Location information-assisted opportunistic beamforming in LTE system for high-speed railway

Abstract

Communication systems of high-speed railway have inherent disadvantages and advantages. The estimation error of direction-of-arrival (DOA) of desired users caused by channel feedback delay and high moving speed make the common beamforming technique of smart antennas work abnormally. Instead, the opportunistic beamforming (OBF) with dumb antennas which does not need channel feedback is proper for high-speed railway. As the system has linear topology, regular movement as well as predictable location and speed information, the OBF can be improved to adapt to this scenario. In this article, conventional OBF is first introduced to the communication systems of high-speed railway. By multiplying random complex on each transmit antenna, the channel fluctuation dynamic range is extended so that multiuser diversity can be exploited. And then location information is employed to assist the conventional one. Communication systems in high-speed railway have the advantage of predictable location and speed information. The improved OBF can perform closer to the performance of coherent beamforming. Numerical analysis and simulation results show that both two algorithms can improve the system performance significantly.

Performance Improvement of LeastSquares Adaptive Filter for High-Speed Train Communication Systems

“…For high-speed train communications, the train speed and location information can be obtained for HST due to its repetitive movement characteristic [8][9]. In particular, this information can be obtained from the signalling controller center, as shown in Cheng, et al [8], and can be predicted by retrieving the information from a dedicated radio environment map, as presented in Li, et al [9].…”

“…In particular, this information can be obtained from the signalling controller center, as shown in Cheng, et al [8], and can be predicted by retrieving the information from a dedicated radio environment map, as presented in Li, et al [9]. The assumption of Doppler shift of the LOS component known perfectly at the receiver is therefore realistic.…”

“…The proposed technique assumes that the time-varying phase of the LOS component is known perfectly at the receiver. This assumption is based on the fact that for high-speed train communications, the speed and train locations can be predicted from communications between trains and the signalling controller center, as shown in Cheng and Fang [8], or by retrieving information from a dedicated environment map, as presented in Li and Zhao [9].…”

A massive MIMO-based adaptive multi-stream beamforming scheme for high-speed railway

“…A WiMAX-based route-tracking beamforming was proposed, and field tests over Taiwan HSR were carried out [26]; the experimental results showed that the received signal strength indicator (RSSI), carrier to interference plus noise ratio (CINR), and throughput were improved. In [5,[27][28][29][30], location information-assisted opportunistic beamforming, beamforming and locationassisted handover scheme, beamforming and Alamouti STBC combined scheme, location assistant beamforming, and distributed beamforming were proposed to improve system throughput and transmission reliability under HSR scenario by exploiting the regular and predictive location and velocity information of the train. However, in the above schemes, only single-stream beamforming and dual-stream beamforming were adopted but the performance of multi-stream beamforming is not analyzed and discussed in this scenario either.…”

“…Beamforming can also be applied in non-LOS, if the multipath channel state information (CSI) is known [25]. Several beamforming-based schemes were conceived for HSR communication systems [5,[26][27][28][29][30]. A WiMAX-based route-tracking beamforming was proposed, and field tests over Taiwan HSR were carried out [26]; the experimental results showed that the received signal strength indicator (RSSI), carrier to interference plus noise ratio (CINR), and throughput were improved.…”