main regulations:
|Standard Name||Primary Regions of Operation||Frequency Range||R-->T Technique||Max Radiated Power|
|FCC||FCC part 15.247 & 15.249||North America||902-928 MHz||FHSS||4W EIRP|
|ETSI||EN 302 208-2 v2.1.1||Europe||865-868 MHz||4 channel plan||2W ERP|
For more information regarding the regulations worldwide please refer to this EPC Global document. http://www.gs1.org/docs/epcglobal/UHF_Regulations.pdf and for more information about the differences between the measure of power please refer to EIRP and ERP article.
This post discusses the nuances of applications intended for deployment in ETSI regions. Within this region there are 4 transmit channels available (hence the name “four channel plan”) where the reader can transmit the maximum allowable power from the antenna (namely 2W ERP, 33dBm).
Due to having significantly less channels, less power and less bandwidth per channel than in FCC regions, applications designed for ETSI regions often have to consider channel selection.
Here are some basic best practice tips:
1. Ensure you’re using the correct channels; use all four channels if you can; but this is not always possible due to other readers transmitting in close proximity; (if using ItemTest to test your reader, select “Use Specified Frequencies” in "Frequency Settings (ETSI Only)" section and select all 4 channels, as shown below)
2. If you have more than one reader in close proximity that will be operating at the same time then alternate output channels; this can be important for times when two readers are used to create a portal or when two dock door portals are in close proximity. An example would be having reader A use channels 4 and 10 (865.7 & 866.9 MHz), and reader B using channels 7 and 13 (866.3 & 867.5 MHz) as shown in the diagrams below:
When readers are actively transmitting, if this separation of channels is not designed into the system there is a 25% chance that they will be transmitting at the same time; thereby increasing the chances if interference; and with it the chances of not reading tags.
3. Considerations if you have to use a single channel; ETSI regulations dictate that it is only permitted to transmit on a single channel for a certain period of time. 4 seconds if tags are being read and only one second if no tags are being read... if this happens then the reader must stop transmitting for a period of 100ms. The reader ensures it complies with the regulations automatically, therefore, it’s important, where possible, to ensure more than one channel is selected.
If you have more than two active readers in close proximity; careful consideration must be given to the design of the system. Which channels to use, separation of antennas, angle of antennas and how operation of the reader is triggered are all variables that can affect the operation of the RFID solution. Please also see this post to learn how to select specific channels when using ETSI readers: Selecting Specific Channels Using ETSI Regulations