Two New Families of Low-Correlation Interleaved QAM Sequences

Abstract

Two families of low correlation QAM sequences are presented here. In a CDMA setting, these sequences have the ability to transport a large amount of data as well as enable variable-rate signaling on the reverse link.

The first family ${\cal I}^2{\cal SQ - B}$ is constructed by interleaving 2 selected QAM sequences. This family is defined over M ²-QAM, where M = 2^m, m ≥ 2. Over 16-QAM, the normalized maximum correlation $\overline{\theta}_{\max}$ is bounded above by $\lesssim 1.17 \, \sqrt{N}$, where N is the period of the sequences in the family. This upper bound on $\overline{\theta}_{\max}$ is the lowest among all known sequence families over 16-QAM.

The second family ${\cal I}^4{\cal SQ}$ is constructed by interleaving 4 selected QAM sequences. This family is defined over M ²-QAM, where M = 2^m, m ≥ 3, i.e., 64-QAM and beyond. The $\overline{\theta}_{\max}$ for sequences in this family over 64-QAM is upper bounded by $\lesssim 1.60 \, \sqrt{N}$. For large M, $\overline{\theta}_{\max} \lesssim 1.64 \, \sqrt{N}$. These upper bounds on $\overline{\theta}_{\max}$ are the lowest among all known sequence families over M ²-QAM, M = 2^m, m ≥ 3.