Tracking down one of the last few parking spots in the cramped confines of a dimly lit multi-storey car park is not among life鈥檚 pleasures. German car maker BMW thinks it has the answer: an indoor positioning system (IPS) that guides drivers to that precious parking spot and later helps them find their car again 鈥� through smart use of the car鈥檚 anti-roll inertial sensors and a mapping app on a cellphone.
BMW鈥檚 was one of many ideas unveiled at last week鈥檚 (IPIN) conference in Zurich, Switzerland, a gathering of engineers hoping to mimic the runaway success of satnav technology 鈥� but this time indoors.
Advertisement
IPS proponents want to pepper public buildings with wireless transmitters to help people locate their departure gate at an airport, say, or a particular store in a vast mall, or an exhibit in a labyrinthine museum. IPS will also be able to track moving targets, letting us locate friends in a multi-storey building regardless of what floor they are on.
But the technology could be a while coming to a public building near you because there is no broad agreement on which technology is best for pinpointing people and objects deep within buildings. The different radio-reflecting and absorbing materials in the built environment mean that radio waves, commonly used in outdoor positioning systems like GPS and the European Union鈥檚 upcoming Galileo network, cannot reliably negotiate complex architectural geometries.
Time and strength
Consequently, engineers are trialling a variety of different methods to find the most reliable. Two leading contenders are called received signal strength (RSS) and time of arrival (ToA).
RSS relies on knowing the strength of a radio signal at its source and monitoring the drop-off with distance. Given a number of static transmitters, the receiver can work out where it is by triangulation. RSS techniques can use Wi-Fi, Bluetooth and ZigBee 鈥� an ultra-low-power version of Bluetooth 鈥� radio networks.
ToA, on the other hand, involves reading time stamps beamed from transmitters in known positions and calculating a position by comparing the times when signals from different transmitters arrive. It is the method at work in GPS.
Rivals play tag
At the trade show in London last week, of the Nokia Research Lab in Tampere, Finland, and his colleagues wore slim, credit-card-sized radio tags to track their movements to within 30聽centimetres using an RSS approach. An upgrade of Nokia鈥檚 technology, presented by Belloni鈥檚 colleagues at IPIN, also included an inertial sensor, allowing dead reckoning of the user鈥檚 motion in between accurate IPS fixes.
A rival system is being offered by , a geolocation firm based near Cambridge, UK, which presented the technology to investors at the invention show in Cambridge this month. Omnisense uses ZigBee radio, inertial sensors and a GPS receiver in its RSS tags 鈥� allowing them to switch seamlessly between indoors and outdoor locations, says the firm鈥檚 Andy Thurman.
The technology could help track miners both above ground and underground, people suffering from dementia 鈥� and cattle. Working out when a cow is ovulating is important to farmers 鈥� and they 鈥減resent鈥� in a different direction to bulls in the herd when this happens. 鈥淭he inertial sensors will tell us this,鈥� Thurman says.
GPS emulator
One of the most interesting ideas at IPIN was a ToA approach that mimics the format of the GPS signal 鈥� and which is locked to the GPS atomic clock to boot 鈥� allowing the satnav receiver technology to be used indoors as well as out. Developed by of Canberra, Australia, the system places radio nodes that beam out GPS timing data around an area or building of interest. It鈥檚 designed to aid the military if GPS is being jammed 鈥� indeed, the US air force bought one of the systems this week. Chief executive Nunzio Gambale is investigating a range of consumer applications as well.
But these varied systems leave the standardisation problem unsolved. The , a global cellphone industry body, is looking into how the next generation of 3G technology 鈥� currently called LTE, for Long Term Evolution 鈥� might be harnessed to provide a standard positioning protocol. But Kanwar Chopra, an engineer with in Cambridge, UK, is sceptical.
鈥淚 don鈥檛 think there is ever going to be one particular technology for indoor location sensing,鈥� he told the UK National Microelectronics Institute鈥檚 in London last week. 鈥淎s we go deeper and deeper indoors, accelerometers and gyros have to do the work. Radio signals are just not designed for location sensing in all environments. It鈥檚 always going to be a fusion of multiple signal types.鈥�
Read previous Innovation columns: TV networks to become social networks, CERN collides with a patent reality, Sunrise boulevards could bring clean power, Hand-held controls move out of sight, Mobile malware develops a money bug, Reinventing urban wind power, Mastering the art of 3D film-making,A real live Grand Prix in your living room, Google may know your desires before you do, Shrewd search engines know what you want, The tech refresher Russia鈥檚 spies needed, Smarter books aim to win back the kids.
