Base station and mobile station for ofdma cellular system

Abstract

In a cellular radio communication system, a base station or a mobile station has a TA (Time Alignment)-range-out detection function, so that when a TA-range-out state that is unable to compensate with a guard interval is detected, the transmission condition of an uplink signal at the mobile station is changed by the mobile station autonomously or by the base station and the mobile station cooperatively.

1 . A base station comprising:
 an antenna for communicating radio frequency (RF) signals with a mobile station;   a front end unit for converting the RF signal received by the antenna into an uplink baseband signal, and converting a downlink baseband signal to be transmitted to the mobile station into an RF signal to output the RF signal to the antenna;   a demodulation processing unit for demodulating the uplink baseband signal;   an uplink-timing detector for detecting a reception timing gap of an uplink signal transmitted by the mobile station, on the basis of the uplink baseband signal;   a time alignment (TA) control signal generator for generating a TA control signal based on the uplink signal reception timing gap detected by the unlink-timing detector;   a transmission condition change signal generator which generates a transmission change signal;   a modulation processing unit for multiplexing a downlink data signal for the mobile station and a control signal includes the TA control signal and a signal for changing a transmission condition of the uplink signal in the mobile station based on a result of a comparison between a predetermined threshold and the uplink signal reception timing gap.