Study on Satellite-to-ground Laser Communications with Existence of Atmosphere

The laser beam used to establish a communication channel between satellite and ground segments has a small divergence angle and a tiny spot on the Earth's surface,which may lead to the fail of the system.So it's important to study the deflection of laser beam by the Earth's atmosphere and find a way to calibrate this error.Both theoretical analysis and real data processing method are used to obtain the mathematical model for divergence angle of laser communication beam and its correction function.Then the model has been applied to the data,which was used to describe the atmosphere state by traditional ground segments to obtain the critical elevation angle.According to the results of calculation,our conclusion will be that the correction should be done when the critical elevation happens.

Quantum communication for satellite-to-ground networks with partially entangled states

To realize practical wide-area quantum communication,a satellite-to-ground network with partially entangled states is developed in this paper.For efficiency and security reasons,the existing method of quantum communication in distributed wireless quantum networks with partially entangled states cannot be applied directly to the proposed quantum network.Based on this point,an efficient and secure quantum communication scheme with partially entangled states is presented.In our scheme,the source node performs teleportation only after an end-to-end entangled state has been established by entanglement swapping with partially entangled states.Thus,the security of quantum communication is guaranteed.The destination node recovers the transmitted quantum bit with the help of an auxiliary quantum bit and specially defined unitary matrices.Detailed calculations and simulation analyses show that the probability of successfully transferring a quantum bit in the presented scheme is high.In addition,the auxiliary quantum bit provides a heralded mechanism for successful communication.Based on the critical components that are presented in this article an efficient,secure,and practical wide-area quantum communication can be achieved.

High Capacity Data Rate System:Review of Visible Light Communications Technology

Wireless communications have become an integral part of global convergence as global connectedness has gradually become dependent on its efficient deployment.The need for"more-broadband"techniques in relation to the ever increasing growth rate of the data hungry society now necessitates novel techniques for the high-speed data transmission.While advancements have been made in this regard,the projection of having an eventual Internet of everything (IoE) deployment will result in an unimaginable transmission data rate requirement as huge data traffic will be conveyed per time within the communications network,which will require a capacity upgrade of the existing infrastructure.Visible light communications (VLCs),as an integral part of optical wireless communications (OWCs),have been reviewed in this article,having the capacity to extend the achievable data rate requirement of the wireless communications network.The technologies,techniques,and best practices have been presented alongside technology integration for the seamless high capacity wireless broadband deployment.

Design of a Multiband Patch Antenna for 5G Communication Systems

Currently, communication system requires multiband small antennas for 5G mobile applications. Driven this motivation, this paper proposes a multiband patch antenna for Wi-Fi, WiMAX and 5G applications. The proposed antenna can effectively operate at 2.4 GHz as Wi-Fi, 7.8 GHz as WiMAX and 33.5 GHz as 5G communication purposes. The proposed antenna arrays have given directional radiation patterns, very small voltage standing wave ratio, high gain (VSWR) and directivity for each aforementioned systems operating frequency. This antenna is made for multiband purpose which can be effective for not only Wi-Fi and WiMAX but also 5G applications.

Unmanned Drug Delivery Vehicle for COVID-19 Wards in Hospitals

The prime reason for proposing the work is designing and developing a low-cost guided wireless Unmanned Ground Vehicle(UGV)for use in hospitals for assistance in contactless drug delivery in COVID-19 wards.The Robot is designed as per the requirements and technical specifications required for the healthcare facility.After a detailed survey and tests of various mechanisms for steering and structure of UGV,the best mechanism preferred for steering articulated and for body structure is hexagonal as this approach provides decent performance and stability required to achieve the objective.The UGV has multiple sensors onboard,such as a Camera,GPS module,Hydrogen,and Carbon Gas sensor,Raindrop sensor,and an ultrasonic range finder on UGV for the end-user to understand the circumferential environment and status of UGV.The data and control options are displayed on any phone or computer present in the Wi-Fi zones only if the user login is validated.ESP-32 microcontroller is the prime component utilized to establish reliable wireless communication between the user and UGV.These days,the demand for robot vehicles in hospitals has increased rapidly due to pandemic outbreaks as using this makes a contactless delivery of the medicinal drug.These systems are designed specifically to assist humans in the current situation where life can be at risk for healthcare facilities.In addition,the robot vehicle is suitable for many other applications like supervision,sanitization,carrying medicines and medical equipment for delivery,delivery of food and used dishes,laundry,garbage,laboratory samples,and additional supply.

OTFSmodulation performance in a satellite-to-ground channel at sub-6-GHz and millimeter-wave bands with high mobility

Orthogonal time frequency space(OTFS)modulation has been widely considered for high-mobility scenarios.Satellite-to-ground communications have recently received much attention as a typical high-mobility scenario and face great challenges due to the high Doppler shift.To enable reliable communications and high spectral efficiency in satellite mobile communications,we evaluate OTFS modulation performance for geostationary Earth orbit and low Earth orbit satellite-to-ground channels at sub-6-GHz and millimeter-wave bands in both lineof-sight and non-line-of-sight cases.The minimum mean squared error with successive detection(MMSE-SD)is used to improve the bit error rate performance.The adaptability of OTFS and the signal detection technologies in satellite-to-ground channels are analyzed.Simulation results confirm the feasibility of applying OTFS modulation to satellite-to-ground communications with high mobility.Because full diversity in the delay-Doppler domain can be explored,different terminal movement velocities do not have a significant impact on the performance of OTFS modulation,and OTFS modulation can achieve better performance compared with classical orthogonal frequency division multiplexing in satellite-to-ground channels.It is found that MMSE-SD can improve the performance of OTFS modulation compared with an MMSE equalizer.