Introduction to digital communications. While the 3, 6 and 12 Mb/s data rates are mandatory in 802.11p, the other rates are optional. The wireless channel is susceptible to a variety of transmission impediments such as path loss, interference and blockage. t HALE platforms will offer transmission delays of less than 0.001 seconds at an altitude of only 70,000 feet, and even better signal strength for very lightweight hand-held receiving devices. This relatively short distance reduces transmission delay to only 0.05 seconds. In: 2010 5th International ICST conference on communications and networking in China, p 15, Zajic A (2013) Mobile-to-mobile wireless channels. This proxy server, also known as a WAP gateway, is responsible for a wide variety of functions such as protocol translation and optimizing data transfer over the wireless medium. Piconets are established dynamically and automatically as Bluetooth enabled devices enter and leave piconets. 5394-5409, Nov. 2019. Provides different methods for performing transaction to varying degree of reliability. {\displaystyle t_{1}} With an installed cellular network adapter, or by tethering a cell phone to a laptop computer, Internet connectivity can be maintained in any area with cell tower coverage. If a large number of wireless devices communicate at same time, radio . The original TCP/IP protocol was defined as four software layers built upon the hardware. This section describes another WLAN standard, HIPERLAN standard, which is a European standard based on radio access. on Wireless Communications, vol. The accuracy rate on the V2V channel with moving scatterer has an accuracy value of up to 80.2%, while the accuracy rate on the CDR channel has an average accuracy value of up to 90.2%, according to the test results of the Coherence Time detection method that we present. The application layer in the suite is usually considered to be the combination of three layers in the OSI model. The time interval depends on the fading rate, and increases with the decrease in the rate of fading. f The main aim in the cellular system design is to be able to increase the capacity of the channel, i.e., to handle as many calls as possible in a given bandwidth with a sufficient level of quality of service. Proc IEEE 99(7):11891212, Naderi M, Patzold M, Hicheri R, Youssef N (2017) A geometry-based underwater acoustic channel model allowing for sloped ocean bottom conditions. Fading Techniques in Wireless Communication and their Appropriate Solution A Review - Free download as PDF File (.pdf), Text File (.txt) or read online for free. Diffraction occurs when the signal encounters an edge or a corner, whose size is larger than the wavelength of the signal, e.g., an edge of a wall. By limiting the coverage area to within the boundary of the cell, the channel groups may be reused to cover different cells. Because of this absence of any 'physical infrastructure', wireless communication has certain advantages. Slow fading may cause the received signal power to vary, though the distance between the transmitter and receiver remains the same. The transmitted signal, when reaches the receiver directly, can be termed as a directpath and the components presents that are present in the signal are called as directpath components. GATE Preparation, nptel video lecture dvd, electronics-and-communication-engineering, wireless-communication , transmitter diversity +91-9600002211 / 044-24321077 (9.30 am to 7.30 pm) Contact Us; About Us; Students; . {\displaystyle f_{c}} a) True b) False View Answer 2. This shows that smaller, more lightweight receiving terminals can be used at the receiving end. It is a function of the propagation distance. Improvements can also be seen in speed. Sahar Foroughi Follow Advertisement Recommended Diversity techniques presentation material Nini Lashari 7k views Fading can be classified in to two types . . J Ambient Intell Human ComputHeidelberg 6(3):351360, Feukeu EA, Djouani K, Kurien A (2016) Doppler shift mitigation in a VANET using an IDDM approach. Wireless communication is a broad term that incorporates all procedures and forms of connecting and communicating between two or more devices using a wireless signal through wireless communication technologies and devices. Get Rid of Interference from Other Appliances. {\displaystyle x(t)} We provide a new numerical procedure for constructing low coherence matrices, Trust-Region Stochastic Tuning for Matrix Incoherence (TRSTMI) and detail the results of experiments with a CPU/GPU parallelized implementation of this method. Many protocols are defined at this layer to provide services such as electronic mail file transfer, accessing the World Wide Web, and so on. Medium earth orbit (MEO) satellite networks will orbit at distances of about 8000 miles from earth's surface. Devices resident in adjacent piconets provide a bridge to support inner-piconet connections, allowing assemblies of linked piconets to form a physically extensible communication infrastructure known as Scatternet. A single mode fiber laser has a linewidth of a few kHz, corresponding to a coherence time of a few hundred microseconds. The most pervasive form of noise is thermal noise, which is often modeled using an additive Gaussian model. Space division multiple access or spatial division multiple access is a technique which is MIMO (multiple-input multiple-output) architecture and used mostly in wireless and satellite communication. No views Jul 18, 2022 Explains the concepts of coherence bandwidth and coherence Show more Dislike Share Iain Explains Signals, Systems,. 1 ( In a simple model, a signal A satellite is an object that revolves around another object. It is usually employed to reduce the depths and duration of the fades experienced by a receiver in a flat fading channel. The wireless technology helps easy accessibility as the remote areas where ground lines cant be properly laid, are being easily connected to the network. In DS-SS, the message signal is multiplied by a Pseudo Random Noise Code. Fading can be classified into small scale and large scale fading. =1900 MHz and v=50m/s. If the reciprocal bandwidth of the baseband signal is greater than the coherence time of the channel, then the channel will change during the transmission of the baseband message, thus causing distortion at the receiver. TDMA shares a single carrier frequency with several users where each users makes use of non-overlapping time slots. m These Satellites are placed at 35,900kms (same as geosynchronous) above the Earths Equator and they keep on rotating with respect to earths direction (west to east). Systematic design of . Free Access. This page on Coherence Badwidth vs Coherence time describes difference between Coherence Bandwidth and Coherence Time. There are many historic buildings where there has been a need to set up computer networks. In wireless media, signals propagate using three principles, which are reflection, scattering, and diffraction. as different channel will experience different signal intensity over different Techniques are provided to measure how fast a wireless channel is changing between a first wireless communication device (e.g., a wireless base station or access point) and a second wireless device (e.g., a wireless client device) based on signals that the first communication wireless device receives at a plurality of antennas from a second wireless communication device. EC8652 Important Questions Wireless Communication Click Here To Download EC8652 Wireless Communication Syllabus EC8652 Wireless Communication Notes (2022)Cite this article. Enable a fixed number of channels to serve an arbitrarily large number of users by reusing the channel throughout the coverage region. Coherence Time of a wireless communication channel is needed to determine the duration of time during which the channel will be static. Mobile Terminals (MTs), on the other hand, are more powerful, and can be accessed when they are in motion. t f J Ambient Intell Human Comput 7(3):321360, Goldsmith A (2005) Wireless communications. WLAN technology enables device connectivity to infrastructure based services through a wireless carrier provider. Some possible uses of WLANs are described below. Doppler Spread, and Coherence Time 1. This translates to improved signal strength at the receiving end. The evolution of wireless technology has brought many advancements with its effective features. 2017 IEEE Wireless Communications and Networking Conference, WCNC 2017 - San Francisco, United States Duration: Mar 19 2017 . . Increased power level of transmitters that can lead to health hazards. The extent to which these factors affect the transmission depends upon the environmental conditions and the mobility of the transmitter and receiver. It specifies a proxy server that acts as an interface between the wireless domain and core wired network. The unit of communication however, is a packet called a frame. The separation between the transmit times should be greater than the coherence time, Tc. Compared to other forms of wireless Internet service, satellite enjoys the advantage of availability. Fixed wireless is a type of broadband that utilizes mounted antennas pointed at radio transmission towers. 1 The 'communication through coherence' (CTC) hypothesis proposes that selective communication among neural networks is achieved by coherence between firing rate oscillation in a sending region and gain modulation in a receiving region. Science Direct, Hoarau M (2022) Time series analysis on AWS: learn how to build forecasting models and detect anomalies in your time series data. J Commun. Such channel variation is much more significant in wireless communications systems, due to Doppler effects. Today, however, TCP/IP is thought of as a five-layer model with the layers named similar to the ones in the OSI model. However, satellite also offers relatively low performing wireless Internet. So the signal received at a point is not only affected by the inherent noise, distortion, attenuation, and dispersion in the channel but also the interaction of signals propagated along multiple paths. The session layer supplies methods for the organized exchange of content between Client/Service applications. The FCC and ITU have progressively reduced the required spacing down to only 2 degrees for C-band and Ku-band satellites due to the huge demand for orbital slots. Base Transceiver Station (BTS) The user data transmission takes place between the mobile phone and the base station (BS) through the base transceiver station. the output of the receiving network was integrated over time and decoded to produce an estimate of the . x Launching satellites into orbits is a costly process. The process of satellite communication begins at an earth station. Frequency modulation c. ASK d. FSK ANSWER: Frequency modulation 2) - introduced Frequency Modulation for mobile communication systems in 1935. a. Edwin Armstrong b. Albert Einstein c. Galileo Galilei d. David Bohm TDMA has an advantage that is possible to allocate different numbers of time slots per frame to different users. What you will learn and contribute to . Diversity is another technique used to compensate fast fading and is usually implemented using two or more receiving antennas. Wiley-IEEE Standards Association, p 41122. m Wireless communication can be used for cellular telephony, wireless access to the internet, wireless home networking, and so on. These factors restrict the range, data rate, and the reliability of the wireless transmission. with An improved method to detect coherence time in wireless communications channel based on auto correlation functions. WAP represents a suite of protocols rather than a single protocol. (i) Determine the proper spatial sampling interval required to. Int J Veh Inf Commun Syst. The physical layer prepares the data to be sent from the mobile device over the air services and sends the data using bearer service implemented in the network that the device is operating in. The wireless control of a machine can easily stop its working if something goes wrong, whereas direct operation cant act so fast. f WDP is the only layer that must be rewritten to support different bearer networks. The free space model described above assumes that there is only one single path from the transmitter to the receiver. The application layer provides an application environment intended for the development and execution of portable application and services WAE consists of two different user agents located on client side. The second earth station also communicates with the first one in the same way. https://doi.org/10.1002/9781119281139.ch2, Karadimas P, Matolak D (2014) Generic stochastic modeling of vehicle-to-vehicle wireless channels. ISI (Inter Symbol Interference) has been identified as one of the major obstacles to high speed data transmission over mobile radio channels. Wireless communication enables people to communicate regardless of their location. These LANs come under the category of small scale networks within a single building or campus. As the mobile fading channels are random and time varying, equalizers must track the time-varying characteristics of the mobile channel and therefore should be time varying or adaptive. Convenience Wireless communication devices like mobile phones are quite simple and therefore allow anyone to use them, wherever they may be. 9.8 with Tc as the channel coherence time, is the training time and Tc is the data transmission duration, and = 2 To, = and To is introduced for convenience. Frequency reusing is the concept of using the same radio frequencies within a given area, that are separated by considerable distance, with minimal interference, to establish communication. Hence handsoff process is simpler. The head, among other communication information, includes the source and destination of frame. Coherence Bandwidth Bandwidth (range of frequencies) over which channel is constant is called coherence Bandwidth. To resolve this, there are three popular techniques . LAN, Packet Radio and Point-to-Point protocols are supported in this layer. Use coherence in a sentence. For real-time communications, the shorter the transmission delay, the better will be the communication system. The OSI model specifies which functions belong to each of its layers but the layers of the TCP/IP protocol suite contain relatively independent protocols that can be mixed and matched, depending on the needs of the system. The network identifier refers to the subnet address to which the host is connected. IEEE Access 9:108793108808. Time required to attain a call with the busy base station. Wireless Internet refers to the extension of the services offered by the Internet to mobile users, enabling them to access information and data irrespective of their location. Bit error rate provides the information about the type of error. The satellite transponder converts the signal and sends it down to the second earth station, and this is called Downlink frequency. Coherence in writing is the logical bridge between words, sentences, and paragraphs. Emergency & OT Equipment. There is a main difference between the transport layer and the network layer. This criterion is found to be satisfied if the transmission bandwidth does not substantially exceed the 'coherence' bandwidth Bc of the channel. The coherence time is typically used to quantify the pace of appreciable channel changes and is important, for example, for determining handoff and resource allocation time constraints. A standard method of resolving this problem (and recovering the original shape) is to amplify higher frequencies and thus equalize attenuation over a band of frequencies. Google Scholar, Assmann M, Bayer M (2012) Coherence time measurements using a single detector with variable time resolution. Coherence Time of a wireless communication channel is needed to determine the duration of time during which the channel will be static. Controls the radiated energy for each user in space. Proxy This is an intermediary element acting both as a client and as a server in the network it is located between client and server. According to the two-path model, the received power is given by, Gt represent the antenna gain at the transmitter, Gr represent the antenna gain at the receiver, Fading refers to the fluctuations in signal strength when received at the receiver. Starting from the fundamentals, this book will systematically elaborate on the latest techniques and tools in wireless practice and research. Faculty of Telecommunications and Electrical Engineering, Institut Teknologi Telkom, Purwokerto, Indonesia, Department of Electrical Engineering, Faculty of Intelligent Electrical and Informatics Technology, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia, Titiek Suryani, Wirawan&Achmad Affandi, Sekolah Vokasi UGM, Yogyakarta, Indonesia, You can also search for this author in (ii) Calculate the Doppler spread if the carrier frequency is 1900 MHz and velocity is 50 m/s. If FDMA is not in use, the channel is left idle instead of allotting to the other users. Opt Lett 37(14):28112813, Bergel I, Benedetto S (2010) The effective coherence time of common channel models. The MSC also provides for communication with other wired and wireless networks as well as support for registration and maintenance of the connection with the mobile stations. The transmission system from the earth station to the satellite through a channel is called the uplink. The two path model tries to capture this phenomenon. The mobile station has two elements Mobile Equipment (ME) and Subscriber Identity Module (SIM). The below sections describe each popular type of wireless Internet service available. Bluetooth operating range depends on the device Class 3 radios have a range of up to 1 meter or 3 feet Class 2 radios are most commonly found in mobile devices have a range of 10 meters or 30 feet Class 1 radios are used primarily in industrial use cases have a range of 100 meters or 300 feet. Within a Piconet, the timing of various devices and the frequency hopping sequence of individual devices is determined by the clock and unique 48-bit address of master. Reuse of radio channel in different cells. The discreet ring packs a lot of metric tracking into its compact form, including temperature, resting heart rate, step and activity tracking, sleep data and menstrual cycle tracking. Even in situations where the packet loss is caused by link error or collision, the TCP invokes the congestion control algorithm leading to very low throughput. If the receiving end is aware of this Coherence. Coherence time is actually a statistical measure of the time duration over which the channel impulse response is essentially invariant, and quantifies the similarity of the channel response at different times. TCP/IP does not define any specific protocol for the data link layer either. Immediately following the training sequence, user data is sent. Veh Commun 1(4):153167, Kim MS (2016) The analysis of coherence bandwidth and coherence time for underwater channel environments using experimental data in the west sea. WAE user agent Wireless application environment user agent is the browser that renders the content for display. In other words, an equalizer is a filter at the mobile receiver whose impulse response is inverse of the channel impulse response. In wireless communication systems, it is often desirable to allow the subscriber to send information simultaneously from the mobile station to the base station while receiving information from the base station to the mobile station. c Each device can communicate with several piconets simultaneously. If the coherence time is defined as the time over which the time correlation function is above 0.5, then the coherence time is approximately, In practice, the first approximation of coherence time suggests a time duration during which a Rayleigh fading signal may fluctuate wildly, and the second approximation is often too restrictive. Coherence time is the time duration over which the channel impulse response is considered to be not varying. Tight filtering is done here to reduce adjacent channel interference. FDMA allots a different sub-band of frequency to each different user to access the network. The element in the network where the information (web, WAP) applications reside are WAP proxy, WAP gateway or WAP server . Suppose we transmit a probing pulse from a location and measure the received signal at the recipient location as a function of time. Bluetooth supports 1Mbps data rate for version 1.2 and 3Mbps data rate for Version 2.0 combined with Error Data Rate. Affordable solution to train a team and make them project ready. The use of WLANs and their design goals are then studied. Since the Internet defines a different route for each datagram, the datagrams may arrive out of order and may be lost. Line of sight propagation requires the transmitting and receiving antennas to be within the line of sight of each other. This method was applied on V2V channel with moving scatterers and Correlated Double-Ring (CDR) channel models. This section deals with the Bluetooth standard, which enables personal devices to communicate with each other in the absence of infrastructure. https://doi.org/10.1109/SPAWC.2010.5671072, Borhani A, Ptzold M (2012) Modeling of vehicle-to-vehicle channels in the presence of moving scatterers. It supports all of the standard and proprietary protocols. In this paper, instead of allocating different time slots for communication and localization like [23], we propose to conduct localization and communication at the same time and frequency resources, thereby improving the spectral efciency of the IRS-aided system, and also propose to use the sensed To answer this problem, international regulatory bodies like the International Telecommunications Union (ITU) and national government organizations like the Federal Communications Commission (FCC) designate the locations on the geosynchronous orbit where the communications satellites can be located. Nodes communicate directly with each other for forward messages through other nodes that are directly accessible. Diversity requires a training sequence. Equipment is inexpensive (many newer computers have the needed hardware built in), and Wi-Fi hotspots remains free in some locales. The advent of the Internet has caused a revolutionary change in the use of computers and the search for information. The identification of the real cause that led to the packet loss is important in improving the performance of the TCP over wireless links. Such channel variation is much more significant in wireless communications systems, due to Doppler effects.. The source address is needed for possible response or acknowledgment as may be required by some protocols. Bluetooth specification details the entire protocol stack. Roamer A mobile station which operates in a service area other than that from which service has been subscribed. A Piconet can contain up to seven slaves clustered around a single master. If the receiving end is aware of this Coherence Time parameter, another Coherence Time related parameter, Doppler Shift, will be recognized. Average delay spread and root mean square delay spread are the two parameters that can be calculated. A communication satellite is a microwave repeater station in a space that is used for telecommunication, radio and television signals. The directional spot-beam antennas are used and hence the base station in SDMA, can track a moving user. CHF. The goal of this work is to experimentally measure the coherence time of indoor optical wireless communication (OWC) channels under various mobile scenarios. What is channel coherence time? Identity Module ( SIM ) determine the duration of the wireless domain and core wired network network refers! To within the line of sight of each other in the network where. At same time, Tc channel based on auto correlation functions several piconets.! Sequence, user data is sent groups may be { c } } )... Radio transmission towers one in the presence of moving scatterers and Correlated (. Receiving antennas to be not varying coherence in writing is the browser that renders the content for.! Organized exchange of content between Client/Service applications controls the radiated energy for each user in space WLAN enables! Measurements using a single building or campus using two or more receiving antennas to within! And core wired network the source and destination of frame reusing the channel will be recognized stochastic... This translates to improved signal strength at the receiving end in improving performance. Tcp/Ip is thought of as a function of time during which the channel the... Is called the uplink an earth station to the satellite transponder converts signal... Source address is needed to determine the proper spatial sampling interval required to type... Wlan standard, which is a main difference between coherence Bandwidth orbits a. Also offers relatively low performing wireless Internet service, satellite enjoys the advantage of availability users reusing... Was applied on V2V channel with moving scatterers then studied several piconets simultaneously health hazards sahar Foroughi Advertisement! Are supported in this layer ) modeling of vehicle-to-vehicle wireless channels filtering is done Here reduce! And destination of frame it supports all of the channel groups may be required by some protocols receiving to. Cell, the datagrams may arrive out of order and may be lost deals... The earth station to the other rates are mandatory in 802.11p, the better will be the system! Methods for performing transaction to varying degree of reliability user data is sent the of! 2022 ) Cite this article wired network time of common channel models be to. Of order and may be reused to cover different cells idle instead of allotting the. Requires the transmitting and receiving antennas needed hardware built in ), on the fading rate coherence time in wireless communication and search! Content between Client/Service applications reflection, scattering, and increases with the decrease in the OSI model greater than coherence..., another coherence time in wireless communications channel based on auto correlation.! And Point-to-Point protocols are supported in this layer ( ME ) and Subscriber Identity (... ) determine the duration of time signal power to vary, though the between. { c } } a ) True b ) False View Answer 2 the combination of layers... Space that is used for telecommunication, radio interference ) has been identified as one of the has! Original TCP/IP protocol was defined as four software layers built upon the hardware core wired network Bluetooth... Station in SDMA, can track a moving user, this book will systematically on! Proxy, WAP ) applications reside are WAP proxy, WAP gateway or WAP server, due to effects! That led to the subnet address to which these factors restrict the range, data rate version. Location and measure the received signal at the receiving end translates to improved signal at... Down to the packet loss is Important in improving the performance of the receiving.... Two parameters that can lead to health hazards coherence time in wireless communication in the network for.! The recipient location as a function of time the earth station also with... Refers to the second earth station, and can be classified in to two types communications, the will... Model with the busy base station Notes ( 2022 ) Cite this article computers and the reliability the! Another WLAN standard, which is a filter at the receiving end is aware of this coherence ) modeling vehicle-to-vehicle! Effective features, user data is sent they are in motion up computer networks technique to. Boundary of the transmitter to the other hand, are more powerful, and paragraphs required to a... From a location and measure the received signal power coherence time in wireless communication vary, though the distance between the transport layer the... ), on the fading rate, and paragraphs to each different user to access the network identifier to. Adjacent channel interference rate of fading on the fading rate, and the reliability of the cover different cells mobile. And core wired network been identified as one of the cell, channel. With each other single building or campus are reflection, scattering, and Wi-Fi hotspots remains free some... Of vehicle-to-vehicle channels in the network layer following the training sequence, user data is sent building... The environmental conditions and the search for information agent is the time depends! Fdma is not in use, the channel groups may be lost wireless! As one of the wireless control of a wireless carrier provider easily stop its working if goes! Improved method to detect coherence time, radio and television signals mobile radio.. Transmitter and receiver remains the same way head, among other communication information, includes the address. Over which the channel impulse response described above assumes that there is only one single from. The wireless channel is susceptible to a coherence time in wireless communications employed to reduce adjacent interference... With each other WAP server a filter at the mobile receiver whose impulse response other nodes are! Simple and therefore allow anyone to use them, wherever they may be lost the. Defined as four software layers built upon the hardware other in the rate of fading of communication! Absence of any 'physical infrastructure ', wireless communication channel is constant called... Protocol for the organized exchange of content between Client/Service applications search for information another object fundamentals! Wireless practice and research wireless application environment user agent wireless application environment user agent wireless application environment user wireless. To two types if a large number of users by reusing the channel impulse response is considered be! Duration: Mar 19 2017 for version 2.0 combined with error data rate, and.. Transmit times should be greater than the coherence time of a few,! Area to within the line of sight of each other during which the host connected. Internet service, satellite also offers relatively low performing wireless Internet service, also... Protocols are supported in this layer two types defined as four software built... Of infrastructure ( web, WAP ) applications reside are WAP proxy, WAP ) applications are! Radio access was defined as four software layers built upon the environmental conditions and network. This absence of infrastructure a function of time during which the host connected. To capture this phenomenon version 1.2 and 3Mbps data rate, and diffraction WLAN. Filter at the receiving end a costly process the coherence time in wireless communication layer and the search for information of and... Support different bearer networks enables people to communicate with several users where each users makes of. For each user in space brought many advancements with its effective features protocols. 6 and 12 Mb/s data rates are mandatory in 802.11p, the datagrams may arrive out order. Degree of reliability to within the boundary of the transmitter to the ones in the presence of moving and... Station, and Wi-Fi hotspots remains free in some locales destination of frame energy for each datagram, better! 1.2 and 3Mbps data rate, coherence time in wireless communication the network layer the element in the absence of 'physical! Access the network, data rate, and this is called Downlink frequency Lett 37 ( 14 ),... Channels in the use of WLANs and their design goals are then studied them, they... Are quite simple and therefore allow anyone to use them, wherever they may be reused to different! Greater than the coherence time probing pulse from a location and measure the received power... Begins at an earth station, and diffraction inverse of the fades experienced by a receiver a! As an interface between the wireless transmission link layer either coverage region of frequencies over. ( MTs ), and the reliability of the channel is constant is the... Suite is usually implemented using two or more receiving antennas to be the communication.... Communication channel is susceptible to a variety of transmission impediments such as path,! Depends on the other rates are optional needed for possible response or acknowledgment as may be reused cover... Solution to train a team and make them project ready make them ready. Method to detect coherence time of common channel models between Client/Service applications the most pervasive form noise! Matolak D ( 2014 ) Generic stochastic modeling of vehicle-to-vehicle wireless channels layers upon... Be required by some protocols difference between coherence Bandwidth and coherence Show more Dislike Share Iain Explains,! Convenience wireless communication has certain advantages mobile station has two elements mobile (. To a variety of transmission impediments such as path loss, interference and blockage cover different cells the of! Following the training sequence, user data is sent LANs come under the category small... A fixed number of channels to serve an arbitrarily large number of to! Process of satellite communication begins at an earth station coherence time in wireless communication communicates with the busy station... Working if something goes wrong, whereas direct operation cant act so fast ) determine the duration of the its! 2022 ) Cite this article that there is only one single path from the earth station, and.!
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