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We consider transmission over the ergodic fading multiple-antenna broadcast (MIMO-BC) channel with partial channel state information at the transmitter and full information at the receiver. Over the equivalent non-fading channel, capacity has recently been shown to be achievable using transmission schemes that were designed for the "dirty paper" channel. We focus on a similar "fading paper" model. The evaluation of the fading paper capacity is difficult to obtain. We confine ourselves to the linear-assignment capacity, which we define, and use convex analysis methods to prove that its maximizing distribution is Gaussian. We compare our fading-paper transmission to an application of dirty paper coding that ignores the partial state information and assumes the channel is fixed at the average fade. We show that a gain is easily achieved by appropriately exploiting the information. We also consider a cooperative upper bound on the sum-rate capacity as suggested by Sato. We present a numeric example that indicates that our scheme is capable of realizing much of this upper bound. [ABSTRACT FROM AUTHOR]

This letter presents two results for multiuser wireless systems employing dirty-paper coding strategies along with greedy scheduling over the broadcast multiple-input multiple-output channel. Specifically, an efficient and suboptimal downlink scheduler is proposed to approximate the maximum sum rate using equal power allocation, and it is shown to approach the maximum sum rate of optimal power allocation for a large number of users under optimal scheduling. The second result demonstrates that the average maximum sum rate can be tightly upper bounded when spatial multiplexing is maximized. [ABSTRACT FROM AUTHOR]

Cognitive radio promises a low-cost, highly flexible alternative to the classic single-frequency band, single-protocol wireless device. By sensing and adapting to its environment, such a device is able to fill voids in the wireless spectrum and can dramatically increase spectral efficiency. In this paper, the cognitive radio channel is defined as a two-sender, two-receiver interference channel in which sender 2 obtains the encoded message sender 1 plans to transmit. We consider two cases: in the genie-aided cognitive radio channel, sender 2 is noncausally presented the data to be transmitted by sender 1 while in the causal cognitive radio channel, the data is obtained causally. The cognitive radio at sender 2 may then choose to transmit simultaneously over the same channel, as opposed to waiting for an idle channel as is traditional for a cognitive radio. Our main result is the development of an achievable region which combines Gel'fand-Pinkser coding with an achievable region construction for the interference channel. In the additive Gaussian noise case, this resembles dirty-paper coding, a technique used in the computation of the capacity of the Gaussian multiple-input multiple-output (MIMO) broadcast channel. Numerical evaluation of the region in the Gaussian noise case is performed, and compared to an inner bound, the interference channel, and an outer bound, a modified Gaussian MIMO broadcast channel. Results are also extended to the case in which the message is causally obtained. [ABSTRACT FROM AUTHOR]

This paper focuses on the problem of broadcasting information in the most efficient manner in a large 2-D ad hoc wireless network at low SNR and under line-of-sight propagation. A new communication scheme is proposed, where source nodes first broadcast their data to the entire network, despite the lack of sufficient available power. The signal’s power is then reinforced via successive back-and-forth beamforming transmissions between different groups of nodes in the network, so that all nodes are able to decode the transmitted information at the end. This scheme is shown to achieve asymptotically the broadcast capacity of the network, which is expressed in terms of the largest singular value of the matrix of fading coefficients between the nodes in the network. A detailed mathematical analysis is then presented to evaluate the asymptotic behavior of this largest singular value. [ABSTRACT FROM PUBLISHER]

This paper deals with the secure communication issues of wireless cooperative networks in the presence of multiple friendly but selfish intermediate nodes. On account of the broadcast nature of wireless communications, it is assailable to malicious eavesdropping. To tackle this challenge in the paper, we present a relay and jammer selection strategy that selects the jammer and relay nodes from intermediate nodes to improve the security of the eavesdropping attacks. The jammer is used to broadcast artificial interference noise on the eavesdropper. The relay acts as a traditional relay that retransmits source signal from the source to the intended destination. For achieving the maximum secrecy capacity by the selected nodes, we introduce a power allocation approach of intermediate nodes that is formulated as a Bertrand game based on price competition. We prove that an optimal pricing scheme can maximize the secrecy capacity and achieve the optimal profits for the selfish friendly nodes. Then, a new particle swarm with simulated anneal optimization algorithm is employed to obtain the solution of pricing and node selection. Finally, the simulation results verify our theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper presents an analytical study of the stable throughput for multiple broadcast sessions in a multi-hop wireless tandem network with random access. Intermediate nodes leverage on the broadcast nature of wireless medium access to perform inter-session network coding among different flows. This problem is challenging due to the interaction among nodes, and has been addressed so far only in the saturated mode where all nodes always have packet to send, which results in infinite packet delay. In this paper, we provide a novel model based on multi-class queueing networks to investigate the problem in unsaturated mode. We devise a theoretical framework for computing maximum stable throughput of network coding for a slotted ALOHA-based random access system. Using our formulation, we compare the performance of network coding and traditional routing. Our results show that network coding leads to high throughput gain over traditional routing. We also define a new metric, network unbalance ratio (NUR), that indicates the unbalance status of the utilization factors at different nodes. We show that although the throughput gain of the network coding compared to the traditional routing decreases when the number of nodes tends to infinity, NUR of the former outperforms the latter. We carry out simulations to confirm our theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper studies the fundamental properties of broadcasting in multihop wireless networks. Previous studies have shown that, as long as broadcast capacity is concerned, asymptotically optimal broadcasting is possible in wireless multihop networks under very general conditions. However, none of the existing work on broadcast capacity has considered latency in message delivery, which is simply assumed to be finite (but not explicitly bounded). In this paper, the issue of investigating the fundamental properties of broadcast communications for what concerns both capacity and latency using a realistic, SINR-based interference model is investigated. In particular, a novel topological notion of network connectivity is introduced, and it is shown that, if the network satisfies this property, asymptotically optimal broadcast capacity and latency can be achieved simultaneously. The above result holds in the general scenario in which an arbitrary number of broadcast sources arbitrarily share the available (optimal) network capacity. The result presented in this paper is in sharp contrast to similar results obtained for the case of unicast transmissions, where asymptotically optimal latency in message delivery can be achieved only at the expense of asymptotically reducing network capacity. Thus, the results presented in this paper show that scalable broadcasting in multihop wireless networks is, in principle, possible. [ABSTRACT FROM AUTHOR]

Audience research is a vital part of TV and radio broadcasting, as well as of the more recent forms of media content delivery, such as the Internet, IPTV, mobile phones, Personal Video Recorders (PVRs) and portable media viewers. The uses of audience research range from self-promotion to refining service offerings and setting advertising rates. Without reliable audience data, many businesses will be reluctant to participate in the new platforms. This paper describes an end-to-end system for convergent audience measurement focused on IPTV but covering also terrestrial, cable, satellite and mobile broadcasting. We created the audience measurement system from the elaboration of a logical architectural model and a common data model which can be applied to any media scenario. We implemented this logical and data model in stationary and mobile media receivers (in the paper the particular case of IPTV is extensively explained). In addition user consumption is modeled and metrics are provided for user media consumption profiling and impact quantification in IPTV environments. [ABSTRACT FROM AUTHOR]

In multiple-antenna broadcast channels, unlike point-to-point multiple-antenna channels, the multiuser capacity depends heavily on whether the transmitter knows the channel coefficients to each user. For instance, in a Gaussian broadcast channel with M transmit antennas and n single-antenna users, the sum rate capacity scales like M log log n for large n if perfect channel state information (CSI) is available at the transmitter, yet only logarithmically with M if it is not. In systems with large n, obtaining full CSI from all users may not be feasible. Since lack of CSI does not lead to multiuser gains, it is therefore of interest to investigate transmission schemes that employ only partial CSI. In this paper, we propose a scheme that constructs M random beams and that transmits information to the users with the highest signal-to-noise-plus-interference ratios (SINRs), which can be made available to the transmitter with very little feedback. For fixed M and n increasing, the throughput of our scheme scales as M log log nN, where N is the number of receive antennas of each user. This is precisely the same scaling obtained with perfect CSI using dirty paper coding. We furthermore show that a linear increase in throughput with M can be obtained provided that M does not not grow faster than log n. We also study the fairness of our scheduling in a heterogeneous network and show that, when M is large enough, the system becomes interference dominated and the probability of transmitting to any user converges to &frac1n;, irrespective of its path loss. In fact, using M = α log n transmit antennas emerges as a desirable operating point, both in terms of providing linear scaling of the throughput with M as well as in guaranteeing fairness. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surface (RIS), a recently introduced technology for future wireless communication systems, enhances the spectral and energy efficiency by intelligently adjusting the propagation conditions between base stations (BSs) and mobile equipments (MEs). An RIS consists of many low-cost passive reflecting elements that are optimized to improve the quality of the received signal. In this paper, we study the problem of power control at the BS and RIS optimization for application to physical-layer broadcasting. Our goal is to minimize the transmit power at the BS by jointly designing the transmit beamforming at the BS and the phase shifts of the passive elements at the RIS. Furthermore, to help validate the proposed optimization methods, we derive lower bounds to quantify the average transmit power at the BS as a function of the number of MEs, the number of RIS elements, and the number of antennas at the BS. The simulation results demonstrate that the average transmit power at the BS is close to the lower bound in an RIS-aided system, and is significantly lower than the average transmit power in conventional schemes without an RIS. [ABSTRACT FROM AUTHOR]

The new ways to consume and deliver media content in a wireless environment have led to a significant increase in the demand for spectrum resources. In addition, the arrival of next-generation wireless communication technologies has encouraged the creating of new verticals targeting novel applications, such as industry IoT, e-health, distance learning, smart city, smart-metering. All these new use cases are centred on an IP-based infrastructure. A promising alternative to satisfy the demand for resources is to incorporate a new delivery mechanism that can alleviate the congestion of classical cell-based point-to-point broadband wireless infrastructures. The best-positioned candidate is the next-generation Digital Terrestrial Television system, which offers a very spectrum efficient one-to-many PHY, and for the first time, native IP support. In ATSC 3.0, the whole system was designed with an IP-centric view, whereas DVB has created standards to deliver services to generic IP devices (DVB-I). Nevertheless, there is still a last missing piece to bring the broadcast infrastructure to the IP-connected world: a Broadcast Core Network (BCN). In this paper, the basics of a BCN are presented with new use cases that are attractive to Broadcast Network Operator (BNO). A possible roadmap towards implementation is described, and a service-based architecture for a BCN is presented and discussed. [ABSTRACT FROM AUTHOR]

This paper describes systems, devices, and methods to implement a bi-directional integrated inter-tower wireless communications network (IITWCN). The described technology can be implemented in combination with the Broadcast Core Network (BCN) in next generation broadcast eco-system and, therefore, support new business cases for broadcast operators such as the delivery of flexible datacasting services or support broadcast or point-to-point Internet services. The introduced bi-directional inter-tower communications network (ITCN) extends the previous unidirectional in-band distribution links (IDL) and adopts the on-channel repeater (OCR) as a simplified backhaul solution in single frequency networks (SFN). The concept of the coordinated ITCN is also presented, aiming at future broadcast Internet services. The ITCN provides a scalable and configurable network solution embedded in a broadcast system, which becomes independent from any non-broadcasting telecommunication infrastructure. The described technology partially relies on the infrastructure of the underlying broadcast/multicast network, using the allocated service channels without requiring additional frequency bands or a separate frequency band. The bi-directional inter-transmitter communication links are therefore referred to as integrated transmission links and the corresponding network as an integrated network. [ABSTRACT FROM AUTHOR]

In a multihop mobile ad hoc network, broadcasting is an elementary operation to support many applications. In [15], it is shown that naively broadcasting by flooding may cause serious redundancy, contention, and collision in the network, which we refer to as the broadcast storm problem. Several threshold-based schemes are shown to perform better than flooding in that work. However, how to choose thresholds also poses a dilemma between reachability and efficiency under different host densities. In this paper, we propose several adaptive schemes, which can dynamically adjust thresholds based on local connectivity information. Simulation results show that these adaptive schemes can offer better reachability as well as efficiency as compared to the results in [15]. [ABSTRACT FROM AUTHOR]

To meet the ever increasing demand for better service quality and availability, the next generation digital TV (DTV) broadcast, a.k.a., the ATSC 3.0, is developed with new capabilities to deliver 4K ultra-high-definition (4K-UHD) services to fixed receivers, robust HD-quality services to mobile receivers, as well as non-broadcast services (e.g., broadband), including Internet of Things (IoT), Connected Vehicles, etc. To realize these capabilities, it becomes necessary to evolve the existing single-transmitter high-power-high-tower (HPHT) network to multi-transmitter low-power-low-tower single-frequency-networks (SFN), which requires installing new transmitters. Each new transmitter needs a feederlink to receive the service data from the broadcast gateway (BG) for transmission. This feederlink contributes to a significant portion of installation and operational costs of the new transmitters. This paper proposes a wireless in-band distribution link (WIDL) technology, where the distribution data is delivered to the newly deployed transmitters from the existing DTV towers wirelessly sharing the same TV band with the broadcast services. The distribution signal is multiplexed with service signal in the same ATSC 3.0 waveform. Layered division multiplexing (LDM) technology is proposed to achieve more efficient transmission of the distribution signal. The WIDL offers better performance and more robust operation than the on-channel repeater (OCR) technologies. More importantly, it offers the possibility of delivering backhaul data for future applications over the DTV infrastructure, such as IoT and connected vehicles. Therefore, the proposed WIDL is one enabling technology to achieve convergence of broadcast services with broadband and other wireless services on the DTV spectrum. [ABSTRACT FROM AUTHOR]

This paper considers the transmission of scheduling information in orthogonal frequency-division multiple-access (OFDMA)-based cellular communication systems such as the Third-Generation Partnership Project (3GPP) long-term evolution (LTE). These systems provide efficient usage of radio resources by allowing users to be dynamically scheduled in both frequency and time. This requires considerable amounts of scheduling information to be sent to the users. This paper compares two basic transmission strategies: transmitting a separate scheduling message to each user versus broadcasting a joint scheduling message to all users. Different scheduling granularities are considered, as are different scheduling algorithms. The schemes are evaluated in the context of the LTE downlink using multiuser system simulations, assuming a full-buffer situation. The results show that separate transmission of the scheduling information requires a slightly lower overhead than joint broadcasting when proportional fair scheduling is employed and the users are spread out over the cell area. The results also indicate that the scheduling granularity standardized for LTE provides a good tradeoff between scheduling granularity and overhead. [ABSTRACT FROM PUBLISHER]

It has been shown that random beamforming using partial channel state information (CSI) achieves the same throughput scaling as obtained from dirty paper coding for a broadcast (downlink) channel with M transmit antennas and K users where K is large [1]. In this paper, we apply this scheme to wideband MIMO broadcast channels. By using OFDM, an L-tap wideband channel can be decomposed to N parallel narrowb- and channels (subcarriers), where N > L. Neighboring subcarriers are highly correlated. Therefore, we consider neighboring subcarriers as a cluster and find the closed form solution for the joint characteristic function of SINR values at two subcarriers in a cluster. We show numerically how the knowledge of the quality of the center subcarrier sheds light about the quality of other subcarriers in the same cluster, and address the issue of cluster size. In addition, through complex and asymptotic analysis, we show that for cluster size of order N/L√logR (for large K), users need only feedback the best SINR at the center subcarrier of each cluster in order for the transmitter to perform opportunistic beamforming and maintain the same throughput scaling as when full CSI is available. Using simulation results, we verify our analytical result and show that even fewer feedback can be tolerated, and larger clusters (N/2L) can be implemented for a small throughput hit. [ABSTRACT FROM AUTHOR]

This paper proposes an architecture for using multiple-input multiple-output techniques for a multimode fiber broadcast channel, allowing simultaneous transmission of unique streams to different users on the same fiber while using square-last detection. The resulting system throughput scales nearly linearly with the number of transmitters and receivers. The paper also proposes a training scheme appropriate for use with square-law detection. [ABSTRACT FROM AUTHOR]

This paper studies the two-hop relay broadcast channel (BC) for a relay-assisted wireless cellular network where the multiuser independent downlink signals from the base station (BS) are first transmitted to a fixed relay station (RS), and then forwarded by the RS to multiple mobile users. Assuming both the BS and RS are equipped with multiantennas, we study the joint optimization of linear beamforming and power control at the BS and RS so as to minimize their weighted sum-power consumption under the user minimum signal-to-interference-noise-ratio (SINR) - quality-of-service (QoS) - constraints. We apply two well-known criteria in the literature, namely, the "SINR balancing" and the "channel-inversion," for the design of linear precoding in the traditional nonrelay-assisted multiantenna BC to the relay-assisted multiantenna BC. First, a convergence-ensured iterative SINR-balancing algorithm is proposed to successively in turn optimize the transmit parameters at one station (BS or RS) with those at the other station being fixed. Second, a joint BS and RS channel-inversion algorithm is proposed together with a novel technique, termed "eigenmode switching," at the RS to reduce the power penalty of the channel inversion. Simulation results show that the proposed joint beamforming and power control schemes provide substantial power savings to achieve the assigned user QoS constraints. [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]

Self-healing key distribution schemes allow group managers to broadcast session keys to large and dynamic groups of users over unreliable channels. Roughly speaking, even if during a certain session some broadcast messages are lost due to network faults, the self-healing property of the scheme enables each group member to recover the key from the broadcast messages he has received before and after that session. Such schemes are quite suitable in supporting secure communication in wireless networks and mobile wireless ad-hoc networks. Recent papers have focused on self-healing key distribution, and have provided definitions, stated in terms of the entropy function, and some constructions. The contribution of this paper is the following. • We analyze current definitions of self-healing key distribution and, for two of them, we show that no protocol can achieve the definition. • We show that a lower bound on the size of the broadcast message, previously derived, does not hold. • We propose a new definition of self-healing key distribution, and we show that it can be achieved by concrete schemes. • We give some lower bounds on the resources required for implementing such schemes, i.e., user memory storage and communication complexity. We prove that the bounds are tight. [ABSTRACT FROM AUTHOR]

OFDM has been applied in a wide variety of wireless communications in recent years since it has the advantage over the conventional single-carrier modulation schemes when enduring the frequency-selective fading. However, intercarrier-interference (ICI) and interblock interference (IBI) due to the Doppler effect, carrier frequency drift of local oscillators and multipath fading limit the capability of OFDM systems. In this paper, a new generalized mathematical model for intercarrier and interblock interferences is derived for wireless mobile OFDM systems, in which Doppler frequency drift, local carrier frequency offset, multipath fading, and cyclic prefix coding are all present in reality. Such a new ICI/IBI model can be applied for OFDM performance evaluation in different environments. This new formulation of IBI and ICI provides a generalized framework which includes special ICI models appearing in the previous literature. Besides, the derived OFDM performance evaluation analysis in this paper can greatly benefit OFDM designers for wireless multimedia networks and digital video broadcasting technologies. [ABSTRACT FROM AUTHOR]

The wireless medium offers many opportunities for broadcast communications. However, it also opens the possibility for attackers to eavesdrop the broadcast data or to pretend to be another node or device. These two attacks define the protection goals, namely, confidentiality and authenticity. Traditionally, both are solved by cryptographic approaches exploiting knowledge available in the surrounding infrastructure. The novel communication paradigms for the Internet of Things or cyber–physical systems do not scale with the standard cryptographic approach. Instead it is possible to exploit properties of the underlying physical channel to provide countermeasures against eavesdropping and impersonation attacks. Thereby, the random fading channel induces uncertainty which is detrimental but at the same time also helpful. In this paper, we review and describe a generalized model for physical-layer-based confidential data transmission and wireless authentication. A key role is played by the channel uncertainty and available design dimensions such as time, frequency, and space. We show that wireless authentication and secret-key generation can work in multicarrier and multiple-antenna systems and explain how even outdated channel state information can help to increase the available secure degrees of freedom. This survey focuses on the system design of wireless physical-layer confidentiality and authenticity under channel uncertainty. The insights could lead to a design of practical systems which are preparing the ground for confidentiality and authenticity already on the physical layer of the communication protocol stack. [ABSTRACT FROM AUTHOR]

Today's cyber-physical systems face various impediments to achieving their intended goals, namely, communication uncertainties and faults, relative to the increased integration of networked and wireless devices, hinder the synchronism needed to meet real-time deadlines. Moreover, being critical, these systems are also exposed to significant security threats. This threat combination increases the risk of physical damage. This paper addresses these problems by studying how to build the first real-time Byzantine reliable broadcast protocol (RTBRB) tolerating network uncertainties, faults, and attacks. Previous literature describes either real-time reliable broadcast protocols, or asynchronous (non real-time) Byzantine ones. We first prove that it is impossible to implement RTBRB using traditional distributed computing paradigms, e.g., where the error/failure detection mechanisms of processes are decoupled from the broadcast algorithm itself, even with the help of the most powerful failure detectors. We circumvent this impossibility by proposing RT-ByzCast, an algorithm based on aggregating digital signatures in a sliding time-window and on empowering processes with self-crashing capabilities to mask and bound losses. We show that RT-ByzCast (i) operates in real-time by proving that messages broadcast by correct processes are delivered within a known bounded delay, and (ii) is reliable by demonstrating that correct processes using our algorithm crash themselves with a negligible probability, even with message loss rates as high as 60 percent. [ABSTRACT FROM AUTHOR]

In this paper, we address the problem of how to make the wireless service provider have better profits with consideration of user experience provision in wireless video broadcasting systems. We propose a marginal-based pricing and a resource-allocation framework to achieve better resource utilization and profit improvement. The marginal principle includes 1) marginal user principle, in which a pricing mechanism is established on the basis of marginal users, such that the WSP can seek its own maximum profit of each content with a QoE guarantee; 2) marginal profit principle, in which a WSP can earn the maximum profit through multicontent-service provision by regulating rate allocation in limited available bandwidth. Furthermore, we present a two-tier framework consisting of the inner and outer loops. The inner loop focuses on pricing-based service provision based on the notion of marginal user principle. The outer loop concentrates on allocating bandwidth among multiple video contents according to marginal profit principle. For the solution, we model the profit regions of WSPs and end-users as the polymatroid structures and model the corresponding allocated rate regions as the contra-polymatroid structures. Through exploiting the properties of polymatroid and contra-polymatroid structures, the broadcasting profit problem is solved by finding the optimal rate vector on the sum-rate facet which satisfies the maximal achievable profit. Extensive performance comparison and analysis are presented to demonstrate efficiency of the proposed solution. [ABSTRACT FROM AUTHOR]

In this paper, we consider a dual-hop multiple-input–multiple-output (MIMO) wireless multirelay network, in which a source–destination pair, both equipped with multiple antennas, communicates through multiple half-duplex amplify-and-forward (AF) relay terminals, which are also with multiple antennas. Since perfect channel-state information (CSI) is difficult to obtain in a practical multirelay network, we consider imperfect CSI for all channels. We focus on maximizing the signal-to-interference-plus-noise ratio (SINR) at the destination. We propose a novel robust linear beamforming at the relays, based on the QR decomposition filter at the destination node, which performs successive interference cancellation (SIC). Using the law of large numbers, we obtain the asymptotic rate in the presence of imperfect CSI, upon which the proposed relay beamforming is optimized. Simulation results show that the asymptotic rate matches with the ergodic rate well. Analysis and simulation results demonstrate that the proposed beamforming outperforms the conventional beamforming schemes for any power of CSI errors and SNR regions. [ABSTRACT FROM PUBLISHER]

Effective data broadcasting is essential in vehicular networks not only for road-safety message dissemination but also to aid routing and cooperative driving applications through periodic beaconing and to spread network initialization advertisements that are mandatory to support infotainment applications. Broadcast data are neither acknowledged nor retransmitted in case of failure, which raises the possibility of frame loss due to channel errors and collisions with multiple simultaneous broadcasts. This paper aims at modeling periodic broadcasting on the control channel of IEEE Std. 802.11p vehicular networks with multichannel architecture. Unlike previous related work, the proposed novel analytical approach accounts for mutual influence among nodes, frequent periodic updates of broadcasted data, standard network advertisement procedures, and 802.11p prioritized channel access with multichannel-related phenomena under various link quality conditions. [ABSTRACT FROM PUBLISHER]

Due to advances in techniques for digital ecosystems and cyber engineering, users can now submit queries to search for inclusive information from different Web objects using mobile handheld devices such as smartphones in many real-life situations. As these mobile devices are not necessarily connected to the Internet all the time, users usually want to be able to get information such as e-mail, news, weather, and Web feed as soon as their mobile devices are connected to the Internet. However, these mobile devices have relatively limited resources. In this paper, we focus on mobile web navigation. Specifically, we use rooted directed trees, which enable users to access valuable information from the highly ranked and relevant Web sites, for answering user-inclusive queries. [ABSTRACT FROM AUTHOR]

Digital ecosystems offer cost-effective digital services that attract and benefit the species within them (i.e., humans, organizations, and computers). As a cornerstone technology for digital information delivery, data broadcast provides a strong backbone for the digital ecosystem infrastructure. Its scalability feature is highly significant for various digital ecosystem applications, including mobile broadcast services. This paper proposes a novel structure and access for mobile data broadcast. The proposed scheme addresses the tradeoff for minimizing query-access and tuning times by specifying a new message structure. Correspondingly, a new access and processing mode for mobile clients is required. We study the effectiveness of the proposed approach in minimizing query-access time while maintaining low tuning time. The results of our experiments are used to make comparisons with existing approaches. The results affirm the effectiveness of our proposed scheme. [ABSTRACT FROM AUTHOR]

A main design issue in a wireless data broadcasting system is to choose between push-based and pull-based logic: The former is used as a low-cost solution, while the latter is preferred when performance is of utmost importance. Therefore, the most significant advantage of a push system is the minimal cost. This fact implies that hardware limitations do exist in the case of push systems. As a consequence, every related proposed algorithm should primarily be cost-effective. This attribute, however, has been overlooked in related research. In this paper, popular broadcast scheduling approaches are tested from an implementation cost aspect, and the results render them only conditionally realizable. Moreover, a new, cost-effective, adaptivity oriented schedule constructor is proposed as a realistic, minimal-cost solution. [ABSTRACT FROM PUBLISHER]

This paper proposes a generalized sequential slotted amplify and forward (GSSAF) strategy for single-antenna wireless cooperative networks. The diversity and multiplexing tradeoff (DMT) is analyzed. Applications to cooperative multiple relay channels, cooperative broadcast channels (CBC) and cooperative multiple access channels are considered and the DMT upper bound is proven to be achievable for each case. Other than proposing the best known near-optimal strategy for CBC, another important contribution is to show that GSSAF can be used as a unified strategy to achieve DMT optimality in wireless cooperative networks with unit multiplexing gains. [ABSTRACT FROM AUTHOR]

Although different broadcasting techniques are widely deployed in wireless networks, there are limited comprehensive analytical frameworks to evaluate the performance of such schemes. In this paper, based on a rigorous theoretical analysis, upper bounds on the network coverage and the total number of transmissions (corresponding to network energy consumption) of flooding and its popular variant probabilistic flooding are derived. The analysis is performed for a static multihop ad hoc wireless network when the network is in saturated condition. To consider a realistic medium-access control (MAC) layer algorithm, successful signal reception is based on the protocol model, and nodes employ carrier-sense multiple access. Based on the concept of marked point process, two different approaches, i.e., hop based and time based, are proposed. In the hop-based approach, an upper bound on network coverage and energy consumption is derived for any serving policy and queuing delay that broadcasted packets experience. This approach can be easily extended to multiple-source scenarios. The time-based approach is appropriate for the case of known service policy and queuing delay, and it predicts the time-domain behavior of the broadcasting schemes, as well as other mentioned parameters. We show that the two bounds are very close to each other. The first approach has less complexity, whereas the second approach provides a tighter bound. As an interesting result, we analytically demonstrate that the disjoint analysis of MAC and network layers provides a much simpler solution, whereas the obtained results are also upper bounds on the network coverage. Simulation results validate our analytical model and demonstrate its tightness for real scenarios. [ABSTRACT FROM PUBLISHER]

A fundamental problem in wireless networks is determining the broadcast capacity, i.e., the maximum data transfer rate from a given node to every other node in a relay network. This paper studies the scaling of the broadcast capacity for a network with a single source and N destinations, of which ƒ (N) are randomly selected to also act as relays. In high-density networks (i.e., the node density goes to infinity; the network area is fixed), it is shown that the broadcast capacity is upper bounded by Θ(log ƒ(N)). Schemes are provided that achieve i) Θ(log ƒ(N)) throughput if the channel fading is spatially continuous; ii) Θ(log log ƒ(N)) throughput if the channel fading is spatially i.i.d.. For extended networks (i.e., the node density is fixed; the network area goes to infinity), the broadcast capacity is upper bounded by Θ(1) under channel models with fading and path-loss exponent α > 2. A multistage cooperative broadcasting scheme, which achieves Θ(1) broadcast rate for the high-density extended networks with pathloss channel model is proposed. These results quantifies the gains obtained due to cooperation compared to multihop noncooperative broadcasting, which has a maximum rate that scales as Θ(1) for high-density and Θ(1/(log ƒ(N))α/2) for extended networks. [ABSTRACT FROM AUTHOR]

Underwater acoustic networks have recently emerged as a new area of research in wireless networking. These networks can support a large number of applications such as environmental and underwater equipment monitoring. In recent years, there has been substantial work on protocol design for these networks with most efforts focusing on MAC and network layer protocols. Despite being a fundamental networking primitive, data broadcasting has so far received little attention in the context of underwater networks. This paper proposes an adaptive push system for dissemination of data in underwater acoustic wireless networks. Besides achieving adaptation of its broadcast schedule according to the a priori unknown needs of the clients, the proposed system also efficiently combats the problem of high latency of the underwater acoustic wireless environment. Simulation results show superior performance of the proposed system in the underwater environment compared to adaptations of existing terrestrial push systems. [ABSTRACT FROM AUTHOR]

Using directional antennas to conserve bandwidth and energy consumption in ad hoc wireless networks has attracted much attention from the research community in recent years. However, very little research has focused on applying directional antennas to broadcasting. In this paper, we propose a virtual link reduction (VLR)-based broadcasting protocol for ad hoc wireless networks using directional antennas. Based on two-hop neighborhood information, VLR relies on no location nor angle-of-arrival (AOA) information. VLR is a localized or distributed protocol, and it achieves full delivery. VLR operates on top of any existing broadcast routing protocols. In VLR, no node rebroadcasts a given packet more than once. No physical link is actually reduced, but if a packet has already been forwarded to the end node of the current link, the packet is no longer forwarded, that is, this link is virtually reduced. To evaluate the performance of the proposed VLR-based protocol, we conduct extensive simulation, for simplicity, assuming that there is no packet collision, no channel contention, and no mobility. Simulation results show that VLR outperforms most existing omnidirectional and directional broadcasting schemes in the sense that its normalized transmission cost and redundancy are significantly reduced. Based on the results, we conclude that VLR is more bandwidth and energy efficient. [ABSTRACT FROM AUTHOR]

In wireless mobile computing environments, broadcasting is an effective and scalable technique to disseminate information to a massive number of clients, wherein the energy usage and latency are considered major concerns. This paper presents an indexing scheme for the energy- and latency-efficient processing of full-text searches over the wireless broadcast data stream. Although a lot of access methods and index structures have been proposed in the past for full-text searches, all of them are targeted for data in disk storage, not wireless broadcast channels. For full-text searches on a wireless broadcast stream, we firstly introduce a naive, inverted list-style indexing method, where inverted lists are placed in front of the data on the wireless channel. In order to reduce the latency overhead, we propose a two-level indexing method which adds another level of index structure to the basic inverted list-style index. In addition, we propose a replication strategy of the index list and index tree to further improve the latency performance. We analyze the performance of the proposed indexing scheme with respect to the latency and energy usage measures, and show the optimality of index replication. The correctness of the analysis is demonstrated through simulation experiments, and the effectiveness of the proposed scheme is shown by implementing a real wireless information delivery system. [ABSTRACT FROM AUTHOR]

The role of the push-based architecture in modern wireless telecommunication systems has been gaining momentum over the past few years. However, these systems pose a challenging problem: the creation of the optimal common broadcast schedule that best fits the needs of the totality of the available clients. To this end, various approaches have been proposed, with one of the most well known and widely accepted approaches being the Broadcast Disks method. This method ensures the periodicity and proportionality attributes of the broadcast schedule but leaves ample room for performance optimization, which is a task traditionally assigned to heuristic algorithms. This paper presents a mathematical analysis of the Broadcast Disks method, which establishes a new analytical performance-optimization procedure. Comparison with other related well-known algorithms yielded better performance in every client test case. Finally, the analysis showed that even small deviations from optimal parameter values may lead to significant performance degradation in terms of the clients' mean waiting time. [ABSTRACT FROM AUTHOR]

Data broadcasting is an efficient way of delivering information over asymmetric wireless environments, and push systems can provide high scalability and client hardware simplicity. Many environments, however, are characterized by a priori unknown client demands and groups of clients that are located at the same region and have similar demands. The main disadvantage of the approaches in such cases is the lack of fairness, because groups with few members have much lower performance than groups with many clients, because the performance per group (directly) depends on the group size. In this paper, we propose a fair push system where the performance of each client is independent of the total number of clients that are located in the same region. This condition is achieved without the overall performance of the system being significantly affected. Moreover, the proposed fair system is extended to a priority-based system that multiplies the performance of a specific group, depending exclusively on its priority level in relevance to the rest of the groups. [ABSTRACT FROM AUTHOR]

Broadcast authentication is a critical security service in wireless sensor networks (WSNs), as it allows mobile users of WSNs to broadcast messages to multiple sensor nodes in a secure way. Although symmetric-key-based solutions such as μTESLA and multilevel μTESLA have been proposed, they all suffer from severe energy-depletion attacks resulting from the nature of delayed message authentication. This paper presents several efficient public-key-based schemes to achieve immediate broadcast authentication and thus avoid the security vulnerability that is intrinsic to μTESLA-like schemes. Our schemes are built upon the unique integration of several cryptographic techniques, including the Bloom filter, the partial message-recovery signature scheme, and the Merkle hash tree. We prove the effectiveness and efficiency of the proposed schemes by a comprehensive quantitative analysis of their energy consumption in both computation and communication. [ABSTRACT FROM AUTHOR]

Digital Video Broadcasting for Handheld (DVB-H) is one of the wireless technologies that provide modern digital television services. The main objective of this paper is to propose a method to evaluate the performance of mobile rebroadcaster in terms of symbol error rate, taking into account antenna effects and the Angle of Arrival statistics. A correction factor is derived from concepts as the Mean Effective Gain, which joined to a closed-form expression for the symbol error probability, allows predictions about the antenna impact on the broadcaster. The quantitative evaluation of the analysis identifies an important SNR reduction from 4 dB to 10 dB, depending on the environment. [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]

With the increasing popularity of wireless networks and mobile computing, data broadcasting has emerged as an efficient way of delivering data to mobile clients having a high degree of commonality in their demand patterns. This paper proposes an adaptive wireless push system that operates efficiently in environments characterized by high broadcasting speeds and a-priori unknown client demands for data items. The proposed system adapts to the demand pattern of the client population in order to reflect the overall popularity of each data item. We propose a method for feedback collection by the server so that the client population can enjoy a performance increase in proportion to the broadcasting speed used by the server. Simulation results are presented which reveal satisfactory performance in environments with a-priori unknown client demands and under various high broadcasting speeds. [ABSTRACT FROM AUTHOR]

The MobileTV, IPTV, and DVB standards (DVB-HIT) have been defined to offer mobile users interactive multimedia services with quality of service (Q0S) consistency analogous to TV services. However, the market has yet to provide effective and economical solutions for the real-time delivery of such services to the corresponding transmitters over multi-domain IP networks. The monitoring system proposed in this paper enables the Q0S in the IP networks involved in the delivery of real-time multimedia content to the transmitters to be ascertained. The system utilizes the Q0S parameters defined in MPEG-2 Transport Streams to detect problems occurring in the heterogeneous multi-domain IP networks. The ability to detect problems having an adverse effect on Q0S allows appropriate control actions to be determined to recover the QoS across the composite IP network. The design and implementation of the proposed QoS-Monitoring system (QoS-MS) is presented, followed by analysis of experimental results that demonstrate the feasibility of the system. [ABSTRACT FROM AUTHOR]

Driven by applications in data-hiding, MIMO broadcast channel coding, precoding for interference cancellation, and transmitter cooperation in wireless networks, Costa coding has lately become a very active research area. In this paper, we first offer code design guidelines in terms of source-channel coding for algebraic binning. We then address practical code design based on nested lattice codes and propose nested turbo codes using turbo-like trellis-coded quantization (TCQ) for source coding and turbo trellis-coded modulation (TTCM) for channel coding. Compared to TCQ, turbo-like TCQ offers structural similarity between the source and channel coding components, leading to more efficient nesting with TTCM and better source coding performance. Due to the difference in effective dimensionality between turbo-like TCQ and TTCM, there is a performance tradeoff between these two components when they are nested together, meaning that the performance of turbo-like TCQ worsens as the TTCM code becomes stronger and vice versa. Optimization of this performance tradeoff leads to our code design that outperforms existing TCQ/TCM and TCQ/TTCM constructions and exhibits a gap of 0.94, 1.42 and 2.65 dB to the Costa capacity at 2.0, 1.0, and 0.5 bits/sample, respectively. [ABSTRACT FROM AUTHOR]

Data broadcasting is an efficient way of delivering data to mobile clients having a high degree of commonality in their demand patterns. This paper proposes the use of multiple directional antennas to increase the performance of an adaptive wireless push system in environments that are characterized by the locality of client demands. Simulation results reveal that using up to three antennas suffices for a significant performance increase over the single-antenna adaptive wireless push system. [ABSTRACT FROM AUTHOR]

In this paper, we develop optimization techniques for linear zero-forcing (ZF) multiple-input, multiple-output (MIMO) broadcast (BC) precoders. A computationally efficient technique based on QR-update algorithms for implementing this optimization is then proposed. The application of the proposed ZF precoders and decoders to systems with both large and small numbers of users is considered. The proposed optimization technique is also shown to perform very well in conjunction with nonlinear Tomlinson- Harashima precoding. Both coded and uncoded performances are considered. [ABSTRACT FROM AUTHOR]

Indexing provides for selective tuning but suffers from the drawback that, in order to conserve battery power, the client has to wait for and tune to the index segment. In Location-Aware Mobile Services (LAMSs), it is important to reduce the query response time since a late query response may contain out-of-date information. In this paper, we present a broadcast-based spatial query processing scheme designed to support Nearest Neighbor (NN) query processing. With the proposed schemes, broadcast data items are sorted sequentially based on their locations and the clients can selectively tune to the desired data item without the need for an index segment. For the purpose of selective tuning, we present the Exponential Sequence Scheme (ESS) and Cluster-Based Fibonacci Sequence Scheme (CFS) schemes. The ESS and CFS schemes attempt to conserve battery power. The performance of our schemes is investigated in relation to various environmental variables such as the distributions of data objects, the average speed of the clients, and the size of the service area. The resulting latency and tuning time are close to the optimum values, as our analysis and simulation results indicate. [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplexing (OFDM) systems are highly sensitive to carrier frequency offset and symbol timing error. This paper deals with estimation method of integer frequency offset (IFO) without the aid of pilot symbols. The proposed IFO estimator exploits two consecutive identical OFDM data symbols with only change of phase. In order to improve the accuracy of the IFO estimator, receive diversity is adopted. To demonstrate the efficiency of the proposed IFO estimators, comparisons are made with other existing estimators in terms of error performance, estimation range, and complexity. [ABSTRACT FROM AUTHOR]

This paper presents an up to date study on external noise levels in the medium wave band based on field trials carried out in Spain and Mexico during years 2004 and 2005 respectively. External noise levels predicted by the ITU-R P.372 recommendation are based on measurements carried out more than 30 years ago and no updated results for the medium wave band have been published in this time. An increment on these noise levels have been measured, which leads to a significant impact on the minimum usable field strength requirements for the broadcasting systems used in this frequency band, such as the new Digital Radio Mondiale (DRM) and In-Band/On-Channel (IBOC) systems. [ABSTRACT FROM AUTHOR]

In this paper, we propose a differential space-frequency block code—orthogonal frequency division multiplexing (DSFBC-OFDM) scheme as a multiple-input multiple-output (MIMO) transmission technique for next generation broadcasting system. A linear decoding method for DSFBC, which performs comparably to the ML decoding method, is derived for the cases of two or four transmit antennas. A simple table lookup method is proposed to improve the efficiency of the encoding/decoding process of DSFBC for the case of non-constant modulus constellations. This not only reduces the computational load, but also removes the necessity of channel estimation. Also, synchronization techniques with a DSFBC-encoded phase reference symbol (PRS) are discussed. Finally, an MIMO channel model for the next generation broadcasting system is developed by extending the 3GPP MIMO model to fit broadcasting environments. The MIMO channel model is then used to compare BER performances of differential space block code schemes for various channel environments. Simulation results show that the DSFBC-16QAM scheme using either four transmit antennas with one receive antenna or two transmit antennas with two receive antennas achieves a performance gain of 12 dB, with a data rate twice faster than that of the conventional DQPSK scheme. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a new scheme to improve the performance of the terrestrial - digital multimedia broadcasting (T-DMB) system, which exploits the burst error characteristics at the output of the convolutional decoder and the properties of the Reed-Solomon (RS) decoder to correct more errors by predicting erasures in each RS packet in advance as many as possible before decoding in the RS decoder. Simulation results show that the proposed scheme yields performance gain of around 1 dB at BER of 10-8 which can result in the extended coverage area of the T-DMB system. [ABSTRACT FROM AUTHOR]