MIMO Testbed at 2.5 GHz

The Vienna MIMO Testbed

The Vienna MIMO testbed is a custom built wireless testbed that allows for repeatable and fully controllable over-the-air experiments. Thereby, the testbed is not restricted to a certain wireless communication standard. It allows for experiments with arbitrary signals with a bandwidth of up to 20 MHz.

The major components are:

  • Three outdoor transmitters supporting up to four antennas each are located on three different rooftop locations. There, the digital signal samples are converted with a precision of 16 bits and are transmitted with adjustable power within a range of about -35 dBm to 35 dBm per antenna.

  • One indoor receiver with four channels that converts the received signals with a precision of 16 bits before the raw signal samples are saved to hard disk. The receive antennas are mounted on a positioning table, which allows for measurements at different positions within an area of about 1 m x 1 m, correspondingly 8 λ x 8 λ.

  • Accurate time and frequency synchronization of all stations is implemented by using GPS synchronized rubidium frequency standards at all stations. Thereby, a dedicated control and synchronization network is used to exchange timing and synchronization information.

Outdoor transmitter
Outdoor transmitter located on a rooftop
Indoor receiver
Setup to compare different antenna configurations

 

Setup to measure at high velocities

At the receiver side, a custom built rotary unit extends the capabilities of the Vienna MIMO testbed for fully controllable wireless measurements at user velocities of up to 400 km/h. Thereby, repeatable time-variant channels are generated by rotating the receive antennas around a central pivot. A light barrier generates a trigger every time the receive antennas pass. This allows for repeated transmissions over the same time-varying channel and therefore for a fair comparison of different transmit signals at different velocities. In order to generate different channel realizations the whole setup can be moved within an area of 3 λ x 2.2 λ.

HighVelocities
Custom built rotary unit
Measured doubly selective channel
The setup allows for repeated transmissions over the same time-variant channel
Selected publications