Window-based channel impulse response prediction for time-varying ultra-wideband channels

This work proposes channel impulse response (CIR) prediction for time-varying ultra-wideband (UWB) channels by exploiting the fast movement of channel taps within delay bins. Considering the sparsity of UWB channels, we introduce a window-based CIR (WB-CIR) to approximate the high temporal resolutions of UWB channels. A recursive least square (RLS) algorithm is adopted to predict the time evolution of the WB-CIR. For predicting the future WB-CIR tap of window wk, three RLS filter coefficients are computed from the observed WB-CIRs of the left wk-1, the current wk and the right wk+1 windows. The filter coefficient with the lowest RLS error is used to predict the future WB-CIR tap. To evaluate our proposed prediction method, UWB CIRs are collected through measurement campaigns in outdoor environments considering line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. Under similar computational complexity, our proposed method provides an improvement in prediction errors of approximately 80% for LOS and 63% for NLOS scenarios compared with a conventional method

Design of an adaptive CubeSat transmitter for achieving optimum signal-to-noise ratio (SNR)

CubeSat technology has opened the opportunity to conduct space-related researches at a relatively low cost. Typical approach to maintain an affordable cubeSat mission is to use a simple communication system, which is based on UHF link with fixed-transmit power and data rate. However, CubeSat in the Low Earth Orbit (LEO) does not have relative motion with the earth rotation, resulting in variable propagation path length that affects the transmission signal. A transmitter with adaptive capability to select multiple sets of data rate and radio frequency (RF) transmit power is proposed to improve and optimise the link. This paper presents the adaptive UHF transmitter design as a solution to overcome the variability of the propagation path. The transmitter output power is adjustable from 0.5W to 2W according to the mode of operations and satellite power limitations. The transmitter is designed to have four selectable modes to achieve the optimum signal-to-noise ratio (SNR) and efficient power consumption based on the link budget analysis and satellite requirement. Three prototypes are developed and tested for space-environment conditions such as the radiation test. The Total Ionizing Dose measurements are conducted in the radiation test done at Malaysia Nuclear Agency Laboratory. The results from this test have proven that the adaptive transmitter can perform its operation with estimated more than seven months in orbit. This radiation test using gamma source with 1.5krad exposure is the first one conducted for a satellite program in Malaysia

Path loss model for outdoor parking environments at 28 GHz and 38 GHz for 5G wireless networks

It has been widely speculated that the performance of the next generation Internet of Things (IoT) based wireless network should meet a transmission speed on the order of 1000 times more than current wireless networks; energy consumption on the order of 10 times less and access delay of less than 1 ns that will be provided by future 5G systems. To increase the current mobile broadband capacity in future 5G systems, the millimeter wave (mmWave) band will be used with huge amounts of bandwidth available in this band. Hence, to support this wider bandwith at the mmWave band, new radio access technology (RAT) should be provided for 5G systems. The new RAT with symmetry design for downlink and uplink should support different scenarios such as device to device (D2D) and multi-hop communications. This paper presents the path loss models in parking lot environment which represents the multi-end users for future 5G applications. To completely assess the typical performance of 5G wireless network systems across these different frequency bands, it is necessary to develop path loss (PL) models across these wide frequency ranges. The short wavelength of the highest frequency bands provides many scatterings from different objects. Cars and other objects are some examples of scatterings, which represent a critical issue at millimeter-wave bands. This paper presents the large-scale propagation characteristics for millimeter-wave in a parking lot environment. A new physical-based path loss model for parking lots is proposed. The path loss was investigated based on different models. The measurement was conducted at 28 GHz and 38 GHz frequencies for different scenarios. Results showed that the path loss exponent values were approximately identical at 28 GHz and 38 GHz for different scenarios of parking lots. It was found that the proposed compensation factor varied between 10.6 dB and 23.1 dB and between 13.1 and 19.1 in 28 GHz and 38 GHz, respectively. The proposed path loss models showed that more compensation factors are required for more scattering objects, especially at 28 GHz

Large-scale path loss models and time dispersion in an outdoor line-of-sight environment for 5G wireless communications

This paper presents path loss models and time dispersion parameters for different candidate frequencies above 6 GHz for fifth-generation (5G) wireless communications. Three well-known path loss models are compared for single-frequency and multi-frequency schemes: the close-in (CI) free space reference distance model, the floating intercept model (FI), and the alpha-beta-gamma (ABG) model. This paper also proposes a new path loss model to account for frequency attenuation (FA) with distance, which we term the FA path loss model. In this model, we introduce a frequency-dependent attenuation factor XF(f), which directly adds to the CI reference attenuation. Ultra-wideband measurements are conducted for different frequencies in the range of 10–40 GHz in an outdoor environment for line-of-sight scenarios. The time dispersion parameters mean excess delay, root mean square delay spread (RMS-DS), and maximum excess delay are estimated. The results reveal that the path loss exponent values for CI models are less than 1.4 in our experimental set-up. For the proposed FA model, with a path loss exponent of 1.4, the XF(f) attenuation factor values are less than 9.7 dB. The time dispersion findings from this work reveal that the RMS-DS values varied between 0.1 and 1.7 ns

Outdoor large-scale path loss characterization in an urban environment at 26, 28, 36, and 38 GHz

Most of the existing channel models cannot be applied to emerging millimeter-wave (mmWave) systems due to the difference between the characteristics of existing operating frequency bands and mmWave frequency bands. Thus, extensive studies on channel characterization and modeling are required to develop a general and suitable channel model that can accommodate a wide range of mmWave frequency bands in its modeling parameter. This paper presents a study of well-known channel models and their authentications for outdoor scenarios on the 26, 28, 36, and 38 GHz frequency bands. A new generalized path loss model for a range of mmWave frequency bands is proposed. Measurements for the outdoor line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios were taken every meter over a separation distance of 114 m between the TX and RX antenna locations to compare the well-known and the new large-scale generic path loss models. This outdoor channel characterization and modeling was conducted in Malaysia, which represents a tropical region environment, and the outcomes were investigated based on the proposed and the well-known path loss models for single- and multi-frequency schemes. Results show that the proposed model is simple and accurate in terms of frequency and environment signal attenuation. The path loss exponent values are 1.54 and 3.05 for the 20 GHz and 30 GHz bands, respectively. © 2018 Elsevier B.V

Enhanced Seamless Handover Algorithm for WiMAX and LTE Roaming

With the ever evolving mobile communication technology, achieving a high quality seamless mobility access across mobile networks is the present challenge to research and development engineers. Existing algorithms are used to make handover while a mobile station is roaming between cells. Such algorithms have some handover instability due to method of making handover decision. This paper proposes an enhanced handover algorithm that substantially reduces the handover redundancy in vertical and horizontal handovers. Also, it enables users to select the most appropriate target network technology based on their preferences even in the worst case where the mobile station roams between cell boundaries, and has high ability to have efficient performance in the critical area full of interferences. The proposed algorithm uses additional quality of service criteria, such as cost, delay, available bandwidth and network condition with two handover thresholds to achieve a better seamless handover process. After developing and testing this algorithm, the simulation results show a major reduction in the redundant handover, so high accuracy of horizontal and vertical handovers obtained. Moreover, the signal strength is kept at a level higher than the threshold during the whole simulation period, while maintaining low delay and connection cost compared to other two algorithms in both scenarios

Enabling remote-control for the power sub-stations over LTE-A networks

In recent years, smart grid (SG) applications have been proven a sophisticated technology of immense aptitude, comfort and efficiency not only for the power generation sectors but also for other industrial purposes. The term SG is used to describe a set of systems customized to rapidly and automatically monitor user demand, restore power, isolate faults and maintain stability for more efficient transmission, generation and delivery of electric power. Nevertheless, the quality of service (QoS) guarantee is essential to maintain the networking technology used in different stages and communication of the SG for efficient distribution, which may be drastically obstructed as the sensors of the application increases. Undoubtedly, receiving and transmitting of this information requires two-way, high speed, reliable and secure communication infrastructure. In this paper, we have proposed a scheduling approach guarantees the efficient utilization of existing network resources that satisfy the sensors’ demands sufficiently. The proposed approach is based on hierarchical adaptive weighting method, which helps to overcome the issues of studied scheduling approach and intended to aid SG sensors applications, based on its QoS demands. We have employed four enabler SG applications for remote power control, namely demand response, advanced metering infrastructure, video surveillance and wide area situational awareness applications for the implementation of the remote-power substation controlling. Moreover, the cooperative game theory technique has been incorporated into a solution for the optimal estimation and allocation of bandwidth among different sensors. The results have been evaluated in terms of throughput, fairness index and spectral efficiency and results have been compared with the well-known scheduling approaches such as exponential/proportional fairness (EXP/PF), best channel quality indicator (Best-CQI) and exponential rules (EXP-Rule). The results demonstrated that the proposed approach is providing a better performance in terms fairness index by 25, 66 and 68% compared to EXP/PF, EXP/RULE and Best-CQI, respectively

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

A new model to enhance the QoS of spectral amplitude coding-optical code division multiple access system with OFDM technique

A new optical orthogonal frequency division multiplexing technique with spectrum amplitude coding optical code division access (SAC-OCDMA) system is developed to enhance the channel data rate, reduce power, and increase the number of SAC-OCDMA system users. The average received signal-to-noise ratio with inter-modulation distortion of subcarriers is derived. Theoretical results are evaluated based on bit error rate, number of users, data rate, and amount of power saved. The proposed system is then compared with the traditional hybrid sub-carrier multiplexing (SCM)/SAC OCDM. The results show that the proposed system reduces approximately −8 dBm of power and doubles the number of users at a higher data rate than the SCM/SAC-OCDMA system. Proof-of-principle simulations of the proposed system are successfully implemented. Overall, the proposed system performed better than the SCM/SAC-OCDMA system. The system is designed based on modified double weight code, which provides better performance than Hadamard and modified frequency-hopping codes

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

<div><p>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.</p></div