In recent years, an increasing number of devices have been developed for operation in the bands allocated by the Federal Communications Commission (FCC) for license-free operation. Given the rules governing devices in these bands, it is possible for interference created by these devices to significantly reduce the overall capacity of these bands. Two such protocols are Bluetooth and IEEE 802.11b. Several methods have been presented in the literature for managing interference between these two devices. However, these approaches are generally not practical, since they either require the purchase of specialized hardware or do not comply with the current versions of existing protocols. In this dissertation, an approach is presented that is not only backwards-compatible, but requires the algorithm to be implemented in only a small subset of the devices operating in the local environment for the coexistence algorithm to function properly. An analytical solution for this coexistence approach when applied to generic networks is presented. A method is also presented for the backwards-compatible integration of some medium access control (MAC) protocols into Bluetooth devices. A case study of the Bluetooth/IEEE 802.11b coexistence problem is presented in this dissertation, as well as a proposed coexistence mechanism, collision-based multiple access (CBMA). A form of adaptive frequency hopping (AFH) is presented in this dissertation, as well as a combined CBMA/AFH strategy. The CBMA algorithm is shown be able to significantly reduce the impact of a Bluetooth link on an IEEE 802.11b link. The AFH algorithm is shown to have comparable performance to the CBMA algorithm. A combined CBMA/AFH algorithm presented, is shown to not only have an impact on the IEEE 802.11b link that is not greater than the CBMA-only implementation, but the Bluetooth link throughput is shown to be significantly greater than either the CBMA or AFH implementation alone. / Ph. D.

The C2X Communication is of high interest to the automotive industry. Ongoing research on this topic mainly bases on the simulation of Vehicular Ad Hoc Networks. In order to estimate the necessary level of simulation details their impact on the results needs to be examined. This thesis focuses on different channel models as the freespace, shadowing, and Ricean model, along with varying parameters. For these simulations the network simulator ns-2 is extended to provide IEEE 802.11p compliance. However, the WAVE mode is not considered since it is still under development and not finally approved. Besides a more sophisticated packet error model than the existing implementation, as well as a link adaptation algorithm, is added. In this thesis several simulations examine specific details of wireless communication systems such as fairness of multiple access, interferences, throughput, and variability. Furthermore, the simulation points out some unexpected phenomena as starving nodes and saturation effects in multi hop networks. Those led to the conclusion that the IEEE 802.11 draft amendment does not solve known problems of the original IEEE 802.11 standard.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / IEEE 802.11e is an amendment of the medium-access control (MAC) layer of the standard for wireless local area networking IEEE 802.11. The goal of 802.11e is to provide 802.11 networks with Quality of Service (QoS). 802.11 has three physical layers (PHY) of practical importance: 802.11b, 802.11a, and 802.11g. 802.11a and 802.11g provide data rates between 6 and 54 Mbps, and 802.11b provides data rates of 5.5 Mbps and 11 Mbps. However these data rates are not the actual throughput. The actual throughput that a user will experience will be lower. The throughput depends on both the PHY and MAC layers. It is important to estimate what exactly is the throughput when the physical layer is 802.11a, 802.11b, or 802.11g, and the MAC layer is 802.11e. In other words, how does providing QoS change the throughput for each of the three physical layers? In this paper we provide answers to this problem. Analytic formulae are derived. The maximum achievable throughput and minimum delay involved in data transfers are determined. The obtained results have further significance for the design of high-throughput wireless protocols.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In our prior work [1] we proposed that network-centric data telemetry systems offer substantial improvements over traditional serial data telemetry systems. This paper is a follow up to that work and is also a companion to our experimentation paper [2]. In network-centric telemetry systems, there can be many infrastructure sites that form the network’s ad hoc communications paths, and there can be many fast-moving nodes, e.g., munitions, which enter the network, generate telemetry data, and exit the network. As the geographic size of such data telemetry networks grows, constraints on link margin will typically preclude a one-to-one matching of ground-based infrastructure sites to airborne, fast-moving nodes. That is, the fast-moving nodes will traverse distances that will require the mobile node to change which specific ground node it communicates with to transfer telemetry data. This paper describes an analytic model for the generic process of a fast moving node entering a wireless network and the associated handoffs of that node among ground stations as the fast mover traverses the spatial region covered by the wireless network. Our analysis and associated worst-case example demonstrate that wireless networking technology can handle the stress of rapidly managing connectivity to high-speed nodes for effective telemetry data extraction.

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / Today’s data acquisition systems are typically comprised of data collectors connected to multiplexers via serial, point-to-point links. Data flows upstream from the sensors or avionics buses to the data acquisition units, to the multiplexer and finally to the recorder or telemetry transmitter. In a networked data acquisition system, data is transported through the network “cloud”. At the core of the network “cloud” is the network switch. The switch is responsible for distributing and directing data within the network. Network switches are commonplace in the commercial realm. Many businesses today could not function without them. A network-based data acquisition system, however, places additional burdens on the network switch. As in a commercial network, the switch in a data acquisition system must be able to distribute data packets within the network. In addition, it must be able to perform in a harsh environment, occupy a minimal amount of space, operate with limited or no external cooling, be configurable, and deal with the distribution of time information. This paper describes the required features of a ruggedized network switch and the implementation challenges facing its design. As a core component of a network-based data acquisition system, an ideal switch must be capable of operating in a large number of configurations, transporting and aggregating data between data sources and data sinks, with a mixture of devices operating at rates ranging from a few thousand bits per second to several gigabits per second, over twisted pair or fiber optic links. To ensure time coherency, the switch must also facilitate a time distribution mechanism, e.g., IEEE-1588 Precision Time Protocol (PTP). The gigabit switch described here uses the PTP to implement an end-to-end clock synchronization, for distributed acquisition nodes, to within 300 nanoseconds.

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / Adding an instrumentation / telemetry system to a test vehicle has historically required an intrusive installation for wiring and powering all elements of the system from the sensor to the telemetry transmitter. In some applications there is need for a flexible and modular instrumentation and telemetry system that can be installed with minimal intrusiveness on an aircraft without the need for permanent modifications. Such an application may benefit from the use of a miniaturized, inexpensive network of wireless sensors. This network will communicate its data to a central unit installed within the aircraft. This paper describes recent efforts associated with the Advanced Subminiature Telemetry System (ASMT) Initial Test Capability Project. It discusses the challenges in developing a wireless sensor network system for use in an airborne environment. These include selection of frequencies, COTS wireless devices, batteries, system synchronization, data bandwidth calculations, and mechanical structure for external installation. The paper will also describe the wireless network architecture as well as the architecture of the wireless sensor and the central control unit.

ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California / Airborne data acquisition systems have changed very little over the years. Their growth has primarily been in the area of digital filtering and the acquisition of new avionic busses. Communication between data acquisition units operating as a system still employs Time Division Multiplexing scheme. These schemes utilize command and data busses like CAIS and PCM. Although this approach is highly efficient, it has many drawbacks. These drawbacks have resulted in rigid system architecture, system bandwidth limitations, highly specialized recorders to acquire unique avionic busses that would otherwise overwhelm the system bandwidth, and unidirectional flow of data and control. This paper describes a network centric data acquisition system that is Ethernet based. Although Ethernet is known as an asynchronous bus, the paper will describe a deterministic time distribution over the bus per IEEE-1588 that allows the use of a packet network for airborne data acquisition. The acquisition unit within the network system is defined by its MIB (Management Information Base) and operates as a data source unit. Other network components may operate as a data sink unit, such as recorders, or as a data source and sink. The role of different units in the network system will be evaluated. The paper will also describe network gateways that allow the use of traditional PCM systems with a network-based system.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / MIL-STD-1553 has served the flight community well. However, in recent years several new high-speed bus standards have emerged that outperform 1553 in various respects such as data throughput and increased address space. During this time, mission requirements - including video and audio - have become more data intensive. Although some of these busses were not initially designed for the avionics industry (such as Ethernet, FireWire, and FibreChannel), they are potentially of interest as high-speed commercial off-the-shelf (COTS) solutions for both set-up and data acquisition. These busses offer not only improved overall system performance, in terms of aggregate sampling rates, but also simplify existing data acquisition system architectures. They require fewer high-bandwidth links which can serve for both set-up and data. This paper examines some of these issues, focusing in particular on IEEE1394, better known as FireWire.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / Replacing and maintaining sensors in existing legacy systems is costly and time consuming since no information beyond voltage or current is supplied by these sensors. When a sensor is replaced or added, information for that sensor has to be incorporated by the software programmer into the main system software – a costly and time-consuming process. A method has been developed to give these old sensors the intelligence to meet the requirements of the proposed IEEE P1451.3 standard. This is accomplished with no changes to the legacy hardware and a minor, one time change to the legacy main system software.

ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / The current paradigm for data acquisition and recording systems for flight test applications does not meet today's demand for high reliability and timing performance. Such systems are better served through a network-based approach that can provide the capacity at which systems must acquire, record, process, and telemeter data. As with any complex system, this approach does have challenges. This paper describes the methods used to develop a network-centric flight test system, including simulators, IEEE 1588 time synchronization, network message protocols, and addresses the integration issues involved such as network topology and reliable latency-bounded throughput. Solutions used in overcoming these integration issues in previous system designs are also presented.