Availability Using Repeaters in Microwave Transmission Networks
Abstract
There are many types of technology used in the modern era. One of them is cellular technology. This technology is often used because it is more efficient and also easy to carry because the device is small. This technology uses propagation media in the form of microwaves. Changes in the weather are vulnerable to this microwave communication, and also microwave communication conditions must be free from obstacles or lane of sight (LOS). In areas that have many plateaus, mountains, and hills, this microwave communication is less efficient because it is not LOS. Because of that, in places that have plateaus, repeaters are needed so that the value reaches availability according to standards.
Availability in this context is the percentage of time when the communication link meets the absence of significant interference which causes the communication link to work with standard signal quality. Environmental factors can affect availability, these factors can be, storms, rain, drought, fog and others, attenuation will occur because of this. Other factors such as technical will determine the level of availability, these technical factors can be like margin fade, path loss, and multipath interference. If the planning of this availability is right, these factors can be avoided, in tropical areas with high rainfall this availability gets more intensive attenuation because of heavier rain
1.Introduction
people who use the internet in the world continue to grow and increase every year. Based on a survey from DataReportal-Global Digital Institute in 2024, internet users in the world in 2024 are estimated to be around 5.35 billion people. with an estimated growth of around 1.8% each year. There have been many telecommunications technologies that have been used in various worlds such as cellular communication, satellite communication, and also using fiber optics. Air or wireless media is used by cellular communication and also satellite communication as a data exchange medium. different from fiber optic, fiber optic uses fiber cables as a medium for data exchange. However, the more modern and developing the era of technology that is more often used is cellular technology because of its efficient devices and uses. Microwaves are the air media that are also used in cellular technology. The frequency of 2 GHz - 58 GHz is the frequency used in microwave transmission, considering that some areas have highland areas, hills and mountains, this will cause the signal sent not to be Line of sight (LOS), if there are obstacles or obstacles in the line of sight (LOS) path, the microwave transmission will experience attenuation and cannot penetrate it, so this will cause reduced transmission availability, if there are no obstacles or obstacles near the line of sight (LOS) then the availability value will be large, so the greater the availability, the better, and vice versa, the smaller the availability, the worse.
during a certain time interval or during certain time conditions, Availability
is also defined as the ability of a unit that can function to be in a state to perform the required function during a specified time interval, or during a specified time interval, assuming that the necessary external resources are provided, simply availability is "Availability is the percentage value of the amount of time the network delivers service divided by the amount of time it is expected to provide service". The time in which the network does not provide service is defined as downtime
Availability is usually expressed as the percentage of the network that is up and running. Availability is a goal of 99.999%, which has long been used for marketing and is considered a desirable goal for availability in many networks, at least at the core level. 99.999% conveys the idea of 5 minutes of downtime per year. This illustrates the relationship between the percentage and minutes of downtime per year. Increasing availability from 99.99% to 99.999% would require a reduction from 52 to just 5 minutes of downtime per year.
Theoretical availability calculations are performed at the planning stage by dividing the supporting units such as hardware, software, physical connections, and power supplies. Mean Time Between Failure (MTBF) information is usually provided by the equipment manufacturer. For network components that do not have this data, such as resources
electricity, statistical data or estimates are used. Estimates of the recovery time of each component, known as Mean Time To Repair (MTTR), are also required. Availability is calculated using the formula:
\[Availability = \frac{MTBF}{MTBF+MTTR}\]
High availability is very important for network service providers. Availability statistics are often used as an attraction for customers. As network availability increases, the overall quality of the network also increases. Currently, most operators include availability guarantees in their SLAs. Therefore, improving availability is a primary goal for operators. The main causes of decreased availability of microwave links include equipment failures, propagation losses (including multipath fading, rain fading), site failures, interference, and human error. Of all these factors, propagation losses and interference are the most controllable. Therefore, methods such as repeater planning, route diversity, spatial diversity, polarization diversity, hot standby, or a combination of several techniques are applied to reduce BER to less than 10 − 6 bit/s and increase Received Signal Rate (RSL) to improve availability. In this study, we investigate the effects of Spatial Diversity and Polarization. One of the systems that is often used is a repeater system that has the advantage of the resulting capability, namely that each repeater will output a signal that is free from noise. The original signal is free from noise, which is a calculation that will later intersect between the signal to error rate and noise ratio.
2. Main factors that influence
2.1 Reflection
when electromagnetic waves that hit an object are very large when propagating and the size of the object hit compared to the wavelength when the wave propagates then it will cause reflection. Reflection occurs from the surface of the earth, buildings, walls, and others. The surface determines the shape of the reflected signal. Multipath reflection of RF signals can cause serious problems for MW such as quality degradation, or causing holes in the coverage area.
2.2 Refraction
Refraction is the bending of waves as they pass through a medium of varying density. When passing through such a medium, some waves will be reflected, while others will be bent through the medium in the other direction. Refraction can be a serious problem for long-distance communications.
2.3 Rain Fading
The performance of 15/18/23 GHz MW links with a hop length of 10-15 km is significantly affected by rain attenuation compared to shorter hop lengths of 5-8 km. Rain attenuation causes severe MW link blackouts in heavy rain areas. As the number of raindrops increases in size, they become more elongated in the horizontal direction, and therefore will reduce horizontal polarization more than vertical polarization. This also depends on the operating frequency. As the operating frequency increases, the wavelength decreases. When the operating wavelength is comparable to a water molecule, severe signal distortion will occur. So the effect of rain at 15 GHz is greater than at 6 GHz.
2.4 Multipath Fading
The refractive index of the atmosphere varies with temperature, humidity, and pressure. Variations in the refractive index will cause electromagnetic waves to change direction. Waves can travel from transmitter to receiver via more than one path. Contributions from different routes will add together in phase. Interference between them will vary between "constructive" and "destructive" causing signal levels to vary.
2.5 Interference
It is clear that nearby base stations operating on the same frequency will pose an interference threat. However, this is not the only situation in which interference will occur. No filter is perfect and power from other frequencies can cause problems. Interference from one system to another on the same frequency is known as "co-channel interference". Interference on other frequencies is known as "parallel channel interference". The amount of "parallel" channel interference depends on the quality of the filters used at both the transmitter and the receiver.
3. Parameters
3.1. Antenna Gain.
Antenna gain is used to measure the antenna's usefulness in sending the desired wave to the destination. Antenna gain explains how much energy isotropically radiated can be directed into a beam. The value of gain can be found using the following equation:
\[G = 20 \log f + 20 \log d + 10 \log \eta + 20.4\]
Information :
G is Antenna gain (dB), Ξ· is Antenna efficiency (%), d = Antenna diameter (m), f is Working frequency (GHz)
3.2. Free Space Loss
Free Space Loss is the attenuation that exists along the space between the transmitting and receiving antennas. The value of FSL can be calculated using the following equation:
\[FSL = 92.45 + 20 \log(fGHz) + 20 \log(Dkm)\]
Information :
FSL is Free Space Loss (dB), f is Frequency (GHz/Mhz), D is Distance between transmitter and receiver (km)
3.3 Effective Isotropic Radiated Power
Effective Isotropic Radiated Power is the effective value of the power emitted by the transmitting antenna. The value of EIRP is influenced by the transmitting power, loss and gain on the transmitting antenna. The EIRP value can be found using the following:
\[EIRP = PTX + Gant - LTX\]
Information :
PTx is Transmit Power (dBm), Gant is Antenna Gain (dBi), LTx is Transmitter loss (dB)
3.4. Isotropic Received Level
Isotropic Received Level is the value of the isotropic power level received by the receiving station. The value of IRL can be found using the equation:
\[IRL = EIRP - FSL\]
Information :
IRL is Isotropic Received Level (dBm), EIRP is Effective Isotropic Radiated Power (dBm), and FSL is Free Space Loss (dB)
3.5 Received Signal Level
Received Signal Level (RSL) is the power level that will be received by the decoding processing device. by the path losses on the receiving antenna side and the receiving antenna gain affect the RSL value. To find the RSL value, the equation can be used:
\[RSL = IRL - GRX - LRX\]
Information :
RSL or Received Signal Level (dBm), IRL a is Isotropic Received Level (dBm), GRx is Antenna Gain (dBi), LRX is Received Loss (dB)
3.6 Fading Margin
To overcome this fading, something is needed that can maintain the received power level above the threshold level (Rx threshold), the power reserve will be used. The power reserve is called the fading margin. The fading margin itself is the difference in the minimum signal level so that communication remains smooth with the received signal. To find the amount of fading margin, the equation can be used:
\[FM = RSL - RxTh\]
Information :
FM is Fading Margin (dB), RSL is Receive Signal Level (dBm),
Ror Rx Threshold Level (dBm)
6.7. Availability and Unavailability
Availability is a measure of system reliability. Ideally, all systems should have 100% availability. This condition is impossible to fulfill because in a system there must be a system failure in providing services. System failure in providing services is called unavailability.
4.Discussion
The availability value on the repeater does not appear due to the presence of obstacles that produce quite high diffraction loss , causing the unavailability level to reach its maximum. Based on the results of the simulation and also the design with the double back-to-back method , the availability value is 99.99086%. Meanwhile, in the double plane reflector method , the availability value increases to 99.99987%. This shows that the use of plane reflectors provides better availability performance than other methods.
From the link budget calculation , although there is a difference between the results of manual analysis and simulation, the difference is very small. Each parameter shows an increase after the addition of a repeater. Like the previous simulation results, the design with a double plane reflector still shows the highest availability value , which is 99.99999%.
The implementation of repeaters in non-line-of-sight (NLOS) networks has been proven to improve the overall reliability of the system. Compared to double back-to-back repeaters , the use of double plane reflectors provides advantages in terms of availability , although both approaches are still within the standards set by ITU-R.
Overall, the results of the microwave transmission network design and testing show that the addition of dual passive repeaters, both back-to-back and reflector types , provides significant improvements to availability and other parameters, such as Received Signal Level (RSL) and Fading Margin .
5.references
· Zein Hanni Pradana, Khoirun Ni'amah, and Solichah Larasati (2020)
Analysis of the Effect of Interference on Availability in Microwave Networks with Passive Repeaters
· Mela Januar Abriyanti, Eka Wahyudi, Muntaqo Alfin Amanaf (2020)
Microwave Transmission Network Design With Double Passive Repeater Using Pathloss 5.0
· Supriya V. Dicholkar, Vinitkumar Jayaprakash Dongre (2016)
Mustafa Emara, Miltiades C. Filippou, Ingolf Karls
EFFECT OF DIFFERENT DIVERSITY TECHNIQUES ON MICROWAVE LINKAVAILABILITY
· Mustafa Emara, Miltiades C. Filippou, Ingolf Karls
Availability and Reliability of Wireless Links in 5G Systems: A Space-Time Approach
· MS Hassan, NH Ahmad, MHF Rahman, RA Razak (2018)
Performance Evaluation of Microwave Radio Link Availability due to Rain Attenuation: A Case Study in Southeast Asia
The Story of Miftakhul Jannah, Eka Wahyudi, Muntaqo Alfin Manaf (2022)
The Effect of Using Back to Back Repeaters on Microwave Design Using Space Diversity Techniques
BIODATA
Name : Muhammad Gilang Ramadhan
NIM : 244101060050
Class : 1A
Study Program: Digital Telecommunication
Network
Department of Electrical Engineering