Design Considerations for Over-Water Microwave Radio Links - A Case Study

Arabian Gulf region with its hot, humid and prolonged summer is known to be one of the most challenging environments for radio-wave propagation. Over-the-sea microwave radio links here face degradation and unpredictability in performance due to anomalous propagation, ducting and reflective effects of large water bodies. This paper presents microwave radio link design challenges in an offshore environment and the methods implemented to overcome these challenges in the context of specific project experience in offshore field areas. A baseline design for the links was established initially which was optimized during the course of the project and during on-site implementation. Several design changes to achieve the desired performance were evaluated and implemented in the field. Required microwave link availability and performance objectives were achieved as a result of collaborative efforts between the operating company, contractor and radio manufacturer over a multi-year period. Use of quadruple diversity, optimal selection of frequencies, judicious use of ATPC (Automatic Transmit Power Control) and use of optimal signal polarisation were some of the methods used to achieve the desired link availability and performance. While these are well-known methods in radio engineering, the particular combination(s) employed to realize the desired performance objectives are identified in the paper as a lessons-learnt exercise which can be of wider application in the petroleum industry in the Gulf region. Over-water wideband microwave links are generally considered unreliable in terms of performance for utilization in process control applications involving remote shutdown and other critical operations. However, the links referred to in this paper continue to serve the field control system applications till date.

Analysis the impact of sun outage and satellite orbit at performance of the telkom 3S satellite communication system

Satellites of communication are located at altitude of thousands kilometers above the earth's surface, so the signal is transmitted by satellite to earth station is very susceptible to interference. Every March and September equinox or when the sun crosses the Earth's equator for several days, earth station occurs a naturally interference called by sun outage. At this time, satellite and the sun reach the closest distance because satellite's position is same direction with the sun. This interference makes the signal received by earth station weaken and even disappears due to temperature noise which increases drastically. Loss of signal on the downlink side caused by noise greatly affects to the performance of satellite communication system. This study aims to analyze the effect of sun outage and satellite orbit to determine sun outage period on the performance of Telkom 3S satellite communication system. The results obtained that indicate the signal quality is represented by degradation in the Carrier to Noise Ratio (C/N) from 14,777 dB to 6,0 dB, Energy bits per Noise Ratio (Eb/No) from 11,515 dB to 2,738 dB, and increase the Bit Error Rate (BER) from 8,29×10-7 to 11,08×10-3. In addition, sun outage makes lost of satellite communication traffic and affecting link availability to 99,855324%. Meanwhile, the result from satellite orbit calculation for sun outage period based on ITU-R S.1525 standard and based by satellite’s handbook. Keywords – Telkom 3S satellite, sun outage, C/N, Eb/No, BER, link availability, sun outage period.

CLOUD ATTENUATION AT Ka, Q AND W BANDS BASED ON RADIOSOUNDINGS DURING RAINY AND NON-RAINY SEASONS IN CENTRAL ANDES: A STUDY IN EL ALTO, BOLIVIA

Cloud attenuation in satellite communication systems becomes a relevant issue as the frequency increases, and thus, it has to be taken into account when link availability is being calculated. This atmospheric impairment is a variable atmospheric phenomenon whose characterization has to be done not only on a yearly-basis but also on a seasonal and monthly basis. In the present paper, cloud attenuation statistics are reported at 20 GHz, 40 GHz and 75 GHz during rainy and non-rainy seasons in El Alto, Bolivia, at 4065 m of altitude, using 3 years of radiosoundings (2016-2019). Cloud detection models have been used for the calculations, including Salonen, Salonen08, Decker and CldMod models, and results obtained are compared to those given by the global model of the ITU-R Rec. P.840. The results lead to conclude that zenith cloud attenuation during rainy season can reach maximum values between 0.15 and 0.45 dB (20 GHz), 0.55 and 1.5 dB (40 GHz), and 1.3 and 3.9 dB (75 GHz) depending on the model to be used. In comparison, during non-rainy season these values vary between 0.08 and 0.33 dB (20 GHz), 0.26 and 1.1 dB (40 GHz), and 0.62 and 2.6 dB (75 GHz). On the other hand, statistics based on CldMod model and, in a less extent, Decker model are close to the ones obtained using the ITU-R global model. These observations could open the possibility of further studies assessing the reliability of meteorological parameters in digital maps at high altitude sites, because these data are used in global propagation models.

Link Availability Prediction Based on Capacity Optimization in MANET

Mobile Ad hoc Network (MANET) is a wireless network composed of multiple wireless nodes without fixed infrastructure support, which is expected to play an important role in future commerce and military, especially in marine and aerospace communications systems. In this paper, for link failure caused by node mobility in MANET, the prediction of link availability is given according to the dynamic characteristics of the link, and transmission modes and relay nodes are selected to optimize the link capacity and reduce the interference. Simulation results show that the proposed routing metric method can select stable routing paths with less interference, and reduce routing overhead caused by node movement based on link availability analysis.

Performance analysis of FSO link under the effect of fog in Delhi region, India

Fog attenuation causes more loss than other weather conditions in a free space optics (FSO) link thus limiting the visibility distance. This work presents a detailed survey on the attenuation of the transmitted signal as a result of variation in visibility range caused by different fog conditions of the Delhi, Safdarjung region. Kim and Kruse models have been used to calculate attenuation as a result of fog conditions for three specific months (January, February and December) for seven consecutive years starting from 2013 to 2019. Received signal quality has been analyzed as a function of transmitted power, data rate, transmission range and operation wavelength. Descriptive statistical analysis of real time observed visibility data allows for the estimation of specific optical attenuation and enables in determining the link availability of the region for the complete year.

Termite inspired algorithm for traffic engineering in hybrid software defined networks

In the era of Internet of Things and 5G networks, handling real time network traffic with the required Quality of Services and optimal utilization of network resources is a challenging task. Traffic Engineering provides mechanisms to guide network traffic to improve utilization of network resources and meet requirements of the network Quality of Service (QoS). Traditional networks use IP based and Multi-Protocol Label Switching (MPLS) based Traffic Engineering mechanisms. Software Defined Networking (SDN) have characteristics useful for solving traffic scheduling and management. Currently the traditional networks are not going to be replaced fully by SDN enabled resources and hence traffic engineering solutions for Hybrid IP/SDN setups have to be explored. In this paper we propose a new Termite Inspired Optimization algorithm for dynamic path allocation and better utilization of network links using hybrid SDN setup. The proposed bioinspired algorithm based on Termite behaviour implemented in the SDN Controller supports elastic bandwidth demands from applications, by avoiding congestion, handling traffic priority and link availability. Testing in both simulated and physical test bed demonstrate the performance of the algorithm with the support of SDN. In cases of link failures, the algorithm in the SDN Controller performs failure recovery gracefully. The algorithm also performs very well in congestion avoidance. The SDN based algorithm can be implemented in the existing traditional WAN as a hybrid setup and is a less complex, better alternative to the traditional MPLS Traffic Engineering setup.

Enhancing Extensive and Remote LoRa Deployments through MEC-Powered Drone Gateways

The distribution of Internet of Things (IoT) devices in remote areas and the need for network resilience in such deployments is increasingly important in smart spaces covering scenarios, such as agriculture, forest, coast preservation, and connectivity survival against disasters. Although Low-Power Wide Area Network (LPWAN) technologies, like LoRa, support high connectivity ranges, communication paths can suffer from obstruction due to orography or buildings, and large areas are still difficult to cover with wired gateways, due to the lack of network or power infrastructure. The proposal presented herein proposes to mount LPWAN gateways in drones in order to generate airborne network segments providing enhanced connectivity to sensor nodes wherever needed. Our LoRa-drone gateways can be used either to collect data and then report them to the back-office directly, or store-carry-and-forward data until a proper communication link with the infrastructure network is available. The proposed architecture relies on Multi-Access Edge Computing (MEC) capabilities to host a virtualization platform on-board the drone, aiming at providing an intermediate processing layer that runs Virtualized Networking Functions (VNF). This way, both preprocessing or intelligent analytics can be locally performed, saving communications and memory resources. The contribution includes a system architecture that has been successfully validated through experimentation with a real test-bed and comprehensively evaluated through computer simulation. The results show significant communication improvements employing LoRa-drone gateways when compared to traditional fixed LoRa deployments in terms of link availability and covered areas, especially in vast monitored extensions, or at points with difficult access, such as rugged zones.