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Multi-user multiple input and multiple output (MU-MIMO) is one of the key techniques in 3GPP Long-Term Evolution (LTE), which enhances the overall system capacity in the downlink. In order to reduce the effect of inter-user-interference in this system, it is necessary to utilize an efficient detection method at the user equipment (UE) that besides its feasibility at high data rate transmission systems...
Algebraic decoding algorithms are commonly applied for the decoding of Reed-Solomon codes. Their main advantages are low computational complexity and predictable decoding capabilities. Many algorithms can be extended for correction of both errors and erasures. This enables the decoder to exploit binary quantized reliability information obtained from the transmission channel: Received symbols with...
Adaptive bit-loading algorithms can improve the performance of OFDM systems significantly. The tradeoff between the algorithms performance (optimum solution) and the computational complexity is essential for implementation of loading algorithms. In this paper, we present a low complexity non-iterative discrete bit-loading algorithm to maximize the data rate subject to specified target BER and uniform...
In this work, a reduced complexity wideband linear SIC multi-user detector that is suitable for large-dimension wireless/wired systems in which the multi-access interference is varying rapidly (i.e. current long-code CDMA systems) is introduced. The proposed scheme exhibits low computational complexity and can converge to either the decorrelator or the LMMSE detectors. It uses a set of weighting factors...
This work proposes an adaptive frequency-domain equalizer (FDE) for single carrier and OFDM indoor over Gbps data rate wireless receiver. System simulation and specifications are based on the IEEE 802.15.3c standard. The proposed LS-LMS FDE uses low computational complexity Least-Mean-Square (LMS) algorithm with Least-Square (LS) channel estimation to accelerate the convergence speed. The FDE can...
In this paper, a new detection method which combines the semi-definite programming relaxation (SDR) with the sphere decoding (SD) is proposed for 256-QAM multiple-input multiple-output (MIMO) system. In this method, the SDR algorithms are engaged to obtain a primary result. Then, a hyper-sphere is constructed which is centered at the received signal and has its radius equals to the Euclidean distance...
Nonorthogonal Frequency Division Multiplexing (NOFDM) is a digital modulation technique that promises to provide extremely high spectral efficiencies. However, this modulation scheme is seldom used in practice due to the high computational complexity involved in decoding the received signal in the presence of noise. The basic aim of this paper is to reduce this decoding complexity. Here, we propose...
In this paper, we propose a fast and accurate ICI cancellation with feedback correction algorithm against phase noise and frequency offset for LTE-advanced uplink system. The purpose of this paper is to describe a method to effectively compensate for ICI. In this paper, we use a fast ICI compensation algorithm, feedback correction algorithm in order to compensate ICI with adaptive channel estimation...
Since Multiple Input Multiple Output (MIMO) transmission has become more and more popular for current and future mobile communication systems, MIMO detection is a big issue. Linear detection algorithms are less complex and well understood but their BER performance is limited. ML detectors achieve the optimum result but have exponential computational complexity. Hence, iterative tree-search algorithms...
Turbo codes are proposed in most of the advanced digital communication standards, such as 3GPP-LTE. However, due to its computational complexity, the turbo decoder is one of the most power hungry blocks in digital baseband. To alleviate this issue, one way is to avoid surplus computing phases thanks to the early termination of the iterative decoding process. The use of stopping criteria is one of...
This paper proposes a lattice-reduction aided detection (LRAD) based successive interference cancellation (SIC). The proposed detector achieves as good as or better BER performances than the conventional LR aided MMSE detector and using the SIC for QPSK, 16QAM and 64QAM in the 8×8 MIMO systems. It also achieves BER curves to be as steep as or steeper than those using the maximum likelihood detector.
Decision feedback equalizers are used in wireless and mobile communications to reduce the intersymbol interference that is caused by the time dispersive channel. Here, an adaptive decision feedback equalizer is presented with a new adaptive algorithm. The algorithm uses sign normalized block based least mean square algorithm, and achieves a significant reduction of computational complexity. The proposed...
A bit loading algorithm is presented for orthogonal frequency division multiplexing (OFDM) systems to minimize bit error rate (BER), where quadrature amplitude modulation (QAM) is employed. The target data bits are loaded onto selected subcarriers that have largest remaining signal-to-noise ratio (SNRrem) values on a group-by-group basis. The number of iterations is determined by the maximum size...
The upper bound of error rate performance of coded free space optical (FSO) communication system is studied in this paper. A new tightened upper bound over fully interleaved turbulence channel is proposed based on Gallager's second-bounding techniques. Two turbulence models are considered, log-normal model for weak fluctuation scenarios and negative exponential model for strong fluctuation scenarios...
Recently, a frequency-domain block signal detection (FDBD) using maximum likelihood detection (MLD) employing QR decomposition and M-algorithm (QRM-MLD) was proposed for the reception of the single-carrier (SC) signals transmitted over a frequency-selective fading channel. SC-FDBD with QRM-MLD can significantly improve the bit error rate (BER) performance of SC transmission while reducing significantly...
The channel estimation algorithms are employed in 3GPP Long Term Evolution (LTE) downlink system to assist the coherent demodulation of Orthogonal Frequency Division Multiplexing (OFDM) symbols. Based on the comparison of several exiting different channel estimation algorithms, we propose a joint time-frequency two-dimensional iterative Wiener filter (IWF) channel estimation algorithm for 3GPP LTE...
In this paper, we consider high-rate low-density parity-check (LDPC) codes for magnetic recording systems. We propose an efficient approach to reduce the computational complexity of the sum-product algorithm (SPA) for LDPC decoding by restricting the check operation to a small subset of input messages. Furthermore, the first-order MacLaurin Series is used to simplify the core operation and an attenuation...
In this paper, we propose a modified maximum likelihood (ML) decision for a relay-based cooperative communication system using complex field network coding (CFNC). Since the traditional uncoded relay network which is wirelessly connected by inband within the donor cell causes interference during simultaneous transmissions through the intermediate relay, each signal in traditional uncoded relay network...
One proven solution to improve the reliability of a wireless channel is to use relays. We focus on the estimate-and-forward (EF) relay protocol where the relay node estimates the source symbol and then forwards it to the destination. We assume the soft information sent by the relay is the expected value of the symbol transmitted by the source. With bit-error-rate (BER) as a metric, we show that EF...
In the scalable video coding extension of the H.264/AVC standard, an exhaustive search technique is used to select the best coding mode for each macroblock. This technique achieves the highest possible coding efficiency, but it demands a higher video encoding computational complexity which constrains its use in many practical applications. This paper proposes combined fast sub-pixel motion estimation...
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