Abstract: A cognitive terminal includes different types of radio modules suiting to different types radio media employed by a cognitive base station in the radio communication system. The radio module of the cognitive terminal counts the number of times it receives/transmits ACK/NACK in each unit time. A radio environment cognition unit of the cognitive terminal performs calculations using the count number(s) in consideration of the packet transmission time interval or the time required for repeating a single data packet, thus measuring characteristics of delay time variations in uplink/downlink communication with respect to each radio media. Thus, it is possible for the cognitive terminal to switch over radio media based on ACK/NACK in uplink/downlink communication.

Abstract: A wireless base station includes: a trend factor regression expression calculator for determining, on the basis of measured wireless communication environment factor, the trend of the variation in the environment factor; a trend prediction value calculator for calculating, on the basis of the determined trend of the variation in the environment factor, the environment prediction value; an irregular variation factor calculator for calculating, on the basis of the difference between the determined trend of the environment factor variation and the measured environment factor, the magnitude of correction to be applied to the environment prediction value; and a radio environment prediction correction unit for correcting the environment prediction value according to the tolerance of the base station for its communication failure risk.

Abstract: A cognitive terminal includes different types of radio modules suiting to different types radio media employed by a cognitive base station in the radio communication system. The radio module of the cognitive terminal counts the number of times it receives/transmits ACK/NACK in each unit time. A radio environment cognition unit of the cognitive terminal performs calculations using the count number(s) in consideration of the packet transmission time interval or the time required for repeating a single data packet, thus measuring characteristics of delay time variations in uplink/downlink communication with respect to each radio media. Thus, it is possible for the cognitive terminal to switch over radio media based on ACK/NACK in uplink/downlink communication.

Abstract: A wireless base station includes: a trend factor regression expression calculator for determining, on the basis of measured wireless communication environment factor, the trend of the variation in the environment factor; a trend prediction value calculator for calculating, on the basis of the determined trend of the variation in the environment factor, the environment prediction value; an irregular variation factor calculator for calculating, on the basis of the difference between the determined trend of the environment factor variation and the measured environment factor, the magnitude of correction to be applied to the environment prediction value; and a radio environment prediction correction unit for correcting the environment prediction value according to the tolerance of the base station for its communication failure risk.

Abstract: A microstrip antenna of two-frequency separate-feeding type for circularly polarized waves is disclosed, in which four radiation conductors are disposed on a dielectric plate mounted on a conducting ground plane and each radiation conductor has its marginal portion partly short-circuited via a short-circuiting conductor to the conducting ground plane and is supplied at its feeding point with power via a feeder passing through the conducting ground plane and the dielectric plate. The four radiation conductors are composed of two pairs of radiation conductors of different sizes adjusted so that two desired frequencies can simultaneously be used for transmission and for reception, respectively, the conductors of each pair being arranged to generate a circularly polarized wave.