Generalized Step-Chirp Sequences With Flexible Bandwidth

TL;DR

This paper introduces a family of generalized step-chirp sequences with tunable bandwidth, designed for flexible beam sweeping in massive MIMO systems, and explores their autocorrelation and spectral properties.

Contribution

The paper proposes a new class of sequences with adjustable bandwidth and closed-form expression, enhancing beamforming and sweeping efficiency in MIMO systems.

Findings

Sequences have low autocorrelation sidelobes and flat spectra.

Parameters allow flexible bandwidth adjustment.

Sequences relate to Mow's perfect autocorrelation sequences.

Abstract

Sequences with low aperiodic autocorrelation sidelobes have been extensively researched in literatures. With sufficiently low integrated sidelobe level (ISL), their power spectrums are asymptotically flat over the whole frequency domain. However, for the beam sweeping in the massive multi-input multi-output (MIMO) broadcast channels, the flat spectrum should be constrained in a passband with tunable bandwidth to achieve the flexible tradeoffs between the beamforming gain and the beam sweeping time. Motivated by this application, we construct a family of sequences termed the generalized step-chirp (GSC) sequence with a closed-form expression, where some parameters can be tuned to adjust the bandwidth flexibly. In addition to the application in beam sweeping, some GSC sequences are closely connected with Mow's unified construction of sequences with perfect periodic autocorrelations, and may have a coarser phase resolution than the Mow sequence while their ISLs are comparable.