Siemens researchers have set a world record for mobile radio data transmission: It achieved a capacity of 1 Gbps in real time. That's about 20 times faster than today's wireless LAN, which reaches 50 Mbps, according to Siemens' researchers. The researchers succeeded in setting the record by combining a number of antennas with the special OFDM transmission system.

According to experts, data transmission rates on this scale will be needed for the transmission of videos, photographs and other multimedia data in about 10 years. In collaborating for the world record with the Fraunhofer Institute for Telecommunications and the Institute for Applied Radio System Technology (IAF), the researchers used 5 GHz as a base frequency, a range in which future commercial transmission channels are likely to operate. The bandwidth of 100 MHz was divided into closely adjacent carrier frequencies that don't interfere with one another. This so-called Orthogonal Frequency Division Multiplexing (OFDM) protects the signal as far as possible against interference such as echoes, which are caused by reflections from buildings.

The researchers also used a multiple input, multiple output (MIMO) system comprising three transmitting antennas and four receive antennas. With these multi-antenna systems, a number of antennas simultaneously transmit different datastreams via the same radio channel and frequency band. This is comparable to a room where several conversation groups have gathered — and all of the groups can talk at the same time without disturbing one another. In contrast to single antennas, each of which sends on a separate frequency, the MIMO system makes it possible to multiply the data transmission rate because it uses the frequency spectrum more efficiently. On the receiving side, multi-antenna systems require a level of computing power that exceeds the capacity of today's mobile communications chips. That's why Siemens researchers optimized the algorithms for the signal processing and implemented them on today's chips.

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