Total Outage Probablity of a Multihop Hybrid FSO/MMW System
01 Dec 2019-pp 1-5
TL;DR: In this paper, a multihop hybrid FSO/MMW system is considered to propagate through a turbulent atmospheric medium with additional effects from pointing errors and a Rayleigh fading MMW channel and the efficiency and reliability of the combined system is studied by extracting the mathematical expression for the total outage probability, accompanied with the appropriate numerical results.
Abstract: In recent years, the FSO communication systems have attracted significant interest, mainly, due to their numerous advantages and significant improvements, that they provide and they are now expected to be a basic part of the backhaul of the upcoming 5G/5G+ networks. However, severe atmospheric and weather conditions induce limitations to their performance and reduce their effective range. Employing a hybrid FSO/MMW system and relay nodes between the transmitter and the receiver is a way to overcome these limitations. In this work, such a multihop hybrid FSO/MMW system is discussed. The pulse is considered to propagate through a turbulent atmospheric medium with additional effects from pointing errors and a Rayleigh fading MMW channel. The efficiency and reliability of the combined system is studied by extracting the mathematical expression for the total outage probability, accompanied with the appropriate numerical results.
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08 Jun 2022
TL;DR: In this paper , an outage performance comparison between a line-of-sight (LOS) THz link and a free space optical (FSO) link in terms of outage probability (OP) metric is provided for different AT and stochastic pointing error (PE) conditions.
Abstract: Over the last years the rapidly growing demands for higher wireless data transfer rates have recently motivated the research community to focus on the exploitation of higher frequency bands, such as the infrared (IR) frequency band and even more recently the terahertz (THz) frequency band (0.3-10 THz) which bridges the gap between millimeter wave (MMW) and IR frequency ranges. Nevertheless, the development of both free space optical (FSO) and THz communication links depends strongly on the randomly varying characteristics of their atmospheric channels along with the stochastic misalignment between transmitter and receiver terminals. Thus, in this work we first introduce Gamma distribution atmospheric turbulence (AT) model in the THz area. In this context, an outage performance comparison between a line of sight (LOS) THz link and a FSO link in terms of outage probability (OP) metric is provided for different AT and stochastic pointing error (PE) conditions. Additionally, the OP for the THz link due to free space path loss (FSPL) and atmospheric attenuation along with stochastic PEs is evaluated. Novel closed-form OP expressions are derived, while proper analytical results reveal and quantify the impact of the above factors. Simulation results are further included to validate our analytical results.
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05 Feb 2014
TL;DR: Measurements and capacity studies are surveyed to assess mmW technology with a focus on small cell deployments in urban environments and it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities.
Abstract: Millimeter-wave (mmW) frequencies between 30 and 300 GHz are a new frontier for cellular communication that offers the promise of orders of magnitude greater bandwidths combined with further gains via beamforming and spatial multiplexing from multielement antenna arrays. This paper surveys measurements and capacity studies to assess this technology with a focus on small cell deployments in urban environments. The conclusions are extremely encouraging; measurements in New York City at 28 and 73 GHz demonstrate that, even in an urban canyon environment, significant non-line-of-sight (NLOS) outdoor, street-level coverage is possible up to approximately 200 m from a potential low-power microcell or picocell base station. In addition, based on statistical channel models from these measurements, it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities. Cellular systems, however, will need to be significantly redesigned to fully achieve these gains. Specifically, the requirement of highly directional and adaptive transmissions, directional isolation between links, and significant possibilities of outage have strong implications on multiple access, channel structure, synchronization, and receiver design. To address these challenges, the paper discusses how various technologies including adaptive beamforming, multihop relaying, heterogeneous network architectures, and carrier aggregation can be leveraged in the mmW context.
2,452 citations
TL;DR: An up-to-date survey on FSO communication systems is presented, describing FSO channel models and transmitter/receiver structures and details on information theoretical limits of FSO channels and algorithmic-level system design research activities to approach these limits are provided.
Abstract: Optical wireless communication (OWC) refers to transmission in unguided propagation media through the use of optical carriers, i.e., visible, infrared (IR), and ultraviolet (UV) bands. In this survey, we focus on outdoor terrestrial OWC links which operate in near IR band. These are widely referred to as free space optical (FSO) communication in the literature. FSO systems are used for high rate communication between two fixed points over distances up to several kilometers. In comparison to radio-frequency (RF) counterparts, FSO links have a very high optical bandwidth available, allowing much higher data rates. They are appealing for a wide range of applications such as metropolitan area network (MAN) extension, local area network (LAN)-to-LAN connectivity, fiber back-up, backhaul for wireless cellular networks, disaster recovery, high definition TV and medical image/video transmission, wireless video surveillance/monitoring, and quantum key distribution among others. Despite the major advantages of FSO technology and variety of its application areas, its widespread use has been hampered by its rather disappointing link reliability particularly in long ranges due to atmospheric turbulence-induced fading and sensitivity to weather conditions. In the last five years or so, there has been a surge of interest in FSO research to address these major technical challenges. Several innovative physical layer concepts, originally introduced in the context of RF systems, such as multiple-input multiple-output communication, cooperative diversity, and adaptive transmission have been recently explored for the design of next generation FSO systems. In this paper, we present an up-to-date survey on FSO communication systems. The first part describes FSO channel models and transmitter/receiver structures. In the second part, we provide details on information theoretical limits of FSO channels and algorithmic-level system design research activities to approach these limits. Specific topics include advances in modulation, channel coding, spatial/cooperative diversity techniques, adaptive transmission, and hybrid RF/FSO systems.
1,749 citations
TL;DR: The use of ML detection in spatial diversity reception to reduce the diversity gain penalty caused by correlation between the fading at different receivers is described.
Abstract: In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of the received light signal, impairing link performance. We describe several communication techniques to mitigate turbulence-induced intensity fluctuations, i.e., signal fading. These techniques are applicable in the regime in which the receiver aperture is smaller than the correlation length of fading and the observation interval is shorter than the correlation time of fading. We assume that the receiver has no knowledge of the instantaneous fading state. When the receiver knows only the marginal statistics of the fading, a symbol-by-symbol ML detector can be used to improve detection performance. If the receiver has knowledge of the joint temporal statistics of the fading, maximum-likelihood sequence detection (MLSD) can be employed, yielding a further performance improvement, but at the cost of very high complexity. Spatial diversity reception with multiple receivers can also be used to overcome turbulence-induced fading. We describe the use of ML detection in spatial diversity reception to reduce the diversity gain penalty caused by correlation between the fading at different receivers.
1,490 citations
TL;DR: A statistical model for the optical intensity fluctuation at the receiver due to the combined effects of atmospheric turbulence and pointing errors is derived and the effect of beam width, detector size, and jitter variance explicitly is considered.
Abstract: We investigate the performance and design of free-space optical (FSO) communication links over slow fading channels from an information theory perspective. A statistical model for the optical intensity fluctuation at the receiver due to the combined effects of atmospheric turbulence and pointing errors is derived. Unlike earlier work, our model considers the effect of beam width, detector size, and jitter variance explicitly. Expressions for the outage probability are derived for a variety of atmospheric conditions. For given weather and misalignment conditions, the beam width is optimized to maximize the channel capacity subject to outage. Large gains in achievable rate are realized versus using a nominal beam width. In light fog, by optimizing the beam width, the achievable rate is increased by 80% over the nominal beam width at an outage probability of 10-5. Well-known error control codes are then applied to the channel and shown to realize much of the achievable gains.
1,205 citations
Book•
01 Mar 2001
TL;DR: Optical wave propagation in random media is discussed in this paper, where the authors present a background review of the background of optical wave propagation and its application in the field of laser communication systems.
Abstract: Optical Wave Propagation In Random Media - Background Review Optical Scintillation Modelling Theory Of Scintillation - Plane Wave Model Theory Of Scintillation - Spherical Wave Model Theory Of Scintillation - Gaussian-Beam Wave Model Aperture Averaging Optical Communication Systems Fade Statistics For Lasercom Systems Laser Radar Systems - Scintillation Of Return Waves Laser Radar Systems - Imaging Through Turbulence.
1,074 citations