Moritz Schack

Measurements and Analysis of an In-Car UWB Channel

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.

Coupling of simulators for the investigation of car-to-x communication aspects

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.

Analysis of Channel Parameters for Different Antenna Configurations in Vehicular Environments

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.

Performance Evaluation of Wiener Filter Designs for Channel Estimation in Vehicular Environments

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.

3D ray-tracing embedded into an integrated simulator for car-to-X communications

This contribution presents a 3D ray-tracing approach which is used as one major component in an integrated simulator for car-to-X communications consisting of a road traffic, a network and a radio propagation simulator. Since the computing time for performing ray-tracing is a critical parameter for the overall performance of the integrated simulator acceleration techniques have to be applied. Results from a study to increase runtime efficiency of the ray-tracer by software and hardware acceleration techniques are presented and possible applications of the simulator are discussed.

Minimizing the Electromagnetic Exposure Using Hybrid (DVB-H/UMTS) Networks

A hybrid mobile communication network as considered in this paper consists of a point-to-point network (UMTS) and a point-to-multipoint network (DVB-H). The benefit of combining these two networks is an optimized transfer of data by collecting several user requests for a single response via the broadcast network. Thus, capacity can be saved, UMTS cells can be unloaded and the mean response time of the system can be reduced. Besides these advantages, hybrid networks can be applied to decrease electromagnetic exposure, especially at hot spot areas. In this paper, it is analysed how the hybrid network structure influences the electromagnetic exposure. Therefore, different scenarios have been developed consisting of different user behavior and different network structures. In order to evaluate the grade of exposure, criteria have been defined. These criteria have been used for comparing a hybrid network with a single UMTS network in terms of electromagnetic exposure. The results are shown for the different network structures and network configurations

Linear Diversity Combining Techniques Employed in Car-to-X Communication Systems

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.

Vehicle-to-Vehicle Communications

This chapter discusses major results and conclusions from Special Interest Group C bringing together various aspects of mobile to mobile communication from all working groups. Vehicle-to-vehicle co ...

Impact of the Hybrid (DVB-H/UMTS) Network Structure on the Electromagnetic Exposure

A hybrid mobile communication network as considered in this paper consists of a point-to-point network (UMTS) and a point-to-multipoint network (DVB-H). The benefit of combining these two networks is an optimised transfer of data by collecting several user requests for a single response via the broadcast network. Thus, capacity can be saved, UMTS cells can be unloaded and the mean response time of the system can be reduced. Besides these advantages, hybrid networks can be applied to decrease electromagnetic exposure, especially at hot spot areas. In this paper, it is analysed how the hybrid network structure influences the electromagnetic exposure. Therefore, different scenarios have been developed consisting of different user behaviour and different network structures. In order to evaluate the grade of exposure, criteria have been defined. These criteria have been used for comparing a hybrid network with a single UMTS network in terms of electromagnetic exposure. The results are shown for the different network structures and network configurations.