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A novel joint blind channel estimation and turbo equalization algorithm is proposed for orthogonal frequency-division multiplexing (OFDM) system in this paper. It has been proved that, blind channel estimation based on linear precoding can obtain channel information exactly. However, the precoding will cause inter-symbol interference (ISI). With the existence of ISI, the bit error rate (BER) performance...
This paper addresses mobile terminal (MT) relaying in order to improve the performance of mobile satellite broadcasting. It considers selective decode-and-forward (SDF) relaying with BICM-OFDM air interface. The BER upper bound was derived for the threshold-based SDF relaying in Rician fading channels. The suboptimal SNR threshold was then obtained by minimising this analytical upper bound. This scheme...
In this paper, we propose an iterative SIC receiver architecture with pilot- and data-based channel estimation for efficient decoding of non-orthogonal superimposed signals. The non-orthogonal superposition concept on top of OFDMA is a promising technique to improve cell spectral efficiency. In the cellular case, where users with significant path loss are superimposed by an intelligent scheduler,...
In this paper, we undertake a comparison of LDPC (768,384) and convolutional (171,133) codes for 60-GHz OFDM-based wireless communication systems. The comparison is based on two parameters: Frame Error Rate (FER) for 60-GHz channels and decoding hardware complexity for a required throughput of more than 1 Gbps. Additionally, we provide performance parameters of a fully parallel LDPC decoder chip,...
This paper investigates the transmission in time dispersive channels of Spectrally Efficient Frequency Division Multiplexed (SEFDM) signals, where carrier orthogonality is intentionally violated in order to increase bandwidth efficiency. Sufficient statistics of the transmitted SEFDM signal can be obtained by projecting the received signal onto an orthonormal base generated at the receiver using an...
Cooperative decoding is powerful technique for establishing good quality TV broadcasting. In cooperative decoding, some TV receivers, nodes, are cooperated, each other. These share the received information signal and thus obtain good quality information signal. Incremental-Maximum Ratio Combining (I-MRC) is one of the cooperative decoding methods. In I-MRC, the best condition's node and second one...
In this paper, we present a factor-graph based receiver for zero-padded orthogonal frequency division multiplexing (ZP-OFDM) transmissions over deep water channels with extremely long delay spreads. Due to the geometric structure of deep oceans, the channel delay spread between the direct paths and surface/bottom reflections can be on the order of hundreds of milliseconds, which is usually several...
In this paper, we consider design optimization of low-density parity-check (LDPC) coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems for high data rate wireless transmission. First, starting from the maximum-likelihood (ML) principle, we devise a novel expectation-maximization (EM)-based scheme for joint estimation of carrier frequency-offset (CFO)...
We propose the use of simple full interference cancellation (FIC) and orthogonal frequency-division multiplexing (OFDM) within a two-hop asynchronous cooperative four relay network. This approach can achieve the full available diversity and asymptotically full rate. The four relay nodes are arranged as two groups of two relay nodes with offset transmission scheduling. Therefore, the source can serially...
In this paper, we consider an OFDM-based cooperative diversity system where a source communicates with a destination with the help of a relay in Amplify-and-Forward relaying or Decode-and-Forward relaying. First, we propose a scheme to selecting the "best" relay to assist the transmission. And then, we present two power allocation schemes to minimize system outage probability, based on statistical...
In this paper, we employ to provide a method which combines Turbo codes and Low-Density Parity-Check (LDPC) codes based on Orthogonal Frequency Division Multiplexing (OFDM) system by adaptive encoding. The technique of channel estimation is used. The code rate and encoding scheme are all adaptive selection in the light of different channel conditions, so that we can make good use of these two types...
This paper proposes an OFDM based transmission scheme for asynchronous amplify-and-forward cooperative systems with two relay nodes over frequency-selective channels. To combat the inter-symbol interference from multi-path fading and timing errors, the cyclic prefix (CP) is used at both the source node and relay nodes. Unlike using IDFT and DFT modulation for two consecutive OFDM blocks respectively,...
This paper considers a two-hop orthogonal frequency division multiple (OFDM) wireless communication systems with a source, a decode-and-forward (DF) relay and a destination. We develop a low complexity rate adaptive power allocation strategy at the source and the relay, with respect to individual transmit power constraints, if the channel state information at the transmitter is given. To further enhance...
In this paper, we propose using chaotic digital filter to encode the time domain signal xn to reduce peak-to-average power ratio (PAR) in OFDM system. The xn may have high PAR value, which is a main drawback of OFDM system. The time domain signal becomes chaotically distributed by chaotic encoding, so the PAR value can be reduced. Simulations are done for numbers of subcarriers being 16, 32, 64, 128,...
In this paper, a low-complexity soft-output QRD-M detection algorithm is proposed for high-throughput Multiple-input multiple-output (MIMO) systems. By employing novel expansion and sorting scheme, the proposed algorithm can greatly reduce the numbers of the fundamental operations during the tree search process, especially the comparison operations which play a key role in the QRD-M detector' computational...
In this paper, we investigate distributed relay selection in OFDM-based cooperative wireless networks. A selective Decode-and-Forward relaying strategy is adopted, in which one relay is selected to forward the entire OFDM symbol. Theoretical outage performance is analyzed and evaluated first. Then six relay selection schemes based on different selection criteria are given. The outage performance of...
This paper gives the system model and the STBC encoding and decoding schemes in MIMO-OFDM system according to STBC coding theories. It focuses on researching and simulating the MIMO-OFDM system's performances, which had added STBC. We had analyzed and simulated BER performance of the system with different number of transceiver antennas. At the same time, BER performance of the system with different...
In this paper, we investigate a semi-blind maximum a posteriori probability-based channel estimator for Alamouti coded OFDM system over time varying Rayleigh channels. This channel estimation is used to handle rapid variations of channel within a transmission block. With the estimate of the channel matrix for the Alamouti symbol interval, a zero-forcing (ZF) receiver can be applied to detect this...
In this paper, we express the power consumption for the wireless receiver employing multiple antenna technique as a closed form function of the number of antennas, time duration, power dissipation for carrier sensing and data decoding, and the probability of successful carrier sensing. Based on the analytical model, we show that when MAC level power save mode is combined with PHY level power save...
We propose two practical schemes for the cancellation of nonlinear distortions caused by the power amplifiers (PA) in Orthogonal Frequency Division Multiplexing (OFDM) systems. The algorithms are iterative and located at the receiver. They utilize a soft channel decoder to improve the capabilities of the distortion estimation and relay all the computational complexity to the receiver. Simulation results...
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