Siemens sets wireless speed record with OFDM

IDG News Service |  Mobile & Wireless

German electronics manufacturer Siemens AG has set what it claims to be the fastest-ever wireless connection.

At its research lab in Munich, Siemens achieved a transmission speed of 1G bps (bit per second) by combining an intelligent antenna system with OFDM (Orthogonal Frequency Division Multiplexing) technology, the company said Tuesday.

By comparison, most wireless LAN systems today offer speeds of around 50M bps.

With transmission capacities for voice, data and video expected to grow by a factor of 10 by 2015, future mobile communication systems will need to utilize frequency bands as efficiently as possible, according to Siemens.

New OFDM technology, based on FDM technology, offers high-spectrum efficiency, the company said.

FDM technology transmits multiple signals simultaneously over a single transmission path, such as a cable or wireless system. Each signal travels within its own frequency range, called a carrier, which is modulated by the data in the form of voice, video or text.

OFDM's spread spectrum technique distributes the data over a large number of carriers spaced apart at precise frequencies. The spacing provides the orthogonal effect in this technique that prevents the demodulators from seeing frequencies other than their own.

For its test, Siemens used intelligent antenna systems, often called multiple antenna or multiple input, multiple output (MIMO) systems. The multiple antennas simultaneously transmit different flows of data over one and the same radio channel and frequency band.

The effect is comparable to a room in which multiple clusters of people are simultaneously conducting conversations both within each cluster and between clusters -- but without interfering with each other.

One of the reasons why multiple-antenna systems are not typically used today is the high computing power required at the receiving end. Information that is transmitted simultaneously by multiple antennas is received by multiple receiving antennas and has to be reconstructed in real-time for the receiving device.

Because this process exceeds the capabilities of chips used in most wireless devices today, Siemens researchers developed new algorithms that can be efficiently implemented on available hardware.

The benefits of OFDM are high spectral efficiency, resiliency to radio frequency interference and lower multi-path distortion, according to Siemens.

OFDM, sometimes called multi-carrier or discrete multi-tone modulation, is the modulation technique used for digital TV in Europe, Japan and Australia. It also forms the basis for ADSL (asymmetrical digital subscriber line) technology.

The Siemens experimental OFDM system operates in the 5GHz band and has a bandwidth of 100MHz.

The German company collaborated with the Heinrich Hertz Institute and the Institute for Applied Radio System Technology.

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