Shuichi Yoshino

A new in-door location detection method adopting learning algorithms

This new location detection method uses wireless LAN systems. The location of the user station is established using the received intensity at a user station of signals from wireless base stations. The method employs two unique concepts. 1) Instead of a discrete coordinate position to define the location of user station, the location is found by using a localized area. 2) The learning algorithms based on LVQ (learning vector quantization) are applied to process in location. As a result, our method provides more accurate positions compared with conventional least squares method (LSM) methods in areas far from the base points.

Cell Range Extension Techniques for Wide-Area Ubiquitous Network

This paper describes a newly developed wireless access system for the wide area ubiquitous network (WAUN), a large cell-based public sensor network. It introduces two key technologies to achieve WAUN with wide area coverage. The first is a digitalized radio over optical fiber (DROF) subsystem that allows cost-effective commercial packet based networks to transfer wireless RF signals among distributed access points. The second is a frequency offset transmitter diversity scheme that achieves sub optimal diversity gain without rate loss, regardless of the number of antennas, by using intentional and orderly frequency offset.

Successive interference canceller with residual interference reduction for M2M wireless access system

This paper proposes two residual interference reduction schemes for the successive interference canceller (SIC) in M2M wireless access systems. In general, its difficult for SIC to completely eliminate interference due to channel estimation errors. Such errors are a serious problem if there are many terminals and the environment is multi-path. The first scheme, the Pre-FDE scheme, employs frequency domain pre-equalization (Pre-FDE) at the terminal side to alleviate the effect of multi-path propagation; it allows the base station to estimate the channel state information (CSI) precisely and also to reduce the residual interference. In the second scheme, the Path-SIC scheme, the base station estimates the CSI accurately by dealing with the interference replica of one path, not one terminal in one subtraction. Both schemes are simulated using actual temporal channel variations obtained by experiments. The simulation results show that the Pre-FDE scheme and the Path-SIC scheme improve the number of terminals transmitting simultaneously from 6 to over 10 compared with the conventional one. However, the PER performance of the Pre-FDE scheme degrades as the environmental speed increases.

Frequency offset transmitter diversity for M2M access system

This paper applies a frequency offset transmitter diversity method for Machine-to-Machine (M2M) communication systems. Wireless terminals based on ZigBee and Wi-SUN offer long term usage and low cost. Frequency offset transmitter diversity is useful for these M2M applications because all it needs are additional access point antennas and an error correction function. Conventionally, the error correction function must employ hard decision to support various modulation/demodulation schemes. This paper proposes a Viterbi algorithm with soft decision that uses received signal strength metric calculated by an external circuit.