Deterministic broadcasting in ad hoc radio networks

We consider the problem of distributed deterministic broadcasting in radio networks of unknown topology and size. The network is synchronous. If a node u can be reached from two nodes which send messages in the same round, none of the messages is received by u. Such messages block each other and node u either hears the noise of interference of messages, enabling it to detect a collision, or does not hear anything at all, depending on the model. We assume that nodes know neither the topology nor the size of the network, nor even their immediate neighborhood. The initial knowledge of every node is limited to its own label. Such networks are called ad hoc multi-hop networks. We study the time of deterministic broadcasting under this scenario. For the model without collision detection, we develop a linear-time broadcasting algorithm for symmetric graphs, which is optimal, and an algorithm for arbitrary n-node graphs, working in time . Next we show that broadcasting with acknowledgement is not possible in this model at all. For the model with collision detection, we develop efficient algorithms for broadcasting and for acknowledged broadcasting in strongly connected graphs. Received: January 2000 / Accepted: June 2001     

Broadcasting in undirected ad hoc radio networks

We consider distributed broadcasting in radio networks, modeled as undirected graphs, whose nodes have no information on the topology of the network, nor even on their immediate neighborhood. For randomized broadcasting, we give an algorithm working in expected time in n-node radio networks of diameter D, which is optimal, as it matches the lower bounds of Alon et al. [1] and Kushilevitz and Mansour [16]. Our algorithm improves the best previously known randomized broadcasting algorithm of Bar-Yehuda, Goldreich and Itai [3], running in expected time . (In fact, our result holds also in the setting of n-node directed radio networks of radius D.) For deterministic broadcasting, we show the lower bound on broadcasting time in n-node radio networks of diameter D. This implies previously known lower bounds of Bar-Yehuda, Goldreich and Itai [3] and Bruschi and Del Pinto [5], and is sharper than any of them in many cases. We also give an algorithm working in time , thus shrinking - for the first time - the gap between the upper and the lower bound on deterministic broadcasting time to a logarithmic factor. Received: 1 August 2003, Accepted: 18 March 2005, Published online: 15 June 2005 Dariusz R. Kowalski: This work was done during the stay of Dariusz Kowalski at the Research Chair in Distributed Computing of the Université du Québec en Outaouais, as a postdoctoral fellow. Research supported in part by KBN grant 4T11C04425. Andrzej Pelc: Research of Andrzej Pelc was supported in part by NSERC discovery grant and by the Research Chair in Distributed Computing of the Université du Québec en Outaouais.     

Activating anonymous ad hoc radio networks

We consider the task of activating an anonymous ad hoc radio network from a single source, by a deterministic algorithm. In the beginning only the source is active and has to activate other nodes by disseminating messages throughout the network. Nodes of the network do not know its topology and they do not have distinct labels. In such networks some nodes are impossible to reach. A node in a network is accessible if it can be activated by some (possibly network-dependent) deterministic algorithm. We show that the problem of recognizing whether a given node of an anonymous radio network is accessible, can be solved in polynomial time for the synchronous scenario. A deterministic wake-up algorithm for ad hoc networks is universal if it activates all accessible nodes in all networks. We study the question of the existence of such a universal activating algorithm. For synchronous communication we design a universal activating algorithm, and for asynchronous communication we show that no such algorithm exists. Research partially supported by NSERC discovery grant and by the Research Chair in Distributed Computing at the Université du Québec en Outaouais. A preliminary version of this paper (with title “Waking up anonymous ad hoc radio networks”) appeared in the Proceedings of the 19th International Symposium on Distributed Computing (DISC 2005), September 2005, Cracow, Poland.     

Adaptive initialization algorithm for ad hoc radio networks with carrier sensing

We propose an algorithm for coordinating access to a shared broadcast channel in an ad hoc network of unknown size n$n$. We reduce the runtime necessary to self-organize access to the channel over the previous algorithm of Cai, Lu and Wang. The runtime of that algorithm is O(n)$O\left(n\right)$. The goal of our work is to improve the constant factor in this estimation. Apart from the experimental evidence of algorithm quality, we provide a rigorous probabilistic analysis of its behavior.     

无线Ad hoc网络中基于网络编码的数据广播协议*

针对节点随机分布的无线Ad hoc网络中数据广播风暴问题,设计了一种基于网络编码的数据广播协议ENCBP。ENCBP采用了渐进式随机线性网络编码技术、自适应概率转发机制以及随机延迟发送机制。NS2仿真结果表明,与现有数据广播协议相比,该协议改善了投递率和传输延迟,协议开销较小。     

Efficient implementations of all-to-all broadcasting in mobile ad hoc networks

In order to ease the challenging task of information dissemination in a MANET, we employ a legend: a data structure passed around a network to share information with all the mobile nodes. Our motivating application of the legend is sharing location information. Previous research shows that a simplistic legend performs better than other location services in the literature. To realize the full potential of legend-based location services, we propose three methods for the legend to traverse a network and compare their performance in simulation. Two of our proposed methods are novel, and the third is an improvement on an existing method. We also evaluate several general improvements to the traversal methods, and describe our way of making the legend transmission reliable. The result is a simple, lightweight location service that makes efficient use of network resources. Beyond using the legend as a location service, we discuss several implementation aspects of providing an efficient all-to-all broadcast operation, including legend reliability, preventing duplicate legends, using a legend in dynamic networks, and working with non-synchronized clocks. We also provide pseudocode for our legend traversal methods to aid implementation.     

Context-aware broadcasting approaches in mobile ad hoc networks

The aim of this paper is to compare different context-aware broadcasting approaches in mobile ad hoc networks (MANETs) and to evaluate their respective performances. Message broadcasting is one of the core challenges brought up by distributed systems and has therefore largely been studied in the context of traditional network structures, such as the Internet. With the emergence of MANETs, new broadcasting algorithms especially geared at these networks have been introduced. The goal of these broadcasting algorithms is to ensure that a maximum number of nodes deliver the broadcasted message (reliability), while ensuring that the minimum number of nodes retransmit the broadcasted message (efficiency), in order to save their resources, such as bandwidth or battery. In recent years, as more and more mobile devices have become context-aware, several broadcasting algorithms have been introduced that take advantage of contextual information in order to improve their performance. We distinguish four approaches with respect to context: (1) context-oblivious approaches, (2) network traffic-aware approaches, (3) power-aware approaches, and (4) location-aware approaches. This paper precisely aims at presenting these four different broadcasting approaches and at measuring the performance of algorithms built upon them.     

Distributed reformation of core-based group-shared multicast trees in mobile ad hoc networks

This paper proposes a method to reduce the cost of a core-based group-shared multicast tree, where the cost is evaluated by the total bandwidth consumption of multicasting packets among all group members. Due to the broadcast nature of radio transmissions, we find that the challenge of determining minimum cost multicast tree can be approximated by finding the multicast tree with a minimum number of non-leaves (the minimum non-leaf multicast tree problem). However, we also find that the minimum non-leaf multicast tree problem is NP-complete. Thus, a method is proposed to dynamically reduce the number of non-leaves in an existing multicast tree. Experimental results show that our method reduces the cost of the multicast tree in both geometrically and randomly distributed network models and the random waypoint mobility model.     

A fault tolerant mutual exclusion algorithm for mobile ad hoc networks

In this paper, we propose a permission-based message efficient mutual exclusion (MUTEX) algorithm for mobile ad hoc networks (MANETs). To reduce messages cost, the algorithm uses the “look-ahead” technique, which enforces MUTEX only among the hosts currently competing for the critical section. We propose mechanisms to handle dozes and disconnections of mobile hosts. The assumption of FIFO channel in the original “look-ahead” technique is also relaxed. The proposed algorithm can also tolerate link or host failures, using timeout-based mechanisms. Both analytical and simulation results show that the proposed algorithm works well under various conditions, especially when the mobility is high or load level is low. To our knowledge, this is the first permission-based MUTEX algorithm for MANETs.     

Rapid almost-complete broadcasting in faulty networks

This paper studies the problem of broadcasting in synchronous point-to-point networks, where one initiator owns a piece of information that has to be transmitted to all other vertices as fast as possible. The model of fractional dynamic faults with threshold is considered: in every step either a fixed number c(G)−1$c\left(G\right)-1$, where c(G)$c\left(G\right)$ is the edge connectivity of the communication graph, or a fraction α$\alpha$ of sent messages can be lost depending on which quantity is larger.     

Efficient broadcasting in ad hoc wireless networks using directional antennas

Using directional antennas to conserve bandwidth and energy consumption in ad hoc wireless networks (or simply ad hoc networks) is becoming popular. However, applications of directional antennas for broadcasting have been limited. We propose a novel broadcast protocol called directional self-pruning (DSP) for ad hoc wireless networks using directional antennas. DSP is a nontrivial generalization of an existing localized deterministic broadcast protocol using omnidirectional antennas. Compared with its omnidirectional predecessor, DSP uses about the same number of forward nodes to relay the broadcast packet, while the number of forward directions that each forward node uses in transmission is significantly reduced. With the lower broadcast redundancy, DSP is more bandwidth and energy-efficient. DSP is based on 2-hop neighborhood information and does not rely on location or angle-of-arrival (AoA) information. Two special cases of DSP are discussed: the first one preserves shortest paths in reactive routing discoveries; the second one uses the directional reception mode to minimize broadcast redundancy. DSP is a localized protocol. Its expected number of forward nodes is O(1) times the optimal value. An extensive simulation study using both custom and ns2 simulators show that DSP significantly outperforms both omnidirectional broadcast protocols and existing directional broadcast protocols.     

Modeling and performance analysis of ad hoc broadcasting schemes

Broadcasting is a technique widely used for distributing control packets in ad hoc networks. The traditional flooding scheme has been proven to unnecessarily consume network capacity and may lead to severe packet collisions in high-density networks. New schemes have been proposed for alleviating this so-called broadcast storm problem and their efficiencies are usually analyzed and compared by ns-2 simulations. However, little work has been done on mathematical modeling and rigorous analysis. In this paper, we focus on two popular ad hoc broadcasting schemes and provide their detailed analysis in one-dimensional and two-dimensional ideal networks. The statistical results obtained have revealed new relationships between network parameters and the performance metrics. These results are useful for optimally setting network parameters in designing protocols. It is also expected that the analytical methods developed will lay a solid foundation for the development of mathematical models for other ad hoc broadcast and multicast schemes.     

An election algorithm to ensure the high availability of leader in large mobile ad hoc networks

A fundamental problem of distributed systems, leader election, is presented in the context of mobile ad hoc networks (MANETs). In many distributed systems, the presence of a leader is necessary in order to monitor underlying computations, guarantee quality functioning, take checkpoints, generate the lost token, detect quiescence conditions, etc. Hence, several leader election algorithms have been proposed in the literature. Although, most of the algorithms focus on reducing the control message (messages that have the highest priority to deliver) count, there have been almost no attention on ensuring high availability of a leader despite various types of failures, especially, in the scenarios like rescue and warfare, where the absence of the leader, even for a short duration, may lead to havoc. We focus on this issue, particularly, for large MANETs, where a large number of applications fails to perform in the absence of a leader. We present a leader election algorithm for large MANETs. The algorithm is inspired by the concept of prevailing parliamentary democracy and elects three best-nodes – in terms of performance parameters like battery life, computing power, memory, hop distance, and mobility – as the president, leader, and vice leader. The president node works as the leader of the network, in case, the leader and the vice leader both become unavailable simultaneously. On the other hand, the leader node serves all the requests. Further, we create a house of elite nodes, which ensures the presence of an executive, i.e. a leader during re-election to restrict the message overhead as well as the election latency while executing coordination related activities.     

Revisiting relative neighborhood graph-based broadcasting algorithms for multimedia ad hoc wireless networks

Multimedia broadcasting is a popular application in an ad hoc wireless network, itself composed of battery-operated nodes. Hence, energy conservation and avoidance of frequent re-construction of broadcast paths are crucial to ensure robust and uninterrupted service of multimedia broadcasting applications. This paper introduces a class of distributed broadcast algorithms based on variations of Relative Neighborhood Graphs (RNG). In contrast to the original RNG-based algorithms, the proposed algorithms consider the remaining battery energy of nodes and the distance between nodes as criteria for determining the relative neighborhood of a node. This approach is intended to boost the resiliency of the broadcast path by avoiding the choice of nodes with low remaining battery capacity as rebroadcast nodes. Extensive simulations are conducted, demonstrating that the proposed algorithms improve over the original RNG in several aspects, including the reduction of broadcast storms, longer path lifetime, and shorter broadcast latency.     

Performance evaluation of dynamic probabilistic broadcasting for flooding in mobile ad hoc networks

In mobile ad hoc networks (MANETs), flooding is a required message dissemination technique for network-wide broadcast. The conventional blind flooding algorithm causes broadcast storm problem, a high number of unnecessary packet rebroadcasts thus resulting in high contention and packet collisions. This paper proposes a new probabilistic approach that dynamically fine-tunes the rebroadcasting probability of a node for routing request packets (RREQs) according to the number of neighbour nodes. We evaluate the performance of the proposed approach for the ad hoc on demand distance vector (AODV) routing protocol and compared against the blind flooding, fixed probabilistic and adjusted probabilistic flooding [L.M.M.M. Bani-Yassein, M. Ould-Khaoua et al., Performance analysis of adjusted probabilistic broadcasting in mobile ad hoc networks, International Journal of Wireless Information Networks 13(2) (2006) 127–140; M.B. Yassein, M.O. Khaoua et al., Improving route discovery in on-demand routing protocols using local topology information in MANETs, Proceedings of the ACM international workshop on Performance Monitoring, Measurement, and Evaluation of Heterogeneous Wireless and Wired Networks, Terromolinos, Spain, ACM Press, 2006, pp. 95–99.] approaches. The simulation results show that our proposed approach demonstrates better performance than blind flooding, fixed probabilistic and adjusted flooding approaches.     

Fast deterministic broadcast and gossiping algorithms for mobile ad hoc networks

We present a mobility resilient deterministic broadcast algorithm with worst-case time complexity of O(nlogn)$O(nlogn)$ for ad hoc networks where the nodes possess collision detection capabilities; n$n$ is the total number of nodes in the network. The algorithm is based on a breadth-first traversal of the network and allows multiple simultaneous transmissions by the nodes. The idea of this broadcast algorithm is then extended to develop a mobility resilient deterministic gossiping algorithm having O(Dnlogn)$O(Dnlogn)$ worst-case run time (D$D$ is the diameter of the network graph), which is an improvement over the existing algorithms. Simulation results show that on an average, the time for completing the broadcast or gossiping is significantly lower than the theoretical worst-case time requirement.     

Distributed cooperative spectrum sensing in cognitive radio for ad hoc networks

Cognitive radio refers to an intelligent radio with the capability of sensing the radio environment and dynamically reconfiguring the operating parameters. Recent research has focused on using cognitive radios in ad hoc environments. Spectrum sensing is the most important aspect of successful cognitive radio ad hoc network deployment to overcome spectrum scarcity. Multiple cognitive radio users can cooperate to sense the primary user and improve sensing performance. Cognitive radio ad hoc networks are dynamic in nature and have no central point for data fusion. In this paper, gradient-based fully distributed cooperative spectrum sensing in cognitive radio is proposed for ad hoc networks. The licensed band used for TV transmission is considered the primary user. The gradient field changes with the energy sensed by cognitive radios, and the gradient is calculated based on the components, which include energy sensed by secondary users and received from neighbors. The proposed scheme was evaluated from the perspective of reliable sensing, convergence time, and energy consumption. Simulation results demonstrated the effectiveness of the proposed scheme.