MIMO-OFDMA Subcarrier Mapping Improvement by using Quarter ICI-SC with STFBC Technique

Many wireless communication systems rely on Orthogonal Frequency Division Multiple Access (OFDMA) to guarantee reliable transmission and better performance. However, the orthogonality of the subcarriers has been destroyed by frequency offset (FO) and thus leads to intercarrier interference (ICI) which reduces the system performance. In order to overcome this problem, quarter ICI self-cancellation (ICI-SC) subcarrier mapping scheme using data allocation in space-time-frequency block codes (STFBC) for MIMO-OFDMA system is proposed. The technique is then evaluated through Pairwise Error Probability (PEP) and Bit Error Rate (BER) performance. From the results, proposed quarter ICI-SC subcarrier mapping scheme technique with STFBC shows the best result for MIMO-OFDMA system

Pedestrians effects on indoor MIMO-OFDM channel capacity

Temporal variations caused by pedestrian movement can significantly affect the channel capacity of indoor MIMOOFDM wireless systems. This paper compares systematic measurements of MIMO-OFDM channel capacity in presence of pedestrians with predicted MIMO-OFDM channel capacity values using geometric optics-based ray tracing techniques. Capacity results are presented for a single room environment using 5.2 GHz with 2x2, 3x3 and 4x4 arrays as well as a 2.45 GHz narrowband 8x8 MIMO array. The analysis shows an increase of up to 2 b/s/Hz on instant channel capacity with up to 3 pedestrians. There is an increase of up to 1 b/s/Hz in the average capacity of the 4x4 MIMO-OFDM channel when the number of pedestrians goes from 1 to 3. Additionally, an increment of up to 2.5 b/s/Hz in MIMO-OFDM channel capacity was measured for a 4x4 array compared to a 2x2 array in presence of pedestrians. Channel capacity values derived from this analysis are important in terms of understanding the limitations and possibilities for MIMO-OFDM systems in indoor populated environments

New Full-Diversity Space-Time-Frequency Block Codes with Simplified Decoders for MIMO-OFDM Systems

Multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) is known as a promising solution for wideband wireless communications. This is why it has been considered as a powerful candidate for IEEE 802.11n standard. 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, at first we propose new full-diversity STFBCs with high coding gain in time-varying channels; the construct method for this structure is using orthogonal space-time block code for any arbitrary number of transmit antenna and then we propose a decoder with linear complexity for our proposed coding scheme. Simulation results verify that the proposed STFBCs outperform other recently published STFBCs

A Multi-Antenna Design Scheme based on Hadamard Matrices for Wireless Communications.

YesA quasi-orthogonal space time block coding (QO-STBC) scheme that exploits Hadamard matrix properties is studied and evaluated. At first, an analytical solution is derived as an extension of some earlier proposed QO-STBC scheme based on Hadamard matrices, called diagonalized Hadamard space-time block coding (DHSBTC). It explores the ability of Hadamard matrices that can translate into amplitude gains for a multi-antenna system, such as the QO-STBC system, to eliminate some off-diagonal (interference) terms that limit the system performance towards full diversity. This property is used in diagonalizing the decoding matrix of the QOSTBC system without such interfering elements. Results obtained quite agree with the analytical solution and also reflect the full diversity advantage of the proposed QO-STBC system design scheme. Secondly, the study is extended over an interference-free QO-STBC multi-antenna scheme, which does not include the interfering terms in the decoding matrix. Then, following the Hadamard matrix property advantages, the gain obtained (for example, in 4x1 QO-STBC scheme) in this study showed 4-times louder amplitude (gain) than the interference-free QOSTBC and much louder than earlier DHSTBC for which the new approach is compared with

Towards a Seamless Future Generation Network for High Speed Wireless Communications

YesThe MIMO technology towards achieving future generation broadband networks design criteria is presented. Typical next generation scenarios are investigated. The MIMO technology is integrated with the OFDM technology for effective space, time and frequency diversity exploitations for high speed outdoor environment. Two different OFDM design kernels (fast Fourier transform (FFT) and wavelet packet transform (WPT)) are used at the baseband for OFDM system travelling at terrestrial high speed for 800MHz and 2.6GHz operating frequencies. Results show that the wavelet kernel for designing OFDM systems can withstand doubly selective channel fading for mobiles speeds up to 280Km/hr at the expense of the traditional OFDM design kernel, the fast Fourier transform

CIR Performace of One-third ICI-SC Subcarrier Mapping Technique with STFBC in MIMO-OFDMA System

In multiple input multiple output (MIMO) with orthogonal frequency division multiple access (OFDMA) system, intercarrier interference (ICI) is one of the major drawback in the system. This is due to the orthogonality of the subcarrier which has been destroyed by frequency offset (FO) and thus degrades the system performance. In order to overcome this problem, one-third intercarrier interference selfcancellation (ICI-SC) subcarrier mapping method with space time frequency block codes (STFBC) is proposed. Average power desired (APD) signal, ICI and carrier to interference ratio (CIR) are derived theoretically and the proposed signal is analyzed with other previous methods. As a result, it is proven that by choosing the suitable subcarrier mapping with ICI-SC method, MIMO-OFDMA system performance which affected by FO can be improved with maximum diversity order

Efficient space-frequency block coded pilot-aided channel estimation method for multiple-input-multiple-output orthogonal frequency division multiplexing systems over mobile frequency-selective fading channels

© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.An iterative pilot-aided channel estimation technique for space-frequency block coded (SFBC) multiple-input multiple-output orthogonal frequency division multiplexing systems is proposed. Traditionally, when channel estimation techniques are utilised, the SFBC information signals are decoded one block at a time. In the proposed algorithm, multiple blocks of SFBC information signals are decoded simultaneously. The proposed channel estimation method can thus significantly reduce the amount of time required to decode information signals compared to similar channel estimation methods proposed in the literature. The proposed method is based on the maximum likelihood approach that offers linearity and simplicity of implementation. An expression for the pairwise error probability (PEP) is derived based on the estimated channel. The derived PEP is then used to determine the optimal power allocation for the pilot sequence. The performance of the proposed algorithm is demonstrated in high frequency selective channels, for different number of pilot symbols, using different modulation schemes. The algorithm is also tested under different levels of Doppler shift and for different number of transmit and receive antennas. The results show that the proposed scheme minimises the error margin between slow and high speed receivers compared to similar channel estimation methods in the literature.Peer reviewe