Attached shuttle payload carriers: Versatile and affordable access to space

The shuttle has been primarily designed to be a versatile vehicle for placing a variety of scientific and technological equipment in space including very large payloads; however, since many large payloads do not fill the shuttle bay, the space and weight margins remaining after the major payloads are accommodated often can be made available to small payloads. The Goddard Space Flight Center (GSFC) has designed standardized mounting structures and other support systems, collectively called attached shuttle payload (ASP) carriers, to make this additional space available to researchers at a relatively modest cost. Other carrier systems for ASP's are operated by other NASA centers. A major feature of the ASP carriers is their ease of use in the world of the Space Shuttle. ASP carriers attempt to minimized the payload interaction with Space Transportation System (STS) operations whenever possible. Where this is not possible, the STS services used are not extensive. As a result, the interfaces between the carriers and the STS are simplified. With this near autonomy, the requirements for supporting documentation are considerably lessened and payload costs correspondingly reduced. The ASP carrier systems and their capabilities are discussed in detail. The range of available capabilities assures that an experimenter can select the simplest, most cost-effective carrier that is compatible with his or her experimental objectives. Examples of payloads which use ASP basic hardware in nonstandard ways are also described

Design and implementation of synchronization and AGC for OFDM-based WLAN receivers

An efficient implementation of several tasks at the receiver becomes crucial in OFDM-based high-speed WLAN systems, such as automatic gain control, time and frequency synchronization and offset tracking. This paper deals with fixed point constraints and accuracy requirements for implementation of those algorithms. Also, a complete set of thresholds for the practical implementation of time and frequency synchronization sub-blocks is obtained. Moreover, a technique to mitigate the remaining frequency offset after coarse acquisition is proposed, yielding a good trade-off between performance and complexity. Finally, we propose the implementation of a simple and effective automatic gain control procedure.This work has been partially funded by Spanish government with project TIC 2002-03498 (ORISE), Telefonica I+D by the contract nº 25756, and the Chamber of Madrid Community and European Social Fund by a grant to the first author

Unequal error protection for power line communications over impulsive noise channels

Power line communication (PLC) has recently attracted a lot of interest with many application areas including smart grids\u27 data communication, where data (from sensors or other measurement units) with different QoS may be transmitted. Power line communications suffer from the excessive power lines\u27 impulsive noise (which can be caused by shedding loads on and off). In this thesis, we present a study of power line communications with unequal error protection for two and four data priority levels hierarchical QAM modulation and space-time block coding. We consider the two commonly used power lines\u27 impulsive noise models with Bernoulli and Poisson arrivals. In our proposed approaches, we achieve UEP on both of bit and symbol levels. Approximate closed form expressions for the error rates are derived for each priority level for both single carrier and OFDM in SISO and MIMO systems. In addition, these simpli fied expressions are used to implement a bit loading algorithm to provide UEP for frequency-selective PLC channels. For the case of MIMO PLC channels, we describe three different MIMO schemes to allow more control over the UEP levels. The three schemes are namely: maximum ratio combiner (MRC) receive diversity, Alamouti space-time block code, and a new structure for a space-time code that allows for unequal error protection at the symbol level. Finally, we apply an Eigen beamforming technique, assuming channel knowledge at transmitter, which improves the BER as compared to the other MIMO PLC schemes

GUARDIANS final report

Emergencies in industrial warehouses are a major concern for firefghters. The large dimensions together with the development of dense smoke that drastically reduces visibility, represent major challenges. The Guardians robot swarm is designed to assist fire fighters in searching a large warehouse. In this report we discuss the technology developed for a swarm of robots searching and assisting fire fighters. We explain the swarming algorithms which provide the functionality by which the robots react to and follow humans while no communication is required. Next we discuss the wireless communication system, which is a so-called mobile ad-hoc network. The communication network provides also one of the means to locate the robots and humans. Thus the robot swarm is able to locate itself and provide guidance information to the humans. Together with the re ghters we explored how the robot swarm should feed information back to the human fire fighter. We have designed and experimented with interfaces for presenting swarm based information to human beings