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The problem of disseminating continuous data flow from a given source node to all other network nodes is known as the dynamic broadcast problem, which is also a fundamental problem in multi-hop wireless networks (e.g., wireless ad hoc and sensor networks). Due to link unreliability and node mobility, the topology of a network typically changes with time. Little work has been conducted to address the dynamic broadcast problem in time-varying wireless multi-hop networks, especially under the popular Signal-to-Interference-plus-Noise-Ratio (SINR) interference model. In this paper, we study the dynamic broadcast problem in SINR-based time-varying directed acyclic multi-hop wireless networks formed by point-to-point wireless links. We consider the SINR-based link transmission rate model involved in the slot-based link scheduling. We first prove a tight upper bound for the broadcast capacity of the multi-hop wireless networks under study. We then propose an online max-weight Throughput-Optimal Dynamic Broadcast algorithm (TODB) which performs link weight allocation, link scheduling, and data forwarding for each time slot according to the current network connectivity and data reception rates of nodes. We derive the throughput-optimality of the TODB algorithm by proving that the broadcast throughput of TODB can achieve the aforementioned upper bound of the broadcast capacity. We evaluate the performance of TODB in terms of throughput and latency via simulations and the results validate its effectiveness. [ABSTRACT FROM AUTHOR]

This paper investigates secure broadcast communications in intelligent reflecting surface (IRS)-aided millimeter wave (mmWave) symbiotic radio (SR) networks, where the IRS and the base station (BS) are cooperating. Specifically, the IRS assists secure broadcasting for the BS by smartly reconfiguring the phase shifts of the signals from the BS, while delivering its own information to an Internet-of-Things device (IoD). We aim at maximizing the minimum secrecy rate of multiple users by jointly designing the hybrid precoder at the BS and the passive beamformer at the IRS, subject to the rate constraints of both the multiple users and the IoD. The design is formulated as a non-convex optimization problem, which is intractable. To handle it, we develop a computationally efficient iterative algorithm based on the successive convex approximation, the efficiency and superiority of which have been validated by simulation results. [ABSTRACT FROM AUTHOR]

This paper presents an adaptive broadcast interval for data dissemination for an infrastructure-to-vehicle (I2V) environment. The roadside units (RSUs) disseminate the data to the vehicles after a specified broadcast time interval. Time interval tuning for the data dissemination is one of the parameters used to determine the effectiveness of the broadcast time interval at RSU for safety and infotainment message dissemination to the vehicles under a particular RSU coverage. We formulated the problem of computing an optimal broadcast time interval to maximize the service ratio, reducing the duplicate message overhead. The proposed scheme uses the software-defined network (SDN) architecture having OpenFlow-enabled RSUs and SDN controllers. Based on the global view of traffic-related information, the proposed SDN controller computes the broadcast time interval for data dissemination among the vehicles. We used the NS-3 simulator to evaluate the proposed scheme's performance by generating a real scenario of VANET traffic using SUMO. Simulation results show that the proposed SDN-based scheme increases the average service ratio by 15-20% and reduces duplicate message overhead by 7-10% in comparison to the other existing state-of-the-art schemes. [ABSTRACT FROM AUTHOR]

Beacon broadcasting is of great importance in improving road safety and avoiding dangerous situations in vehicular ad hoc networks (VANETs). In order to support emerging vehicular applications such as autonomous driving, the reliability of beacon broadcasting becomes an indispensable issue which is also difficult given the highly dynamic topology and vehicle density. For the territories which are not covered with communication infrastructure, controlling and scheduling in a centralized way may not be applicable. Therefore, vehicle-to-vehicle (V2V) ad hoc communication is promising to address the ubiquitousness coverage concern. In this paper, a distributed network coding-based medium access control protocol (NC–MAC) is proposed to support V2V beacon broadcasting. We combine the preamble-based feedback mechanism, retransmissions, and network coding together to enhance broadcasting reliability. Extensive simulations are given to show the performance gain of NC–MAC protocol compared to the existing 5 G cellular vehicle-to-everything (C–V2X) MAC protocol in a wide range of scenarios including highway and urban vehicle traces generated by simulation of urban mobility (SUMO). The results show that the proposed protocol can improve the communication reliability as well as scalability. [ABSTRACT FROM AUTHOR]

Efficiency of position-based emergency message broadcast protocols of Vehicular Ad-hoc Networks (VANET) is affected by the position of vehicles that depends entirely on accuracy of the positioning system. In addition, GPS-based dissemination protocols encounter many challenges due to high-energy consumption, low accuracy, and the need for up-to-date maps for real-world automatic applications. In this paper, a Route Segmented Broadcast Protocol based on Radio Frequency identification technology (RSBP-RF) is proposed to eliminate GPS-based problems and increase the efficiency of emergency message broadcasting by improving the positioning accuracy. In this protocol, embedded passive RFID tags are used to segment the route and provide a position-aware technique. In RSBP-RF, each vehicle is informed of its position by crossing on the tags and immediately broadcasts a beacon to its neighbors. Moreover, the proposed protocol includes a proactive relay vehicle selection scheme that uses the received beacons to select the farthest neighboring node. The results of the conducted simulations in the NS-3 tool have validated the effectiveness of the proposed protocol in terms of end-to-end delay, delivery ratio, one-hop delay, collision ratio, relay node selection accuracy, and dissemination performance. Moreover, analysis of the time complexity and message complexity proves the lightness of the RSBP-RF protocol. [ABSTRACT FROM AUTHOR]

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 proposes the integration of non-orthogonal multiple access (NOMA) and broadcasting with buffer-aided (BA) full-duplex (FD) relaying to improve the spectral efficiency of a single-source two-user network. Furthermore, opportunistic relay selection is employed, activating one or two FD relays to support the end-to-end communication. The network performance is improved through buffers, allowing to switch to half-duplex (HD) transmission/reception when FD operation is not feasible. A hybrid BA FD/HD NOMA relay selection algorithm is proposed, herein called $\mathop {\mathrm{BAHyNOMA}}$ , orchestrating the three aforementioned techniques, towards a simple yet efficient and robust relay selection. $\mathop {\mathrm{BAHyNOMA}}$ is evaluated in terms of outage probability, average sum-rate and average delay, and it is observed that the average sum-rate can be doubled, while maintaining low latency. [ABSTRACT FROM AUTHOR]

Multimedia broadcast and multicast services (MBMS) in mobile networks has been widely addressed, however an investigation of such a technology in emerging, multi-tier, scenarios is still lacking. Notably, user clustering and resource allocation are extremely challenging in multi-tier networks, and imperative to maximize system capacity and improve quality of user-experience (QoE) in MBMS. Thus, in this paper we propose a clustering and resource allocation approach, named EMB, which specifically addresses heterogeneous networks and accounts for the fact that multimedia content is adaptively encoded into scalable layers depending on the QoE requirements and channel conditions of the heterogeneous users. Importantly, we prove that our clustering algorithm yields Pareto efficient broadcasting areas, multimedia encoding parameters, and resource allocation, in a way that is also fair to the users. Furthermore, numerical results obtained under realistic conditions and using real-world video content, show that the proposed EMB results in lower churn count (i.e., higher number of served users), higher throughput, and increased QoE, while using fewer network resources. [ABSTRACT FROM AUTHOR]

An autonomous V2V communication mode (also known as side-link mode 4), which facilitates V2V communication in out of eNB coverage areas, has recently been introduced into the Long term evolution (LTE) standard. Recent research has studied the performance of this LTE-V2V autonomous mode for a highway use case. However, performance analysis for a highway use case cannot be easily applied to an intersection use case as it may contain non-line-of-sight (NLOS) communication links. In this paper, we analyze and evaluate the safety message broadcasting performance of LTE-V2V autonomous mode in an urban intersection scenario. Considering practical path loss models, we present the impact of NLOS communication link on the overall message dissemination performance. Through the analytical and simulation results, we show that the overall message dissemination performance degrades drastically with increasing vehicle density and increasing distance of the transmitting vehicle from the intersection. To improve the performance, we propose a vehicle-assisted relaying scheme in which the relaying vehicle is selected in an autonomous manner. We also present two resource allocation strategies for the relaying vehicle. For low to medium vehicle density along the street, we observe significant improvement in message dissemination through relaying compared to the scheme without relaying. [ABSTRACT FROM AUTHOR]

In this paper, we study the problem of multirate packet delivery in heterogeneous packet erasure broadcast networks. The technical challenge is to enable users receive packets at different rates, as dictated by the quality of their individual channel. We present a new analytical framework for characterizing the delivery rate and delivery delay performance of a previously proposed non-block-based network coding scheme in the literature. This scheme was studied in homogeneous network settings. We show for the first time, via new theoretical analysis and simulations that it can actually achieve multirate packet delivery. Using acknowledgments from each user, we show that the user with the highest link capacity achieves the maximum possible throughput. Also, a non-zero packet delivery rate is possible for other users, and the delivery rate depends on the difference between the packet arrival rate at the sender and the link capacity of each user. The accuracy of our analytical framework is confirmed by comparing the results with simulations for different settings of packet arrival rate at the sender and link capacities. [ABSTRACT FROM AUTHOR]

One approach to the distribution of traffic information in a self-organizing traffic information system is multihop broadcasting. In this approach, each vehicle may simply rebroadcast an information packet that it receives from the others. However, rebroadcasting results in redundant retransmissions of the same information, leading to a useless occupation of the radio channel. Minimizing redundancy, while still guaranteeing reachability in the network, is a challenging task in multihop broadcasting. In our previous work, we introduced a new probabilistic-based broadcasting scheme, i.e., Irresponsible Forwarding (IF) , which could effectively reduce the redundancy. However, in the previous work, we only considered the scenario where the intervehicle spacing was exponentially distributed. In this paper, we generalize the concept of IF such that it can be applied to any intervehicle spacing distribution. In addition, we evaluate the performance of the IF protocol when it is applied in a realistic scenario (i.e., using real traffic traces). This paper shows that the IF protocol is able to limit packet redundancy all hours of the day effectively. [ABSTRACT FROM PUBLISHER]

This paper contributes to the studies for long-term evolution (LTE) deployment into the ultrahigh-frequency (UHF) broadcasting spectrum (470–790 MHz) utilizing the supplemental downlink (SDL) concept and its coexistence with the digital terrestrial Television (DTT) service. The performed real and practical coexistence scenario studies were based on the modeling and simulation of the LTE and DTT systems in order to assess potential interference between systems and the availability of the spectrum for the LTE SDL services. Simulations were aligned with the scenarios and assumptions agreed to in the European regulation complemented with real case study parameters from Finland: the early adopter of the digital dividend II. The results lead to some conclusions about the LTE SDL-DTT coexistence and indicated availability of the complementary LTE SDL services on the lower UHF spectrum. Flexible use of the UHF band aims to increase the efficiency of spectrum use in delivering fast growing and converging mobile broadband, media, and TV content to meet the changing consumer needs. Simulated scenarios can be utilized by regulation and standardization forums for studying the future of UHF spectrum and LTE broadcasting evolution in mobile communications toward fifth-generation (5G). [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]

There are numerous research challenges that need to be addressed until a wide deployment of vehicular ad hoc networks (VANETs) becomes possible. One of the critical issues consists of the design of scalable routing algorithms that are robust to frequent path disruptions caused by vehicles' mobility. This paper argues the use of information on vehicles' movement information (e.g., position, direction, speed, and digital mapping of roads) to predict a possible link-breakage event prior to its occurrence. Vehicles are grouped according to their velocity vectors. This kind of grouping ensures that vehicles, belonging to the same group, are more likely to establish stable single and multihop paths as they are moving together. Setting up routes that involve only vehicles from the same group guarantees a high level of stable communication in VANETs. The scheme presented in this paper also reduces the overall traffic in highly mobile VANET networks. The frequency of flood requests is reduced by elongating the link duration of the selected paths. To prevent broadcast storms that may be intrigued during path discovery operation, another scheme is also introduced. The basic concept behind the proposed scheme is to broadcast only specific and well-defined packets, referred to as "best packets" in this paper. The performance of the scheme is evaluated through computer simulations. Simulation results indicate the benefits of the proposed routing strategy in terms of increasing link duration, reducing the number of link-breakage events and increasing the end-to-end throughput. [ABSTRACT FROM AUTHOR]

Based on the cell broadcast service architecture, this paper proposes an efficient multicast mechanism for the universal mobile telecommunications system to support multimedia messaging service (MMS). We define a new interface between the serving GPRS support node and the cell broadcast center to track the current locations of the multicast members. Then we describe the location tracking procedures (including, attach, detach, and location update) of the multicast members and the multicast message delivery procedure. We use an analytic model to investigate the performance of our approach. This paper indicates that our MMS multicast mechanism outperforms the previous proposed approaches. [ABSTRACT FROM AUTHOR]

Wireless broadcasting systems employ multiple retransmissions to guarantee the correct reception of each packet. The traditional hybrid automatic retransmission request (HARQ) protocol retransmits one packet per slot. Hence, a large amount of retransmissions is required to correctly receive all the packets, which leads to low spectrum efficiency. In this paper, we propose a Network-coding-and-distributed-Turbo-Coding-based type-III HARQ (NTC-HARQ) protocol, including an xoring Network Coding Combined (XNCC) retransmission strategy at the access node (AN) and a joint network–turbo decoding (JNTD) strategy at the user equipment (UE). Specifically, to reduce the overall number of retransmissions, lost packets of different UEs are network coding (NC) combined at the AN by utilizing the XNCC strategy. The soft information of the lost packet at each UE can be recovered from the received network-coded retransmission packet by using the proposed xoring soft network decoder. The recovered soft information of the UE's lost packet is combined with the local undecodable soft information of the same packet to form a distributed turbo code. A Chase-combining-based distributed turbo decoder is proposed to perform turbo decoding, which introduces coding gain and improves packet-error-rate (PER) performance. Theoretical analyses and simulation results show that the average-number-of-transmission performance of the proposed NTC-HARQ protocol outperforms that of the XNCC-based type-I HARQ protocol, the traditional NC-based HARQ protocol, and the JNTD-based protocol. [ABSTRACT FROM PUBLISHER]

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]

In this paper, we propose a novel best-effort broadcasting service (BEBS) scheme in cellular networks, which can be used for location-based advertising and real-time multimedia broadcasting. Unlike the conventional broadcasting service that aims to assure reliable data delivery to every user, the main objective of the proposed BEBS is to maximize the effective capacity at the cost of reliability. To this end, we introduce the notion of target reliability and formulate the problem of maximizing the capacity of BEBS under any given reliability constraint. By deriving an analytical model, we investigate the effect of target reliability on the achievable capacity. We further prove several key properties of BEBS with respect to the optimal value of target reliability and the maximum gain of the achievable capacity. To realize the maximum achievable capacity of BEBS, we propose two feedback control schemes that adjust the target reliability or modulation and coding scheme based on the estimate of relative gain of BEBS. We validate our analytical model by comparison with simulation. In addition, the simulation results confirm that the proposed schemes for BEBS significantly outperform conventional reliable broadcasting under various network configurations. [ABSTRACT FROM PUBLISHER]

Recently, many cities around the world have witnessed large-scale deployment of terrestrial broadcasting mobile television (TV) to vehicles. This service is similar to the cable or satellite TV already in the home, and user-centric interactive mobile Video-on-Demand (VoD) over urban vehicular networks is in fact expected. However, providing this new service with focus on user Quality of Experience (QoE) constitutes a significant challenge. This paper introduces a QoE-driven User-centric solution for VoD services in urban vehicular network environments (QUVoD). QUVoD relies on a multihomed hierarchical peer-to-peer (P2P) and vehicular ad-hoc network (VANET) architecture. Vehicles construct a low-layer VANET via Wireless Access in the Vehicular Environment interfaces; they also form an upper layer P2P Chord overlay on top of a cellular network via Fourth-Generation (4G) interfaces. A novel grouping-based storage strategy that uniformly distributes the video segments along the Chord overlay is proposed, reducing segment seeking traffic while also enabling load balancing. A novel segment seeking and multipath delivery scheme that achieves high lookup success rate and very good video data delivery efficiency is also introduced, which achieves high lookup success rate and very good video data delivery efficiency. Furthermore, a new speculation-based prefetching strategy is proposed, which analyses users' interactive viewing behavior and, by estimating video segment playback order, employs prefetching of the expected segments, smoothening the video playback. Simulation results show how QUVoD is a highly efficient user-centric mobile VoD solution in urban vehicular networks in comparison with existing state-of-the-art solutions. [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]

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]

Although Digital Video Broadcast-Handheld (DVB-H) is currently considered to be a mature technology, new multiburst forward error-correction (FEC) schemes such as multiprotocol encapsulation–interburst FEC (MPE-iFEC) and application-layer FEC (AL-FEC) can be applied to mobile TV streaming services to increase the robustness of the transmission. Compared with the conventional intraburst approach MPE-FEC, multiburst encoding provides protection across several bursts rather than within a single burst because it is possible to recover from completely erroneous bursts. The robustness of the transmission can be enhanced, keeping the capacity devoted for error repair (code rate or FEC overhead) and thus increasing the number of interleaved bursts. This paper describes a methodology for estimating the coverage for multiburst FEC DVB-H mobile TV streaming services in realistic scenarios based on dynamic system-level simulations. Furthermore, it presents illustrative performance-evaluation results with field measurements, and it presents simulation results quantifying the reduction in the fading margin required to cope with fast fading and shadowing that can be achieved with multiburst FEC, compared with MPE-FEC. [ABSTRACT FROM PUBLISHER]

Broadcast transmission is an effective way to disseminate safety-related information for cooperative driving in intervehicle communication (IVC). However, it is fraught with fundamental challenges such as message redundancy, link unreliability, hidden terminals, and broadcast storms, which greatly degrade network performance. In this paper, we introduce a cross-layer approach to design an efficient and reliable broadcast protocol for emergency message dissemination in IVC systems. We first propose a novel composite relaying metric for relay selection by jointly considering geographical locations, physical-layer channel conditions, and moving velocities of vehicles. Based on the relaying metric, a distributed relay-selection scheme is proposed to assure that a unique relay is selected to reliably forward the emergency message in the desired propagation direction. We further apply IEEE 802.11e enhanced distributed coordination access (EDCA) medium-access control (MAC) to guarantee quality-of-service (QoS) provisioning to safety-related services. In addition, an analytical model is developed to study the performance of the proposed cross-layer broadcast protocol (CLBP) in terms of the relay-selection delay and the emergency message access delay. Network Simulator (NS-2) simulation results are given to validate our analysis. It is shown that the CLBP not only can minimize the broadcast message redundancy but can quickly and reliably deliver emergency messages in IVC as well. [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]

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]

Broadcast is a fundamental operation of wireless ad hoc networks (WANETs) and has widely been studied over the past few decades. However, most existing broadcasting strategies assume nonsleeping wireless nodes and thus are not suitable for uncoordinated duty-cycled WANETs, in which each node periodically switches on and off to save energy. In this paper, we study the minimum-transmission broadcast problem in uncoordinated duty-cycled WANETs (MTB-UD problem) and prove its NP-hardness. We show that modifications of existing broadcast approaches can only provide a linear approximation ratio of O(n) (where n is the number of nodes in the network). We propose a novel set-cover-based approximation (SCA) scheme with both centralized and distributed approximation algorithms. The centralized SCA (CSCA) algorithm has a logarithmic approximation ratio of 3(ln Δ + 1) and time complexity of O(n3) (Δ is the maximum degree of the network). The distributed SCA (DSCA) algorithm has a constant approximation ratio of at most 20 while keeping both linear time and message complexities. We have conducted both theoretical analysis and simulations to evaluate the performance of the proposed algorithms. Results show that both the CSCA and DSCA algorithms outperform the modified versions of existing broadcast approaches by at least 50%. [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]

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]

Digital Video Broadcasting via Satellite-Second Generation (DVB-S2) was originally designed for fixed terminals, but it has recently been adopted by the DVB Return Channel via Satellite for Mobile scenario (DVB-RCS+M) under the singlecarrier-per-channel (SCPC) mode. For the purpose of adapting DVB-S2 for mobile reception, it has been agreed that, among others, forward error correction (FEC) at the link layer (LL) is a suitable means of achieving reliable reception in mobile environments. Prime candidates for LL-FEC had already been available schemes in the DVB family of standards: multiple-protocol encapsulation-FEC (MPE-FEC) and MPE interburst FEC (MPE-IFEC). Furthermore, different FEC codes may be applied within these schemes, i.e., Reed-Solomon (RS) or Raptor FEC codes. This paper introduces the integration of such schemes and codes on top of DVB-S2. In addition, we analyze the performance that can be achieved when applying these schemes with particular focus on two typical railway scenarios: 1) line of sight, together with the effect of railway power arches (LOS+PA), and 2) nonline of sight (nLOS). Both theoretical and simulation analyses reveal that LL-FEC can overcome typical fading effects in the railway scenario by selecting appropriate FEC codes and optimizing the coding parameters. We show that MPE-IFEC and extended MPE-FEC with Raptor codes - as finally specified in DVB-RCS+M-consistently show superior results over those of other LL-FEC for railway scenarios. We also indicate signaling updates to allow achievable performance. As for practical implementation, we propose two possible novel cross-layer architectures for unicast DVB-52 to provide quality of service (QoS). The architectures allow the migration from traditional packet encapsulation based on Moving Picture Experts Group 2-Transport Streams (MPEG2-TS) to new schemes, such as generic stream encapsulation (GSE). [ABSTRACT FROM AUTHOR]

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]

Digital video broadcasting for handhelds (DVB-H) is the standard for broadcasting Internet Protocol (IP) data services to mobile portable devices. To provide interactive services for DVB-H, the Universal Mobile Telecommunications System (UMTS) can be used as a terrestrial interaction channel for the unidirectional DVB-H network. The converged DVB-H and UMTS network can be used to address the congestion problems due to the limited multimedia channel accesses of the UMTS network. In the converged network, intersystem soft handover between DVB-H and UMTS is needed for an optimum radio resource allocation, which reduces network operation cost while providing the required quality of service. This paper deals with the intersystem soft handover between DVB-H and UMTS in such a converged network. The converged network structure is presented. A novel soft handover scheme is proposed and evaluated. After considering the network operation cost, the performance tradeoff between the network quality of service and the network operation cost for the intersystem soft handover in the converged network is modeled using a stochastic tree and analyzed using a numerical simulation. The results show that the proposed algorithm is feasible and has the potential to be used for implementation in the real environment. [ABSTRACT FROM AUTHOR]

The dual-decomposition-based sum capacity maximization algorithm for the vector broadcast channels consists of the following two nested loops: The inner loop is an iterative water-filling-like algorithm that optimizes the covariance matrices for a fixed water level, and the outer loop finds the optimum water level by using a bisection search. Recently, an improved version has been proposed, where the inner loop is optimized only to a certain tolerance that still guarantees algorithm convergence. This requires tracking the instantaneous error of the inner loop, and this issue has not yet been addressed. In this paper, we provide a tight upper bound of the instantaneous error of the inner loop, which can be used to construct a nonheuristic stopping criterion. Specifically, we derive the Lagrange dual function of the inner optimization problem and provide a method to obtain a feasible dual variable from which a tight upper bound of the instantaneous error can easily be computed. We also show that the rate of convergence of the global algorithm can substantially be improved by introducing a covariance normalization step between two successive outer iterations. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a new communications paradigm, namely, reliable neighborcast, and present a reliable neighborcast protocol (RNP) that operates as an overlay on the existing reliable broadcast protocols. The protocol is intended for vehicle-to-vehicle communications networks that communicate the speed, position, and state of nearby vehicles to coordinate or control their operation. The implementation of RNP that we describe operates on top of overlapping groups that use the mobile reliable broadcast protocol and provides the guarantees and characteristics of that protocol to each neighborhood. The efficiency of the overlays—defined as the fraction of the received messages that apply to a neighborhood—widely varies. We present an efficient overlay for 1-D networks, which is implemented in many highway applications. The characteristics of mobility are considered, and techniques are presented to eliminate delays as vehicles change neighborhoods and to move the underlying broadcast groups with the general flow of traffic. [ABSTRACT FROM AUTHOR]

In this paper, we propose a distributed mobility transparent broadcast (DMTB) protocol to achieve efficient and effective broadcasts in vehicle-to-vehicle networks. The protocol is fully distributed and highly adaptive to node mobility. Although distributed, DMTB does not suffer from the performance degradation induced by the unavailability of global information. The protocol's performance is proven to be within a constant of the optimum. A detailed analysis regarding the protocol's performance is presented. The simulation results clearly verify that the protocol maintains its performance under high node mobility. [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]

Flexible multimedia broadcast/multicast services such as mobile auction and advertisements are vital services for future mobile ad hoc networks. A great number of applications rely on a reliable and efficient medium access control (MAC) layer broadcast. The current IEEE 802.11 broadcast protocol based on carrier sense multiple access with collision avoidance does not offer any MAC layer recovery on broadcast frames. Consequently, unexpected lost frames may deteriorate the quality of broadcast/multicast services. Previous protocols extended request-to-send, clear-to-send, and acknowledgement to enhance the broadcast reliability. However, they still suffered from the hid- den terminal problem and the excessive retransmission problem at the same time. In this paper, we first formulate the excessive retransmission problem as an optimization problem and show that it is NP-hard even if the upper layer service is periodical beacon exchange. An approximation algorithm with a guaranteed approximation ratio is also suggested. Then, a reliable and efficient MAC layer broadcast protocol, which is named broadcast protocol with busy tone (BPBT), is proposed. BPBT applies a busy tone to solve the hidden terminal problem and applies the proposed approximation algorithm to solve the excessive retransmission problem. Finally, BPBT is compared with previous protocols for performance evaluation by simulation. [ABSTRACT FROM AUTHOR]

Localization is one of the substantial issues in wireless sensor networks. Several approaches, including range-based and range-free, have been proposed to calculate positions for randomly deployed sensor nodes. With specific hardware, the range-based schemes typically achieve high accuracy based on either node-to- node distances or angles. On the other hand, the range-free mechanisms support coarse positioning accuracy with the less expense. This paper describes a range-free localization scheme using mobile anchor points. Each anchor point equipped with the GPS moves in the sensing field and broadcasts its current position periodically. The sensor nodes obtaining the information are able to compute their locations. With the scheme, no extra hardware or data communication is needed for the sensor nodes. Moreover, obstacles in the sensing fields can be tolerated. The localization mechanism has been implemented in the network simulator ns-2. The simulation results show that our scheme performed better than other range-free mechanisms. [ABSTRACT FROM AUTHOR]

Data dissemination by the use of periodic broadcast is a viable sc bible mechanism due to the explosion of information services in wireless networks. Many research works have exploited the data broadcast methodologies, however, upon the premise that the broadcast traffic is static on a single broadcast channel. In practice, the broadcast traffic changes dynamically and multiple broadcast channels can be utilized for efficient data dissemination. Accordingly, in this paper we devise an adaptive multichannel data dissemination mechanism, including two components: the multichannel traffic-awareness and the deterministic balance search techniques. The multichannel traffic-awareness technique performs a cyclic estimation of dynamic access frequency distribution in response to traffic dynamics. With the measured estimation, he deterministic balance search technique adjusts channel allocation and item classification to further minimize and balance the push access and the pull response time. The experimental results show that the proposed mechanism is able to attain the result of channel partition and item classification very close to the optimum and, thus, minimize the mean access time in both push and pull channels simultaneously. Therefore, the reliability of broadcast contents is guaranteed. [ABSTRACT FROM AUTHOR]