Using GPS–Enabled Technology Indoors

An increasing number of mobile phones and PDAs allow people access to the internet wherever they are and whenever they need it.

Users are using their mobile devices routinely to search the internet for the information they need, ranging from the location of the nearest cinema to aeroplane landing times and myriad other requirements that are part of their daily life.

The systems that allow this to take place could be described as “pull technology” where the initial request for data originates from the client, which is then responded to by the server. The reverse is known as push technology, where the server pushes data to clients.

An example of a service that uses a push technology is Location Based Services (LBS).

Services can be offered to users by LBS based on their geographical location provided by positioning technology such as Global Positioning System (GPS). This is usually backed up, or complemented by, a Geographical Information System (GIS) that essentially manages the provision of point-of-interest data such data petrol stations, nightclubs, shops, etc. Consumers receive information based on their geographic location.

This works perfectly well as long as the mobile device can receive a GPS signal; usually this is not an issue when outdoors with a clear view of the sky and the GPS satellites some 12,600 miles above the earth.

When moving indoors this can provide a challenge because the signals from the positioning satellites are too weak to penetrate the building materials.

What is required is an enabling technology such as a GPS repeater system.

A repeater is a device that relays GPS signals to any indoor location that isn’t normally reachable.

There is an outdoor antenna to pick up the signal, a coaxial cable to carry the signal to the interior of the building and a small mains-powered repeater unit.

The repeater re-radiates the GPS signal inside the building, nominally providing coverage within a radius of up to 20 metres in diameter.

If the required coverage are is larger than can be serviced by a single repeater, multiple units may be installed, all operating from the same outdoor antenna,

So who would benefit from this technology?

Certainly retailers who are selling GPS-enabled devices, such as satnav systems for cars would benefit from a GPS repeater. At least when potential buyers are looking at the satnav demo units on display the would see their current “live” position as opposed to a message that reports the loss of GPS signal 3 days, 16 hours, 11 minutes and 45 seconds ago.

Additionally, owners and/or operators of shopping centres can provide GPS signal within their premises so that GPS-enabled devices can acquire satellite signals without the need to leave the building; thus enabling any Location Based Service that may be in use.