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In this paper, we present the baseband receiver design for IEEE 802.11ah. We study several key receiver algorithms, including coarse frequency offset estimation and coarse timing synchronization, fine frequency offset estimation, fine timing synchronization, channel estimation and MIMO equalization. For channel estimation, we propose to use decoded SIG field to improve its estimation. To further improve...
Problems with power quality in the grid have gained a lot of attention recently due to rapid increase in the amount of grid-connected power converters. The converter should produce sinusoidal currents also during abnormal conditions, such as unbalanced grid voltages. Several methods, like the delayed signal cancellation-based method (DSC), have been proposed to alleviate the detrimental effect of...
In industrial applications synchronized sensor nodes are vital for many tasks like multi parameter sampling of complex machinery behavior. The wirelessly connected nodes are usually synchronized to a base station. Therefore, frequency or period estimation of the reference clock is a key issue for all connected tasks like sampling, localization or applying energy optimized communication protocols....
Pathological high-frequency oscillations (HFOs, 200–600 Hz) observed in depth-EEG and on scalp EEG recordings are recognized to be potentially valuable biomarkers of the epileptogenic zone responsible for generating seizures. Many research studies have been dedicated to detect, classify, simulate and understand the underlying mechanisms responsible for their generation. However, broadly classifying...
Phase-locked loops (PLLs) are doubtless the most popular synchronization technique in the power converters. Almost all proposed PLL structures known in literature are inherently nonlinear and can be linearized as second order linear time invariant system. Nonlinear nature of PLLs degrades their performances, and question arises if there exist an enhanced PLL structure that would have superior performances...
In this paper, we propose a new method to compensate Doppler frequency shift for OFDM-based underwater acoustic communication systems. In order to save bandwidth, we do not use additional signal header (preamble) in each OFDM frame as proposed in many conventional approaches. Instead, the central sub-carrier is reserved for pilot transmission. This subcarrier is so-called as the carrier frequency...
Mobile ad-hoc networks (MANET) are of particular importance in military communications. With the trend towards higher throughput requirements and spectrum congestion, researchers have looked at using multi-antenna techniques to enable concurrent transmissions within a one-hop MANET. However, the acquisition overhead has been shown to be a problem when dealing with concurrent transmission in MANET...
Development of synchronized phasor measurements is one of the most significant developments in the area of power systems in recent times. A lot of research is being conducted in their applications and optimal placement as well. However, more efforts are needed to develop models of Phasor Measurement Units (PMUs) which can be directly utilized in power system simulations without the need for spending...
In interactive satellite communication systems, adaptive coding and modulation is a suitable countermeasure to mitigate the high fade dynamics of frequency ranges like the Ka-band. Consequently, receivers that support operation at low and very low SNR are required. In this paper, we present such a receiver structure dedicated for burst reception in a MF-TDMA system, as it is typically adopted in the...
Frequency hopping is used in different communications systems for its robustness by providing frequency diversity against jamming and interfering signals. Successful detection and demodulation of a frequency hopping signal is dependent on proper tuning to transmit frequency and time synchronization of the burst. The sequence of hop frequencies is generally determined by a Pseudo-Noise (PN) sequence...
The principal objective of the NATO Narrow Band Waveform (NBWF) is to achieve coalition interoperability within lower tactical levels. This paper describes a low-complexity generic receiver for the different modes of the NBWF. The NBWF burst consists of a continuous wave (CW) signal followed by a pseudo-random sequence and a data sequence modulated by continuous phase modulation (CPM). Joint coarse...
This paper presents an effective algorithm for estimating carrier frequency offset of APSK modulated signal. The data of the signal is obtained after the process of timing synchronization. The algorithm is based on the characteristic that the radiuses of the points of the constellation of APSK modulated signal are different. The value of the data is set to zero except the points with the smallest...
An embedded pilot signal structure is presented that allows simultaneous processing for time-, and frequency-selective channel variations. The pilot signal is added to an OFDM data signal in the time domain and allows for variable power allocation to the pilot. The structure of the signal shows up as a tone comb in the frequency domain which allows for doppler tracking. It is shown that exact tone...
A Grid-Voltage sensorless control strategy for LCL Grid-connected voltage source inverters is proposed. Positive and negative grid sequences used for synchronization are estimated using an observer. The control of the system is implemented with a strategy that allows the use of the proportional plus resonant regulator (PR) optimum design, regardless of the filter resonance frequency. The effectiveness...
The paper deals with developed and experimentally tested effective synchronization and power control techniques for grid-connected converter. A new FLL (Frequency Locked Loop) technique is developed that incorporates advantages of both the cascaded delayed signal cancellation and dual second order generalized integrator schemes. Experimental results are evaluated in terms of quality of the positive...
In this paper, the authors address the problem of true Cramer-Rao lower bound (CRLB) derivation for a non-data-aided (NDA) vector parameter estimation over non-constant gain flat Rayleigh fading channel (FRFC). General CRLB expressions for carrier frequency offset, carrier phase, symbol timing and signal to noise ratio (SNR) estimation are analytically developed going through the computation of the...
Provisioning of cost-effective Ethernet-based fronthaul by reusing the LAN infrastructure available in most commercial buildings is challenging predominantly in terms of the required bandwidth and synchronization. In contrast to a synchronous fronthaul, a PTP-based Ethernet network must cope with estimation noise introduced by packet delay variation (PDV) for synchronization recovery. The SYNC packet...
In this paper, we propose a simple calibration method for an ad hoc microphone array that utilizes sound emissions. Assuming that each device has a function to record sound while emitting another sound, the location, the recording time offset, and the sampling frequency mismatch of each device are estimated from the time of arrival (TOA) of the sound emitted by each device. The accurate estimation...
This paper deals with the baseband digital demodulation of bursty BPSK signals in the presence of frequency, phase and time offset in an Additive White Gaussian Noise (AWGN) impaired narrowband satellite TDMA channel. The receiver perform the tasks of acquiring synchronization in time, frequency and phase, matched filtering, BPSK demodulation and soft decision Viterbi decoding on the received baseband...
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,...
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