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The problem of carrier frequency and phase synchronization exists in most wireless digital communication systems. These offsets are generally results from the Doppler effect, oscillator instabilities, and unknown transmission delays between receiver and transmitter. In this paper, we propose a joint synchronization algorithm applicable for short-burst PSK modulation systems. In the coarse estimation,...
Owing to the growing demand for the high-speed wireless communications which uses Orthogonal Frequency Division Multiplexing (OFDM), there is a need to provide high-quality to overcome various channel impairments appearing over the transmission link. One of the main problems in providing such mechanisms is Doppler shift. which reduces the spectral efficiency of the system, raising a need to determine...
In this paper, a pilot-aided frequency synchronization scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed. A maximum likelihood (ML) estimator based on Double Dwell Synchronization (DDS) is employed for offset estimation and correction. The proposed DDS scheme provides an accurate estimate over a wide estimation range with reduced computational complexity for both AWGN...
In this paper, we propose a robust timing and frequency synchronization algorithm for the orthogonal frequency division multiplexing (OFDM) systems. The algorithm we proposed can achieve accurate timing and frequency synchronization in time-domain by using the preamble consisting of only one training symbol based on constant amplitude zero autocorrelation (CAZAC) sequence and a new weighting factor...
This paper shows that preamble detectors, based on the mathematical and statistical properties of M-ary symbols in ISI-free environments, can provide reasonably good performance when operating on SOQPSK-TG samples in the presence of unknown ISI and a frequency offset. Of the preamble detectors examined in this paper, the preamble detector based on the concept of non-coherent post-detection integration...
Considering both large cost and high complexity of current carrier synchronization systems at low Signal-to-Noise Ratio (SNR), an adaptive carrier synchronization system design in accordance with Green communication is proposed. First, the proposed design takes advantage of parameter control method to change an optimal scheme to some suboptimal schemes. Within the requirement of satisfying less SNR...
Nowadays, correlator is a crucial part of communication systems. The correlation function has a great practical importance when it is necessary to process a signal in the presence of noise. Use of correlator in modern communication system have more precise frequency and timing synchronization, which improves its ability against interference of multipath and frequency selective fading channels. Even...
In the cell search scheme of 3GPP Long Term Evolution (LTE), time and frequency synchronization are the first step and its performance will affect the entire synchronization process. Time and frequency synchronization can be acquired by the detection of primary synchronization signal (PSS) in conventional scheme. However frequency offset will degrade the performance of time synchronization. Based...
For Integer carrier Frequency Offset(IFO) leads to cyclic shift of subcarrier data in OFDM system, it should be corrected before the OFDM demodulation. In order to resist the selective fading in frequency domain and time domain, the conventional algorithms use the blind estimation method or training sequences in the two sequential OFDM symbols to get the IFO estimation value. These algorithms demand...
For inter-vehicle communications, the IEEE 802.11p standard has been employed in the U.S. and Europe. This configuration is an OFDM-based system, so it still has to cope with the issue of frequency synchronization. In this paper, a pilot-aided estimation technique is developed for the compensation of frequency offset in the IEEE 802.11p environments. The proposed synchronization algorithm utilizes...
This paper investigates the legacy compatibility between IEEE 802.11n and 802.11a/g devices, focusing on the performance of legacy 802.11a/g auto-correlation and cross-correlation joint time and frequency synchronization schemes operating over 802.11n networks. It is shown that synchronization schemes based on auto-correlation metric allow the backward compatibility, considering a different number...
In this paper, a jointed preamble/boundary detection and fractional carrier frequency offset (CFO) estimation design is presented which supports dual SC/HSI modes of IEEE 802.15.3c applications. Based on correlation based algorithms which utilizes the structure of preamble, an efficiency architecture is proposed which realizes synchronization detection with a sequential detection scheme and only single...
In the first part of this paper an audio watermarking system, operating in log-spectrum domain, is presented. Special measures are taken to make this system robust to symbol time offset. In the second part algorithms for sampling frequency offset and symbol time offset estimation and correction are proposed. These algorithms are based on inaudible pilot tones insertion and assure robust watermark...
This paper addresses problems related to time and frequency synchronization as well as blind CP (cyclic prefix) type identification in 3GPP LTE system. We start with a general framework based on maximum likelihood (ML) parameter estimation. Then, simplified practical algorithms for estimating time and frequency offset as well as blind CP length are described. Finally, a robust hierarchical scheme...
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 this paper, a measurement method for DTMB modulator which performs the estimation of timing and frequency offsets, channel impulse response (CIR), as well as modulation error ratio (MER) by using only two consecutive frames in an iterative manner is proposed to precisely measure the modulator performance in short time. Both simulation and lab testing results show that the measurement method could...
In this paper, we propose an efficient scheme using a new single-symbol preamble structure for OFDM data-aided synchronization. The preamble symbol is constituted of two successive equal-duration sub-symbols, the second one of which is a differentially encoded version of the first one, using an adequately designed precoding sequence. This structure leads to almost perfect channel autocorrelation profile...
A new method for frequency synchronization based upon Zero-Intermediate Frequency (zero-IF) receiver and characteristics of the received signal's power spectrum for MC-DS-CDMA-Uplink system is proposed in this paper. The variance for Carrier Frequency Offset (CFO) estimators of MC-DS-CDMA-Uplink is compared with that of an OFDM system to estimate the CFO. Our study and results show that the MC-DS-CDMA...
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...
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