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

This technical report considers the problem of providing a geocast service, which is useful for sending messages to everyone in a specified geographical region, in mobile ad hoc networks. In the report, a novel geocasting algorithm combining unicasting and flooding is proposed for an efficient geocast packet delivery. TORA (unicast) routing protocol is first modified to be able to perform anycasting service. Our geocasting algorithm is then obtained using a small variation on the anycasting protocol. The proposed protocol, named "GeoTORA", also incorporates flooding, but flooding is limited to nodes within a small region. This integration of TORA and flooding can significantly reduce the overhead of geocast delivery, while maintaining reasonably high accuracy.

Anycasting and Geocasting in Mobile Ad Hoc Networks

We present a dynamic spatial backoff method to resolve channel contention in wireless ad-hoc networks. We argue that each node should adjust its receiver sensitivity level according to the mean channel gain of its particular transmitter-receiver link, in order to see the full benefit of spatial backoff and improve the throughput. We designed a distributed algorithm that adjusts each transmitters carrier sense threshold and transmission rate dynamically based on local information and limited receiver feedback, for wireless channels that have small-scale multipath fading. We evaluated the algorithm using different topologies, under various fading conditions. Results show that our algorithm is able to achieve aggregate throughput near or better than the maximum achievable by the static scheme, without a priori knowledge of the network topology or fading condition.

/pdf/dynamic-spatial-backoff-in-fading-environments-1lsh2tqfzl.pdf

Dynamic spatial backoff in fading environments

The IEC 61850 protocol suite provides significant benefits in electrical substation design and enables formal validation of complex device configurations to ensure that design objectives are met. One important benefit is the potential for protective relays to react in a collaborative fashion to an observed fault current. Modern relays are networked cyberphysical devices with embedded systems, capable of sophisticated protection schemes that are not possible on legacy overcurrent relays. However, they may be subject to error or cyber attack. Herein, we introduce the CODEF (Collaborative Defense) project examining distributed substation protection. Under CODEF, we derive algorithms for distributed protection schemes based on distributed agreement. By leveraging Kirchhoff’s laws, we establish that certain fast agreement protocols have important equivalences to linear coding and error correction theory. In parallel, we describe a cyber-physical simulation environment in which these algorithms are being validated with respect to the strict time constraints of substation protection.

/pdf/design-and-simulation-of-fast-substation-protection-in-iec-4eva5orfoa.pdf

Design and simulation of fast substation protection in IEC 61850 environments

Practical algorithms for determining causality by assigning timestamps to events have focused on online algorithms, where a permanent timestamp is assigned to an event as soon as it is created. We address the problem of reducing size of the timestamp by utilizing the underlying topology (which is often not fully connected since not all processes talk to each other) and deferring the assignment of a timestamp to an event for a suitably chosen period of time after the event occurs. Specifically, we focus on inline timestamps, which are a generalization of offline timestamps that are assigned after the computation terminates. We show that for a graph with vertex cover VC, it is possible to assign inline timestamps which contains only 2|VC|+2 elements. By contrast, if online timestamps are desired, then even for a star network, vector timestamp of length n (for the case of integer elements) or n-1 (for the case of real-valued elements) is required. Moreover, in addition to being efficient, the inline timestamps developed can be used to solve typical problems such as predicate detection, replay, recovery that are solved with vector clocks.

https://dl.acm.org/doi/pdf/10.1145/3087801.3087818

Effectiveness of Delaying Timestamp Computation

: The issue of transport capacity of a randomly deployed wireless network under random (c, f) channel assignment was considered by us in [1] We showed in [1] that when the number of available channels is c = O(log n), and each node has a single interface assigned a random f subset of channels, the capacity is Omega(W x square root of f/cn log n) and O(W x square root of Prnd/n log n), and conjectured that optimal capacity was Theta(W x square root of Prnd/N log n) We now present a lower bound construction that yields capacity Omega(W x square root of Prnd/n log n) whenever f > 10(1 + log 192/5 + log c/f) Thus for values of c and f that satisfy f > 10(1 + log 192/5 + log c/f), the optimal capacity under random (c,f) assignment is proved to be Theta(W x square root of Prnd/n log n) n log n ) We conjecture that this would be the case for all 2 </= f </= c (for any given c= O(log n)

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA495206&Location=U2&doc=GetTRDoc.pdf

Nitin H. Vaidya

Papers

Anycasting and Geocasting in Mobile Ad Hoc Networks

Dynamic spatial backoff in fading environments

Design and simulation of fast substation protection in IEC 61850 environments

Effectiveness of Delaying Timestamp Computation

Capacity of Multi-Channel Wireless Networks with Random Channel Assignment: A Tight Bound