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

Limited channel spectrum and rapid growth in the number of wireless devices make the issue of efficient channel resource utilization in wireless networks critical. Additionally, with the growth of real-time applications, wireless networks that support quality of service (QoS) have also drawn a lot of attention. This dissertation focuses on the design of scheduling algorithms to improve channel utilization and to support differentiated service in wireless multihop networks. To improve the channel utilization, we discuss approaches along both the temporal dimension and the spatial dimension. In the temporal dimension, when two nodes are competing for the channel, their channel accesses are separated in time to ensure successful transmissions. As an improvement over the conventional approaches, we propose the application of "pipelining" techniques to medium access control (MAC) protocol design. Pipelining, which allows the execution of multiple tasks to overlap in time, can help to hide MAC overhead by overlapping it with useful packet transmissions, leading to improved channel utilization. In the spatial dimension, due to radio signal attenuation, two competing nodes separated in space can be allowed to transmit at the same time, using transmission rates suitable for their link qualities. Exploiting the fact that nodes in a wireless network compete for "space" to schedule their packet transmissions, we propose a new approach that adapts the "space" occupied by the transmissions, named "spatial backoff," to improve the channel utilization. 
In order to support differentiated service, the medium access control protocol must provide certain mechanisms to incorporate differentiated priority scheduling, such that higher priority traffic can be transmitted in preference to lower priority traffic. The "location dependent channel contention" and "hidden terminals" make priority scheduling significantly different from that in wireless LANs. In this dissertation, we also discuss issues related to priority scheduling in multihop networks. A priority scheduling protocol is proposed to ensure channel access privilege of high priority packets and to improve the channel utilization when high priority packets are not present.

Efficient packet scheduling in wireless multihop networks

This paper presents a technique to provide seamless communication in mobile wireless networks. The motivation behind this study is to find a cost effective solution for minimizing the impact of active hand-offs (hand-offs during an active connection) on connection throughput. Existing solutions either provide total guarantee for seamless communication, incurring heavy network bandwidth usage (multicast based approach), or do not provide any guarantee for seamless communication (unicast based approach). Some other solutions are tuned to give good performance for specific protocols (e.g., fast-retransmit approach). This paper proposes a novel staggered multicast approach which provides a probablistic guarantee for seamless communication independent of the communication protocol used. We present experimental results of performance improvements achieved by our scheme, for data transfer using TCP over a wireless network in the presence of active handoffs. The conclusions however, are generic in that they apply to protocols other than TCP.

Providing seamless communication in mobile wireless networks

Traffic analysis poses a serious threat to communication security, especially in wireless networks. Encryption may be used to hide message contents, whereas traffic padding may be used to hide the traffic pattern. This paper deals with the issue of preventing traffic analysis by inserting dummy (or padding) traffic to hide the real traffic pattern. The observable traffic pattern, after dummy traffic has been inserted, is referred to as a cover mode. Since the dummy traffic incurs an overhead, it is important to minimize dummy traffic while achieving the desired security objective. In this paper, we attempt to develop a suitable cover mode with the objective of minimizing energy of preventing traffic analysis by inserting dummy (or padding) traffic to hide the real traffic pattern. The observable traffic pattern, after dummy traffic has been inserted, is referred to as a cover mode. Since the dummy traffic incurs an overhead, it is important to minimize dummy traffic while achieving the desired security objective. In this paper, we attempt to develop a suitable cover mode with the objective of minimizing energy consumption -- the nodes in wireless ad hoc networks typically have limited battery supply, therefore, it is important to minimize the energy consumption. We propose different methods for implementing the cover mode, and evaluate the impact of these techniques on system lifetime and on energy consumption per unit of real traffic transmitted in the network.

Power-Aware Traffic Cover Mode to Prevent Traffic Analysis in Wireless Ad Hoc Networks

This paper studies how the capacity of a static multichannel network scales as the number of nodes, n, increases. Gupta and Kumar have determined the capacity of single channel networks, and those bounds are applicable to multichannel networks as well, provided each node in the network has a dedicated interface per channel. In this work, we establish the capacity of general multichannel networks wherein the number of interfaces, m, may be smaller than the number of channels, c. We show that the capacity of multichannel networks exhibits different bounds that are dependent on the ratio between c and m. When the number of interfaces per node is smaller than the number of channels, there is a degradation in the network capacity in many scenarios. However, one important exception is a random network with up to O(logn) channels, wherein the network capacity remains at the Gupta and Kumar bound of �

/pdf/capacity-of-multichannel-wireless-networks-impact-of-21v41mucoa.pdf

Nitin H. Vaidya

Papers

Efficient packet scheduling in wireless multihop networks

Providing seamless communication in mobile wireless networks

Power-Aware Traffic Cover Mode to Prevent Traffic Analysis in Wireless Ad Hoc Networks

Capacity of Multichannel Wireless Networks: Impact of Channels, Interfaces, and Interface Switching Delay ∗

Heterogeneous data networks: congestion or corruption?