Periodic Broadcast Research Articles

An Adaptive Broadcasting Strategy for Efficient Dynamic Mapping in Vehicular Networks

In this work, we face the issue of achieving an efficient dynamic mapping in vehicular networking scenarios, i.e., obtaining an accurate estimate of the positions and trajectories of connected vehicles in a certain area. State-of-the-art solutions are based on the periodic broadcasting of the position information of the network nodes, with an inter-transmission period set by a congestion control scheme. However, the movements and maneuvers of vehicles can often be erratic, making transmitted data inaccurate or downright misleading. To address this problem, we propose to adopt a dynamic transmission scheme based on the actual positioning error, sending new data when the estimate overcomes a preset error threshold. Furthermore, the proposed method adapts the error threshold to the operational context according to an innovative congestion control algorithm that limits the collision probability among broadcast packet transmissions. This threshold-based strategy can reduce the network load by avoiding the transmission of redundant messages, and is shown to improve the overall positioning accuracy by more than 20% in realistic urban scenarios.

Passive Round-Trip-Time Positioning in Dense IEEE 802.11 Networks

The search for a unique and globally available location solution has attracted researchers for a long time. However, a solution for indoor scenarios, where high accuracy is needed, and Global Positioning System (GPS) is not available, has not been found yet. Despite the number of proposals in the literature, some require too long a calibration time for constructing the fingerprinting map, some rely on the periodic broadcast of positioning information that may downgrade the data communication channel, while others require specific hardware components that are not expected to be carried on commercial off-the-shelf (COTS) wireless devices. The scalability of the location solution is another key parameter for next-generation internet of things (IoT) and 5G scenarios. A passive solution for indoor positioning of WiFi devices is first introduced here, which merges a time-difference of arrival (TDOA) algorithm with the novel fine time measurements (FTM) introduced in IEEE 802.11mc. A proof of concept of the WiFi passive TDOA algorithm is detailed in this paper, together with a thorough discussion on the requirements of the proposed algorithm.

Efficient coverage greedy packet stateless routing in wireless sensor networks

Wireless sensor network is a collection of sensor nodes designed with different routing capabilities to operate on real-world applications. In extreme environments, real-time applications of wireless sensor network ensure exchange of data, a difficult one between the sensor nodes, when less resources are consumed. Therefore, researchers are developing a routing protocol including optimal routing procedures to increase the longevity of the networks. In this paper, an improved route extension architecture is developed in wireless sensor network environment. This Improved Greedy Perimeter Stateless Routing is proposed to offer an improved transmission coverage and reduced power consumption capability. It deploys a periodic broadcast of hello message (or control messages) including the positional information between the sensor nodes. The experimental result concludes that the Improved Greedy Perimeter Stateless Routing method achieves improved routing capabilities than the traditional hybrid protocols like LEACH and Greedy Perimeter Stateless Routing.

Investigating narrative involvement, parasocial interactions, and impulse buying behaviours within a second screen social commerce context

Using mobile devices for additional information search before, during and after watching television (either factual news or fictional TV series) - is an increasingly significant information management phenomenon. This activity has been recognised by both TV media executives and academia as ‘second screen’ activity. This paper develops and tests a ‘parasocial interaction-impulse buying’ - model that captures the behaviours of consumers watching a Chinese TV drama series. These audience-consumers were also engaging extensively (most on a daily basis) during the broadcast period with series related influencer social media activities on a second screen. A structural equation model was developed to analyse the data. Findings indicate that TV series audience consumers who are also highly engaged with influencer- consumer ‘second screen’ content are likely to experience positive narrative involvement leading to engagement in parasocial interaction behaviours and ultimately impulse buying behaviour. These findings have implications for managers by providing insights into (1) the effects of influencer second screen content (2) the processes by which consumers’ involvement in a TV show’s narrative leads to impulse buying of products. Thus, influencer related second screen consumer engagement should be considered a significant opportunity for marketers, as such activity makes consumers become more involved in the characters and the narrative of a particular TV show, leading to increased impulse buying.

Hybrid Combining of Directional Antennas for Periodic Broadcast V2V Communication

A hybrid analog-digital combiner for broadcast vehicular communication is proposed. It has an analog part that does not require any channel state information or feedback from the receiver, and a digital part that uses maximal ratio combining (MRC). We focus on designing the analog part of the combiner to optimize the received signal strength along all azimuth angles for robust periodic vehicle-to-vehicle (V2V) communication, in a scenario of one dominant component between the communicating vehicles (e.g., highway scenario). We show that the parameters of a previously suggested fully analog combiner solves the optimization problem of the analog part of the proposed hybrid combiner. Assuming $L$ directional antennas with uniform angular separation together with the special case of a two-port receiver, we show that it is optimal to combine groups of $\lceil L/2\rceil$ and $\lfloor L/2\rfloor$ antennas in analog domain and feed the output of each group to one digital port. This is shown to be optimal under a sufficient condition on the sidelobes level of the directional antenna. Moreover, we derive a performance bound for the hybrid combiner to guide the choice of antennas needed to meet the reliability requirements of the V2V communication links.

Vehicle density and signal to noise ratio based broadcast backoff algorithm for VANETs

In a realistic vehicular ad-hoc networks (VANETs), a beacon frame loss is usually caused by collision or channel noise. In this paper, we propose an effective scheme for the periodic broadcast on the control channel in VANETs. Instead of the fixed contention window, in our scheme, the contention window is dynamically adjusted. For a certain vehicle density, the best contention window size is obtained by maximizing the transmission success rate in a unit time slot. On this basis, the channel quality is evaluated according to the signal to noise ratio (SNR), and the same frame will be transmitted twice under certain conditions. Simulation results show that the proposed vehicle density and SNR based broadcast algorithm outperforms the traditional broadcast methods.

Performance Analysis and Boost for a MAC Protocol in Vehicular Networks

This paper proposes an analytical model to investigate the performance of periodical broadcast of safety messages in vehicular ad hoc networks (VANETs), regarding a hybrid medium access control (MAC) protocol, called NC-PNC MAC. We first examine the percent of vehicles involved in subcarrier collisions during a random orthogonal frequency-division multiple access scheme, and then theoretically analyze the total number of transmissions and the packet delivery ratio (PDR) during one dissemination period. Based upon the analysis, this paper not only reveals how the subcarrier collision probability influences the PDR performance, but mathematically obtains the maximum PDR. To confirm the results, by adjusting a pivotal parameter of the MAC protocol, the PDR performance for basic safety message broadcast in VANETs can be enhanced by 10% to 30% under the constraint of the delivery latency.

IPBM: an energy efficient reliable interference-aware periodic broadcast messaging protocol for MANETs

Mobile ad-hoc networks (MANETs) have been widely employed in many fields including critical information delivery in open terrains as in tactical area, vehicular or disaster area network scenarios. To provide effective network maintenance for those MANETs, it is essential to adopt proper control communication methods, which provide reliable delivery of network information. However, it is difficult to provide control communication that meets the quality of service requirements due to the broadcasting of control messages and dynamic nature of MANETs. Interference is one of the major problems that degrades this service quality, especially for the networks deployed in open terrain environments. Moreover, large and dense MANET scenarios further complicate this problem. Even though many communication methods have been proposed in the literature, a satisfactory one for periodic and broadcast delivery of control packets considering the interference awareness and at the same time yielding high reliability, goodput, energy efficiency still does not exist for MANETs. To that end, we present a new control communication protocol, which is referred to as the Interference-Aware Periodic Broadcast Messaging (IPBM) protocol, for those MANETs deployed in interference-rich open terrains. We show that the proposed interference awareness mechanism of IPBM, in which the transmission power of the units is increased at certain periods, significantly reduces the packet loss caused by the interference problem. Moreover, IPBM achieves an important amount of increase in the link reliability as well as in goodput with the least power consumption among the evaluated solutions. The mobility support feature of IPBM makes the protocol applicable not only to large and dense but also to highly dynamic MANETs. Besides, IPBM can properly work alongside the deployed main data communication protocol, since it provides valuable network information to be manipulated. Simulation results under both static and dynamic topologies confirm that adopting the IPBM protocol in the intended MANET scenarios significantly increases the reliability and goodput as well as the energy efficiency.

Bloom Hopping: Bloom Filter Based 2-Hop Neighbor Management in VANETs

Recent works have shown that it would be beneficial for nodes in wireless networks with very dynamic topology to maintain a list of 2-hop neighbors, namely, the neighbors of its neighbors. This is important, for example, for routing, clustering, and message dissemination to all the nodes in a given geographic vicinity. In this paper, we propose a scheme that uses Bloom filters for maintaining 2-hop neighborship information. Furthermore, we developed a novel 2-hop broadcast algorithm making use of the specific nature of our Bloom filter encoded neighbor information. We particularly focus on the Vehicular Ad Hoc Networks (VANETs) application scenario. Here, beaconing is a periodic broadcast of awareness messages by each vehicle to its immediate neighbors. A naive approach would be to include all 2-hop neighbors in each beacon message, which, however, would work only for small or sparse scenarios. We show that our approach significantly reduces the length of the beacon messages, thereby keeping channel load and collision probability considerably lower than in the naive scheme. We further demonstrate the application of our Bloom filter based 2-hop neighbor table for developing higher layer protocols and introduce a multi-hop broadcast protocol called Bloom Hopping.

Modelling a vehicle‐ID‐based IEEE 802.11OCB MAC scheme for periodic broadcast in vehicular networks

Periodic broadcast of cooperative awareness messages (CAMs) is of great importance considering safety-related applications, for a network like VANET. This study proposes a vehicle-identifier (ID)-based MAC scheme for the periodic broadcast of CAMs in a vehicular network. Each CAM generated by a vehicle is associated with a unique ID. This study uses this attribute of CAM messages while participating in the channel assessment procedure. Each vehicle weighs the random back-off number with the unique ID incorporated in their respective CAM. This eventually leads to the selection of a vehicle-ID-based random back-off number, mitigating all possible probabilities of collision due to same back-off number selection. The simulation is performed considering saturated traffic conditions, to analyse its behaviour under most critical situations. The proposed model eliminates the chances of selecting zero as the initial back-off number, eliminating any chances of consecutive freeze process. The proposed one-dimensional Markovian model is validated by MATLAB. The proposed model provides a clear depiction that it performs better than the traditional IEEE 802.11OCB used for VANET. Also, it is worth noting that the achieved results outperform the existing work in terms of average packet delay since nearly one-fourth of the contention window size is utilised throughout the simulation.

FL-ASB: A Fuzzy Logic Based Adaptive-period Single-hop Broadcast Protocol

In vehicular ad hoc networks, vehicle-to-vehicle–based broadcast can fast disseminate safety messages between vehicles within the whole network and hence expand drivers perception vision, which will reduce the accident probability and ensure the transportation reliability. As for fixed-period single-hop broadcast protocol, disseminating safety messages frequently can cause excessive network load. However, increasing period purely does not guarantee the real-time performance. In addition, exiting adaptive-period single-hop broadcast protocols also have limitations without considering synthetically various impact factors. Thus, how to design a single-hop broadcast protocol that can dynamically adjust the broadcast period according to the actual road condition is a pressing issue. A Fuzzy Logic Based Adaptive-period Single-hop Broadcast Protocol in vehicular ad hoc networks is designed in this article, which provides a new solution for the dissemination of period safety messages. In this article, the impact of various factors (such as the number of one-hop neighbor nodes, vehicle speed, received signal strength index, and visibility) on the single-hop broadcast period has been analyzed. In view of each impact factor, we design corresponding membership function and fuzzy rules according to the specific scenarios and parameters. It realizes the adaptive changes of period safety messages broadcast period through the simulation of the proposed fuzzy logic inference system. Finally, we verify the performance of the Fuzzy Logic Based Adaptive-period Single-hop Broadcast Protocol in a bidirectional four-lane highway scenario. Simulation results show that the proposed Fuzzy Logic Based Adaptive-period Single-hop Broadcast Protocol has obvious advantages in terms of network load ratio, average one-hop delay, and delivery ratio.

Reliable Cooperative Authentication for Vehicular Networks

Vehicular ad-hoc networks (VANETs) have been researched with regard to enhance driver's safety and comfort. In VANETs, all vehicles share their status and road conditions with neighboring nodes by periodically generating safety messages. To provide reliable VANET services, message authentication is an important feature. In particular, anonymous message authentication has attracted considerable interest, because periodic broadcast messages from a vehicle can be used to track its location. Unfortunately, previously proposed anonymous message authentication protocols had serious practical shortcomings, including high communication, authentication, and revocation costs, as well as reliability issues. Thus, in this paper, we propose an anonymous authentication protocol based on a cooperative authentication method. The proposed method does not require mode synchronization between cooperative and non-cooperative authentication. In addition, we design a two-layer pseudo-identity generation method and construct a key update tree for efficient revocation. Simulations show that our protocol does not result in packet losses caused by authentication overheads, even when the vehicle density is 200/km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

AUV-Aided Joint Localization and Time Synchronization for Underwater Acoustic Sensor Networks

For the purpose of localization and time synchronization of underwater sensor networks, buoys are generally distributed on the sea surface of the area of interest, serving as fixed anchors. However, this method is not economical and has poor scalability. An alternative is to employ an autonomous underwater vehicle (AUV) as a mobile anchor. By receiving the periodical broadcast signals from the AUV, any sensor in the communication range can measure time of arrival of received packets and obtain a series of nonlinear equations. In this letter, we proposed an efficient linear algorithm to solve the nonlinear equations, and gave closed-form positioning and synchronization error analysis. Besides, we show that the proposed method can approach the Cramér-Rao lower bound by both theoretical analysis and simulation.

The Modeling and Cross-Layer Optimization of 802.11p VANET Unicast

Vehicular ad-hoc networks (VANETs) play an important role in enabling ubiquitous communications and connectivity among vehicles in intelligent transportation systems. Various messages can be transmitted in a VANET to improve road safety and furnish multiple types of application services. Therefore, the evaluation of VANET performance and its optimization should be considered. Previous conventional considerations regarding VANET modeling merely incorporated a general homogeneous road traffic scenario. Furthermore, prior research works primarily focused on the broadcasting performance in VANETs, since the safety beacon packets are transmitted in periodic broadcast. However, the exchange of some important data between vehicles is better accomplished by using unicast instead of broadcast with the retransmission mechanism. On the other hand, in the context of VANET optimization, most conventional schemes required continuous monitoring of the network by measuring the number of neighboring nodes to configure the transmission power or adjusting the transmission rate accordingly. Such constant tracking leads to large transmission overheads and measurement delay. In this paper, we propose a set of 802.11p unicast modeling and optimization methodologies to determine the optimal network parameters without continuously monitoring the vehicles in vicinity. This is accomplished by integrating a stochastic urban traffic model in the analysis then performing a cross-layer optimization for each network node to reduce packet collisions. The optimal transmission range and contention window size at different locations are derived based on the spatio-temporal velocity profile and are made known to entering vehicles. These aid the vehicles to configure their transmission power and rate accordingly upon entering a road segment. We evaluate the proposed system in terms of the network delay and throughput performance. Considerable simulation runs to verify the feasibility of the proposed model and optimization methods. Our results indicate that delay (throughput) is improved by about 53% (120%) on average for homogeneous traffic and 45% (104%) on average for heterogeneous traffic.

CLPS: context-based location privacy scheme for VANETs

Location privacy preservation is considered as a challenge for deploying vehicular ad hoc networks (VANETs). In fact, the continuous periodical broadcast of spatiotemporal information in beacons allows a global passive adversary (GPA) to link pseudonyms and reconstruct vehicle traces. Consequently, it is imperative that a vehicle selects the right context to change pseudonym to confuse the adversary and ensure pseudonyms unlinkability. In this paper, we propose a context-based location privacy scheme (CLPS) that makes the following contributions: i) a pseudonym changing strategy that allows a vehicle to change pseudonyms based on its context; ii) a linkability threat, called cheating attack that negatively affects the proposed pseudonym changing strategy. A cheating detection mechanism is developed to allow a vehicle to detect misbehaving vehicles that launch the cheating attack, and assess the success of the pseudonym change. Finally, we evaluate CLPS against GPA by simulations using privacy extension, PREXT, in Veins, and we compare it against different existing privacy schemes.

Intervehicle Range Estimation From Periodic Broadcasts

Dedicated short-range communications enables vehicular communication using periodic broadcast messages. We propose to use these periodic broadcasts to perform intervehicle ranging. Motivated by this scenario, we study the general problem of range estimation between pairs of moving vehicles using periodic broadcasts. Each vehicle has its own independent and unsynchronized clock, which can exhibit significant drift between consecutive periodic broadcast transmissions. Consequently, both the clock offsets and drifts need to be taken into account in addition to the vehicle motion to accurately estimate the vehicle ranges. We develop a range estimation algorithm using local polynomial smoothing of the vehicle motion. The proposed algorithm can be applied to networks with arbitrary number of vehicles and requires no additional message exchanges apart from the periodic broadcasts. We experimentally validate our algorithm and show that its performance is close to that of unicast round-trip time ranging. In particular, we are able to achieve submeter ranging accuracies in vehicular scenarios. Our scheme requires additional timestamp information to be transmitted as part of the broadcast messages, and we develop a novel timestamp compression algorithm to minimize the resulting overhead.

A broadcast scheme for vehicle-to-pedestrian safety message dissemination

Ensuring cooperative awareness by periodic message beaconing in vehicular environments is necessary to address pedestrian safety. However, high periodic basic safety message broadcasting in dense vehicular environments makes accessing the communication channel very competitive. Furthermore, high-frequency periodic broadcasting causes fast device energy dissipation which is a key issue for small computing devices used in wireless sensor and mobile communications. Therefore, in order to achieve reliable message dissemination for vehicle-to-pedestrian safety, energy loss minimization mechanisms for pedestrian mobile devices should be developed. This article proposes controlling the number of broadcasts by eliminating periodic safety message broadcasts from pedestrian nodes; these nodes only receive broadcasts from vehicles and then conditionally communicate with the vehicles when safety alerts are raised. When the pedestrian nodes do not receive messages from any vehicle for a specified period, pedestrian no...

Enhanced local density estimation in internet of vehicles

The Internet of vehicles allows connecting vehicles to the Internet to make all data from vehicles available for applications aimed towards improving safety and comfort for passengers. Density is one of the most important sensed data to gather. This information is mainly obtained through periodic messages broadcast by the neighbouring vehicles. However, the availability of this information depends on the Internet. A low penetration rate of Internet of vehicles, or the loss of Internet connection, can significantly affect the accuracy of the sensed density. Moreover, the reception rate of the periodic messages seriously drops at short distances caused by the broadcast storm problem in high-density scenarios. To address this problem, using inter-vehicular communications, we propose a segment-based approach for enhancing the accuracy of the local density estimation. This approach provides a highly accurate estimation with low overhead over the maximum vehicles transmission range to all the vehicles. The proposed approach is extensively evaluated analytically and by simulation. Performance evaluation results show that our approach SLDE allows about 3% of mean error ratio with low overhead over the maximum transmission range.

Video On-Demand Service via Wireless Broadcasting

Video on-demand (VoD) service is very popular over the mobile Internet. With the demand and quality of video contents become increasingly high, the capacity demand on mobile networks is explosively increasing. In order to sustainably accommodate the future traffic growth, operators such as Verizon start to offload video traffic with broadcasting. However, how to improve VoD users’ quality of experience (QoE) under wireless broadcasting is still an open issue, where the major challenge is the time-varying wireless channel capacity. In this paper, we design a wireless VoD scheme with a periodic broadcasting approach. The basic idea is to fragment a video into segments, which are then delivered over different broadcasting channels periodically. We integrate network coding into our scheme so that packet redundancy can counteract the wireless unreliability. Moreover, we reveal the fundamental limits our proposed scheme can achieve in terms of two key QoE metrics: access delay and probability of continuous playout. We then show the intrinsic connections between the two QoE metrics and the choice of design parameters. The tradeoff between QoE improvement and bandwidth overhead is also presented. We implement the scheme in a testbed and demonstrate comprehensive experiment results.

Organizing XML Data in a Wireless Broadcast System by Exploiting Structural Similarity

Wireless data broadcast is an efficient way of delivering data of common interest to a large population of mobile devices within a proximate area, such as smart cities, battle fields, etc. In this work, we focus ourselves on studying the data placement problem of periodic XML data broadcast in mobile and wireless environments. This is an important issue, particularly when XML becomes prevalent in today’s ubiquitous and mobile computing devices and applications. Taking advantage of the structured characteristics of XML data, effective broadcast programs can be generated based on the XML data on the server only. An XML data broadcast system is developed and a theoretical analysis on the XML data placement on a wireless channel is also presented, which forms the basis of the novel data placement algorithm in this work. The proposed algorithm is validated through a set of experiments. The results show that the proposed algorithm can effectively place XML data on air and significantly improve the overall access efficiency.