A transmission and receiving method for transmitting an uplink signal to a base station and receiving a first downlink signal and a second downlink signal from the base station, comprising:
- when the uplink signal is transmitted from a telephone to the base station:
- modulating a first data stream according to a QPSK to produce a modulated signal;
- transmitting the modulated signal as the uplink signal;
- and
- when the first and second downlink signals are transmitted from the base station to the telephone:
- receiving the first downlink signal and the second downlink signal, wherein the first downlink signal has information of data for demodulation and the second downlink signal has information of a second data stream, the first downlink signal is modulated according to a QPSK, and the second downlink signal is modulated according to an n-level PSK or an n-level QAM, wherein the data for demodulation includes information representing the value of n;
- and
- demodulating the first downlink signal to produce the data for demodulation and demodulating the second downlink signal to produce the second data stream, wherein the second data stream is produced according to the data for demodulation;
- wherein a data rate of the second downlink signal is changeable.