Single Input Single Output (SISO) Orthogonal Frequency Division Multiplexing (OFDM) systems have been adopted in many of the recent wireless communication standards such as European terrestrial broadcast systems based on DVB-H, DVB-T and DVB-T2. For OFDM systems, cyclic prefix of sufficient length makes the receiver design simple in frequency-selective multipath environments. Wireless communication based on Multiple Input Multiple Output (MIMO) systems has gained popularity due to the potential capacity increases it can provide. MIMO-OFDM based transmission systems can thus provide very high data rates with a relatively simple receiver design and are now adopted widely in recent wireless communication standards such as Long Term Evolution (LTE), WiMAX and WiFi. Modern wireless communication applications, both SISO and MIMO, require high data rates at high carrier frequencies and at high levels of mobility. This results in less intercarrier spacing and severe time-varying frequency-selective multipath fading, which breaks the orthogonality of subcarriers and causes intercarrier interference (ICI) in the received signal thus severely impacting the BER performance of the receiver. Hence, efficient receiver design which is fundamental to any communication system is ever more relevant. Turbo iterative receivers (IR) are based on the observation that performance of the system can be significantly improved if detection and decoding are combined together. They, in general, are found to have superior performance compared to other solutions, however turbo IRs usually suffer from high computational complexity which makes their implementation expensive. Such practical application challenges motivate us to propose a new, low complexity, Turbo IR for SISO and MIMO OFDM systems under time varying frequency selective channel conditions. Motivated by the classical TE, we first propose a sub-optimal, successive interference cancellation and MAP decoding (SIC-MAP) algorithm for SISO systems. In SIC-MAP, copies of the received signal on the same and adjacent subcarriers are carefully combined to take advantage of the frequency diversity (on account of the time variations of the channel) while eliminating the interference from the other transmit symbols leveraging the feedback information from the decoder. The resulting system matrix becomes a single column vector which allows an easy MAP decoding. BER performance, computation complexity, and convergence behavior of the proposed scheme has been contrasted with two other similar schemes. It has been found that SIC-MAP, while having near identical performance to the competing schemes, can be implemented approximately with only a third of their computational complexity. Subsequently, we extend the above detection idea, SIC-MAP, to MIMO systems (SIC-MAP-MIMO). Unlike single antenna systems, even under static multipath channel conditions, the received signal in a MIMO receiver is corrupted by the co-antenna interference (CAI), thus making the detection task more challenging. SIC-MAP-MIMO algorithm achieves comparable BER performance to the competing equalization schemes but with even more computational savings than SISO. A low complexity Least Squares (LS) based iterative channel estimation scheme using soft feedback information has also been proposed. This scheme is especially suitable when the number of significant channel taps is higher than the number of pilots, a phenomenon that is often encountered in practical systems.
Subject (authority = RUETD)
Topic
Electrical and Computer Engineering
Subject (authority = ETD-LCSH)
Topic
MIMO systems
Subject (authority = ETD-LCSH)
Topic
Wireless communication systems
RelatedItem (type = host)
TitleInfo
Title
Rutgers University Electronic Theses and Dissertations
Rutgers University. Graduate School - New Brunswick
AssociatedObject
Type
License
Name
Author Agreement License
Detail
I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.