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Frame discrimination algorithms are discussed that address the problem of differentiating user frames transmitted asynchronously through optical fading channels. In communications systems where multiple users transmit asynchronously, fading channels can render the received frames unidentifiable at the receiver so that intended user destinations for the frames are then unknown. Algorithms that are...
In this paper, a blind synchronization algorithm for estimating the symbol timing offset and the carrier frequency offset (CFO) in OFDM systems has been presented. The synchronization parameters are estimated by utilizing the correlation attribute of the samples of the received signal. The Cramer-Rao lower bound (CRLB) of the CFO estimation has been derived over the entire delay spread of the fading...
Self-encoded spread spectrum systems derive spreading codes from the data stream and have been shown to achieve a 3 dB power gain while providing time diversity for robust performance in wireless fading channels. Since the receiver does not knowledge of the initial spreading code, these systems present a unique challenge to code synchronization. In this paper, we present a method to achieve code acquisition...
In this paper, we present a novel technique for coarse timing synchronization for Asymmetrically-Clipped Optical Orthogonal Frequency Division Multiplexing (ACO-OFDM) systems. This technique is tailored specifically for the ACO-OFDM waveform, and performs coarse symbol timing synchronization without the need for training data. By using a specific symmetry property of the ACO-OFDM time-domain signal,...
In this paper, a novel OFDM symbol timing recovery method, which is robust to doubly selective fading channels and carrier frequency offset, is proposed for the mobile terminals of CMMB system. The time slot timing synchronization is accomplished by using the inverse sliding correlation between the segmenting Sync sequences, which possess the inverse conjugate symmetry (ICS) characteristic. Furthermore,...
Time domain synchronous orthogonal frequency division multiplex (TDS-OFDM) is an effective multi-carrier modulation scheme to improve spectrum efficiency. Conventional synchronization algorithm based on the time-domain differential correlation of the pseudo noise (PN) sequence may not work well in severe multipath fading channels. In this paper, a robust synchronization algorithm is proposed where...
A novel cell search scheme based on coherent sequence detection and sign decision is proposed in this paper. The given structure of the SCH (synchronization channel) allows the UE (user equipment) to detect cell ID with low complexity, and the adverse effects of the channel fading and frequency offset are eliminated in the three search steps. The performance of the scheme is investigated in various...
In order to increase the accuracy of timing estimation in frequency selective fading (FSF) channels and reduce the computational complexity, in this paper an adaptive symbol synchronization of OFDM blind channel estimation is proposed. First, by the ML algorithm used in flat fading channels, we give a rough estimated time position dML, then choose Δd, and give the maximum d1 of the measure function...
The correlation-based method is the popular solution for timing synchronization. The performance of this method is decreased in low signal-to-noise ratio (SNR) because of the limited correlation peaks. In this paper, a new method based on more peaks by using a new structure of the short preamble is proposed. Simulation results show that the proposed approach greatly improves the estimation accuracy...
In this paper, we propose a coarse and fine frequency synchronization method which is suitable for the 3rd Generation Partnership Project (3GPP) long term evolution (LTE) orthogonal frequency division multiple access (OFDMA) system in time division duplexing (TDD) mode. In general, primary synchronization signal (PSS) correlation based estimation method and cyclic prefix (CP) correlation based tracking...
In LTE system, maximum likelihood algorithm based on cyclic prefix is used to accomplish the symbol and slot synchronization. Zadoff-Chu sequences finish frame synchronization and cell search. But in low signal-to-noise ratio AWGN channels and multi-path fading channels, the maximum likelihood peak values are not stable in the right place due to high noise effects, multi-path delays and Doppler effects...
In wireless sensor networks, localization in indoor environment suffers from non-LOS (line-of-sight) and multi-path fading. In this paper, a new localization algorithm is proposed, which makes essential use of distributed space-time-codes (DSTC) to combat fading. By cleverly devising DSTC and employing a novel ML synchronization technique, the proposed algorithm exploits the full benefits of TDOA...
An OFDM structure based on super-imposed pseudo-random sequences for time domain synchronization is proposed. A time synchronization method is proposed, which is exactly located in the first channel delay by periodically super-imposed sequences. The amplitude value of each channel path estimated with minimum mean square error (MMSE) can be easily deduced with help of periodical sequences. For depth...
In this paper, we propose a modified version of the well-known delay looked loop (DLL) timing synchronizer, which is specifically designed to take into account the characteristics of a class of receiver architectures that has been experiencing a renewed interest in the frame of ultra wide band (UWB) transmission systems, i.e., the Differential Transmitted Reference (DTR) receiver. The proposed solution...
In this paper, we propose a Coarse Symbol Timing Synchronization (CSTS) algorithm for OFDM systems that is robust to a multi-path fading channel. Based on the fact that multi-path channel distorts the correlation value within a guard interval, we employ a variable-length window for correlation in CSTS. Simulation results show that the proposed method outperforms the conventional correlation methods...
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