Asynchronous and variable data rate OFDM modem for RADAR data transmission

This paper addresses the real trials of a new OFDM modem specifically designed for data RADAR transmission that was promoted by the Spanish aeronautical authorities. The nature of this environment is very different of standard applications and has required some new features that will be described in the sequel. The data source is asynchronous depending on the appearance of new plots, and therefore the data rate is also variable. Frames transmission must be very short, less than one second because it is a critical real time application. It is unidirectional, that means that we do not have a feedback channel to inform the transmitter about the channel state. To cope with this lack of time diversity we have implemented a parallel transmission strategy by different channels well separated in frequency. Also, FEC and CRC codes are included working with very short interleavers due to the delay requirement. This design has been tested in a real link between Madrid and Las Palmas de Gran Canaria with quite satisfactory performance using our own broadband transceiver to make the multiband transmission efficiently.