Patent ID: 8831427

Claim:
Method for the transfer of a data signal from a stationary transmitter to a mobile receiver or vice versa, said method comprising the following steps: dividing a first electrical data signal into a number N of parallel data signal streams, modulating each of said parallel data signal streams to an orthogonal electrical sub-carrier, said sub-carriers having different frequencies, converting said plurality of parallel data signal streams to an electrical second serial data signal stream, using said second serial data signal stream for modulating the intensity of an infra-red light source, receiving an optical signal of said infra-red light source by use of a receiver and converting said optical signal back to said second serial data signal stream, demodulating said number N of parallel data signal streams from said second serial data signal stream, processing each of said parallel data signal streams separately, using at least one sub-carrier as a backchannel from the receiver to the transmitter in order to transfer control information concerning the current transfer quality and data rate of each sub-carrier, adapting the amount of data sent to each of said parallel data signal streams and the modulation method of each of said orthogonal electrical sub-carriers according to the transfer quality of the respective sub-carrier wherein the in-band sub-carrier with the lowest sub-carrier frequency is regularly used as a backchannel from the receiver to the transmitter in order to transfer control information concerning the current transfer quality and the current data rate of each sub-carrier.