Channel Measurements

The impact of spatial correlation on the multi-input multi-output ultrawide band (MIMO-UWB) system using the time reversal (TR) technique is investigated. Thanks to TR, several data streams can be transmitted by using only one antenna in a system named virtual MIMO-TRUWB. Since the virtual MIMO-TR-UWB system is not affected by the transmit correlation, under the condition of the high spatial correlation, it outperforms the true MIMO-UWB system with multiple transmit antennas. The channel measurements are performed in short-range indoor environment, both line-of-sight and non-line-of-sight to verify the adopted correlated channel model.

Most millimeter wave (mmWave) channel measurements are conducted with different configurations, which may have large impacts on propagation channel characteristics. In addition, the comparison of different mmWave bands is scarce. Moreover, mmWave massive multiple-input multipleoutput (MIMO) channel measurements are absent, and new propagation properties caused by large antenna arrays have rarely been studied yet. In this paper, we carry out mmWave massive MIMO channel measurements at 11-, 16-, 28-, and 38-GHz bands in indoor environments. The space-alternating generalized expectation-maximization algorithm is applied to process the measurement data. Important statistical properties, such as average power delay profile, power azimuth profile, power elevation profile, root mean square delay spread, azimuth angular spread, elevation angular spread, and their cumulative distribution functions and correlation properties, are obtained and compared for different bands. New massive MIMO propagation properties, such as spherical wavefront, cluster birth-death, and non-stationarity over the antenna array, are validated for the four mmWave bands by investigating the variations of channel parameters. Two channel models are used to verify the measurements. The results indicate that massive MIMO effects should be fully characterized for mmWave massive MIMO systems.

Theoretical models of ultrawideband (UWB) radio channels indicate that pairs of UWB radio transceivers measure their common radio channel with a high degree of agreement and third parties are not be able to accurately estimate the state of the common channels. These properties allow generation of secret keys to support secure communications from UWB channels measurements. In this paper, the results of UWB propagation studies are presented that validate the required properties to support secret key generation in a typical indoor environment. Key generation algorithms are employed on the measured data and key lengths on the order of thousands of bits are obtained capable of supporting most popular cryptographic systems. The paper also reports measurements of the spatial and temporal correlation of the UWB channel from which the relative privacy of the secret keys can be determined as well as the rate new secret keys may be generated.

In a bid to meet the growing demands for mobile satellite applications, communication systems designers have been concerned about how rain attenuation affects satellite communication links especially in tropical region. This study has been conducted to characterize rain fade on satellite communication links in Jos (9.95650N, 8.85830E, 1,192 m), a semi-tropical region of Nigeria. The study will avail communication service providers with necessary information to improve the quality of service within the region. Rain data were retrieved from the Davis weather station for a period of one year in 2014. Rain attenuation data were obtained from a Ku-band beacon link set at a look-up angle of 56.50 on the European Telecommunication Satellite (EUTELSAT W4/W7) orbited on 036E. The different rain rates and their corresponding rain attenuation values were analyzed to obtain basic characteristics of rain fade in the region. The results showed that, as the rain increases in intensity, the measure...

Background: Predicted rain fade values for an Earth-satellite link operating at X-band frequency had been generated using the latest ITU-R Recommendation, P618-11. Rain fade values for the very same link were also estimated using the "radar-derived attenuation" technique. The radar technique involves the exploitation of vertical polarization S-band meteorological radar reflectivity information to calculate the possible rain attenuation along the satellite propagation paths. All estimated rain fade values were then compared with the actual measured signal of RazakSAT's X-band satellite transmission. The measured X-band (8 GHz) transmission signals were collected and analyzed at the Malaysian National Space Agency (NSA) space center. Objective: Preliminary findings concerning the feasibility of each estimation technique are presented in this paper. The research also attempts to investigate the validity of the mentioned rain attenuation estimation techniques. Results: Preliminary findings concerning the feasibility of each estimation technique are presented in this paper. The research also attempts to investigate the validity of the mentioned rain attenuation estimation techniques. Conclusion: Such knowledge can be considered critical for the design of reliable Earth-Space communication link and certainly can be used in the preliminary proposition plan for the link designers as well as engineers.

The impact of spatial correlation on the multi-input multi-output ultrawide band (MIMO-UWB) system using the time reversal (TR) technique is investigated. Thanks to TR, several data streams can be transmitted by using only one antenna in a system named virtual MIMO-TRUWB. Since the virtual MIMO-TR-UWB system is not affected by the transmit correlation, under the condition of the high spatial correlation, it outperforms the true MIMO-UWB system with multiple transmit antennas. The channel measurements are performed in short-range indoor environment, both line-of-sight and non-line-of-sight to verify the adopted correlated channel model.

SOPHIA is the software radio extension to the MONROE measurement and experimentation project. Under MONROE, fixed and mobile nodes for network measurement and experimentation have been distributed across 4 European countries. Each node provides a powerful platform for wireless systems analysis, consisting of a flexible PC and a number of mobile broadband modems connected to different operator networks. Through the SOPHIA project extension, MONROE nodes have been enhanced with software radio capabilities, greatly expanding the range of measurements and experiments which can be supported by the platform. This paper presents the SOPHIA project extension, describing the baseband and RF front-end hardware selected to enhance the MONROE nodes and outlining the software tools which can be leveraged by the new, enhanced platform. The capabilities of the SOPHIA-enhanced MONROE platform are illustrated using detailed performance measurements of LTE networks,

Atmospheric condition variations were shown to have a major effect on the earth sky signal quality at Ku band. Moreover, such variations increased in the tropical regions as compared to temperate areas due to their different weather parameters. With the increase of recent satellite communication technology applications throughout the tropical countries and lack of information regarding the atmospheric impairments analysis, simulation and mitigation techniques, there is an ever increasing need for extracting a unique and accurate performance of the signal quality effects during highly natural tropical weather impairments. This paper presents a new method developed for proper analysis with distinctive and highly realistic performance evaluation for signal quality during the atmospheric conditions variations in 14 tropical areas from the four continents analyzed based on actual measured parameters. The method implementation includes signal attenuation, carrier to noise ratio, symbol energy to noise ratio, and symbol error rate at different areas and different modulation schemes. Furthermore, for improvement in analysis in terms of covering more remarkable regions in tropics, the paper provides new measurements data with analysis for certain region in tropics used as a test bed and to add measurement data of such area to the world's data base for future researchers. The results show a significant investigation and performance observation in terms of weather impairments in tropical regions in general and each region in that area in particular regarding the signal attenuation and error rates accompanied for several transmission schemes.

Wireless avionics intra-communication (WAIC) refers to a wireless communication system among electronic components (e.g., sensors and actuators) that are integrated or installed in an aircraft and it is proposed to replace heavy and expensive wired communication cables. Recently, the use of a frequency band (4.2–4.4 GHz) for the WAIC (so-called, WAIC band) has been approved by international telecommunication union (ITU). Accordingly, several existing wireless protocols such as IEEE 802.11 and IEEE 802.15 are being considered as candidate techniques for the intra-avionics sensor network. In this paper, we perform a real field experiment to investigate wireless channel characteristics in intra-avionics sensor networks at the WAIC bands by a software-defined radio platform (universal software radio peripheral, USRP) and self-produced monopole antennas for the WAIC band. Through the experiment, we validated the feasibility of IEEE 802.11 protocol for the intra-avionics sensor network at...

In this paper, path loss and time-dispersion results of the propagation channel in a typical office environment are reported. The results were derived from a channel measurement campaign carried out at 26 GHz in line-of-sight (LOS) and obstructed-LOS (OLOS) conditions. The parameters of both the floating-intercept (FI) and close-in (CI) free space reference distance path loss models were derived using the minimum-mean-squared-error (MMSE). The time-dispersion characteristics of the propagation channel were analyzed through the root-mean-squared (rms) delay-spread and the coherence bandwidth. The results reported here provide better knowledge of the propagation channel features and can be also used to design and evaluate the performance of the next fifth-generation (5G) networks in indoor office environments at the potential 26 GHz frequency band.

In this paper, we explore design aspects of adaptive modulation based on orthogonal frequency-division multiplexing (OFDM) for underwater acoustic (UWA) communications, and study its performance using real-time at-sea experiments. Our design criterion is to maximize the system throughput under a target average bit error rate (BER). We consider two different schemes based on the level of adaptivity: in the first scheme, only the modulation levels are adjusted while the power is allocated uniformly across the subcarriers, whereas in the second scheme, both the modulation levels and the power are adjusted adaptively. For both schemes we linearly predict the channel one travel time ahead so as to improve the performance in the presence of a long propagation delay. The system design assumes a feedback link from the receiver that is exploited in two forms: one that conveys the modulation alphabet and quantized power levels to be used for each subcarrier, and the other that conveys a quantized estimate of the sparse channel impulse response. The second approach is shown to be advantageous, as it requires significantly fewer feedback bits for the same system throughput. The effectiveness of the proposed adaptive schemes is demonstrated using computer simulations, real channel measurements recorded in shallow water off the western coast of Kauai, HI, USA, in June 2008, and real-time at-sea experiments conducted at the same location in July 2011. We note that this is the first paper that presents adaptive modulation results for UWA links with real-time at-sea experiments.

In this paper we have investigated the effects of vehicular traffic on interpersonal wearable-to-wearable (W2W) communications channels in an urban environment at 2.45 GHz. In particular, we have studied the perturbations in the received signal caused by different types of vehicles as they passed through a channel between two persons who maintained various relative orientations while positioned at the opposite sides of a road. As the channel underwent different fading mechanisms depending on whether the vehicle was approaching, transitioning (i.e., intersecting the direct signal path) or receding from the persons, the overall disturbance was appropriately segmented depending on the journey stage. The results have shown that relative body orientation was a significant factor when considering the impact that a vehicle can have on a W2W link. When both persons faced the oncoming traffic, the link was particularly susceptible to significant fading events with variations in the received signal power from the unperturbed state as great as 44.1 dB observed to occur. For all of the journey stages, irrespective of the relative orientation of the persons, the logarithmically transformed longterm fading process was found to be multimodal and well described by a Gaussian mixture model. During the transitioning phase, shadowing caused by the passing automobile obstructing the line-of-sight (LOS) signal path was found to be the main contributor to the signal fading. However, probably the most remarkable result of the channel characterization work conducted in this study was the severity of the short-term fading often observed in this emerging wireless network. Such was intensity of the measured envelope fluctuation in many of the scenarios, we have been able to utilize the recently proposed κ − µ Extreme distribution with great success and in the process, provide a further important empirical validation of this new fading model. Moreover, we have used the Resistor-Average Distance (RAD) which is derived from the Kullback-Leibler distance (DKL) to show the improved fit that the κ − µ Extreme distribution offers compared to the κ−µ distribution when used to model the W2W channel in this fading environment.

Satellite communication links at a frequency above 10 GHz experience severe attenuation due to rain, particularly in tropical regions. Reliable long-term rain fade empirical data for Ka-band satellite link in Malaysia and tropical areas are indeed limited. The main objective of this paper is to provide and present the findings of an empirically measured rain fade at the Ka-band of 20.01 GHz and the cumulative distribution analysis. An 8.1 m dual Gregorian dish antenna with 21 dB/K G/T and a meteorological standard dual type tipping bucket are used to measure the Ka-band beacon signal emanating from the MEASAT-5 satellite and the rainfall intensity, respectively, for a period of two years. Cumulative distribution of rain fade for monthly, annual and monsoon seasons were compiled to reflect the accurate changes in Malaysian weather. The measured rain fade is at 10 dB and 29 dB for the exceeded percentage of 0.3% and 0.1%, respectively. At rain fade of 33 dB, the receiver begins to sat...

Cloud-cover statistics, low cloud base height, frequency of precipitation, 0°C isothermal height, and integrated cloud liquid water and cloud attenuation have been obtained for the tropical rain forest climatic zone of Africa. The cumulative distribution of integrated cloud liquid water content shows a departure from the ITU-R model. A comparison of cloud attenuation at Ka-and V-bands show that the ITU-R model underestimates the attenuation up to about 1.7 and 2.3 dB at 30 and 50 GHz, respectively. View less Metadata Contents

The advancement of satellite communication has arisen tremendously where higher capacity communications systems are needed. Most satellite engineers are shifting to Ka, Q, and V-band upcoming since the low frequencies such as below 10 GHz are already congested. Actual measurement data at millimetre-wave frequencies in tropical regions are minimal. The prediction of rain attenuation at frequencies above 10 GHz is required to determine a reliable fade margin. In this paper, a statistical frequency scaling technique has been developed as an alternative way of estimating rain attenuation. The technique was derived based on the correlation between the attenuation ratio of a higher and lower frequency against the attenuation at a lower frequency. The attenuations from the proposed model were compared to the proposed frequency scaling by International Telecommunication Union-R (ITU-R) as well as the conventional ITU-R rain prediction model. To deliver a reliable model, validation methods have been done using a set of data with different years and locations in tropical regions. A dependent prediction technique with the lowest root mean square error (RMSE) value and error was produced. This technique is beneficial in applying suitable mitigation techniques to moderate rain fade in tropical regions.

Much investigative studies have been performed over the years on electromagnetic wave signals being attenuated by rain, cloud, gas and tropospheric scintillation. This paper present the impact of tropospheric scintillation on earth-space path in southwest, Nigeria at 12.245 GHz. Twenty-four months of scintillation data from ASTRA 2E/2F/2G on latitude 6.7° N and longitude 3.23° E for two years (2015-2016) were statistically analysed and compare with four existing models. The result reveals that under non-rainy atmosphere, ITU-R model gave the lowest percentage error of about 1.07%, followed closely by Karasawa model with 1.67%. The work also shows that ITU-R is the best fit model of tropospheric scintillation fade for the study area at 1% of time. A modified ITU-R scintillation fade model was also proposed for the tropical region of Ota and its environs.

The CricketSatellite is a Space Temperature Module that relays a Frequency (433 MHz) to the receiving antenna. The module transmits an audio tone that changes frequency due to temperature within the atmosphere. The satellite is attached to helium balloons. Applications such as High Definition Software Defined Radio (HDSDR) and Audio Analyzers (Spectrum Lab) are required for the interpretation of transmitted signals. Calibration Calibration is used to establish relationships between frequency and temperature. 1) Signals are received and interpreted through the HDSDR application. 2) Signals are displayed through the Spectrum Lab application.

The nature of this deliverable of WP2.1 ("Radio interfaces for next-generation wireless systems") is mainly descriptive; it introduces the EuWIn lab at large, providing detailed descriptions about its three sites (CTTC, CNIT/Bologna, CNRS/Eurecom), its goals, and the means to achieve them. It also includes an accurate report on the technical facilities that are available at EuWIn@CTTC and the interfaces through which they can be accessed. Finally, this document also includes the preliminary plan of activities (first JRA proposals, web portal, web meetings, workshops, training schools, industry liaisons, demonstration activities and experimental tours) together with the lab access policies.

In this paper, path loss and time-dispersion results of the propagation channel in a typical office environment are reported. The results were derived from a channel measurement campaign carried out at 26 GHz in line-of-sight (LOS) and obstructed-LOS (OLOS) conditions. The parameters of both the floating-intercept (FI) and close-in (CI) free space reference distance path loss models were derived using the minimum-mean-squared-error (MMSE). The time-dispersion characteristics of the propagation channel were analyzed through the root-mean-squared (rms) delay-spread and the coherence bandwidth. The results reported here provide better knowledge of the propagation channel features and can be also used to design and evaluate the performance of the next fifth-generation (5G) networks in indoor office environments at the potential 26 GHz frequency band.

Free space fading for satellite link propagation studies in the equatorial regions are indeed particularly scarce, complicated and expensive to venture upon. Most of satellite propagation studies done in temperate climate are not reasonable for countries in the equatorial region due to its huge climate differences. In equatorial regions, the future stratospheric and space-based telecommunications systems are expected to operate with high elevation angle slant paths and high frequency of operation from the Earth stations’ point of view. These systems will also be sharing frequency bands with other terrestrial and space services. From this standpoint, a precise modelling of the vertical variation of free space path loss parameters will be of great interest for improving the prediction of the clear sky margin along the slant path in the tropics. In this paper, the Free Space Path Loss (FSPL) propagation link for Xband and S-band RazakSAT satellite will be analysed using a Terminal Dopp...

This paper describes a short-term rain attenuation predictor model for terrestrial radio links located in tropical area. The predictor is based on the fade-slope statistics that are modeled by a generalization of Van de Kamp (VDK) distribution for rain attenuation levels between 1 and 30 dB. The predictor can improve adaptive fade countermeasures as it predicts the rain attenuation in the next ten-seconds based on the current attenuation value. The model is applied to data collected in four links located in tropical region and its results show that the absolute values of prediction errors are under 2.9 dB for 99.9% of the predictions.

The loss of signal in terms of attenuation is very common problem. Signal attenuation can cause degradation in the Quality of service (QoS) in wireless communication. Networks operating over high frequency bands are highly affected by signal attenuation. This is particularly trivial in the millimeter (mm) wave bands. The number of climatic factors which cause signal attenuation include fog, cloud, rain, gas but attenuation due to clouds is a complex study because of the structure of clouds and higher probability of occurrence. It is important to investigate the effect of clouds on electromagnetic waves and to study the models of cloud attenuation as its role at mm is significant. This research work presents the comparative study of such empirical models which provides the cloud attenuation considering frequency, elevation angle and liquid water content as input parameters. Simulated results showed that liquid water content and frequency are directly proportional to cloud attenuation...

Severe tropical weather dynamics impairments on the earth-sky signal quality at Ku-band relative to temperate weather increase the demand for land mobile satellite (LMS) channel characterization and modeling specific to tropical regions. Variation in weather dynamics decreases the accuracy of the existing LMS channel models if applied to the tropics. This study presents a tropical weather-aware LMS channel model that can be applied at areas with diverse atmospheric (rain, clouds, and tropospheric scintillation) and mobility impairments. The proposed tropical-LMS channel (TRO-LMSC) model is designed on the basis of actual experimental measurements conducted in a tropical area. The TRO-LMSC model involves multipath design, mobility model, rain impairment model, cloud impairment model, tropospheric scintillation model, and link budget module. The proposed model shows improved channel modeling accuracy and comprehensiveness with relatively less root mean square error compared with existing models. Consequently, this improvement enhances the identification of the type and performance of the fade mitigation technique, the management of available communication resources, as well as the reliability and efficiency of the communication services.

Atmospheric condition variations were shown to have a major effect on the earth sky signal quality at Ku band. Moreover, such variations increased in the tropical regions as compared to temperate areas due to their different weather parameters. With the increase of recent satellite communication technology applications throughout the tropical countries and lack of information regarding the atmospheric impairments analysis, simulation and mitigation techniques, there is an ever increasing need for extracting a unique and accurate performance of the signal quality effects during highly natural tropical weather impairments. This paper presents a new method developed for proper analysis with distinctive and highly realistic performance evaluation for signal quality during the atmospheric conditions variations in 14 tropical areas from the four continents analyzed based on actual measured parameters. The method implementation includes signal attenuation, carrier to noise ratio, symbol energy to noise ratio, and symbol error rate at different areas and different modulation schemes. Furthermore, for improvement in analysis in terms of covering more remarkable regions in tropics, the paper provides new measurements data with analysis for certain region in tropics used as a test bed and to add measurement data of such area to the world's data base for future researchers. The results show a significant investigation and performance observation in terms of weather impairments in tropical regions in general and each region in that area in particular regarding the signal attenuation and error rates accompanied for several transmission schemes.

This paper provides a first look at the potential for implementing a high-bandwidth air/ground (A/G) digital networked voice and data system in the very high frequency (VHF) band. The Future Communication study (FCS), a joint study performed by the Federal Aviation Administration (FAA) and EUROCONTROL, evaluated several systems and found the system called Broadband-Aeronautical Mobile Communications (B-AMC) to be a leading technology candidate to supply data communications in the L-band. Based on the FAA's desire to maintain operations in the VHF band and on the 2007 World Radiocommunications Conference (WRC-07) decision to make 112 -117.975 MHz available for aeronautical mobile communications, The MITRE Corporation's Center for Advanced Aviation System Development (CAASD) investigated the feasibility of implementing B-AMC in the VHF band and determined its potential for supporting networked voice using Voice over Internet Protocol (VoIP). Furthermore, this study examined how the B-AMC protocol layers can be tailored to VoIP protocols in terms of meeting certain performance measures. * An Electronic Industries Alliance (EIA)/TIA standardized system for provision of packet data services in an interoperable dispatch oriented topology for public safety providers.

At the rise of the fourth industrial revolution, artificial intelligence (AI), along with key enabling technologies such as millimeter waves (mm-waves) can be used to launch the fifth-generation (5G) and beyond communication links. However, the quality of radio links at higher frequency bands is limited by atmospheric elements. Among others, rainfall is the major propagation impairment at millimetric wave bands, which needs to be considered during the link budget planning. In this study, we investigated the rain attenuation results obtained from experimental data, existing models, and proposed supervised artificial neural network (SANN) at K , Ka, and E-bands, respectively, for terrestrial links in South Korea. The measurement campaigns were between Incheon, National Radio Research Agency (RRA) tower station, to the EMS Dongyoksang tower station operating at 75 GHz over a 100-m path length, and between Incheon, RRA tower station to Khumdang, Korea Telecom (KT) tower station, operating at 18 and 38 GHz over a 3.2km path length. The three-year rainfall and received signal level data measurements over these paths were used to determine rain attenuation distributions at different percentages of exceedance time distribution. Additionally, three existing attenuation models, ITU-R 530.17, Lin, and Revised Silva Mello (RSM) models were compared with measured rain attenuation. Our results indicate that these models did not correspond with measured results. Therefore, in this research, we proposed a supervised learning-based attenuation prediction method, which provides better performance than existing models. Furthermore, we validated our proposed model with measured received-signal level and rainfall data at the above-mentioned operating frequencies. INDEX TERMS Artificial neural network, millimeter wave, rain attenuation, South Korea, terrestrial links.

The spectral capacity of VHF aeronautical radio is rapidly reaching saturation in the United States and in Europe. A key functional objective for any future civil aviation communications technology is providing relief to the current spectral congestion. This article provides a review on the existing national and global aeronautical radio networks. The spectrum depletion problem is described. Recent developments in narrowband and wideband digital communications for potential applications in civil aviation are discussed. Comments are made on critical issues that must be considered when selecting a communication technology for aeronautics which addresses the spectral congestion problem and simultaneously supports transformation to a long term network centric solution. Recommendations are made on some possible communication technologies that may bring about short-term resolution to VHF spectrum depletion without requiring major changes in ground infrastructure or on-board avionics.