Outdoor Radio Propagation Research Articles

Effects of Solar Radio Emissions on Outdoor Radio Propagation at 38 GHz Bands for D2D Communications

This letter presents empirical data documenting the effects of solar radio emissions on outdoor radio propagation at 38 GHz millimeter-wave (mmWave) band for both line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. Comparing the measurement data collected during a sunny day with the counterpart data collected at night, higher path loss exponent (PLE) values were observed during the day compared to nighttime. This is attributable to the decrease in the carrier-to-noise ratio for day-time signal propagation in sunny sky compared to nighttime. About 4% and 25% increase in PLE values was observed during the day for LOS and NLOS scenarios, respectively. This translates into corresponding decrease in the radio coverage of the wireless transmitter during the day compared to nighttime. Time-domain waveforms were also examined, and it was found that the average received signal envelope was 103 times below a given threshold during the day, and 19 times below the same threshold at night. This, thus, shows that the received signal envelope fades out many more times during the day compared to nighttime.

Characterization of Fading Statistics of mmWave (28 GHz and 38 GHz) Outdoor and Indoor Radio Propagation Channels

Extension of usable frequency spectrum from microwave to millimeter-wave (mmWave) is one of the key research directions in addressing the capacity demands of emerging 5th-generation communication networks. This paper presents a thorough analysis on the azimuthal multipath shape factors and second-order fading statistics (SOFS) of outdoor and indoor mmWave radio propagation channels. The well-established analytical relationship of plain angular statistics of a radio propagation channel with the channel’s fading statistics is used to study the channel’s fading characteristics. The plain angle-of-arrival measurement results available in the open literature for four different outdoor radio propagation scenarios at 38 GHz, as well as nine different indoor radio propagation scenarios at 28 GHz and 38 GHz bands, are extracted by using different graphical data interpretation techniques. The considered quantifiers for energy dispersion in angular domain and SOFS are true standard-deviation, angular spread, angular constriction, and direction of maximum fading; and spatial coherence distance, spatial auto-covariance, average fade duration, and level-crossing-rate; respectively. This study focuses on the angular spread analysis only in the azimuth plane. The conducted analysis on angular spread and SOFS is of high significance in designing modulation schemes, equalization schemes, antenna-beams, channel estimation, error-correction techniques, and interleaving algorithms; for mmWave outdoor and indoor radio propagation environments.

Improving the Accuracy of Millimeter-Wave Ray-Tracing Simulations by Modeling Roadside Trees

In recent years, ray-tracing simulation is widely adopted to model outdoor radio propagation. However, existing studies have not focused on the blockage effect of roadside trees. In this study, we model roadside trees using a variety of techniques to analyze their effect on the accuracy of channel modeling using ray-tracing simulation. The roadside trees were modeled as objects transmitting, reflecting, and diffracting electromagnetic waves. We noted that the results of ray-tracing simulations that included roadside trees were more accurate than simulations without tree effects, based on the deviations from the experimentally measured results.

Compressed Sensing of Sparse Multipath MIMO Channels with Superimposed Training Sequence

Recent advances in multiple-input multiple-output (MIMO) systems have renewed the interests of researchers to further explore this area for addressing various dynamic challenges of emerging radio communication networks. Various measurement campaigns reported recently in the literature show that physical multipath MIMO channels exhibit sparse impulse response structure in various outdoor radio propagation environments. Therefore, a comprehensive physical description of sparse multipath MIMO channels is presented in first part of this paper. Superimposing a training sequence (low power, periodic) over the information sequence offers an improvement in the spectral efficiency by avoiding the use of dedicated time/frequency slots for the training sequence, which is unlike the traditional schemes. The main contribution of this paper includes three superimposed training (SiT) sequence based channel estimation techniques for sparse multipath MIMO channels. The proposed techniques exploit the compressed sensing theory and prior available knowledge of channel's sparsity. The proposed sparse MIMO channel estimation techniques are named as, SiT based compressed channel sensing (SiT-CCS), SiT based hardlimit thresholding with CCS (SiT-ThCCS), and SiT training based match pursuit (SiT-MP). Bit error rate (BER) and normalized channel mean square error are used as metrics for the simulation analysis to gauge the performance of proposed techniques. A comparison of the proposed schemes with a notable first order statistics based SiT least squares (SiT-LS) estimation technique is presented to establish the improvements achieved by the proposed schemes. For sparse multipath time-invariant MIMO communication channels, it is observed that SiT-CCS, SiT-MP, and SiT-ThCCS can provide an improvement up to 2, 3.5, and 5.2 dB in the MSE at signal to noise ratio (SNR) of 12 dB when compared to SiT-LS, respectively. Moreover, for $$\mathrm {BER}=10^{-1.9}$$BER=10-1.9, the proposed SiT-CCS, SiT-MP, and SiT-ThCCS, compared to SiT-LS, can offer a gain of about 1, 2.5, and 3.5 dB in the SNR, respectively. The performance gain in MSE and BER is observed to improve with an increase in the channel sparsity.

Radio Propagation Channel Measurements for Multi-Antenna Satellite Communication Systems: A Survey

For the terrestrial infrastructure, the multiple-input multiple-output (MIMO) architecture is a key technology that has brought the wireless gigabit vision closer to reality. Satellite communication systems have not been immune from this wave of innovation, and theoretical and experimental efforts have recently been devoted to the investigation of the applicability of multiple-antenna techniques to these systems. This paper intends to highlight and critically present the most important results from measurement campaigns conducted to characterize the radio channel of multi-antenna satellite systems. Emphasis is given on the viability of MIMO technology over satellite, and the potential enhancements in terms of channel capacity and link reliability that can be achieved through spatial and/or polarization diversity. The configurations under investigation range from very simple single-input multiple-output (SIMO) systems, with multiple antennas only at the terrestrial receiver, to quite complex and challenging systems, such as dual-satellite multiple-input single-output (MISO) systems, and single-satellite dual-polarized MIMO systems. The spotlight is on land mobile satellite (LMS) systems in outdoor radio propagation environments. However, satellite-to-indoor reception is also included.

Research on Outdoor Positioning Based on Ray Tracing Method

GPS can’t detect the signal because of the cell complex environment in the outdoor and poor radio wave propagation conditions, so that the positioning result is not ideal. However, the positioning method using the ray tracing prediction of radio waves, the tracking point of the scene from all the source radiation, record the relevant parameters, and then positioned within the microcell environment can satisfy the demand. The principle of ray tracing was firstly introduced in this paper, then an outdoor positioning model was set up, finally, the corresponding simulation experiments was implemented to demonstrate the effectiveness of ray tracing positioning in the outdoor environments.

A Novel Inversion Method for Outdoor Coverage Prediction in Wireless Cellular Network

A novel coverage-prediction method for outdoor radio propagation based on the inversion theory is proposed here. Coverage prediction in a wireless cellular network is treated as an inverse problem instead of using high-precision geometric modeling. More precisely, the problem is solved by an inversion of the measured data under some <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> constraints, and the complicated propagation-prediction problem is reduced to solving a system of large-scale ill-condition equations. The effectiveness of the proposed method is demonstrated by using experiments under various radio environments in Guangdong, China. The prediction results are approximately consistent with independent checking samples, and the proposed strategy is compared with other existing approaches.

Measurement of attenuation and phase on 26-GHz wide-band point-to-multipoint signals under the influence of rain

This letter presents the results of a study on rain attenuation of an outdoor radio propagation channel at 26 GHz, which is widely used for local multipoint distribution service deployment. The difference in attenuation between vertical and horizontal polarization is compared for wide-band signals using a line-of-sight radio link with alternate polarizations by transmitting signals with horizontal and vertical polarizations. It is shown that attenuation difference due to depolarization becomes much more significant when the rainfall exceeds 70 mm/h.

Radio propagation measurements and prediction using three-dimensional ray tracing in urban environments at 908 MHz and 1.9 GHz

There is an explosive growth in the market of wireless communications services in urban areas. New regulatory environments as well as competition in the communications industry require that these systems be deployed quickly and at low cost. Computer-based radio propagation prediction tools are strong candidates for this goal. We introduce an outdoor radio propagation prediction tool using a ray tracing technique in two dimensions (2-D) and three dimensions (3-D). We have compared the predicted and measured results in various propagation environments. Comparisons indicate that 2-D is adequate for a low transmitter while 3-D is recommended for a high transmitter whose height is comparable with or higher than surrounding buildings. In most locations, the computer tool predicts the correct propagation loss with a mean error of less than 7 dB and a standard deviation of less than 8 dB.

Parallel irregular software for wave propagation simulation

The objective of the European project STORMS (software tools for the optimization of resources in mobile systems) is to develop a software tool to be used for the design and the planning of the future universal mobile telecommunication system (UMTS). In this context the ParFlow method permits the simulation of outdoor radio wave propagation in urban environment, modelling the physical system in terms of the motion of fictitious microscopic particles over a lattice. This paper gives an overview of the ParFlow method, and reports the design and the implementation of ParFlow++, an object-oriented irregular parallel software for urban outdoor radio wave propagation prediction.