Tharek Abdul Rahman

A Beam Steering Radial Line Slot Array (RLSA) Antenna with Reconfigurable Operating Frequency

A beam steering radial line slot array (RLSA) antenna with reconfigurable operating frequency is proposed in this paper. The RLSA antenna is fed by an aperture coupled structure, which incorporates PIN diode switches that are integrated with the feed line. It is found that the beam steering ability and reconfigurable operating frequency are greatly influenced by the spiral and radius of feed line respectively. The activation of certain PIN diode switches configuration would then determine the beam steered angle and the frequency of operation. This novel antenna design is capable of steering its radiated beam to four different angles; 0°/360°, 90°, 180°, and 270°. Furthermore, the proposed antenna can be configured to operate from a single centre frequency, up to four operating centre frequencies concurrently, at each steered beam direction. The four frequencies are 2.3 GHz, 2.6 GHz, 2.9 GHz and 3.3 GHz. This antenna is a promising candidate to be installed for a smart antenna system, cognitive radio, radar or direction finding applications in the future.

A Comprehensive Survey of Pilot Contamination in Massive MIMO—5G System

Massive MIMO has been recognized as a promising technology to meet the demand for higher data capacity for mobile networks in 2020 and beyond. Although promising, each base station needs accurate estimation of the channel state information (CSI), either through feedback or channel reciprocity schemes in order to achieve the benefits of massive MIMO in practice. Time division duplex (TDD) has been suggested as a better mode to acquire timely CSI in massive MIMO systems. The use of non-orthogonal pilot schemes, proposed for channel estimation in multi-cell TDD networks, is considered as a major source of pilot contamination in the literature due to the limitations of coherence time. Given the importance of pilot contamination in massive MIMO systems, we provide an extensive survey on pilot contamination, and identify other possible sources of pilot contamination, which include hardware impairment and non-reciprocal transceivers. We review established theories that have analyzed the effect of pilot contamination on the performance of massive MIMO systems, particularly on achievable rates. Next, we categorize the different proposed mitigation techniques for pilot contamination using the following taxonomy: pilot-based approach and subspace-based approach. Finally, we highlight the open issues, such as training overhead, deployment scenario, computational complexity, use of channel reciprocity, and conclude with broader perspective and a look at future trends in pilot contamination in massive MIMO systems.

Intelligent Fleet Management System with Concurrent GPS & GSM Real-Time Positioning Technology

Fleet management system is a rapid growing industry. This system helps institutions to manage vehicle fleet efficiently and effectively through smart allocation of resources. In this project, an intelligent fleet management system which incorporates the power of concurrent Global Positioning System (GPS) and Global System for Mobile Communications (GSM) real-time positioning, front-end intelligent and web-based management software is proposed. In contrast to systems which depend solely on GPS positioning, the proposed system provides higher positioning accuracy and is capable to track the target at areas where GPS signals are weak or unavailable. The terminal is powered by Front-End Intelligent Technology (FEI), a comprehensive embedded technology that is equipped with necessary artificial intelligence to mimic human intelligence in decision-making for quicker response, better accuracy and less dependence on a backend server. With less dependency on the backend, large scale fleet management system can be implemented more effectively. The proposed system is successfully implemented and evaluated on twenty vehicles including buses and cars in Universiti Teknologi Malaysia (UTM). Results from the test-bed shown that user can monitor and track the real-time physical location and conditions of their vehicles via Internet or Short Message Service (SMS). The web-based fleet management software also helped the user to manage fleets more effectively.

Broadband Modified Rectangular Microstrip Patch Antenna Using Stepped Cut at Four Corners Method

In this paper, a new method that called the Stepped Cut at Four Corners is introduced to design a multi-mode/broadband modified rectangular microstrip patch antennas (MRMPAs). In order to become acquainted with the new method, the design process of a monopole broadband MRMPA suitable for multifunctional wireless communication bands is explained. The methodology of the proposed broadband MRMPA design is presented in six stages. The first stage is designing a single-mode RMPA. Subsequently, by creating a step at the corners using the proposed method a dual-mode antenna is obtained at the second stage, while the triple-mode and multi-mode antennas are designed, at the third and fourth stages respectively. Two types of broadband antennas are obtained, the stepped line and straight line antennas. By increasing the number of steps, the antennas operating bandwidth (BW), with return loss less than -lOdB, covers the frequency range from 900 MHz to 2.6 GHZ, which is suitable for GSM (900 MHz and 1.5 GHz), WiFi (2.4 GHz) and LTE (2.6 GHz) applications. In addition, the antenna prototype has been fabricated and measured in the all stages, in order to validate the simulation results, and there is a close agreement between the simulated and measured results

A Dual-Band Diamond-Shaped Antenna for RFID Application

A novel dual-band single-layer substrate and diamond-shaped antenna is presented. The proposed antenna operates in dual-band frequency at UHF band (from 902 to 920 MHz) and ISM band (from 2.4 to 2.5 GHz), which is suitable for RFID application. Antenna frequencies were controlled by the shape and size of the radiating element. The proposed prototype antenna also has acceptable performances in terms of gain, efficiency, and directional radiation pattern. The antennas gain and efficiency are 7.8 dBi and 87 %, respectively, at the lower frequency band, while the corresponding values are 9.4 dBi and 94 % at the higher band. When compared to the simulated results, the measurements show good agreement in terms of return loss and radiation pattern.

Statistical Modelling and Characterization of Experimental mm-Wave Indoor Channels for Future 5G Wireless Communication Networks.

This paper presents an experimental characterization of millimeter-wave (mm-wave) channels in the 6.5 GHz, 10.5 GHz, 15 GHz, 19 GHz, 28 GHz and 38 GHz frequency bands in an indoor corridor environment. More than 4,000 power delay profiles were measured across the bands using an omnidirectional transmitter antenna and a highly directional horn receiver antenna for both co- and cross-polarized antenna configurations. This paper develops a new path-loss model to account for the frequency attenuation with distance, which we term the frequency attenuation (FA) path-loss model and introduce a frequency-dependent attenuation factor. The large-scale path loss was characterized based on both new and well-known path-loss models. A general and less complex method is also proposed to estimate the cross-polarization discrimination (XPD) factor of close-in reference distance with the XPD (CIX) and ABG with the XPD (ABGX) path-loss models to avoid the computational complexity of minimum mean square error (MMSE) approach. Moreover, small-scale parameters such as root mean square (RMS) delay spread, mean excess (MN-EX) delay, dispersion factors and maximum excess (MAX-EX) delay parameters were used to characterize the multipath channel dispersion. Multiple statistical distributions for RMS delay spread were also investigated. The results show that our proposed models are simpler and more physically-based than other well-known models. The path-loss exponents for all studied models are smaller than that of the free-space model by values in the range of 0.1 to 1.4 for all measured frequencies. The RMS delay spread values varied between 0.2 ns and 13.8 ns, and the dispersion factor values were less than 1 for all measured frequencies. The exponential and Weibull probability distribution models best fit the RMS delay spread empirical distribution for all of the measured frequencies in all scenarios.

Spectrum occupancy at UHF TV band for cognitive radio applications

Cognitive radio (CR) is one of the promising technologies in providing dynamics of the radio spectrum. Studies have shown that the spectrum is underutilized mainly due to the current management of the spectrum. CR through opportunistic spectrum access (OSA) is expected to increase the spectrum usage especially in the TV broadcasting band which is undergoing major changes. These changes are due to the digital transition from analog to digital TV broadcasting which will allow efficient use of the spectrum. Apart from that, the success in the development of IEEE 802.22 wireless regional area network (WRAN) standard have also paved way to the reality of unlicensed devices operating in the licensed band. In this context, this paper presents the spectrum occupancy of the UHF TV band in the frequency range from 470 to 798 MHz in an outdoor environment of a suburban area in Johor Bahru, Malaysia. The measurements are analyzed and spectrum holes are identified. The obtained results demonstrate significant amount of spectrum available for deployment of cognitive radio systems and IEEE 802.22 WRAN standard in the UHF TV broadcasting band.

Time-scale domain characterization of non-WSSUS wideband channels

To account for nonstationarity, channel characterization and system design methods that employ the non-wide-sense stationary uncorrelated scattering (non-WSSUS) assumption are desirable. Furthermore, the inadequacy of the Doppler shift operator to properly account for the frequency shift in wideband channel implies that the time-frequency characterization methods that employ the Doppler shift operator are not appropriate for most wideband channels. In this article, the statistical time-scale domain characterization of the non-WSSUS wideband channel is presented. This approach employs the time scaling operator in order to account for frequency spreading, and also emphasizes on the nonstationarity of the wideband channel. The non-WSSUS statistical assumption termed local-sense stationary uncorrelated scattering (LSSUS) is presented and employed in characterizing the nonstationary property of the time-varying wideband channel. The LSSUS channel model is then parameterized to provide useful coherence and stationarity/nonstationarity parameters for optimal system design. Some application relevance of the developed model in terms of channel capacity and diversity techniques are discussed. Measurement and simulation results show that the assumption of ergodic capacity and the performance of various diversity techniques depend on the degree of channel stationarity/nonstationarity. It is shown that the quantification of this degree of stationarity through the channel parameters can provide a way of tracking channel variation and allowing for adaptive application of diversity techniques and the channel capacity.

Enabling Remote Health-Caring Utilizing IoT Concept over LTE-Femtocell Networks.

As the enterprise of the “Internet of Things” is rapidly gaining widespread acceptance, sensors are being deployed in an unrestrained manner around the world to make efficient use of this new technological evolution. A recent survey has shown that sensor deployments over the past decade have increased significantly and has predicted an upsurge in the future growth rate. In health-care services, for instance, sensors are used as a key technology to enable Internet of Things oriented health-care monitoring systems. In this paper, we have proposed a two-stage fundamental approach to facilitate the implementation of such a system. In the first stage, sensors promptly gather together the particle measurements of an android application. Then, in the second stage, the collected data are sent over a Femto-LTE network following a new scheduling technique. The proposed scheduling strategy is used to send the data according to the application’s priority. The efficiency of the proposed technique is demonstrated by comparing it with that of well-known algorithms, namely, proportional fairness and exponential proportional fairness.

An improved ITU-R rain attenuation prediction model over terrestrial microwave links in tropical region

An improved approach of predicting rain attenuation cumulative distribution (CD) over terrestrial microwave links operating in tropical regions is presented in this article. The proposed method offers a better extrapolation approach for determining the values of rain attenuation at different exceedance probability from the measured attenuation at 0.01% of the time. The experimental data consist of measured rainfall rates and rain attenuation over six geographically spread DIGI MINI-LINKs operating at 15 GHz in Malaysia. A new set of numerical coefficients was derived for improved rain attenuation CD predictions in the Malaysian tropical climate. In order to test the applicability of the proposed extrapolation method, a validation was performed using rain rate and rain attenuation measurements from five Brazilian and seven Nigerian tropical locations. When tested against measurements, the proposed method seems to provide a significant improvement over the current extrapolation method adopted by ITU-R Recommendations P.530-14, for the prediction of rain attenuation CD over tropical regions.