International Journal of Digital Multimedia Broadcasting The latest articles from Hindawi © 2017 , Hindawi Limited . All rights reserved. A Novel Steganography Technique for SDTV-H.264/AVC Encoded Video Mon, 09 May 2016 12:58:09 +0000 Today, eavesdropping is becoming a common issue in the rapidly growing digital network and has foreseen the need for secret communication channels embedded in digital media. In this paper, a novel steganography technique designed for Standard Definition Digital Television (SDTV) H.264/AVC encoded video sequences is presented. The algorithm introduced here makes use of the compression properties of the Context Adaptive Variable Length Coding (CAVLC) entropy encoder to achieve a low complexity and real-time inserting method. The chosen scheme hides the private message directly in the H.264/AVC bit stream by modifying the AC frequency quantized residual luminance coefficients of intrapredicted I-frames. In order to avoid error propagation in adjacent blocks, an interlaced embedding strategy is applied. Likewise, the steganography technique proposed allows self-detection of the hidden message at the target destination. The code source was implemented by mixing MATLAB 2010 b and Java development environments. Finally, experimental results have been assessed through objective and subjective quality measures and reveal that less visible artifacts are produced with the technique proposed by reaching PSNR values above 40.0 dB and an embedding bit rate average per secret communication channel of 425 bits/sec. This exemplifies that steganography is affordable in digital television. Christian Di Laura, Diego Pajuelo, and Guillermo Kemper Copyright © 2016 Christian Di Laura et al. All rights reserved. Enhancing the Security of Customer Data in Cloud Environments Using a Novel Digital Fingerprinting Technique Wed, 04 May 2016 11:25:10 +0000 With the rapid rise of the Internet and electronics in people’s life, the data related to it has also undergone a mammoth increase in magnitude. The data which is stored in the cloud can be sensitive and at times needs a proper file storage system with a tough security algorithm. Whereas cloud is an open shareable elastic environment, it needs impenetrable and airtight security. This paper deals with furnishing a secure storage system for the above-mentioned purpose in the cloud. To become eligible to store data a user has to register with the cloud database. This prevents unauthorized access. The files stored in the cloud are encrypted with RSA algorithm and digital fingerprint for the same has been generated through MD5 message digest before storage. The RSA provides unreadability of data to anyone without the private key. MD5 makes it impossible for any changes on data to go unnoticed. After the application of RSA and MD5 before storage, the data becomes resistant to access or modifications by any third party and to intruders of cloud storage system. This application is tested in Amazon Elastic Compute Cloud Web Services. Nithya Chidambaram, Pethuru Raj, K. Thenmozhi, and Rengarajan Amirtharajan Copyright © 2016 Nithya Chidambaram et al. All rights reserved. Model Aspects of Open Access to Multimedia Broadcast Services in the Evolved Packet System Wed, 02 Mar 2016 12:56:46 +0000 Multimedia broadcast is the most efficient method to distribute identical content to multiple users in the Evolved Packet System (EPS). EPS enables efficient usage of network resources and provisioning of quality of service for every user. Third-party control allows applications in an enterprise domain to invoke network functions like multimedia broadcast. In this paper, an approach to modeling the behavior of Service Capability Server (SCS) for multimedia broadcast in EPS is presented. Third-party applications can access multimedia broadcasting capabilities by using Parlay X Web Service interfaces. The SCS for multimedia broadcast exposes Parlay X interfaces toward 3rd-party applications and control protocols toward the network. The SCS functional behavior has to be synchronized with the application view on message broadcast and the state of the network resources intended for the broadcast session. Models of multicast session, IP connectivity session, and bearers’ and charging session are proposed and formally described using the notation of Label Transition Systems. The concept of weak bisimilarity is used to prove that models expose equivalent behavior; that is, they are synchronized. Ivaylo Atanasov and Evelina Pencheva Copyright © 2016 Ivaylo Atanasov and Evelina Pencheva. All rights reserved. Adaptive Streaming of Scalable Videos over P2PTV Wed, 12 Aug 2015 07:10:46 +0000 In this paper, we propose a new Scalable Video Coding (SVC) quality-adaptive peer-to-peer television (P2PTV) system executed at the peers and at the network. The quality adaptation mechanisms are developed as follows: on one hand, the Layer Level Initialization (LLI) is used for adapting the video quality with the static resources at the peers in order to avoid long startup times. On the other hand, the Layer Level Adjustment (LLA) is invoked periodically to adjust the SVC layer to the fluctuation of the network conditions with the aim of predicting the possible stalls before their occurrence. Our results demonstrate that our mechanisms allow quickly adapting the video quality to various system changes while providing best Quality of Experience (QoE) that matches current resources of the peer devices and instantaneous throughput available at the network state. Youssef Lahbabi, El Hassan Ibn Elhaj, and Ahmed Hammouch Copyright © 2015 Youssef Lahbabi et al. All rights reserved. On the Feasibility of Unlicensed Communications in the TV White Space: Field Measurements in the UHF Band Mon, 23 Feb 2015 08:50:13 +0000 In practical unlicensed communications in TV band, radio devices have to identify, at first, the transmission opportunities, that is, the portion of the spectrum licensed for broadcasting services unoccupied in a certain region at certain time, that is, the so-called TV white space. In this paper the outcome of field measurements in the UHF TV band (470–860 MHz) conducted in EU is presented. To obtain empirical values for the parameters upon which unlicensed radio devices are able to distinguish in a real scenario between empty and occupied TV channels, signal power measurements have been performed in Italy, Spain, and Romania on rural, suburban, and urban sites, at different heights over the ground by using different analysis bandwidths. The aim of this work is to provide a set of practical parameters upon which harmless unlicensed communication in the UHF TV white space is feasible. The results have been analyzed with respect to the hidden node margin problem, spectrum sensing bandwidth, and occupancy threshold. M. Fadda, V. Popescu, M. Murroni, P. Angueira, and J. Morgade Copyright © 2015 M. Fadda et al. All rights reserved. Generalized Block-Diagonalization Schemes for MIMO Relay Broadcasting Systems Wed, 31 Dec 2014 00:10:07 +0000 We propose two generalized block-diagonalization (BD) schemes for multiple-input multiple-output (MIMO) relay broadcasting systems with no channel state information (CSI) at base station. We first introduce a generalized zero forcing (ZF) scheme that reduces the complexity of the traditional BD scheme. Then the optimal power loading matrix for the proposed scheme is analyzed and the closed-form solution is derived. Furthermore, an enhanced scheme is proposed by employing the minimum-mean-squared-error (MMSE) criterion. Simulation results show that the proposed generalized MMSE scheme outperforms the other schemes and the optimal power loading scheme improves the sum-rate performance efficiently. Xianan Wang, Xiaoxiang Wang, Wenrong Gong, and Zijia Huang Copyright © 2014 Xianan Wang et al. All rights reserved. Decision Feedback Blind Equalizer with Tap-Leaky Whitening for Stable Structure-Criterion Switching Wed, 31 Dec 2014 00:10:04 +0000 The research presented in this paper improves the structure-criterion switching performance of the blind decision feedback equalizer (DFE) which eliminates error propagation effects by optimizing both the structure and the cost criterion. To conquer the complexity of the 64-QAM (quadrature amplitude modulated) signal constellation, the stochastic entropy-gradient algorithm is additionally regularized by the coefficient leaky term to avoid a coefficients norm overgrowth of the received signal whitener. Effectively, the leak of coefficients is employed to ensure a stable structure-criterion switching of DFE between blind and decision-directed operation modes. The optimization of the resulting whitening algorithm is achieved by means of two free, leaky and entropic, parameters which act in opposition to each other. Both, the influence of the 64-QAM signal on the feedback filter behavior and the parametric optimization of the whitening algorithm are analyzed through simulations. Vladimir R. Krstić and Miroslav L. Dukić Copyright © 2014 Vladimir R. Krstić and Miroslav L. Dukić. All rights reserved. A New QIM-Based Watermarking Method Robust to Gain Attack Thu, 11 Sep 2014 09:59:35 +0000 We propose a new watermarking method based on quantization index modulation. A concept of initial data loss is introduced in order to increase capacity of the watermarking channel under high intensity additive white Gaussian noise. According to the concept some samples in predefined positions are ignored even though this produces errors in the initial stage of watermark embedding. The proposed method also exploits a new form of distribution of quantized samples where samples that interpret “0” and “1” have differently shaped probability density functions. Compared to well-known watermarking schemes, this provides an increase of capacity under noise attack and introduces a distinctive feature. Two criteria are proposed that express the feature numerically. The criteria are utilized by a procedure for estimation of a gain factor after possible gain attack. Several state-of-the-art quantization-based watermarking methods were used for comparison on a set of natural grayscale images. The superiority of the proposed method has been confirmed for different types of popular attacks. Yevhen Zolotavkin and Martti Juhola Copyright © 2014 Yevhen Zolotavkin and Martti Juhola. All rights reserved. Efficient Time-Frequency Localization of a Signal Mon, 25 Aug 2014 08:51:00 +0000 A new representation of the Fourier transform in terms of time and scale localization is discussed that uses a newly coined A-wavelet transform (Grigoryan 2005). The A-wavelet transform uses cosine- and sine-wavelet type functions, which employ, respectively, cosine and sine signals of length . For a given frequency , the cosine- and sine-wavelet type functions are evaluated at time points separated by on the time-axis. This is a two-parameter representation of a signal in terms of time and scale (frequency), and can find out frequency contents present in the signal at any time point using less computation. In this paper, we extend this work to provide further signal information in a better way and name it as -wavelet transform. In our proposed work, we use cosine and sine signals defined over the time intervals, each of length , , and are nonnegative integers, to develop cosine- and sine-type wavelets. Using smaller time intervals provides sharper frequency localization in the time-frequency plane as the frequency is inversely proportional to the time. It further reduces the computation for evaluating the Fourier transform at a given frequency. The A-wavelet transform can be derived as a special case of the -wavelet transform. Satish Chand Copyright © 2014 Satish Chand. All rights reserved. Spatial Multiple Description Coding for Scalable Video Streams Mon, 25 Aug 2014 07:53:15 +0000 The need for adapting video stream delivery over heterogeneous and unreliable networks requires self-adaptive and error resilient coding. Network bandwidth fluctuations can be handled by means of a video coding scheme which adapts to the channel conditions. However, packet losses which are frequent in wireless networks can cause a mismatch during the reconstruction in the receiver end and result in an accumulation of errors which deteriorates the quality of the delivered video. A combination of multiple description coding in pixel domain and scalable video coding schemes which addresses both video adaptation and robustness to data loss is proposed in this paper. The proposed scheme combines error concealment with spatial video scalability. In order to improve the fidelity of the reconstructed to the original frames in presence of packet loss, a multilayer polyphase spatial decomposition algorithm is proposed. Classical multiple description methods interpolate the missing data which results in smoothing and artifact at object boundaries. The proposed algorithm addresses the quality degradation due to low-pass filtering effect of interpolation methods. We also comparatively analyze the trade-off between robustness to channel errors and coding efficiency. Roya Choupani, Stephan Wong, and Mehmet Tolun Copyright © 2014 Roya Choupani et al. All rights reserved. A Model for Video Quality Assessment Considering Packet Loss for Broadcast Digital Television Coded in H.264 Thu, 03 Apr 2014 11:15:53 +0000 This paper presents a model to predict video quality perceived by the broadcast digital television (DTV) viewer. We present how noise on DTV can introduce individual transport stream (TS) packet losses at the receiver. The type of these errors is different than the produced on IP networks. Different scenarios of TS packet loss are analyzed, including uniform and burst distributions. The results show that there is a high variability on the perceived quality for a given percentage of packet loss and type of error. This implies that there is practically no correlation between the type of error or the percentage of packets loss and the perceived degradation. A new metric is introduced, the weighted percentage of slice loss, which takes into account the affected slice type in each lost TS packet. We show that this metric is correlated with the video quality degradation. A novel parametric model for video quality estimation is proposed, designed, and verified based on the results of subjective tests in SD and HD. The results were compared to a standard model used in IP transmission scenarios. The proposed model improves Pearson Correlation and root mean square error between the subjective and the predicted MOS. Jose Joskowicz and Rafael Sotelo Copyright © 2014 Jose Joskowicz and Rafael Sotelo. All rights reserved. Performance Evaluation of Concurrent Multipath Video Streaming in Multihomed Mobile Networks Mon, 26 Aug 2013 16:12:34 +0000 High-quality real-time video streaming to users in mobile networks is challenging due to the dynamically changing nature of the network paths, particularly the limited bandwidth and varying end-to-end delay. In this paper, we empirically investigate the performance of multipath streaming in the context of multihomed mobile networks. Existing schemes that make use of the aggregated bandwidth of multiple paths can overcome bandwidth limitations on a single path but suffer an efficiency penalty caused by retransmission of lost packets in reliable transport schemes or path switching overheads in unreliable transport schemes. This work focuses on the evaluation of schemes to permit concurrent use of multiple paths to deliver video streams. A comprehensive streaming framework for concurrent multipath video streaming is proposed and experimentally evaluated, using current state-of-the-art H.264 Scalable Video Coding (H.264/SVC) and the next generation High Efficiency Video Coding (HEVC) standards. It provides a valuable insight into the benefit of using such schemes in conjunction with encoder specific packet prioritisation mechanisms for quality-aware packet scheduling and scalable streaming. The remaining obstacles to deployment of concurrent multipath schemes are identified, and the challenges in realising HEVC based concurrent multipath streaming are highlighted. James Nightingale, Qi Wang, and Christos Grecos Copyright © 2013 James Nightingale et al. All rights reserved. Optimization of ATSC Mobile Handheld Service Capacity Sun, 24 Mar 2013 10:01:08 +0000 Mobile TV has become a reality offered on several mobile delivery systems. Among them is the Advanced Television System Committee (ATSC) system for mobile and handheld digital television services, known as ATSC Mobile DTV or ATSC M/H, which has moved from standardization to implementation. As the North American broadcast industry is preparing to provide Mobile DTV service to consumers, this work discusses important technical parameters that affect the TV service quality and capacity. Since additional error correction mechanisms were added to overcome mobile transmission problems, the available payload for M/H services is limited. This creates a need to efficiently use the available M/H bandwidth. The paper aims to optimize the Mobile DTV service capacity while maintaining an acceptable perceived quality. It presents tradeoffs between several factors affecting service capacity and signal robustness, which is prominent for designing Mobile TV broadcasting scenarios. Omneya Issa Copyright © 2013 Omneya Issa. All rights reserved. Bandwidth Management in Wireless Home Networks for IPTV Solutions Tue, 05 Mar 2013 10:55:14 +0000 The optimal allocation of the retransmission bandwidth is essential for IPTV service providers to ensure maximal service quality. This paper highlights the relevance of the wireless transport in today’s IPTV solution and discusses how this new media affects the existing broadcast technologies. A new Markovian channel model is developed to address the optimization issues of the retransmission throughput, and a new method is presented which is evaluated by empirical measurements followed by mathematical analysis. Tamás Jursonovics and Sándor Imre Copyright © 2013 Tamás Jursonovics and Sándor Imre. All rights reserved. Client-Driven Joint Cache Management and Rate Adaptation for Dynamic Adaptive Streaming over HTTP Wed, 27 Feb 2013 12:30:10 +0000 Due to the fact that proxy-driven proxy cache management and the client-driven streaming solution of Dynamic Adaptive Streaming over HTTP (DASH) are two independent processes, some difficulties and challenges arise in media data management at the proxy cache and rate adaptation at the DASH client. This paper presents a novel client-driven joint proxy cache management and DASH rate adaptation method, named CLICRA, which moves prefetching intelligence from the proxy cache to the client. Based on the philosophy of CLICRA, this paper proposes a rate adaptation algorithm, which selects bitrates for the next media segments to be requested by using the predicted buffered media time in the client. CLICRA is realized by conveying information on the segments that are likely to be fetched subsequently to the proxy cache so that it can use the information for prefetching. Simulation results show that the proposed method outperforms the conventional segment-fetch-time-based rate adaptation and the proxy-driven proxy cache management significantly not only in streaming quality at the client but also in bandwidth and storage usage in proxy caches. Chenghao Liu, Miska M. Hannuksela, and Moncef Gabbouj Copyright © 2013 Chenghao Liu et al. All rights reserved. PAPR Reduction of OFDM Signals by Novel Global Harmony Search in PTS Scheme Thu, 06 Dec 2012 13:54:10 +0000 The orthogonal frequency division multiplexing (OFDM) modulation technique is one of the key strategies for multiuser signal transmission especially in smart grids and wind farms. This paper introduces an approach for peak-to-average power ratio (PAPR) reduction of such signals based on novel global harmony search (NGHS) and partial transmit sequence (PTS) schemes. In PTS technique, the data block to be transmitted is partitioned into disjoint subblocks, which are combined using phase factors to minimize PAPR. The PTS requires an exhaustive search over all combinations of allowed phase factors. Therefore, with respect to the fast implementation and simplicity of NGHS technique, we could achieve significant reduction of PAPR. Hojjat Salehinejad and Siamak Talebi Copyright © 2012 Hojjat Salehinejad and Siamak Talebi. All rights reserved. IPTV: Technology, Practice, and Service Sun, 26 Aug 2012 08:29:00 +0000 Hsiang-Fu Yu, Jen-Wen Ding, Pin-Han Ho, and János Tapolcai Copyright © 2012 Hsiang-Fu Yu et al. All rights reserved. Background Traffic-Based Retransmission Algorithm for Multimedia Streaming Transfer over Concurrent Multipaths Mon, 13 Aug 2012 10:21:32 +0000 The content-rich multimedia streaming will be the most attractive services in the next-generation networks. With function of distribute data across multipath end-to-end paths based on SCTP's multihoming feature, concurrent multipath transfer SCTP (CMT-SCTP) has been regarded as the most promising technology for the efficient multimedia streaming transmission. However, the current researches on CMT-SCTP mainly focus on the algorithms related to the data delivery performance while they seldom consider the background traffic factors. Actually, background traffic of realistic network environments has an important impact on the performance of CMT-SCTP. In this paper, we firstly investigate the effect of background traffic on the performance of CMT-SCTP based on a close realistic simulation topology with reasonable background traffic in NS2, and then based on the localness nature of background flow, a further improved retransmission algorithm, named RTX_CSI, is proposed to reach more benefits in terms of average throughput and achieve high users' experience of quality for multimedia streaming services. Yuanlong Cao, Changqiao Xu, Jianfeng Guan, and Hongke Zhang Copyright © 2012 Yuanlong Cao et al. All rights reserved. Secure and Reliable IPTV Multimedia Transmission Using Forward Error Correction Sun, 08 Jul 2012 10:42:03 +0000 With the wide deployment of Internet Protocol (IP) infrastructure and rapid development of digital technologies, Internet Protocol Television (IPTV) has emerged as one of the major multimedia access techniques. A general IPTV transmission system employs both encryption and forward error correction (FEC) to provide the authorized subscriber with a high-quality perceptual experience. This two-layer processing, however, complicates the system design in terms of computational cost and management cost. In this paper, we propose a novel FEC scheme to ensure the secure and reliable transmission for IPTV multimedia content and services. The proposed secure FEC utilizes the characteristics of FEC including the FEC-encoded redundancies and the limitation of error correction capacity to protect the multimedia packets against the malicious attacks and data transmission errors/losses. Experimental results demonstrate that the proposed scheme obtains similar performance compared with the joint encryption and FEC scheme. Chi-Huang Shih, Yeong-Yuh Xu, and Yao-Tien Wang Copyright © 2012 Chi-Huang Shih et al. All rights reserved. Automatic Story Segmentation for TV News Video Using Multiple Modalities Thu, 05 Jul 2012 10:04:20 +0000 While video content is often stored in rather large files or broadcasted in continuous streams, users are often interested in retrieving only a particular passage on a topic of interest to them. It is, therefore, necessary to split video documents or streams into shorter segments corresponding to appropriate retrieval units. We propose here a method for the automatic segmentation of TV news videos into stories. A-multiple-descriptor based segmentation approach is proposed. The selected multimodal features are complementary and give good insights about story boundaries. Once extracted, these features are expanded with a local temporal context and combined by an early fusion process. The story boundaries are then predicted using machine learning techniques. We investigate the system by experiments conducted using TRECVID 2003 data and protocol of the story boundary detection task, and we show that the proposed approach outperforms the state-of-the-art methods while requiring a very small amount of manual annotation. Émilie Dumont and Georges Quénot Copyright © 2012 Émilie Dumont and Georges Quénot. All rights reserved. QoS Supported IPTV Service Architecture over Hybrid-Tree-Based Explicit Routed Multicast Network Tue, 03 Jul 2012 08:43:47 +0000 With the rapid advance in multimedia streaming and multicast transport technology, current IP multicast protocols, especially PIM-SM, become the major channel delivery mechanism for IPTV system over Internet. The goals for IPTV service are to provide two-way interactive services for viewers to select popular program channel with high quality for watching during fast channel surfing period. However, existing IP multicast protocol cannot meet above QoS requirements for IPTV applications between media server and subscribers. Therefore, we propose a cooperative scheme of hybrid-tree based on explicit routed multicast, called as HT-ERM to combine the advantages of shared tree and source tree for QoS-supported IPTV service. To increase network utilization, the constrained shortest path first (CSPF) routing algorithm is designed for construction of hybrid tree to deliver the high-quality video stream over watching channel and standard quality over surfing channel. Furthermore, the Resource Reservation Protocol- Traffic Engineering (RSVP-TE) is used as signaling mechanism to set up QoS path for multicast channel admission control. Our simulation results demonstrated that the proposed HT-ERM scheme outperforms other multicast QoS-based delivery scheme in terms of channel switching delay, resource utilization, and blocking ratio for IPTV service. Chih-Chao Wen and Cheng-Shong Wu Copyright © 2012 Chih-Chao Wen and Cheng-Shong Wu. All rights reserved. Rate Adaptive Selective Segment Assignment for Reliable Wireless Video Transmission Wed, 27 Jun 2012 10:41:27 +0000 A reliable video communication system is proposed based on data partitioning feature of H.264/AVC, used to create a layered stream, and LT codes for erasure protection. The proposed scheme termed rate adaptive selective segment assignment (RASSA) is an adaptive low-complexity solution to varying channel conditions. The comparison of the results of the proposed scheme is also provided for slice-partitioned H.264/AVC data. Simulation results show competitiveness of the proposed scheme compared to optimized unequal and equal error protection solutions. The simulation results also demonstrate that a high visual quality video transmission can be maintained despite the adverse effect of varying channel conditions and the number of decoding failures can be reduced. Sajid Nazir, Dejan Vukobratović, Vladimir Stanković, and Ivan Andonović Copyright © 2012 Sajid Nazir et al. All rights reserved. A Secure and Stable Multicast Overlay Network with Load Balancing for Scalable IPTV Services Thu, 07 Jun 2012 11:05:11 +0000 The emerging multimedia Internet application IPTV over P2P network preserves significant advantages in scalability. IPTV media content delivered in P2P networks over public Internet still preserves the issues of privacy and intellectual property rights. In this paper, we use SIP protocol to construct a secure application-layer multicast overlay network for IPTV, called SIPTVMON. SIPTVMON can secure all the IPTV media delivery paths against eavesdroppers via elliptic-curve Diffie-Hellman (ECDH) key exchange on SIP signaling and AES encryption. Its load-balancing overlay tree is also optimized from peer heterogeneity and churn of peer joining and leaving to minimize both service degradation and latency. The performance results from large-scale simulations and experiments on different optimization criteria demonstrate SIPTVMON's cost effectiveness in quality of privacy protection, stability from user churn, and good perceptual quality of objective PSNR values for scalable IPTV services over Internet. Tsao-Ta Wei, Chia-Hui Wang, Yu-Hsien Chu, and Ray-I Chang Copyright © 2012 Tsao-Ta Wei et al. All rights reserved. Video Classification and Adaptive QoP/QoS Control for Multiresolution Video Applications on IPTV Wed, 30 May 2012 10:51:39 +0000 With the development of heterogeneous networks and video coding standards, multiresolution video applications over networks become important. It is critical to ensure the service quality of the network for time-sensitive video services. Worldwide Interoperability for Microwave Access (WIMAX) is a good candidate for delivering video signals because through WIMAX the delivery quality based on the quality-of-service (QoS) setting can be guaranteed. The selection of suitable QoS parameters is, however, not trivial for service users. Instead, what a video service user really concerns with is the video quality of presentation (QoP) which includes the video resolution, the fidelity, and the frame rate. In this paper, we present a quality control mechanism in multiresolution video coding structures over WIMAX networks and also investigate the relationship between QoP and QoS in end-to-end connections. Consequently, the video presentation quality can be simply mapped to the network requirements by a mapping table, and then the end-to-end QoS is achieved. We performed experiments with multiresolution MPEG coding over WIMAX networks. In addition to the QoP parameters, the video characteristics, such as, the picture activity and the video mobility, also affect the QoS significantly. Huang Shyh-Fang Copyright © 2012 Huang Shyh-Fang. All rights reserved. Adjustable Two-Tier Cache for IPTV Based on Segmented Streaming Mon, 21 May 2012 11:19:20 +0000 Internet protocol TV (IPTV) is a promising Internet killer application, which integrates video, voice, and data onto a single IP network, and offers viewers an innovative set of choices and control over their TV content. To provide high-quality IPTV services, an effective strategy is based on caching. This work proposes a segment-based two-tier caching approach, which divides each video into multiple segments to be cached. This approach also partitions the cache space into two layers, where the first layer mainly caches to-be-played segments and the second layer saves possibly played segments. As the segment access becomes frequent, the proposed approach enlarges the first layer and reduces the second layer, and vice versa. Because requested segments may not be accessed frequently, this work further designs an admission control mechanism to determine whether an incoming segment should be cached or not. The cache architecture takes forward/stop playback into account and may replace the unused segments under the interrupted playback. Finally, we conduct comprehensive simulation experiments to evaluate the performance of the proposed approach. The results show that our approach can yield higher hit ratio than previous work under various environmental parameters. Kai-Chun Liang and Hsiang-Fu Yu Copyright © 2012 Kai-Chun Liang and Hsiang-Fu Yu. All rights reserved. Monitoring Accessibility Services in Digital Television Wed, 16 May 2012 08:29:24 +0000 This paper addresses methodology and tools applied to the monitoring of accessibility services in digital television at a time when the principles of accessibility and design are being considered in all new audiovisual media communication services. The main objective of this research is to measure the quality and quantity of existing accessibility services offered by digital terrestrial television (DTT). The preliminary results, presented here, offer the development of a prototype for automatic monitoring and a methodology for obtaining quality measurements, along with the conclusions drawn by initial studies carried out in Spain. The recent approval of the UN Convention on the Rights of Persons with Disabilities gives special relevance to this research because it provides valuable guidelines to help set the priorities to improve services currently available to users. Francisco Utray, Mercedes de Castro, Lourdes Moreno, and Belén Ruiz-Mezcua Copyright © 2012 Francisco Utray et al. All rights reserved. A Seamless Broadcasting Scheme with Live Video Support Tue, 24 Apr 2012 07:55:42 +0000 Broadcasting schemes, such as the fast broadcasting and harmonic broadcasting schemes, significantly reduce the bandwidth requirement of video-on-demand services. In the real world, some history events are very hot. For example, every year in March, thousands of people connect to Internet to watch the live show of Oscar Night. Such actions easily cause the networks contested. However, the schemes mentioned previously cannot alleviate the problem because they do not support live broadcasting. In this paper, we analyze the requirements for transferring live videos. Based on the requirements, a time skewing approach is proposed to enable the broadcasting schemes to support live broadcasting. However, the improved schemes require extra bandwidth for live broadcasting once the length of live shows exceeds the default. Accordingly, we proposed a scalable binomial broadcasting scheme to transfer live videos using constant bandwidth by increasing clients’ waiting time. When the scheme finds that the length of a video exceeds the default, it doubles the length of to-be-played segments and then its required bandwidth is constant. Zeng-Yuan Yang, Yi-Ming Chen, and Li-Ming Tseng Copyright © 2012 Zeng-Yuan Yang et al. All rights reserved. An Efficient Periodic Broadcasting with Small Latency and Buffer Demand for Near Video on Demand Mon, 09 Apr 2012 10:16:50 +0000 Broadcasting Protocols can efficiently transmit videos that simultaneously shared by clients with partitioning the videos into segments. Many studies focus on decreasing clients' waiting time, such as the fixed-delay pagoda broadcasting (FDPB) and the harmonic broadcasting schemes. However, limited-capability client devices such as PDAs and set-top boxes (STBs) suffer from storing a significant fraction of each video while it is being watched. How to reduce clients' buffer demands is thus an important issue. Related works include the staircase broadcasting (SB), the reverse fast broadcasting (RFB), and the hybrid broadcasting (HyB) schemes. This work improves FDPB to save client buffering space as well as waiting time. In comparison with SB, RFB, and HyB, the improved FDPB scheme can yield the smallest waiting time under the same buffer requirements. Ying-Nan Chen and Li-Ming Tseng Copyright © 2012 Ying-Nan Chen and Li-Ming Tseng. All rights reserved. Communications and Networking for Smart Grid: Technology and Practice Thu, 05 Apr 2012 09:00:57 +0000 Chi Zhou, Hossam S. Hassanein, Robert Qiu, and Pierangela Samarati Copyright © 2011 Chi Zhou et al. All rights reserved. Efficient Wireless Broadcasting through Joint Network Coding and Beamforming Sun, 18 Mar 2012 15:00:28 +0000 We develop a framework that exploits network coding (NC) and multiple-input/multiple-output (MIMO) techniques, jointly together, to improve throughput of downlink broadcast channels. Specifically, we consider a base station (BS) equipped with multiple transmit antennas that serves multiple mobile stations (MSs) simultaneously by generating multiple signal beams. Given the large number of MSs and the small number of transmit antennas, the BS must decide, at any transmission opportunity, which group of MSs it should transmit packets to, in order to maximize the overall throughput. We propose two algorithms for grouping MSs that take advantage of NC and the orthogonality of user channels to improve the overall throughput. Our results indicate that the proposed techniques increase the achievable throughput significantly, especially in highly lossy environments. Monchai Lertsutthiwong, Thinh Nguyen, and Bechir Hamdaoui Copyright © 2012 Monchai Lertsutthiwong et al. All rights reserved.