Khairayu Badron

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.

Rain induced attenuation studies for V-band frequency in tropical regions

Satellite links operating at frequencies above 10GHz in the tropics typically suffer severe signal degradation due to rain. The study attempts to investigate the impacts of rain on the performance of satellite-Earth links at V-band frequency. Attenuation due to rain at 38GHz had been measured for a period of 20 months in Malaysia. Studies are being conducted to quantify the rain-induced degradations. Preliminary analyses include seasonal variations and the annual cumulative distributions. Obtained results are compared with several prediction models including the ITU-R.

Cluster-Based Spectrum Sensing Scheme in Heterogeneous Network

In OFDM based Heterogeneous Networks (HetNet) deploying femtocells (HeNodeBs) causes’ inter-cell interference in uplink as well as downlink. Spectrum allocation is one of the technique as many researcher identified. However, using frequency reuse/cognitive system for dynamic spectrum reallocation is also a challenging issues. Therefore, this paper focuses on unused spectrum sensing (SS) through proposing cluster-based spectrum sensing for OFDM based two-tier HetNets. The proposed SS scheme adopted the basic model of energy detector and compared with cooperative spectrum sensing scheme. In the proposed scheme, the energy detection model is extended into multiple channel detection model. To detect spectrums from nearby macrocell (macro-eNodeB) HeNodeBs are grouped into cluster. A cluster formation algorithm is also proposed in where, cluster head (CH) and signaling node (SN) will detect implies the multi-channel SS technique. The simulation results demonstrate that the proposed scheme can improve the spectrum detection with minimum error. The performance of the proposed scheme is evaluated in Monte Carlo simulation validate the scheme performance.

Comparison of Ku-band satellite rain attenuation with ITU-R prediction models in the tropics

Rain attenuated Ku-band beacon signal from Malaysias MEASAT satellite was compared with various ITU-R prediction models in the attempt to identify the best applicable technique. The preliminary findings indicate that ITU-R P.618-5 is the best ITU-R model since it offers good estimations that almost comparable to the measured attenuation values. The use of radar-derived parameter namely the local rain height information was observed to contribute a significant improvement to the prediction models.

Determination of Ku-band specific attenuation parameters based on measurements in the tropics

Attenuation due to rain is a critical constraint in the design of Earth-space links especially at frequencies higher than 10 GHz. Rain attenuation prediction models proposed by ITU-R were reported to offer good estimation for temperate regions but a number of studies reveal that it severely underestimates the concerned signal in the tropics. The study attempted to derive new applicable specific attenuation coefficients using one-year 11 GHz satellite beacon data and rainfall rate measurements in Malaysia. The acquired outcomes are incorporated in the ITU-R procedure to assess their suitability and significance.

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.

Recognition of Metal Objects inside Wall using Antipodal Vivaldi Antenna

Received Dec 04, 2017 Revised Jan 11, 2018 Accepted Apr 15, 2018 Wireless Body Area Networks (WBANs) are fundamental technology in health care that permits the information of a patient’s essential body parameters to be gathered by the sensors. However, the safety and concealment defense of the gathered information is a key uncertain problem. A Hybrid Key Management (HKM) scheme [13] is worked based on Public Key Cryptography (PKC)-authentication scheme. This scheme uses a oneway hash function to construct a Merkle Tree. The PKC method increase the computational complexity and lacking scalability. Additionally, it increases expensive computation, communication costs and delay. To overcome this problem, Robust Security for Protected Health Information by ECC with signature Hash Function in WBAN (RSP) is proposed. The system employs hash-chain based key signature technique to achieve efficient, secure transmission from sensor to user in WBAN. Moreover, Elliptical Curve Cryptography algorithm is used to verifies the authenticate sensor. In addition, it describes the experimental results of the proposed system demonstrate the efficient data communication in a network.A Weblogs contains the history of User Navigation Pattern while user accessing the websites. The user navigation pattern can be analyzed based on the previous user navigation that is stored in weblog. The weblog comprises of various entries like IP address, status code and number of bytes transferred, categories and time stamp. The user interest can be classified based on categories and attributes and it is helpful in identifying user behavior. The aim of the research is to identifying the interested user behavior and not interested user behavior based on classification. The process of identifying user interest, it consists of Modified Span Algorithm and Personalization Algorithm based on the classification algorithm user prediction can be analyzed. The research work explores to analyze user prediction behavior based on user personalization that is captured from weblogs.Wireless Body Area Networks (WBANs) are fundamental technology in health care that permits the information of a patient’s essential body parameters to be gathered by the sensors. However, the safety and concealment defense of the gathered information is a key uncertain problem. A Hybrid Key Management (HKM) scheme [13] is worked based on Public Key Cryptography (PKC)-authentication scheme. This scheme uses a oneway hash function to construct a Merkle Tree. The PKC method increase the computational complexity and lacking scalability. Additionally, it increases expensive computation, communication costs and delay. To overcome this problem, Robust Security for Protected Health Information by ECC with signature Hash Function in WBAN (RSP) is proposed. The system employs hash-chain based key signature technique to achieve efficient, secure transmission from sensor to user in WBAN. Moreover, Elliptical Curve Cryptography algorithm is used to verifies the authenticate sensor. In addition, it describes the experimental results of the proposed system demonstrate the efficient data communication in a network.

RSSI Measurements of a GSM Signal within an Indoor Environment

Studies has suggested that the association between Received Signal Strength Indication (RSSI) and measured distance between the transmitter and receiver can be one of the key elements for ranging and localization technologies. In this study, measurements of RSSI and the distance between 1800MHz receiver and transmitter within an indoor environment were acquired, recorded and analyzed. Using the data, correlation for a select indoor environment was derived. By comparing the recorded distance values acquired at set RSSI with values calculated based on the Free Space Path Loss equation, provisional estimation of the indoor signal fading can be established. The experiment was the initial part of a three-stage work that will later entail the comparison to that of outdoor as well as clean room environments. The final result of the study hopes to achieve a simple yet improved indoor fading model experienced by mobile communication signals.

Performance analysis of rain attenuation on earth-to-satellite microwave links design in Libya

Performances of earth-to-satellite microwave links operating in Ku, Ka, and V-bands are degraded by the environment and strongly attenuated by rain. Rain attenuation is the most significant consideration and challenge to design a reliable earth-to-satellite microwave links for these frequency bands. Hence, it is essential for satellite link designer to take into account rain fade margin accurately before system implementation. Rain rate is the main measured parameter to predict of rain attenuation. Rainfall statistical data measured and recorded in Libya for the period of 30 years are collected from 5 locations. The prediction methods require one minute integration time rain intensity. Therefore, collected data were analyzed and processed to convert into one–minute rain rate cumulative distribution in Libya. The model proposed by ITU-R is used to predict and investigate rain fade based on converted 1-minute rain rate data. Rain fade predicted at two locations are used for performance analysis in terms of link spectral efficiency and throughput. V-band downlink shows that 99.99% availability is possible in all the Southern part stations in Libya at 0.29 bps/Hz spectral efficiency and 20.74 Mbps throughput when 72 MHz transponder band width is used which is not feasible in Northern part. Results of this paper will be a very useful resource to design highly reliable earth-to-satellite communication links in Libya.