Performance Enhancement of MIMO OFDM for Higher Spectral Efficiency (original) (raw)
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Low Complexity Space-Frequency MIMO OFDM System for Double-Selective Fading Channels
This paper presents a highly robust space-frequency block coded (SFBC) multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system. The proposed system is based on applying a short block length Walsh Hadamard transform (WHT) after the SFBC encoder. The main advantage of the proposed system is that the channel frequency responses over every two adjacent subcarriers become equal. Such interesting result provides an exceptional operating conditions for SFBC-OFDM systems transmitting over time and frequencyselective fading channels. Monte Carlo simulation is used to evaluate the bit error rate (BER) performance of the proposed system using various wireless channels with different degrees of frequency selectivity and Doppler spreads. The simulation results demonstrated that the proposed scheme substantially outperforms the standard SFBC-OFDM and the space-time block coded (STBC) OFDM systems in severe time-varying frequency-selective fading channels. Mo...
International Journal of Advanced Research in Electrical, Electronics and Instrumentation Energy, 2014
In this paper, an analysis for the bit error rate (BER) performance of space-time block codes (STBC) from generalized orthogonal designs for QAM modulation has been presented. Space-time block codes (STBC) offer high diversity gain and among which orthogonal STBCs are very attractive due to its relatively simpler design and low decoding complexity. Performance of Alamouti STBC and Orthogonal STBC with rate ½ for different transmitting and receiving antennas under Rayleigh fading situation has been analyzed. The decoding techniques used for this analysis are ZF, MMSE and ML. In all the cases, the bit error rate has been treated as the figure of merit and its change with SNR are observed due to different parameter variations of the channel distribution as well as different antenna configurations.
A new approach to diversity and multiplexing gains for wideband MIMO channels
IEEE Transactions on Wireless Communications, 2007
In this paper, a new approach to improving reliability and bandwidth efficiency in communications over frequencyselective channels using multiple antennas is proposed. In the heart of the new approach is a novel space-time orthogonal frequency division multiplexing (OFDM) scheme. The proposed space-time OFDM modulator translates a multiple-input multiple-output (MIMO) channel into a single-input multipleoutput (SIMO) channel without the loss of system freedom (the available diversity gain). This translation simplifies code design as compared to that in the conventional MIMO OFDM approach. Instead of more complicated space-time codes, codes that are designed for single-input fading channels can be used with the proposed space-time modulation. For bandwidth-efficient applications, a channel multiplexing scheme is developed to work with the space-time modulator. Unlike the conventional spatial multiplexing schemes, an arbitrary number of data streams can be created and each layer occupies all the transmit antennas all the time. As a result, all the available degrees of freedom are preserved for each layer and a full range of optimal tradeoffs between data rate and reliability is possible. Several examples are given to demonstrate the advantages of the proposed approach over the conventional MIMO OFDM approach.
A New Full-Diversity Space-Time-Frequency Block Code for MIMO-OFDM System
2013
Multi-input multi-output-orthogonal frequency-division multiplexing (MIMO-OFDM) is known as a proper solution for wideband wireless communication. Numerous space-frequency block codes (SFBCs) and space-time-frequency block codes (STFBCs) have been proposed so far for implementing MIMO-OFDM systems. In this paper, a new full-diversity STFBC is proposed for two transmit antennas, which could benefit from the maximum coding advantage when delay and power profiles (DPPs) of the channel are available at the transmitter. Furthermore, simulation results confirm that the proposed STFBC outperforms other recently proposed STFBCs with the same order of the receiver complexity.
BER & SNR Performance of MIMO OFDM with Space-Time Block Coding
2018
Multi-Input and Multi output-OFDM system which is the merging of two systems, MIMO and OFDM, have more data transmission rate with huge diversity. STBC with MIMOOFDM has a better performance against the multipath interference including destructive interference which causes fading with less Bit Error rate, coding complexity and more SNR ratio. Created and analyzed a digital prototype of a physical model for estimating the performance of the MIMOOFDM system with STBC. The analysis carried out here shows that the MIMO-OFDM system along with STBC has better Signal to Noise Power Ratio with less BER than the Non-STBC MIMO-OFDM system.
Diversity and Coding Gains of Space-Time-Frequency Coded MIMO-OFDM
VTC Spring 2008 - IEEE Vehicular Technology Conference, 2008
Space-time-frequency (STF) coding for multipleinput multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) over frequency-selective Rayleigh fading channels is considered. The maximum diversity order and coding gain of the system are derived when linear constellation precoding (LCP) is applied to OFDM symbols. It is also shown that with a proper subcarrier grouping of the OFDM symbols, the system implementation can be greatly simplified while maintaining the diversity order and coding gain. In particular, as long as the group size F is not less the number of effective resolvable channel taps L, the maximum diversity order can always be achieved. Moreover, if F ≥ L, and F is an Euler number or an integer power of 2, the maximum coding gain can be achieved. Otherwise, the achievable coding gain approximates 70% of the maximum one.
Mimo Channel and Performance Analysis using OFDM System for Reduced Bit Error Rate
ABC Research Alert, 2015
Multiple-input Multiple-output (MIMO) systems use multiple antennas at the transmitter and receiver end, are a key technology to meet the growing demand for high data rate wireless systems. The aim of this thesis is to investigate MIMO system capacity with the aim of achieving optimum Bit Error Rate (BER) while increasing the system capacity using multicarrier delay diversity modulation (MDDM), proposed for fifth generation systems. In principle, the capacity of MIMO system can increase linearly with the number of antennas. Multiple antennas at the transmitter and receiver provide diversity in a fading environment. Furthermore, the research work in this thesis consists of different investigations of the basic principle of MIMO, Multiple-input Single-output (MISO) and Single-input Single-output (SISO) wireless communication systems with Space Time Codes (STC). A MISO systems and MIMO systems are schematized using MDDM which incorporated with Orthogonal Frequency Division Multiplexing (OFDM). OFDM is chosen over a single-carrier solution due to lower complexity of equalizers for high delay spread channels or high data rates. The design is implemented with binary Phase Shift Keying (BPSK) and simulated using MATLAB, which is examined in associated Additive White Gaussian Noise (AWGN) channel. The receiver-design is included with the maximal ratio combiner (MRC) receiving technique with perfect wisdom of channel state information (CSI). The theoretical performance is derived for AWGN channels and compared with the simulated results as well as compared between each system to another.
2011
To enhance the capacity of a multiple input single output (MISO) system in wireless communications, the most widely used channel coding technique is the space time block coding (STBC). The outstanding orthogonal full rate STBC proposed by Alamouti is the most successful one and also very simple to implement, where only two transmit antennas and one receive antenna are used. As the number of antennas is increased beyond two, the orthogonality of the STBC is lost. Recent literature proposes a scheme known as the quasi-orthogonal STBC for full rate communication. It has been found that for 1/2 and 3/4 rate, the orthogonality of the code can be maintained. In this paper, we propose a system with a full rate orthogonal STBC for four symbols and eight transmit antenna MISO case. After comparing the performance of the proposed system with the existing models, we have found that the proposed scheme is the best in context of the probability of bit error (BER) consideration.
Combined beamforming with space-time-frequency coding for MIMO–OFDM systems
AEU - International Journal of Electronics and Communications, 2015
Multiple antennas can be used in wireless systems to achieve good quality of service and high data rate communication. Recently, efficient space-time-frequency (STF) codes have been developed to improve the diversity gain. This paper aims at performance analysis of multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system using STF Coding and random beamforming. The proposed approach which combines beamforming with STF code offers improved performance over STF in term of bit error rates (BER). It is also observed that the proposed scheme gives better performance as compared to the combined space-time block code (STBC) with beamforming. Computational complexity of the proposed scheme is also calculated.