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81
Maximal Independent Sets in Radio Networks
"... We study the distributed complexity of computing a maximal independent set (MIS) in radio networks with completely unknown topology, asynchronous wakeup, and no collision detection mechanism available. Specifically, we propose a novel randomized algorithm that computes a MIS in time O(log 2 n) with ..."
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Cited by 37 (8 self)
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We study the distributed complexity of computing a maximal independent set (MIS) in radio networks with completely unknown topology, asynchronous wakeup, and no collision detection mechanism available. Specifically, we propose a novel randomized algorithm that computes a MIS in time O(log 2 n) with high probability, where n is the number of nodes in the network. This significantly improving on the best previously known solutions. A lower bound of Ω(log 2 n / log log n) given in [11] implies that our algorithm’s running time is close to optimal. Our result shows that the harsh radio network model imposes merely an additional O(log n) factor compared to Luby’s MIS algorithm in the message passing model. This has important implications in the context of ad hoc and sensor networks whose characteristics are closely captured by the radio network model.
The wakeup problem in multihop radio networks
 in Proc., 15th ACMSIAM Symposium on Discrete Algorithms (SODA), 2004
, 2004
"... a wakeup signal from another node. Once a node is We study the problem of waking up a collection of activated, it starts executing its wakeup protocol. This processors connected by a multihop adhoc ratio network with unknown topology, no access to a global clock, and no collision detection mecha ..."
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Cited by 34 (6 self)
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a wakeup signal from another node. Once a node is We study the problem of waking up a collection of activated, it starts executing its wakeup protocol. This processors connected by a multihop adhoc ratio network with unknown topology, no access to a global clock, and no collision detection mechanism available. Each node in the network wakesup spontaneously, or it is activated by receiving a wakeup signal from another node. All active nodes transmit the wakeup signals according to a given protocol. The running time of is the number of steps counted from the first spontaneous wakeup, until all nodes become activated. We provide two protocols for this problem. The first one is a deterministic protocol with running time. Our protocol is based on a novel concept of a rotationtolerant
Time of deterministic broadcasting in radio networks with local knowledge
 SIAM Journal on Computing
, 2004
"... Abstract. We consider broadcasting in radio networks, modeled as undirected graphs, whose nodes know only their own label and labels of their neighbors. In every step every node acts either as a transmitter or as a receiver. A node acting as a transmitter sends a message which can potentially reach ..."
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Cited by 30 (8 self)
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Abstract. We consider broadcasting in radio networks, modeled as undirected graphs, whose nodes know only their own label and labels of their neighbors. In every step every node acts either as a transmitter or as a receiver. A node acting as a transmitter sends a message which can potentially reach all of its neighbors. A node acting as a receiver in a given step gets a message if and only if exactly one of its neighbors transmits in this step. BarYehuda, Goldreich, and Itai [J. Comput. System Sci., 45 (1992), pp. 104–126] considered broadcasting in this model. They claimed a linear lower bound on the time of deterministic broadcasting in such radio networks of diameter 3. This claim turns out to be incorrect in this model (although it is valid in a more pessimistic model [R. BarYehuda, O. Goldreich, and A. Itai, Errata Regarding “On the time complexity of broadcast in radio networks: An exponential gap between determinism and randomization, ”
Fast distributed algorithm for convergecast in ad hoc geometric radio networks
 Proc. 2nd Int. Conf. on Wireless on Demand Network Systems and Service (WONS
, 2005
"... Abstract — Wireless ad hoc radio networks have gained a lot of attention in recent years. We consider geometric networks, where nodes are located in a euclidean plane. We assume that each node has a variable transmission range and can learn the distance to the closest neighbor. We also assume that n ..."
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Cited by 29 (0 self)
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Abstract — Wireless ad hoc radio networks have gained a lot of attention in recent years. We consider geometric networks, where nodes are located in a euclidean plane. We assume that each node has a variable transmission range and can learn the distance to the closest neighbor. We also assume that nodes have a special collision detection (CD) capability so that a transmitting node can detect a collision within its transmission range. We study the basic communication problem of collecting data from all nodes called convergecast. Recently, there appeared many new applications such as realtime multimedia, battlefield communications and rescue operations that impose stringent delay requirements on the convergecast time. We measure the latency of convergecast, that is the number of time steps needed to collect the data in any nnode network. We propose a very simple randomized distributed algorithm that has the expected running time O(log n). We also show that this bound is tight and any algorithm needs Ω(log n) time steps while performing convergecast in an arbitrary network. One of the most important problems in wireless ad hoc networks is to minimize the energy consumption, which maximizes the network lifetime. We study the tradeoff between the energy and the latency of convergecast. We show that our algorithm consumes at most O(n log n) times the minimum energy. We also demonstrate that for a line topology the minimum energy convergecast takes n − 1 time steps while any algorithm performing convergecast within O(log n) time steps requires Ω(n) times the minimum energy.
Gossiping in a MultiChannel Radio Network  An Oblivious Approach to Coping with Malicious Interference (Extended Abstract)
 IN: DISC 2007. LNCS
, 2007
"... We study oblivious deterministic gossip algorithms for multichannel radio networks with a malicious adversary. In a multichannel network, each of the n processes in the system must choose, in each round, one of the c channels of the system on which to participate. Assuming the adversary can disrup ..."
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Cited by 28 (9 self)
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We study oblivious deterministic gossip algorithms for multichannel radio networks with a malicious adversary. In a multichannel network, each of the n processes in the system must choose, in each round, one of the c channels of the system on which to participate. Assuming the adversary can disrupt one channel per round, “preventing“ communication on that channel, we establish (1−ɛ)n a tight bound of max Θ c−1 + logc n n(1−ɛ), Θ ɛc2 ”” on the number of rounds needed to solve the ɛgossip problem, a parameterized generalization of the alltoall gossip problem that requires (1 − ɛ)n of the “rumors ” to be successfully disseminated. Underlying our lower bound proof lies an interesting connection between ɛgossip and extremal graph theory. Specifically, we make use of Turán’s theorem, a seminal result in extremal combinatorics, to reason about an adversary’s optimal strategy for disrupting an algorithm of a given duration. We then show how to generalize our upper bound to cope with an adversary that can simultaneously disrupt t < c channels. Our generalization makes use of selectors: a combinatorial tool that guarantees that any subset of processes will be “selected ” by some set in the selector. We prove this generalized algorithm optimal if a maximum number of values is to be gossiped. We conclude by extending our algorithm to tolerate traditional Byzantine corruption faults.
A JammingResistant MAC Protocol for SingleHop Wireless Networks
, 2008
"... In this paper we consider the problem of designing a medium access control (MAC) protocol for singlehop wireless networks that is provably robust against adaptive adversarial jamming. The wireless network consists of a set of honest and reliable nodes that are within the transmission range of each ..."
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Cited by 28 (9 self)
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In this paper we consider the problem of designing a medium access control (MAC) protocol for singlehop wireless networks that is provably robust against adaptive adversarial jamming. The wireless network consists of a set of honest and reliable nodes that are within the transmission range of each other. In addition to these nodes there is an adversary. The adversary may know the protocol and its entire history and use this knowledge to jam the wireless channel at will at any time. It is allowed to jam a (1 − ɛ)fraction of the time steps, for an arbitrary constant ɛ> 0, but it has to make a jamming decision before it knows the actions of the nodes at the current step. The nodes cannot distinguish between the adversarial jamming or a collision of two or more messages that are sent at the same time. We demonstrate, for the first time, that there is a localcontrol MAC protocol requiring only very limited knowledge about the adversary and the network that achieves a constant throughput for the nonjammed time steps under any adversarial strategy above. We also show that our protocol is very energy efficient and that it can be extended to obtain a robust and efficient protocol for leader election and the fair use of the wireless channel.
A Better Wakeup in Radio Networks
, 2004
"... We present an improved algorithm to wake up a multihop adhoc radio network. The goal is to have all the nodes activated, when some of them may wake up spontaneously at arbitrary times and the remaining nodes need to be awoken by the already active ones. The best previously known wakeup algorithm ..."
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Cited by 25 (3 self)
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We present an improved algorithm to wake up a multihop adhoc radio network. The goal is to have all the nodes activated, when some of them may wake up spontaneously at arbitrary times and the remaining nodes need to be awoken by the already active ones. The best previously known wakeup algorithm was given by Chrobak, G¸asieniec and Kowalski [11], and operated in time O(n 5/3 log n), where n is the number of nodes. We give an algorithm with the running time O(n 3/2 log n). This also yields better algorithms for other synchronizationtype primitives, like leader election and localclocks synchronization, each with a time performance that differs from that of wakeup by an extra factor of O(log n) only, and improves the best previously known method for the problem by a factor of n 1/6. A wakeup algorithm is a schedule of transmissions for each node. It can be represented as a collection of binary sequences. Useful properties of such collections have been abstracted to define a (radio) synchronizer. It has been known that good radio synchronizers exist and previous algorithms [17, 11] relied on this. We show how to construct such synchronizers in polynomial time, from suitable constructible expanders. As an application, we obtain a wakeup protocol for a multipleaccess channel that activates the network in time O(k 2 polylog n), where k is the number of stations that wake up spontaneously, and which can be found in time polynomial in n. We extend the notion of synchronizers to universal synchronizers. We show that there exist universal synchronizers with parameters that guarantee time O(n 3/2 log n) of wakeup.
Secure Communication over Radio Channels
 PODC'08
, 2008
"... We study the problem of secure communication in a multichannel, singlehop radio network with a malicious adversary that can cause collisions and spoof messages. We assume no preshared secrets or trustedthirdparty infrastructure. The main contribution of this paper is fAME: a randomized (f)ast( ..."
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Cited by 24 (9 self)
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We study the problem of secure communication in a multichannel, singlehop radio network with a malicious adversary that can cause collisions and spoof messages. We assume no preshared secrets or trustedthirdparty infrastructure. The main contribution of this paper is fAME: a randomized (f)ast(A)uthenticated (M)essage (E)xchange protocol that enables nodes to exchange messages in a reliable and authenticated manner. It runs in O(Et 2 log n) time and has optimal resilience to disruption, where E is the set of pairs of nodes that need to swap messages, n is the total number of nodes, C the number of channels, and t < C the number of channels on which the adversary can participate in each round. We show how to use fAME to establish a shared secret group key, which can be used to implement a secure, reliable and authenticated longlived communication service. The resulting service requires O(nt 3 log n) rounds for the setup phase, and O(t log n) rounds for an arbitrary pair to communicate. By contrast, existing solutions rely on preshared secrets, trusted thirdparty infrastructure, and/or the assumption that all interference is nonmalicious.
Optimal Clock Synchronization in Networks
"... Having access to an accurate time is a vital building block in all networks; in wireless sensor networks even more so, because wireless media access or data fusion may depend on it. Starting out with a novel analysis, we show that orthodox clock synchronization algorithms make fundamental mistakes. ..."
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Cited by 22 (7 self)
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Having access to an accurate time is a vital building block in all networks; in wireless sensor networks even more so, because wireless media access or data fusion may depend on it. Starting out with a novel analysis, we show that orthodox clock synchronization algorithms make fundamental mistakes. The stateoftheart clock synchronization algorithm FTSP exhibits an error that grows exponentially with the size of the network, for instance. Since the involved parameters are small, the error only becomes visible in midsize networks of about 1020 nodes. In contrast, we present PulseSync, a new clock synchronization algorithm that is asymptotically optimal. We evaluate PulseSync on a Mica2 testbed, and by simulation on larger networks. On a 20 node network, the prototype implementation of PulseSync outperforms FTSP by a factor of 5. Theory and simulation show that for larger networks, PulseSync offers an accuracy which is several orders of magnitude better than FTSP. To round off the presentation, we investigate several optimization issues, e.g. media access and local skew.
InterferenceResilient Information Exchange
"... This paper presents an efficient protocol to reliably exchange information in a singlehop radio network with unpredictable interference. The devices can access C communication channels. We model the interference with an adversary that can disrupt up to t of these channels simultaneously. We assume ..."
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Cited by 21 (7 self)
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This paper presents an efficient protocol to reliably exchange information in a singlehop radio network with unpredictable interference. The devices can access C communication channels. We model the interference with an adversary that can disrupt up to t of these channels simultaneously. We assume no shared secret keys or thirdparty infrastructure. The running time of our protocol decreases as the gap between C and t increases. Two extreme cases prove particularly interesting: The running time is linear when the number of channels C = Ω(t 2), and exponential when only C = t + 1 channels are available. We prove that exponentialtime is unavoidable in the latter case. At the core of our protocol lies a combinatorial function, of independent interest, and described for the first time in this paper: the multiselector. This function determines a sequence of device channel assignments such that every sufficiently large subset of devices is partitioned, by at least one of these assignments, onto distinct channels.