An Uplink Control Channel Design with Complementary Sequences for Unlicensed Bands

TL;DR

This paper introduces two novel modulation schemes based on complementary sequences for uplink control channels in unlicensed bands, effectively reducing PAPR and supporting flexible resource allocations without increasing error rates.

Contribution

The paper proposes new CS-based modulation schemes that address high PAPR issues and establish a theoretical link between CSs and Reed-Muller codes for practical system applications.

Findings

Reduced PAPR to 3 dB in non-contiguous allocations

Supports up to 21 UCI bits per user

Maintains low error rates with proposed schemes

Abstract

In this paper, two modulation schemes based on complementary sequences (CSs) are proposed for uplink control channels in unlicensed bands. These schemes address high peak-to-average-power ratio (PAPR) under non-contiguous resource allocation in the frequency domain and reduce the maximum PAPR to 3 dB. The first scheme allows the users to transmit a small amount of uplink control information (UCI) such as acknowledgment signals and does not introduce a trade-off between PAPR and co-channel interference (CCI). The second scheme, which enables up to 21 UCI bits for a single user or 11 UCI bits for three users in an interlace, is based on a new theorem introduced in this paper. This theorem leads distinct CSs compatible with a wide variety of resource allocations while capturing the inherent relationship between CSs and Reed-Muller (RM) codes, which makes CSs more useful for practical systems. The numerical results show that the proposed schemes maintain the low-PAPR benefits without increasing the error rate for non-contiguous resource allocations in the frequency domain.