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In this letter, we derive a low-complexity channel estimation scheme for multiple-input multiple-output multiband orthogonal frequency division multiplexing ultrawideband (MIMO MB-OFDM UWB) system over spatially correlated channel. More precisely, we drive a linear minimum mean-squared-error (LMMSE) channel estimation algorithm. Then, an optimal low-rank LMMSE channel estimation method based on low-rank...
It is well known that, in the case of frequency domain blind channel estimation, the channel gains are correctly estimated but the channel phases are not necessarily estimated correctly: the channel estimates are often accompanied with phase ambiguity because the phase range for numerical calculation is restricted to (−π, π]. In this paper, a new frequency-domain blind channel estimation without phase...
In high mobility environments, the significant Doppler shift introduces severe inter-carrier interference (ICI) to an orthogonal frequency-division multiplexing (OFDM) system, which makes channel estimation very challenging. In this paper, we propose an efficient structured distributed compressive sensing (SDCS) based joint channel estimation scheme within multiple OFDM symbols. By utilizing the complex...
In this paper, two receive beamforming techniques with carrier frequency offset (CFOs) compensation (joint receive beamforming technique and spatially-separated receive beamforming technique) are proposed for a mobile relay station with a uniform linear array in OFDM systems. The spatially-separated receive beamforming technique is shown to be robust against CFO errors and can be effectively used...
In this paper, we propose an optimal pilot design scheme for multi-user Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing/Space Division Multiple Access (OFDM/SDMA) systems. We derive the optimal pilot design criterion with regard to the computational complexity and the Mean Square Error (MSE) of the Least Square (LS) estimator. Furthermore, we propose a binary-tree...
This paper explores the potential benefit of recently proposed spectrally-efficient frequency-division multiplexing systems (SEFDM), when compared to traditional orthogonal frequency-division multiplexing (OFDM) systems. First, the considered SEFDM channel model is described, then we obtain an expression for the capacity of this channel in case of un-precoded transmission. We evaluate the channel...
En este artículo se encuentra un OFDM óptimo para redes eléctricas inteligentes. El OFDM óptimo consiste de constelaciones bidimensionales rotadas rectangular, circular y hexagonal de cuatro y dieciséis. Los resultados que se obtienen logran disminuir la probabilidad de error de bit en forma significativa por un orden de magnitud de por lo menos 1×10−2 cuando se compara con OFDM-QAM
In this paper, a novel DFT-based pilot-symbol-aided channel estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems is presented. By using transform domain cluster and discriminant analysis, this algorithm can adaptively remove the noise in the channel impulse response (CIR). Then as the noise is removed, the accuracy of channel estimation can be improved dramatically. With...
A large-scale MIMO multi-cell system is considered where the desired cell bears pilot contamination. Multiple neighbor cells and the desired cell use the same pilot position to transmit training symbols, and training symbols from neighbor cells have a large received power. The channel estimation of the desired cell will be significantly deteriorated. In order to reduce the impact of pilot contamination...
A unipolar orthogonal frequency division multi-plexing (OFDM) technique called flipped OFDM (Flip-OFDM), is suitable for intensity modulation and direct detection (IM/DD) channel which needs the transmitted signal to be real and positive. Flip-OFDM uses two consecutive OFDM subframes to transmit the positive and negative parts of the signal, respectively. In the conventional receiver, only the difference...
In the context of long-haul multi-band coherent OFDM transmission (at 400 Gbps), we propose an inter-band nonlinear interference canceler based on Volterra series. This new type of receiver significantly improves the BER performance compared to the standard third-order inverse Volterra series nonlinear equalizer.
We find optimized M-QAM constellations for short-reach DDO-OFDM using an iterative gradient-search method and evaluate their performance. With the optimized constellations, capacity is increased by 12 Gb/s compared to square constellation achieving data rate of 168 Gb/s for 16-QAM.
Orthogonal frequency division multiplexing (OFDM) modulations are very popular in wireless communications due to their flexibility and good performance over severely time-dispersive channels. However, OFDM signals have large peak-to-average power ratio (PAPR), which leads to amplification problems. Constant envelope OFDM (CE-OFDM) techniques use an OFDM signal to modulate the phase of a given carrier,...
In this paper, we critically compare the performances of bulk, per-subcarrier and combined selection schemes in super dense networks. Specifically, their outage and contention probabilities are critically appraised. To analyze the effects of outage and contention together, a performance parameter termed the bulk gain factor is defined and employed. Finally, we find that although the bulk selection...
Reaching a consensus in a group decision-making (GDM) usually costs plenty of time and resources, so how to minimize the total cost in a GDM process has become the focus of most researchers, which makes the construction of the minimum cost consensus models be the key research field in recent years. The aim of this paper is to propose two kinds of non-linear minimum cost consensus models: one considers...
A novel rateless coded Vector Orthogonal Frequency Division Multiplexing (V-OFDM) system for adaptive transmission over wireless channels is studied in this paper. In particular, an iterative receiver with joint V-OFDM equalization and ratelss decoding is designed, which exchanges the logarithmic likelihood information between the belief propagation decoder and the maximum likelihood equalizer or...
In this paper, we analyze the effect of the imperfect channel estimation on the equalization performance in three-node cooperative wireless networks. Specifically, we consider a distributed time-reversal space-time block coded single-carrier (D-TR-STBC-SC) system over frequency-selective fading channels with amplify-and-forward (AF) half-duplex relaying. Through the comprehensive analysis of mean-square-error...
In this paper, we propose Irregular Non-Binary Low Density Parity Check (IR-NB-LDPC) codes with Signed Log Fast Fourier Transform (SL-FFT) decoding algorithm to overcome the harsh environment of power-line communication (PLC) channels. Their performance is compared with Irregular Binary LDPC (IR-B-LDPC) codes using the Sum Product algorithm (SPA). The sparse parity check matrix H of both codes are...
This paper considers the network energy efficiency in multi-cell OFDMA downlink systems. We propose a resource allocation scheme with limited coordination to optimize the network energy efficiency and satisfy user requirement. The proposed scheme has two steps; centralized and distributed. In the first step a central unit allocates the resources for cell- edge users at first place giving them high...
This paper examines the challenging carrier frequency offset (CFO) estimation problem in the tile-based orthogonal frequency division multiple access (OFDMA) uplink systems. The existing solutions to this problem are either restricted to less flexible subcarrier assignments or too complex to implement in practice. This paper proposes simple iterative solutions with extremely low computational load,...
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