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The problem of optimizing access and bandwidth sharing among Transmission Control Protocol (TCP) connections in the mobile digital video broadcasting return channel via satellite (DVB-RCS) is tackled in this paper. After sketching the general system architecture, we explicitly deal with the dynamic assignment of bandwidth to TCP connections on the return link, which is accomplished by a network control center (NCC) placed onboard the satellite. Mobile users access the satellite in multifrequency time-division multiple access (MF-TDMA), whereas they receive data from the NCC in time-division multiplexing (TDM). Two different techniques, based on deterministic and random access, are compared in terms of bandwidth usage and average completion time per connection, when the mobile user acts as both server and client. In the server case, to increase the TCP throughput, both packet-level forward error correction (FEC) on data sent by mobile users and a duplicated and delayed acknowledgment technique for TCP acknowledgment traffic from the NCC to the mobile users are applied. An analysis of the packet losses and a simulation campaign of file transfers by employing a realistic channel model has been carried out. The results of the analysis show the convenience of adopting a technique, in addition to the optimal data redundancy in different cases, such as the server or client role of users, their willingness to pay, the file size, and the environment type. [ABSTRACT FROM AUTHOR]

The requirements for future DVB-TIH networks demand that broadcasters design and deploy networks that provide ubiquitous reception in challenging indoors and other obstructed situations. It is essential that such networks are designed cost-effectively and with minimized environmental impact. The EC funded project PLUTO has since its start in 2006 explored the use of diversity to improve coverage in these difficult situations. The purpose of this paper is to investigate the performance of Transmit Delay Diversity (DD) with two antennas to improve the reception of DVB-TIH systems operating in different realistic propagation conditions through a series of tests using a SPIRENT SR5500 dual channel emulator. The relationship between correlation coefficient between channels, receiver velocity and diversity gain is investigated. It is shown that transmit delay diversity significantly improves the quality of reception particularly in simulated fast fading mobile broadcasting applications. This paper documents research conducted by Brunel University and Broadreach Systems. [ABSTRACT FROM AUTHOR]

In this paper, an efficient design of dual mode deinterleaver for both IEEE 802.16 and digital video broadcasting (DVB) standards is presented. The paper first proposes a systematic data allocation method for the design of matrix transposer which can be used to realize the block deinterleaver adopted by IEEE 802.16 based on the multi- bank memory architecture. In addition, multiple input/output data can be grouped together in order to further reduce the memory access frequency such that the required number of banks and ports for the memory can be both reduced. Similarly, the multi-bank memory design approach can also be applied for the byte-level convolutional deinterleaver adopted in DVB system by realizing the multiple delay branches as the circular buffer. Finally, these two different deinterleaving standards can be further integrated . into a single design suitable for those dual-mode communication systems. Our implementation results show that the dual mode deinterleaver can run up to 150 Mhz, and consume about 38.5k gates. The same design methodology can also be applied for the design of interleavers. [ABSTRACT FROM AUTHOR]

Due to the recent popularization of digital broadcasting systems, selective contents, i.e., watching contents selected by users themselves, have attracted great attention. For example, in a news program, after a user selects an interesting content, he/she watches it. In selective contents broadcasting, since the server needs to deliver many contents, the necessary bandwidth for continuously playing the data increases. Conventional schemes reduce the necessary bandwidth by producing an effective broadcast schedule. However, they do not consider the upper limit in the bandwidth. When an upper limit exists in the bandwidth, users may wait to play the data. In this paper, we propose a broadcasting scheme that reduces waiting time by considering available bandwidth. In our proposed scheme, by acquiring the channel bandwidth that is the same as the data consumption rate, we effectively reduce the waiting time. [ABSTRACT FROM AUTHOR]

LDPC codes are state-of-art error correcting codes, included in several standards for broadcast transmissions. Iterative soft-decision decoding algorithms for LDPC codes reach excellent error correction capability; their performance, however, is strongly affected by finite-precision issues in the representation of inner variables. Great attention has been paid, in recent literature, to the topic of quantization for LDPC decoders, but mostly focusing on binary modulations and analysing finite precision effects in a disaggregrated manner, i.e., considering separately each block of the receiver. Modern telecommunication standards, instead, often adopt high order modulation schemes, e.g. M-QAM, with the aim to achieve large spectral efficiency. This puts additional quantization problems, that have been poorly debated in previous literature. This paper discusses the choice of suitable quantization characteristics for both the decoder messages and the received samples in LDPC-coded systems using M-QAM schemes. The analysis involves also the demapper block, that provides initial likelihood values for the decoder, by relating its quantization strategy with that of the decoder. A new demapper version, based on approximate expressions, is also presented, that introduces a slight deviation from the ideal case but yields a low complexity hardware implementation. [ABSTRACT FROM AUTHOR]

This paper studies efficient and simple data broadcast in IEEE 802.15.4-based ad hoc networks (e.g., ZigBee). Since finding the minimum number of rebroadcast nodes in general ad hoc networks is NP-hard, current broadcast protocols either employ heuristic algorithms or assume extra knowledge such as position or two-hop neighbor table. However, the ZigBee network is characterized as low data rate and low cost. It cannot provide position or two-hop neighbor information, but it still requires an efficient broadcast algorithm that can reduce the number of rebroadcast nodes with limited computation complexity and storage space. To this end, this paper proposes self-pruning and forward node selection algorithms that exploit the hierarchical address space in ZigBee networks. Only one-hop neighbor information is needed; a partial list of two-hop neighbors is derived without exchanging messages between neighboring nodes. The ZigBee forward node selection algorithm finds the minimum rebroadcast nodes set with polynomial computation time and memory space. Using the proposed localized algorithms, it is proven that the entire network is covered. Simulations are conducted to evaluate the performance improvement in terms of the number of rebroadcast nodes, number of duplicated receivings, coverage time, and communication overhead. [ABSTRACT FROM AUTHOR]

In providing video-on-demand (VoD) services to a number of clients through networks, the bandwidth requirements of video transmission restrict VoD services. For this reason, many significant broadcasting-based VoD schemes have been proposed to efficiently support services. However, the broadcasting-based VoD schemes approach needs frequency channel hopping, using many channels at the same time and managing many segments of a video. These make it difficult to implement. In this paper, we propose a harmonic staggered broadcasting scheme which has a simple structure and substantially improved VoD efficiency. The proposed scheme substantially reduces the number of segments required and the frequency for switching channels. Also this new scheme performs significantly better than the existing VoD schemes in viewer's waiting time and buffer requirements with simplicity. The numerical results demonstrate that the viewer's waiting time of the harmonic staggered broadcasting scheme is close to the harmonic broadcasting scheme and the buffer requirements of this can be adjusted by a video dividing coefficient h. [ABSTRACT FROM AUTHOR]

DVB-H networks allow high data rate broadcast access for hand-held terminals. A method to analyze the performance is developed. The influence of different MPE-FEC rates and modulation schemes on the performance of a DVB-H network is analyzed in this paper for 9 different reception conditions. Portable (indoor and outdoor) and mobile reception (car, train, tram, bus) are investigated. This analysis enables better estimations of the performance of DYB-H systems and an optimized DVB-H performance model. The percentage of valid reception, MPE-FEC gains, carrier to interference-plus-noise ratios, and minimal signal strengths for the different reception conditions and modulation schemes are presented. [ABSTRACT FROM AUTHOR]

Recently, the use of a virtual backbone in various applications in mobile ad hoc networks (MANETs) has become popular. These applications include topology management, point and area coverage, and routing protocol design. In a MANET, one challenging issue is to construct a virtual backbone in a distributed and localized way while balancing several conflicting objectives: small approximation ratio, fast convergence, and low computation cost. Many existing distributed and localized algorithms select a virtual backbone without resorting to global or geographical information. However, these algorithms incur a high computation cost in a dense network. In this paper, we propose a distributed solution based on reducing the density of the network using two mechanisms: clustering and adjustable transmission range. By using adjustable transmission range, we also achieve another objective, energy-efficient design, as a by-product. As an application, we show an efficient broadcast scheme where nodes (and only nodes) in a virtual backbone are used to forward the broadcast message. The virtual backbone is constructed using Wu and Li's marking process [37] and the proposed density reduction process. The application of the density reduction process to other localized algorithms is also discussed. The efficiency of our approach is confirmed through both analytical and simulation study. [ABSTRACT FROM AUTHOR]

For mobile ad hoc networks, network-wide broadcast is a critical network layer function supporting route discovery and maintenance in many unicast and multicast protocols. A number of broadcast schemes have been proposed; however, almost all of them assume the usage of omnidirectional antennas and focus on broadcast overhead in terms of the number of forwarding nodes. Directional antennas have narrow beams and can potentially reduce broadcast overhead in terms of the ratio of the number of received duplicate packets to the number of nodes that receive broadcast packets. In this paper, we propose to map probability-based directional and omnidirectional broadcast to bond and site percolation, respectively, and describe a collection of directional antenna-based broadcast schemes for mobile ad hoc networks. A thorough and comparative simulation study is conducted to demonstrate the efficiency of the proposed schemes. [ABSTRACT FROM AUTHOR]

In this paper, we discuss energy efficient broadcast in ad hoc wireless networks. The problem of our concern is: Given an ad hoc wireless network, find a broadcast tree such that the energy cost of the broadcast tree is minimized. Each node in the network is assumed to have a fixed level of transmission power. We first prove that the problem is NP-hard and propose three heuristic algorithms, namely, shortest path tree heuristic, greedy heuristic, and node weighted Steiner tree-based heuristic, which are centralized algorithms. The approximation ratio of the node weighted Steiner tree-based heuristic is proven to be (1 + 2 In(n − 1)). Extensive simulations have been conducted and the results have demonstrated the efficiency of the proposed algorithms. [ABSTRACT FROM AUTHOR]

We consider a three-node network where a relay node establishes a bidirectional communication between the two other nodes using a spectrally efficient decode-and-forward protocol. In the first phase we have the classical multiple-access channel where both nodes transmit a message to the relay node, which then decodes the messages. In the second phase the relay broadcasts a re-encoded composition of them based on the network coding idea. This means that each receiving node uses the same data stream to infer on its intended message. We characterize the optimal transmit strategy for the broadcast phase where either the relay node or the two other nodes are equipped with multiple antennas. Our main result shows that beamforming into the subspace spanned by the channels is always an optimal transmit strategy for the multiple-input single-output bidirectional broadcast channel. Thereby, it shows that correlation between the channels is advantageous. Moreover, this leads to a parametrization of the optimal transmit strategy which specifies the whole capacity region. In retrospect the results are intuitively, clear since the single-beam transmit strategy reflects the single stream processing due to the network coding approach. [ABSTRACT FROM AUTHOR]

Broadcast is a fundamental operation in wireless networks, and naïve flooding is not practical, because it cannot deal with interference. Scheduling is a good way of avoiding interference, but previous studies on broadcast scheduling algorithms all assume highly theoretical models such as the unit disk graph model. In this work, we reinvestigate this problem by using the 2-Disk and the signal-to-interference-plus-noise-ratio (SINR) models. We first design a constant approximation algorithm for the 2-Disk model and then extend it to the SINR model. This result, to the best of our knowledge, is the first result on broadcast scheduling algorithms in the SINR model. [ABSTRACT FROM AUTHOR]

We investigate the optimal design of a multihop wireless mesh network equipped with multiple orthogonal wireless channels and multiple radios. Specifically, we focus on solutions that can efficiently utilize the limited resource to support multiple unicast applications by routing and network coding. We propose a cross-layer optimization framework where the broadcasting feature of the wireless environment, which plays an important role in realizing the achievable gain of network coding, is taken into account. Moreover, we propose a network code construction scheme based on linear programming, with which the possible achievable Coding+MAC gain could be significantly increased. Delay constraints are also included in the network code construction formulation so that the possible impact of the extra decoding delay to the TCP/IP performance can be reduced without changing the upper layer protocols. The proposed network design based on cross-layer optimization results in significant increase in network throughput, and our results can serve as an important guide for practical network design. [ABSTRACT FROM AUTHOR]

This work proposes a quality-oriented multimedia delivery framework that tackles the issue of optimizing video broadcasting and interactive video applications over packet networks with respect to both resource utilization and user perceived quality. Previous work showed that the quality of service requirements of multimedia applications can be optimally satisfied by pipeline forwarding of packets by keeping delay controlled and resource utilization high, while enabling highly scalable network devices. These properties are key in today networks to enable valuable (i.e., chargeable for) services and to avoid that the traffic increase due to broadband video either collapses existing networks or forces the deployment of high cost, cutting-edge technology to properly upgrade them. However, the current Internet is not based on such technology and its incremental introduction raises questions on how to handle video packets generated by pipeline-forwarding-unaware sources. This work proposes to use the perceptual importance of the carried video samples to determine which packets shall be transferred with pipeline forwarding-thus receiving deterministic service-and which with a traditional, e.g., best effort or differentiated service. Two new scheduling algorithms are proposed, with an extensive analysis and simulation results, which also investigate the impact of the encoding scheme. Performance bounds have been established by comparing the proposed algorithms with an exhaustive-search approach, showing that the performance is within 2 dB PSNR from the optimal solution in the worst case. [ABSTRACT FROM AUTHOR]

This work proposes a jointed mode detection and symbol detection scheme for DVB-T. To reduce hardware complexity, the division operation of normalized maximum correlation (NMC) is removed and the delay line which uses twisted memory access method lowers the hardware cost. In addition, the proposed detection procedure does not need to refill or replenish the received data samples; as the result, the longest latency of the detection is only 17280 samples and is comparable with the parallel method. To lower the hardware cost, the memory is released for channel estimation after completing the Mode/GI detection and symbol detection. Total complexity of Mode/GI/symbol detection and channel estimation is about 200 Kgates (including memory). [ABSTRACT FROM AUTHOR]

A partially cooperative relay broadcast channel (RBC) is a three-node network with one source node and two destination nodes (destinations 1 and 2) where destination 1 can act as a relay to assist destination 2. Inner and outer bounds on the capacity region of the discrete memoryless partially cooperative RBC are obtained. When the relay function is disabled, the inner bound reduces to an inner bound on the capacity region of broadcast channels that includes an inner bound of Marton, and Gel'fand and Pinsker. The outer bound reduces to a new outer bound on the capacity region of broadcast channels that generalizes an outer bound of Marton to include a common message, and that generalizes an outer bound of Gel'fand and Pinsker to apply to general discrete memoryless broadcast channels. The proof for the outer bound simplifies the proof of Gel'fand and Pinsker that was based on a recursive approach. Four classes of RBCs are studied in detail. For the partially cooperative RBC with degraded message sets, inner and outer bounds are obtained. For the semideterministic partially cooperative RBC and the orthogonal partially cooperative RBC, the capacity regions are established. For the parallel partially cooperative RBC with unmatched degraded subchannels, the capacity region is established for the case of degraded message sets. The capacity is also established when the source node has only a private message for destination 2, i.e., the channel reduces to a parallel relay channel with unmatched degraded subchannels. [ABSTRACT FROM AUTHOR]

Multiple transmit antennas in a downlink channel can provide tremendous capacity (i.e., multiplexing) gains, even when receivers have only single antennas. However, receiver and transmitter channel state information is generally required. In this correspondence, a system where each receiver has perfect channel knowledge, but the transmitter only receives quantized information regarding the channel instantiation is analyzed. The well-known zero-forcing transmission technique is considered, and simple expressions for the throughput degradation due to finite-rate feedback are derived. A key finding is that the feedback rate per mobile must be increased linearly with the signal-to-noise ratio (SNR) (in decibels) in order to achieve the full multiplexing gain. This is in sharp contrast to point-to-point multiple-input multiple-output (MIMO) systems, in which it is not necessary to increase the feedback rate as a function of the SNR. [ABSTRACT FROM AUTHOR]

The article discusses the wireless broadcasting of multimedia streaming technology within a framework that permits asynchronous media access. Mobile television and other wireless video broadcasting services users are experiencing a greening due to the advanced terminal capabilities, new network infrastructures and developments in media coding efficiency. With this, receivers subscribe at any time on the ongoing broadcast session, but are still able to show the media stream from the beginning. Thus, the media stream is sectioned and each segment is broadcast by a code. Each encoded segment is broadcast at different rates, resulting to asynchronous data reception and full reliability are attained at the same time.

To reduce the bandwidth of media-on-demand transmissions, different broadcasting techniques have been developed over the last years. For highly demanded media, proactive schemes have a lower bandwidth requirement compared to reactive ones. While some of the proactive schemes try to obtain an efficiency near to the theoretical limit, others have been developed to lower the bandwidth by partial preloading, additional playout delay, the use of breaks within the transmission or by exploiting bandwidth variations of variable-bit-rate media. In this article we describe how one of the most efficient proactive transmission schemes can further be improved and generalized so it supports all these additional enhancements and outperforms its predecessor and the specialized schemes. [ABSTRACT FROM AUTHOR]

Home network systems including a home gateway are expected to facilitate the convergence of broadcasting and communication services to complement the ubiquitous computing and services. We focus on supporting the convergence of broadcasting and communication in home network systems with an Ethernet passive optical network(EPON)-based home gateway. We propose a new architecture that integrates broadcasting and data services in a home network. For this architecture, we use an overlay transport mechanism in access network and IP multicast techniques of the Internet group management protocol(IGMP) and IGMP snooping in a home network. We also detail a set of mechanisms and procedures for a home broadcasting service through the home gateway system. Our new scheme is composed of three parts: a) an overlay transmission model of video broadcasting signals (satellite and/or cable TV) and Internet data, b) to select a specific video broadcasting channel and to make of the selected video broadcasting stream into IP multicast packets in tuner/conversion module using multiple tuner system and c) to transfer the converted IP multicast packets to L2 switch of home gateway's core module and to send them out to target port(s) by L2 multicast using IGMP snooping. [ABSTRACT FROM AUTHOR]