Structuring Unreliable Radio Networks

In this paper we study the problem of building a connected dominating set with constant degree (CCDS) in the dual graph radio network model [4,9,10]. This model includes two types of links: reliable, which always deliver messages, and unreliable, which sometimes fail to deliver messages. Real networks compensate for this differing quality by deploying low-layer detection protocols to filter unreliable from reliable links. With this in mind, we begin by presenting an algorithm that solves the CCDS problem in the dual graph model under the assumption that every process u is provided a local link detector set consisting of every neighbor connected to u by a reliable link. The algorithm solves the CCDS problem in O(Δ\log[superscript 2] n/b + log[superscript 3] n) rounds, with high probability, where Δ is the maximum degree in the reliable link graph, n is the network size, and b is an upper bound in bits on the message size. The algorithm works by first building a Maximal Independent Set (MIS) in log[superscript 3] n time, and then leveraging the local topology knowledge to efficiently connect nearby MIS processes. A natural follow up question is whether the link detector must be perfectly reliable to solve the CCDS problem. With this in mind, we first describe an algorithm that builds a CCDS in O(Δpolylog(n)) time under the assumption of O(1) unreliable links included in each link detector set. We then prove this algorithm to be (almost) tight by showing that the possible inclusion of only a single unreliable link in each process's local link detector set is sufficient to require Ω(Δ) rounds to solve the CCDS problem, regardless of message size. We conclude by discussing how to apply our algorithm in the setting where the topology of reliable and unreliable links can change over time.Simons Foundation. (Postdoctoral Fellows Program)United States. Air Force Office of Scientific Research (Award FA9550-08-1-0159)National Science Foundation (U.S.) (Award CCF-0937274)National Science Foundation (U.S.) (Award CCF-0726514)National Science Foundation (U.S.) (Purdue University) (Science and Technology Center Award 0939370-CCF

Structuring Unreliable Radio Networks

In this paper we study the problem of building a connected dominating set with constant degree (CCDS) in the dual graph radio network model. This model includes two types of links: reliable links, which always deliver messages, and unreliable links, which sometimes fail to deliver messages. Real networks compensate for this differing quality by deploying low-layer detection protocols to filter unreliable from reliable links. With this in mind, we begin by presenting an algorithm that solves the CCDS problem in the dual graph model under the assumption that every process u is provided with a local "link detector set" consisting of every neighbor connected to u by a reliable link. The algorithm solves the CCDS problem in O((Delta log2(n)/b) + log3(n)) rounds, with high probability, where Delta is the maximum degree in the reliable link graph, n is the network size, and b is an upper bound in bits on the message size. The algorithm works by first building a Maximal Independent Set (MIS) in log3(n) time, and then leveraging the local topology knowledge to efficiently connect nearby MIS processes. A natural follow up question is whether the link detector must be perfectly reliable to solve the CCDS problem. To answer this question, we first describe an algorithm that builds a CCDS in O(Delta polylog(n)) time under the assumption of O(1) unreliable links included in each link detector set. We then prove this algorithm to be (almost) tight by showing that the possible inclusion of only a single unreliable link in each process's local link detector set is sufficient to require Omega(Delta) rounds to solve the CCDS problem, regardless of message size. We conclude by discussing how to apply our algorithm in the setting where the topology of reliable and unreliable links can change over time

Traffic-adaptive, flow-specific medium access for wireless networks

In this report, we formally introduce the novel concept of traffic-adaptive, flow-specific medium access control and show that it outperforms contention, non-contention and hybrid medium access schemes. A traffic-adaptive, flow-specific mechanism is proposed that utilizes flow-specific queue size statistics to select between medium access modes. A general model for traffic adaptive, flow-specific medium access control is developed and it is shown that hybrid medium access as well as traditional contention-based and non-contention schemes can be seen as special cases of the more general flow-specific access. The two flow, two-mode case of the general model is developed in detail and it is shown analytically that this queue-based implementation of traffic-adaptive, flow-specific medium access outperforms contention, non-contention, and hybrid approaches. The proposed traffic-adaptive, flow-specific mechanism is applied to Cooperative Wireless Sensor Network Medium Access Control (CWS-MAC) a flow-specific medium access protocol. Performance is evaluated is evaluated and compared to the traditional medium access approaches. Both analytical and simulation results are provided including the development of throughput and delay expressions for slotted ALOHA with periodic server vacations.Approved for public release; distribution is unlimited

Distributed algorithms for coloring and domination in wireless ad hoc networks

Abstract. We present fast distributed algorithms for coloring and (connected) dominating set construction in wireless ad hoc networks. We present our algorithms in the context of Unit Disk Graphs which are known to realistically model wireless networks. Our distributed algorithms take into account the loss of messages due to contention from simultaneous interfering transmissions in the wireless medium. We present randomized distributed algorithms for (conflict-free) Distance-2 coloring, dominating set construction, and connected dominating set construction in Unit Disk Graphs. The coloring algorithm has a time complexity of O( ∆ log 2 n) and is guaranteed to use at most O(1) times the number of colors required by the optimal algorithm. We present two distributed algorithms for constructing the (connected) dominating set; the former runs in time O( ∆ log 2 n) and the latter runs in time O(log 2 n). The two algorithms differ in the amount of local topology information available to the network nodes. Our algorithms are geared at constructing Well Connected Dominating Sets (WCDS) which have certain powerful and useful structural properties such as low size, low stretch and low degree. In this work, we also explore the rich connections between WCDS and routing in ad hoc networks. Specifically, we combine the properties of WCDS with other ideas to obtain the following interesting applications: – An online distributed algorithm for collision-free, low latency, low redundancy and high throughput broadcasting. – Distributed capacity preserving backbones for unicast routing and scheduling.