Destination directed packet switch architecture for a 30/20 GHz FDMA/TDM geostationary communication satellite network

Emphasis is on a destination directed packet switching architecture for a 30/20 GHz frequency division multiplex access/time division multiplex (FDMA/TDM) geostationary satellite communication network. Critical subsystems and problem areas are identified and addressed. Efforts have concentrated heavily on the space segment; however, the ground segment was considered concurrently to ensure cost efficiency and realistic operational constraints

Destination-directed, packet-switching architecture for 30/20-GHz FDMA/TDM geostationary communications satellite network

A destination-directed packet switching architecture for a 30/20-GHz frequency division multiple access/time division multiplexed (FDMA/TDM) geostationary satellite communications network is discussed. Critical subsystems and problem areas are identified and addressed. Efforts have concentrated heavily on the space segment; however, the ground segment has been considered concurrently to ensure cost efficiency and realistic operational constraints

Localization of nodes in wired and wireless networks

This thesis focuses on the implementation of algorithms for localization of nodes in wired and wireless networks. The thesis is organized into two papers. The first paper presents the localization algorithms based on time of arrival (TOA) and time difference of arrival (TDOA) techniques for computer networks such as the Internet by using round-trip-time (RTT) measurements obtained from known positions of the gateway nodes. The RTT values provide an approximate measure of distance between the gateway nodes and an unknown node. The least squares technique is then used to obtain an estimated position of the unknown node. The second paper presents localization of an unknown node during route setup messages in wireless ad hoc and sensor networks using a new routing protocol. A proactive multi-interface multichannel routing (MMCR) protocol, recently developed at Missouri S&T, was implemented on the Missouri S&T motes. This protocol calculates link costs based on a composite metric defined using the available end-to-end delay, energy utilization, and bandwidth, and it chooses the path that minimizes the link cost factor to effectively route the information to the required destination. Experimental results indicate enhanced performance in terms of quality of service, and implementation of this protocol requires no modification to the current IEEE 802.11 MAC protocol. Received signal strength indicator (RSSI) values are recorded from the relay nodes (gateway nodes) to the unknown node during route setup messages. The location of the unknown node is estimated using these values with some a priori profiling and the known positions of the relay nodes as inputs to the least squares technique --Abstract, page iv

Performance Model of Multichannel Deflection-Routed All-Optical Networks With Packet Injection Control

Deflection routing is a feasible approach to resolve the output contention problem in packet-switched networks when buffering of packets is not practical. In this paper, we investigate the performance of multichannel deflection-routed networks with no packet injection control, strict packet injection control, and a simple token-bucket-based packet injection control. The analytical performance models of multichannel deflection-routed networks with strict packet injection control are derived. Simulation results show that the analytical models can accurately predict the performance regardless of the network topology, number of channels, and packet injection control methods. We observed that the end-to-end throughput-delay and the packet re-transmission performance at sources can be largely improved by using simple packet injection control mechanisms such as the proposed token-bucket-based method.postprin

When Channel Bonding is Beneficial for Opportunistic Spectrum Access Networks

Transmission over multiple frequency bands combined into one logical channel speeds up data transfer for wireless networks. On the other hand, the allocation of multiple channels to a single user decreases the probability of finding a free logical channel for new connections, which may result in a network-wide throughput loss. While this relationship has been studied experimentally, especially in the WLAN configuration, little is known on how to analytically model such phenomena. With the advent of Opportunistic Spectrum Access (OSA) networks, it is even more important to understand the circumstances in which it is beneficial to bond channels occupied by primary users with dynamic duty cycle patterns. In this paper we propose an analytical framework which allows the investigation of the average channel throughput at the medium access control layer for OSA networks with channel bonding enabled. We show that channel bonding is generally beneficial, though the extent of the benefits depend on the features of the OSA network, including OSA network size and the total number of channels available for bonding. In addition, we show that performance benefits can be realized by adaptively changing the number of bonded channels depending on network conditions. Finally, we evaluate channel bonding considering physical layer constraints, i.e. throughput reduction compared to the theoretical throughput of a single virtual channel due to a transmission power limit for any bonding size.Comment: accepted to IEEE Transactions on Wireless Communication

Destination-directed, packet-switched architecture for a geostationary communications satellite network

A major goal of the Digital Systems Technology Branch at the NASA Lewis Research Center is to identify and develop critical digital components and technologies that either enable new commercial missions or significantly enhance the performance, cost efficiency, and/or reliability of existing and planned space communications systems. NASA envisions a need for low-data-rate, interactive, direct-to-the-user communications services for data, voice, facsimile, and video conferencing. The network would provide enhanced very-small-aperture terminal (VSAT) communications services and be capable of handling data rates of 64 kbps through 2.048 Mbps in 64-kbps increments. Efforts have concentrated heavily on the space segment; however, the ground segment has been considered concurrently to ensure cost efficiency and realistic operational constraints. The focus of current space segment developments is a flexible, high-throughput, fault-tolerant onboard information-switching processor (ISP) for a geostationary satellite communications network. The Digital Systems Technology Branch is investigating both circuit and packet architectures for the ISP. Destination-directed, packet-switched architectures for geostationary communications satellites are addressed