Reference signal reception and CQI computation method and wireless communication apparatus
A wireless communication base station apparatus which is able to prevent deterioration in the throughput of LTE terminals even when LTE terminals and LTE+ terminals coexist. In this apparatus, based on the mapping pattern of the reference signals used only in LTE+ terminals, a setting unit sets, in each subframe, the resource block groups where the reference signals used only by the LTE+ terminals are mapped. For symbols mapped to the antennas, an mapping unit maps, to all the resource blocks within one frame, cell specific reference signals used for both LTE terminals and LTE+ terminals. For the symbols mapped to the antennas, the mapping unit maps, to the plurality of resource blocks, of which part of the resource block groups is comprised, in the same subframe within one frame, the cell specific reference signals used only for LTE+ terminals, based on the setting results inputted from the setting unit.
1. A communication apparatus comprising:
a receiving section, which, in operation, receives a first reference signal that is mapped in a subframe and transmitted to the communication apparatus for a first communication system; and
a measuring section, which, in operation, computes a channel quality indicator (CQI) based on the received first reference signal,
wherein the first reference signal is not transmitted in a subframe where a transmission of the first reference signal collides with a transmission of physical broadcast channel (PBCH) or system information block 1 (SIB 1 ),
said receiving section, in operation, further receives a second reference signal that is mapped in all subframes and transmitted to the communication apparatus for the first communication system and another communication apparatus for a second communication system, and
said measuring section, in operation, further computes a CQI based on the received second reference signal.
2. The communication apparatus according to claim 1 , wherein said receiving section, in operation, receives a third reference signal that is mapped and transmitted on a resource block upon which data is mapped, and the communication apparatus further comprises a demodulating section, which, in operation, demodulates the data based on the received third reference signal.
3. The communication apparatus according to claim 2 , wherein the third reference signal is a UE-specific reference signal.
4. The communication apparatus according to claim 1 , wherein the second reference signal is a cell-specific reference signal.
5. The communication apparatus according to claim 1 , wherein the second reference signal is used for demodulating the PBCH or a downlink control channel.
6. The communication apparatus according to claim 1 , wherein the first reference signal is mapped such that a number of symbols of the first reference signal per resource block is lower than a number of symbols of the second reference signal per resource block.
7. The communication apparatus according to claim 1 , wherein a maximum number of antenna ports of a base station in the first communication system is larger than a maximum number of antenna ports of a base station in the second communication system.
8. The communication apparatus according to claim 1 , wherein the first communication system is a LTE-Advanced, and the second communication system is a LTE.
9. The communication apparatus according to claim 1 , wherein the first reference signal is mapped with a set period.
10. The communication apparatus according to claim 1 , wherein the first reference signal is mapped with an interval, which is the same as (i) an interval of retransmissions in a HARQ or a number of HARQ processes, (ii) an integer multiple of an interval of retransmissions in a HARQ or an integer multiple of a number of HARQ processes, or (iii) 1/N of an interval of retransmissions in a HARQ or 1/N of a number of HARQ processes, where N is a positive integer.
11. The communication apparatus according to claim 1 , wherein the first reference signal is mapped with a same period as a period, with which a CQI is reported, or with a period which is integer multiple of a period, with which a CQI is reported.
12. The communication apparatus according to claim 1 , wherein the first reference signal is mapped with a same period as a period of semi-persistent scheduling (SPS) transmission, or with a period which is 1/N of a period of SPS transmission, where N is a positive integer.
13. The communication apparatus according to claim 1 , wherein the first reference signal is a cell-specific reference signal.
14. The communication apparatus according to claim 1 , wherein the first reference signal is a channel state information-reference signal (CSI-RS).
15. A communication method comprising:
receiving a first reference signal that is mapped in a subframe and transmitted to the communication apparatus for a first communication system; and
computing a channel quality indicator (CQI) based on the received first reference signal,
wherein the first reference signal is not transmitted in a subframe where a transmission of the first reference signal collides with a transmission of physical broadcast channel (PBCH) or system information block 1 (SIB 1 ),
the method further comprises:
receiving a second reference signal that is mapped in all subframes and transmitted to the communication apparatus for the first communication system and another communication apparatus for a second communication system; and
computing a CQI based on the received second reference signal.