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Green Microwave and Satellite Communication Systems
Published in Gurjit Kaur, Akanksha Srivastava, Green Communication Technologies for Future Networks, 2023
Divya Sisodiya, Yash Bahuguna, Akanksha Srivastava, Gurjit Kaur
Uplink refers to the signal transmission from the first Earth station to the satellite via a channel. Downlink refers to the transfer of a signal from a satellite to a second ground station via a channel. The uplink frequency of first Earth station is the frequency at which it communicates with the satellite. This signal is converted into a different frequency by the satellite transponder and sent down to the second Earth station. Downlink frequency is the name given to this frequency. The same procedure is followed by the second Earth station to communicate with the first. An Earth station is where satellite communication begins. An infrastructure is being built here to send and receive signals from a satellite orbiting the Earth. The information is sent to satellites through high-frequency and high-powered signals from Earth stations.
MAC and QoS in WiMAX Mesh Networks
Published in Yan Zhang, Hsiao-Hwa Chen, Mobile Wimax, 2007
In the PMP mode, the downlink from the base station (BS) to the subscriber stations (SSs) operates on a PMP basis. Within a given frequency channel and coverage of the BS, all SSs receive the same transmission, or parts of it. The BS is the only transmitter operating in this direction. So it transmits without having to coordinate with other stations. The downlink is used for information broadcasting. In cases where the message downlink mobile application part (DL-MAP) does not explicitly indicate that a portion of the downlink subframe is for a specific SS, all SSs are able to listen to that portion. The SSs check the connection identifiers (CIDs) in the received protocol data units (PDUs) and retain only those PDUs addressed to them. SSs share the uplink to the BS on a demand basis. Depending on the class of service at the SSs, the SSs may be issued continuing rights to transmit or the transmission rights may be granted by the BS after receipt of requests from the SSs. In addition to individually addressed messages, messages may also be sent by multicast to groups of selected SSs and broadcast to all SSs. In each sector, SSs are controlled by the transmission protocol at the media access control (MAC) layer. And they are enabled to receive services tailored to the delay and bandwidth requirements of each application. This is accomplished by four types of uplink sharing schemes: un-solicited bandwidth grants, polling, and bandwidth request contention.
Aircraft Automation in the Future
Published in Charles E. Billings, Aviation Automation: The Search for A Human-Centered Approach, 2018
Thus far, I have not discussed new functions that may be enabled by data link. The high-bandwidth capability of digital data link permits it, at least in theory, to be used to downlink a considerable amount of aircraft data not now made available to ground facilities or airline operations centers. This offers the potential for error checking by ATC computers of clearances that have been uplinked, accepted, and executed by pilots, as well as the exchange of more aircraft data with the ground, as was done in United Kingdom CAA trials in 1991 (see page 213).
Performance Analysis of Radio Over Fiber System Employing Photonics Antenna and Different Modulation Schemes
Published in IETE Journal of Research, 2023
Cellular access, whether mobile or immobile, is considered as one of the most important techniques to attain better services for broadband. In this work, we present and analyze the structure of a 2.4 GHz antenna for radio over fiber system in downlink operation. Performance of system has been evaluated using different modulation schemes at a data rate of 2.5 Gbps considering a fiber length over 50 km. 16-QAM modulation scheme best suits for the transmission of data as it provides optimum performance for a given length of the fiber. The quality of the received signal has also been analyzed with variation in transmitted power, type and length of the fiber. G.652 fiber results in the achievement of highest value of Q-factor for a propagation length and transmitted power of 50 km and 0.5 dBm, respectively.
Processing time reduction for UAV optimal altitude and investigating its effect on flight time and energy consumption
Published in Journal of Information and Telecommunication, 2023
Mohammad Rezvan Marani, Seyed Masoud Mirrezaei
In this paper, we consider a moving QuadRotor UAV with velocity . The UAV, a LAP type, is deployed as a fly base station in a circular area (dense urban environment) and serves a set of downlink users. In this model, the position of the users is fixed. Figure 1 shows the system model. In Figure 1, h is the altitude of the UAV, d is the distance between the UAV and the user, r is the radius of the area covered by the UAV, and θ is the UAV's elevation angle. The values of d and θ are obtained from (1) and (2), respectively. We note that, the communication channel model between the UAV and the downlink users is of the air-to-ground (A2G) type, and only the dominant signals, i.e. the LOS and the non-Line of sight (NLOS), are considered.
DewCityGame: Dew Computing-based 5G IoT for Smart City Using Coalition Formation Game
Published in IETE Journal of Research, 2022
The uplink power consumption in sending the task from the IoT node to the dew of the machine is calculated as The uplink power consumption in sending the task from one dew to another dew of the machine is calculated as The downlink power consumption in sending the result from one dew to another dew of the machine is calculated as The downlink power consumption in sending the result from the dew of the machine to the IoT node is calculated as The propagation power consumption in sending the task between the IoT node and the dew of the machine is calculated as The propagation power consumption in sending the task between one dew to another dew of the machine is calculated as The computing power consumption for the task in the dew of the machine is calculated as The total power consumption of the DewCityGame is calculated as