Two New Families of Low-Correlation Interleaved QAM Sequences

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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.