Hsiang-Fu Yu

Broadcasting scheme with low client buffers and bandwidths for video-on-demand applications

Efficient data broadcasting is independent of request arrivals, and is thus highly promising when transmitting popular videos. A conventionally adopted broadcasting method is periodic broadcasting, which divides a popular video into segments, which are then simultaneously broadcast on different data channels. Once clients want to watch the video, they download the segments from these channels. The skyscraper broadcasting (SkB) scheme supports clients with small bandwidths. An SkB client requires only two-channel bandwidths to receive video segments. This work proposes a reverse SkB (RSkB) scheme, which extends SkB by reducing buffering spaces. The RSkB is mathematically shown to achieve on-time video delivery and two-channel client bandwidths. A formula for determining the maximum number of segments buffered by an RSkB client is presented. Finally, an analysis of RSkB reveals that its client buffer requirements are usually 25–37% lower than SkB. Extensive simulations of RSkB further demonstrate that RSkB yields lower client buffer demand than other proposed systems.

High-capacity reversible data hiding based on multi-histogram modification

Reversible data hiding is a technique that embeds a message into a host image with acceptable visual distortion and then recovers the image without any data loss while extracting the embedded message. The previous schemes mainly suffer from an unresolved problem that the imperceptibility of a marked image decreases severely as the embedding capacity increases. Extending the histogram modification technique, this study proposes a novel scheme that utilizes multiple histograms to increase embedding capacity while keeping marked-image quality. Unlike most histogram modification schemes, the multi-histogram scheme does not suffer from overflow and underflow during histogram shift. This scheme can yield the embedding capacity of 1 bit per pixel (bpp) at the PSNR of 48.13 db for a 512 × 512 grayscale image. To reduce the overhead during message embedding, the work further proposes an iterative multi-histogram scheme. Comprehensive experimental results show that both the schemes can achieve high embedding capacity and image quality.

Improvement of the client-centric approach for broadcasting popular videos

Periodic broadcast is a cost-effective solution for large-scale distribution of popular videos. Regardless of the number of video requests, this strategy guarantees constant worst service latency to all clients. An essential periodic broadcast method is the client-centric approach (CCA), which allows clients to use smaller receiving bandwidth to download broadcast data. An enhanced version, namely CCA+, was proposed to yield a shorter waiting time. This work further improves CCA+ by leveraging client bandwidth for more efficient video broadcast. The new scheme reduces the broadcast latency by as much as 39 % when compared to CCA+ and 78 % when compared to CCA. We prove the applicability of this new scheme and provide an analytical evaluation to demonstrate the performance advantage, as compared with particular schemes.

Efficient periodic broadcasting scheme for video delivery over a single channel

Periodic broadcasting is one of the cost-effective solutions for distributing popular videos to clients under constant worst playback latency. The broadcasting methods typically transmit video segments across multiple channels simultaneously, thus, requiring a client to receive segments from these channels concurrently. However, numerous practical systems, such as digital video broadcasting-handheld (DVB-H), do not allow clients to download video data from multiple channels because clients usually only have one tuner. To resolve this problem in multiple-channel broadcasting, the alternative broadcasting (AB) scheme, the hopping insertion (HI) scheme, SingBroad, PAS, the reverse-order scheduling (ROS) scheme, and the half-division broadcasting (HDB) scheme have been proposed to broadcast segments over a single channel. This paper presents a novel single-channel broadcasting scheme, which partitions a video into segments as many as possible to reduce video playback latency. Using mathematical analysis, this study verifies the workability of this scheme by demonstrating that client playback continuity is guaranteed. A performance analysis indicates that the proposed scheme yields the smallest waiting time, when compared with AB, HI, SingBroad, PAS, ROS, and HDB under various parameter settings. In addition, comprehensive simulation results show that the proposed scheme and ROS outperform these schemes (The comparison does not include the HI scheme because its buffer requirements are not provided in [24]) regarding smaller client buffer requirements under larger broadcasting bandwidth settings.

Multiagent Cooperative Learning Strategies for Pursuit-Evasion Games

This study examines the pursuit-evasion problem for coordinating multiple robotic pursuers to locate and track a nonadversarial mobile evader in a dynamic environment. Two kinds of pursuit strategies are proposed, one for agents that cooperate with each other and the other for agents that operate independently. This work further employs the probabilistic theory to analyze the uncertain state information about the pursuers and the evaders and uses case-based reasoning to equip agents with memories and learning abilities. According to the concepts of assimilation and accommodation, both positive-angle and bevel-angle strategies are developed to assist agents in adapting to their environment effectively. The case study analysis uses the Recursive Porous Agent Simulation Toolkit (REPAST) to implement a multiagent system and demonstrates superior performance of the proposed approaches to the pursuit-evasion game.

Single-Channel Data Broadcasting under Small Waiting Latency

Due to the advancement of network technology, video-on-demand (VoD) services are growing in popularity. However, individual stream allocation for client requests easily causes a VoD system overload; when its network and disk bandwidth cannot match client growth. This study thus presents a fundamentally different approach by focusing solely on a class of applications identified as latency tolerant applications. Because video broadcasting does not provide interactive (i.e., VCR) functions, a client is able to tolerate playback latency from a video server. One efficient broadcasting method is periodic broadcasting, which divides a video into smaller segments and broadcasts these segments periodically on multiple channels. However, numerous practical systems, such as digital video broadcasting-handheld (DVB-H), do not allow clients to download video data from multiple channels because clients usually only have one tuner. To resolve this problem in multiple-channel broadcasting, this study proposes a novel single-channel broadcasting scheme, which leverages segment-broadcasting capability further for more efficient video delivery. The comparison results show that, with the same settings of broadcasting bandwidth, the proposed scheme outperforms the alternative broadcasting scheme, the hopping insertion scheme, SingBroad, PAS, and the reverse-order scheduling scheme for the maximal waiting time.

A Limited-Client-Capability Broadcasting Scheme for VoD Applications

Data broadcasting is independent of client arrival rate, and thus it is very suitable to transmit popular videos that interest many clients at a particular period of time. One broadcasting method (called periodic broadcasting) is to partition a video into segments, which are then simultaneously broadcast on several data channels. Once clients want to watch the video, they download the segments from these channels. Specially, the skyscraper broadcasting (SkB), client-centric approach (CCA), greedy disk-conserving broadcasting (GDB) schemes were proposed to support a client with a small bandwidth. This paper presents a limited-client-capability broadcasting (LCCB) scheme, which achieves small waiting time, bandwidth consumption, and buffer demand on the client side. In comparison with SkB, CCA, and GDB, LCCB gains smaller waiting time. Extensive simulation results indicate that LCCB also requires lower client buffer spaces than SkB, CCA, and GDB.

A new slotted generalized Fibonacci broadcasting scheme for popular video delivery

It has been well recognized as an efficient approach for broadcasting popular videos by partitioning a video data stream into multiple segments and launching each segment through an individual channel simultaneously and periodically. Based on the design premises, the slotted generalized Fibonacci broadcasting (SGFB) scheme allows a client with small bandwidths to receive video segments. Given a fixed number of bandwidth channels on the client, SGFB can achieve the minimum client waiting time than other schemes. Extending SGFB, this work designs a new SGFB scheme (called SGFB+) to achieve small buffering space as well as low bandwidth demand at the client. Extensive simulation was conducted, which demonstrated that SGFB+ could have 37% smaller client buffer size than SGFB. Further simulation results also indicate that SGFB+ achieves lower client buffer demand than several broadcasting schemes.

An Efficient Broadcasting Scheme with Low Buffer Demand for Video-on-Demand Applications

It has been well recognized as an efficient approach for broadcasting popular videos by partitioning a video data stream into multiple segments and launching each segment through an individual channel simultaneously and periodically. Based on the design premises, the fibonacci broadcasting (FiB) scheme allows a client with two-channel bandwidths to receive video segments. Extending FiB, this work designs a new FiB scheme (called FiB+) to achieve small buffering space as well as low bandwidth demand at the client. Extensive simulation was conducted, which demonstrated that FiB+ could have 30% smaller client buffer size than FiB.

Efficient Periodic Broadcasting for Mobile Networks at Small Client Receiving Bandwidth and Buffering Space

Periodic broadcasting is an effective approach for delivering popular videos. In general, this approach does not provide interactive (i.e., VCR) functions, and thus a client can tolerate playback latency from a video server. The concept behind the approach is partitioning a video into multiple segments, which are then broadcast across individual communication channels in terms of IP multicast. The method improves system throughput by allowing numerous clients to share the channels. For many broadcasting schemes, client receiving bandwidth must equal server broadcasting bandwidth. This limitation causes these schemes to be infeasible in mobile networks because increasing receiving bandwidth at all client sites is expensive, as well as difficult. To alleviate this problem, the fibonacci broadcasting (FiB) scheme allows a client with only two-channel bandwidth to receive video segments. In comparison with other similar schemes, FiB yields smallest waiting time. Extending FiB, this work proposes a new scheme (called FiB