Kenichi Mizugaki

Accurate Wireless Location/Communication System With 22-cm Error Using UWB-IR

We propose a high-accuracy, low-cost UWB-IR wireless location system based on the quasi TDOA method. The system consists of anchor nodes, a synch node and a location server. The anchor nodes synchronize each other as regulated by the synch node so that synchronization is always precise in the location process. To make the anchor node simple, the location system uses acquisition and tracking functions that can measure the time when a signal is received as accurately as pulse signal width. In addition, we performed a wireless location experiment indoors and the average error of the location measurement was 22-cm

TOA/TDOA hybrid relative positioning system using UWB-IR

We developed a TOA/TDOA hybrid relative positioning system with UWB-IR technology. The proposed system reduces both the number of base stations and the wireless communication times in a positioning sequence. We evaluated the system performance over various distances between base stations by using computer simulations and experiments, assuming that the target nodes were outside the area surrounded by the base stations. For the experiments, we implemented the system with UWB transceivers that we developed. From the experimental results, we confirmed that the proposed system could detect the relative positions of the target nodes using two base stations 4 m apart and with a measured angle accuracy of 8.6 degrees.

A CMOS UWB-IR Receiver Analog Front End with Intermittent Operation

A low power receiver analog front end (AFE) for ultra-wideband impulse radio (UWB-IR) was developed in 0.18 mum CMOS. All circuits of the receiver AFE operate intermittently with a sampling clock of an analog-digital converter (ADC). The sampling rate of the ADC is equal to pulse repetition frequency of the received signals. Power consumption of the receiver AFE is decreased 60% by intermittent operation without degrading of receiver sensitivity. As a result, the power consumption of the receiver AFE is 38 mW at 258 kbps data rate.

Rapid signal acquisition for low-rate carrier-based ultra-wideband impulse radio

In this paper, a rapid signal-acquisition method is proposed for carrier-based ultra-wideband impulse-radio systems in low-data-rate applications such as sensor networks. For low-data-rate ultra-wideband impulse radio systems, highly precise synchronization must be established over relatively long periods. In the proposed method, signal-acquisition times are reduced by assigning different blocks responsibility for synchronization with the pulse and with the spreading code. Furthermore, dividing up the symbols to produce a smaller unit for integration enables signal acquisition even when there is a realistic difference between the transmitter and receiver-local frequencies. Results of simulation indicate that, for a given Eb/N0, the proposed method reduces acquisition times from those required by the conventional method.

0.7-GHz-Bandwidth DS-UWB-IR System for Low-Power Wireless Communications

A direct-sequence ultra-wideband impulse radio (DSUWB-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-mdistance wireless communications using realistic specifications. We also conduct an experiment that confirms the feasibility of our system.

Adaptive channel diversity method based on ISA100.11a standard for wireless industrial monitoring

An adaptive channel diversity (ACD) ISA100.11-based method in wireless systems for industrial monitoring has been developed. The reliability performance (packet error rate vs. throughput) is calculated using measured data. It improves communication reliability by dynamically selecting higher quality frequency channels. Static analysis evaluation using a 30-device system with a star topology showed that using this method can reduce system latency by about 65% under wireless LAN conditions and that the effect is evident when the radio link quality is measured during periods of interference noise. The ACD method can thus be used to measure communication link quality in wireless radio environments and thus help reduce interference from other wireless systems.

Verification of interference avoidance effect with Adaptive Channel Diversity method based on ISA100.11a standard

We propose the Adaptive Channel Diversity (ACD) method to improve the wireless performances in terms of reliability and latency. The ACD selects the optimum channel frequencies depending on the amount of dynamic radio interference. We have used this ACD method in prototype systems that are based on the technologies adopted in the ISA100.11a standard, time division multiple access (TDMA), and the frequency channel hopping (FH). By evaluating our prototype systems with the 2.4-GHz ISM band, a 10-4 packet loss rate was achieved within a 1.3-s latency for a 30-terminal star topology system, and within a 0.85-s latency for a 5-terminal multi-hop topology system. These results were consistent with our simulations.

Tagless location system using UWB impulse radio

A tagless location system is proposed and experimentally demonstrated. The delay profile of UWB impulse radio can be detected easily because of its nanosecond pulse width. This profile appears as spatial information such as the location of a person. The profile is influenced by the propagation environment. Therefore, we can use the delay profile associated with specific location information as an indicator of the tagless location. We describe the system configuration and discuss the results of the principal experiment. The results of a 20-position trial show that the recognition ratio is 60–70%.