Delay Alignment Modulation: Enabling Equalization-Free Single-Carrier Communication

TL;DR

This paper introduces delay alignment modulation (DAM), a new broadband transmission technique that enables equalization-free single-carrier communication by aligning multi-path signals to eliminate inter-symbol interference, improving efficiency and reducing complexity.

Contribution

The paper presents a novel DAM scheme that achieves ISI-free transmission without equalization, applicable to MISO systems and enhanced with beamforming techniques, outperforming OFDM in certain scenarios.

Findings

DAM effectively eliminates ISI in sparse channels.

DAM reduces PAPR and out-of-band emissions compared to OFDM.

DAM improves spectral efficiency by eliminating guard intervals.

Abstract

This paper proposes a novel broadband transmission technology, termed delay alignment modulation (DAM), which enables the low-complexity equalization-free single-carrier communication, yet without suffering from inter-symbol interference (ISI). The key idea of DAM is to deliberately introduce appropriate delays for information-bearing symbols at the transmitter side, so that after propagating over the time-dispersive channel, all multi-path signal components will arrive at the receiver simultaneously and constructively. We first show that by applying DAM for the basic multiple-input single-output (MISO) communication system, an ISI-free additive white Gaussian noise (AWGN) system can be obtained with the simple zero-forcing (ZF) beamforming. Furthermore, the more general DAM scheme is studied with the ISI-maximal-ratio transmission (MRT) and the ISI-minimum mean-square error (MMSE) beamforming. Simulation results are provided to show that when the channel is sparse and/or the antenna dimension is large, DAM not only resolves the notorious practical issues suffered by orthogonal frequency-division multiplexing (OFDM) such as high peak-to-average-power ratio (PAPR), severe out-of-band (OOB) emission, and vulnerability to carrier frequency offset (CFO), with low complexity, but also achieves higher spectral efficiency due to the saving of guard interval overhead.