A Novel PAPR Reduction Technology Of TDCS

TDCS is a low probability intercept and low probability detection communicationssystem because of its ability to utilize a noise-like time-domain communications waveformwhile simultaneously avoiding interfering signals in the RF spectrum of interest. One of itsmajor drawbacks is Peak-to-Average-Power Ratio (PAPR). A large PAPR requires a linearHigh Power Amplifier (HPA) and digital-to-analogue converters (DAC) of high dynamicrange. Which bring about expensive cost performance trade-off.This thesis investigates PAPR reduction in TDCS by using two techniques Projectiononto Convex Sets (POCS) and Gradient based algorithm using tone reservation (TR).POCS is an algorithm for controlling the clipping in multi-carrier modems, it iterativelyreduces the peak power by adding energy to unused tones in the transmitter. It uses a timedomain shaping vector generated in the frequency domain, by modifying the projection ontocomplex sets approach for multicarrier systems. Simulations show that adequate PAPRreduction is achieved, transmitter-receiver waveform mismatches are not exacerbated byPAPR reduction, and the resulting waveform is still LPI.This research also examined the theory and application of the Gradient Based Algorithmusing (TR) for PAPR reduction of TDCS. TDCS is a system that inherently possesses unusedcarrier frequencies, or null-tones, in his respective transmission frequencies. The fundamentalof TR property relies on using other unused or reserved tones to design a peak-cancellingsignal that lowers the PAPR of a transmitted signal.The investigation of PAPR reduction is done by making modifications to TDCS model. Itrevealed that a TDCS with modified spectral mask with forced null-tones provided acceptableresults when reducing PAPR with Gradient Based Algorithm. Simulations showed that bysacrificing12out of128TDCS tones (9.4%) for tone reservation, over4dB of PAPRreduction can be obtained for TDCS system.