Carrier Frequency Synchronization Research Articles

Carrier Frequency Synchronization of LDPC Coded Transmissions in High Dynamic Environments

Carrier Frequency Synchronization of LDPC Coded Transmissions in High Dynamic Environments

Design of Downlink Synchronization for Millimeter Wave Cellular System Based on Multipath Division Multiple Access

This work focuses on the design of downlink receiver for future generation cellular systems. In the multipath division multiple access (MDMA) system, the initial synchronization process includes timing and carrier frequency synchronization as well as home cell search. For the proposed system, the user data is transmitted in time domain and the cell search is based on control signals transmitted in frequency domain simultaneously. Firstly, this paper presents a novel architecture for the joint detection and estimation of both the coarse symbol boundary and the fractional carrier frequency offset based on cyclic prefix in time domain. Secondly, a robust integer carrier frequency offset detection is performed with the primary control tone in frequency domain. Moreover, the position of the secondary control tones is used to obtain the cell ID. Finally, the preamble sequence carried by the secondary control tones is used to detect frame header through differential detection. The simulation results show the proposed synchronization algorithms can achieve detection failure rate less than 1% and the normalized residual carrier frequency offset is less than 5% under the interference of user data. Furthermore, a hardware design targeted at 200 Mbps per-user data rate is realized with memory arbiter to share memory.

Joint carrier frequency and symbol timing synchronization sequence for FBMC based system

Filter Bank Multicarrier (FBMC) is a multicarrier scheme that employs shaping filter for improved spectral properties. In this paper, a low complexity data-aided symbol timing and carrier frequency offset synchronization technique for FBMC is presented for continuous mode transmission. Two training sequences based on Zadoff–Chu sequence are proposed. The first sequence is called the Long Sequence that takes 9 FBMC symbols, it avoids the interference with data symbols and the second is called the Short Sequence that takes 3 FBMC symbols, it is a modified version of the Long Sequence for better spectral efficiency. An autocorrelation-based synchronization metric is used that exploits the repetition of samples in the received training sequence. High peak is produced by the synchronization metric during reception of the training sequence compared to the metric values during reception of data samples. This makes it easy for the receiver to recognize the training sequence and to perform the related estimates of the symbol timing and carrier frequency offset. The training sequence is also used for channel estimation. The performance was evaluated under different channel conditions for two different shaping filters.

Development of a Low-Cost Multistatic Passive Weather Radar Network

Practical and accurate estimation of 3-D wind fields is an ongoing challenge in radar meteorology. Multistatic (single transmitter/multiple receivers) radar architectures offer a cost-effective solution for obtaining the multiple Doppler measurements necessary to achieve such estimates. Existing multistatic weather radars, while less costly than comparable monostatic networks, have been constrained by the need for specialized equipment and software to perform frequency and pulse timing synchronization with the transmitting radar. This article describes the implementation of a passive radar network that performs pulse timing and carrier frequency synchronization through measurements of the sidelobe radiation of the transmitting radar. This makes it possible for the receiver modules to be constructed with minimal size and cost, and it allows for their use in coordination with any in-band transmitter capable of recording time-stamped pointing angle information. A prototype network consisting of two passive receivers has been constructed in the Oklahoma City, OK, USA. Weather observations collected using the radiation from a WSR-88D have been used to validate the accuracy of velocity measurements obtained through this technique.

Millimeter-Scale Node-to-Node Radio Using a Carrier Frequency-Interlocking IF Receiver for a Fully Integrated 4$\times$ 4$\times$ 4 mm3 Wireless Sensor Node

Ultralow-power (ULP) mm-scale Internet-of-Things (IoT) platforms enable newly emerging applications such as pervasive agricultural monitoring and biosensing. Although there is an increasing interest in node-to-node communication as defined in Bluetooth v5.0, prior research in mm-scale wireless systems is mostly limited to asymmetric node-to-gateway communications. We present a 2.4-GHz node-to-node communication system for an ultra-small wireless sensor node fully integrated within a 4 $\times $ 4 $\times $ 4 mm3 form factor. The system integrates multiple stacked layers including an RF transceiver, a ULP processor, a photovoltaic (PV) cell, a 32-kHz crystal, and a 3-D magnetic dipole antenna. The transceiver front-end circuit is co-designed with a printed 3-D magnetic dipole antenna to form a power oscillator for the transmitter (TX) as well as a $Q$ -enhanced amplifier (QEA) for the receiver (RX). A new carrier frequency-interlocking IF architecture successfully mitigates the TX–RX carrier frequency synchronization challenge that is critical to the mm-scale radio systems. The complete system achieves −94-dBm sensitivity with 97- $\mu \text {W}$ power consumption and −12.6-dBm equivalent isotropically radiated power (EIRP). Standalone operation of a sensor node is demonstrated through bi-directional wireless communication to another sensor node over 1-m distance in real, uncontrolled wireless channels.

Time and Carrier Frequency Synchronization for Coherent Optical Communication: Implementation Considerations, Measurements, and Analysis

We develop a measurement scheme for the time and frequency offsets, along with their compensation, for a coherent optical receiver. This relies on a modified constant amplitude zero autocorrelation sequence-based method, which is implemented on a field-programmable gate array. Experiments are performed for an optical orthogonal frequency-division multiplexing transmission system. The performance of the proposed scheme is compared to a MATLAB-based implementation of the original scheme. The contributory factors to the error between these two schemes, as well as the implementation complexity, are investigated. Experimental measurements demonstrate that the proposed scheme closely matches the performance of the original scheme while utilizing fewer hardware resources.

Efficient Weighted Least-Squares Frequency Synchronization Scheme for Digital Terrestrial Broadcasting System

The integrated services digital broadcasting-terrestrial (ISDB-T) system provides the interesting advantages of hierarchical transmission and partial reception using band segmented transmission orthogonal frequency division multiplexing scheme. In ISDB-T, the hierarchical configuration varies depending on whether a segment is modulated coherently or differentially. Thus, it is important to accomplish frequency synchronization regardless of segment type. For this purpose, an effective weighted least-squares (WLS) carrier frequency synchronization method is presented using transmission and multiplexing configuration control (TMCC) and auxiliary channel (AC) in a blind manner. Thus, the proposed estimation scheme is performed without resorting to a priori knowledge on segment type that can be known after correct TMCC decoding. To eliminate bias caused by using non-uniformly distributed TMCC and AC subcarriers, an appropriate subset is selected to form the basis of robust WLS estimation. Extensive simulations are conducted to verify the efficiency of the proposed WLS estimation method and compare its performance with that of the conventional WLS estimation scheme.

Design of OFDM Joint Synchronization Algorithm Based on Cyclic Prefix

By studying the Maximum Likelihood (ML) algorithm and applying it to Orthogonal Frequency Division Multiplexing (OFDM) system, we analyze its performance. OFDM system has obvious advantages over other wireless communication systems, but it also has disadvantages, such as being sensitive to synchronization errors. The ML algorithm can solve this shortcoming of OFDM system. ML algorithm uses the redundant information carried by the cyclic prefix in OFDM code element. At the same time, ML algorithm calculates its maximum likelihood estimation algorithm to complete the code element timing synchronization and carrier frequency synchronization. Compared with other synchronization algorithms, ML algorithm can complete initial capture and synchronous tracking in one step, so it is widely used in OFDM systems. In this paper, we build a traditional OFDM system and apply the ML algorithm to OFDM synchronization simulation. By changing the design of relevant parameters, we describe the ML algorithm in detail and obtain the same results as the theory.

A carrier frequency estimation algorithm for Multi-h CPM signals

Considering the problem that Multi-h CPM signal transmission performance is excellent but carrier frequency synchronization is complex, the article proposed a multi-h CPM non-data assisted carrier frequency estimation algorithm based on maximum likelihood. Firstly, the importance of carrier frequency synchronization is explained by simulating the influence of carrier frequency offset on transmission error performance. Then, the carrier phase deviation, frequency deviation, propagation delay, modulation index error and symbol error joint likelihood function in signal transmission are given. The likelihood function is derived and the maximum likelihood carrier frequency estimation is derived in detail. Then the flow chart of the carrier frequency synchronization algorithm based on maximum likelihood is designed. Finally, the ARTM Tier2 signal is simulated by Matlab simulation. The results show that the proposed algorithm is suitable for Multi-h CPM signals and has good carrier frequency estimation performance, and is insensitive to symbol timing deviation and modulation index synchronization error.

Distributed Time and Carrier Frequency Synchronization for Dense Wireless Networks

Dense networks call for interconnectivity of a large number of devices, and in this context, the diversity of interconnected devices introduces challenges to be considered for management and coordination of the network. Synchronization of timing (TO) and carrier frequency offsets (CFO) are critical aspects to be considered to guarantee the proper network interconnectivity. This paper addresses a distributed synchronization method for dense (say $\geq$ 50 nodes), compact, and possibly strongly connected wireless network where the internode distance is small and propagation delay of the entire network is not negligible compared to the inverse of signal bandwidth. Signatures are periodically transmitted by every node to mark the start of the payload and to broadcast the synchronization state that is iteratively minimized by all nodes in aligning jointly the TO/CFO skew with the consensus-type algorithms. Here, the same signature is broadcasted by every node and it collides with those of the others to perform as a reference (compound) signature for receiving nodes that embeds the reference TO/CFO of the network for synchronization. In view to make distributed TO/CFO synchronization practicable, this paper aims to: first, compensate the propagation delays between nodes to mitigate their impact on the global TO/CFO synchronization of the network; second, design and validate chirplike signatures based on Zadoff–Chu sequences that enable the estimate of the TO and CFO mismatch on every node and decouple TO and CFO estimates; and finally, evaluate the mean-square convergence conditions for nodes employing realistic and unstable oscillators. Numerical validations are based on TO/CFO synchronization for orthogonal frequency division multiplexing (OFDM) system.

Zadoff-chu sequence based preamble design of fbmc/oqam for 5g

The Spectrum effectiveness for 5G networks can be accomplished by Filter Bank Multi Carrier / Orthogonal Quadrature Amplitude Modulation (FBMC / OQAM) that avoids the benefit of guard band. FBMC is very considerate to Carrier Frequency Offset (CFO) and Timing Offset (TO). This paper suggests Zadoff-chu (ZC) sequence based preamble or pilot is accustomed to design the FBMC frame for synchronize more with receiver to achieve sufficient channel inference and phase tracking which reduces the carrier frequency and timing synchronization. This method helps to influence the out of band emissions and conceive non-orthogonal waveforms to investigate the overall system performance such as Bit Error Rate (BER) over AWGN channels. The performance measuresbeing Complementary Cumulative Distribution Curve (CCDF) for FBMC signal with different multicarrier to evaluate the Peak to Average Power Ratio (PAPR) has been achieved by simulation. The simulation outcomeshows that FBMC outperforms well when analyzed with other multicarrier systems.

Быстродействующий алгоритм восстановления несущей частоты и кадровой синхронизации в модемах с QPSK-модуляцией

When demodulating signals in communication systems with QPSK modulation operating in the pulsed mode, the following problems arise: rapid elimination of the reference oscillator phase ambiguity and ensuring reliable frame synchronization for a given noise immunity. In most QPSK modems, the carrier frequency recovery and synchronization recovery tasks are separated and solved with the help of different functional modules, which is not the optimal solution from the point of view of increasing the energy efficiency. In this paper, we propos a fast algorithm for frame synchronization and recovery of the carrier frequency of a QPSK modem using Barker sequences as synchronization signals in conjunction with the coordinated processing. The simulation of the combined circuit is performed, which allows to eliminate the phase ambiguity of the reference oscillation with the simultaneous formation of the frame synchronization signal for various combinations of binary sync codes of the length N = 7. To obtain a reference oscillation, a stable quartz oscillator is used. An external adjustable phase shifter block abruptly changes the phase of the oscillator, and the phase ambiguity, which is multiple of 90°, is eliminated by parallel analysis of all possible rotations of the signal constellation plane in the units, each of which contains a pair of filters matched to the signal distributed over in two quadratures. The timing for the proposed scheme does not depend on the initial phase difference between the received and the initial signal constellations, while the circuit realization of a non-tunable oscillator is much simpler than that for a voltage controlled oscillator.

Discrete FRFT-Based Frame and Frequency Synchronization for Coherent Optical Systems

A joint frame and carrier frequency synchronization algorithm for coherent optical systems, based on the digital computation of the fractional Fourier transform (FRFT), is proposed. The algorithm utilizes the characteristics of energy centralization of chirp signals in the FRFT domain, together with the time and phase shift properties of the FRFT. Chirp signals are used to construct a training sequence (TS), and fractional cross-correlation is employed to define a detection metric for the TS, from which a set of equations can be obtained. Estimates of both the timing offset and carrier frequency offset (CFO) are obtained by solving these equations. This TS is later employed in a phase-dependent decision-directed least-mean square algorithm for adaptive equalization. Simulation results of a 32-Gbaud coherent polarization division multiplexed Nyquist system show that the proposed scheme has a wide CFO estimation range and accurate synchronization performance even in poor optical signal-to-noise ratio conditions.

Distributed Synchronization on Weakly Connected Networks

Distributed synchronization for wireless networks is based on the mutual exchange of the same chirp-signature by nodes. Collisions of these signatures drive the system toward time and (carrier) frequency synchronization using distributed consensus algorithms. This letter investigates the convergence and the asymptotic distortion properties on noisy networks when neighboring clusters of nodes are weakly connected to each other only through a subset of nodes and bridging links. These heavily connected clusters act as macroagents, and the consensus properties of the ensemble depend on the number of bridge links between them. The convergence rate and mean square synchronization deviation are derived as functions of the number of bridge links for different examples of weakly connected noisy networks via the analytic calculation of Laplacian spectra. Our approach facilitates the study of network topology optimization for distributed synchronization.

Near-Coherent QPSK Performance With Coarse Phase Quantization: A Feedback-Based Architecture for Joint Phase/Frequency Synchronization and Demodulation

As communication systems scale up in bandwidth, the limited resolution in high-speed analog-to-digital converters (ADCs) is a key challenge in realizing low-cost “mostly digital” transceiver architectures. This motivates a systematic effort to understand the limits of such architectures under the severe quantization constraints imposed by the use of low-precision ADCs. In particular, we investigate a canonical problem of blind carrier phase and frequency synchronization with coarse phase quantization in this paper. We develop a Bayesian approach to blind phase estimation, jointly modeling the unknown data, unknown phase and the quantization nonlinearity. We highlight the crucial role of dither, implemented via a mixed signal architecture with a digitally controlled phase shift prior to the ADC. We show the efficacy of random dither, and then improve upon its performance with a simple feedback control policy that is close to optimal in terms of rapidly reducing the mean squared error of phase estimation. This initial blind phase acquisition stage is followed by feedback-based phase/frequency tracking using an Extended Kalman Filter. Performance evaluations for a QPSK system show that excellent bit error rate (BER) performance, close to that of an unquantized system, is achieved by the use of 8 phase bins (implementable using 4 one-bit ADCs operating on linear combinations of in-phase and quadrature components).

Carrier Frequency Synchronization in Distributed Wireless Sensor Networks

Carrier frequency synchronization is a difficult problem in distributed wireless sensor networks (WSNs) due to its high-precision requirement. In this paper, we propose simple and easily implementable carrier frequency synchronization for distributed WSNs with a master–slave structure. The slave sensors receive the calibration signal broadcasted from the master sensor (base station) and modulate them in a novel manner such that the retransmitted signal can be easily extracted by the master sensor to compensate the carrier frequency synchronization errors. The advantage of this method is that it does not require a priori establishment of the time synchronization between the master sensor and slave sensors and that no additional resource would be required to transmit as synchronization signal. Moreover, the impact of Doppler frequency shift is canceled to some degree in this approach. We present the carrier synchronization compensation algorithm and discuss several practical implementation issues. We also derive the stochastic Cramer–Rao lower bound performance analysis of the method and provide numerical results that validate the analysis.

Frame and carrier frequency synchronization algorithm for wireless body area network

SummaryA wireless body area network (WBAN) is a radio‐frequency‐based wireless communication technology that consists of a number of different sensor and actuator nodes interconnected with a body gateway. Considering the constrained resources in WBAN devices, simple and noise‐robust synchronization algorithms are required. Frame synchronization and frequency offset estimation are extremely important in the design of a robust WBAN receiver. In this paper, a detection strategy such as frame synchronization and frequency estimation is described in the WBAN system, which can improve the receiver performance. In doing so, algorithms are designed or chosen for the frame detection, carrier frequency offset synchronization, and joint fine‐time and phase‐offset estimation by exploiting the spike‐like property of the physical layer convergence protocol preamble and the frame structure in the WBAN system. The performance of the WBAN synchronization receiver is verified by computer simulation. Copyright © 2015 John Wiley & Sons, Ltd.

Analysis of Synchronization Impairments for Cooperative Base Stations Using OFDM

Base station cooperation is envisioned as a key technology for future cellular networks, as it has the potential to eliminate intercell interference and to enhance spectral efficiency. To date, there is still lack of understanding of how imperfect carrier and sampling frequency synchronization between transmitters and receivers limit the potential gains and what the actual system requirements are. In this paper, OFDM signal model is established for multiuser multicellular networks, describing the joint effect of multiple carrier and sampling frequency offsets. It is shown that the impact of sampling offsets is much smaller than the impact of carrier frequency offsets. The model is extended to the downlink of base-coordinated networks and closed-form expressions are derived for the mean power of users’ self-signal, interuser, and intercarrier interference, whereas it is shown that interuser interference is the main source of degradation. The SIR is inverse to the base stations’ carrier frequency variance and to the square of time since the last precoder update, whereas it grows with the number of base stations and drops with the number of users. Through user selection, the derived SIR upper bound can be approached. Finally, system design recommendations for meeting synchronization requirements are provided.

Second-Order Statistics-Based Blind Synchronization Algorithm for Two Receive-Antenna Orthogonal STBC Systems

Blind estimation algorithms offer possibilities for improving the throughput of communications systems by reducing the overhead that would otherwise be required for the estimation of parameters needed for operations such as block timing and carrier frequency synchronization. Additionally, they are required by emerging cognitive radios to provide spectrum awareness functionality. When compared with the existing literature, in this letter we propose a blind block timing and carrier frequency synchronization algorithm applicable to orthogonal space-time block code systems. By exploiting the space-time redundancy of the received signal when two receive antennas are employed, this algorithm estimates the synchronization parameters using second-order statistics without requiring a priori knowledge of the channel coefficients or signal-to-noise ratio. Furthermore, it does not depend on accurate clock timing synchronization, which is confirmed by simulation experiments.

Joint scheme for symbol, sampling clock, and carrier frequency synchronization in PDM-CO-OFDM system beyond 100 Gb/s

We propose a joint scheme for symbol, sampling clock, and carrier frequency synchronization in a polarization division multiplexing coherent optical orthogonal frequency division multiplexing (PDM-CO-OFDM) system. Unlike other existing algorithms designed for specific impairment, the scheme can estimate and compensate for the interactional synchronization errors effectively without extra training overhead by building a compre­hensive error model. The simulation shows that symbol synchronization error and sample timing error can be corrected by channel equalizer, and the estimation ranges of sampling frequency offset and normalized carrier frequency offset are about (-2000, 2000)ppm, and (-0.04 (-3.5), 0.04 (3.5))Ghz, respectively.