International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper addresses the physical and MAC layer performance of the IEEE 802.11b wireless local area networking (WLAN) standard in range-extended outdoor applications for high speed network platforms. Physical layer performance is quantified by bit error rate (BER) and packet error rate (PER) vs. range performance as well as acquisition and tracking performance considering Doppler effects caused by such high-speed platforms. This performance assessment is ascertained through the use of modeling and simulation and hardware-in-the-loop testing.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / The US Army’s Yuma Proving Ground (YPG) uses a wireless local area network (WLAN) to gather test data. It is desired to extend this WLAN to support tests of gun-launched munitions where miniature and rugged data acquisition hardware will be required. The Two Way Robust Acquisition of Data (2-RAD) program has been initiated under the Central Test and Evaluation Investment Program (CTEIP) to develop a process to expand the use of WLAN technology, which is now primarily used at YPG for internal ballistic test data acquisition.

In general, rural areas in Africa are seen as unprofitable by operators and hence these areas do not benefit from typical wired Internet access. Due to the cost involved, only a small number of people in Africa benefit from the Internet. On the other hand, the Global System for Mobile communications (GSM) has thoroughly penetrated Africa and in many cases unutilized capacity exists in rural areas. Since the cost of GSM services is still extremely high when compared to the average income of African communities, many organizations are now considering alternative business models for the provision of Internet access to disadvantaged populations. To try to bridge the digital divide, the aim of this contribution is to show that basic but affordable Internet Protocol (IP) connectivity can be provided to rural communities by using spare capacity on GSM networks to carry Wireless Local Area Network (WLAN) traffic. Since the main problem with WLAN in Africa is not the last mile, but rather finding a way to connect the wireless access point to an existing backbone network, a solution to integrate WLAN with GSM is proposed.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Tests for missile defense systems are very complex, and present challenging issues for the extraction of target lethality data. Future tests will involve the use of multiple interceptors and targets with some of these assets following over-the-horizon (OTH) trajectories. The use of wireless local area network (WLAN) technologies for the acquisition of test data offers a novel approach to manage data bandwidths and link margins over-the-air (OTA) as functions of time and asset. Notional test scenarios are examined for the suitability of WLAN technologies to missile defense intercept testing.

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.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / A Wireless Local Area Network (WLAN) based system called 2-Way Robust Acquisition of Data (2-RAD) is being developed to telemeter data from a number of fast moving airborne platforms to ground collection points distributed over a large test range. The Johns Hopkins University Applied Physics Laboratory (JHU/APL) is analyzing a 2-RAD prototype currently in operation at the U.S. Army Yuma Proving Ground (YPG) that uses an IEEE 802.11b WLAN infrastructure. Preliminary analysis efforts at JHU/APL indicate that the Doppler shift from fast movers, and the system radio link margin, do not preclude IEEE 802.11b from being used for 2 -RAD.

A growing number of IEEE 802.11-based wireless LANs have been set up in many public places in the recent years. These wireless LANs provide convenient network connectivity to users. Although mobile nodes allowed roaming across wireless LANs, handoff latency becomes an obstacle when mobile nodes migrate between different IP networks. Advanced, the link-layer handoff process disrupts the association when a mobile node moves from one access point to another. Even without discussing the latency of Mobility Protocols, this link-layer handoff latency already made many real time applications can not meet their requirements. In this dissertation, it is proposed three schemes to solve the problems occurred in the different network layers. These schemes not only reduce the latency of whole handoff procedure but also have no violation to the existing specifications in the IEEE 802.11 standard and compatible with existing devices. L2-Optimize and AIL used to minimize the duration of link-layer handoff. With LASP, Mobility handoff can be reduced to an acceptable situation. Therefore, even real time applications can meet their requirements when users are roaming across wireless LANs.

In order to grapple with the continuously increasing demand on the multimedia traffic over high speed wireless LAN, we need a QoS-oriented MAC for wireless multimedia system. The IEEE 802.11's PCF is an optional capability, which is connection-oriented, and provides contention-free service, but some papers have proved that it is not efficient when use PCF to transmit voice. And there are no any efficient bandwidth allocation scheme for more high bandwidth requirement source like video in PCF. In this thesis, we will propose a efficient centralized scheduled access MAC approach in IEEE 802.11 to satisfy heterogeneous traffic mix. There are two main algorithms to achieve the goal, queue management algorithm for downlink and uplink to satisfy video traffic's high bandwidth requirement, polling list management method enhance the efficiency of the polling scheme for transmitting voice traffic. We evaluate the system performance by the network simulator OPNET, we use the MPEG-1 and ITU G.711 PCM standard as the video and voice traffic . The result shows that the centralized scheduled access MAC approach we propose has excellent efficient and compelling performance.

[pt] As Redes locais sem fio (WirelessLAN ou WLAN) surgiram como uma alternativa as redes convencionais com fio (LAN), de uma forma mais flexível, de fácil configuração e boa conectividade em áreas fechadas (prediais) ou abertas (campus). Elas combinam a mobilidade do usuário com sua conexão a rede com taxas de comunicação de até 20 Mbps ou mais, empregando técnicas de espalhamento espectral (salto em frequência - FHSS ou sequência direta - DSSS) ou acesso por modulação de frequências ortogonais - OFDM, nas faixas de frequência de 900 MHz, 2.4 Ghz e 5.7 Ghz. Dependendo da tecnologia, faixa de frequência e ambiente de utilização, o alcance das WLAN pode variar de 30 a 250 metros, ou maiores distâncias com as evoluções deste padrão. O seu projeto requer o modelamento do canal de propagação em ambientes internos . Os métodos de previsão de perda de transmissão mais utilizados são de natureza semi-empírica, devido à complexidade do problema em que envolve múltiplos mecanismos de propagação como reflexão em paredes, pisos e tetos, difração em obstáculos e transmissão através de paredes e pisos. Além da perda de propagação deve ser considerado o problema do multipercursos que produz em espalhamento de retardos, o sinal recebido afetando a qualidade do sistema. / [en] The Wireless Local Area Network (WirelessLAN or WLAN) appeared as an alternative the conventio nal Local Area Network (LAN), in a more flexible way, of easy configuration and good conectividade in closed areas (property) or open areas (campus). They combine user s mobility , his/her network connection with communication taxes of up to 20 Mbps or plus, using spread spectrum techniques (Frequency Hopping - FHSS or Direct Sequence - DSSS) or access for Orthogonais Frequency Division Modulation - OFDM, in frequency range of 900 MHz, 2.4 Ghz and 5.7 Ghz. Depending on the technology, frequency range and us e atmosphere, the reach of WLAN can vary from 30 to 250 meters, or larger distances with the evolutions of this pattern. This project requests the model of the propagation channel in internal atmospheres. The methods of forecast of transmission loss more used are of semi-empiric nature, due to the complexity of the problem in that it involves multiple propagation mechanisms as reflection in walls, floors and roofs, diffraction in obstacles and transmission through walls and floors. Besides the propagation loss it should be considered the problem of the multipath that produces in dispersal of retards, the received sign affecting the quality of the system.

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