In conventional radio communication systems, non-linear distortion characteristics of amplifier circuits (Power Amplifier (PA)) of transmission apparatuses cause unwanted emissions of radio waves (e.g., Out of Band Emissions (OOBE) and spurious emissions) in frequency bands other than the bands in which transmission signals are transmitted. Accordingly, various measures have been taken for preventing interference due to the unwanted emissions of radio waves, as described above, between each of the radio communication systems and other radio communication systems using a frequency band adjacent to that of the radio communication system (i.e., adjacent radio communication systems).
As a measure for preventing interference with adjacent radio communication systems, a spectrum mask for a transmission power is generally defined in a radio communication system on frequency characteristics of radio signals to be transmitted. Here, the spectrum mask for a transmission power represents an allowable range (e.g., limit value) of the transmission power in each frequency band. Values defined as spectrum masks for transmission powers include, for instance, an out of band emission, a spurious emission, and an Adjacent Channel Leakage power Ratio (ACLR) and the like. Transmission apparatuses in the radio communication systems suppress the amount of out of band emission within a range that does not exceed the spectrum mask (allowable range), thereby avoiding interference between the radio communication systems.
Here, according to the 3GPP (3rd Generation Partner Project) LTE (Long Term Evolution) Release 8 specifications (hereinafter referred to as Rel. 8 LTE), an uplink data channel (PUSCH: Physical Uplink Shared CHannel) is subjected to transmission power control (referred to as Fractional Transmission Power Control (Fractional TPC)) (e.g., see NPL 1). More specifically, the transmission apparatus (i.e., a terminal (UE: User Equipment)) controls transmission power PPUSCH(i) in a subframe i according to a definition of following equation 1.
[1]PPUSCH(i)=min{PCMAX,10 log10(MPUSCH(i))+PO—PUSCH(j)+α(j)·PL+ΔTF(i)+f(i)}[dBm]  (Equation 1)
In equation 1, PCMAX represents the maximum transmission power value set from an upper layer; MPUSCH(i) represents a bandwidth (bandwidth allocated for PUSCH transmission) [RB] allocated to PUSCH transmitted by the transmission apparatus using subframe i (i-subframe); PO—PUSCH(j) represents a received target power value; α(j) represents a coefficient by which a PL (Path Loss or Propagation Loss) estimation value is multiplied; PL represents a propagation loss estimation value estimated by the transmission apparatus (UE) in the downlink; ΔTF(i) represents an offset value set according to the type of transmission data or modulation scheme (QPSK, 16QAM, etc.); and f(i) represents a cumulative value of transmission power values (control value in a closed loop (closed-TPC)).
Furthermore, Rel. 8 LTE specifies a transmission signal power to be satisfied, by a transmission apparatus (UE) in a frequency band available for an IMT (International Mobile Telecommunication) system (hereinafter referred to as an IMT band) (e.g., see NPL 2). This definition has been made to prevent interference between a 3GPP E-UTRAN system (also referred to as an LTE system) and other radio communication systems (adjacent radio communication systems) using a frequency band adjacent to a frequency band used by the 3GPP E-UTRAN system (LTE system). More specifically, a MPR (Maximum Power Reduction) value is defined. According to the MPR value, the maximum transmission power value set in the transmission apparatus (UE) is reduced according to a modulation scheme used for modulating transmission data, a bandwidth to which transmission data is allocated (allocated bandwidth) or a frequency position at which the transmission data is allocated. Furthermore, in a specific IMT band with a particularly strict specification on a spectrum mask and the like according to radio laws and ordnances in each country, a maximum power reduction (A-MPR: Additional MPR) value for further reducing the maximum transmission power value is set. Accordingly, the transmission apparatus controls a transmission power using the maximum transmission power value (PCMAX in equation 1) in consideration of the MPR value and the A-MPR value.
Rel. 8 LTE adopts SC-FDMA (Single-Carrier Frequency Division Multiple Access) as an uplink multiple access scheme. That is, in Rel 8 LTE, in the uplink, the transmission apparatus (UE) allocates transmission signals to resources contiguous in frequency and transmits the signals (hereinafter, referred to as “contiguous hand allocation transmission), i.e., performs single-carrier transmission. Thus, in Rel. 8 LTE, the MPR value and A-MPR value are set on the basis of the transmission bandwidth, frequency position and the like for the contiguous band allocation transmission (single-carrier transmission).
As an expanded system of Rel. 8 LTE, standardization of LTE Release 10 specifications (hereinafter, referred to as Rel. 10 LTE; also referred to as LTE-Advanced System) has been started. In Rel. 10 LTE, there has been discussed allocation of PUSCH to non-contiguous frequencies and transmission thereof (non-contiguous band allocation transmission of PUSCH), and simultaneous transmission, of PUSCH and a control channel (PUCCH: Physical Uplink Control CHannel) (simultaneous transmission of PUSCH and PUCCH) (e.g., see NPLs 3, 4 and 5) in addition to contiguous band allocation transmission (single-carrier transmission) applied to Rel. 8 LTE. That is, in Rel. 10 LTE, multicarrier transmission (non-contiguous band allocation transmission) in the uplink, in addition to the single-carrier transmission (contiguous hand allocation transmission), has been discussed.
In this way, it is made possible to allocate transmission signals to a frequency band having a favorable channel quality and then transmit the signals depending on the frequency response characteristics of a channel for each transmission apparatus (UE). Accordingly, improvement in the throughput characteristics of each transmission apparatus (UE) as well as an increase in the system capacity in the uplink can be expected in Rel. 10 LTE in comparison with Rel. 8 LTE.