The Wideband Radio Communications Laboratory
Radio communications are prevalent for audio, in cellular and cordless phones, and for data, in wireless data communication networks.
Future data networks are expected in wide bandwidths, that enable fast communications.
The Wideband Radio Laboratory is designed to investigate the physical aspects of radio communications, namely the radio channel connecting a transmitting antenna with a receiving antenna.
The lab is designed to gather large sets of channel response data, for statistical analysis of indoor and outdoor environments.
The Wideband Radio Communications Laboratory is located in room 3 of the Ross Building (floor -2) in the Givat Ram campus of the Hebrew University of Jerusalem.
It is supervised by Dr. Dana Porrat of the Hebrew University.
Graduate and undergraduate students are very welcome.
The lab is designed to measure the responses of wideband (2-18 GHz) indoor and outdoor radio channels.
The environment we use is the Ross building, an office building with open space areas, outdoor measurements will be taken in the future.
The pictures show the basic setup of the lab, that contains a network analyzer, two antennas, amplifiers and a positioner with millimeter resolution for positioning one of the antennas.
We can locate the antennas up to 50 meters apart.
Here are the same pictures again, with annotations:
Here are sample results, from line of sight measurements. The horizontal axis is time in nano-seconds, the vertical shows the channel's impulse response in a linear scale, and the four graphs show the responses at different receiver antenna locations, measured from the edge of the positioning table.
Note how the response is delayed as the receive antenna is moved away from the transmit antenna.
A simple calculation shows that a distance of 5 cm delays incoming waves by 5 cm / 3e8 m/s = 0.17 nsec, and 20 cm cause a delay of 0.67 nsec.
The delays between the different responses here are shorter (increase by 0.41 nsec as the distance grows by 20 cm), because movement of the receive antenna on the positioner was not radial with respect to the transmit antenna.
Movement of 20 on the positioner caused the receive antenna to move away from the transmit antenna by 0.41 nsec x 3e8 m/s = 12.3 cm.
This picture shows a larger measurement, taken with receiver locations along one meter with a resolution of 6 mm.
The arrangement of the antennas is Non Line of Sight (NLOS) with a single wall and some furniture blocking the line of sight.
The antennas are placed about 6 meters from each other.
The picture shows the impulse response at each receiver location at a different row, the horizontal axis is delay from the time of transmission of the pulse.
Red and yellow indicate a positive response (such as the peaks in the picture above), and blue indicates a negative response.
The background bluish color indicates low amplitudes.
Diagonal lines in this pictures are related to a shift in the time of arrival of a path between the transmitter and receiver, as the receiver is moved.
At delays below 35 nsec, the picture is dominated by a set of parallel lines with a negative slope (the delay decreases as receiver location increases).
Around delay 30-40 nsec appears a new set of diagonal lines with positive slopes, but these lines are weaker than the earlier ones.
This is a zoom into the range 40 - 60 nsec, with a color scale that shows the response clearly.
Modified Spetember 18, 2007, Jerusalem