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A pilot-aided integer frequency offset (IFO) estimation scheme robust to the timing offset is proposed for orthogonal frequency division multiplexing (OFDM)-based digital video broadcasting-terrestrial (DVB-T) systems. The proposed scheme first produces correlation values between each continual pilot (CP) and a predetermined scattered pilot (SP), and then, recorrelates the correlation values in order...
In this paper, based on mutually orthogonal (MO) ZCZ polyphase sequence (PS) sets proposed by Ref. [11], a method for improving the family size of ZCZ sequences in each set mentioned above is presented. As compared with Ref. [11], the resulting ZCZ sequences in each set can arrive to their theoretical bound due to expansion of their family size, whereas the length and width of ZCZ of ZCZ sequences...
Since the received MIMO-OFDM signal is usually corrupted in the time-domain due to some adverse factors such as frequency offset and large peak-to-average power ratio (PAPR) etc., a high-quality signal may only be obtained in the frequency domain. However, the second-order statistics of the time-domain signal are very often used in a blind or semi-blind channel estimation, which means that an IFFT...
This paper presents an architecture of an autocorrelator for Orthogonal Frequency Division Multiplexing systems. The received signal is quantized to only the sign-bit, which dramatically simplifies the frequency offset estimation. Hardware cost is reduced under the assumption that synchronization during acquisition does not have to be very accurate, but sufficient for coarse estimation. The architecture...
Next generation wireless systems are foreseen to adopt OFDM based transmission schemes. Unfortunately, conventional OFDM schemes suffer from the high mobility associated with next generation wireless systems, thus they need to be supported with enhanced techniques that alleviate the effects of the mobility. Among these, techniques for channel identification bear a particular importance. In this paper,...
Utilizing the characteristic of IEEE 802.16d downlink frame's format, this paper proposed a modified frame synchronization method, which can achieve a better frame synchronization. The first OFDM training symbol in long preamble is used for rough synchronization, and the second OFDM training symbol in long preamble is used for fine synchronization. Due to symbol repetition in long preamble, autocorrelation...
LMMSE algorithm is one of the best linear channel estimations for time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) system. The research on the computational complexity reduction of LMMSE algorithm remains to be a challenging topic. Since the combination of fast Fourier transform with singular value decomposition (FFT-SVD) simplify the channel autocorrelation matrix computation...
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, an adaptive MMSE channel estimation method is proposed for UWB-OFDM system. As we known, the MMSE algorithm is dependent on the auto-correlation of the known signals and the cross-correlation between the known signals and the signals to be estimated. These parameters are difficult to obtain in practice, because it needs a long-term statistic at the cost of huge complexity and time delay...
By analytical means, this paper investigates the application of a multi-periodic preamble for the synchronization in OFDM systems, which is based on an auto-correlation of the received signal. In contrast to common system configurations, the multi-periodic preamble enables to select the two parameters correlation shift and correlation window length independently of each other. This allows adapting...
In the cooperative relay system, different frames from different relays are not aligned in the time domain, and have different carrier frequency offsets (CFOs). Estimation of these time offsets and multiple CFOs is a crucial and challenging task. In this contribution, a new preamble structure is proposed, and the corresponding timing and frequency synchronization algorithms are also presented for...
Implementation of a carrier frequency offset (CFO) estimator with multiple correlation lags is presented in this paper. The proposed implementation breaks through the length constraint of single training sequence, and reduces the hardware cost of the estimator. A newly designed Automatic Frequency Control (AFC) loop are also proposed to achieve better utilization of multiple estimates and better trade-off...
OFDM system performance is sensitive to frequency offset and timing error than single-carried system. In this paper, a novel joint time and frequency synchronization method is proposed based on PN sequences for OFDM. A special training symbol of OFDM is constructed with the PN sequence and the differentially coded PN sequence in the transmitter, in the receiver, the training symbol is differentially...
To fulfill future airport capacity requirements, the proposed data link has to be a high capacity, high rate data link. Air-ground data link system can be used in orthogonal frequency division multiplexing (OFDM) systems to improve communication quality and capacity. A channel estimation design method for OFDM system by using correlation of pilot sequences has been proposed in this paper. The main...
In this paper, a complete solution to the initial synchronization for multi-cell OFDMA (orthogonal frequency division multiple access) systems is proposed. The proposed method consists of the following operations: timing synchronization, fractional carrier frequency offset (CFO) estimation, fractional CFO compensation, and joint integer CFO and preamble index estimation. To estimate multiple fractional...
In this paper, we propose a low-complexity carrier frequency offset (CFO) estimation algorithm for OFDM based wireless LAN, IEEE 802.11a. The complexity of the arctangent operation to calculate the argument of auto-correlation for CFO estimation is reduced by a novel range pointer method. The proposed algorithm estimates fine CFO value first and then based on the fine CFO value, simple criteria is...
Considering the features of Underwater Acoustic channel and the sensitivity versus synchronization for CI/OFDM system, A time and frequency synchronization method based on Constant Amplitude Zero Auto-Correlation(CAZAC) sequence is presented. The time offset estimation and carrier frequency offset estimation can be achieved simultaneously. The fractional part and integral part of carrier offset estimation...
The exact time-of-arrival (TOA) information of the multi-path signals is crucial for optimal channel estimation in vehicular OFDM systems. Super-resolution algorithms such as ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique) have been applied to retrieve this information from embedded pilots in the received OFDM symbols. These algorithms have high applicability for vehicular...
In the uplink of multi-user multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, there are multiple carrier frequency offsets (CFO's) from the multiple users. In this paper, we study algorithms to estimate these multiple CFO values. We first derive the maximum likelihood (ML) estimator and show that the complexity of the ML estimator increases exponentially...
To meet the demand of high data rate transmissions for multimedia wireless communications, orthogonal frequency division multiplexing (OFDM) systems in conjunction with multiple-input multiple-output (MIMO) signal processing have been considered one of the central techniques in advanced wireless communications. In the paper, two semiblind channel estimation algorithms are proposed for the uplink multiuser...
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