Abstract—We describe a distributed position-based network protocol optimized for minimum energy consumption in mobile wireless networks that support peer-to-peer communications. Given any number of randomly deployed nodes over an area, we illustrate that a simple local optimization scheme executed at each node guarantees strong connectivity of the entire network and attains the global minimum energy solution for stationary networks. Due to its localized nature, this protocol proves to be self-reconfiguring and stays close to the minimum energy solution when applied to mobile networks. Simulation results are used to verify the performance of the protocol. Index Terms — Distributed algorithms, energy management, graph theory, mobile communication, network fault tolerance, networks, packet radio, portable radio communication, power measurement, protocols, radio repeaters. I.

The communication protocols used in wireless ad hoc networks today have been designed to support reliable communication between senders and receivers that compete with other sender-receiver sets for the use of the shared bandwidth. This competition-driven approach prevents wireless ad hoc networks from scaling with the number of nodes. We introduce a collaboration-driven approach to the sharing of the available bandwidth in wireless ad hoc networks, which we call opportunistic cooperation. This scheme is based on the integration of multiuser detection and position-location information with frequency and code division in mobile ad hoc networks (MANETs). Transmissions are divided in frequency and codes according to nodal locations, and successive interference cancellation (SIC) is used at receivers to allow them to decode and use all transmissions from strong interfering sources. We show that both the link's Shannon capacity and the per source-destination throughput scale like (upper-bound) and (lower-bound), for nodes in the network, a path loss parameter 3600 .

We introduce a collaboration-driven approach to the sharing of the available bandwidth in wireless ad hoc networks, which we call many-to-many cooperation, that allows concurrent many-to-many communication. This scheme is based on the integration of multi-user detection and position-location information with frequency and code division in mobile ad hoc networks (MANETs). Transmissions are divided in frequency and codes according to nodal locations, and successive interference cancellation (SIC) is used at receivers to allow them to decode and use all transmissions from strong interfering sources. Consequently, the interference is divided into constructive interference (COI) and destructive interference (DEI). We show that, if each node is allowed to expand its bandwidth, both the link’s Shannon capacity and the per source-destination throughput scale like O(n α 2) (upperbound) and Ω[f(n)] (lower-bound), for n nodes in the network, a path loss parameter α>2, and1 ≤ f(n) <n α 2. Many-to-many cooperation allows multi-copy relaying of the same packet, which reduces the packet delivery delay compared to single-copy relaying without any penalty in capacity.

Internet-based mobile ad hoc network (IMANET) is an emerging technique that combines a mobile ad hoc network (MANET) and the Internet to provide universal information accessibility. Although caching frequently accessed data items in mobile terminals (MTs) improves the communication performance in an IMANET, it brings a critical design issue when data updates. In this paper, we analyze several push and pull-based cache invalidation strategies for IMANETS. Aglobal positioning system (GPS) based connectivity estimation (GPSCE) scheme is first proposed to assess the connectivity of an MT for supporting cache invalidation mechanisms. Then, we propose a pull-based approach, called aggregate cache based on demand (ACOD) scheme that uses an efficient search algorithm for finding the queried data items. In addition, we modify two push-based cache invalidation strategies, proposed for cellular networks, to work in IMA-NETS. They are called modified timestamp (MTS) scheme and MTS with updated invalidation report (MTS + UIR) scheme, respectively. We compare the performance of all these schemes as a function of query interval, cache update interval, and cache size through extensive simulation. Simulation results indicate that the ACOD scheme provides high throughput, low query latency, and low communication overhead, and thus, is a viable approach for implementation in IMANETS.

We introduce a collaboration-driven approach to the sharing of the available bandwidth in wireless ad hoc networks, which we call many-to-many communication, that allows concurrent multi-packet transmissions (MPTs) and multi-packet receptions (MPRs). Many-to-many communication also permits one-time multi-copy relaying of the same packet, which reduces the packet delivery delay compared to single-copy relaying without any penalty in capacity. Our scheme is based on the integration of multi-user detection and position-location information with frequency and code division in mobile ad hoc networks (MANETs). Transmissions are divided in frequency and codes according to node locations, and successive interference cancellation (SIC) is used at receivers to allow them to decode and use all transmissions from strong interfering sources. Consequently, the interference is divided into constructive interference (COI) and destructive interference (DEI). We show that, if each node is allowed to expand its bandwidth, both the link’s Shannon capacity and the per source-destination throughput scale like O(n α 2) (upper-bound) and Ω[f(n)] (lower-bound), for n nodes in the network, a path loss parameter α> 2, and 1≤f(n)<n α

in 2002. His research currently focuses on the performance analysis and validation of Doppler-aided GPS carrier-tracking loops. He is also looking into the solutions to the problem of GPS/WAAS performance degradation caused by ionospheric scintillation. Jiwon Seo is a Ph.D. candidate in Aeronautics and

The fundamental tasks of a Global Positioning System (GPS) receiver are signal tracking and noise rejection. The essence of this dissertation is investigating the balance between the aforementioned objectives; taking advantage of the noise immunity property of external sensors, and designing novel integrated tracking architectures to advance the performance of a GPS receiver under strong interference conditions. Speci cally, the problem of interest is resolving the interference due to ionospheric scintillation on the GPS receiver used in aviation navigation. Using GPS for landing aircraft in equatorial regions is more di cult than in other regions because ionospheric scintillation is prevalent. Ionospheric scintillation causes amplitude fades of 20 dB or more, and an increase in the phase jitter. This research evaluates techniques to enhance a GPS receiver's ability to overcome ionospheric scintillation. To validate the designed GPS receiver, a GPS channel model for aircraft landing in equatorial regions is built based on the use of a high delity GPS constellation simulator, a clock emulator, and real GPS data from the equator that contains an abundance of ionospheric scintillation.