In LTE-Advanced, which is an extended edition of 3GPP LTE (3rd Generation Partnership Project Long Term Evolution), the use of Multi Carrier (MC) transmission in an uplink has been studied in addition to the use of Single Carrier (SC) transmission.
In SC transmission, a transmission signal is transmitted using consecutive frequency bands. Therefore, in SC transmission, channel correlation between frequency bands to which a transmission signal is mapped is high, and furthermore, transmission power can be concentrated in consecutive frequency bands. Consequently, by filtering a channel estimate estimated based on a pilot signal, a significant noise averaging effect can be obtained, and satisfactory channel estimation accuracy is obtained.
On the other hand, in MC transmission, a transmission signal is transmitted using nonconsecutive frequency bands. Therefore, in MC transmission, a transmission signal can be assigned to a wider frequency band than in the case of SC transmission, enabling a greater frequency diversity effect to be obtained than with SC transmission.
Also, in LTE-Advanced, DFT-s-OFDM (Discrete Fourier Transform spread Orthogonal Frequency Division Multiplexing) with SDC (Spectrum Division Control) has been studied as a transmitting method whereby switching is performed adaptively between SC transmission and MC transmission according to the communication environment of a mobile station (see Non-Patent Literature 1, for example).
FIG. 1 is a block diagram showing an outline configuration of a DFT-s-OFDM with SDC type of radio communication terminal apparatus (hereinafter referred to as “terminal”). As shown in FIG. 1, a terminal performs DFT processing on a data signal, and adds a CP (Cyclic Prefix) before transmission. Here, switching between SC transmission and MC transmission can be performed by having the subcarrier mapping section shown in FIG. 1 control the method of mapping a data signal in the frequency domain. Specifically, SC transmission is used if the number of data divisions in the frequency domain (hereinafter referred to as the number of SD's (Spectrum Divisions)) is 1, and MC transmission is used if the number of SD's is 2 or more. A radio communication base station apparatus (hereinafter referred to as “base station”) can switch adaptively between SC transmission and MC transmission by controlling the number of SD's according to the communication environment of a terminal.
An advantage of DFT-s-OFDM with SDC is that the CM (Cubic Metric) or PAPR (Peak-to-Average Power Ratio) in MC transmission can be lowered compared with OFDMA (Orthogonal Frequency Division Multiple Access). By this means, the MC transmission application range can be widened, and coverage performance can be improved.
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