SYNTHESIS OF SPECTRALLY AND ENERGY-EFFICIENT SIGNAL-CODE CONSTRUCTIONS FOR MIMO SYSTEMS WITH SIGNALS SPATIAL CODING

Abstract

Wireless communication systems are considered, the main task of which is to increase
their spectral (SE) and energy efficiency (EE) in conditions of limited frequency and energy resources.
Additional use of the spatial resource based on flexible and universal methods of signals Space-Time
Coding (STC) in MIMO-systems (Multiple Input - Multiple Output) can significantly increase the SE and
EE values, as well as significantly improve the capabilities and conditions for EE exchange on SE. The
advantages and disadvantages of Orthogonal Space-Time Block Coding (OSTBC) and Non-Orthogonal
STBC (NOSTBC) are shown. Two main methods of synthesis of spectrally and energy-efficient
information transmission methods are demonstrated. The first method is implemented by creating
Perfect-codes that simultaneously achieve maximum diversity and multiplexing gains. The exponential
computational decoding complexity of such codes makes it impossible for their practical implementation
in mobile terminals at the present stage of development of circuitry. The second method of synthesis is
based on improving the simple basic STC methods in terms of increasing the SE and EE by creating
Signal-Code Constructions (SCC), which have the advantages of the basic STC methods and are devoid
of the disadvantages inherent in Perfect-codes. A technique for the synthesis of SCC is proposed, the
essence of which is to determine the priority areas (by the value of the Signal-to-Noise Ratio (SNR)) of
using the STC and corresponding signal constellations, which provide the maximum SE for a guaranteed
Bit Error Rate (BER). It was found that MIMO 2x2 with Alamouti OSTBC has an advantage in terms of EE
over NOSTBC type VBLAST for SE not more than
8 b/s/Hz and SNR under 35 dB, BER not exceeding 10-5. In MIMO 4x4, OSTBC codes are inferior to
NOSTBC in terms of EE. VBLAST code allows to provide SE 4 - 8 b/s/Hz at SNR 10 - 20 dB, BER not
exceeding 10-5. Based on the results obtained, propositions for further improvement of OSTBC and
NOSTBC are formulated.