Constant Envelope Phase Modulation Inspired by Orthogonal Waveforms

Abstract

Constant envelope orthogonal frequency division multiplexing (CE-OFDM) is a technique to modify the OFDM signal with high peak-to-average power ratio (PAPR) to a constant envelope zero decibel PAPR waveform. The conventional CE-OFDM uses inverse discrete Fourier transform to calculate the signal time samples before feeding them to the phase modulator. This letter describes a different approach for the implementation of a constant envelope of generating phase digitally modulated waveforms that may be easier for implementation. The new approach, which we termed "constant envelope M-ary time orthogonal" (CE-MTO), is based on orthogonal waveforms in the time domain. A time domain-analytical study of the CE-MTO in the presence of an additive white Gaussian noise is presented. Simulations of the CE-MTO performances show the comparable results to those of the CE-OFDM technique also in a frequency selective channel.

Constant Envelope Modulation Techniques for Limited Power Millimeter Wave Links

“…Further analysis considers the detection of orthogonal modulation techniques (CE-OFDM [25] and CE-MTO [26] techniques). In the receiver (see Figure 3), after an analog to digital conversion, the samples, [ ] r n , are sent to the phase demodulator.…”

“…Due to the fact that ι(t) and n(t) are independent random processes, that is, σ 2 I+N = σ 2 I + σ 2 N , where the AWGN standard deviation is based on the following [26]:…”

“…The signal to interference power ratio is assumed to be SIR = 15 dB. The "Analytical AWGN only" curve refers to the analytical expression obtained in our previous work [26] in Equation (21) for the case of the AWGN channel only. The "Analytical Interference only" and the "Analytical Interference and AWGN" curves refer to Equations (15) and (18), respectively.…”

“…The popular orthogonal frequency division multiplexing (OFDM) signaling, which is commonly used in communications, presents envelope fluctuations, resulting in a high PAPR [24].Several CE techniques have been suggested. In the literature [25,26], the information-bearing message signal is transformed into a constant envelope waveform by the utilization of the phase modulation. In the CE-OFDM discussed in the literature [25], the OFDM waveform is used to phase modulate the carrier, while in our proposed CE-M-ary time orthogonal (CE-MTO) technique described in [26], orthogonal waveforms in the time domain were used.…”

“…In the literature [25,26], the information-bearing message signal is transformed into a constant envelope waveform by the utilization of the phase modulation. In the CE-OFDM discussed in the literature [25], the OFDM waveform is used to phase modulate the carrier, while in our proposed CE-M-ary time orthogonal (CE-MTO) technique described in [26], orthogonal waveforms in the time domain were used. In our previous work [26], we showed that the implementation of the CE-MTO technique is expected to be simpler than that of the CE-OFDM, and that the symbol error rate (SER) performances in the presence of additive white gaussian noise (AWGN) and fading channels are comparable for both techniques.Interference is a significant challenge of wireless communications that has a detrimental effect on the overall link performances.…”