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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...
We proposed a new method for timing estimation in cognitive radio systems under a fractional bandwidth (FBW) scenario. A conventional timing estimation based on autocorrelation suffering performance reduction caused by interference and multipath channel distortion. The proposed method is developed based on normalized 4-th order moment for symmetric correlator. Based on these 4-th order moment, a binary...
Carrier frequency offset (CFO) estimation must have sufficient precision for orthogonal frequency division multiplexing (OFDM) systems due to its sensibility to orthogonality between sub-carriers, especially for high rate OFDM transmission with narrow sub-carrier spacing. In time domain synchronous OFDM (TDS-OFDM), time domain pseudo-noise (PN) sequences are inserted between adjacent data blocks as...
Traditional OFDM based transmission system uses Cyclic Prefix (CP) in an OFDM symbol in order to maintain orthogonality of transmission. Present days' Ultra-Wideband (UWB) systems use Multi-Band OFDM (MB-OFDM) techniques for transmission in application like Wireless Personal Area Network (WPAN). UWB based systems are power limited by the regulation of FCC. CP introduces correlation in the transmitted...
This paper presents a low-complexity architecture compensating for carrier frequency offset (CFO) and IQ imbalance circuits in MIMO-OFDM receiver systems. A coordinate rotation digital computer based sinusoid iteration generator is also developed for CFO estimation and correction in wireless communication receivers. Besides the main effect from the multi-path, some non-ideal effects from imperfect...
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...
The underwater acoustic channel is a complicated and time-varying multipath channel, especially for the mobile applications in the littoral. To accommodate the execrable channel conditions, a robust communication scheme is proposed, which combines the differential frequency hopping (DFH) and multi-carrier technologies. Also a novel Doppler-shift estimation and synchronization method is presented,...
A novel timing offset estimation scheme for orthogonal frequency division multiplex (OFDM) systems is proposed in this paper, which can eliminate the ambiguity of the first arriving path estimation in multipath channels. The timing of the first arriving path is determined by detecting the first falling edge of the sliding window of the correlation result. A predefined threshold is adopted to validate...
This paper proposes a novel symbol timing estimation technique for multiband orthogonal frequency division multiplexing (MB-OFDM) based ultra wideband system. The symbol timing is estimated in two steps namely, coarse synchronization and fine synchronization. The coarse synchronization is obtained using the correlation between adjacent symbols. A new algorithm is proposed using maximum likelihood...
Ultra wideband communication is a promising technology with attractive features of low power, low complexity transceiver and rich multipath diversity that can be used for transmitting both high and low data rates. Exploiting the inherent capabilities of UWB communication is up to perfect synchronization between transmitter and the receiver which is a serious bottleneck of these systems. Using very...
In this paper, two fast and accurate FFT-based frequency offset estimation methods for OFDM systems are proposed. We analyze and simulate proposed methods in both Gaussian and multipath fading channels, and compare the results with those obtained using well known Schmidl's method. The simulation results are presented in terms of Error Variance (EV). Both proposed FFT-based methods have significantly...
Time offset estimation is one of the main tasks of the initial ranging process in orthogonal frequency-division multiple access (OFDMA)-based network. Recently, the multiuser time offset estimation based on phase shift over adjacent subcarriers has been presented. This method can reduce the huge computation complexity of the timing recovery based on peak correlation searching of long PN codes. The...
In orthogonal frequency division multiple access (OFDMA) uplink system, estimations of time delay and carrier frequency offset (CFO) are both particularly challenging. In this paper, a coarse CFO and time delay estimation method is proposed for interleaved OFDMA uplink system. By exploiting the special scheme of interleaved OFDMA, the repetitive time-domain training symbol is designed, and the training...
Time domain synchronous orthogonal frequency division multiplex (TDS-OFDM) is an effective multi-carrier modulation scheme to improve the spectrum efficiency. However, conventional synchronization algorithm based on the correlation property of the time-domain pseudo-noise (PN) sequence may not work well over severe multipath fading channels when large carrier frequency offset (CFO) exits. In this...
Timing and frequency synchronization is the important task in receiver. In this paper, an efficient timing and carrier frequency offset (CFO) estimation algorithm for orthogonal frequency division multiple access/ time division duplexing (OFDMA/TDD) mode in IEEE 802.16-2004 standard (WiMAX) is represented. This method has high performance and jointly estimates timing error and CFO. The performance...
Synchronization is a key problem of orthogonal frequency division multiplexing (OFDM) systems. OFDM is very sensitive to synchronization error, especially the symbol timing synchronization error. Two new methods of timing synchronization estimation for OFDM systems based on the former synchronization method are proposed, which both utilize new training sequence and estimators to overcome the shortcomings...
Orthogonal frequency division multiplexing (OFDM) systems are more sensitive to timing and frequency offsets than single carrier systems. This paper presents a method of joint time and frequency synchronization for OFDM systems. The synchronization technique is examined in both AWGN and multipath fading environments. Compared with conventional schemes, the proposed schemes can achieve smaller mean...
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...
Multiple antenna systems have been shown to provide significant performance improvements for network nodes; however, the vast majority of nodes in military networks will be limited to single channel devices due to mobility (size and power) and ease of use considerations. In this paper we apply a new joint synchronization-pilot sequence (JSPS) optimization design technique to multiple transmitter OFDM...
In this paper we present a time delay estimation algorithm for known symbol padding (KSP) orthogonal frequency division multiplexing (OFDM) systems. The estimator exploits both the pilot symbols in the guard interval and on the pilot carriers, and takes the frequency selectivity of the fading channel into account. Our simulations indicate that the time delay estimator gives rise to only a small degradation...
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