We present Greedy Perimeter Stateless Routing (GPSR), a novel routing protocol for wireless datagram networks that uses the positions of routers and a packet's destination to make packet forwarding decisions. GPSR makes greedy forwarding decisions using only information about a router's immediate neighbors in the network topology. When a packet reaches a region where greedy forwarding is impossible, the algorithm recovers by routing around the perimeter of the region. By keeping state only about the local topology, GPSR scales better in per-router state than shortest-path and ad-hoc routing protocols as the number of network destinations increases. Under mobility's frequent topology changes, GPSR can use local topology information to find correct new routes quickly. We describe the GPSR protocol, and use extensive simulation of mobile wireless networks to compare its performance with that of Dynamic Source Routing. Our simulations demonstrate GPSR's scalability on densely deployed wireless networks.

/pdf/gpsr-greedy-perimeter-stateless-routing-for-wireless-59gz21qf8y.pdf

GPSR: greedy perimeter stateless routing for wireless networks

https://www.cs.montana.edu/courses/csci566/Ref/CR-Survey.pdf

NeXt generation/dynamic spectrum access/cognitive radio wireless networks: a survey

Advances in processor, memory and radio technology will enable small and cheap nodes capable of sensing, communication and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed diffusion paradigm for such coordination. Directed diffusion is datacentric in that all communication is for named data. All nodes in a directed diffusion-based network are application-aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network. We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network.

/pdf/directed-diffusion-a-scalable-and-robust-communication-4tsx5vxsas.pdf

Directed diffusion: a scalable and robust communication paradigm for sensor networks

"A Survey of Mobility Models for Ad Hoc Network Research," Wireless Comm. & Mobile Computing (WCMC) : Special issue on Mobile Ad Hoc Networking : Research

In the performance evaluation of a protocol for an ad hoc network, the protocol should be tested under realistic conditions including, but not limited to, a sensible transmission range, limited buffer space for the storage of messages, representative data traffic models, and realistic movements of the mobile users (i.e., a mobility model). This paper is a survey of mobility models that are used in the simulations of ad hoc networks. We describe several mobility models that represent mobile nodes whose movements are independent of each other (i.e., entity mobility models) and several mobility models that represent mobile nodes whose movements are dependent on each other (i.e., group mobility models). The goal of this paper is to present a number of mobility models in order to offer researchers more informed choices when they are deciding upon a mobility model to use in their performance evaluations. Lastly, we present simulation results that illustrate the importance of choosing a mobility model in the simulation of an ad hoc network protocol. Specifically, we illustrate how the performance results of an ad hoc network protocol drastically change as a result of changing the mobility model simulated.

/pdf/a-survey-of-mobility-models-for-ad-hoc-network-research-ygkxat400x.pdf

A survey of mobility models for ad hoc network research

Consider a point-to-point message-passing network. We are interested in the asynchronous crashtolerant consensus problem in incomplete networks. We study the feasibility and efficiency of approximate consensus under different restrictions on topology knowledge and the relay depth, i.e., the maximum number of hops any message can be relayed. These two constraints are common in large-scale networks, and are used to avoid memory overload and network congestion respectively. Specifically, for positive integer values k and k′, we consider that each node knows all its neighbors of at most k-hop distance (k-hop topology knowledge), and the relay depth is k′. We consider both directed and undirected graphs. More concretely, we answer the following question in asynchronous systems: What is a tight condition on the underlying communication graphs for achieving approximate consensus if each node has only a k-hop topology knowledge and relay depth k′? To prove that the necessary conditions presented in the paper are also sufficient, we have developed algorithms that achieve consensus in graphs satisfying those conditions: The first class of algorithms requires k-hop topology knowledge and relay depth k. Unlike prior algorithms, these algorithms do not flood the network, and each node does not need the full topology knowledge. We show how the convergence time and the message complexity of those algorithms is affected by k, providing the respective upper bounds. The second set of algorithms requires only one-hop neighborhood knowledge, i.e., immediate incoming and outgoing neighbors, but needs to flood the network (i.e., relay depth is n, where n is the number of nodes). One result that may be of independent interest is a topology discovery mechanism to learn and “estimate” the topology in asynchronous directed networks with crash faults. 2012 ACM Subject Classification Computer systems organization → Fault-tolerant network topologies

Effects of Topology Knowledge and Relay Depth on Asynchronous Appoximate Consensus.

Design diversity has emerged as a powerful mechanism for incorporating software fault tolerance in ultra-reliable systems. In this paper we study the trade-offs available during the development process of fault-tolerant software employing the recovery block approach [2]. When the total available testing time is bounded, our analysis determines how appropriately to allocate testing time to the various redundant modules that make up the fault tolerant system so as to maximise its reliability. This requires a study of the interactions between the various modules in the software system. For example error coverage and the false alarm probability of acceptance test in the recovery block scheme may be interrelated and it may not be possible to simultaneously improve both. Hence there exists a trade-off between acceptance test coverage and false alarm probability. The impact of such trade-offs on system reliability is also studied.

Trade-offs in developing fault tolerant software

IEEE 802.11 DCF is the MAC protocol currently used in wireless LANs. 802.11 DCF is inefficient due to two types of overhead; channel idle time and collision time. This paper presents the design and performance evaluation of an efficient MAC protocol for wireless networks, called Token-DCF. Token-DCF decreases both idle time and collision time. In Token-DCF, each station keeps track of neighboring links' queue length by overhearing of transmitted packets on the wireless medium. The result is then used to assign privileges to the network stations. A privileged station does not follow the backoff mechanism and transmits immediately after the channel is sensed idle. Our simulation results show that Token-DCF can significantly improve channel utilization, system throughput and channel access delay over 802.11 DCF.

Token-DCF: An Opportunistic MAC protocol for Wireless Networks

Summary form only given. Widespread proliferation of wireless RF technology has brought the possibility of infrastructureless networking to the forefront. Infrastructureless networks are often referred to as wireless ad hoc networks and they include sensor networks as an important subclass. Dependability issues such as security, reliability, availability, and quality of service are complicated by the wireless and infrastructureless environment. Reliability and availability solutions must account for the varying characteristics of a wireless channel, which is subject to interference, fading, and multipath effects, among other problems. The presence of mobile nodes in many of these settings complicates even further the dependability issues. To date, no conference or workshop has specifically addressed dependability-related issues for ad hoc and sensor networks. One of the goals of this workshop is to bring together researchers to focus exclusively on this important topic, to outline its specific and unique research challenges, and to identify some of the most promising candidate solution methods and techniques to address those challenges. A second, and equally important, goal is to promote synergy between the networking and dependability communities on this topic of mutual concern. DIWANS includes invited talks from several prominent researchers in the field, and peer-reviewed papers on a variety of relevant topics. Most important, however, are the interactions among a diverse set of researchers, working at all network layers and interested in a wide range of problems, from the most fundamental to the most applied.

DIWANS: workshop on dependability issues in wireless ad hoc networks and sensor networks

This paper explores an old problem, {\em Byzantine fault-tolerant Broadcast} (BB), under a new model, {\em selective broadcast model}. The new model "interpolates" between the two traditional models in the literature. In particular, it allows fault-free nodes to exploit the benefits of a broadcast channel (a feature from reliable broadcast model) and allows faulty nodes to send mismatching messages to different neighbors (a feature from point-to-point model) simultaneously. The {\em selective broadcast} model is motivated by the potential for {\em directional} transmissions on a wireless channel. 
We provide a collection of results for a single-hop wireless network under the new model. First, we present an algorithm for {\em Multi-Valued} BB that is order-optimal in bit complexity. Then, we provide an algorithm that is designed to achieve BB efficiently in terms of message complexity. Third, we determine some lower bounds on both bit and message complexities of BB problems in the {\em selective broadcast model}. Finally, we present a conjecture on an "exact" lower bound on the bit complexity of BB under the {\em selective broadcast} model.

/pdf/byzantine-broadcast-under-a-selective-broadcast-model-for-1g16rhfxlc.pdf

Nitin H. Vaidya

Papers

Effects of Topology Knowledge and Relay Depth on Asynchronous Appoximate Consensus.

Trade-offs in developing fault tolerant software

Token-DCF: An Opportunistic MAC protocol for Wireless Networks

DIWANS: workshop on dependability issues in wireless ad hoc networks and sensor networks

Byzantine Broadcast Under a Selective Broadcast Model for Single-hop Wireless Networks