A couple of common misconceptions about RFID and Wi-Fi radio channels (and RFID as Wi-Fi points)

RFID tag for patients to be seen on the hospital map

- Can you make a chip in every head for every builder?
- Theoretically, yes, but maybe explain why you need it?
“They steal building materials from us.” Right during the works. And so everyone will be seen where he went there, where not necessary.

The project was decided by sewing RFID tags into uniforms, dividing the construction into zones and beyond with what is being done on the network when building the perimeter. That is, building a profile of “white” traffic - who goes where and when. And then - like on a firewall - the builders banned everything else. Thefts were immediately reduced. The foreman received otherworldly power and saw almost every joint.
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And then every goddamn time, when I talk about the RFID solution, people start waving their hands and confusing these tags with Wi-Fi, Bluetooth and passive resonating circuits. One of the reasons - some RFID tags actually work over Wi-Fi 802.11. Let's tell how it is used in practice in different countries.

Passive and active RFID

There are two kinds of RFID tags. The first ones are those that do not have their own onboard power and simply resonate in a magnetic field. Such you most often see in shops from bookstores to clothes, and even on sausage in the grocery. They are very cheap, small and reliable, if the attacker does not have a bag woven from a wire on the principle of a Faraday cage.


Passive tags

Active RFID tags are not a resonating, but an independently radiating circuit. Signal transmission is constantly and at a much greater distance. Active tags are more expensive, more, but they can give more data. Active tags, obviously, are much easier to read - respectively, the readers themselves will be two orders of magnitude smaller and an order of magnitude less demanding on power.


Active tags

The usual drawdown distance for a passive tag is 3 meters, for an active one, 100–500 meters.

“Large” active tags, so as not to get up twice, are supplied with different sensors. The possibility of continuous monitoring and transmission of the signal to the radio air makes it possible to broadcast the level of temperature, humidity, notify of shocks and impacts, the level of vibration, show the level of illumination, gas pollution (including qualitatively, for example, only in carbon dioxide), broadcast the level of radiation. And writing logs in the internal memory - 512 kilobytes does not seem fiction anymore.

These labels are very actively used in different industries.

RFID over Wi-Fi 802.11

Now we have reached the most interesting and large RFID-tags. These are 802.11-compatible radio devices that broadcast at frequencies from 2.4 to 2.4835 GHz or 5.8 GHz to 5.825 - in those same “household” bands. And their charm is that they are "out of the box" are full-fledged parts of the Wi-Fi infrastructure and do not require any intermediate protocols or interfaces for communication.


Not all support 5GHz - for example, this 802.11 b / g / n, 2.4GHz

Patients will not go far

Label as in the picture above the post was introduced in a foreign hospital. She hit the patients on the belt. It transmits the basic telemetry without additional lotions - just the patient's position (in the case of a hospital, the closest radiator corresponding to the ward or corridor). If you press her finger on the groove, you can call your sister, if you push hard or fall face down on the floor along with the mark - the doctor will come running instead of the sister.

It is 802.11 b / g / n, the signal power is omnientenna + 11.5dBm, 2.4 - 2.4835 GHz, the protocol is UDP / IP or DHCP, 16 Mbit / s for 40 meters, 6 Mbit / s for 100 meters are stated. Open / WPA2 protection, the battery is not removed, it dies in the cold in a day or two, there is a certain class of protection against rain. The size is approximately like a cockroach from the Fifth Element, 3x5 centimeters and a little less than a centimeter in height. It weighs 2 grams (as much blood in the vole mouse). Rear clip or Velcro.

A hospital in Canada put these tags on the staff too - just see what you can do next. It turned out that with the help of such things it is possible to greatly increase the safety of performing various procedures, optimize patient flows, simplify the work of keeping a log for security, monitor all sorts of different parameters from external sensors. The best story is a nasty squeak, if you don’t wash your hands when you come from the “dirty” zone.

Final - the introduction of tags on all valuable equipment. They just started with a quick search for objects like beds, stretchers and wheelchairs, but then they realized that they could take telemetry from their instruments. And they connected to the notifications à la Zabbix all medical monitors, ventilators, etc.

Search for free riders in production

Another interesting introduction was done on the American industrial complex. To begin with, each container and each individual accounting unit (pallet or box) were supplied with a passive RFID tag in order to keep accurate records of products and know what and how is spent. This alone has somewhat reduced, as they wrote in the report, “non-production losses” - it seems that in America they steal as merrily as they did in familiar factories.

Then the tags were hung on the form of workers - this is done according to the requirements of labor safety. On the part of the tags - the function "lonely worker", when you need to move or pull the tag every 5-10 minutes. I didn’t do it - it squeaks disgustingly, and after 15 seconds SOS is sent.

Then, tracking the flow of workers and materials, production analysts began to look for problems. Found a couple of manual procedures that were absolutely not needed at the factory, automated some of the processes, unloaded the internal logistics due to the correct location of the warehouses and the correct accounting of shifts. In general, they were able to ensure that workers did not stand idle and did not wait for something, but constantly worked. At the last stage, they were going to do the integration for automatic assignment of tasks to employees in real time (at the time of implementation, this was done at the beginning of the shift).

And the final is automation of transport and materials accounting logs, quick inventories and residue control.

At school

For one American school, RFID + Wi-Fi was implemented in a very original way. Each student has a regular Wi-Fi-compatible label, and the teachers have small Wi-Fi terminals with the ability to send and receive messages.


Based on ARiSTA Flow

The school principal can send messages to teachers, and teachers can respond with recorded patterns like “understood”, “urgently approach”, etc. The same system is activated by fire alarms and other emergencies — teachers receive information about where the class should be displayed, then there is actually an evacuation route.

In each class there is a reader (Wi-Fi access point), which “sees” and counts the students. The attendance log is generated automatically. The school intranet is connected to the server, which looks into the large Internet, and parents can log in with the application or directly through the web-form and see where their children sit at school and diaries at the same time.

The most interesting thing is done in the school bus, which collects children in the district. Children with tags get on the bus, and there is almost the same functional infrastructure installed, and parents can make sure that the child has sat down normally and see the bus on the map (he gives the coordinates of his GPS sensor).

Teachers began to hang individual tags on projectors and other equipment in order to know where it is located exactly, therefore, the school still marks the school inventory.

What it looks like

One example of a solution is Cisco RFID over Wi-Fi.

The Mobility Services Engine (MSE) aggregates the signal strength data from all wireless devices and sends them to the MobileView application. MSE also provides a wealth of security features ranging from security — Cisco CleanAir, location detection to unauthorized devices, Wi-Fi intrusion prevention systems (wIPS), and location analytics.

Or MobileView is a web application for displaying tracking of asset movements, including alarm messages, based on movements across specified zones.



RFID tags with telemetry, call buttons, temperature and humidity sensors.

Here are the staff tags:



Range Outdoor range: Up to 200m (650 feet) Indoor range: Up to 80m (260 feet)
Physical and Mechanical Dimensions (incl. Flange): 80mm x 40.6mm x 20mm (3.14in x 1.60in x 0.8in) Total Weight (Incl. Retractable reel): 53g (1.86oz). Radio 802.11 b / g / n compliant (2.4 GHz) Low frequency receiver for chokepoint detection (125 kHz) Transmission power: up to + 19dBm (~ 81mW) Patented. Ultrasound Receiver Frequency: 40KHz.

Works up to 2 years without replacing the battery. Depends on the configuration in the system.
Includes an ultrasonic transmitter with a frequency of 40kHZ, these signals are distributed only within the room, which is necessary for the accuracy of the location detection system. An RFID tag via ultrasound receives a request from a special transmitter that is installed in the room, and sends a response via Wi-Fi, determining the location of the person.

Asset tags:



45mm x 31mm x 18mm (1.7in x 1.2in x 0.7in) Weight: 26g (0.92oz), Radio 802.11 compliant (2.4 GHz) Low frequency receiver for chokepoint detection (125kHz) Transmission power: up to + 19dBm (~ 81mW) Patented clear channel sensing avoids interference with wireless networks. Ultrasound Receiver (optional) Frequency 40KHz.

In this label, a 3.6V battery is installed with the possibility of replacement. Duration of work - up to 4 years. The tag sends charge information to the MobileView system. The tag is equipped with a motion sensor, and in the case of motion, it begins to send a signal to the monitoring system. The transmission interval is adjustable from 1 second to 3.5 hours. Includes an ultrasonic transmitter with a frequency of 40kHZ, these signals are distributed only within the room, which is necessary for the accuracy of the location detection system. An ultrasound RFID tag receives a request from a special transmitter that is installed in the room and sends a response via Wi-Fi, identifying the location of the asset.

Tag Setting Device:


Radio Wi-Fi 802.11 (2.4 GHz); b / g / n compliant * Bluetooth 4. 1 (2.4 GHz) * Low Frequency receiver (LF) 125kHz Transmission power: Up to + 19dBm (~ 81mW). This sensor, this device allows you to quickly configure RFID tags.

Ultrasonic LF transmitter (various options):



The ultrasonic transmitter connects to the LAN and is powered by PoE. He constantly sends a request at a frequency of 40 KHz. At this frequency, the signal propagates only within the room where the transmitter is installed. When an active RFID tag appears indoors, it receives a signal and transmits its data via Wi-Fi to the MobileView monitoring system. There are several types of LF transmitters, they differ in signal transmission distance and mounting possibilities.

Thanks to these devices, it turns out to save the charge on the active tags, because the tag can turn off and stop transmitting information via Wi-Fi when leaving the working area of ​​the LF transmitter.

In general, I hope it became a little clearer how it works. In Russia, the use of such tags is still extremely rare, but we are already preparing the first major implementations. If there are questions not for public discussion, then my mail is AChuvilin@croc.ru.