An original asynchronous Ultra Wideband -- Impulse Radio (UWB-IR) wireless location system for sensor network is developed and evaluated through experiments. The system enables wireless nodes to be located and communicated with simultaneously at low power and low cost. The proposed system does not need system synchronization. Each access point of the proposed location system measures the time difference between two signals' received timing: one is from target node, and the other is from an access point, the position of which is already known. Then the position of the target nodes is calculated by a pseudo Time Difference of Arrival (TDOA) method. We first introduce the system configuration and asynchronous TDOA method adopted in this system. Next, we estimate the received-signal-timing measurement accuracy of UWB-IR signal and evaluate it in experiments using prototype UWB-IR transceivers. Then we estimate the location accuracy by the horizontal dilution of precision (HDOP) metric and show the field trial results of using the prototype UWB-IR location system.

A direct-sequence ultra-wideband impulse radio (DS-UWB-IR) system is developed for low-power wireless applications such as wireless sensor networks. This system adopts impulse radio characterized by a low duty cycle, and a direct-sequence 0.7-GHz bandwidth, which enables low-power operation and extremely precise positioning. Simulation results reveal that the system achieves a 250-kbps data rate for 30-m-distance wireless communications using realistic specifications. We also conduct an experiment that confirms the feasibility of our system.

Context awareness is one of the ultimate goals of ubiquitous computing, and spatial information plays an important role in building context awareness. In this paper, we propose a new interoperable spatial information model, which is based on ucode relation (ucR) and Place Identifier (PI), for realizing ubiquitous spatial infrastructure. In addition, we propose a design environment for spatial information database using our model. Our model is based on ucode and its relation. ucode is 128 bits number and the number itself has no meaning. Hence, it is difficult to manage the relation between ucodes without using a tool. Our design environment provides to describe connection between each ucode visually and is able to manipulate data using the target space map interactively. To evaluate the proposed model and environment, we designed three spaces using our tool. In addition, we developed a web application using our spatial model. From evaluation, we have been showed that our model is effective and our design environment is useful to develop our spatial information model.