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Abstract
The energy efficiency of pulse-amplitude-modulated discrete multitone modulation (PAM-DMT) decreases as the modulation order of M-PAM modulation increases. Enhanced PAM-DMT (ePAM-DMT) was proposed as a solution to the reduced energy efficiency of PAM-DMT. This was achieved by allowing multiple streams of PAM-DMT to be superimposed and successively demodulated at the receiver side. In order to maintain a distortion-free unipolar ePAM-DMT system, the multiple time-domain PAM-DMT streams are required to be aligned. However, aligning the antisymmetry in ePAM-DMT is complex and results in efficiency losses. In this paper, a novel simplified method to apply the superposition modulation on M-PAM modulated discrete multitone (DMT) is introduced. Contrary to ePAM-DMT, the signal generation of the proposed system, termed augmented spectral efficiency discrete multitone (ASE-DMT), occurs in the frequency domain. This results in an improved spectral and energy efficiency. The analytical bit error rate (BER) performance bound of the proposed system is derived and compared with Monte-Carlo simulations. The system performance is shown to offer significant electrical and optical energy savings compared with ePAM-DMT and DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM).
Highlights
As the demand for higher data rate broadband access increases, the limited availability of the electromagnetic spectrum becomes an ever more important challenge
Since the bit error rate (BER) performance of M-ary pulse-amplitude modulation (M-PAM) is equivalent to the BER performance M2-QAM at a given signal-to-noise ratio (SNR), the BER performance of all of the aforementioned unipolar orthogonal frequency division multiplexing (OFDM) schemes is identical
This is similar in principle to [10,11,12], the superposition is performed in the frequency domain which results in simpler system implementation compared with the time domain processing of eACO-OFDM, SEE-OFDM and Layered ACO-OFDM
Summary
As the demand for higher data rate broadband access increases, the limited availability of the electromagnetic spectrum becomes an ever more important challenge. Unipolar OFDM schemes, such as asymmetrically clipped optical OFDM (ACO-OFDM) [4]; pulse-amplitude-modulated discrete multitone (PAM-DMT) [5]; unipolar orthogonal frequency division multiplexing (UOFDM) [6]; and flip OFDM (FLIP-OFDM) [7], achieve unipolar OFDM time-domain waveforms by exploiting the frequency/time domain symmetries of the OFDM frames. An alternative method to achieve superposition modulation based on aclaco was proposed by Lawery [13] This is similar in principle to [10,11,12], the superposition is performed in the frequency domain which results in simpler system implementation compared with the time domain processing of eACO-OFDM, SEE-OFDM and Layered ACO-OFDM. A novel simplified technique is proposed to generate the superimposed PAMDMT waveforms in the frequency domain, and it is termed augmented spectral efficiency discrete multitone (ASE-DMT). In ASE-DMT, the frames alignment is arranged in the frequency domain
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