For future railway wireless communication networks, it is an effective way to adopt higher frequency spectra with broader bandwidth to enhance the transmission capacity. Nevertheless, massive beamforming techniques are needed to overcome the severe path loss of higher frequency spectra. For railway systems with dual on-vehicle receivers, dual-beam transmissions can be implemented to improve the capacity. The analysis results show that the optimization of dual-beam transmissions depends on the train position. Based on the above, an adaptive beam splitting or integrating communication scheme is proposed. When the train is far away from the base station, to avoid the inter-beam interference, an integrated beam with wider beamwidth is used to cover the two receivers to realize diversity receiving. As the train is approaching the center of the base station, two beams are generated to realize space multiplexing, to improve the transmission capacity and reliability. Numerical simulation results demonstrate that the proposed scheme can adapt to train positions and improve the transmission performance.
FANG X M, CUI Y P, YAN L, et al. The evolution and development of key technologies of mobile communication systems for high-speed railway[J]. Journal of Electronics & Information Technology, 2015, 37(1): 226-235. doi: 10.11999/ JEIT141156.
ZHANG W, LI B, LIU Y, et al. Hybrid beamforming technology in 60 GHz millimeter wave uplink communication system[J]. Journal of Electronics & Information Technology, 2012, 34(11): 2728-2733. doi: 10.3724/SP.J.1146.2012. 00603.
[3]
RAPPAPORT T S, GUTIERREZ F, Ben-Dor E, et al. Broadband millimeter-wave propagation measurements and models using adaptive beam antennas for outdoor urban cellular communications[J]. IEEE Transactions on Antennas and Propagation, 2013, 61(4): 1850-1859.
[4]
KIM J and KIM I G. Distributed antenna system-based millimeter-wave mobile broadband communication system for high speed trains[C]. 2013 International Conference on ICT Convergence (ICTC), Jeju, Korea, 2013: 218-222.
[5]
SEUNG N C, DUKHYUN Y, Ilgyu K, et al. Uplink design of millimeter-wave mobile communication systems for high- speed trains[C]. IEEE 79th Vehicular Technology Conference (VTC Spring), Seoul, Korea, 2014: 1-5.
[6]
HUR S, KIM T, LOVE D J, et al. Millimeter wave beamforming for wireless backhaul and access in small cell networks[J]. IEEE Transactions on Communications, 2013, 61(10): 4391-4403.
[7]
KHAN F, PI Z, and RAJAGOPAL S. Millimeter-wave mobile broadband with large scale spatial processing for 5G mobile communication[C]. Annual Allerton Conference on Communication, Control, and Computing (Allerton), Monticello, IL, USA, 2012: 1517-1523.
ZOU W X, DU G L, LI B, et al. A novel beam search algorithm for 60 GHz millimeter wave communication[J]. Journal of Electronics & Information Technology, 2012, 34(3): 683-688. doi: 10.3724/SP.J.1146.2011.00436.
[9]
GODARA L C. Applications of antenna arrays to mobile communications, Part I: Performance improvement, feasibility, and system considerations[J]. Proceedings of the IEEE, 1997, 85(7): 1031-1060.
[10]
GODARA L C. Application of antenna arrays to mobile communications, Part II: Beam-forming and direction-of- arrival considerations[J]. Proceedings of the IEEE, 1997, 85(8): 1195-1245.
[11]
LUO W T, FANG X M, CHENG M, et al. Efficient Multiple- Group Multiple-Antenna (MGMA) scheme for high-speed railway viaducts[J]. IEEE Transactions on Vehicular Technology, 2013, 62(6): 2558-2569.
[12]
CHENG M and FANG X M. Location information assisted opportunistic beamforming in LTE system for high speed railway[J]. EURASIP Journal on Wireless Communications and Networking, 2012, 2012(210): 1-7.
[13]
CHENG M, FANG X M, and LUO W T. Beamforming and positioning-assisted handover scheme for long-term evolution system in high-speed railway[J]. IET Communications, 2012, 6(15): 2335-2340.
[14]
R1-092552. Reporting of CQI/PMI/RI for LTE TDD dual-layer beamforming[S]. Nokia, Nokia Siemens Networks, 2009.
[15]
LUO W T, ZHANG R, and FANG X M. A CoMP soft handover scheme for LTE systems in high speed railway[J]. EURASIP Journal on Wireless Communications and Networking, 2012, 2012(196): 1-9.
[16]
YANG C, LU L, DI C, et al. An on-vehicle dual-antenna handover scheme for high-speed railway distributed antenna system[C]. IEEE 6th International Conference on Wireless Communications Networking and Mobile Computing (WiCOM), Chengdu, China, 2010: 1-5.
XIE C F and QIU W J. Antenna Theory and Design[M]. Xi’an: Northwest Telecommunication Engineering College Press, 1985: 93-102.
[18]
DU Q, WU G, YU Q, et al. ICI mitigation by Doppler frequency shift estimation and pre-compensation in LTE-R systems[C]. International Conference on Communications in China (ICCC), Beijing, China, 2012: 469-474.
[19]
GU J, ZHANG H, and YANG J. On reduction of inter-beam interference in beamforming of multiple beam array antennas [C]. 7th International Conference on Signal Processing (ICSP), Beijing, China, 2004: 463-466.
[20]
PROAKIS J and SALEHI M. Digital Communications[M]. New York: McGraw Hill, 2000: 122-127.