Conference Paper

Performance Analysis of Pilot Patterns for Channel Estimation for OFDM Systems in High-Speed Trains Scenarios

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This paper investigates the performance of fast doubly selective fading channel estimation combining with inter-carrier interference (ICI) cancellation for Long Term Evolution (LTE) Communication Platform in high speed railway environment (LTE-R). We consider the channel impulse responds (CIR) coefficients with a critically Doppler frequency shift and multi-path fading that has been taken from Winner II channel model and the D2a propagation scenario, where the conditions of high-speed railway (HSR) are analyzed. As multi-path fading increases and the channel varies in the order of the symbol period, we first propose a novel approach for pilot symbols structure in time domain. After that, we deployed the proposed pilot symbol structure to estimate the channel in the time domain. Channel information corresponding to the data positions is obtained by the linear interpolation. In each OFDM symbol, the slope and the initial value for establishing an interpolation function are estimated to adapt to the time variation of the channel. An accurate estimate of channel state information will be used for the purpose of ICI cancellation. The simulation results show that the estimated channel by our proposed method can follow the real channel well, even in a very high Doppler frequency. The estimation performance in terms of mean squared error (MSE) significantly outperforms the state of the arts. Combination of our channel estimator with several interference cancelers provides a much better system performance compared to the case if the frequency channel estimation is used.
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Long Term Evolution for Railway (LTE-R) is commonly believed to be the next generation wireless communication system for high speed railway. The main objective of this paper is to assess the performance of LTE-R under realistic conditions using a hybrid high speed railway channel model involving WINNER II Channel Model that was refined and validated using measurements made within the WP1 Channel Model work package in Europe, high speed train channel model in 3GPP and large-scaled models based on a group of measurements on Zhengzhou-Xian passenger dedicated line in China. The paper presents a detailed evaluation of the BER and PSD for LTE-R suitably dimensioned for the high speed railway channel. The investigation includes analysis of the Doppler shift caused by the velocity of transmitter and receiver, the multipath interference due to reflections and diffractions from terrains in the radio service coverage area, and other serious impairing factors. The results show that LTE-R has promising potential to be used in a high speed railway environment.
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We present a complete simulation and experimentation framework for IEEE 802.11p. The core of the framework is an SDR-based OFDM transceiver that we validated extensively by means of simulations, interoperability tests, and, ultimately, by conducting a field test. Being SDR-based, the transceiver offers important benefits: It provides access to all data down to and including the physical layer, allowing for a better understanding of the system. Based on open and programmable hardware and software, the transceiver is completely transparent and all implementation details can be studied and, if needed, modified. Finally, it enables a seamless switch between simulations and experiments and, thus, helps to bridge the gap between theory and practice. Comparing the transceiver's performance with independent results from simulations and experiments, we underline its potential to be used as a tool for further studies of IEEE 802.11p networks both in field operational tests as well as simulation based development of novel physical layer solutions. To make the framework accessible to fellow researchers and to allow reproduction of the results, we released it under an Open Source license.
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With the rapid development of high-speed railway, the train speed can reach up to 350 km/h. Much more technical demands for high-speed railway mobile communication system are put forward. As the next generation wireless communication technology of 3GPP, Long Term Evolution for railway, known as LTE-R, is proposed to provide railway communication services including railway control, passenger services, wireless surveillance video, etc. The main goal of this paper is to evaluate the detailed performance of LTE-R on the WINNER D2a channel model which has been presented as an appropriate choice for the wireless channel model in high-speed scenario, and implement a LTE-R transceiver based on LabVIEW software and National Instruments Universal Software Radio Peripheral 2920 (NI USRP2920) platform for further research. The experimental results show that LTE-R has promising potential to be used in high-speed railway scenario.
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Includes: 1) Report from the IEEE Intelligent Vehicles Symposium 2009 and 2) The Organization of the IEEE Intelligent Transportation System Society.
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The channel estimation methods for OFDM systems based on a comb-type pilot sub-carrier arrangement are investigated. The channel estimation algorithm based on comb-type pilots is divided into pilot signal estimation and channel interpolation. The pilot signal estimation based on LS or MMSE criteria, together with channel interpolation based on piecewise-linear interpolation or piecewise second-order polynomial interpolation is studied. Owing to the MMSE estimate of the pilot signals, the inter-carrier interference and additive white Gaussian noise are reduced considerably. The computational complexity of pilot signal estimation based on MMSE criterion can be reduced by using a simplified LMMSE estimator with low-rank approximation using singular value decomposition. Phase compensators before and after interpolation are also presented to combat the phase changes of subchannel symbols arising from the frame synchronization errors. Compared to the transform-domain processing based channel estimation algorithm the MMSE estimate of pilot signals together with phase compensated linear interpolation algorithm provides a better performance and requires less computations
Experimental characterization of LTE wireless links in high-speed trains
  • T Domnguez
  • J Rodrguez
  • J Garca
  • L Castedo
IEEE Intelligent Transportation Systems Magazine
  • C Standard
  • Wang
A Survey on Channel Estimation Techniques Based on Pilot Arrangement in OFDM Systems
  • S Coleri
  • M Ergen
  • A Puri
  • A Bahai
  • E Engineering
  • U C Berkeley