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Multiuser Detection (MUD) and Channel Estimation techniques in Space-Division Multiple Access aided Orthogonal Frequency Division Multiplexing (SDMA-OFDM) systems recently received intensive interest in receiver design technologies. The maximum likelihood (ML) MUD that provides optimal performance has the cost of a dramatically increased computational complexity. The minimum mean-squared error (MMSE)...
Analog-to-digital (A/D) conversion plays a crucial role when it comes to the design of energy-efficient and fast signal processing systems. As its complexity grows exponentially with the number of output bits, significant savings are possible when resorting to a minimum resolution of a single bit. However, then the nonlinear effect which is introduced by the A/D converter results in a pronounced performance...
Besides the determined construction of polar codes in BEC channels, different construction techniques have been proposed for AWGN channels. The current state-of-the-art algorithm starts with a design-SNR (or an operating SNR) and then processing is carried out to approximate each individual bit channel. However, as found in this paper, for fading channels, an operating SNR can not be directly used...
The orthogonal frequency division multiplexing (OFDM) system requires precise channel estimation for better system performance. Among various channel estimation methods, the discrete Fourier transform (DFT)-based channel estimation is favored because it has simple architecture and shows as good performance as the linear minimum mean square error (LMMSE) estimation method. However, the DFT itself has...
In this paper, we propose a novel method for channel estimation based on adaptive pilot spacing using low complexity with least-square (LS) channel estimation. Many channel estimation method uses LS or MMSE (Minimum Mean Square Error) channel estimator. The MMSE channel estimation technique suffers from a high computational complexity with an order of O(N - P3) operations ((N - P) represents the total...
The multiuser switched diversity (MUSwiD) selection scheme is useful in reducing the required amount of channel estimations and system complexity in wireless networks. In this paper, we propose and evaluate the performance of cognitive amplify-and-forward (AF) MUSwiD relay networks where a cognitive user is selected among a set of users for data reception. The selection process is performed such that...
The channel estimation algorithm which has excellent performance is necessary for Single Carrier Frequency Division Multiple Access (SC-FDMA) system. The traditional Least Square (LS) algorithm and Linear Minimum Mean-Square (LMMSE) algorithm exist many problems. The problem of the LMMSE algorithm which is too complex is found to be applied effectively by researching LMMSE algorithm. The traditional...
In this paper, we derive closed-form capacity expressions for a low complexity bit-interleaved coded modulation system with uniform inputs in a Rayleigh fading channel with additive white Gaussian noise. Additionally, we include pilot-symbol assisted channel estimation in our considerations. Finding a closed-form solution is enabled by assuming quantization and that the decoder has no channel state...
In this paper the equalization problem is treated as a classification task. No specific (linear or nonlinear) model is required for the channel or for the interference and the noise. Training is achieved via a supervised learning scheme. Adopting Mahalanobis distance as an appropriate distance metric, decisions are made on the basis of minimum distance path. The proposed equalizer operates on a sequence...
In this paper, we investigate the performance of the low-complexity algorithms based on Likelihood Ascent Search (LAS) and Tabu Search (TS) for detection in MIMO systems with channel estimation errors. Here, we briefly review the algorithms for LAS and TS and their variants and subsequently compare them for various MIMO settings. We provide the simulation results for BER performance in 2× 2, 4× 4...
This paper presents an intact scheme of timing synchronization for Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) Ultra Wide Band (UWB) systems. Frame detection and coarse timing are implemented with the Maximum Correlation (MC) method based on the first-band information of the preamble. Fine timing is achieved with the Minimum Energy Ratio (MER) method based on the information of...
In this paper, we consider a full duplexing (FD) wireless cellular network where a central base station (BS) works in the FD mode while the downlink (DL) and uplink (UL) users work in the time division duplexing (TDD) mode. Since this FD system induces the inter-user interference from UL user to DL user, the main challenge for maximizing the system performances is user pairing that makes a pair of...
Cluster-sparse channels often exist in frequency-selective fading broadband communication systems. The main reason is received scattered waveform exhibits cluster structure which is caused by a few reflectors near the receiver. Conventional sparse channel estimation methods have been proposed for general sparse channel model which without considering the potential cluster-sparse structure information...
Sparse code multiple access (SCMA) is a new frequency domain non-orthogonal multiple-access technique which can enable massive connectivity and grant-free transmission in wireless radio access. With SCMA, different incoming data streams are directly mapped to codewords of different multi-dimensional cookbooks, where each codeword represents a spread transmission layer. Multiple SCMA layers share the...
The radio over fiber (RoF) distributed antenna system (DAS) has been chosen as one of the candidate technologies for next generation communication system. In RoF, the radio remote unit (RRU) utilizes orthogonal frequency division multiplexing (OFDM) transmission, because of its increased data rate and its resilience to multipath fading. Also in optical fiber system, the optical components cannot be...
This paper describes the performance of singular value decomposition (SVD) estimation techniques for multiband orthogonal frequency-division multiplexing (OFDM) of ultra-wideband (UWB) system in Saleh-Valenzuela channel modelling. The performance of SVD estimation is compared against LS and MMSE methods corresponding to zero-padded of a UWB system. The crucial limitation in UWB system is strictly...
In the Multiple Input Multiple Output (MIMO) systems, the receiver performance is greatly affected by Antenna Gain Imbalance (AGI). This paper proposes an novel AGI detection algorithm based on the Least Square (LS) channel estimation. The AGI parameter is accurately obtained after eliminating the influence of noise from the channel through the long-term statistics. Moreover, a compensation algorithm...
Orthogonal Frequency Division Multiplexing (OFDM) has been considered as a strong candidate for next generation high speed aerial vehicle communication systems. However, OFDM systems suffers severe performance degradation due to inter-carrier interference (ICI) in high mobility channel, if no ICI cancellation is performed. Traditionally, training symbols have been employed in one packet to help the...
Low-complexity single-stage frequency domain equalization is demonstrated in a 112-Gbps PDM-QPSK optical communication system. The bulk of CD is blindly estimated while residual CD, PMD and SOP tracking is supported by training-aided channel estimation.
In this paper, we propose a low-rank minimum mean-square error (OLR-MMSE) channel estimator for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. We evaluate the performance of the proposed low-rank channel estimator for slowly fading channel environments in terms of the symbol error rate (SER) by computer simulations. It is shown that the proposed channel...
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