Application of Optimal Finite-Length Signals for Overcoming "Nyquist Limit"

An opportunity of finite-length optimal signals application to excess Nyquist limit without energy losses and within defined occupied bandwidth is considered in this article. Finite-length optimal signals with different duration can be found by numerical solution of corresponding multistep optimization task. Optimality criterion of signal form is based on defined reduction rate of out-of-band emissions in condition of controlled intersymbol interference. Controlled intersymbol interference determines possibility of application of simple algorithm of coherent bit-by-bit detection. Solutions of optimization tasks for different conditions are compared with known signal forms in term of Euclidean distance between signal sequences according to Mazo method. It is shown that optimal signals provide higher symbol rate without significant losses in BER performance and may be applied in 5G standards instead of signals formed with the use of digital filtration.