scholarly journals Low-Latency Short-Packet Transmission over a Large Spatial Scale

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 916
Author(s):  
Lei Huang ◽  
Xiaoyu Zhao ◽  
Wei Chen ◽  
H. Vincent Poor
Keyword(s):  
Spatial Scale ◽  
Satellite Communications ◽  
Packet Transmission ◽  
Propagation Loss ◽  
Low Latency ◽  
Long Distance ◽  
Performance Bound ◽  
Large Spatial Scale ◽  
Short Packet ◽  
Leo Satellite

Short-packet transmission has attracted considerable attention due to its potential to achieve ultralow latency in automated driving, telesurgery, the Industrial Internet of Things (IIoT), and other applications emerging in the coming era of the Six-Generation (6G) wireless networks. In 6G systems, a paradigm-shifting infrastructure is anticipated to provide seamless coverage by integrating low-Earth orbit (LEO) satellite networks, which enable long-distance wireless relaying. However, how to efficiently transmit short packets over a sizeable spatial scale remains open. In this paper, we are interested in low-latency short-packet transmissions between two distant nodes, in which neither propagation delay, nor propagation loss can be ignored. Decode-and-forward (DF) relays can be deployed to regenerate packets reliably during their delivery over a long distance, thereby reducing the signal-to-noise ratio (SNR) loss. However, they also cause decoding delay in each hop, the sum of which may become large and cannot be ignored given the stringent latency constraints. This paper presents an optimal relay deployment to minimize the error probability while meeting both the latency and transmission power constraints. Based on an asymptotic analysis, a theoretical performance bound for distant short-packet transmission is also characterized by the optimal distance–latency–reliability tradeoff, which is expected to provide insights into designing integrated LEO satellite communications in 6G.

Mark-recapture on large spatial scale reveals long distance dispersal in the Marsh Fritillary, Euphydryas aurinia

2011 ◽  
Vol 36 (4) ◽  
pp. 499-510 ◽  
Author(s):  
KAMIL ZIMMERMANN ◽  
ZDENEK FRIC ◽  
PETR JISKRA ◽  
MICHALA KOPECKOVA ◽  
PETR VLASANEK ◽  
...  
Keyword(s):  
Spatial Scale ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Mark Recapture ◽  
Large Spatial Scale ◽  
Euphydryas Aurinia ◽  
Marsh Fritillary

scholarly journals Spatial Distribution of Coffee Wilt Disease Under Roguing and Replanting Conditions: A Case Study from Kaweri Estate in Uganda

2016 ◽  
Vol 106 (11) ◽  
pp. 1291-1299 ◽  
Author(s):  
F. Pinard ◽  
S. E. Makune ◽  
P. Campagne ◽  
J. Mwangi
Keyword(s):  
Spatial Scale ◽  
Disease Progression ◽  
Spatial Scales ◽  
Disease Incidence ◽  
Wilt Disease ◽  
Long Distance ◽  
Large Spatial Scale ◽  
Aerial Dispersal ◽  
Global And Local

Based on time and spatial dynamic considerations, this study evaluates the potential role of short- and long-distance dispersal in the spread of coffee wilt disease (CWD) in a large commercial Robusta coffee estate in Uganda (Kaweri, 1,755 ha) over a 4-year period (2008 to 2012). In monthly surveys, total disease incidence, expansion of infection foci, and the occurrence of isolated infected trees were recorded and submitted to spatial analysis. Incidence was higher and disease progression faster in old coffee plantings compared with young plantings, indicating a lack of efficiency of roguing for reducing disease development in old plantings. At large spatial scale (approximately 1 km), Moran indices (both global and local) revealed the existence of clusters characterized by contrasting disease incidences. This suggested that local environmental conditions were heterogeneous or there were spatial interactions among blocks. At finer spatial scale (approximately 200 m), O-ring statistics revealed positive correlation between distant infection sites across distances as great as 60 m. Although these observations indicate the role of short-distance dispersal in foci expansion, dispersal at greater distances (>20 m) appeared to also contribute to both initiation of new foci and disease progression at coarser spatial scales. Therefore, our results suggested the role of aerial dispersal in CWD progression.

scholarly journals Secrecy analysis of short-packet transmissions in ultra-reliable and low-latency communications

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Jianhua He ◽  
Guangheng Zhao ◽  
Lu Wang ◽  
Xue Sun ◽  
Lei Yang
Keyword(s):  
Power Allocation ◽  
High Reliability ◽  
Low Latency ◽  
Artificial Noise ◽  
Secrecy Outage Probability ◽  
Secrecy Rate ◽  
Single Antenna ◽  
Error Probabilities ◽  
Short Packet ◽  
Allocation Factor

AbstractIn this paper, we investigate the secrecy performance of short-packet transmissions in ultra-reliable and low-latency communications (URLLC). We consider the scenario where a multi-antenna source communicates with a single-antenna legitimate receiver requiring ultra-high reliability and low latency, in the presence of a single-antenna eavesdropper. In order to safeguard URLLC, the source transmits the artificial noise (AN) signal together with the confidential signal to confuse the eavesdropper. We adopt a lower bound on the maximal secrecy rate as the secrecy performance metric for short-packet transmissions in URLLC, which takes the target decoding error probabilities at the legitimate receiver and the eavesdropper into account. Using this metric, we first derive a compact expression of the generalized secrecy outage probability (SOP). Then, we formally prove that the generalized SOP is a convex function with respect to the power allocation factor between the confidential signal and the AN signal. We further determine the optimal power allocation factor that minimizes the generalized SOP. The results presented in this work can be useful for designing new secure transmission schemes for URLLC.

scholarly journals Robust Digital Signal Recovery for LEO Satellite Communications Subject to High SNR Variation and Transmitter Memory Effects

IEEE Access ◽  
2021 ◽  
pp. 1-1
Author(s):  
Qingyue Chen ◽  
Yufeng Zhang ◽  
Feridoon Jalili ◽  
Zhugang Wang ◽  
Yonghui Huang ◽  
...  
Keyword(s):  
Digital Signal ◽  
Satellite Communications ◽  
Memory Effects ◽  
Signal Recovery ◽  
Leo Satellite

Prospects for the Application of the Global High-speed, Low Latency Broadband Satellite Internet in the Field of Road Transport

2021 ◽  
pp. 254-264
Author(s):  
Anatoliy Soltus ◽  
◽  
Maksym Rud ◽  
Keyword(s):  
Antenna Arrays ◽  
Communication Systems ◽  
High Speed ◽  
Electromagnetic Compatibility ◽  
Emerging Market ◽  
Satellite Communications ◽  
Road Transport ◽  
Unmanned Vehicles ◽  
Low Latency ◽  
Current State

The article examines the problems of navigation and communication with the use of satellite technologies in road transport in the context of the growth of globalization processes in the world economy and the transformations of freight transport technologies caused by a large-scale transition to transport with zero emissions and the development of unmanned vehicles. The paper discusses the principles of building a global high-speed broadband satellite Internet with low latency. Potential capabilities of technologies such as digital antenna arrays and laser communication channels used in such systems are analyzed. Also considered are the existing and potential problems, both technical with electromagnetic compatibility with existing satellite communication systems and between systems under construction or planning, and legal caused by changes in the principles of information transfer at the interstate level. The main players in the emerging market of high-speed satellite communications are considered and the parameters of the systems declared by them are described. The comparison of the current state of building satellite constellations of individual projects is carried out and the ability to implement the announced plans by individual companies is analyzed. The disadvantages that create obstacles for the introduction of high-speed satellite communications in road transport at the moment and the directions of their overcoming are highlighted. Considering the potential of satellite Internet systems, the current state of construction, as well as existing technical and legal restrictions, the introduction of reliable satellite communications will significantly speed up the transition to autonomous unmanned vehicles. In this regard, the most successful opportunities for the new communication technology will be able to realize the transport companies, which will simultaneously update the fleet of vehicles towards zero emissions and with unmanned technologies.

scholarly journals Space Is More Important than Season when Shaping Soil Microbial Communities at a Large Spatial Scale

mSystems ◽  
2020 ◽  
Vol 5 (3) ◽  
Author(s):  
Kaoping Zhang ◽  
Manuel Delgado-Baquerizo ◽  
Yong-Guan Zhu ◽  
Haiyan Chu
Keyword(s):  
Seasonal Variation ◽  
Microbial Community ◽  
Spatial Scale ◽  
Environmental Variables ◽  
Soil Microbial Communities ◽  
Spatiotemporal Variation ◽  
Relative Importance ◽  
Large Spatial Scale ◽  
Environmental Covariates ◽  
Soil Microbial

ABSTRACT The relative importance of spatial and temporal variability in shaping the distribution of soil microbial communities at a large spatial scale remains poorly understood. Here, we explored the relative importance of space versus time when predicting the distribution of soil bacterial and fungal communities across North China Plain in two contrasting seasons (summer versus winter). Although we found that microbial alpha (number of phylotypes) and beta (changes in community composition) diversities differed significantly between summer and winter, space rather than season explained more of the spatiotemporal variation of soil microbial alpha and beta diversities. Environmental covariates explained some of microbial spatiotemporal variation observed, with fast-changing environmental covariates—climate variables, soil moisture, and available nutrient—likely being the main factors that drove the seasonal variation found in bacterial and fungal beta diversities. Using random forest modeling, we further identified a group of microbial exact sequence variants (ESVs) as indicators of summer and winter seasons and for which relative abundance was associated with fast-changing environmental variables (e.g., soil moisture and dissolved organic nitrogen). Together, our empirical field study’s results suggest soil microbial seasonal variation could arise from the changes of fast-changing environmental variables, thus providing integral support to the large emerging body of snapshot studies related to microbial biogeography. IMPORTANCE Both space and time are key factors that regulate microbial community, but microbial temporal variation is often ignored at a large spatial scale. In this study, we compared spatial and seasonal effects on bacterial and fungal diversity variation across an 878-km transect and found direct evidence that space is far more important than season in regulating the soil microbial community. Partitioning the effect of season, space and environmental variables on microbial community, we further found that fast-changing environmental factors contributed to microbial temporal variation.

scholarly journals Slaves of the environment: the movement of herbivorous insects in relation to their ecology and genotype

1999 ◽  
Vol 354 (1388) ◽  
pp. 1479-1495 ◽  
Author(s):  
Hugh D. Loxdale ◽  
Gugs Lushai
Keyword(s):  
Spatial Scale ◽  
Large Population ◽  
Insect Population ◽  
Insect Species ◽  
Herbivorous Insect ◽  
Suitable Habitat ◽  
Long Distance ◽  
Flight Behaviour ◽  
Vast Number ◽  
Insect Movement

The majority of insect species do not show an innate behavioural migration, but rather populations expand into favourable new habitats or contract away from unfavourable ones by random changes of spatial scale. Over the past 50 years, the scientific fascination with dramatic long–distance and directed mass migratory events has overshadowed the more universal mode of population movement, involving much smaller stochastic displacement during the lifetime of the insects concerned. This may be limiting our understanding of insect population dynamics. In the following synthesis, we provide an overview of how herbivorous insect movement is governed by both abiotic and biotic factors, making these animals essentially ‘slaves of their environment’. No displaced insect or insect population can leave a resource patch, migrate and flourish, leaving descendants, unless suitable habitat and/or resources are reached during movement. This must have constrained insects over geological time, bringing about species–specific adaptation in behaviour and movements in relation to their environment at a micro– and macrogeographical scale. With insects that undergo long–range spatial displacements, e.g. aphids and locusts, there is presumably a selection against movement unless overruled by factors, such as density–dependent triggering, which cause certain genotypes within the population to migrate. However, for most insect species, spatial changes of scale and range expansion are much slower and may occur over a much longer time–scale, and are not innate (nor directed). Ecologists may say that all animals and plants are figuratively speaking ‘slaves of their environments’, in the sense that their distribution is defined by their ecology and genotype. But in the case of insects, a vast number must perish daily, either out at sea or over other hostile habitats, having failed to find suitable resources and/or a habitat on which to feed and reproduce. Since many are blown by the vagaries of the wind, their chances of success are serendipitous in the extreme, especially over large distances. Hence, the strategies adopted by mass migratory species (innate pre–programmed flight behaviour, large population sizes and/or fast reproduction), which improve the chances that some of these individuals will succeed. We also emphasize the dearth of knowledge in the various interactions of insect movement and their environment, and describe how molecular markers (protein and DNA) may be used to examine the details of spatial scale over which movement occurs in relation to insect ecology and genotype.

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