This invention relates to Bluetooth communications and in particular to extending the range of Bluetooth communications.
Bluetooth is a low power radio protocol which is used to transfer data in the 2.4 GHz ISM (Industrial Scientific and Medical) band. Whilst Bluetooth is widely used and is very versatile, Bluetooth enabled devices tend to have limited range and where there is intervening structure or equipment between two communicating Bluetooth devices (Bluetooth peers) range can become restricted to the point that it is not a feasible form of communication in some circumstances. In particular, with the normal range provided by Bluetooth enabled devices it can be impossible to set up a wireless Bluetooth system to allow communication with devices spread out over a large factory or commercial premises.
There is a desire therefore for apparatus and methods which can be used to extend the range of Bluetooth communication.
In conventional radio communications repeaters are sometimes used in an effort to increase range. A radio repeater functions by detecting a weak radio signal with one antenna, reamplifyng and then transmitting the amplified signal from another antenna. However, in getting such a radio repeater to function there is a problem of ensuring that the receiver of the weak incoming radio signal does not pick up the boosted signal output from the other antenna. If this happens a positive feedback loop results. This means that no data gets transmitted and the end result is that the transmitting antenna transmits an ever increasing signal until it saturates. This phenomenon is known as self-oscillation.
The Bluetooth protocol allows a so-called piconet to be formed. A piconet is a collection of up to eight Bluetooth devices that can talk to one of their members which is defined as a master, while the other members are defined as slaves. Bluetooth also allows different piconets to connect to each other in order to share information between the piconets. When such piconets join together one device partakes in both piconets, but as a slave to the master of each. This means that information is only transferred across the piconets if that slave is interrogated and controlled by both masters. Thus, before any information can be transferred between the piconets, it is necessary for the master in the receiving piconet to interrogate the common slave to determine whether there is any information to be transferred.
It is an aim of the present invention to provide apparatus and methods for extending the range of Bluetooth communication between a master and slave device without the need for establishing advertising piconet group capabilities, coordinating Bluetooth transmitters, or scatternets.