Now-a-days wireless networks such as cellular communication have deeply affected human lives and became an essential part of it. The demand to buy high capacity and better performance devices and cellular services has been rapidly increased. There are more than two hundred different countries and almost three billion users all over the world which are using cellular services provided by Global System for Mobile (GSM), Universal Mobile Telecommunication System (UMTS), Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX). In the past decade, one antenna is connected to only one communication radio device at the same time but currently this scenario has been completely changed. To increase the capacity of the channels and to improve the bit error performance between mobile station and service station, it is now possible to connect one antenna with more than one communication radio device at the same time. Multiple Input Multiple Output (MIMO) systems are designed to obtain this requirement. In MIMO systems, antennas are combined in the form of small frames like coupling in cellular devices. Diversity means to obtain successful transmission and reception of radio signals with accordance to polarization and correlation. Due to diversity the capacity of the channels and bit error rate are improved, so diversity is one of the main and important properties of MIMO systems. This thesis is emphasized to study WiMAX systems by implementing multiple antenna techniques, by observing the bit error rate performance and data rate in WiMAX systems using two important and currently widely applied multiple access communication techniques. The research will also elaborate these techniques and explain the basic parameters, operations, mathematical calculations and different relevant observations. The simulation tool used in this research thesis is MATLAB which is also used to illustrate the results with figures and graphs. / Nu för tiden trådlösa nätverk såsom cellulär kommunikation har stor påverkan på människors liv och blev en viktig del av det. Kravet att köpa hög kapacitet och bättre utrustning prestanda och mobiltelefoni har snabbt ökat. Det finns mer än två hundra olika länder och nästan tre miljarder användare över hela världen som använder mobiltelefoni som Global System for Mobile (GSM), Universal Mobile Telecommunication System (UMTS), Wireless Local Area Network (WLAN) och Worldwide Interoperability för Microwave Access (WiMAX). Under det senaste decenniet har en antenn ansluten till en kommunikationsradio enhet vid samma tidpunkt, men för närvarande detta scenario har fullständigt förändrats. Att öka kapaciteten av kanalerna och för att förbättra prestandan lite fel mellan mobil station och bensinstationen, är det nu möjligt att ansluta en antenn med mer än en kommunikationsradio enhet samtidigt. Multiple Input Multiple Output (MIMO) system är utformade för att uppnå detta krav. I MIMO-system, antenner kombineras i form av små ramar som kopplingsanordningar i cellulär enheter. Mångfald innebär att få lyckad överföring och mottagning av radiosignaler i enlighet med polarisation och korrelation. På grund av mångfalden kapacitet av kanalerna och bit error rate förbättras, så att mångfald är en av de största och viktigaste egenskaper MIMO-system. Denna avhandling är betonas att studera WiMAX system genom att genomföra flera antenn teknik, genom att observera bitars prestanda felfrekvensen och datahastighet i WiMAX system med hjälp av två viktiga och som för närvarande tillämpas allmänt flera tekniker tillgång kommunikation. Forskningen kommer också att utveckla dessa metoder och förklara de grundläggande parametrarna, operationer, matematiska beräkningar och olika relevanta iakttagelser. Den simuleringsverktyg som används i denna forskning avhandling är MATLAB som också används för att illustrera resultaten med siffror och diagram.

Multiple antenna techniques are used to increase the robustness and performance of wireless networks. Multiple antenna techniques can achieve diversity and increase bandwidth efficiency when specially designed channel codes are used at the scheme’s transmitter. These channel codes can be designed in the space, time and frequency domain. These specially designed channel codes in the space and time domain are actually designed for flat fading channels and in frequency selective fading channel, their performance may be degraded. To counteract this possible performance degradation in frequency selective fading channel, two main approaches can be applied to mitigate the effect of the symbol interference due to the frequency selective fading channel. These approaches are multichannel equalisation and orthogonal frequency division multiplexing (OFDM). In this thesis, a multichannel equalisation technique and OFDM were applied to channel codes specially designed for multiple antenna systems. An optimum receiver was proposed for super-orthogonal space-time trellis codes in a multichannel equalised frequency selective environment. Although the proposed receiver had increased complexity, the diversity order is still the same as compared to the code in a flat fading channel. To take advantage of the multipath diversity possible in a frequency selective fading channel, super-orthogonal block codes were employed in an OFDM environment. A new kind of super-orthogonal block code was proposed in this thesis. Super-orthogonal space-frequency trellis-coded OFDM was proposed to take advantage of not only the possible multipath diversity but also the spatial diversity for coded OFDM schemes. Based on simulation results in this thesis, the proposed coded OFDM scheme performs better than all other coded OFDM schemes (i.e. space time trellis-coded OFDM, space-time block coded OFDM, space-frequency block coded OFDM and super-orthogonal space-time trellis-coded OFDM). A simplified channel estimation algorithm was proposed for two of the coded OFDM schemes, which form a broad-based classification of coded OFDM schemes, i.e. trelliscoded schemes and block-coded schemes. Finally in this thesis performance analysis using the Gauss Chebychev quadrature technique as a way of validating simulation results was done for super-orthogonal block coded OFDM schemes when channel state information is known and when it is estimated. The results obtained show that results obtained via simulation and analysis are asymptotic and therefore the proposed analysis technique can be use to obtain error rate values for different SNR region instead of time consuming simulation. / Thesis (PhD)--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted