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In this paper, we present the baseband receiver design for IEEE 802.11ah. We study several key receiver algorithms, including coarse frequency offset estimation and coarse timing synchronization, fine frequency offset estimation, fine timing synchronization, channel estimation and MIMO equalization. For channel estimation, we propose to use decoded SIG field to improve its estimation. To further improve...
In the paper, operation algorithms of the N-OFDM modem for channels with the Additive White Gaussian Noise (AWGN) are considered. The algorithms are based on the Hartley transform under the optimal demodulation by the estimation of the received signals amplitudes using the Cauchy method. The experimental results for interference immunity estimation are provided for different values of spacing frequencies...
A novel blind time-frequency joint synchronization based on the cyclostationary of orthogonal frequency division multiplexing with offset quadrature amplitude modulation (OFDM/OQAM) systems is conceived in multipath channels conditions. The cyclic cumulants of OFDM/OQAM signals are derived firstly, symbol timing offset (STO) and carrier frequency offset (CFO) are estimated by employing two groups...
In this paper, we address the use of multi-layered sliding windows to detect the presence of a wireless network for cognitive radio applications. Although synchronization signals of the Long Term Evolution (LTE) has been used as the reference system, the proposed scheme is generic in principle. Our proposed scheme doesn't require any a priori knowledge of the exact synchronization sequences, so it...
In order to counteract hostile communication based on the advanced Orthogonal Frequency Division Multiplexing (OFDM) technology, an efficient and unrecognizable jamming technique by failing the OFDM cyclic prefix (CP) functionality is developed in the paper. CP is introduced into OFDM systems to prevent interference caused by the multipath fading, as long as it is no shorter than the channel delay...
We present an optimal frame timing estimator for OFDM signals that utilizes both cyclic prefix (CP) and pilot-carrier-aided channel estimation. Combining the periodic nature of the embedded pilot signal information with the correlation present in the cyclic prefix allows improved frame timing estimates relative to use of either one. Following a derivation of the ML estimator, a processor diagram is...
In this paper, we propose a new method to compensate Doppler frequency shift for OFDM-based underwater acoustic communication systems. In order to save bandwidth, we do not use additional signal header (preamble) in each OFDM frame as proposed in many conventional approaches. Instead, the central sub-carrier is reserved for pilot transmission. This subcarrier is so-called as the carrier frequency...
This paper evaluates the link-level performance of millimeter wave (mmWave) wireless communication system operating on 39.5 GHz frequency band. A frame structure based on the long term evolution (LTE) is proposed, including resource allocation and reference signal pattern. Some key parameters are carefully set to adapt to the mmWave frequency. Simulation results validate that the performance of mmWave...
We propose an effective synchronization and digital signal processing scheme for OFDM spectrum slicing transmissions in the presence of a large timing mismatch. Without loss of generality, a 76.8 Gbaud DP-16QAM OFDM three-slice spectrum slicing system was considered.
The problem of secure communication with the multi-antenna transmission in fading channel is an essential task. The fading channel is one of media for the eavesdropper to intercept when transmitting data. We investigate method for security in wireless communication. In particular, we focus on confidential transmission of pseudo-random location of subcarrier to increase security. This security method...
Filter bank-based multicarrier (FBMC) systems have been considered as a prevalent candidate for replacing the long established cyclic prefix (CP)-based orthogonal frequency division multiplexing (CP-OFDM) in the physical layer of next generation communications systems. In particular, offset quadrature amplitude modulation (OQAM)-based FBMC has received increasing attention due to, among other features,...
A joint timing offset (TO) and frequency offset (FO) estimation method based on Radon-Wigner transform (RWT) is first proposed for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systems. The result shows that the timing and frequency synchronization performance of the proposed method are both better than the Schmidl & Cox method and fractional Fourier transform (FrFT) algorithm...
We propose a symbol synchronization scheme based on Gold sequences modulated on a single pilot subcarrier for the OFDMA-PON. The IMDD real-time experimental demonstrations are carried out with two ONUs and one OLT. The results show that the accurate symbol synchronization can be achieved at received optical power of −21dBm on the condition of SFO range from 0ppm to 70ppm between two ONUs.
The need for high data rate is growing since the multimedia applications are gaining popularity which needs high data rate and quality of service. Multiple Input Multiple Output (MIMO) transmission system is one of the most promising approach of the Smart Antenna Technology which uses multiple antennas in the transmitter and the receiver side and is currently followed for high-rate wireless communication[1]...
In this paper, we propose a new technique for synchronization and channel estimation in M-QAM OFDM radio over fiber (RoF) system by using constant amplitude zero auto-correlation (CAZAC) sequence based training preamble. Delay and correlate method is used to identify the training sequence in the received signal vector and to correct the symbol timing offset. For an optimum demodulation of OFDM signal,...
In this study a new jammer design for orthogonal frequency division multiplexing (OFDM) based systems is in- troduced. We present three new vulnerability attack scenarios based on chirp signals. These are the conventional chirp attack, the cyclic prefix chirp attack and the pilot tone chirp attack. Bit error rate (BER) performances are investigated in presence of chirp based attacks. It is shown that...
This article describes a new approach in characterizing amplifiers and other two-port devices. Traditionally, key performance parameters such as gain or AM/AM and AM/PM distortion are characterized using a CW stimulus. However, most devices are operated with modulated signals instead of CW in real life. These key characteristics typically vary greatly between CW and modulated operation.
With the introduction of DVB-T2 in Germany and other European countries as new standard for Digital Video Broadcasting the underlying passive radar signal processing has also to be adapted, because the currently used predecessor, DVB-T, is not compatible to DVB-T2 on the physical layer. DVB-T2 has been improved in order to achieve a higher data rate and to allow more flexibility for different use...
LTE has several advantages to be investigated as transmitter of opportunity for passive radar in Germany: low carrier frequencies (i.e. low free space attenuation), high bandwidth (i.e. high range resolution) and wide area network (i.e. large availability). Therefore the signal correlation behavior is investigated. Additionally, a signal processing method is proposed for passive radar using LTE. The...
Direct device-to-device (D2D) communication is considered as a key technology and enabler for a multitude of new services in future fifth generation (5G) networks. Especially safety and emergency applications will require fast and reliable handover, seamless D2D connectivity and proper radio access to the cellular network. This paper proposes a novel handover scheme, which takes advantage of the D2D...
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