Multi-hop Broadcast Research Articles

Capacity of practical wireless multihop broadcast networks

In a wireless multihop broadcasting scenario, a number of relay nodes may cooperate the source node in order to improve the capacity of the network. However, the imposition of total energy and maximum hop constraints to this system in a practical setting. In this paper, we study an ad-hoc network with infinitely many nodes and analytically find the number and positions of rebroadcasting relay nodes to achieve the optimal broadcast capacity. The interference due to multiple transmissions in the same geographical area is taken into account. According to the results of this theoretical model, we propose two heuristics, one distributed and one centralized, as suboptimal but practical solutions to the relay selection problem in wireless multihop broadcasting. We discuss the broadcast capacity performances and CSI (channel state information) requirements of these algorithms. The results illustrate that the benefits of peer-assisted broadcasting are more pronounced in the centralized relay selection algorithm when compared to the fully randomized and distributed selection under a realistic system model.

Going realistic and optimal: A distributed multi-hop broadcast algorithm for vehicular safety

A subject of great interest and important investments by governments, navigation system companies and street management authorities is highway safety. In this context, an important role is played by applications designed to warn drivers of upcoming dangers. An example is vehicular accident warning systems, which advertise accident events to approaching vehicles. The effectiveness of currently in use vehicular accident warning systems can be jeopardized by their: (a) inability to provide an accident warning to the closest approaching vehicles; and, (b) high delays in advertising an event. In fact, such systems are unable to reach the vehicles that are closest to an accident site due to the absence of any deployed automatic detection and broadcast mechanisms. The future deployment of Vehicular Ad hoc Networks (VANETs) can fill this gap. By leveraging on the distributed nature of ad hoc networks, accident warning systems can rapidly alert the vehicles which most risk their involvement in a crash. To reach this goal, VANET-based accident warning systems require the design of efficient broadcast algorithms. A number of solutions have been proposed in the past few years. However, no such proposals, to the best of our knowledge, assume realistic wireless propagation scenarios. The scope of this paper is to present an optimal distributed algorithm, working at the application layer, for the broadcast of safety messages in VANETs. Optimality, in terms of delay, is achieved in unidimensional highway scenarios and under realistic wireless propagation assumptions. This is the only algorithm, to this date, capable of reaching all vehicles with the minimum number of transmissions within a realistic setting.

Opportunistic broadcast of event-driven warning messages in Vehicular Ad Hoc Networks with lossy links

Multi-hop broadcast is a key technique to disseminate time-sensitive event-driven safety warning messages (WMs) in Vehicular Ad hoc Networks (VANETs). Due to the lossy nature of the vehicular wireless environment and the fact that the implementation of broadcast at the link layer uses unreliable transmissions (i.e., lack of positive ACKs), highly reliable, scalable, and fast multi-hop broadcast protocol is particularly difficult to design in VANETs with lossy links. Schemes that use redundant network layer broadcasts have been proposed. However, the tradeoff between reception reliability and transmission count in such schemes needs to be carefully considered. In this paper (The preliminary version of this paper appeared in [1], IEEE MASS 2009.,) we propose an opportunistic broadcast protocol (OppCast) that aims at simultaneously achieving high WM packet reception ratio (PRR) and fast multi-hop message propagation while minimizing the number of transmissions. A double-phase broadcast strategy is proposed to achieve fast message propagation in one phase and to ensure high PRR in the other. OppCast exploits opportunistic forwarding in each transmission to enhance the WM reception reliability and to reduce the hop delay, and to carry out reliable and efficient broadcast coordination, we propose the use of explicit broadcast acknowledgements (BACKs) which effectively reduces the number of redundant transmissions. OppCast is also extended to handle sparse and disconnected VANETs, where the protocol adaptively switches between fast opportunistic forwarding and the store-carry-and-forward paradigm. Extensive simulation results show that, compared with existing competing protocols, OppCast achieves close to 100% PRR and faster dissemination rate under a wide range of vehicular traffic densities, while using significantly smaller number of transmissions.

애드혹 네트워크에서 임시 경로 설정 유니캐스트를 기반으로 한 향상된 멀티 홉 전송 기법

스마트 패킷 에이전트는 유비쿼터스 네트워크 환경에서 사용자들의 단말에 라우팅 프로토콜 실행모듈과 서비스 실행모듈을 동적으로 제공해주기 위해 제안된 어플리케이션 서비스이다. 하지만 기존의 스마트 패킷 에이전트는 브로드캐스트 멀티 홉 전송기법을 사용함으로 인해 네트워크 내 트래픽 증가, 구성 노드들의 불필요한 참여, 낮은 전송 속도 등의 문제점을 발생시켰다. 본 논문에서는 브로드캐스트 멀티 홉 전송기법의 패킷 전송 소요 시간을 줄이고 네트워크 트래픽을 개선하기 위한 유니캐스트 기반의 멀티 홉 전송기법을 제안한다. 유니캐스트 기반의 멀티 홉 전송기법은 u-Zone Master가 이동 노드와의 Hop Counter 계산을 통하여 임시 라우팅 경로를 설정하게 함으로써, 스마트 패킷 에이전트의 네트워크 트래픽과 패킷 재전송률을 감소시킨다. 또한 본 논문에서는 슬라이딩 윈도우 기반의 UDP 전송 방식을 제안하여 기존의 Stop&Wait 방식이 지니고 있던 낮은 전송 속도 문제를 개선하였다. 제안 방식의 개선 사항은 성능 분석의 결과로 입증한다. Smart packet agent is an application that is proposed to provide routing protocol and service module in ubiquitous network environment. However, it uses multi-hop broadcast, thus it causes increasing network traffic, low-speed data transmission, and the unnecessary joining nodes. In this paper, a transmit technique that uses unicast-based multi-hop to have lower network traffic and faster transmission time than the multi-hop broadcast technique. In our scheme, u-Zone Master establishes temporary routing paths by calculating moving nodes' hop-counter. Therefore, it reduces smart packet agent's network traffic and retransmission rate. Besides, this paper proposed an UDP transmission that bases on sliding window. Hence, the Stop & Wait transmission speed is improved. The results, which are taken by analyzing performance prove that the proposed scheme has better performance.

A Novel Position-based Multi-hop Broadcast Protocol for Vehicular Ad Hoc Networks

Vehicular Ad Hoc Networks (VANETs) are considered as a promising scheme to actively guarantee vehicle safety, and broadcast is a key technology for warning message dissemination in VANETs. This paper proposes a novel Position-based Multi-hop Broadcast (PMB) protocol for VANETs in view of some shortcomings of existing broadcast protocols for VANETs, such as ignoring the differences of transmission range among different nodes (vehicles), and disseminating warning messages only with the help of nodes in the one-way lane, PMB calculates waiting time to select the rebroadcast nodes based on additional coverage area of adjacent nodes considering the transmission ranges of nodes together with the inter-vehicle spacing, to guarantee less nodes used to rebroadcast warning packets. Besides, it guarantees the reliability of warning message dissemination by adopting the alternative answering mechanism named implicit ACK and explicit ACK adaptively and rebroadcast packets based on nodes in the two-way lane. The simulation results show that PMB outperforms existing broadcast protocols for warning message dissemination in VANETs in terms of suppression of broadcast redundancy, real-time performance and reliability even if all nodes have different transmission ranges.

Comparison of robustness of time synchronisation in sensor networks

In sensor networks, time synchronisation between sensor nodes is important because it affects not only the efficiency of information gathering but also the energy consumption. Since network sizes and sensor network environments change at varying rates, different time synchronisation strategies are required for different networks. The pulse-coupled oscillator model is self-organised synchronisation method which can be used to achieve local interaction between individuals for the synchronisation of entire networks. Centralised synchronisation methods also exist, such as the multi-hop reference broadcast synchronisation method which synchronises the entire network by transmitting the differences in the timers of reference nodes through networks divided into clusters. In this paper, we compare the influence of delay jitter and packet loss resulting from the lower layer protocols on these two techniques. We also investigate the energy consumption of both methods.

On-line genetic programming of multi-hop broadcast protocols in ad hoc networks

From the family of ad hoc communication protocols the most challenging ones are those, that are designed to disseminate messages to all, or most of the nodes in the system. By their nature, these kinds of protocols use significant network resources, as the communication must involve a large fraction of the network nodes. Reducing the network load can be achieved by using the available local broadcast medium (radio channel), but it is not trivial how to select the set of nodes that should participate in the dissemination process. Previous attempts delivered algorithms that can provide reasonable performance and reliability but mostly for specific cases of ad hoc networks. In this paper a new way of tackling the broadcast problem is presented that takes no assumptions about the nature of the underlying network. Instead of using hand-optimizing protocols, we propose a framework for a self-optimizing and self-managing system inspired by natural selection and evolution. A generic distributed feed-forward performance evaluation criterion based on natural selection is presented along with an implementation of a virtual machine and a corresponding language for Genetic Programming to be used in tandem with the natural selection process.

Reliable Delay Constrained Multihop Broadcasting in VANETs

Vehicular communication is regarded as a major innovative feature for in-car technology. While improving road safety is unanimously considered the major driving factor for the deployment of Intelligent Vehicle Safety Systems, the challenges relating to reliable multi-hop broadcasting are exigent in vehicular networking. In fact, safety applications must rely on very accurate and upto-date information about the surrounding environment, which in turn requires the use of accurate positioning systems and smart communication protocols for exchanging information. Communications protocols for VANETs must guarantee fast and reliable delivery of information to all vehicles in the neighbourhood, where the wireless communication medium is shared and highly unreliable with limited bandwidth. In this paper, we focus on mechanisms that improve the reliability of broadcasting protocols, where the emphasis is on satisfying the delay requirements for safety applications. We present the Pseudoacknowledgments (PACKs) scheme and compare this with existing methods over varying vehicle densities in an urban scenario using the network simulator OPNET.

Minimum-Outage Broadcast in Wireless Networks with Fading Channels

We consider the problem of cooperative broadcasting for minimum outage in wireless networks. We consider wireless multihop broadcast as a set of transmitters that transmit in a certain order. The receiving nodes are able to combine all the previous transmissions and achieve better received SNR. We consider the problem of finding the optimal set and order of (fixed-power) transmitters that minimizes the overall outage probability in a wireless fading channel. We found the optimal solution using a Branch-and-Bound approach and proposed some suboptimal algorithms. The numerical results show that a simple algorithm that we propose performs surprisingly well.

DV-CAST: A distributed vehicular broadcast protocol for vehicular ad hoc networks

The potential of infrastructureless vehicular ad hoc networks for providing safety and nonsafety applications is quite significant. The topology of VANETs in urban, suburban, and rural areas can exhibit fully connected, fully disconnected, or sparsely connected behavior, depending on the time of day or the market penetration rate of wireless communication devices. In this article we focus on highway scenarios, and present the design and implementation of a new distributed vehicular multihop broadcast protocol, that can operate in all traffic regimes, including extreme scenarios such as dense and sparse traffic regimes. DV-CAST is a distributed broadcast protocol that relies only on local topology information for handling broadcast messages in VANETs. It is shown that the performance of the proposed DV-CAST protocol in terms of reliability, efficiency, and scalability is excellent.

Opportunistic scheduling and spectrum reuse in relay-based cellular networks

In order to understand the key merits of multiuser diversity, opportunistic scheduling and spectrum reuse techniques in downlink relay-based cellular networks, this paper analyzes the spectral efficiency performance over a fading multihop broadcast channel (MBC) composed of a base station (BS), a relay station (RS), U far users and V near users in the asymptotic regime of large number of users. Using tools from extreme-value theory, we characterize the average spectral efficiency of the MBC as a function of the number of users and physical channel parameters. Our analysis yields very accurate formulas even for moderately low values of U and V , specified in detail and verified (via Monte Carlo simulations) for the case of Rayleigh fading. Next, we consider a relay-based broadband multi-cellular network in the downlink mode; with special focus on orthogonal frequency-division multiple-access (OFDMA) resource allocation and investigate the spectral efficiency performance of opportunistic multiuser scheduling and spectrum reuse techniques based on capacity analysis and system-level simulations. This empirical study validates our analytical insights and helps to further identify design tradeoffs associated with spectrum reuse, interference management and multiuser diversity techniques in relay-based cellular networks.

A Novel Multi-hop Broadcast Protocol for Vehicular Safety Applications

Many safety applications in Vehicular Ad hoc Networks (VANETs) are based on broadcast. Designing a broadcast protocol that satisfies VANET applications' requirements is very crucial. In this paper, we propose a reliable and efficient multi-hop broadcast routing protocol for VANETs. The proposed protocol provides the strict reliability in various traffic conditions. This protocol also performs low overhead by means of reducing rebroadcast redundancy in a high-density network environment. We also propose an enhanced multipoint relay (MPR) selection algorithm that considers vehicles' mobility and then use it for relay node selection. We show the performance analysis of the proposed protocol by simulation with ns-2 in different conditions, and give the simulation results demonstrating effectiveness of the proposed protocol compared with other VANET broadcast schemes.

Congestion Awareness Multi-Hop Broadcasting for Safety Message Dissemination in VANET

The safety applications for cooperative driving in VANETs, typically require the dissemination of safety-related information to all vehicles with high reliability and a strict timeline. However, due to the high vehicle mobility, dynamic traffic density, and a self-organized network, Safety message dissemination has a special challenge to efficiently use the limited network resources to satisfy its requirements. With this motivation, we propose a novel broadcasting protocol referred to as congestion awareness multi-hop broadcasting (CAMB) based loosely on a TDMA-like transmission scheduling scheme. The proposed protocol was evaluated using different traffic scenarios within both a realistic channel model and an 802.11p PHY/MAC model in our simulation. The simulation results showed that the performance of our CAMB protocol was better than those of the existing broadcasting protocols in terms of channel access delay, packet delivery ratio, end-to-end delay, and network overhead.

A Novel Multi-hop Broadcast Protocol for Vehicular Safety Applications

A Novel Multi-hop Broadcast Protocol for Vehicular Safety Applications

Adaptive Probabilistic Broadcasting over Dense Wireless Ad Hoc Networks

We propose an idle probability-based broadcasting method,iPro, which employs an adaptive probabilistic mechanism to improve performance of data broadcasting over dense wireless ad hoc networks. In multisource one-hop broadcast scenarios, the modeling and simulation results of the proposediProare shown to significantly outperform the standard IEEE 802.11 under saturated condition. Moreover, the results also show that without estimating the number of competing nodes and changing the contention window size, the performance of the proposediProcan still approach the theoretical bound. We further applyiProto multihop broadcasting scenarios, and the experiment results show that within the same elapsed time after the broadcasting, the proposediProhas significantly higher Packet-Delivery Ratios (PDR) than traditional methods.

An Epidemic Theoretic Framework for Vulnerability Analysis of Broadcast Protocols in Wireless Sensor Networks

While multi-hop broadcast protocols, such as Trickle, Deluge and MNP, have gained tremendous popularity as a means for fast and convenient propagation of data/code in large scale wireless sensor networks, they can, unfortunately, serve as potential platforms for virus spreading if the security is breached. To understand the vulnerability of such protocols and design defense mechanisms against piggy-backed virus attacks, it is critical to investigate the propagation process of these protocols in terms of their speed and reachability. In this paper, we propose a general framework based on the principles of epidemic theory, for vulnerability analysis of current broadcast protocols in wireless sensor networks. In particular, we develop a common mathematical model for the propagation that incorporates important parameters derived from the communication patterns of the protocol under test. Based on this model, we analyze the propagation rate and the extent of spread of a malware over typical broadcast protocols proposed in the literature. The overall result is an approximate but convenient tool to characterize a broadcast protocol in terms of its vulnerability to malware propagation. We have also performed extensive simulations which have validated our model.

차량간 통신을 위한 위치 정보 기반의 AODV 라우팅 프로토콜

도로 기반 시설의 도움 없이 지능형 교통 시스템을 실현하기 위한 차량 간 통신(Inter-Vehicle Communication)에 대한 관심이 증가하고 있다. 차량 간 통신은 고정된 인프라 없이 차량간에 실시간 정보를 교환할 수 있게 해준다. 차량 간 통신 시스템은 정보를 전송하기 위해 멀티 홉 브로드캐스트 방식을 사용한다. 본 논문에서는 차량 간 통신을 위한 위치 정보 기반의 AODV 라우팅 프로토콜을 제안한다. 제안하는 AODV 라우팅 프로토콜은 위치 정보를 갖는 Hello 패킷을 전송하여 노드간 거리를 계산한다. 그런 다음 각 노드의 거리테이블을 이용하여 신속한 경로 복구를 수행한다. 제안하는 AODV 라우팅 프로토콜의 성능은 퀄넷(Qualnet) 버전 3.8 시뮬레이터를 사용하여 기존의 AODV 라우팅 프로토콜과 비교하였다. In order to realize Intelligent Transport System (ITS) without any road facilities support, Inter-vehicle Communication (IVC) is increased attention. IVC makes it possible to exchange real-time information among vehicles without centralized infrastructure. The IVC systems use multi-hop broadcast to disseminate information. In this paper, we propose the improved AODV routing protocol based on location information. The proposed AODV routing protocol transmits Hello packet with location information to calculate the distance between nodes. Then it achieves fast link recovery. We confirm the throughput performance of the proposed AODV routing protocol compared with the AODV routing protocol using Qualnet ver.3.8 simulator.

Black-Burst-Based Multihop Broadcast Protocols for Vehicular Networks

In this paper, two IEEE 802.11-based multihop broadcast protocols, namely urban multihop broadcast and ad hoc multihop broadcast, are proposed to address the broadcast storm, hidden node, and reliability problems of multihop broadcast in vehicular networks. In the proposed protocols, the functions of forwarding and acknowledging the broadcast packet are assigned to only one vehicle by dividing the road portion inside the transmission range into segments and choosing the vehicle in the furthest nonempty segment without a priori topology information. The simulation results confirm that our protocols have very high success rate and efficient channel utilization when compared with other flooding-based protocols. It is also concluded that there is no need for infrastructure support unless the line of sight among different road segments incident to an intersection is blocked with obstacles.

A scalable, power-efficient broadcast algorithm for wireless networks

Scalability and power-efficiency are two of the most important design challenges in wireless ad hoc networks. In this paper, we present a scalable, power-efficient broadcast algorithm for wireless ad hoc networks. We first investigate the trade-off between (i) reaching more nodes in a single hop using higher transmission power and (ii) reaching fewer nodes using lower transmission power and relaying messages through multiple hops. Our analysis indicates that multi-hop broadcast is more power-efficient if α ≥ 2.2, where α is the path loss exponent in the power consumption model P(r, α) = c0 ċ rα + c1. Based on the analysis, we then propose Broadcast over Local Spanning Subgraph (BLSS). In BLSS, an underlying topology is first constructed by a localized topology control algorithm, Fault-Tolerant Local Spanning Subgraph (FLSS). FLSS can preserve k- connectivity of the network, where the value of k determines the degree of fault tolerance. Broadcast messages are then simply relayed through the derived topology in a constrained flooding fashion. BLSS is fully localized, scalable, power-efficient, and fault-tolerant. Simulation results show that the performance of BLSS is comparable to that of centralized algorithms.

Cooperative Multihop Broadcast for Wireless Networks

We address the minimum-energy broadcast problem under the assumption that nodes beyond the nominal range of a transmitter can collect the energy of unreliably received overheard signals. As a message is forwarded through the network, a node will have multiple opportunities to reliably receive the message by collecting energy during each retransmission. We refer to this cooperative strategy as accumulative broadcast. We seek to employ accumulative broadcast in a large scale loosely synchronized, low-power network. Therefore, we focus on distributed network layer approaches for accumulative broadcast in which loosely synchronized nodes use only local information. To further simplify the system architecture, we assume that nodes forward only reliably decoded messages. Under these assumptions, we formulate the minimum-energy accumulative broadcast problem. We present a solution employing two subproblems. First, we identify the ordering in which nodes should transmit. Second, we determine the optimum power levels for that ordering. While the second subproblem can be solved by means of linear programming, the ordering subproblem is found to be NP-complete. We devise a heuristic algorithm to find a good ordering. Simulation results show the performance of the algorithm to be close to optimum and a significant improvement over the well known BIP algorithm for constructing energy-efficient broadcast trees. We then formulate a distributed version of the accumulative broadcast algorithm that uses only local information at the nodes and has performance close to its centralized counterpart.