Abdul Rahman Tharek

Rain fade characteristics analyses for V-band link in tropical region

A decade ago, the operating frequencies of most available satellites in the tropics were C band, S-band and Ku-band. The V-band satellite links were initially confined mainly to temperate regions. Recently however, this new service has gradually been introduced worldwide including the tropical regions. In the future, new satellites in the tropical and equatorial will also have no alternative but to operate at V-band and higher frequencies due to spectrum limitations. Therefore, it is very critical to be able to predict accurately the likely impairment to be encountered on a given link in order to plan the services economically. The predicted value of signal loss and fading are used to determine the design parameters. This paper aimed to discuss the seasonal, diurnal and possible fade mitigation technique that can be used and the challenges to be able to use V-band frequency in tropical region in the future.

A modified rain attenuation prediction model for tropical V-band satellite earth link

Radio wave propagation plays a very important part in the design and eventually dictates performance of space communication systems. Over time, the requirements of satellite communication have grown extensively where higher capacity communications systems are needed. Escalating demands of microwave and millimetre wave communications are causing frequency spectrum congestion. Hence, existing and future satellite system operators are planning to employ frequency bands well above 10 GHz. The challenge in operating at such high frequencies for communication purposes is that there exists stronger electromagnetic interaction between the radio signals and atmospheric hydrometeors. Such instances will degrade the performance of such high frequency satellite communication systems. The development of a revised model for a better-improved rain fade prediction of signal propagations in tropical region is considered very important. Researchers and engineers can employ the model to accurately plan the future high frequencies satellite services.

Investigation of rain fading on a 26GHz link in tropical climate

Links both terrestrial and Earth-space operating at bands higher than 10GHz inevitably suffer severe signal degradation due to rain fade particularly in the tropics. The study had investigated the likely impacts of rain fading on the links performance at 26GHz frequency, where rain attenuation at 26GHz had been measured for a period of over one year in Malaysia. Studies include in the attempt to quantify the rain-induced degradations. Analyses result presented consists of seasonal variations and the annual cumulative distributions. The study also includes assessment of time-diversity mitigation technique application. The technique entails a process of retransmission of signals to obtain the required signal gain for better output signal. Preliminary analyses comprise of generation of diversity gain values of specific time delays.

Analyses of rain fade countermeasure technique time diversity at 26 GHz

Measurements of 26 GHz attenuation due to rain were acquired from a microwave link set-up in Malaysia, a country in one of the most extreme weather with regard to rainfall rates. The data were analyzed with particular interest assessing the performance of Time Diversity as a conceivable fade mitigation technique in broadcast applications. The technique entails a process of retransmission of signals to obtain the required signal gain for improved output signal. An empirical relationship is proposed, enabling Time Diversity gain at mentioned frequency to be determined as a function of delay.

The Feasibility of Coexistence Between 5G and Existing Services in the IMT-2020 Candidate Bands in Malaysia

In 2015, the international telecommunication union (ITU) proposed 11 candidate millimeter-wave bands between 24 and 86 GHz for the deployment of future fifth mobile generation (5G) broadband systems. Furthermore, the ITU called for spectrum-sharing studies in these bands. Since 5G specifications are not yet defined, the utilization of radio spectrum by 5G mobile systems will assist in identifying these specifications. This paper introduces Malaysia as a case study for the deployment of 5G systems. This includes a discussion of the current status of the Malaysian telecommunication market. Then, we investigate the current services that are already deployed in the proposed bands. Our investigation shows that the fixed (F) service is the most deployed as a primary service in the candidate bands. For this reason, a preliminary spectrum-sharing study is conducted on the basis of a modified 5G spectrum-sharing model to evaluate the feasibility of coexistence between 5G and F services in the 28-GHz band. Our modified methodology can be used for spectrum-sharing studies between 5G and any other services for an initial spectrum-sharing investigation. The results show that the F service will be severely affected by the 5G system transition in the 28-GHz band, especially in the base station (BS)-to-BS sharing scenario. The best band from the perspective of current spectrum allocation for 5G systems is the 45-GHz (i.e., 45.5–47 GHz) band, since it is already reserved for mobile service for primary allocation and not utilized. This paper is carried out concurrently with current worldwide efforts investigating spectrum sharing, as requested by the ITU in agenda item 1.13 for the next world radio conference 2019.

Case study of rain attenuation at 26 GHz in tropical region (Malaysia) for terrestrial link

Millimeter wave (mm Wave) is todays breakthrough frontier for emerging wireless mobile cellular networks, wireless local area networks, personal area networks, and vehicular communications. In the near future, mm Wave products, systems, theories, and devices will come together to deliver mobile data rates thousands of times faster than todays existing cellular and WiFi networks for an example from the era of 3G towards 5G mobile communication near future. However for Tropical countries the data link reliability is effected during rain. This paper presents studies on rain attenuation at 26 GHz, which is widely used for local multipoint distribution service deployment by using the measured and prediction methods for terrestrial microwave links point to point in tropical regions. In this paper, discussion and comparison of five different reduction factor models have been presented. The essence of reduction factor is either to reduce the point rain rate to the path averaged rain rate, or to reduce the actual path length filled with the uniform point rainfall. Several models have been proposed by researchers to account for the horizontal variation of rain fall. However of ITU-R model, revised Moupfouma model, revised Silva Mello model and Lin model mostly been used for rain attenuation predictions in tropical regions. The Abdulrahman model is newly introduced has been take into consideration in this studies. The objective of these studies to identify most suitable rain attenuation prediction model for the Malaysian tropical region by comparing with actual measurement data at higher operating frequencies, such as 26 GHz which falls under Ka Band category. This study will provide useful information for researchers by understanding and good considerations in rain attenuation predictions for a terrestrial link operating frequency at 26 GHz in a tropical region. At the end of the analysis, it was found the Lin models predicts closely with the measurement value at 26 GHz with little error compare to other models.

Proposed rain fade mitigation technique for Ka-band space-Earth links in tropical climate

Satellite communication systems are swayed towards superior capacity. Millimeter wave offers a huge bandwidth allocation, involves small-sized antenna requirement and experiences less congested spectrum environment. However, rain posses a crucial intimidation to such satellite communication links especially in tropical region where the hydrometeors can severely affect the signal. Rain is the factor that typically bounds the implementation of higher frequencies for satellite communications in this region. Time diversity is seemed to be a plausible mitigation technique to countermeasure such impairments. It is envisioned that the technique will not be requiring extensive auxiliarys equipment. This paper delineates the likely improvement of a future Ka-band frequency space-Earth link using proposed time diversity (TD) technique in tropical regions. The analyses relating to the performance prediction of a satellite communication link in tropical region assimilating TD scheme are also included. The recovery strategy and its associated equations were determined reflecting the memory capacity requirement of TD. The knowledge will be integrated accordingly at the receiver with hopes to mitigate attenuation due to rain endured by the propagation link.

Rain attenuation studies on path reduction factor for tropical terrestrial link

The radio waves propagates through the earth atmosphere will be attenuated due to presence of the atmosphere particles such as water vapor , water drops and the ice particles. Meantime the atmospheric gases and rain will absorb the scatter the radio path consequently degrade the performance of the link. This paper presents comparative studies on different rain attenuation prediction methods for terrestrial microwave links point to point for tropical regions. Basically the models described in this paper include those of the ITU-R, revised Moupfouma, revised Silva Mello.el model and Lin model The objective of these studies is to show the most suitable rain attenuation prediction model for the Malaysian tropical region. Various reduction factor models are also discussed for the particular models being considered. This paper will help provide useful information for researchers to make good considerations in rain attenuation predictions for a terrestrial link operating frequency at 15GHz in a Tropical Region. Suggested model been discussed to help researchers to make good consideration in their studies.

Rain Attenuation Prediction for Higher Frequencies in Microwave Communication Using Frequency Scaling Technique

At a frequency range above 5 GHz, rainfall becomes a serious and major source of attenuation for microwave communication. Atmospheric effects play a major role in designing terrestrial or satellite-to-earth links operating at frequencies above 5 GHz. Raindrops absorb and scatter radio waves, leading to signal attenuation and reduction of the systems availability and reliability. Rain attenuation is very critical in tropical region compare to temperate region due to the geographical location. There are many techniques to predict the rain attenuation. In this research paper frequency scaling technique has been considered and discussed. In this research, three pair of frequencies, 5.8 GHz, 15 GHz and 26 GHz was compared and analyzed. All the measured data of rain attenuation for the above operating frequencies are presented. The equation of power n value for all percentage of time at certain operating frequency was identified. The results show that the proposed new power n = 1.57 closely agreed with the predicted and measured rain attenuation for all the three frequency range (5.8, 15 and 26 GHz). This data will be very useful for any researcher and mobile operators in this region for designing their microwave communication links.

Analyses of worst-month rain fade statistics for Ku-band (26GHz) in the tropics

ITU proposes that the fraction of time during which a pre-selected threshold is exceeded in the worst-month within a year is referred to as “the annual worst-month time fraction of excess”. This relates directly to situation where accumulation of outages at a specific threshold in one specific month has the worse effect on the transmission link than if compared to the accumulation that were distributed throughout the year. “Worst-month” is basically where the threshold is exceeded for the longest time. The study of the worst-month statistics is critical to the designers of telecommunication systems since there might be cases where impairment can be dominated by a single month of the year due to local weather pattern.