Seamless LTE connectivity in high speed trains

High speed train (HST) is becoming one of the preferred mid-range transportation and the on-board Internet service is a must for train operators. LTE networks paved the road toward high quality and cost effective on-board Internet in HSTs. However, frequent handovers (HO) for several onboard users overload sequentially cells along the train-track and increases the service interruptions, that in turn degrade untolerably the quality of service (QoS). HO service interruptions could be largely mitigated if HST could be virtually longer to access multiple cells from multiple devices coordinated in bundle. This is the paradigm of multi-cell access investigated here. More specifically, we propose a novel (and practically viable) onboard architecture for train-to-ground LTE backhauling. Multiple directional antennas with fixed-beams are deployed along the train to provide multi-cell access to distribute on-board traffics over at least three cells. Multiple antennas are paired with a load balancing mechanism for seamless on-board Internet. The combined use of multi-cell access and distributed load balancing mechanism provide a balanced QoS across all carriages that heavily mitigates the service discontinuities due to LTE HOs. The proposed architecture does not imply any change on network side. Conclusions are supported by numerical results for realistic LTE parameters in current HST settings. © 2014 IEEE