Geometric searching and link distance

2005 ◽  
pp. 261-272 ◽  
Author(s):  
Gautam Das ◽  
Giri Narasimhan
Keyword(s):  
Link Distance

scholarly journals Influence of Noise-Limited Censored Path Loss on Model Fitting and Path Loss-Based Positioning

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 987
Author(s):  
Aki Karttunen ◽  
Mikko Valkama ◽  
Jukka Talvitie
Keyword(s):  
Model Fitting ◽  
Path Loss ◽  
Threshold Level ◽  
Training Data ◽  
Link Distance ◽  
Strength Based ◽  
Radio Systems ◽  
Two Phases ◽  
Wireless Standards ◽  
Influence Of Noise

Positioning is considered one of the key features in various novel industry verticals in future radio systems. Since path loss (PL) or received signal strength-based measurements are widely available in the majority of wireless standards, PL-based positioning has an important role among positioning technologies. Conventionally, PL-based positioning has two phases—fitting a PL model to training data and positioning based on the link distance estimates. However, in both phases, the maximum measurable PL is limited by measurement noise. Such immeasurable samples are called censored PL data and such noisy data are commonly neglected in both the model fitting and in the positioning phase. In the case of censored PL, the loss is known to be above a known threshold level and that information can be used in model fitting and in the positioning phase. In this paper, we examine and propose how to use censored PL data in PL model-based positioning. Additionally, we demonstrate with several simulations the potential of the proposed approach for considerable improvements in positioning accuracy (23–57%) and improved robustness against PL model fitting errors.

scholarly journals Average Channel Capacity of Amplify-and-forward MIMO/FSO Systems Over Atmospheric Turbulence Channels

2018 ◽  
Vol 8 (6) ◽  
pp. 4334
Author(s):  
Duong Huu Ai
Keyword(s):  
Atmospheric Turbulence ◽  
Channel Capacity ◽  
Multiple Input Multiple Output ◽  
Mathematical Expression ◽  
Relay Channel ◽  
Free Space Optical ◽  
Amplify And Forward ◽  
Average Channel Capacity ◽  
Link Distance ◽  
Gamma Distributions

In amplify-and-forward (AF) relay channel, when the direct link between source and destination terminals is deeply faded, the signal from the source terminal to the destination terminal propagates through the relay terminals, each of which relays a signal received from the previous terminal to the next terminal in series. This paper, we theoretically analyze the performance of multiple-input multiple-output (MIMO) AF free-space optical (FSO) systems. The AF-MIMO/FSO average channel capacity (ACC), which is expressed in terms of average spectral efficiency (ASE) is derived taking into account the atmospheric turbulence effects on the MIMO/FSO channel. They are modeled by log-normal and the gamma-gamma distributions for the cases of weak-to-strong turbulence conditions. We extract closed form mathematical expression for the evaluation of the ACC and we quantitatively discuss the influence of turbulence strength, link distance, different number of relay stations and different MIMO configurations on it.

scholarly journals BER analysis of amplify-and-forward relaying FSO systems using APD receiver over strong atmospheric turbulence channels

2019 ◽  
Vol 9 (5) ◽  
pp. 3678
Author(s):  
Duong Huu Ai ◽  
Van Loi Nguyen
Keyword(s):  
Atmospheric Turbulence ◽  
Closed Form Expression ◽  
Free Space Optical ◽  
Amplify And Forward ◽  
Transmission Distance ◽  
Link Distance ◽  
Optimal Value ◽  
Atmospheric Loss ◽  
The Impact ◽  
Relay Stations

<span lang="EN-US">In this paper, we theoretically analyze the performance of amplify-and-forward (AF) serial relaying free-space optical (FSO) systems using avalanche photodiodes (APD) and subcarrier quadrature amplitude modulation (SC-QAM) over strong atmospheric turbulence channels modelled by gamma-gamma distribution. Closed-form expression for average bit error rate (BER) of system is theoretically derived talking into account APD shot noise, thermal noise as well as the impact of atmospheric loss and turbulence. The numerical results show that using AF relay stations can extend the transmission distance and help to improve performance of FSO system significantly when compared with the direct transmission. Moreover, the selection of APD gain value is indispensable to the system performance. The proposed system could be achieved the best performance by selecting an optimal APD gain value. In addition, the optimal value of APD gain also significantly depends on various conditions, such as link distance, the number of relay stations and APD receiver noise.</span>

scholarly journals Performance Analysis of Subcarrier Multiplexed Optical Transmission System for QPSK Data

2020 ◽  
Vol 9 (2) ◽  
pp. 466-476
Keyword(s):  
Optical Transmission ◽  
Dispersion Compensation ◽  
Chromatic Dispersion ◽  
Transmission System ◽  
Laser Source ◽  
Radio Link ◽  
Link Distance ◽  
Performance Results ◽  
The Impact ◽  
Dispersion And Attenuation

This paper focuses on the impact of different parameters on the performance of the Subcarrier Multiplexed Optical Transmission System for the application on radio link via optical fiber. Performance results are evaluated for QPSK data format for ODSB and OSSB modulation of Microwave subcarriers with digital NRZ coded random data patterns. The four subsystems of QPSK modulators are at 400, 500, 600, 700 MHz subcarrier frequencies with frequency spacing of 100 MHz. The power of subcarriers is decreasing with increasing the link distance due to dispersion and attenuation. By using dispersion compensation fiber, the link distance has been enhanced from 100 km to 240 km successfully. The impact of chromatic dispersion has been reduced in OSSB by using dual-electrode MZM. The constellation diagram also confirms that the phase of the signal after traveling through the link is changing due to dispersion. The phase is the same for subcarrier 600 MHz & 700 MHz for ODSB and OSSB in QPSK SCM. The impact of linewidth and responsivity on SNR has also analyzed to evaluate the performance. It is concluded that the maximum SNR is decreasing with increase in the linewidth of laser source and increasing with the increase in responsivity of PIN diode for the same fiber length in SCM transmission.

Bit Error Rate Performance Analysis of Hybrid Subcarrier Intensity Modulation-Based FSO with Spatial Diversity in Various Weather Conditions

2019 ◽  
Vol 40 (3) ◽  
pp. 307-314 ◽  
Author(s):  
Rajat Kumar Giri ◽  
Bijayananda Patnaik
Keyword(s):  
Bit Error Rate ◽  
Error Rate ◽  
Weather Conditions ◽  
Spatial Diversity ◽  
Intensity Modulation ◽  
Free Space Optical ◽  
Diversity Techniques ◽  
Link Distance ◽  
Simulation Results ◽  
Improved Performance

Abstract In this paper, we study the performance improvement of free space optical (FSO) communication system with spatial diversity techniques employing hybrid pulse position modulation-binary phase shift keying-subcarrier intensity modulation (PPM-BPSK-SIM). The involvement of multiple photo-detectors in diversity based FSO systems offers an effective way to overcome scntillation. In this paper, we have simulated the bit error rate (BER) with respect to different parameters like average SNR, link distance at various weather conditions. The simulation results are verified in Matlab environment with the mathematical analysis. The simulation results show that higher order single input multiple output (SIMO) system achieves better BER performance and hybrid PPM-BPSK-SIM has significant improved performance than the common modulation schemes like PPM, BPSK-SIM.

LOGARITHMIC-TIME LINK PATH QUERIES IN A SIMPLE POLYGON

1995 ◽  
Vol 05 (04) ◽  
pp. 369-395 ◽  
Author(s):  
ESTHER M. ARKIN ◽  
JOSEPH S.B. MITCHELL ◽  
SUBHASH SURI
Keyword(s):  
Data Structure ◽  
Shortest Path ◽  
Simple Polygon ◽  
Additive Constant ◽  
Time And Space ◽  
Link Distance ◽  
Path Distance ◽  
Path Queries ◽  
Shortest Path Distance ◽  
Small Additive

We develop a data structure for answering link distance queries between two arbitrary points in a simple polygon. The data structure requires O(n3) time and space for its construction and answers link distance queries in O(log n) time, after which a minimum-link path can be reported in time proportional to the number of links. Here, n denotes the number of vertices of the polygon. Our result extends to link distance queries between pairs of segments or polygons. We also propose a simpler data structure for computing a link distance approximately, where the error is bounded by a small additive constant. Finally, we also present a scheme for approximating the link and the shortest path distance simultaneously.

Improved Performance Analysis of Free Space Optics Communication Link under Rain Conditions using EDFA Pre-amplifier

2018 ◽  
Vol 39 (2) ◽  
pp. 241-246 ◽  
Author(s):  
Mehtab Singh
Keyword(s):  
Performance Analysis ◽  
Free Space ◽  
Weather Conditions ◽  
Fiber Amplifier ◽  
Free Space Optics ◽  
Communication Link ◽  
Erbium Doped Fiber Amplifier ◽  
Space Optics ◽  
Link Distance ◽  
Improved Performance

AbstractFree Space Optics (FSO) also known as Optical Wireless Communication (OWC) is a communication technology in which free space/air is used as the propagation medium and optical signals are used as the information carriers. One of the most crucial factors which degrade the performance of FSO link is the signal attenuation due to different atmospheric weather conditions such as haze, rain, storm, and fog. In this paper, an improved performance analysis of a 2.5 Gbps FSO link under rain conditions has been reported using Erbium-Doped Fiber Amplifier (EDFA) as a pre-amplifier. The results show that the maximum link distance for an FSO link under rain weather conditions with acceptable performance levels (Q$$\sim6$$and BER$$ \le {10^{- 9}})$$in the absence of EDFA pre-amplifier is 1,250 m which increases to 1,675 m with the use of EDFA pre-amplifier.

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