Correlation, spread-spectrum multiple-access and linear complexity properties of nonlinear feedforward logic (NLFFL) pseudonoise sequences

Two classes of nonlinear feedforward logic (NLFFL) pseudonoise (PN) sequences based on AND and majority logic (ML) gates are compared. Suggestions are made for sequence design. Correlation and direct-sequence (DS) spread-spectrum multiple-access (SSMA) properties of properly designed NLFFL sequences are found to be comparable with the properties of well-known linear PN sequences. It is determined that sequence design employing ML gates with an odd number of inputs is easier compared with the design with AND gates, especially when the number of gate inputs is large The severe nonbalance problem at the output of an AND or equivalent nonlinear gate can be avoided. ML-NLFFL type sequences are less vulnerable to correlation attack and jamming by the basic m-sequence. Instead, they possess smaller linear complexity values compared with AND-NLFFL sequences.<>