Time Synchronization

Small, low cost, low power and multifunctional sensor are developed as a result of improvement in microelectromechanical (MEMS) technology. Sensor's are connected via wireless medium and are used to observe various aspects of the physical world. Data sensed by these nodes needs to be ag-glomerated using data fusion, which requires clocks of nodes to be synchronized with each other. Existing approaches of clock synchronization are not designed keeping wireless sensor networks in mind. So there is a need to extend or redesign and develop a new way to synchronize the wireless sensor networks that is best suited to the specific needs of a sensor-network application. In this paper, we introduced a new approach of synchronization of nodes in WSN by enhancing the CSMA/CA protocol (slotted ALOHA). A Master Node, which is assumed to be synchronized with GPS (Global positioning System), deployed in the network. The nodes in a cluter synchronized their local clock with master node using NTP. The proposed solution features minimal energy consumption, minimal packet loss and achieve better throughput.

Structural Health Monitoring (SHM) requires precise displacement measurements to ensure infrastructure safety and longevity. Vision-based methods offer a scalable, non-contact solution but are often constrained by synchronization and real-time processing challenges. This paper presents a Robot Operating System (ROS)-based framework for real-time 3D displacement tracking that leverages software-synchronized multi-camera systems and AprilTag fiducial pose estimation. The framework makes three tightly coupled contributions: 1) an end-to-end software synchronization pipeline that integrates host clock discipline, SDK capture-time timestamp propagation, and middleware tuple formation for real-time cross-host camera alignment without specialized hardware or post-hoc alignment; 2) a scalable architecture for distributed, multi-point tracking; and 3) a modular real-time pipeline enabling parallel acquisition and extensibility. In the primary LDS-referenced displacement validation experiments, the system achieved sub-millimeter accuracy for the validated in-plane displacement components (RMSE 0.14–0.40 mm) and maintained residual timing offsets below 5 ms across the tested configurations. Additional repeated-run LDS-referenced sinusoidal tests further confirmed repeatable best-view performance across excitation frequencies, with best-view mean RMSEs ranging from 0.096 to 0.261 mm. Subsequent modal testing verified relative frequency errors under 4% across all modes and MAC values exceeding 0.85 for the first four modes. These results demonstrate that consumer-grade cameras, when combined with software-only synchronization, can provide laboratory-grade precision in compact, field-oriented setups for real-time displacement tracking.

In the prevailing open-access environment, one of the limitations for power exchanges has been voltage stability. The study of voltage stability necessitates a complete network representation. In this paper, the advantage of the dynamic behavior of generators is considered by incorporating dynamic models for generators. It has been shown dynamic models resulted in more accurate results compared to the conventional PV buses or ideal voltage source models that are used in most of the voltage stability studies. Moreover, the traditional L-index is augmented by incorporating real-time and synchronized phasor data collected from the optimally located phasor measurement units (PMU) in a wide-area measurement system (WAMS) to estimate more accurate voltage stability margins. Simulation studies carried out on IEEE 9-bus and IEEE 14-bus systems under various system conditions. It has been demonstrated that the inclusion of dynamic models and synchrophasor data from WAMS significantly improves the precision with which voltage stability analysis results are obtained.

A demand for high speed mobile wireless communications is quickly mounting. Wireless communication is the key part of research with growing demand of high data rate applications at a low cost. Orthogonal Frequency Division Multiplexing (OFDM) is a promising answer for this problem. It is a multi-carrier modulation and as well as a multiplexing technique proposed for 3G, 4G, LTE; a systems to support high data rate applications in a fading environment. There are many problems linked with the multicarrier transmission like phase variations, timing offset, large peak to average power ratio (PAPR), frequency offset etc. in which Carrier Frequency Offset (CFO) is one of the major issues. This frequency offset breaks the orthogonality among the sub-carriers and hence causes inter-carrier interference (ICI) in the OFDM symbol, which seriously degrades the overall system performance. In this thesis; we have studied and analyzed CFO upon signal to noise ratio (SNR), different techniques to estimate CFO and its effect in detailed for OFDM symbol. The estimation techniques cover both domains; time and frequency for OFDM system. The three types of CFO methods as: CP, Moose, and Classen are compared in MATLAB simulation. In Cyclic Prefix (CP) method, the CFO can be found from the phase angle of the product of CP and corresponding rear part of the OFDM symbol. In CFO estimation using Classen method, the CFO estimation range can be increased by reducing the distance between two blocks of samples for correlation. This was made possible using training symbol that are repetitive with shorter period. The principles of the eight different methods are reviewed; but among these, three methods has been compared in term of Mean Square Error (MSE) which is verified through MATLAB simulation. From simulation results, the Classen method has best performance and CP method has worst performance because of easy implementation and no loss of bandwidth efficiency. Although, Moose method has similar performance as Classen method in terms of MSE.

SUMMARY
At the time of Einstein’s invention of reciprocal special relativity (SR), Hendrick Lorentz and Henri Poincaré, two pioneers of nonreciprocal Ether/PRF relativity theory, concluded, with Einstein, that it is best to adopt isotropic light-speed at the foundation of relativity physics. On what basis did the three agree, despite Lorentz-Poincaré’s belief in the diametrically opposed Ether/PRF? In large part, it was the failure of the Michelson-Morley experiment to detect motion through the ether; failure to detect meant adoption of the simpler, more parsimonious isotropic light-speed assumption instead of the (also) non-measurable anisotropic light-speed.
        But now, 120+ years later, and 50+ years after discovery of the CM-Frame with its (averaged) 369.8 km/s dipole at the Earth’s location, Lorentz-Poincaré’s Ether/PRF may be returning. And why? Besides the CMB+dipole discovery, there is the 7.018 second time-shift (at 7.09 light-seconds forward) within the CM-Frame. This time shift results from adoption of isotropic light-speed in all inertial reference frames (IRFs), which changes cumulative time contraction/slowdown within CM-Frame theory into synchronous time within SR theory. Here the 7.018 time-shift erases or negates cumulative time contraction along the x’-axis out to 7.09 light-seconds (at v=0.99c), thereby giving time-synchrony along the x’-axis (and, by extension, in all IRFs).
        Because of the CMB discovery, and the time-shift within the CM-Frame, Lorentz-Poincaré theory can be brought into the 21st century where it should join with special relativity in a complementary relationship going forward.

We introduce the Orbital State Function (OSF), a continuous-time keyed primitive whose evaluation traces a deterministic orbit on a 3-dimensional sphere as a function of wall-clock time. An OSF is parameterized by a secret key consisting of an initial position, a rotation axis, and an angular velocity; given only the current time, its output at the next microsecond is computationally unpredictable to any adversary lacking the key, despite the function being deterministic. Built on any OSF satisfying a min-entropy condition, we construct a 3-round timesynchronized mutual authentication protocol in which each party proves knowledge of its peer's OSF by predicting the peer's current state. Wall-clock time serves as an implicit challenge, eliminating the explicit challenge-response round trip of classical schemes. Under the random oracle model for the hash commitment, we prove authentication unforgeability with adversary advantage bounded by q H • 2-λ , where λ is the OSF's output min-entropy. We instantiate the OSF concretely via quaternion rotation on a spherical shell in R 3 , parameterized by seven CSPRNG-generated floating-point values (a unit axis, an angular velocity, and a 3-dimensional initial position). A careful entropy analysis yields output min-entropy λ ≥ 159 bits, exceeding the 128-bit level of AES-128. Session data keys are derived via ephemeral Diffie-Hellman embedded in the same three rounds, providing forward secrecy. Authentication security reduces only to hash pre-image resistance and OSF key entropy; it is independent of integer factorization and discrete logarithm assumptions. Under the quantum random oracle model, the forgery advantage is bounded by O(q 2 H /2 λ) via Grover's algorithm, giving 79-bit post-quantum security for λ = 159. A deployed TypeScript implementation achieves sub-millisecond state computation and under 50 ms mutual authentication on commodity hardware.

This paper evaluates the performance of CS-RZ-ASK modulation format in optical communication by presenting the Q-factor, Bit Error Rate and noise margin at different distances. This technique suppress the power of carrier that carries no information in order to increase the efficiency in terms of power saving.

Time synchronization has always been a critical deciding factor of whether interoperating simulation models using the High Level Architecture (HLA) is achievable efficiently. In this paper, we propose a conservative time synchronization algorithm that makes use of the manufacturing process flow information (a sequence of steps production lots flow through) in the computation of the request time. This time is used by the simulation federate to issue requests to advance time to the HLA Runtime Infrastructure (RTI). The proposed algorithm monitors the simulation events that potentially trigger external timestamp messages at the exit step and j processing steps before this exit step as well as simulation events that extend the timestamp of external messages. We evaluated the performance of this algorithm using a Borderless Fab simulation model on the AutoSched AP. The experimental results show that the algorithm performs much better than a straightforward use of the RTI's time synchronization, and the further back we went in looking at the processing steps, the better the execution time that was achieved.

Classical finance theory assumes a flat, Galilean time structure in which all market participants share a universal clock and price velocity composes linearly. Four prior works-Wissner-Gross & Freer (2010), Kakushadze (2017), Romero & Zubieta-Martinez (2016), and Carvalho & Gaspar (2021)-demonstrated that special-relativistic geometry provides a mathematically consistent and empirically motivated alternative. Each of these contributions, however, remained at the level of theoretical framework: no prior work delivered an operational system that computes Lorentz factors, spacetime intervals, Christoffel symbols, or geodesic deviations from live ohlcv bar data. We close this gap. We present the Special-Relativistic Finance Manifold (srfm), the first end-to-end C++20 implementation of a special-relativistic price dynamics framework. Our contributions are fivefold: (i) an operational price-velocity β p and Lorentz-factor γ p calculator derived from open-high-low-close-volume bars; (ii) a spacetime interval classifier that partitions market regimes into timelike and spacelike sectors analogous to causal cones in special relativity; (iii) a Christoffel symbol computation on the empirical covariance manifold spanned by rolling price features; (iv) a geodesic deviation solver whose output functions as a regime-change signal; and (v) an empirical validation on Q1 2025 equity data demonstrating that timelike bars exhibit statistically distinct return variance from spacelike bars [1]. All five components are implemented with zero-panic guarantees, strong-typed interfaces, and a 1.5 : 1 test-to-production line ratio enforced by continuous integration.

Automatic speech recognition of real-live broadcast news (BN) data (Hub-4) has become a challenging research topic in recent years. This paper summarizes our key efforts to build a large vocabulary continuous speech recognition system for the heterogenous BN task without inducing undesired complexity and computational resources. These key efforts included: • automatic segmentation of the audio signal into speech utterances; • efficient one-pass trigram decoding using look-ahead techniques; • optimal log-linear interpolation of a variety of acoustic and language models using discriminative model combination (DMC); • handling short-range and weak longer-range correlations in natural speech and language by the use of phrases and of distance-language models; • improving the acoustic modeling by a robust feature extraction, channel normalization, adaptation techniques as well as automatic script selection and verification. The starting point of the system development was the Philips 64k-NAB word-internal triphone trigram system. On the speaker-independent but microphone-dependent NAB-task (transcription of read newspaper texts) we obtained a word error rate of about 10%. Now, at the conclusion of the system development, we have arrived at Philips at an DMCinterpolated phrase-based crossword-pentaphone 4-gram system. This system transcribes BN data with an overall word error rate of about 17%.

We propose a novel theoretical model of time based on the postulate that only the "absolute present" exists, containing all time labels as a quantum superposition. The distinction between past, present, and future is reduced to different values of a temporal parameter τ within a unified Hilbert space. We introduce a synchronization mechanism mediated by a single state |ψ 0 ⟩, which explains how the past can be altered without trace through manipulation of the present. The model is consistent with the Wheeler-DeWitt equation and extends presentist interpretations of quantum mechanics.

Automated parking systems rely heavily on sensor fusion to ensure precise and secure vehicle control by integrating data from vision systems and ultrasonic sensors. A major challenge in such systems is maintaining temporal alignment across these sensor domains, as clock misalignment can lead to delayed actuation and inaccurate perception. This study addresses cross-domain clock synchronization to enhance the temporal integrity of sensor fusion. Using Precision Time Protocol version 2 (PTPv2) over Automotive Ethernet, the proposed method synchronizes clocks across domains with an accuracy of ±50 μs. A real-time hardware-in-the-loop (HIL) testbed was developed, comprising ultrasonic arrays and vision systems embedded within a vehicular network. Experimental results show that PTPv2 synchronization significantly reduces fusion latency (12.5 ms vs. 38.7 ms), improves object detection accuracy (96.3% vs. 78.5%), and minimizes inter-sensor offset (mean T = 42 μs vs. 312 μs). In contrast, unsynchronized systems exhibited increased localization errors and inconsistent outputs in dynamic parking scenarios. These findings confirm that the temporal coherence required for reliable multi-sensor fusion is achieved through cross-domain synchronization via PTPv2, offering a scalable solution to enhance the responsiveness and dependability of next-generation automated parking systems.

Deploying real-time control systems software on multiprocessors requires distributing tasks on multiple processing nodes and coordinating their executions using a protocol. One such protocol is the discrete-event (DE) model of computation. In this paper, we investigate distributed discrete-event (DE) with null-message protocol (NMP) on a multicore system for real-time control software. We illustrate analytically and experimentally that even with the null-message deadlock avoidance scheme in the protocol, the system can deadlock due to inter-core message dependencies. We identify two central reasons for such deadlocks: 1) the lack of an upper-bound on packet transmission rates and processing capability, and 2) an unknown upper-bound on the communication network delay. To address these, we propose using architectural features such as timing control and real-time network-on-chips to prevent such message-dependent deadlocks. We employ these architectural techniques in conjunction with a distributed DE strategy called PTIDES for an illustrative car wash station example and later follow it with a more realistic tunnelling ball device application.

This preprint is part of a three-paper series exploring physical realization as a temporally organized process constrained by relativistic causality.

The present paper addresses classical gravitational optics. It shows that gravitational light deflection and Shapiro time delay follow directly from a temporal realization gradient,

                                                                                              a=−c2∇α,

without introducing additional fields, modified dynamics, or spacetime curvature as a primitive assumption.

By integrating the realization-induced acceleration along null trajectories, a general expression for the deflection angle is derived for arbitrary radial profiles. The empirically observed impact-parameter dependence uniquely selects an inverse-square realization gradient and reproduces the standard Eddington light-deflection coefficient. The same realization field yields the logarithmic form of the Shapiro time delay.

Small deviations from the inverse-square profile generate characteristic, scale-dependent corrections to both effects, which are tightly constrained by existing precision measurements. The results demonstrate that classical gravitational optics can be understood as a cumulative effect of temporal organization, while remaining observationally indistinguishable from general relativity in the tested regime.

The norm for A664-P7 networks used in avionic does not offer any mean of defining a common time reference to the various applications running on end-systems. In this paper, we propose an algorithm to provide such a time reference. To support the proposal, we implemented the algorithm and ran experiments with OMNeT++ to explore the robustness of the approach.

Start-to-end simulation plays an important role in designing next generation light sources. In this paper, we present recent progress in a parallel beam dynamics code, IMPACT, towards the fully start-to-end, multi-physicssimulation of a next generation X-ray FEL light source. We will discuss numerical methods and physical models used in the simulation. We will also present some preliminary simulation results of a beam transporting through photoinjector, beam delivery system, and FEL radiation. COMPUTATIONAL FRAMEWORK The computational framework used for the start-to-end simulation of next generation light sources is the IMPACT code suite. The IMPACT code is a parallel particle-incell code suite for modeling high intensity, high brightness beams in rf proton linacs, electron linacs and photoinjectors. It consists of two parallel particle-in-cell tracking codes IMPACT-Z [1, 2] and IMPACT-T [3] (the former uses longitudinal position as the independent variable and allows for efficient ...

The west Pacific warm pool is the heat engine for the globe's climate system. Its vast moisture and heat exchange profoundly impact conditions in the tropics and higher latitudes. Here, September-November sea surface temperature (SST) variability is reconstructed for the warm pool region (15°S-5°N, 110-160°E) surrounding Indonesia using annually resolved teak ring width and coral d 18 O records. The reconstruction dates from A.D. 1782-1992 and accounts for 52% of the SST variance over the most replicated period. Significant correlations are found with El Nin ˜o-Southern Oscillation (ENSO) and monsoon indices at interannual to decadal frequency bands. Negative reconstructed SST anomalies coincide with major volcanic eruptions, while other noteworthy extremes are at times synchronous with Indian and Indonesian monsoon drought, particularly during major warm ENSO episodes. While the reconstruction adds to the sparse network of proxy reconstructions available for the tropical Indo-Pacific, additional proxies are needed to clarify how warm pool dynamics have interacted with global climate in past centuries to millennia.

Abstract—Inaccurate range estimates often restrict indoor positioning systems, resulting in a more remarkable drawback when using an already-deployed IEEE 802.11 network. This is the case of the time delay based location system that this paper deals with. The main causes of these inaccuracies are multipath and non-line-of-sight (NLOS) effects. These effects can be solved to a large degree by characterizing arrival times and range estimation errors. For this reason, this paper analyzes multipath and NLOS effects involved in the round-trip time (RTT) discrete measuring process, which is conducted before each range estimate. RTT observations obtained in this process for different real indoor environments provide useful statistical information that allows to make the work extendable to other similar scenarios. Moreover, from this statistical information, the nodes in the network can estimate several parameters of the range estimates distribution while performing the location process. Th...

We show that the Einstein covariance principle provides an opportunity to generate infinitely many solutions of given covariant equation from a known one. With use of this statement we derive exact expressions for charge and current densities in a medium in an arbitrary external field. We obtain that in a homogeneous nondisipersive medium the field of a point particle differs at short-distances from the well known expression. We also demonstrate that in a linear medium second harmonic generation and optical detection become possible in the field of radially polarized radiation..

We propose Isochronous-MAC (I-MAC) using the Long-Wave Standard Time Code (so called "wave clock"), and introduce crosslayer design for a low-power wireless sensor node with I-MAC. I-MAC has a periodic wakeup time synchronized with the actual time, and thus we take the wave clock. However, a frequency of a crystal oscillator varies along with temperature, which incurs a time difference among nodes. We present a time correction algorithm to address this problem, and shorten the time difference. Thereby, the preamble length in I-MAC can be minimized, which saves communication power. For further power reduction, a lowpower crystal oscillator is also proposed, as a physical-layer design. We implemented I-MAC on an off-the-shelf sensor node to estimate the power saving, and verified that the proposed cross-layer design reduces 81% of the total power, compared to Low Power Listening.

We propose a single-chip ultralow-power sensor node processor with a synchronous media access control (MAC). It is comprised of a transceiver, i8051 micro processor, and dedicated MAC processor. The test chip occupies 3 x 3 mm 2 in a 180-nm CMOS process, including 1.38 M transistors. The power is 58.0 W under a network environment.

We propose a single-chip ultralow-power sensor node processor with a synchronous media access control (MAC). It is comprised of a transceiver, i8051 micro processor, and dedicated MAC processor. The test chip occupies 3× 3 mm 2 in a 180-nm ...

In this paper, a power management technique based on dynamic frequency scaling is proposed. The proposed technique targets digital receivers employing adaptive sampling. Such circuits over-sample the analogue input signal, in order to succeed timing synchronization. The proposed technique introduces power savings by forcing the receiver to operate only on the "correct" data for the time intervals during which synchronization is achieved. The simple architectural modifications, needed for the application of the proposed strategy, are described. As test-vehicle a number of FIR filters, which are the basic components of almost every digital receiver, are used. The experimental results prove that the application of the proposed technique introduces significant power savings, while negligibly increasing area and critical path.

This paper r e p o r t s t h e r e s u l t s of one o f the tasks of a study performed by H a r r i s Corporation f o r the Defense Communications Agency (DCA) . The task was t o evaluate the a b i l i t y o f a s e t o f timing/synchronizat i o n subsystem features t o provide a s e t o f d e s i r a b l e c h a r a c t e r i s t i c s f o r t h e e v o l v i n g Defense Comunicat i o n s Systenl (DCS) d i g i t a l communications network. The s e t of features r e l a t e t o the approaches by which timing/synchranization informat i o n could be disseminated throughout the network and the manner i n which t h i s information could be u t i l i z e d t o provide a synchronized network. These features, which could be u t i l i z e d i n a l a r g e number o f d i f f e r e n t combinatians, include mutual c o n t r o l , d i r e c t e d c o n t r o l , double ended reference l i ~i k s , independence o f c l o c k e r r o r measuremmt and c o r r e c t i o n , phase reference combining, and s e l f organizing. Some a d d i t i o n a l secondary features include smoothing f o r l i n k and nodal dropouts, unequal reference weightings, and a master i n t h e mutual contro: network. The s e t of d e s i r a b l e c h a r a c t e r i s t i c s used i n t h e e v a l u a t i o n o f the features includes b u t i s n o t l i m i t e d to, f r equency and phase accuracy, minimized propagation o f disturbances i n the network, s l i p free communicat i o n s as a normal mode o f operation, s u r v i v a b i l i t y under stressed conditions, i n t e r o p e r a b i l i t y w i t h other networks, m o n i t ~~a b i l i t y , precise time a v a i la b i l i t y , minimized overhead requirements and cost effectiveness.

This paper presents the investigation of importancefor determining the dynamic structural response of heavy lifting machines subjected to extreme external effects. A measuring system for the experimental investigation of the dynamics of heavy lifting machines is proposed.It shows the experimental testing results of carrying structures for several classes of hoisting and an export mining machine. The results refer to the most important dynamic parameters. The dynamic parameters also include the duration of transient phenomena in handling lifting structures and structural damping.A technical solution based on the measuring chain that is integrated into the mining export plant information system was developed in the research. The recommendation to choose optimal measuring equipment for this kind of measurement is given to manufacturers and users on the basis of the experience gained in the design and implementation of specifi c measuring systems. The technical specifi cation of amplifi ers and transducers that should be developed for this kind of measurement is also proposed.

Harsh deployment environments and uncertain run-time conditions create numerous challenges for postmortem time reconstruction methods. For example, motes often reboot and thus lose their clock state, considering that the majority of mote platforms lack a real-time clock. While existing time reconstruction methods for long-term data gathering networks rely on a persistent basestation for assigning global timestamps to measurements, the basestation may be unavailable due to hardware and software faults. We present Phoenix, a novel offline algorithm for reconstructing global timestamps that is robust to frequent mote reboots and does not require a persistent global time source. This independence sets Phoenix apart from the majority of time reconstruction algorithms which assume that such a source is always available. Motes in Phoenix exchange their time-related state with their neighbors, establishing a chain of transitive temporal relationships to one or more motes with references to the global time. These relationships allow Phoenix to reconstruct the measurement timeline for each mote. Results from simulations and a deployment indicate that Phoenix can achieve timing accuracy up to 6 ppm for 99% of the collected measurements. Phoenix is able to maintain this performance for periods that last for months without a persistent global time source. To achieve this level of performance for the targeted environmental monitoring application, Phoenix requires an additional space overhead of 4% and an additional duty cycle of 0.2%.

This paper investigates postmortem timestamp reconstruction in environmental monitoring networks. In the absence of a timesynchronization protocol, these networks use multiple pairs of (local, global) timestamps to retroactively estimate the motes' clock drift and offset and thus reconstruct the measurement time series. We present Sundial, a novel offline algorithm for reconstructing global timestamps that is robust to unreliable global clock sources. Sundial reconstructs timestamps by correlating annual solar patterns with measurements provided by the motes' inexpensive light sensors. The surprising ability to accurately estimate the length of day using light intensity measurements enables Sundial to be robust to arbitrary mote clock restarts. Experimental results, based on multiple environmental network deployments spanning a period of over 2.5 years, show that Sundial achieves accuracy as high as 10 parts per million (ppm), using solar radiation readings recorded at 20 minute intervals.

A hierarchical time division multiple access (HTDMA) medium access control (MAC) protocol is proposed for clustered mobile underwater acoustic networks. HTDMA consists of two TDMA scheduling protocols (i.e., TDMA1 and TDMA2) in order to accommodate mobile underwater nodes (UNs). TDMA1 is executed among surface stations (e.g., buoys) using terrestrial wireless communication in order to share mobility information obtained from UNs which move cluster to cluster. TDMA2 is executed among UNs, which send data to their surface station as a cluster head in one cluster. By sharing mobility information, a surface station can instantaneously determine the number of time slots in a TDMA2 frame up to as many as the number of UNs which is currently residing in its cluster. This can enhance delay and channel utilization performance by avoiding the occurrence of idle time slots. We analytically investigate the delay of HTDMA, and compare it with that of wellknown contention-free and contention-based MAC protocols, which are TDMA and Slotted-ALOHA, respectively. It is shown that HTDMA remarkably decreases delay, compared with TDMA and Slotted-ALOHA.