In mobile communications, channel side information at transmitters can increase capacity. For moving relays nodes, local nodes placed on buses and trams in urban areas, the channel state information is outdated for control delays of several milliseconds, as in the LTE system.
Prediction of the channel based on statistic is not adequate for vehicular velocities. In this thesis, prediction made with an additional antenna, a “predictor antenna”, placed in front of the main antenna is evaluated.
The predictor utilizes that the channel of the predictor antenna is highly correlated to the channel experienced by the main antenna somewhat later, when the main antenna has moved to the position previous occupied by the predictor antenna.
A normalised correlation of up to 0.98 could be measured between the channels of the antennas for an antenna separation of several wavelengths, but it was found that the close environment and the antenna pattern have a big impact on the correlation.
The predictions made with the antenna are also combined with predictions based on statistics of past measurements from the main antenna to see if a better result can be achieved. For a prediction range of 0.5 carrier wavelengths, a prediction as good as a normalised mean square error (NMSE) of -13.9 dB could be seen.
This is sufficient to give a gain in the performance when using link adaptation and opportunistic multi-user scheduling, based on channel state information at transmitter. The evaluations is based on measurements on a 20 MHz downlink channel at 2.68 GHz.
Source: Uppsala University
Author: Wiklund, Ingrid