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

For synchronous point-to-point n-node networks of undirected links, it has been previously shown that, to achieve consensus in presence of up to f Byzantine faults, the following two conditions are together necessary and sufficient: (i) n ≥ 3f + 1 and (ii) network connectivity greater than 2f . The first condition, that is, n ≥ 3f + 1, is known to be necessary for directed graphs as well. On the other hand, the second condition on connectivity is not necessary for directed graphs. So far, tight necessary and sufficient condition for Byzantine consensus in directed graphs has not been developed. This paper presents tight necessary and sufficient condition for achieving Byzantine consensus in synchronous networks that can be represented as directed graphs. We provide a constructive proof of sufficiency by presenting a new Byzantine consensus algorithm for directed graphs. Further work is needed to improve the message overhead of Byzantine consensus in directed graphs.

/pdf/exact-byzantine-consensus-in-directed-graphs-2go9dd15qk.pdf

Exact Byzantine Consensus in Directed Graphs

For mobile users who move frequently but receive relatively rare calls, a forwarding scheme has been shown to outperform the normal IS-41 location management scheme. But the forwarding scheme is more vulnerable to failure of intermediate Visitor Location Registers (VLRs) than the IS-41 scheme. We propose two simple variations to the forwarding scheme to address the fault tolerance weakness. One is based on the idea of maintaining two paths from the home location server to the last VLR. The second scheme is based on the knowledge of the neighbors of the faulty VLR. We evaluate and compare the performance of these location management schemes.

/pdf/tolerating-visitor-location-register-failures-in-mobile-2avlx8stje.pdf

Tolerating Visitor Location Register failures in mobile environments

This paper proposes a routing scheme that exploits multiple heterogeneous wireless interfaces: a primary 802.11a interface and a secondary 802.11b (or 802.11) interface. In normal conditions, a TCP flow uses a primary path over the 802.11a interface discovered by a reactive routing protocol. But in presence of route breakage due to node mobility, it resorts to its backup path over the 802.11b interface which is already maintained by a proactive routing protocol and is being used for delivery of other packets. The secondary interface exhibits different property than the primary interface (i.e., slower rate but larger transmission range), which helps keep TCP flows alive and preserve the TCP window size, thereby making them more robust to route breakage induced by mobility. ns-2 implementation and experiments reveal several potential benefits of the proposed routing scheme.

/pdf/routing-exploiting-multiple-heterogeneous-wireless-fuk6g4k2w0.pdf

Routing Exploiting Multiple Heterogeneous Wireless Interfaces: A TCP Performance Study

This paper addresses the multi-agent optimization problem in which the agents try to collaboratively minimize \(\frac{1}{k}\sum _{i=1}^k h_i\) for a given choice of k input functions \(h_1, \ldots , h_k\). This problem finds its application in distributed machine learning, where the data set is too large to be processed and stored by a single machine. It has been shown that when the networked agents may suffer Byzantine faults, it is impossible to minimize \(\frac{1}{k}\sum _{i=1}^k h_i\) with no redundancy in the local cost functions.

Robust Multi-agent Optimization: Coping with Byzantine Agents with Input Redundancy

We present a distributed solution to optimizing a convex function composed of several non-convex functions. Each non-convex function is privately stored with an agent while the agents communicate with neighbors to form a network. We show that coupled consensus and projected gradient descent algorithm proposed in [1] can optimize convex sum of non-convex functions under an additional assumption on gradient Lipschitzness. We further discuss the applications of this analysis in improving privacy in distributed optimization.

Nitin H. Vaidya

Papers

Exact Byzantine Consensus in Directed Graphs

Tolerating Visitor Location Register failures in mobile environments

Routing Exploiting Multiple Heterogeneous Wireless Interfaces: A TCP Performance Study

Robust Multi-agent Optimization: Coping with Byzantine Agents with Input Redundancy

Distributed Optimization of Convex Sum of Non-Convex Functions