Abstract: A battery built-in wireless ID card unit including a magnetic field detection section which generates an electromotive force from a received magnetic field to turn on a power switch of a built-in battery, and a control section which transmits an ID code by radio after the power switch is turned on, thereby turning off the power switch.

Abstract: A data transmitter-receiver for reducing high-frequency noise which leads to a cause of performance deterioration of a radio instrument, and for eliminating dissipation current. The data transmitter-receiver transmits transmitting data to a modulator-demodulator connected to a radio instrument, and receives receiving data from the modulator-demodulator. A terminal controlling section 3 of the data transmitter-receiver performs data processing on the receiving data, thus outputting to a data-terminal, and performs data processing transmitting signal from the data-terminal, thus generating the receiving data.

Abstract: A radio channel estimation method includes a combination of BER (bit error rate) estimation and RSSI (received signal strength indicator) estimation. The RSSI and the BER are detected from a received signal through a radio channel, and then the radio channel is estimated based on the RSSI and the BER. A quality of the radio channel is estimated to be degraded unless the BER meets a first criterion and the RSSI meets a second criterion. The BER meets the first criterion when an average number of times during a time period that the BER exceeds a maximum value is smaller than a first threshold value. The RSSI meets the second criterion when an average number of times during a time period that the RSSI is below a minimum value is smaller than a second threshold value.

Abstract: An RSSI detector 2 detects the electric field level of a received signal, and a transmission rate determiner 5 determines an initial transmission rate value from the detected electric field level. A radio unit 1 transmits the determined initial value to a base station 20. In response thereto, the base station 20 transmits a control signal at the assigned initial transmission rate value. A bit error rate value detector 4 detects a bit error rate of the control signal, and a transmission rate determiner 5 finely regulates the initial value according to the detected bit error rate. An optimal transmission rate is thus determined.