Modeling and characterization of urban radio channels for mobile communications

Results of this thesis contribute in modeling and characterization of radio channels for future mobile communications. The results are presented mainly in three parts: a) modeling of propagation mechanisms, b) methodology of developing a propagation model, c) characterization of urban radio channel. One of the main propagation physical phenomena that have an important role in diverting signals to non line of sight scenarios is the diffraction process. This thesis proposes diffraction coefficients that have better agreement with finite difference time domain solution and rigorous diffraction theory than the coefficient commonly used in propagation predictions for mobile communications. The importance of diffuse scattering has also been investigated and showed that this physical process may have a key role in urban propagation, with a particular impact on the delay spread and angular spread of the signal at the receiver. This thesis proposes wideband propagation models for main and perpendicular streets of urban street grids. The propagation models are ray-based and are given in explicit mathematical expressions. Each ray is characterized in terms of its amplitude, delay, and angle of arrival, angle of departure for vertical and horizontal polarizations. Each of these characteristics is given in a closed mathematical form. Having wideband propagation model in explicit expression makes its implementation easy and computation fast. Secondary source modeling approach for perpendicular streets has also been introduced in this thesis. The last part of the thesis deals with characterization of urban radio channels for extracting parameters that help in successful design of mobile communication systems. Knowledge of channel characteristics enables reaching optimum trade off between system performance and complexity. This thesis analyzes measurement results at 2 GHz to extract channel parameters in terms of Rake finger characteristics in order to get information that helps to optimize Rake receiver design for enhanced-IMT2000 systems. Finger life distance has also been investigated for both micro- and small cell scenarios. This part of the thesis also presents orthogonality factor of radio channel for W-CDMA downlink at different bandwidths. Characterization of dispersion metrics in delay and angular domains for microcellular channels is also presented at different base station antenna heights. A measure of (dis-) similarity between multipath components in terms of separation distance in delay and angular domains is introduced by the concept of distance function, which is a step toward in development of algorithm extraction and analysis multipath clustering. In summary, the significant contributions of the thesis are in three parts. 1) Development of new diffraction coefficients and corrections of limitations of existing one for accurate propagation predictions for mobile communications. 2) Development of wideband propagation models for urban street grid. The novelty of the model is the development in explicit mathematical expressions. The developed models can be used to study propagation problem in microcellular urban street grids. 3) Presenting channel parameters that will help in the design of future mobile communication systems (enhanced-IMT2000), like number of active fingers, finger life distance, and orthogonality factors for different bandwidths. In addition, a technique based on multipath separation distance is proposed as a step toward in development of algorithms for extraction and analysis of multipath clusters.reviewe

Deterministic diffraction loss modelling for novel broadband communication in rural environments

This paper presents a deterministic modelling approach to predict diffraction loss for an innovative Multi-User-Single-Antenna (MUSA) MIMO technology, proposed for rural Australian environments. In order to calculate diffraction loss, six receivers have been considered around an access point in a selected rural environment. Generated terrain profiles for six receivers are presented in this paper. Simulation results using classical diffraction models and diffraction theory are also presented by accounting the rural Australian terrain data. Results show that in an area of 900 m by 900 m surrounding the receivers, path loss due to diffraction can range between 5 dB and 35 dB. Diffraction loss maps can contribute to determine the optimal location for receivers of MUSA-MIMO systems in rural areas

On Simulating Propagation for OFDM/MIMO Systems with the MR-FDPF Model

International audienceRadio propagation tools are needed for wireless network optimization. The MR-FDPF approach earlier proposed uses a multi-resolution pre-processing in the frequency domain. However, the current challenge for radio propagation tools not relies on providing signal power levels but beyond on providing a realistic prediction of the system performance. A system level simulator should comply with OFDM and MIMO features. This paper investigates the appropriateness of the MR-FDPF approach for such task

Antennas and Propagation Aspects for Emerging Wireless Communication Technologies

The increasing demand for high data rate applications and the delivery of zero-latency multimedia content drives technological evolutions towards the design and implementation of next-generation broadband wireless networks. In this context, various novel technologies have been introduced, such as millimeter wave (mmWave) transmission, massive multiple input multiple output (MIMO) systems, and non-orthogonal multiple access (NOMA) schemes in order to support the vision of fifth generation (5G) wireless cellular networks. The introduction of these technologies, however, is inextricably connected with a holistic redesign of the current transceiver structures, as well as the network architecture reconfiguration. To this end, ultra-dense network deployment along with distributed massive MIMO technologies and intermediate relay nodes have been proposed, among others, in order to ensure an improved quality of services to all mobile users. In the same framework, the design and evaluation of novel antenna configurations able to support wideband applications is of utmost importance for 5G context support. Furthermore, in order to design reliable 5G systems, the channel characterization in these frequencies and in the complex propagation environments cannot be ignored because it plays a significant role. In this Special Issue, fourteen papers are published, covering various aspects of novel antenna designs for broadband applications, propagation models at mmWave bands, the deployment of NOMA techniques, radio network planning for 5G networks, and multi-beam antenna technologies for 5G wireless communications

Map-based channel model parameterization and comparison of three different deterministic channel modelling methods

Abstract. The interest in studying the channel characteristics is exponentially increasing with the growth of the communication systems. Various channel modelling approaches have been discussed in the past decades. The ray-tracing based channel models are distinguished from the other channel models as they consider the environmental information and thus are expected to reflect the real propagation phenomena that exist in that specific environment. The goal of this thesis is to study the propagation channel characteristics of the three different channel models. The two deterministic channel models are the simplified map-based ray tracing channel model implemented in the METIS project and the full ray tracing-based channel model implemented by the Beijing Jiaotong University. The third channel model is the hybrid model based on METIS map-based channel. It uses the deterministic part of the METIS map-based channel model. Full ray-tracing based models require detailed description of the propagation environment or map and they target on site-specific channel modelling. Such site-specific models are not typically required in performance testing of devices, where the target is to ensure device performance in a typical propagation environment and possibly to cover some extreme cases. The simplifying map-based approach contradicts with the full ray tracing method in the way that the information of the map is reduced by approximating the building shapes and introducing artificial tiles to make scattering in the walls and ground reflections. Map-based channel modelling provides additional realism in channel models compared to traditional stochastic models applied in performance testing. The urban street canyon scenario was chosen to be modelled. The comparison was carried out at 3.5 GHz by means of performance metrics such as total path loss, LOS and NLOS propagation conditions at UE positions, K-factor, RMS delay spread, statistics of angles, angle spreads, and cross polarization ratios. The results have showed similarities in the LOS UE positions and dissimilarities in the NLOS UE positions. The reasons are identified and explained in the discussion section. It is decided to investigate the radio channel characteristics of the METIS map-based channel model and hybrid channel model for the future study purpose