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For high-speed rail networks, data transmission suffers from severe penetration loss and when the train moves from one base station to another, a large number of User Equipments (UEs) on board carry out the handover authentication procedure simultaneously, which incurs a lot of handover overheads. The introduction of Mobile Relay Node (MRN) can improve the link quality and decrease the handover overheads. However, MRNs still suffer from several protocol attacks and frequent handovers and thus, the introduction of MRNs deteriorates the handover success rate and handover performance. At the same time, considering the diversity of future 5G high-speed rail networks, in this paper, we propose two fixed-trajectory group pre-handover authentication schemes for MRN: the first proposed scheme FTGPHA1 which establishes most of the important security properties and costs low handover overheads, and the second proposed scheme FTGPHA2 which furnishes better security properties than the first one. In these two schemes, since all of the MRNs in the same train and the next base station can accomplish the handover authentication with the help of the donor software defined networking controller before the MRN arrives, the handover delay can be ignored and thus, uninterrupted services can be provided for UEs on board. The security and performance evaluations demonstrate that the two proposed schemes outperform other related schemes. [ABSTRACT FROM AUTHOR]

In this paper, a novel two-hop relay architecture using mobile relay nodes (MRN) technology for high-speed trains is presented. In this architecture, a long-term evolution advanced (LTE-A) link in sub-6 GHz bands is established between the Donor-eNB (DeNB) and the MRNs mounted on the roof of the train and another in millimeter Wave (mmWave) bands between the MRN and the user equipment (UE) terminals inside the train. Moreover, the multiple-input multiple-output (MIMO) channel is exploited between the DeNB and the UEs to enhance channel capacity. Different relay structures—several relays in a train carriage and a single relay with multiple antennas—and different types of relays—amplify-and-forward and decode-and-forward (DF)—are studied. Ultimately, performance analysis is studied and discussed by means of a downlink-level simulator with accurate channel models. Furthermore, multiuser transmission and conventional user scheduling algorithms are added to obtain a more realistic simulator. A new algorithm for one of the structures and the DF relay is proposed. This paper will examine how to provide broadband data access to train passengers in high-speed environments by validating a new architecture, which takes advantage of MIMO techniques, mobile relays, and millimeter bands. [ABSTRACT FROM AUTHOR]

The orthogonal space-time block code (OSTBC) and cooperative relaying schemes are the two major spatial diversity techniques to achieve high link reliability in any wireless communication system. Typically, the OSTBC based cooperative amplify-and-forward relaying system achieves optimal diversity gain with simple linear decoding by assuming that the channels remain quasi-static during the length of the Alamouti code-word symbol periods. However, due to time selective fading or relay node’s mobility, the quasi-static assumptions does not hold good and causes severe error floor in the system. In this paper, at first, we have investigated various conventional signal detection methods to improve the system performance which include Alamouti and quasi-ML detection (QMLD) methods. Then, we derive the exact closed-form signal-to-interference-plus-noise ratio expression for the Alamouti method and signal-to-noise ratio for the QMLD method. Based on this performance analysis, we propose a decision feedback detection (DFD) which is a hybrid of Alamouti and QMLD methods. The simulation results show that the proposed DFD method significantly outperforms the conventional QMLD method under high mobility channel environment. [ABSTRACT FROM AUTHOR]

In recent years, train passengers have been transferring increasing amounts of data using mobile devices. Wireless networks with mobile relay nodes support broadband wireless communications for passengers of such vehicles using backhaul links. However, the mobility management entity reuses the handover of existing user equipment, resulting in the handover of the Long-Term Evolution network being unsuitable for user equipment within the cabins of vehicles traveling at high speed. In this paper, we propose a self-optimizing handover hysteresis scheme with dual mobile relay nodes for wireless networks in high-speed mobile environments. The proposed mechanism tunes the hysteresis and cell individual offset handover parameters based on the velocity of the vehicle and the handover performance indicator, which affects the handover triggering decision and performance. The results of simulations conducted in which the performance of the proposed scheme was compared to that of an existing scheme show that the proposed scheme can reduce the number of radio link failures and service interruptions during handover procedures. [ABSTRACT FROM AUTHOR]