Over-the-Air Testing of Impulsive Frequency Shift Keying Modulation

Abstract

Code division multiple access has been used in military communications due to its low probability of detection and interception. However, with the shift towards the wideband regime due to the crowded frequency spectrum, the high cost of obtaining channel state information in this regime impedes the usage of code division multiple access. Impulsive frequency shift keying is a modulation scheme that performs well in the wideband regime without channel state information, and has potential for low probability of intercept systems due to it being based on frequency shift keying. In this work, we demonstrate the concept of impulsive frequency shift keying with over the air testing. We consider the performance of impulsive frequency shift keying in Rayleigh fading channels with both log-normal path loss and shadowing to facilitate the development of a link budget for the transmitter and receiver design. Its performance is investigated in the real world by implementing the transmitter and receiver using software-defined radios and performing over the air tests in a suburban environment by fixing the transmitter and attaching the receiver to a moving vehicle. We achieve a data rate of 0.9 kb/s, which is sufficient for text communications, and show that the symbol error rate for discretized signal-to-noise ratio bins follows a similar trend to the probability of a symbol error in the simulations.