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OFDM is an important technology for 4G and being used of the wireless data communication, but it is very difficult to have a blind recognition method about subcarrier modulation type of OFDM. The characteristics of cyclostationarity modulation spectrum which will be not affected by noise, This paper gives out a blind recognition method about modulation types of OFDM subcarrier based on coefficient...
Impulse noise (IN) is one of the major impairments for data transmission over power lines. For power line communications (PLC) systems with bandwidths in the high kHz to MHz range, IN occurs in bursts. As long as those bursts are sufficiently short compared to a signal-processing (e.g. coding) frame, there is hope to successfully mitigate IN. In this paper, we introduce a new IN mitigation technique...
For non-contiguous OFDM (NC-OFDM) based cognitive radio (CR) systems, one of huge challenges is to establish spectrum synchronization before data transmissions. In this paper, we propose a novel active subchannel detection scheme for the NC-OFDM receiver without out-of-band spectrum synchronization information. The key idea of the proposed scheme is to employ the received training symbol to calculate...
This paper presents baseband receiver design for the third Generation Partnership Project (3GPP) Long Term Evolution (LTE) downlink systems under fast-fading channels. We aim to support 2×2 open-loop spatial multiplexing at high mobility up to 240 Km/hr with well-synchronized capability. The proposed receiver contains the functional blocks of mode detection, synchronization, channel tracking, inter-carrier...
Multiple-input multiple-output (MIMO) communications based on orthogonal frequency division multiplexing (OFDM) are considered for improving the performance and bandwidth utilization of underwater acoustic systems in which cooperation is possible between distributed transmitters. The major challenge in such a framework - and the principal difference from the traditional case where multiple transmitters...
The detector proposed in this paper tries to address the challenge of low signal-to-noise ratio signal detection in low-complexity MB-OFDM UWB receivers. The idea is to exploit the 128-point FFT of the UWB receiver to carry out frequency-domain energy detection. The main advantage of the proposed detector is that it only requires a memory buffer the size of the UWB receiver FFT, which makes it lighter...
The IEEE802.11ac task group has started to establish a next-generation WLAN standard. The wider channel of more than 80 MHz achieving over a 1-Gbps data rate is discussed. We have developed an experimental platform consisting of baseband and RF units in a 2×2 MIMO-OFDM system for the wider channel and evaluated its system performance in a field experiment. A MIMO-OFDM transceiver in the baseband unit...
We propose a dual diagonal linear-minimum-mean-square-error (DD-LMMSE) channel estimation algorithm for orthogonal frequency division multiplexing (OFDM) systems involving joint channel estimation and signal detection. Computational complexity and mean-square-error (MSE) analysis are presented to evaluate the efficiency of the proposed algorithm. Compared with the optimal LMMSE method, the proposed...
The performance of the classical low complexity OFDM detection is known to rapidly degrade with the raising of inter-carrier interference in the presence of fast time-varying channels. Advanced equalization techniques to mitigate the impact of the inter-carrier interference under those circumstances, generally involve significantly higher complexity. In this paper we address a class of reduced-complexity...
MIMO-OFDM performs signal detection on subcarrier-by-subcarrier basis and increases its computational complexity. A complete pipeline MMSE detector meeting requirements for a high throughput has been presented in our previous work, which provides real-time processing even for large numbers of subcarriers. However, it requires large circuit scale and tends to be excessive for small numbers of subcarriers...
Since 2008, The Federal Communications Commission (FCC) allows the operation of Cognitive Radio (CR) in unused parts (i.e. white spots) of the DTV spectrum. Due to the nonlinearity of the radio receiver and the existence of strong DTV signals, different types of distortion products will be generated in the CR-receiver. This paper analyzes the spectral location of distortion products across the white...
This paper presents part of the experimental results obtained during the French national research project GRACE, which deals with opportunistic cognitive radio and spectrum management. The consortium, composed by French big- and small-size companies and research institutes, proposes a cognitive orthogonal frequency division multiplexing (OFDM) signal based on IEEE 802.16e standard, with time-windowing...
Phase noise causes common phase error (CPE) and intercarrier interference (ICI) in orthogonal frequency division multiplexing (OFDM) system. To mitigate the effects of phase noise, many schemes have been proposed, but they are either computationally complex or at the price of sacrificing spectral efficiency. In this paper, a continuous Hopfield neural network (HNN) is designed for OFDM signal receiver...
Based on the variational Bayes expectation-maximization (VBEM) algorithm, a low complexity semi-blind Bayesian iterative receiver with joint signal detection and channel tracking is proposed in this paper for MIMO-OFDM systems over time-varying multi-path channels. Since the VBEM algorithm provides distribution estimation of all parameters, the detection performance can be improved by taking the channel...
In this paper, we describe a novel design of a Peak-to-Average-Power-Ratio (PAPR) reducing system, which exploits the relative temporal sparsity of Orthogonal Frequency Division Multiplexed (OFDM) signals to detect the positions and amplitudes of clipped peaks, by partial observation of their frequency content at the receiver. This approach uses recent advances in reconstruction of sparse signals...
In the uplink of OFDMA systems, carrier frequency offsets (CFOs) can be compensated directly at the receiver by several methods. Particularly, Cao and Tureli applied minimum mean square error (MMSE) criterion to recover individual ideal waveform exploiting multiuser signal structure characteristic inherent from an interleaved subcarrier assignment. In this paper, the explicit signal-to-interference...
Sensing of orthogonal frequency division multiplexing (OFDM) signals at low signal-to-noise ratio (SNR) is of great importance for cognitive radio (CR) communications due to the wide applications of OFDM in many existing and evolving broadband wireless communications. In-band pilots, multiplexed with the data-carrying subcarriers, provides one distinct feature of OFDM signals. The objective of this...
Direct conversion receivers are attractive for low cost systems as they avoid intermediate frequency (IF) filters. However, the direct conversion from radio frequencies (RF) to complex inphase (I) and quadrature (Q) baseband signals in one mixing step introduces additional front-end distortions. These IQ distortions lead to a degradation in the system performance. The problem becomes more significant...
It is well known that carrier frequency offsets caused by inaccuracies of local oscillators between transmitter and receiver stations destroy the orthogonality among OFDM subcarriers and induce additional intercarrier interference. In conjunction with MIMO transmission where different users interfere with each other, this effect strongly degrades the signal detection performance if it is not compensated...
A practical variational Bayes (VB) iterative receiver with joint signal detection and channel estimation is proposed in this paper for MIMO-OFDM systems in time-varying multipath channel. Since the VB method provides distribution-estimates of the parameters, the soft-input soft-output (SISO) QRD-M algorithm is exploited to estimate the signal distribution, and several channel estimation algorithms...
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