S.B. Makarov - Dr.Sc. (Eng.), Professor, Director, St.Petersburg State Polytechnic University, Institute of Physics, Nanotechnology and Telecommunications E-mail: makarov@cee.spbstu.ru S.V. Zavyalov - Post-graduate, Department «Radio engineering for securing information», St.Petersburg State Polytechnic University, Institute of Physics, Nanotechnology and Telecommunications E-mail: sz5@mail.ru

Specific costs of frequency bandwidth and specific energy costs for using non-orthogonal multi-frequency signals were examined for different coherent detection algorithms, including coherent detection algorithm with compensation for inter-channel interference. The energy spectrum of a random sequence of multi-frequency PSK-4 signals with an arbitrary frequency spacing between subcarriers Δf and arbitrary envelope of the form a(t) is the sum of shifted copies of the spectral density`s average power of single-frequency signal (if quadrature components are formed independently). The dependences of peak-factor of a random sequence of signals on the number of subcarrier frequencies are presented. The value of the peak-factor of signal sequence is decreased with reducing frequency spacing between subcarriers and tends to the value of 3 dB, which is defined as the value of peak-factor of the sum of signals on a single carrier frequency. Elementwise coherent detection algorithm with compensation for inter-channel interference has been developed and studied. BER performance of non-orthogonal multi-frequency PSK-4 signals for this algorithm is considered. Inter-channel interference has maximum effect on BER performance of signals which are located at the center frequency (by simulation results). Application of the detection algorithm with compensation for inter-channel interference significantly improve the validity of data receiving non-orthogonal multi-frequency PSK-4 signals. In area of BER p = 10-3?10-4 energy gain is equal to 10 dB. The threshold effect appears when the detection algorithm with compensation for inter-channel interference is used in the low signal-to-noise ratio due to the presence of a feedback loop. This effect is linked to the clustering of wrong decisions of symbols. As a result the efficiency of application algorithm with compensation for inter-channel interference must be smaller than efficiency of application classic elementwise coherent detection algorithm. This is confirmed by simulation. Specific costs of frequency bandwidth are reduced with using non-orthogonal multi-frequency signals with rectangular shape of envelope by more than 12% with energy loss less than 1 dB in area of p = 10-3?10-4 comparatively to orthogonal multi-frequency transmission system. Further reduction in specific costs of frequency bandwidth can be accomplished by usage of signals with a smooth shape of envelope.

 

1. Fink L.M. Teorija peredachi diskretnykh soobshhenijj. Izd. 2-e pererab. i dop. M.: Sov. radio. 1970.
2. Makarov S.B, Cikin I.A. Peredacha diskretnykh soobshhenijj po radiokanalam s ogranichennojj polosojj propuskanija. M.: Radio i svjaz. 1988.
3. Makarov S.B., Rashich A.V. Snizhenie pik-faktora signalov s ortogonalnym chastotnym uplotneniem // Nauchno-tekhnicheskie vedomosti SPbGPU № 2(55)/2008. SPb.: Izd-vo SPGU. 2008. S. 79-84.
4. Makarov S.B., Rashich A.V. Metod formirovanija spektralno-ehffektivnykh OFDM-signalov na osnove neortogonalnykh bazisnykh funkcijj // Nauchno-tekhnicheskie vedomosti SPbGPU № 2(76)/2009. SPb.: Izd-vo SPGU. 2009. S. 94-98.
5. Feer K. Besprovodnaja cifrovaja svjaz. Metody moduljacii i rasshirenija spektra: Per. s angl. / Pod red. V.I. ZHu­ravleva. M.: Radio i svjaz. 2000. 520 s.
6. Makarov S.B. Markov A.M. Priem v «celom» sluchajjnykh posledovatelnostejj chastotno-manipulirovannykh signalov s mezhsimvolnojj interferenciejj // Radiotekhnika. 2011. № 3. S. 46-51.
7. Makarov S.B., Ulanov A.M., Cikin I.A. EHffektivnost primenenija ogranichennykh po spektru zavisimykh signalov pri peredache diskretnykh soobshhenijj // EHlektrosvjaz. 1988. № 5.