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Through the wide deployment of high-speed rails around the world, multimedia services on high-speed trains will be highly demanded in the near future. However, network round trip time and packet loss rate for high-speed rail reception are much higher and also of high variance. To facilitate the delivery of a live video streaming service, our previous research suggests that the video streaming service is transmitted as a file delivery service and the generated streaming files are delivered via a UDP-based file delivery protocol. In this paper, we investigate the potentials of UDP-based file delivery protocols for high-speed rail reception. We propose Reliable FLUTE (R-FLUTE) for reliable UDP-based unicast file delivery by introducing feedback mechanisms into the IETF FLUTE protocol. To get higher throughput and better network utilization, we extend R-FLUTE to support multisession delivery and propose an adaptive session-based rate control mechanism. We further conduct our experiments on a real 802.16e mobile WiMAX network for Taiwan High Speed Rail (THSR). The results show that the proposed scheme in comparison with FTP can provide more stable throughput, thereby requiring smaller buffer level in receivers (i.e., can deliver more real-time live video to receivers).

In Taiwan, because of the Doppler effects and tunnel shading, it is difficult to smoothly receive a live DVB-T channel inside a high-speed train by a laptop equipped with an ordinary DVB-T USB dongle. For providing live TV services inside a high-speed train, we develop a mobile live TV system for Taiwan High-speed Rail (THSR). The proposed system delivers live TV programs to a high-speed train through the mobile WiMAX network deployed along the THSR railway by the WiMAX operator VeeTime. Then, the received live TV programs are delivered to the terminal devices of high-speed rail passengers through Wi-Fi multicast. Using Wi-Fi multicast inside a high-speed train is necessary since there may be several hundreds of concurrent users on the same high-speed train. However, conventionally to provide a scalable Wi-Fi multicast streaming system is difficult because no extra reliability control mechanisms such as ARQ (Automatic Repeat-reQuest) are available for Wi-Fi multicast. Instead we overcome the difficulty of scalable Wi-Fi multicast streaming by using AL-FEC (Application Layer -- Forward Error Correction). Hence, in the demo session of MobiSys 2013, we plan to show the whole mobile live TV system with a live TV input, especially focused on its capability of scalable Wi-Fi multicast streaming over a multi-hop Wi-Fi network that can emulate the real multi-hop Wi-Fi network inside a high-speed train.

A low-cost radio-over-fiber (RoF) based integrated transmission of long term evolution (LTE) and worldwide interoperability for microwave access (WiMAX) signals is proposed to solve the shadowing effect of building envelopes and the complexity of transmitting system in wireless access network services. This scheme is also applied to solve the problems of required fast handover and poor signal penetration in tunnels for high-speed rail mobile connections. We design and demonstrate experimentally a multi-service WiMAX/LTE RoF system that can extend the indoor signal coverage, with an emphasis on the power conversion efficiency and optoelectronic component selections. The designed RoF transceivers and switches are being deployed in both the campus buildings and the tunnels of Taiwan High-Speed Rail system to allow mobile connections.

AL-FEC (Application-Layer FEC) is already in used for protecting streaming and file delivery services against packet losses in the field of wide-area multimedia broadcasting, such as in DVB-H and 3GPP MBMS (Multimedia Broadcast Multicast Service) mobile TV systems. However, it is still not a well-studied approach for applying AL-FEC to WiFi multicast since guaranteed bandwidth for a multicast service is more difficult to be allocated in a WiFi network in comparison to traditional mobile TV systems. In this paper, we show our experiences of using an AL-FEC code; i.e. the systematic Raptor code as well the IETF FEC Framework to further protect the RTP packets delivered over WiFi multicast carriers inside the cars of a train for high-speed rails, instead of using any feedback and retransmission mechanisms.

For improving the service quality of the Taiwan High-Speed Rail (THSR), a dedicated mobile WiMAX network (based on IEEE 802.16e in the current stage) is planned to be deployed along the railway of THSR. The mobile WiMAX network is not only for providing Internet access over the THSR trains, but also for delivering live entertainment contents to the passengers, such as mobile TV streaming of live programs. In this paper, we show the experiences about the design, implementation and evaluation of the mobile TV streaming service for high-speed rail reception based on AL-FEC (Application-Layer FEC). The experiment results show that AL-FEC can effectively compensate the packet losses in the high-speed reception scenario if the underlying reliability control schemes in IEEE 802.16e cannot provide error free mobile TV streaming delivery.

As high speed rails become more and more popular, providing broadband internet access on high speed rails is not widespread due to the large inter-carrier interference, terrestrial obstacles and inherent carriage shielding. In this paper an integrated Worldwide Interoperability for Microwave Access-Radio over Fiber (WiMAX-RoF) system is proposed and deployed along Taiwan High Speed Rail (THSR) rail tracks. Field trial and laboratory experiment results are presented. According to the field trial results, excessive delay induced by unequal fiber length deteriorates the throughput performance and can be overcome by equalizing the fiber length. On the other hand, rate adaptation for maximum throughput is challenging at high mobility. Careful calibration is needed to tradeoff the throughput gain against robustness to signal fluctuations. Laboratory experiments distinguish the impact of echo channel and remote antenna unit (RAU) distance from others. The results give insights in the analysis of field trial results.

For the sake of satisfying the requirement of different receivers and adapting the network condition, a new video coding scheme appears and is called Scalable Video Coding (SVC). Different from traditional coding scheme i.e. H.264, encoding once by using SVC encoder can generate one bitstream with different resolutions as well as frame rate, and the bitstream can be corresponded with the requirement of different receivers. In this paper, we propose two adaptive SVC layer switching algorithms for dedicated Worldwide Interoperability for Microwave Access (WiMAX) network of Taiwan High Speed Rail (THSR). The adaptive layer switching algorithms are based on network condition to adjust to delivering video data. For the first algorithm, we record the Received Signal Strength Indicator (RSSI) trace at the high speed moving environment of THSR in advance, and measure the available network bandwidth with RSSI trace. Then, Streaming Server can deliver the corresponding SVC layer data by measured network bandwidth. As to the second algorithm, Streaming Server estimates network available bandwidth from static information such as packet loss rate sent by Streaming Client. Streaming Server can select and deliver SVC layer data which are adapted to estimated network bandwidth. Our streaming system is an adaptive streaming system because video layer switching adapts to different network conditions.

A link adaptation scheme for MIMO-OFDM systems over high speed rail environment is addressed in this paper. In this study, a selection method of MIMO transmission mode and the modulation and coding scheme (MCS) according to the Rician channel K-factor from our previous work is considered. A hidden Markov model of time-varying Rician channel K-factor is constructed by using the real measured channel data on the high speed rail train. With the constructed hidden Markov model, the time correlation of Rician channel K-factor can be obtained and the time-varying K-factor value can be generated. By using the hidden Markov model, the K-factor value can be predicted to facilitate link adaptation since the K-factor may vary during feedback, especially in high mobility scenario. Simulation results show an average throughput improvement of 5Mbps.

To solve the cell-edge problem (deep and flat fading for long time) of multi-cell MBMS in SFN and reduce PAPR in OFDM systems simultaneously, a novel transmission architecture is proposed. Grid scrambling diversity scheme is adopted in the architecture to increase time and frequency diversity. Several grid scramblers are used and the time domain signal with smallest PAPR is selected for transmission. Some simulation results are provided to demonstrate the efficacy of the proposed architecture.

In this paper, we propose a novel transmission structure with the time-frequency scrambling scheme. The major concept of this technique is coming from combining the Toshiba's approach and our proposed time-dimension group scrambling scheme. In this technique, several OFDM symbols and several sub- carriers can be grouped into a grid structure and then scrambled by a scrambling pattern, the time- frequency dimension diversity gains are both increased after channel decoder. The time-frequency scrambling scheme uses the random behaviors of transmitted signals from multiple cells to create the plentiful time and frequency channel diversity, indeed, control the coherent time and the interleaver length. Hence, the burst error due to the flat fading and the long-term shadowing fading can be mitigated and channel coding will work more efficiently. The simulation results show that the destructive interference can be improved at the cell-edge by the proposed scheme. The SNR gains can be derived by the proposed scheme for mutli-cell MBMS environments (5 dB and 1.5 dB for two equal-gain and TU6 channels, respectively).