In this film, Wireless in the world 2, simple visualisations of radio ‘spaces’ are overlaid into urban spaces. The film has been made as a follow up to this video experiment and has been specifically designed for exhibition in HABITAR at LABoral Centro de Arte y Creación Industrial.

Here is an excerpt from the exhibition description:

“Utopian and radical architects in the 1960s predicted that cities in the future would not only be made of brick and mortar, but also defined by bits and flows of information. The urban dweller would become a nomad who inhabits a space in constant flux, mutating in real time. Their vision has taken on new meaning in an age when information networks rule over many of the city’s functions, and define our experiences as much as the physical infrastructures, while mobile technologies transform our sense of time and of space.”

There are photos of the exhibition by Edgar Gonzalez here. The exhibition catalogue with essays by Anne Galloway, Usman Haque, Nicolas Nova and others is available to download here.

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This video is about exploring the spatial qualities of RFID, visualised through an RFID probe, long exposure photography and animation. It features Timo Arnall of the Touch project and Jack Schulze of BERG.

The problem and opportunity of invisibility

RFID is still badly understood as an interactive technology. Many aspects of RFID interaction are fundamentally invisible; as users we experience two objects communicating through the ‘magic’ of radio waves. This invisibility is also key to the controversial aspects of RFID technology; once RFID antennas are hidden inside products or in environments, they can be invoked or initiated without explicit knowledge or permission. (See here for more on the invisibility of radio.)

But invisibility also offers opportunities: the lack of touch is an enormous usability and efficiency leap for many systems we interact with everyday (hence the success of Oyster, Suica and Octopus cards). But there is also the ‘magic’ of nearness one of the most compelling experiential aspects of RFID.

As designers we took this invisibility as a challenge. We needed to know more about the way that RFID technology inhabits space so that we could better understand the kinds of interactions that can be built with it and the ways it can be used effectively and playfully inside physical products.

The experiments

In order to study the readable volume around an RFID reader, we built experimental probes that would flash an LED light when they successfully read an RFID tag. The readable volume is not the same as the radio field, instead it shows the space within the field in which an RFID tag and an RFID reader will interact with each other.

One version of our probe containing a tag and LED light connected to the RFID reader that is being studied.

In a dark room, the probes were moved around the various RFID tags and readers that we wanted to study, with a camera taking long-exposure photographs of the resulting patterns of light. In this way we could build up layers by slicing through the field in different ways, creating animations that clearly reveal the spatial properties of this interaction.

These experiments were carried out in order to help us flesh out our own models of the technology, and were not intended to be scientifically accurate. So although they accurately reflect the behaviour of the technologies in the situations that we work with, there were no controlled environments or settings for generalisable technical accuracy.

Innovations ID 20

The Innovations ID 20 RFID reader has become one of the standard components in a lot of our work, it is small, robust and relatively cheap. So it has been very important for us to gain an understanding of the readable volume it produces when we embed the reader inside products such as Sniff and Skål.

Details: Innovations ID20 low-frequency EM4102 reader, 20mm circular EM4102 tag.

The resulting visualisation shows the way in which we have mapped the boundary of the readable volume, although a tag will read anywhere inside this, we have only mapped the edge for the sake of clarity. From the animation (see the video) we start to clearly see that the readable volume is made up of a strong central sphere, accompanied by a smaller lobe that surrounds the edge of the reader.

Oyster card

Mifare cards are one of the largest public applications of RFID, used in many transit systems around the world such as the Oyster and Suica cards. It has become common to have to touch in and touch out of subway stations, and many people have become accustomed to this interaction. So what does the readable volume around an Oyster card look like?

Details: Standard Mifare Oyster card, probed with a Sonmicro high-frequency reader.

With a square antenna inside the Oyster and the Sonmicro reader, we get an elongated main volume, accompanied by long skinny lobes on each edge of the card. This looks very different from the ID 20 mapping.

Orientation

The first two mappings held the reader and the tag parallel to each other, but we predicted that there would be a higher degree of complexity in the relationship if the tag and the reader moved in different orientations. The rig below was built so that we could control the angle between the reader and the tag, which moved along the surface of the table.

Details: Innovations ID20 low-frequency EM4102 reader, 50mm circular EM4102 tag.

There is clearly enormous physical complexity in this relationship, in the animation we can see the volume growing and shrinking, lobes turning into spheres, and vice-versa. But the animation gives us a very clear picture of the ‘throw’ of the reader onto a single two-dimensional plane, almost like looking at it as a torch.

Parallel and perpendicular

To show the two extremes of the relationship between orientation and the readable volume, we created two mappings, one with the tag parallel to the reader, and the other with the tag perpendicular. We mapped them using two different colours of LED: green for parallel and red for perpendicular.

Details: Innovations ID20 low-frequency EM4102 reader, 20mm circular EM4102 tag.

This image is a composite of the two mappings (see the video for animations of the two mappings separately) and it is clear that the readable volume is significantly different. When the tag is perpendicular to the reader, there is a sizeable gap in the middle of the reader where the tag will not read, creating two readable volumes side by side.

Conclusions

We have been continually challenging the ways in which RFID technology has been framed. It is incredible how often RFID is seen as a long-range ‘detector’ or how little relevant information is contained in technical data-sheets. When this information is the primary material that we are working with as designers, this is highly problematic. By doing these kind of experiments we can re-frame the technology according to our experience of it, and generate our own material knowledge.

One of the early motivations in this project was the way in which the animations really captured our tacit, embodied knowledge of the readable volume in a visual way, it was almost as if you could wave your hand through the floating green LEDs and feel them. Of course we had felt it hundreds of times in experimenting with tags and readers, but we had never seen it captured in an image, in a way that was communicable to others without having them try an interactive demonstrator. With this visual material, we can communicate about RFID in ways that we couldn’t previously.

So we hope that this work goes some way towards building better spatial and gestural models of RFID, as material for designers to build better products and to take full advantage of the various ways in which spatial proximity can be used. And with this better understanding we hope to be able to discuss and design for privacy and the ‘leakage’ of data in a more rigorous way.

Field icon

Download a PDF file of the RFID icon.

This RFID icon is based on the shape of the ‘readable volume’. Created by Timo Arnall & Jack Schulze, it is licensed for use under a Creative Commons Attribution 3.0 Unported License.

Go ahead and use it!

Credits

The project was made by Timo Arnall and Einar Sneve Martinussen from AHO and Jack Schulze from BERG. Thanks to Jørn Knutsen for help in building the rigs.

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I’m investigating the visualisation of electromagnetic fields, part of our exploratory process to look at the materiality of RFID. What are we talking about when we say ‘touch-based interaction’ or ‘near field’ for instance? This investigation threw up an interesting company: Indexsar specialises in:

“Turnkey test systems for the measurement of SAR (Specific Absorption Rate) and the Over The Air (OTE) testing of wireless devices. Our product range includes E-field probes for use in both air and in tissue-simulant liquids, equipment for accurate testing of the dielectric properties of phantom liquids and a system to give a 3-Dimensional presentation of mobile handset radiation and sensitivity. We can supply suitable RF amplifiers and directional couplers for wireless product testing and can offer suitable phantoms (heads, hands and liquids) for testing radiated emissions.”

Their test setup includes 6-axis industrial robots to move sensors around models of human anatomy (or “phantom geometry” in official testing language). Their setups include geometry for the head, and the right hand (no left hands yet). In the test rig below a liquid model moves while the sensors are stationary. It looks like it has been hacked together from meccano and a Wacom pad.

These are some visualisations of bodily electromagnetic fields from Flomerics MicroStripes and Hugo:

Microstripes software is a 3D electromagnetic simulation & synthesis tool:

“MicroStripes is widely used to design antenna and microwave structures and assess their installed performance, to optimize RFID systems, to analyze radar cross-section (RCS), EMI/EMP and lightning effects on vehicles, ships and aircraft, and to predict absorption of EM fields in human tissue.”

Another visualisation:

Leafing through the manual for my Nokia E60 I noticed that it includes guidelines on holding the phone, in order not to degrade the performance, and thus battery life of the antennae.

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