Hsin-Ta Chiao

WiFi multicast streaming using AL-FEC inside the trains of high-speed rails

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.

Video Everywhere Through a Scalable IP-Streaming Service Framework

In this paper, we propose a scalable IP-streaming service framework providing the time-shifting and place-shifting capability to achieve the vision of video everywhere. Traditional PVR (personal video recorder) provides the time-shifting viewing experience. However, when mobile TV and PMP (portable media player) are available, the traditional PVR has to be enhanced with the extra place-shifting viewing experience. Hence, several proprietary IPTV streaming techniques such as orb or SONY location free already can deliver a video stream to various kinds of end user terminals through Internet or wireless LAN. In this paper, we propose a distributed, scalable IP-streaming service framework to enhance the current IPTV streaming techniques. Three important issues are addressed in this paper. First, we propose a suitable metadata format that is capable of being used in the service framework second, we discuss how to produce scalable IDTV (interactive digital television) contents that can adapt the display capabilities of diverse terminal devices. Third, we evaluate how to apply the MPGE-4 SVC (scalable video coding) in the service framework.

Application-Layer FEC for file delivery over the WiMAX unicast networks

FLUTE is a file delivery protocol whose operation can only require a unidirectional communication channel from a sender to a receiver. Due to the nature of unidirectional delivery, FLUTE is designed in a flexible way so that it can cooperate with different kinds of forward error correction codes in application layer, such as systematic Raptor codes or other FEC codes defined in IETF. Besides, since FLUTE is a generic IP-based file delivery protocol, it is already applied for multicast-based file distribution in IP-based mobile TV standards such as DVB-IPDC and OMA BCAST. In addition, the FLUTE protocol can also be applied for long haul, multi-hop file delivery in an IP-based intranet. In this paper, we describe the experience of using the FLUTE protocol for file delivery over a WiMAX unicast network and show the performance gain of employing a systematic Raptor code as the application layer FEC for FLUTE.

FJM: a high performance Java message library

In this paper, we presented an IP-multicast-based Java message service implementation called FJM (fast Java messaging) library. We discussed its architecture, protocols, and implementation issues. For achieving better performance, we revised the original design of the FJM. The details of the refinement were also described in this paper. Then, we compared the performance of both versions of the FJM with the performance of other JMS implementations. After our careful design and tuning, in most cases, the revised version of the FJM can offer the highest throughput among the well known industrial or open source JMS implementations. Therefore, FJM can be used in many innovative or mission critical cluster applications, such as massively multiplayer virtual worlds or military simulator.

Efficient encoding of systematic Raptor codes based on operation lists for known block lengths

Raptor codes can provide good error correction capability and efficient encoding and decoding rates. Its fountain code property is effective in avoiding packet retransmission for both unicast and multicast service delivery. Hence, there are many wireless and broadband applications adopting it such as mobile multimedia broadcasting and broadband IPTV systems. In this paper, we present an efficient systematic Raptor codes encoder based on operation lists for known block lengths. For a Raptor codes application that can frequently use one or several fixed block lengths (i.e., the number of source symbols in a source block), we could produce the corresponding operation lists in advance and use it to generate the encoding symbols more efficiently. We first introduce the basic architecture of the proposed Raptor encoder, and then describes the details about how to generate operation lists and Raptor intermediate symbols. The simulation results show that our encoder is at least two times faster than the conventional Raptor codes encoder which is adopted by 3GPP and DVB-H.

UDP-based file delivery mechanism for video streaming to high-speed trains

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).

A mobile live TV system for Taiwan high-speed rail

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.

Decomposable Forward Error Correction Codes Based on Chinese Remainder Theorem

Several applications benefited from multicast data distribution because a sender can concurrently transmit data to multiple receivers using fewer bandwidth. However, reliability is an important issue in multicast because retransmission is not very efficient in multicast. In recent years, Forward Error Correction (FEC) codes are proposed to facilitate reliable multicast data distribution and are applied to several applications. FEC provides a more efficient way of reliable multicast data distribution because of no retransmission. In this paper, we propose a new FEC codes (F-CR codes), which are extended from Chinese Remainder codes, require smaller transmission redundancy than conventional FEC codes and support two variants for transmission and computation efficiency. In particular, the r-decomposition variant allows the sender to decompose an output symbols encoded into r smaller sub-symbols. This decomposable property which is firstly proposed in this paper is especially suitable for link unstable networks or link heterogeneity networks like wireless sensor networks. The analysis and experiments also demonstrate the feasibility of F-CR codes.

An HD streaming system for WiFi multicast channels based on application-layer FEC

This paper presents an HD (High Definition) streaming system that employs an AL-FEC (Application-Layer FEC) scheme (i.e., DVB AL-FEC) based on Raptor codes to protect the transmission of MPEG-2 TS (Transport Streaming) over RTP streaming packets over error-prone Wi-Fi multicast channels. The employed AL-FEC scheme can effectively recover the missing Wi-Fi multicast packets in a scalable way. In this paper, we describe the prototype of the proposed HD streaming system, which is implemented based on VLC server and VLC client over Linux operating systems. Finally, we show that the proposed system can significantly improve the HD video quality of a Wi-Fi multicast streaming service.

Mobile TV streaming over the mobile WiMAX network for high-speed rail reception

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.