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

In this article, we outline a research agenda for developing protocols and algorithms for densely populated RFID based systems covering a wide geographic area. This will need multiple readers collaborating to read RFID tag data. We consider cases where the tag data is used for identification, or for sensing environmental parameters. We address performance issues related to 'accuracy' and 'efficiency' in such systems by exploiting 'diversity' and 'redundancy'. We discuss how tag multiplicity can be used to improve accuracy. In a similar fashion, we explore how reader diversity, achieved by using multiple readers with potentially partially overlapping coverage areas, can be exploited to improve accuracy and efficiency. Finally, we show how multiple antennas in a reader can be used to improve accuracy and access rates by utilizing antenna diversity. RFID tag/sensor data can be highly redundant for the purpose of answering a higher level query. For example, often the higher level query needs to compute a statistic or a function on the sensory data obtained by the RFID sensors, and does not need all the individual sensor readings. We outline the need for efficient tag-to-reader communication, and reader-to-reader coordination to effectively compute such functions with low overhead.

/pdf/rfid-based-networks-exploiting-diversity-and-redundancy-13nukdd9ui.pdf

RFID-based networks: exploiting diversity and redundancy

Long-running applications are often subject to failures. Failures can result in significant loss of computation, Therefore, it is necessary to use a failure recovery scheme to minimize performance overhead in the presence of failures. In this paper, we argue that it is often advantageous to use "two-level" recovery schemes. A two-level recovery scheme tolerates the more probable failures with low performance overhead, while the less probable failures may possibly incur a higher overhead. By minimizing overhead for the more frequently occurring failure scenarios, the two-level approach can achieve lower performance overhead (on average) as compared to existing recovery schemes. The paper describes two two-level recovery schemes. Performance analysis using a Markov chain shows that, in practice, a two-level scheme can perform better than its "one-level" counterpart. While the conclusions of this paper are intuitive, the work on design of appropriate recovery schemes is lacking. The objective of this paper is to motivate research into recovery schemes that can provide multiple levels of fault tolerance and achieve better performance than existing recovery schemes. The paper presents an analytical approach for evaluating performance of two-level schemes and shows that such schemes are hard to optimize analytically.

A case for two-level recovery schemes

This work addresses Byzantine vector consensus (BVC), wherein the input at each process is a d-dimensional vector of reals, and each process is expected to decide on a decision vector that is in the convex hull of the input vectors at the fault-free processes [3, 8]. The input vector at each process may also be viewed as a point in the d-dimensional Euclidean space R^d, where d > 0 is a finite integer. Recent work [3, 8] has addressed Byzantine vector consensus in systems that can be modeled by a complete graph. This paper considers Byzantine vector consensus in incomplete graphs. In particular, we address a particular class of iterative algorithms in incomplete graphs, and prove a necessary condition, and a sufficient condition, for the graphs to be able to solve the vector consensus problem iteratively. We present an iterative Byzantine vector consensus algorithm, and prove it correct under the sufficient condition. The necessary condition presented in this paper for vector consensus does not match with the sufficient condition for d > 1; thus, a weaker condition may potentially suffice for Byzantine vector consensus.

Iterative Byzantine Vector Consensus in Incomplete Graphs

Wireless local-area networks are becoming increasingly popular. This is due, in part, to the recent availability of devices capable of communicating at data rates approaching that of conventional wired networks. These high rates are made possible through new modulation and coding techniques that dramatically increase bandwidth efficiency. However, maintaining reliable communication at higher data rates requires more signal power. Consequently, wireless devices often support multiple data rates, providing the user the ability to choose the rate that best suits their application. Alternatively, an automatic rate adaption mechanism may be used. Rate adaption is the process of automatically selecting the rate that gives the optimum throughput for the channel conditions. Although rate adaption mechanisms for cellular wireless networks have been studied at length, few have been proposed for wireless local-area networks. This paper presents one such mechanism: a rate adaptive MAC protocol based on the RTS/CTS collision avoidance handshake, called the Receiver-Based AutoRate (RBAR) protocol. The protocol is unique in that the rate adaption mechanism is located on the receiver, instead of the sender. Simulation results of an implementation of RBAR into IEEE 802.11 show that this arrangement performs well, in comparison to an existing protocol.

A Rate-Adaptive MAC Protocol for Wireless Networks

Location management is an important problem in distributed mobile computing. Location management consists of location updates, searches and search-updates. An update occurs when a mobile host changes location. A search occurs when a mobile host needs to be located. A search-update occurs after a successful search. Various strategies can be designed for search, update and search-update. Static location management uses one combination of search, update and search-update strategies throughout the execution. Simulations were carried out to evaluate the performance of different static strategies for various communication and mobility patterns. Simulation results indicate that performing search-updates significantly reduces the message overhead of location management. >

/pdf/location-management-in-distributed-mobile-environments-7t8gsq5teh.pdf

Nitin H. Vaidya

Papers

RFID-based networks: exploiting diversity and redundancy

A case for two-level recovery schemes

Iterative Byzantine Vector Consensus in Incomplete Graphs

A Rate-Adaptive MAC Protocol for Wireless Networks

Location management in distributed mobile environments