System-level simulation of a third generation WCDMA wireless geolocation network

A wireless geolocation system for use in a WCDMA network was simulated in Matlab. In such a system, the multipath delays have a significant effect on the mobile location estimate.Ü si ul nk end-to-end model was created according to WCDMA system specifications, where the pilot signal was spread using 28400-chip complex Gold spreading and passed through a shaping filter. The effects of multipath fading and noise was added. The received signal was passed through a receive filter and correlated with the mobile station's locally generated Gold code to find the multipath delay. The mobile location was estimated using a hyperbolic time-difference-of-arrival approach. The estimation error was calculated for various environments and channel models and found to be less than 20m for the suburban ATDMA model and less than 110m for the rural CODIT model, which is acceptable considering that one chip time corresponds to 78 m. For comparison, the former WCDMA specification of 40960-chip spreading was evaluated and an error of less than 100m was obtained for the COST-231 suburban model using the CODIT Macro Channel where one chip time corresponds to 73m. This asynchronous system was found to be a satisfactory geolocation system for WCDMA under the given conditions

Enabling programmable ubiquitous computing environments: the DAIS middleware

textEmerging ubiquitous computing scenarios involve client applications that dynamically collect information directly from the local environment by leveraging sensor network nodes opportunistically and unpredictably. Such scenarios deviate from existing deployments of sensor networks which are often highly application-specific and generally funnel information to a central collection service for a single purpose. A significant barrier to the widespread development of such flexible sensor network applications lies in the increased complexity of the programming task when compared to existing distributed or even mobile situations. Ubiquitous computing nodes are severely resource-constrained, in terms of both computational capabilities and battery power, and therefore the application development task must inherently consider low-level design concerns, such as reducing power consumption, minimizing communication in the network to extend the network’s lifetime, and handling the variability of devices’ capabilities and constraints. This complexity, coupled with the increasing demand for applications, highlights the need for programming platforms (i.e., middleware) that simplify application development. This dissertation reports on the DAIS (Declarative Applications in Immersive Sensor networks) middleware platform that enables the development of adaptive ubiquitous computing applications. Our approach focuses on minimizing communication and coordination to best ensure the network’s lifetime. DAIS attempts to localize data collection and sensor interaction to only the regions of the network required for the applications’ immediate data needs. At the programming interface level, this requires exposing some aspects of the physical world to the developer, and we accomplish this through novel programming abstractions that enable on demand access to dynamic data sources. We develop a pair of intuitive grouping abstractions, the scene (which enables local interactions) and the virtual sensor (which enables automatic abstraction of heterogeneous data), to define a coordination model that supports interactions in ubiquitous computing. We combine these abstractions with an expressive programming interface to create the complete DAIS middleware.Electrical and Computer Engineerin