Vehicle-to-Everything (V2X) communication is essential for improving traffic safety and efficiency. This study investigates the performance of the NR-V2X communication system in urban environments. It focuses on an urban intersection approach scenario, in which vehicles approach from different directions, increasing collision risk and demanding highly reliable communication. Unlike prior work relying on stochastic channel models, we derive channel impulse responses using ray tracing and integrate them into the ns-3 simulator. We examine the effects of varying vehicle density, packet transmission rate, bandwidth, and subcarrier spacing. Under a 20MHz channel, 20Hz packet rate, and 15kHz subcarrier spacing, increasing the number of vehicles from five to ten raises the median end-to-end delay by approximately 46% (from 3.5ms to 5.1ms) and reduces the median throughput by about 23% (from 78kbit/s to 60kbit/s). Increasing bandwidth primarily enhances throughput, while larger subcarrier spacing (30kHz vs. 15kHz) significantly reduces delay. These quantified tradeoffs provide practical guidance for designing resilient NR-V2X links in dense urban environments.

With the aim of improving cell edge throughput in interference-limited networks, different Inter-cell Interference (ICI) mitigation techniques have been proposed. Accurately assessing the potential performance gains of such techniques requires a comprehensive understanding of the large-scale fading correlation characteristics between Transmission Points (TPs). This paper focuses on the analysis of the slow fading correlation of the received power from multiple TPs in different environments, specifically distinguishing between co-located and distributed TP sets. Accordingly, comprehensive measurements by means of drive tests and corresponding evaluations have been conducted in four environments (Urban, Suburban, Rural and Highway) within a commercial LTE network. The analysis provides valuable insights for the design of robust transmission strategies such as Coordinated Multipoint (CoMP) and accurate network planning. The results reveal that co-located TP sets exhibit significantly higher slow fading correlation only in Rural and Highway environments, where propagation paths are less obstructed. On the other hand, co-located TP and distributed TP sets yield similar rather low correlations in both Urban and Suburban environments.

The 6 GHz spectrum is widely recognized as a key frequency band by various wireless communication organizations, including cellular and IEEE Std 802.11ax (Wi-Fi 6). Consequently, addressing coexistence mechanisms between cellular, in other words, 5G New Radio-Unlicensed (5G NR-U) in the 3rd Generation Partnership Project (3GPP) and Wi-Fi in this unlicensed band is essential for enhancing wireless communication efficiency, especially during co-channel operation. The U-NII-7 sub-band regulated by the Federal Communications Commission (FCC) allows both indoor and outdoor operation. Thereby, devices operating in this band are required to connect to the Automated Frequency Coordination (AFC) system database for license-exempt use, and the operation is permitted only if the device is located outside exclusion zones. This study investigates the influence of a geolocation-based exclusion zone on the interference level between 5G NR-U and Wi-Fi as a function of exclusion zone radius. Simulation results based on a Monte Carlo method show that, in some cases, applying a geolocation-based exclusion zone, in which Wi-Fi routers are not allowed to operate within a certain distance of a 5G NR-U base station, can effectively suppress high levels of aggregate interference under co-channel operation, even without the use of advanced dynamic spectrum allocation techniques.

In this paper, we describe the extraction of parameters for a non-stationary tapped delay line channel model using first-order Markov chain in a V2V environment based on the measurement data. We analyze key properties such as delay spread, amplitude statistics, Doppler frequency, and correlations within a V2V environment. The number of taps required to model the channel is calculated, and the reliability of the channel model is evaluated based on the mean square delay spread of the channel. Our comprehensive investigation aims to enhance the understanding of dynamic channel behavior in V2V communication and to provide valuable insights for the development and optimization of communication systems in vehicular environments.

Coordinated multipoint (CoMP) concepts promise significant performance gains in mobile radio networks as has been shown by numerous studies by means of limited field trials, simulations or analytical models. In order to predict the potential performance benefits of CoMP in terms of joint transmission (JT) for real network deployments in different environments, a simple semi-analytical approach based on comprehensive measurements in real-world network deployments is applied in this paper. Typical urban, suburban, rural and highway scenarios are evaluated and the performance for coherent and non-coherent JT is deduced from the evaluation of reference signal received power (RSRP) levels of available cells. Special attention is thereby devoted to the distinction between inter-site and intra-site CoMP, since this is of significant importance for network operators intending to integrate CoMP functionality into their mobile radio networks. The results confirm that rural and highway scenarios would rather necessitate inter-site JT while urban and suburban environments favor intra-site JT due to the increased site density.

This paper presents a novel approach to predict radio signal strength in wireless networks combining geometry extraction techniques and Machine Learning (ML). Traditional methods whether empirical or deterministic have their own ad-vantages and disadvantages, with empirical methods often falling short with accuracy, while deterministic models can be resource intensive, especially with large scenarios. Our approach proceeds towards a hybrid implementation of environment description, exploring the complex relationships between the different environmental factors and signal strength, harnessing the power of ML. We employ LightGBM, a powerful tree-based learning algorithm with a gradient boosting framework, to predict signal strength based on a set of features. These features include transmitter height, location coordinates, distance, buildings and terrain height. In our study, labels represent the actual signal strength in different scenarios, we utilized a unique approach of training our model using two distinct sources of labels: Ray traced and measurement data. The ray traced labels were extracted from a large variety of urban cities, consisting of high building density and diverse infrastructures. The results demonstrate that our hybrid approach was able to provide promising results with a standard deviation of approximately 1.2 dB in comparison with ray tracing, while utilizing a fraction of the resources. Additionally, the model was able to adapt to the measurement data, offering high accuracy results with a standard deviation of approximately 2.6 dB.

For energy efficient operation of the massive multiple-input multiple-output (MIMO) networks, various aspects of energy efficiency maximization have been addressed, where a careful selection of number of active antennas has shown significant gains. Moreover, switching-off physical resource blocks (PRBs) and carrier shutdown saves energy in low load scenarios. However, the joint optimization of spectral PRB allocation and spatial layering in a heterogeneous network has not been completely solved yet. Therefore, we study a power consumption model for multi-cell multi-user massive MIMO 5G network, capturing the joint effects of both dimensions. We characterize the optimal resource allocation under practical constraints, i.e., limited number of available antennas, PRBs, base stations (BSs), and frequency bands. We observe a single spatial layer achieving lowest energy consumption in very low load scenarios, whereas, spatial layering is required in high load scenarios. Finally, we derive novel algorithms for energy efficient user (UE) to BS assignment and propose an adaptive algorithm for PRB assignment and power control. All results are illustrated by numerical system-level simulations, describing a realistic metropolis scenario. The results show that a higher frequency band should be used to support UEs with large rate requirements via spatial multiplexing and assigning each UE maximum available PRBs.

This paper presents an assessment of the accuracy of a deterministic channel model resulting from ray-tracing. The study involves comparing the channel impulse response obtained from ray-tracing with the channel impulse response derived from a measurement campaign conducted in the city of Braunschweig, Germany. The analysis primarily focuses on power delay profiles and channel gains in an urban scenario. The results demonstrate a high level of agreement between the simulation and measurement outcomes. This paper also investigates the impact of vehicle density on the V2V channel characteristics within the urban environment. The analysis reveals that surrounding vehicles are not negligible, they cause higher multi-path components in intersection, which should be taken into account.

In this paper, we analyze a measured time-variant channel impulse response of a dynamic driving maneuver at an urban intersection in the context of V2X communication. Channel correlation metrics are introduced to identify segments with similar channel conditions. The impact of different correlation cut-off levels on segment identification is discussed. The resolved segments can be used in the future to generate channel models for conformance testing of real chipsets.

Artificial intelligence (AI) is considered an efficient response to several challenges facing 6G technology. However, AI still suffers from a huge trust issue due to its ambiguous way of making predictions. Therefore, there is a need for a method to evaluate the AI’s trustworthiness in practice for future 6G applications. This paper presents a practical model to analyze the trustworthiness of AI in a dedicated 6G application. In particular, we present two customized deep neural networks (DNNs) to solve the automatic modulation recognition (AMR) problem in Terahertz communications-based 6G technology. Then, a specific trustworthiness model and its attributes, namely data robustness, parameter sensitivity, and security covering adversarial examples, are introduced. The evaluation results indicate that the proposed trustworthiness attributes are crucial to evaluate the trustworthiness of DNN for this 6G application.

We derive an analytical expression of the error vector magnitude (EVM) in terahertz (THz) communication links affected by two performance limiters, namely antenna alignment error and the receiver's in-phase/quadrature imbalance (IQI). Through the sole use of elementary functions, we show how to compute the EVM in closed-form approximately, but accurately and efficiently. Furthermore, we show that antenna alignment errors and IQI can severely degrade the performance of THz communications. Investigations of the special and limiting cases of the regimes pertaining to high signal-to-noise ratio (SNR) and low antenna alignment error variance are carried out, where we also demonstrate the possible separation of the IQI and THz channel effects on the performance of the EVM.

TeraHertz (THz) communications can satisfy the high data rate demand with massive bandwidth. However, severe path attenuation and hardware imperfection greatly alleviate its performance. Therefore, we utilize the reconfigurable intelligent surface (RIS) technology and investigate the RIS-aided THz communications. We first prove that the small-scale amplitude fading of THz signals can be accurately modeled by the fluctuating two-ray distribution based on two THz signal measurement experiments conducted in a variety of different scenarios. To optimize the phase-shifts at the RIS elements, we propose a novel swarm intelligence-based method that does not require full channel estimation. We then derive exact statistical characterizations of end-to-end signal-to-noise plus distortion ratio (SNDR) and signal-to-noise ratio (SNR). Moreover, we present asymptotic analysis to obtain more insights when the SNDR or the number of RIS’s elements is high. Finally, we derive analytical expressions for the outage probability and ergodic capacity. The tight upper bounds of ergodic capacity for both ideal and non-ideal radio frequency chains are obtained. It is interesting to find that increasing the number of RIS’s elements can significantly improve the THz communications system performance. For example, the ergodic capacity can increase up to 25% when the number of elements increases from 40 to 80, which incurs only insignificant costs to the system.

Wireless communications in the low terahertz band (0.1 THz-1 THz) is a promising candidate to enable ultra-high-rate vehicular networks beyond 5G. The successful design and adoption of such systems require a deep understanding of the low THz channel specifics in complex vehicular scenarios. In this paper, a comprehensive measurement campaign is reported with the aim of analyzing the wave propagation at 300 GHz in typical vehicular deployments. Following a modular approach, the generic vehicular scenario is decomposed into basic propagation setups that are further analyzed in detail. The obtained measurement data are then applied to derive the mathematical approximations that characterize the low THz band channel properties for each scenario. Finally, the combination of measurement and modeling results is used to identify the critical propagation effects that has to be accounted for in the applied studies. The presented approach, raw and processed data, as well as the contributed analysis, serve as building blocks for future analytical and simulation tools to model prospective vehicular communication systems in the low THz band.

In this paper, measurements of the attenuation by the window and fuselage of an aircraft for Terahertz communications are presented. The measurements are performed at 300GHz using an ultra wide-band sub-mmWave channel sounder in a Boeing 737. They are subdivided into a characterization of perpendicular and oblique incidence, respectively, with regard to the azimuth angle. Before presenting the results, the different measurement setups are described. The results suggest a minimal attenuation of -11.01 dB by the window for perpendicular incidence whereas no specific angle dependency could be identified.

This paper investigates the advantages of using communication supported by information from vehicle sensors to improve the performance of the High-Density Platooning (HDPL) application. HDPL is one of the most promising applications in the field of cooperative driving. The goal of this application is to improve fuel and road efficiency without impairing safety. The level of efficiency improvement depends on the instantaneous channel quality. Strong multipath components, which arise from other vehicles, traffic signs, and surrounding buildings in such a highly dynamic vehicular environment, significantly influence the instantaneous link quality between communicating vehicles in a platoon. An emerging concept of vehicle sensor-aided predictive communications has shown its potential to improve direct-link communication. In this paper, the applicability of this approach is evaluated in terms of inter-vehicle distance error, which reflects the difficulties that the control algorithm has to cope with in the communications conditions. The simulation results show that the proposed sensor-based approach significantly improves the platoon performance even if affected by multiple dynamic scattering reflections at the same time.

Powered by the Internet of Things, the vehicular ad-hoc networks are expected to evolve into the Internet of Intelligent Vehicles in which each vehicle can be much more efficient in various vehicular and transportation applications. In order to realize this vision, a seamless low-latency and ultrareliable vehicle-to-vehicle (V2V) communication network is required. Thus, it is of importance to characterize the V2V channels in various realistic environments, especially when the line-of-sight between transmitter (Tx) and receiver (Rx) is obstructed. In this paper, we characterize obstructed V2V channels in the 5-GHz band through measurement-calibrated ray-tracing (RT) simulations. To begin, the main objects in the real world are divided into two groups: 1) the small-scale structures (e.g., lampposts, traffic signs, etc.) and 2) the large-scale structures (such as buildings and ground). Then, we integrate the radar cross sections of the small-scale structures into our RT simulator through a framework based on high frequency prediction techniques. For the large-scale structures, we calibrate the electromagnetic and scattering parameters of the large-scale structures through V2V channel measurements. After such integration and calibration, extensive RT simulations for V2V channels with Tx and Rx located on vehicles traveling in the opposite or same direction are realized with various antenna deployments in urban and open space environments, with and without sloped terrain. Based on the RT results, we characterize the path loss, shadow fading, and delay spread of the channel for each case, and show agreement with measured results in the literature for all these channel characteristics.

The terahertz (THz) communication utilizes the frequency spectrum above 300 GHz and is widely considered as a promising solution to the future high-speed short-range wireless communication beyond millimeter wave communication. While providing tens of gigahertz bandwidth, it is subjected to high-propagation path loss, inter-symbol, and inter-user interferences. The massive multiple-input-multiple-output (MIMO) can be applied to address these problems by cooperation between many access point antennas. However, the THz channel characteristics, including high-propagation path loss, frequency selectivity, and a big number of samples per channel impulse response, require carefully tailored algorithm for massive MIMO signal processing. In this paper, we propose a single carrier minimum mean square error precoding and detection algorithm for frequency selective THz channels. The MIMO signal transmission is described with the block matrices. A gain control heuristic is introduced to reduce the complexity. The sparsity property of the channel is utilized to construct sparse channel matrices and the least square QR algorithm is applied to efficiently solve the problems. Besides the uniform antenna array, the hybrid array consisting of several subarrays is considered as well. The simulation results show that the massive MIMO array can provide a satisfactory performance in terms of bit error rate.

A measurement campaign has been carried out in a reference indoor environment - a medium-size meeting room - using an ultra-wideband channel sounder operating at 3 different frequency bands: 10 GHz, 60 GHz and 300 GHz. Automatic rotational units are used at Tx and Rx side to perform a full horizontal scanning with directional antennas, in order to achieve a double-directional channel characterization. Preliminary results show that multipath is mainly affected by few single or double-bounce components, and significant contributions may come from objects other than the walls, e.g. TV monitor and entrance door. Most of the contributions are clearly identifiable at all the considered frequencies, although they appear to be stronger at 60 GHz compared to 10 GHz. The radio channel's multipath richness appears to be frequency dependent, and in particular it decreases when comparing 60 GHz to 300 GHz.

In recent years, a combined utilization of ad-hoc communication and cellular mobile radio systems has been considered for vehicular networking in future Intelligent Transportation Systems (ITSs). The development of hybrid system protocols, algorithms and architectures require comprehensive performance investigations typically carried out by means of simulations. The main contribution of this article is to introduce a top-down design methodology for building realistic simulation scenarios tailored to the requirements in vehicular communication and suitable for multiple levels of abstraction in simulations. Within this paper the focus is set on the example city of Doha, Qatar: Building upon a macroscopic layer including static environmental data and a realistic cellular network, it is shown how to embed microscopic sub-scenarios with detailed modelling of individual user mobility into the macroscopic world. Exemplary sub-scenarios are derived with respect to applications considered for ITS. As a proof of concept, in the first part of the article, the design process is demonstrated for an LTE network in conjunction with IEEE 802.11p based vehicular communication. In the second part of the article, exemplary individual simulation results at the link-level are presented for both considered radio technologies.

The millimeter and sub-millimeter wave communication is a promising solution to future indoor multi-gigabit wireless communications because of its huge available bandwidth. One of the key difficulties is the hu- man blockage effect since the human body can no longer be considered as being "transparent" as at lower frequencies. In this paper a study of statistical characteristics of this problem is presented. At first, broadband measurements of human blockage are provided. Afterwards, a realis- tic mobility model for indoor movements of humans is adopted and elliptic cylinders are applied to approximate human bodies in ray-launching simulations. Consequently, the distributions of Line-Of-Sight (LOS) path and blockage durations as well as blockage numbers are obtained by simulations. Finally, the system performance in presence of the distributed antennas is evaluated.

Wireless communication became a key technology in the transportation domain. An increase of efficiency and safety can be achieved by connecting all traffic participants. In the railway domain wireless communication could enable new applications. In this contribution we focus on train-to-train (T2T) communication and investigate the propagation conditions. In typical railway environments different types of objects along the track highly influence the propagation channel and, in turn, the performance of wireless T2T communications. Therefore, the characterization and modeling of the propagation effects are indispensable. In comparison to cellular or vehicle-to-vehicle communication, T2T propagation is hardly investigated. In this paper we present how key parameters of the multipath components (MPCs) of the channel impulse response can be estimated. The estimation is based on measurement data. We estimate delay and Doppler of single-bounce MPCs and estimate the location of the corresponding scatterers.

A promising application of cooperative driving is the exchange of safety-relevant time-critical information. With the support of communications, vehicles can improve safety by communicating the output of their advanced driver-assistance systems. The level of improvement is however very dependent on the instantaneous channel quality at the time of the information exchange. The configuration of the communication partners, but also the other vehicles, traffic signs and buildings that compose the surrounding dynamic environment, create strong time-varying multipath components. Existing measurement campaigns show that such components can bring positive and negative impacts on the communication link depending on the instantaneous properties of the surrounding environment. An emerging concept of vehicle sensor-aided communications has shown its potential to improve direct-link communication via utilizing information about the surrounding environment provided by vehicle sensors. In this paper we show that the sensor-aided predictive communications can improve the safety in cooperative emergency braking situations. The performance of this approach is evaluated in terms of application related metrics variation compared to various channel conditions: perfect, realistic vehicular channel model, and the blocked channel. Simulation results show that the proposed sensor-based approach significantly improves the emergency braking performance for both the head-on and rear-end collision scenarios.

Angle of arrival (AoA) estimation is required by adaptive directive antennas in order to realize a high antenna gain, which is necessary for future indoor terahertz communications due to its extremely high path loss. This paper proposes an AoA estimation algorithm using belief propagation in a dynamic scenario, where the user equipment (UE) is moving during the data transmission, based on the space-time correlations of AoA change. The temporal correlation of AoA change is due to the limited moving speed and statistical movement pattern. Furthermore, if we have distributed antennas or hybrid massive multiple-input-multiple-output (MIMO) array, the AoA changes of different antennas reveal spatial correlation because all the AoA changes are caused by the same spatial displacement of UE. This spatial correlation is utilized in this paper to further improve the estimation accuracy by passing messages between antennas and combining the intrinsic estimate by each antenna and extrinsic information from other antennas. In order to demonstrate the algorithm performance, a distributed antenna system and a hybrid massive MIMO array (an array of multiple directive antenna arrays) are considered as application scenarios. The simulation results show that the cooperative estimation brings significant advantage in both scenarios in respect of mean effective antenna gain and level crossing rate.

Railway, subway, airplane, and other transportation systems have drawn an increasing interest on the use of wireless communications for critical and noncritical services to improve performance, reliability, and passengers experience. Smart transportation systems require the use of critical communications for operation and control, and wideband services can be provided using noncritical communications. High speed train (HST) is one of the best test cases for the analysis of communication links and specification of the general requirements for train control and supervision, passenger communications, and onboard and infrastructure wireless sensors. In this paper, we analyze in detail critical and noncritical networks mainly using the HST as a test case. First, the different types of links for smart rail transportation are described, specifying the main requirements of the transportation systems, communications, and their applications for different services. Then, we propose a network architecture and requirements of the communication technologies for critical and noncritical data. Finally, an analysis is made for the future technologies, including the fifth-generation (5G) communications, millimeter wave (mmWave), terahertz (THz), and satellites for critical and high-capacity communications in transportation.

This demonstration shows several use cases of the Simulator for Mobile Networks (SiMoNe). It starts with a network planning and optimisation context for large-scale urban scenarios and hyper-dense small-cell deployments and comes to the evaluation of SON- and management functionality in aforementioned scenarios. Five different SON functions will be shown, namely MRO, MLB, LTE/GSM DSA, Wi-Fi/LTE TS and LTE/V2X TS.

Reliable vehicular communication is considered an important precondition for future intelligent transportation systems (ITSs). Recently, a combination of ad-hoc direct communication and infrastructure based cellular networks are considered to enable seamless connectivity and sufficient Quality of Service (QoS) for all types of vehicular applications. Within this paper a novel algorithm to enable data traffic steering between ad-hoc IEEE 802.11p based dedicated short range communication and LTE for Vehicle-to-X (V2X) communication is presented. Based on the system-level evaluation of cell loads and radio channel congestion the network based performance of the proposed algorithm is analyzed and compared to the conservative approach of using exclusively IEEE 802.11p for message dissemination. First simulation results in a realistic urban intersection scenario show significant improvement of the quality of service.

User mobility in mobile radio networks strongly affects the performance of the whole system. Thus, it is of upmost importance to model mobility patterns as realistically as possible. Several publications w. r. t. individual (realistic) user movements have been made. However, especially in urban scenarios, user mobility is often correlated. In public transportation systems (metro, bus, etc.) the motion of many users is bound to the same vehicle, leading to a far different system performance (e.g. cell load, number of handovers, etc.). Therefore, a new correlated group mobility model is presented in this paper. Results show that the system performance compared to individual user movements is significantly different.

The increasing complexity in today's mobile networks enforces the need for more sophisticated and more realistic simulation scenarios. It is a pre-requisite to cope with the effects in real heterogeneous networks in order to allow the exploitation of their inherent heterogeneity. This paper describes the first version of a common "ready-to-use" simulation environment in the city of Hannover: A complete LTE network, which has been modelled for the entire city area. In addition, sophisticated modelling approaches for user mobility patterns have been employed. Furthermore, provisioning a common scenario ensures the comparability of simulation results, which are based on this scenario.

In this paper, a realistic urban scenario for a hyper-dense small-cell network deployment is presented, using full 3D building models and 3D ray-optical pathloss predictions. This network is compared to a similarly dimensioned 3GPP-like deployment, in order to emphasize the correlations and the differences between these two environments. Furthermore, different expansion stages of the small-cell deployments in both environments are discussed with respect to the coverage and interference situations.

Unlike solid obstacles, the excess loss of semiclosed obstacles (SCOs) can be considerably overestimated by directly applying existing diffraction models, i.e., multiedge diffraction models. By regarding the propagation situation as a superposition of the cases of the “Open Field” and the “Closed Obstacle,” this paper presents a simple way to model the excess loss of SCOs that widely exists in intelligent transportation systems. By estimating two weight coefficients according to the specific situation, this model structure can be applied to different SCOs. To illustrate our modeling concepts, two typical cut-and-cover tunnels in high-speed railway are studied in detail. Combining this case with our previous implementations for train stations and crossing bridges, a complete set of coefficients for the excess loss of the main SCOs in railway settings is presented. This case study shows that the proposed approach provides an effective and fairly simple way to include various SCOs in the network planning, simulation, and design of communication systems. As our approach has determined the coefficients empirically, the proposed model structure can provide the foundation for future work that aims to streamline the excess loss prediction via estimation of coefficients either analytically or via a reduced set of measurements.

Today's networks become increasingly complex due to the presence of multiple radio access technologies (RATs) and various network layers. The introduction of Self-Organising Network (SON) Functions that continuously modify the network's operating point support the operator on dedicated network management tasks, but need to be configured themselves in order to allow for achieving objectives for the mobile network. Another complexity that arises is that those operator objectives also change depending on the environment and the current conditions of the mobile network. It is therefore indispensable to introduce a SON management automation entity. A corresponding solution is introduced in this paper.

The network management of heterogeneous mobile networks relies on a profound network topology. This includes a realistic network deployment and realistic pathloss predictions to account for the irregularities in the network. To derive relevant key performance indicators in such networks, mobility models are needed that account for individual user movements in the network and produce user individual performance indicators, e.g. handover events. A multitude of mobility models are known that are supposed to address the different characteristics of human movement patterns and behaviours of certain user groups, such as vehicular, indoor or pedestrian users. To approach the latter one, a new pedestrian mobility model based on real geographical data is presented in this document.

A Self-Organising Network (SON) represents an approach where the optimisation of a mobile radio network is automated through a set of independently operating SON functions. These SON functions, however, require to be configured in order to allow for an optimised network performance with respect to technical objectives defined by the network operator. The SEMAFOUR demonstrator shows a concept for SON management based on operator objectives, where the SON function configuration is performed in an automated way. The demonstrator illustrates the different aspects and complexity of the management of SON in a heterogeneous network.

Car2X-Communication is a method for data exchange between vehicles and infrastructure units to increase traffic safety and efficiency. Usually data processing and control is performed within the vehicle i.e decentralized. Centrally organized systems hardly get any attention in latest research, although they have many advantages. Since communication systems are improving, even safety-critical centralized systems become realistic. In this paper we present the technical feasibility of centralized Car2X-Systems based on LTE. Exemplarily, we investigate a Server-based Adaptive Cruise Control System (SbACC), whereby the longitudinal behavior of vehicles is controlled by a central server over LTE. Additionally we identify several methods with which the requirements for delay and bandwidth can be relaxed, such that a sufficient performance of the SbACC can still be guaranteed. The evaluation is then performed based on the simulation of scenarios with realistic movement and communication, yielding a maximum required bandwidth of the SbACC in downlink of 2.15% in an urban and 9.6% in a suburban scenario.

Today's cellular radio networks offer so many parameters that can be configured, that it is virtually impossible to configure such a system manually. To overcome this problem, operators and vendors put their trust in SON. But still, how can a SON function evaluate all potential parameter variations in short time and in a realistic manner in order to make the right decision? The herein presented Simulator for Mobile Networks (SiMoNe) is capable of performing system-level simulations within realistic network scenarios. By offering the capability of parallel simulations of parameter variations, a multitude of different settings can be evaluated. It allows for simulations based on time variant maps as well as for simulations with a large number of individual user traces which follow different mobility pattern like vehicular or indoor mobility.

This experience session track paper presents first findings and results of the simulator implementations, developed for the European funded FP7 SEMAFOUR project. First, the SEMAFOUR concept of Policy-bases SON Management (work package 5 - Integrated SON Management) is introduced, with a focus on those parts that have been implemented. Furthermore, the SON Functions that built the basis for the simulations are briefly described on slide 5. The simulation scenario and environment is explained in detail from slide 6 to 8. The sequential steps that have been taken in the simulation work and the findings within these steps are explained in detail from slide 9 to 11.

The demonstrator shows a self-management system for heterogeneous mobile radio communication networks as developed in the European FP7 SEMAFOUR project. The self-management system uses operator-defined objectives regarding, e.g., network capacity, network load, or network robustness, to automatically configure and control the operation of Self-Organising Network (SON) Functions. The SON Functions are instrumented as to contribute to the operator objectives. Changing objectives or their priorities leads to a reconfiguration of the SON Functions. The demonstration uses three SON Functions, namely, Mobility Load Balancing, Mobility Robustness Optimisation and Coverage and Capacity Optimisation, and the impact of changing objectives can be traced in the demonstrator's realistic network scenario and the network's Key Performance Indicators.

In this paper, a physical (PHY) layer performance comparison for 3GPP Long Term Evolution (LTE) and IEEE 802.11p in a realistic urban street intersection scenario is presented. For this approach standard compliant link level simulation tools in combination with ray-optical channel modeling are utilized. Results are analyzed with respect to an intersection collision warning application where a suitable performance metric is derived to analyze the individual performances with respect to the packet error ratio in the downlink. In the absence of a line of sight (LOS) path for a Vehicle-to-Vehicle (V2V) link, the results show promising potential of LTE to outperform a dedicated IEEE 802.11p based communication link even when considering full buffer intercell-interference condition.

This document describes an approach to calculate realistic spatial user and traffic distributions for cellular networks with time varying usage intensities per land-use class. The distributions account for the common human behaviour for different times of the day and different days of the week. In combination with the coverage area of the cell as well as the land-use classes in the respective area, an estimation of the tempo-spatial distribution is achieved. Performance measurement (PM) data on cell level is used for weighting these distributions according to the actual traffic situations in an existing network.

An analytical 3D ray-launching method using arbitrary polygonal shapes for wireless propagation prediction is introduced within this document. The algorithm is significantly advanced compared to other ray-launching techniques, since the actual ray-casting methodology is based on vertices of the geographical data and not on a brute-force manner which most often leads into irrelevant directions in space. As a valu-able feature, the herein presented approach does not rely on any kind of spatial resolution. It is neither limited to certain discrete angle increments like conventional ray-launching, nor is it suffering from low resolutions or the need for sub-sampling like conventional ray-tracing.

High-speed railway (HSR) brings convenience to peoples' lives and is generally considered as one of the most sustainable developments for ground transportation. One of the important parts of HSR construction is the signaling system, which is also called the “operation control system,” where wireless communications play a key role in the transmission of train control data. We discuss in detail the main differences in scientific research for wireless communications between the HSR operation scenarios and the conventional public land mobile scenarios. The latest research progress in wireless channel modeling in viaducts, cuttings, and tunnels scenarios are discussed. The characteristics of nonstationary channel and the line-of-sight (LOS) sparse and LOS multiple-input-multiple-output channels, which are the typical channels in HSR scenarios, are analyzed. Some novel concepts such as composite transportation and key challenging techniques such as train-to-train communication, vacuum maglev train techniques, the security for HSR, and the fifth-generation wireless communications related techniques for future HSR development for safer, more comfortable, and more secure HSR operation are also discussed.

In a realistic high-speed railway environment, the track, terrain, vegetation, cuttings, barriers, pylons, buildings, and crossing bridges are the main sources of reflection, diffraction, and scattering. Moreover, the radiation pattern and the polarization of the transmitting and receiving antennas considerably influence the propagation. This paper presents a deterministic modeling approach covering all the effects in a realistic highspeed railway environment for the first time. The antenna influence and the mechanisms of transmission, scattering, and reflection are evaluated by developing a 3D ray-optical tool. The diffraction loss is obtained by the multi-edge diffraction models using raster databases. This approach compensates the limitation of the existent empirical and stochastic models used for the high-speed railway, and promotes the deterministic modeling towards to the realistic environment. Therefore, it allows a detailed and realistic evaluation and verification of the train control communications systems.

The development of self-management solutions for (multi-technology, multi-layer) mobile communication networks is driven by their increasing operational complexity. Initial stand-alone SON (Self-Organizing Networks) solutions are already available, but are not sufficient to handle the networks of tomorrow. In this paper we present our approach at developing a unified management framework that integrates the existing and future advanced SON functions across several radio access technologies. The envisioned self-management system comprises (i) an integrated SON management system, in charge of policy transformation/supervision and conflict detection/handling; (ii) advanced multi-RAT/layer SON functions; and (iii) a Decision Support System providing measurement-based assistance for residual operational tasks, such as timely recommendations for targeted new site deployments.

This paper presents the results of an accuracy assessment of a deterministic channel model for vehicle-to-vehicle (V2V) communications. Channel simulations obtained from the ray-tracing model developed by TU Braunschweig are compared to data gathered during the DRIVEWAY V2V channel measurement campaign at 5.6 GHz in the city of Lund in summer 2009. The analysis focuses on PDP and channel gains in an urban four-way intersection scenario. Despite some implementation-based limitations of the ray-tracing model, a very good agreement between simulation and measurement results is achieved. Most relevant power contributions arising from multiple-bounce specular reflections as well as from single-bounce non-specular reflections are captured by the deterministic model. We also discuss the question to what extent roadside obstacles like traffic signs, parked cars or lamp posts have to be considered when characterizing the V2V channel.

Providing the basis for fast system simulations and the adequate design of upcoming THz communication systems, a novel stochastic 300 GHz indoor channel model is introduced. It combines both the modeling in time as well as in frequency domain in order to account for the significant frequency dispersion of ultra broadband THz channels. Not only amplitude, phase and temporal, but also spatial channel information is considered. That way, MIMO systems as well as novel antenna concepts can be simulated. Verified and calibrated frequency domain ray tracing simulations in an office scenario provide the data basis for the derivation of model parameters. Model channel realizations are tested against ray tracing predictions and channel measurements. A complete scenario-specific parameter set is given for the considered environment, so that the model can be implemented for further use and future THz communication links can be designed under consideration of realistic propagation conditions.

During the last few years, vehicle-to-vehicle (V2V) wireless communication has become a key objective for enabling future cooperative safety applications, such as intersection collision warning. In this paper, we present the results of a 5.9 GHz V2V performance measurement campaign at four different urban intersections under NLOS conditions using commercial off-the-shelf wireless interface cards which meet the 802.11p and ITS-G5 specifications. Particularly, we quantify the packet delivery ratio (PDR) and received signal strength indication (RSSI) levels associated with different scenario conditions with respect to vehicle positioning, intersection geometry and traffic density. We determine reliable communication ranges which constitute an important metric for V2V collision avoidance applications.

New ultra high data rate systems in the 60 GHz band, especially those targeting high definition video indoor transmission, have a strong requirement for Quality of Service to prevent link outage, and this has to be performed at the MAC level. This paper describes a new simulation platform for these ultra high data rate wireless systems. This new tool models the complete wireless system, including a ray tracing based channel model, smart antennas model, and a physical layer model suitable for MB-OFDM and Single Carrier basebands. In addition, it includes the modeling of RF front-end properties and a MAC layer with beamforming capability for Quality of Service. In this paper we also highlight one use case of this simulation tool as a mean to compare the performance impact of different antenna arrays in a high definition video streaming application.

Among the techniques proposed to reduce interference in cellular ODFMA networks, base station cooperation (BSC) is currently the technique known to achieve the highest network throughputs. Its deployment however is vastly expensive and cheaper alternatives are expected to play an important role in future wireless access standards. This contribution introduces relay-augmented networks based on the novel paradigm of (m,n)-relaying and shows how, by reaching performances close to those achievable by employing BSC, these qualify as an especially interesting option among the aforementioned alternatives.

Handover parameter optimization is a self-optimizing network (SON) use case that promises significant performance improvement of the radio network. The basic idea is to adapt the handover control parameters, hysteresis and time-to-trigger, to the individual cell situation, in terms of e.g. the building density, cell environment and degree of user mobility. The aim is to reduce the number of handover failures, ping-pong handovers and radio link failures. We propose an handover parameter optimization algorithm that tunes the hysteresis and time-to-trigger in iterative steps and show the system performance improvement with it in both a realistic and a hexagonal simulation scenario.

Today, the network operators have to perform drive/walk tests when planning and optimizing their networks. These drive/walk tests are costly and time-consuming, cover only a limited part of the network, and capture only a snapshot in time. To overcome these difficulties, the mobile devices in the network can be used as probes by continuously reporting the observed service quality together with their positions. In this paper, we introduce the concept of X-map estimation, which is a function that processes the measurement data into a geographic map with overlay performance information, referred to as an X-map. By continuously processing measurements, the X-map estimation function approximates the spatial characteristics of the network performance and therefore reduces the costs of drive/walk tests. Additionally, X-maps can be used by Self-Organizing Networks (SON), especially in functionalities that address optimization of coverage, capacity, and quality. In this paper, we introduce two approaches for determining X-maps and we analyze the influence of the applied positioning method on the accuracy of the X-maps. We show that the accuracy of the positioning technique can have a significant impact on the accuracy of the X-map.

Information about the radio coverage is essential for network planning and network optimization. In order to obtain the necessary information, planning tools are used which are in some aspects inaccurate due to, e.g., inaccurate input data, simplifications in the applied propagation models, and changes in the environment or traffic distribution. Thus, the planning tools have to be optimized using measurement campaigns. For this, drive/walk tests have to be performed which are not ideal since only a limited part of the network can be covered due to the costs and access restrictions, and only a snapshot of the conditions in the field is captured. Therefore, we introduce the concept of the X-map estimation function which continuously monitors the network and estimates the spatial network performance by processing the UE reports in a geographic map with overlay performance information, referred to as an X-map. Two different approaches for creating X-maps are evaluated in this paper. We analyze the influence of the positioning accuracy, the UE measurement accuracy, and the number of measurements taken on the accuracy of the resulting X-maps. We show that the influence of the different factors on the accuracy of the X-maps depends on the used approach and that the positioning accuracy and the number of measurements taken have the largest impact.

This paper presents performance evaluation results of different linear diversity combining techniques that have been applied to IEEE 802.11p based Car-to-X (C2X) communication systems. More precisely, we employed the Selection Combining (SC), the Equal Gain Combining (EGC) and the Maximum Ratio Combining (MRC) algorithms to systems with multiple receiver antennas and compared the resulting performance to that of single-receive antenna systems. Concerning the great challenges of typical C2X propagation channels that go along with a strong time variance and long multipath delays, the use of multiple receive antennas in combination with adequate signal combining algorithms can clearly improve the reliability of the communication system even under poor Signal-to-Noise Ratio (SNR) conditions. Based on physical (PHY) layer simulations, the achieved performance of different diversity combining techniques has been evaluated using stochastic models of double-selective fading channels.

Future communication systems for car-to-x (C2X) applications have to meet stringent requirements regarding reliability issues. Channel estimation (CE) - as one of the key tasks that affect the system performance - has to be able to cope with the rapidly changing channel conditions. Applying a Wiener filter (WF) is one very efficient method to reduce the estimation error of any channel estimation approach. This paper deals with design aspects of Wiener filter coefficients and their impact on the system performance. Parameters like noise variance, maximum excess delay of the channel impulse response as well as the assumed shape of the power delay profile (PDP) are considered. The resulting performance benefit of different filter designs is evaluated by means of IEEE 802.11p physical (PHY) layer simulations.

Mobile operators are facing capacity problems due to the rising demand for data services, particularly in indoor environments. In order to ensure high data rates, femto cells will be part of the solution. Since they are operated by the customers, the influence of a network operator on the installation location is limited. Thus, femto cells have to be taken into account in future network and handover planning where the level of detail in modeling is crucial. A simple prediction model is not detailed enough to simulate spatially very limited femto cells. Therefore, this paper compares two different levels of complexity in the prediction of femto cells and their resulting effects on handovers as well as on call drops in long-term evolution (LTE) networks under various configurations of the handover parameters.

This paper presents a self-optimizing algorithm that tunes the handover (HO) parameters of a LTE (Long-Term Evolution) base station in order to improve the overall network performance and diminish negative effects (call dropping , HO failures). The proposed algorithm picks the best hysteresis and time-to-trigger combination for the current network status. We examined the effects of this self-optimizing algorithm in a realistic scenario setting and the results show an improvement from the static value settings.

In order to be able to investigate future Vehicle-to-Vehicle (V2V) communication systems, the need for realistic simulation environments is increasing. Especially, the integration of realistic antenna models which account for several non-ideal effects such as e.g. mutual coupling or the influence of a finite ground plane size is important. In this paper, a comparison of two possible multiple-input and multiple-output (MIMO) antenna configurations consisting of three antennas mounted on the car at different positions is carried out using a complex simulation environment. In particular, the receive diversity and the MIMO capacity are considered since the link robustness as well as the increase of spectral efficiency are important issues.

Accompanied by the continuous progression of the maturity of car-to-x communication protocols and corresponding system architectures, the need for integrated network simulation approaches which consider realistic channel modeling on the one hand and appropriate mobility models on the other hand becomes more and more observable. Moreover, in order to analyze the impacts of car-to-x applications on the behavior of vehicles, an interconnection of different simulation tools is needed. In this paper, a concept for the interconnection of network, channel and road traffic simulations is presented. This concept relies on network simulation based on the open source simulator OMNeT++ and the INET Framework, which utilizes a coupling to the well-known road traffic simulator SUMO. In order to characterize the radio channel, an interconnection between OMNeT++ and a ray optical propagation model is being established. Furthermore, some preliminary simulation results are presented which serve as a proof of concept.

The complexity of current mobile radio networks (GERAN, UTRAN) has raised a demand for automatic planning procedures and a call for self-planning in future systems (LTE second phase). However, for any kind of automatism, reliable input data is necessary and, among other things, derivable from measurements of statistical counters collected by the operation and maintenance centre (OMC). Mobility information is required by planning procedures concerning registration areas, handover (HO) parameters, etc., in particular, and can mainly be derived from HO statistics. For a new network plan, this information has to be estimated. In this paper, an estimation method for HO attempts based on corresponding HO measurements from the network in operation is proposed. The associated model is based on graphs representing the interdependency of cells. The order of neighbourhood is introduced as a weight function for the edges. For appropriate weighting during estimation a general Pareto probability density function is determined from HO measurements. The analysis of the estimation performance is carried out by comparing the estimation values with corresponding OMC measurement data. Both the required network data and the OMC measurement data are provided by a real network.

The Saleh-Valenzuela multipath channel model (SVmodel) is often used for the modeling of communication channels in confined environments . The model assumes multipath components (MPC) arriving at the receiver in clusters. Instead of identifying clusters from the power delay profile (PDP) via visual inspection as proposed in , this paper proposes a systematic algorithm for cluster identification in a large wide-bodied aircraft cabin. The performance of the SV model implemented with the proposed best fit algorithm is compared in empty and occupied aircraft cabin scenarios.

Car manufacturers have been showing great interest in setting up ultra-wideband (UWB) systems due to the offered high data rates. In this paper, the fundamental features of the in-car UWB channel in terms of large-scale and small-scale parameters are investigated. These values are based on measurement data collected with a vector network analyzer (VNA) in the frequency band of 3-8 GHz. With the aid of the measurements, simple preliminary empirical models have been derived describing both, path loss as well as small-scale features of the channel. The results are shown for LOS and NLOS situations as well as for an empty car and a car occupied with persons.

Automatic methods for location area code (LAC) planning in mobile networks require prediction values of the expected signaling traffic (paging, location update, etc.) that have to be provided by signaling traffic models. It is a main objective that the input data of the methods and models are based on performance measurement values from the operations and maintenance center (OMC). In this paper, the performance of redistribution of measurement values for cell planning is investigated. Cell assignment probabilities (CAP) are used to distribute measurement values over cell areas. Then, CAPs of a new cell plan are used to reassign the former measurement distributions resulting in cell prediction values. The analysis of the prediction performance is carried out by comparing the mobile terminated call (MTC) prediction values based on one network status with OMC measurement values of a following network status. Network and OMC measurement data are provided by a real network.

Automatic methods for location area code (LAC) planning in mobile networks require prediction values of the expected signaling traffic (paging, location update, etc.) that have to be provided by traffic and mobility models. Modeling can be based on a learning data set consisting of geographic information (population distribution, land use) as input data and performance measurement values from the operations and maintenance center (OMC) as output data. In this paper, the performance of fast modeling methods based on classification and regression trees (CART) is investigated and compared to linear regression analysis. It will be shown that a combination of these two methods shows modeling results of arbitrary accuracy. The analysis of the modeling performance is carried out by comparing the mobile terminated call (MTC) prediction values with OMC measurement values from a real network.

Analysis results of commonly used propagation models applied to UMTS ultra high sites (UHSs) in urban environment are presented. Differences between predicted values and measurements for two specific locations are presented as functions of the distance between the base and mobile station as well as of the elevation angle at the BS. An assessment of the validity range of the different propagation models is done and a proposal for the extension of the models is made

In this paper a new approach for the calibration of electromagnetic material parameters (permittivity) of 3D ray tracing prediction model at 2.4 GHz is presented. The calibration procedure is based on measurements of the channel impulse response using cross-correlation techniques and the 802.11b preamble. Further developments of a method, which has been published earlier, are presented. The analysis of the permittivity of different walls determined from a short measurement campaign is shown.

In this paper a couple of simple expressions for calculating the frequency re-use factor describing the uplink interference situation in WCDMA radio networks are derived. The derivation of these heuristic expressions is based on a series of Monte Carlo simulations performed in a hexagonal network with inhomogeneous traffic distributions. it is shown that only specific areas within each cell of the first two tiers contribute significantly to the uplink interference, which reduces the complexity in the network quality assessment. This information can be used to speed up the evaluation of solutions in automatic planning algorithms.

A run-time efficient three-dimensional radio propagation prediction model is presented. The model allows mobile network operators to predict the outdoor and the outdoor-to-indoor coverage in dense urban areas using one general prediction model. It integrates almost all relevant propagation phenomena in dense urban areas with an accuracy comparable to the results of dedicated prediction models. The required high resolution building data is stored in vector as well as raster format. Depending on the terrain processing task, the format resulting in the shorter run-time is employed. A huge amount of measurements from the Global System for Mobile Communications 1800 network of E-Plus have been used to derive the heuristics and empirical correction factors included in the model. It is shown that the prediction accuracy can be improved significantly by considering vegetation effects and multipath propagation. Measurements justify multipath propagation only up to a distance of measurements from the base stations (BSs) in an dense urban environment. This is another source of significant run-time savings. Consequently, the prediction time of large areas decreases dramatically by neglecting multipath effects at these distances. A semiempirical building penetration extension is used to derive indoor predictions for each floor based on outdoor predictions at ground-level combined with a height gain model. An additional deterministic component is incorporated in case the BS and (parts of) the building are in line of sight. Preliminary tests show a sufficient match between the measurements and the outdoor as well as the outdoor-to-indoor predictions.

Conventional wave propagation models for radio networks predict field strength levels only. Wideband wave propagation models however, include algorithms to characterize the radio channel. For digital radio systems the BER of the unprotected radio channel is an important parameter. In the approach presented in this paper, the influence of multipath propagation on different digital modulation schemes is investigated. The calculations are based on a 3D wave propagation model, which yields a field strength-delay spectrum (FDS). The FDS is defined by amplitudes and delays of incident waves, which contribute to intersymbol interference due to multipath propagation. Two algorithms for computation of the BER evaluating the FDS, for both linear and non-linear digital modulation schemes are presented. This paper focuses on GMSK- and PSK-modulation schemes, which are used in digital mobile radio systems (DCS1800, GSM, DECT) as well as in digital audio broadcast systems (DAB). An analysis of the performance of the different modulation schemes in difficult terrain is shown.>

Network planning in mobile communications requires a realistic description of the propagation phenomena. Common wave propagation models for rural areas consider mainly the influence of topography. However, shadowing effects of the morphography in the vicinity of the mobile cause additional path loss. Usually this path loss is accounted for either by empirical corrections or by additional knife edges. In this paper new ray optical approaches for the calculation of the additional path loss for mobile locations within forested or urban environments are presented. For these situations typical macro situations are defined. In the case of urban environments the additional path loss is determined by means of the Uniform Theory of Diffraction whereas in forested areas a lateral wave propagation approach is used. The model is applied to an existing GSM-network. The results achieved by this model show good agreement with both wideband and narrowband measurements.>

Mobile communication links are severely influenced by propagation effects. Wave propagation in the VHF/UHF frequency range over natural and man-made terrain is strongly dependent on topography and morphography. Propagation modeling is based on a ray-optical approach. Wave interactions, like diffraction and scattering, over the propagation path are described by the uniform theory of diffraction (UTD) and physical optics (PO). Propagation models for rural and urban areas are presented for 2-D and 3-D ray tracing. Near-range models apply to the corresponding areas in forest and urban sites. The field-strength delay spectrum describes ray contributions with deterministic amplitudes but statistical phases are used to derive time-and frequency-domain channel characteristics. Comparisons between measured and predicted data are presented.>

The gain of different diversity techniques that reduce the effects of amplitude and phase fluctuations in radio transmission systems depends on the correlation between the signals in various diversity channels. This paper presents a new approach for the prediction of the envelope correlation coefficient which is the term of interest for combining techniques with phase synchronization. It is based on the results of a deterministic 3D wave propagation model and on the assumption of ergodicity.>