GEOHYPE: Spatial Data Focusing
Associating wireless information to physical location is an interesting feature that many applications can benefit from. This capability is known as geocasting.
GEOHYPE investigates physical solutions that enable the broadcasting of information to specific spatial locations, using limited infrastructures. From a scientific point of view, the problem is to find a way for a base station to wirelessly transmit data that are decodable only within desired areas. To overcome limitations of classical beamforming methods that necessitate large and complex antenna arrays, GEOHYPE proposes an original approach named Spatial Data Focusing. Instead of focusing the radiated power of a transmitter toward a particular direction, GEOHYPE aims to focus the data only. In other words, transmitted data are present everywhere but decodable only at the desired location.
The Concept
To enable base stations to spatially discriminate geographical areas, beamforming can be used as shown in the figure on the left. Using an antenna array, it is possible to target different spots. However, this suffers from a fundamental physical limitation: the beamwidth, hence the size of the illuminated area, is strictly related to the electrical size of the array.
So for instance, for a base station to illuminate a spot of 10 meters at a distance of 200 meters, the antenna array using a classical beamforming approach would need more than 30 elements and should be about 6 meter large at a GSM operating frequency of 900 MHz. Using Spatial Data Focusing, GEOHYPE can reach this performance using only 2 antenna elements, leading to an array of typically less than 20 centimetres, as shown in the figure on the right.
The Novelty
Using Multiple Input Single Output architectures and dedicated signal processing, GEOHYPE introduces an alternative to beamforming in geocasting scenarios. It can be shown that focusing the data is spatially more selective than focusing the power.