Performance comparison of pilot tone aided and pilot symbol aided QAM over a mobile radio channel

This paper compares the performance of pilot tone aided (PTA) and pilot symbol aided (PSA) BPSK, QPSK, 8QAM, 16QAM, 32QAM and 64QAM over a narrowband radio channel. This set of modems is capable of achieving 14, 28, 48, 56, 70 and 84 kbit/s respectively in a 20 kHz channel bandwidth. Computer simulations in a Rayleigh fading channel show that PTA modems have almost the same performance as PSA modems. However PTA signals have a higher peak to mean power ratio (η) and this translates into greater amplifier linearity requirements in the transmitter. In the PSA modems, η is independent of the pilot symbols, however in the PTA modems it depends upon the pilot tone to data power ratio (R). An optimisation of R in an AWGN channel gives a value of 0.2 for QAM. A comparison of η between PSA and PTA transmitted signals show differences of 3.38, 5.1, 4.8, 4.25, 4.45 and 3.9 dB for 99.9% of the time (based on the above mentioned list of modulation schemes)