12 research outputs found
HighâSpeed Data Transmission Subsystem of the SEOSAR/PAZ Satellite
This paper analyzes a digital interface and bus system modeling and optimization of the SEOSAR/PAZ Earth Observation satellite. The important part of the satellite is an Xâband Synthetic Aperture Radar instrument that integrates 384 Transmit/Receive Modules located in 12 antenna panels 7.5 m away from the central processor and controlled by a synchronous 10 Mbps bidirectional serial protocol. This type of midârange pointâtoâmultipoint transmission is affected by bit errors due to crosstalk, transmission line attenuation and impedance mismatches. The highâspeed data communication network has been designed to optimize the transmission by using a simulation model of the data distribution system which takes into account the worstâcase scenario and by developing a labâscaled prototype which exhibits BER of 10-11 for an interfering signal of 10 Vpp. The result is a pointâtoâmultipoint bidirectional transmission network optimized in both directions with optimal values of loads and equalization resistors. This highâspeed data transmission subsystem provides a compact design through a simple solution
Modeling of the Division Point of Different Propagation Mechanisms in the Near-Region Within Arched Tunnels
An accurate characterization of the near-region propagation of radio waves inside tunnels is of practical importance for the design and planning of advanced communication systems. However, there has been no consensus yet on the propagation mechanism in this region. Some authors claim that the propagation mechanism follows the free space model, others intend to interpret it by the multi-mode waveguide model. This paper clarifies the situation in the near-region of arched tunnels by analytical modeling of the division point between the two propagation mechanisms. The procedure is based on the combination of the propagation theory and the three-dimensional solid geometry. Three groups of measurements are employed to verify the model in different tunnels at different frequencies. Furthermore, simplified models for the division point in five specific application situations are derived to facilitate the use of the model. The results in this paper could help to deepen the insight into the propagation mechanism within tunnel environments
Channel Capacities for Different Antenna Arrays with Various Transmitting Angles in Tunnels
[[abstract]]This paper focuses on the research of channel capacity of multiple-input multipleoutput
(MIMO) system with different transmitting angles in straight and curvy tunnels.Araytracing
technique is developed to calculate channel frequency responses for tunnels, and the
channel frequency response is further used to calculate corresponding channel capacity. The
channel capacities are calculated based on the realistic environment. The channel capacities
of MIMO long term evolution system using spatial and polar antenna arrays by different
transmitting angles are computed. Numerical results show that, The channel capacity for
transmitting angle at 15⊠is largest compared to the other angles in the tunnels. Moreover,
the channel capacity of polar array is better than that of spatial array both in the straight and
curvy tunnels. Besides, the channel capacity for the tunnels with traffic is larger than that
without traffic. Finally, it isworth noting that in these cases the presentwork provides not only
comparative information but also quantitative information on the performance reduction.[[notice]]èŁæŁćźçą[[incitationindex]]SC
Communication systems of highâspeed railway: A survey
Modern railway services are required to deliver good quality services to the passenger throughout the whole journey. These include improved performances, safety, and reduce delays. There is also the requirement for inâtrain customer experience such as infotainment and access to reliable communication systems. The railway industry has employed different types and generations of communication systems in recent times. Signaling systems were used at the early stage of the railway services. Today, communication systems such as the secondâgeneration communication system, also known as the global system for mobile communications (GSM), the Thirdâgeneration (3G) and the Fourthâgeneration (4G) are utilized in the railway industry. In this paper, we present a brief history of railway communication systems, their features and applications. In addition, we discuss the technical challenges and potential solutions of inâtrain communication systems and how data can be distributed onâboard and between the train coaches using state of the art and hybrid communication technologies