RFID and interference
RFID is a proven and effective technology, however occasionally there can be difficulties when using it alongside other wireless systems. Before installing a system it is important to consider other technologies being used within the same building or site.
An RFID specialist will take account of this and design the system in such a way as to avoid interference. If you already have an RFID system installed and you are experiencing problems, a specialist will troubleshoot your system and identify the possible causes of interference.
The two types of problems
RFID relies on wireless transmission of signals between readers and tags so interference can prevent the system from working effectively. There are two ways it can cause difficulties – firstly, one system can block the signal from another and prevent correct data being transmitted and/or received; and secondly, the signal from one system can be picked up by the other and interpreted incorrectly as valid data.
Before discussing the causes, it is worth distinguishing between the two types of RFID systems as different issues may arise with each. In passive RFID systems, the readers emit a signal that induces a current in the tag and powers its transmitter to respond. In active RFID systems, the tags broadcast their presence continuously without being prompted to do so.
. . . and the most common causes
Here are some of the most frequent causes of RFID interference problems:
- Environmental factors are the most common cause. In the past there were difficulties with tags mounted on metal or on containers of liquids, which interfered with the activation of the tags and resulted in them failing to respond to readers. Improvements in tag and antenna design and tuning have allowed these problems to be overcome provided they are considered at the planning stage.
- UHF systems can suffer interference due to reflection or re-radiation of power signals. These make careful site planning and antenna or reader tuning essential. Passive or semi-passive systems create less risk of interference than active ones.
- Cross interference is most likely to occur is between RFID systems and WIFI or personal area networks (WPAN) such as Bluetooth but only when devices share common or adjacent frequency bands. In the medical field, interference between a wireless microphone and a wireless endoscope has been noted but there are limited occurrences and the US Food and Drug Administration Centre for Devices & Radiological Health has approved RFID for use in both clinical procedures and as an aid to patient identification.
- Active tags that use IEE802.11 WIFI standards could experience difficulty when used alongside WIFI networks operating to the same standards. Whilst in laboratory conditions it has been shown that electro-magnetic radiation from RFID can cause interference with other systems. These tests also acknowledge that other technologies with similar EM signatures are already in common use.
- Standards and correct systems design help to reduce the risks – for example the Gen 2 standard for UHF systems incorporates a Dense Reader Mode which reduces the risks of interference between readers when 50 or more are deployed in close proximity. Interference problems for passive tag systems are further reduced in Europe because European standards limit the power used in such systems to 2 watts, compared with 2.4W in the USA.
The table below shows the areas of potential risk of interference between network and RFID frequency:
|Frequency||BandwidthRFID Usage||WLAN & WPAN Usage|
|58KHz – 1KHz||EAS Electro magnetic Tags|
|125 – 135KHz||LF Passive Tags|
|7.4KHz – 8.8MHz||EAS Swept-rf Tags|
|13.56MHz||HF Passive Tags|
|868MHz – 928MHz||UHF Passive Tags||IEEE802.15 WPAN (Zigbee @ 868 & 915MHz)|
|902MHz / 111.5KHz2.4GHz / 111.5KHz||EAS Re-radiating Tags|
|2.4GHz||Some WiFI based active Tags||IEEE802.11b & g WLAN IEEE802.15 WPAN (Bluetooth & Zigbee)|
(“EAS” refers to Electronic Article Surveillance, a low cost technique mainly used to prevent item theft in retail environments)
Checklist: 6 ways to avoid RFID interference
Correct installation will avoid potential interference issues. A company with specific RFID expertise will take account of the individual circumstances and requirements of each installation. In any RFID deployment, we recommend a six-step approach to minimise the risk of interference:
- Audit the frequency spectrums used by devices within the same environment.
- Clarify with suppliers the frequencies, protocols and standards used by the equipment.
- For 2.4GHz active tag systems review IP addresses and WIFI channels used in relation to the planned system.
- Carry out a pilot installation that measures the performance of the system in the planned environment.
- If necessary consider dual trials, in the planned environment and where less RF interference is expected.
- Review the performance of BOTH the RFID component and the existing systems following the pilot.
Call in the experts
CoreRFID regularly provides consultancy for companies which have issues with RFID interference. We can assess your system, identify the cause of the problems and provide recommendations on the most cost-effective solutions. Contact us to speak to one of our experienced team. Call +44 (0) 845 071 0985 or email info (at) corerfid.com ot complete the contact form.