A method is described comprising: transmitting a training signal from each antenna of a base station to each of a plurality of client devices, each of the client devices analyzing each training signal to generate channel characterization data, and transmitting the channel characterization data back to the base station; storing the channel characterization data for each of the plurality of client devices; receiving data to be transmitted to each of the client devices; and precoding the data using the channel characterization data associated with each respective client device to generate precoded data signals for each antenna of the base station; and transmitting the precoded data signals through each antenna of the base station to each respective client device.

System and method for distributed input-distributed output wireless communications

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.

Challenges Toward Wireless Communications for High-Speed Railway

一种高速调制解调器，它通过电话线发送和接收一载频集的数字数据。 该调制解调器包括在载波之间可变地分配数据和功率，以便补偿等效噪声和使数据速率最大的系统。 此外，也介绍不需要一个均衡网络、可自适应地分配信道的控制和可跟踪线上参数变化的系统。

Ensemble modem structure for imperfect transmission media

This paper presents a novel and practical study on the position-based radio propagation channel for High-Speed Railway by performing extensive measurements at 2.35 GHz in China. The specification on the path loss model is developed. In particular, small scale fading properties such as K-factor, Doppler frequency feature and time delay spread are parameterized, which show dynamic variances depending on the train location and the transceiver separation. Finally, the statistical position-based channel models are firstly established to characterize the High-Speed Railway channel, which significantly promotes the evaluation and verification of wireless communications in relative scenarios.

Position-Based Modeling for Wireless Channel on High-Speed Railway under a Viaduct at 2.35 GHz

A system and machine-implemented method are described for performing precoding interpolation in a DIDO system which employs orthogonal frequency-division multiplexing (OFDM) and DIDO precoding to communicate with a plurality of distributed-input-distributed-output (DIDO) clients. For example, a system according to one embodiment of the invention comprises: selecting a first subset of ODFM tones to determine a first subset of precoding weights; deriving a second subset of precoding weights for a second subset of ODFM tones by interpolating between the first subset of precoding weights; and using a combination of the first subset of precoding weights and the second subset of precoding weights to precode a data stream prior to transmitting the data stream to a DIDO client.

System and method for DIDO precoding interpolation in multicarrier systems

This paper presents a channel model for direct train- to-train communication appropriate for the 400 MHz band. Extrapolation of theoretical and experimental results obtained for the planning of other railway communication systems like GSM-R is not obvious due to the difference in frequencies, antenna height and absence of base stations. In this paper, the analysis of the channel model covers different radio phenomena including path loss, Doppler, fading, and delay spread. Concretely we consider three scenarios (train stations, shunting yards and regional networks), for which the propagation channel characteristics are discussed. Furthermore, influence of special railway environments like cuttings which can be found near cities and towns, tunnels and bridges are encountered.

/pdf/channel-model-for-train-to-train-communication-using-the-400-4jf3xnengu.pdf

Channel Model for Train to Train Communication Using the 400 MHz Band

Cooperative safety applications require dedicated short-range communications (DSRC) to provide position-awareness of neighboring vehicles at a specific level of reliability, i.e., awareness-quality, up to a given distance, i.e., awareness-range. However, heavy communication loads negatively impact such awareness requirements due to communication impairments, ranging from strict capacity limitations of DSRC channels to correlated packet collisions due to periodic communication patterns. Transmission control strategies may adapt power or rate to control such impairments but risk missing the requirements of cooperative safety applications. In this paper, we design a new awareness control strategy by implementing a spatial awareness framework. Specifically, we adapt the distribution of the awareness-quality as a function of the awareness-range. Therefore, we first propose random transmit power control (RTPC), which manages to provide different levels of awareness-quality at different ranges, while mitigating correlated packet collisions by randomizing them in space. As RTPC is able to reduce the channel load, we secondly propose to combine RTPC with transmit rate control (TRC) and to benefit from the gained channel resources by subsequently increasing the update-rate and by implication, the quality of position-awareness. The spatial awareness control capability of RTPC $+$ TRC has been evaluated through simulations. We discuss the influence of RTPC $+$ TRC on cooperative safety applications exemplarily for the forward collision warning (FCW) application.

Random Transmit Power Control for DSRC and its Application to Cooperative Safety

The paper presents an overview of the state of the art in collision avoidance related with transportation systems like the automatic identification system (AIS) for maritime transportation, traffic alert and collision avoidance system/automatic dependent surveillance-broadcast (TCAS/ADS-B) for aircraft, and the car-2-car communication system (C2C) for road transportation. The examined systems rely on position detection and direct communication among vehicles. Alike a collision avoidance system for railway transportation "RCAS" is introduced. Focussing on the communication aspects, possible applicability of the examined state of the art systems to RCAS is studied. The analysis are performed at different communication system layers, namely application (APP) layer, media access control (MAC) layer and physical layer (PHY), which are the most relevant for a single hop network broadcast system as favorized in RCAS. Since multihop and addressed communication are not foreseen in a first RCAS approach, the network layer is not taken into account.

/pdf/comparison-of-collision-avoidance-systems-and-applicability-441j9d4faq.pdf

Comparison of Collision Avoidance Systems and Applicability to Rail Transport

In this paper we present the results of an empirical study investigating the performance of TETRA (TErrestrial Trunked RAdio) in a Vehicular Ad-hoc Network (VANET) for safety related railway traffic applications. The Short Data Service (SDS) of TETRA in the Direct Mode Operation (DMO) allows an infrastructure-less exchange of traffic relevant information between vehicles in range of the communication. The propagation channel in case of such a direct (base station free) communication between railway vehicles underlies specific effects, which are not equivalent to other well known terrestrial mobile scenarios. We will present measurements covering urban, suburban and rural environments along a regional railway network in the south of Bavaria. Beside different operational conditions such as front, rear, and flank approaches of trains, we investigated several topological scenarios on both, single and double track sections along the line. We will also discuss the observed characteristic changes in narrow band signal attenuation and Doppler spectra for passages through forests, hilly areas, stations and a tunnel. We determined statistics for the transmission delay of messages and the message erasure rates for single and multi user access on a single common carrier for different transmission intervals. Finally, the quality of service for the envisaged safety applications is assessed.

On the Performance of TETRA DMO Short Data Service in Railway VANETs

The proceedings contain 20 papers. The topics discussed include: VANET architectures and protocol stacks: a survey; behavior specification of a red-light violation warning application - an approach for specifying reactive vehicle-2-X communication applications; wireless protocol design for a cooperative pedestrian protection system; a vehicular mobility model based on real traffic counting data; driver-centric VANET simulation; simulative evaluation of the potential of Car2X-communication in terms of efficiency; performance study of an in-car switched Ethernet network without prioritization; degradation of communication range in VANETs caused by interference 2.0 - real-world experiment; real-world measurements of non-line-of-sight reception quality for 5.9GHz IEEE 802.11p at intersections; and interoperability testing suite for C2X communication components. © Springer-Verlag Berlin Heidelberg 2011

/pdf/communication-technologies-for-vehicles-58203xbcx4.pdf

Cristina Rico Garcia

Papers

Channel Model for Train to Train Communication Using the 400 MHz Band

Random Transmit Power Control for DSRC and its Application to Cooperative Safety

Comparison of Collision Avoidance Systems and Applicability to Rail Transport

On the Performance of TETRA DMO Short Data Service in Railway VANETs

Communication Technologies for Vehicles