MIMO Sistemler İçin Gelişmiş Uzaysal Modülasyon Teknikleri / Advanced Spatial Modulation Techniques for MIMO Systems

Uzaysal modulasyon (sm), geleneksel isaret kumelerine ek olarak anten indisleriyle de bilgi iletmek temeline dayanan, yakin zamanda onerilmis umut verici bir cok-girisli cok-cikisli (mimo) iletim teknigidir. Bu bilgilendirici makalenin temel amaci, telsiz iletisim alaninda calisan arastirmacilara bu guncel ve yeni konuyu tanitmak, sm konusunda yakin zamanda yapilan calismalari gozden gecirmek ve sm sistemlerinin hata basarimini iyilestirmek icin literaturde onerdigimiz iki yeni ve ozgun mimo iletisim sistemini okurlarin dikkatine sunmaktir [12-16]. Uzay-zaman blok kodlamali uzaysal modulasyon (stbc-sm) olarak adlandirilan ilk sistemde sm, uzay-zaman blok kodlama (stbc) ile birlestirilmistir. Dolayisiyla bu sistemde, bilgi simgeleri sadece uzay ve zaman bolgelerine degil ayni zaman anten bolgesine de dagitilmistir. Stbc-sm icin genel bir tasarim yontemi verilmis ve en buyuk olabilirlikli (ml) kod cozucu incelenmistir. Bilgisayar benzetimleri yardimiyla stbc-sm yapilarinin klasik sm ve v-blast yapilarina gore oldukca iyi hata basarimi sagladigi gosterilmistir. Incelenen ikinci sistemde ise, ek kodlama kazanclari elde etmek icin, sm ile kafes kodlama birlestirilerek kafes kodlamali uzaysal modulasyon (tc-sm) olarak adlandirilan bir mimo iletisim sistemi sunulmustur. Bir kafes kodlayici ile sm esleyicinin birlikte tasarlandigi bu sistemin ciftsel hata olasiligi (pep), iliskisiz rayleigh sonumlemeli kanallar icin hesaplanarak kod tasarim olcutleri verilmistir. Ardindan bu olcutler $4$, $8$ ve $16$-durumlu tc-sm sistemlerinin elde edilmesinde kullanilmistir. Bilgisayar benzetimleri sonucu incelenen tc-sm yapilarinin klasik uzay-zaman kafes kodlara gore daha dusuk kod cozmekarmasikligi ile daha iyi hata basarimlari sagladigi gosterilmistir. -------------- ABSRACT Spatial modulation (SM), which has recently been proposed andis based on the use of the antenna indices to transmit informationin addition to the conventional signal constellations, is a promising multiple-input multiple-output (MIMO) transmission technique. The main objective of this tutorial paper is to introduce theresearcher working in wireless communication the recent developments and results in the area of the SM as well as the two newand novel MIMO transmission schemes, which have been proposed in the literature quite recently, to improve the error performance of the SM system [12-16]. In the i¬rst scheme called spacetime block coded spatial modulation (STBC-SM), SM is combinedwith space-time block coding (STBC). Therefore, in this scheme,information symbols are expanded not only to the space and timedomains but also to the antenna domain. A general design technique is given and maximum likelihood (ML) decoder is investigated for STBC-SM. It is shown by computer simulations that theSTBC-SM systems achieve signii¬cantly better error performancethan classical SM and V-BLAST systems. In the second reviewedscheme, to obtain additional coding gains, a new MIMO communication scheme called trellis coded spatial modulation (TC-SM)is presented by combining SM with trellis coding. For uncorrelated Rayleigh fading channels, code design criteria are given byderiving pairwise error probability (PEP) of this system, in whicha trellis encoder and SM mapper are jointly designed. These criteria are then used to obtain 4, 8 and 16-state TC-SM schemes.It is shown via computer simulations that the investigated TCSM schemes achieve better error performance than the classicalspace-time trellis codes, at reduced decoder complexity