Hop Size Research Articles

Energy-Balanced Transmission Policies for Wireless Sensor Networks

Transmission policy, in addition to topology control, routing, and MAC protocols, can play a vital role in extending network lifetime. Existing transmission policies, however, cause an extremely unbalanced energy usage that contributes to early demise of some sensors reducing overall network's lifetime drastically. Considering cocentric rings around the sink, we decompose the transmission distance of traditional multihop scheme into two parts: ring thickness and hop size, analyze the traffic and energy usage distribution among sensors and determine how energy usage varies and critical ring shifts with hop size. Based on above observations, we propose a transmission scheme and determine the optimal ring thickness and hop size by formulating network lifetime as an optimization problem. Numerical results show substantial improvements in terms of network lifetime and energy usage distribution over existing policies. Two other variations of this policy are also presented by redefining the optimization problem considering: 1) concomitant hop size variation by sensors over lifetime along with optimal duty cycles, and 2) a distinct set of hop sizes for sensors in each ring. Both variations bring increasingly uniform energy usage with lower critical energy and further improves lifetime. A heuristic for distributed implementation of each policy is also presented.

Enhanced DV-Hop Algorithm with Reduced Hop-Size Error in Ad Hoc Networks

DV-Hop algorithm produces errors in location estimations due to inaccurate hop size. We propose a novel localization scheme based on DV-Hop to improve positioning accuracy with least error hop sizes of anchors and average hop sizes of unknowns. The least error hop size of an anchor minimizes its location error, but it may be far small or large. To cope with this inconsistent hop size, each unknown node calculates its average hop size with hop sizes from anchors. Simulation results show that the proposed algorithm outperforms the DV-Hop algorithm in location estimations.

Iterative MMSE estimation of SINR for turbo‐coded FH‐SS systems in partial‐band interference and fading channels

AbstractThe minimum mean square error (MMSE) estimate of the signal‐to‐interference‐and‐noise ratio (SINR) is derived for turbo‐coded slow frequency hopping systems in the presence of partial‐band interference and Rayleigh fading. The MMSE estimator operates without training symbols and iteratively uses the turbo decoder extrinsic information to improve the accuracy of the SINR estimate. Performance comparisons are made with a genie‐aided MAP‐based estimator and near‐optimal performance is obtained for all but impractically small hop sizes. Copyright © 2010 John Wiley & Sons, Ltd.

Effect of Single-Strand Break on Holliday Junction Migration Dynamics: A Single-Molecule Fluorescence Study

Single-strand breaks (SSBs) are the most common DNA lesions in living cells. SSBs occur three orders of magnitude more frequently than double-strand breaks. Unrepaired SSBs lead to blockage or collapse of DNA replication forks, possibly causing formation of double-strand breaks. Holliday junctions (HJ) play central role in various DNA functions including repair of lesions, replication, homologous and site-specific recombination. Branch migration, either spontaneous or protein-mediated, is among widely employed mechanisms in these functions. Therefore, elucidation of the SSB effect on spontaneous branch migration of HJs is a problem of great importance. To accomplish this task, we employed single-molecule FRET approach developed before, allowing us to follow spontaneous branch migration of one HJ at a single base pair level in real time. One SSB was incorporated in the middle of the homologous region of mobile HJ with the donor and acceptor dyes placed on its opposite arms. The data showed that branch migration does not stop at these lesions or reflects from them. Our previous results showed that branch migration is a step-wise process and one step can cover entire homology region. The analysis of the time trajectories showed that such long steps are not prevented by SSBs. Step size distributions for HJs containing SSB were obtained and such characteristics of these distributions as the mean hop size and the distributions width remain virtually the same as in the designs without a break. Lifetimes of folded states were found to be very similar to that in control, just slightly increasing around the SSB in the AT-rich design. We also studied an immobile HJ with a SSB at the junction. Its arms remain in antiparallel orientation, very similarly to our previous studies.Supported by the NSF grant PHY-0615590 (YLL).

Diversity Combining and SNR Estimation for Turbo-Coded Frequency-Hopped Spread-Spectrum in Partial-Band Interference and Fading Channels

We compare different combinations of the repetition diversity order L and code rate R for turbo-coded Frequency-Hopped Spread-Spectrum (FH/SS) communication systems in the presence of fading and partial-band Gaussian interference. For a fixed overall channel code rate R/L we show that using the lowest code rate and no repetition diversity always performs better than using a higher code rate and some repetition for both coherent and non-coherent schemes. We then propose a simple maximum-likelihood-based method for signal-to-noise-ratio (SNR) estimation in Non-Coherent Binary Frequency Shift Keying (NCBFSK) without training symbols. Except for impractically small hop sizes of 8 bits or less we obtain performance virtually equal to that of perfect SNR knowledge but with much less complexity than iterative schemes previously proposed. For the case of Coherent Binary Phase Shift Keying (CBPSK) we derive the Expectation Maximization (EM) estimate of the SNR without training symbols and iteratively feed the estimator with the extrinsic information from the turbo decoder. The performance for CBPSK is near that of perfect SNR knowledge for hop sizes of 64 bits or more. Unlike previously proposed methods for CBPSK the EM estimate of SNR does not require knowledge of the noise and interference variance, received bit energy, or the fading channel model.

Multi channel frequency hopping spread spectrum signaling using code M-ary frequency shift keying

In this paper we have proposed code M-ary frequency shift keying technique based frequency hopping (CMFSK/FH) spread spectrum signaling for multi channel. In this technique, taking one bit from each channel, we have constructed data word (called as symbol) for CMFSK system and corresponding to each state of data word, the transmitter generates a frequency, which is selected and amplified for transmission. The received signal in the receiver is tuned to each transmitted frequency and decoded for separation of channels. Here, we have developed simulation model for bit error rate (BER) performance analysis of CMFSK/FH system and compared the same with analytical results of BER. It is seen that simulation model is matched closely with analytical result. The BER performance for CMFSK/FH is better than that of existing FH system. It is also seen that the BER decreases with increase of frequency hop size.

Quantum dynamics of a single dislocation

We discuss the zero temperature motions of an edge dislocation in a quantum solid (e.g., He 4). If the dislocation has one kink (equal in length to its Burgers vector b) the kink has a creation energy U and can move along the line with a certain transfer integral t. When t and U are of comparable magnitude, two opposite kinks can form an extended bound state, with a size l. The overall shape of the dislocation in the ground state is then associated with a random walk of persistence length l (along the line) and hop sizes b. We also discuss the motions of kinks under an applied shear stress σ: the glide velocity is proportional to exp ( − σ * σ ) , where σ * is a characteristic stress, controlled by tunneling processes. To cite this article: P.-G. de Gennes, C. R. Physique 7 (2006).

POLLEN FLOW BETWEEN CONNECTED AND ISOLATED FLOWER PATCHES

Pollen flow between artificial patches of Scabiosa columbaria (Dipsacaceae), mainly pollinated by syrphids, was studied in a seminatural environment. Three linearly arranged patches of 30 heads each were used. The central patch served both as pollen donor and receptor patch (complete flowers), the other two patches served only as receptor patches (emasculated flowers and female flowers). The central patch was connected over a distance of 25m with one receptor patch by a corridor of flowers. The plant species of the corridor varied: either S. columbaria female heads, S. columbaria male heads, Origanum vulgare inflorescences or Aster multiflorus heads were used. The corridor species shared visitors with S. columbaria. The second receptor patch was not connected with the donor patch and served as a control. Syrphid species did not differ in hop size (distance between two subsequently visited heads) if the corridor consisted of S. columbaria female heads. In the Aster corridor, syrphid species made larger hops than in the Scabiosa corridor. Despite the fact that a fair amount of pollen was deposited on the female heads in the corridor, pollen flow was increased significantly in 4 out of 10 experiments if the receptor patch was connected with a corridor containing S. columbaria male or female heads. In only one experiment a significant decrease in pollen deposition in the connected patch (connected with a female S. columbaria corridor) was observed. Pollen flow was significantly reduced in 2 out of 9 experiments with Aster or Origanum as corridor species and was increased significantly only once. A significant increase of heterospecific pollen deposition was observed if the corridor species was not conspecific.

Finding shortest paths in distributed loop networks

Loop networks with hop connections offer smaller diameter, path lengths, alternative routes in paths and have better fault-tolerance. Such loop networks, known as distributed loops have potential applications in local area networks, parallel processing and multicomputer interconnection environment. The shortest path between any two nodes in a distributed loop network has been studied for specific hop sizes. Results exist for computing this in O(δ) time, where δ is the diameter of the distributed loop. But there exists no closed form for the diameter. In this paper we consider distributed loops of n nodes having hop connections and without any knowledge of diameter, obtain the shortest path in O( h g + log(h)) time, where h is the hop size and g is GCD( n, h).

Magnetoconductance anisotropy and interference effects in variable-range hopping

We investigate the magnetoconductance (MC) in the variable-range hopping regime, caused by quantum interference effects in three dimensions. We find that, in the absence of spin-orbit scattering, there is an increase in the localization length, producing a large positive MC. By contrast, with spin-orbit scattering present, there is no change in the localization length, and only a small increase in the overall tunneling amplitude as in two dimensions. Orientational effects, of the sample with respect to an external magnetic field, can be considered in three dimensions, and we find the magnetoconductance anisotropy depends critically on the number of dominant hops in the sample and the magnetic field intensity. If a single hop (or a few) dominates the conductivity of the sample, this leads to a characteristic orientational ``fingerprint'' for the MC anisotropy that could be probed experimentally. Samples probed to date, however, exhibit a conductance dominated by many hops, and thus averaging over critical hop orientations renders the bulk sample isotropic. Anisotropy appears, however, for thin films, when the length of the hop is comparable to the thickness. The hops are then restricted to align with the sample plane, leading to different MC behaviors parallel and perpendicular to it, even after averaging over many hops. We predict, on the basis of the Nguyen-Spivak-Shklovskii model, the variations of such anisotropy with both the hop size and the magnetic field strength. An orientational bias of dominant hops produced by strong electric fields is suggested as an interesting probe of anisotropy effects due to interference mechanisms in the variable-range hopping regime. \textcopyright{} 1996 The American Physical Society.

Residual minimization in a musical signal model based on a deterministic plus stochastic decomposition

Spectral modeling synthesis (SMS) is a spectrum modeling technique that models time-varying spectra as (1) a collection of sinusoids controlled through time by piecewise linear amplitude and frequency envelopes (the ‘‘deterministic’’ part), and (2) a time-varying filtered noise component (the ‘‘stochastic’’ part). This technique has proved to give general, high quality transformations for a wide variety of musical signals. As part of the analysis process of SMS the deterministic component is subtracted in the time domain from the original sound resulting into a residual signal. For a good deterministic-stochastic decomposition this residual should be free of the partials of the analyzed sound and a minimization criteria of the residual can be establish to measure the quality of the decomposition. There are many control parameters in the analysis process and their impact in the synthesized sound can be measured numerically by studying their effect on the residual. This paper will discuss the effect that parameters like size and type of analysis window, hop size, or FFT size have on the residual and analytical ways to get the best analysis for a given sound.