Wireless communication device and wireless communication method

1. A wireless communication device, comprising:

a transmitter configured to transmit a first frame containing notification information to specify a first wireless terminal and a second wireless terminal and a second frame for channel estimation; and

a receiver configured to receive a third frame transmitted from the first wireless terminal in response to the first frame and a fourth frame transmitted from the second wireless terminal; in response to the first frame,

wherein the third frame and the fourth frame are transmitted in a multiplexing scheme by the first wireless terminal and the second wireless terminal,

wherein the third frame contains first channel information estimated based on the second frame,

wherein the fourth frame contains second channel information estimated based on the second frame, and

wherein

the first frame contains first information to specify a preamble of the third frame and a preamble of the fourth frame, the preamble of the third frame and the preamble of the fourth frame include mutually-orthogonal bit patterns for channel estimation, and the receiver receives the third frame and the fourth frame whose preambles include the bit patterns specified by the first information from the first terminal and the second terminal in same frequency band, or

the first frame contains second information to specify a first subcarrier used for transmission of a preamble of the third frame and a second subcarrier orthogonal to the first subcarrier, used for transmission of a preamble of the fourth frame, the receiver receives the preambles of the third frame and the fourth frame transmitted via the first subcarrier and the second subcarrier specified by the second information from the first wireless terminal and the second wireless terminal, the preambles include any bit patterns for channel estimation,

and receives parts following the preambles of the third frame and the fourth frame in same frequency band.

2. The device according to claim 1 , wherein the receiver obtains third channel information and fourth channel information by estimating channels based on the bit pattern of the preamble of the third frame and the bit pattern of the preamble of the fourth frame received, and demodulates parts following the preambles of the third frame and the fourth frame based on the third channel information and the fourth channel information.

3. The device according to claim 1 , wherein the bit patterns of the preambles of the third frame and the fourth frame which are mutually orthogonal corresponds to different ones of rows or columns in an orthogonal matrix based on a total number of streams used by the first wireless terminal and the second wireless terminal.

4. The device according to claim 3 , wherein the notification information contains information on the total number of streams used by the first wireless terminal and the second wireless terminal.

5. The device according to claim 1 , wherein the notification information contains information on a number of streams allowed for the first wireless terminal and information on a number of streams allowed for the second wireless terminal.

6. The device according to claim 1 , wherein the notification information contains information on an amount of correction for a frequency used in transmission of the third frame and an amount of correction for a frequency used in transmission of the fourth frame.

7. The device according to claim 1 , wherein the notification information contains information on a transmission power value of the first frame and information on an expected received power value of the third frame and an expected received power value of the fourth frame.

8. The device according to claim 1 , wherein the transmitter is configured to transmit the second frame after the first frame is transmitted.

9. The device according to claim 1 , further comprising: at least one antenna.

10. A wireless communication device, comprising:

a receiver configured to receive a first frame containing notification information to specify the wireless communication device and a second wireless terminal and a second frame for channel estimation, from a third terminal; and

a transmitter configured to transmit a third frame in response to the first frame to the third wireless terminal, which contains first channel information based on the second frame,

wherein the third frame is multiplexed with a fourth frame transmitted in response to the first frame from the second wireless terminal, and

wherein

the first frame contains first information to specify a bit pattern of a preamble of the third frame and a bit pattern of a preamble of the fourth frame, the transmitter transmits the third frame having the preamble having the bit pattern specified by the first information, the bit pattern of the preamble of the third frame is orthogonal to the bit pattern of the preamble of the fourth frame transmitted from the second wireless terminal, and the third frame and the fourth frame are transmitted in same frequency band, or

the first frame contains second information to specify a first subcarrier used for transmission of a preamble of the third frame and a second subcarrier orthogonal to the first subcarrier, used for transmission of a preamble of the fourth frame, the transmitter transmits the preamble of the third frame via the first subcarrier specified by the second information, the third frame having a bit pattern for channel estimation,

and a part following the preamble of the third frame is transmitted in same frequency band as that of a part following the preamble of the fourth frame.

11. The device according to claim 10 , wherein

the notification information contains information on a transmission power value of the first frame, an expected received power value of the third frame, and

the transmitter is configured to transmit the third frame at transmission power determined such that received power of the third frame in the third wireless terminal is coincident with the expected received power value.

12. The device according to claim 10 , wherein the bit patterns of the preambles of the third frame and the fourth frame which are specified by the first information correspond to different ones among rows or columns in an orthogonal matrix based on a total number of streams used by the wireless device and the second wireless terminal.

13. The device according to claim 10 , wherein

the notification information contains on an amount of correction for a frequency used in transmission of the third frame, and

the transmitter is configured to transmit the third frame on a basis of the amount of correction.

14. The device according to claim 10 , further comprising: at least one antenna.

15. A wireless communication method, comprising:

transmitting a first frame containing notification information to specify a first wireless terminal and a second wireless terminal and a second frame for channel estimation; and

receiving a third frame transmitted from the first wireless terminal in response to the first frame and a fourth frame transmitted from the second wireless terminal in response to the first frame,

wherein the third frame and the fourth frame are transmitted in a multiplexing scheme by the first wireless terminal and the second wireless terminal,

wherein the third frame contains first channel information estimated based on the second frame,

wherein the fourth frame contains second channel information estimated based on the second frame, and

wherein

the first frame contains first information to specify a preamble of the third frame and a preamble of the fourth frame, the preamble of the third frame and the preamble of the fourth frame include mutually-orthogonal bit patterns for channel estimation, the method comprises receiving the third frame and the fourth frame whose preambles include the bit patterns specified by the first information from the first terminal and the second terminal in same frequency band, or

the first frame contains second information to specify a first subcarrier used for transmission of a preamble of the third frame and a second subcarrier orthogonal to the first subcarrier, used for transmission of a preamble of the fourth frame, the method comprises receiving the preambles of the third frame and the fourth frame via the first subcarrier and the second subcarrier specified by the second information from the first wireless terminal and the second wireless terminal,

and receiving parts following the preambles of the third frame and the fourth frame in same frequency band.

16. The method according to claim 15 , further comprising obtaining third channel information and fourth channel information by estimating channels based on the bit pattern of the preamble of the third frame and the bit pattern of the preamble of the fourth frame received, and demodulates parts following the preambles of the third frame and the fourth frame based on the third channel information and the fourth channel information.

17. The method according to claim 15 , wherein the bit patterns of the preambles of the third frame and the fourth frame which are mutually orthogonal corresponds to different ones among rows or columns in an orthogonal matrix based on a total number of streams used by the first wireless terminal and the second wireless terminal.

18. The method e according to claim 15 , wherein the notification information contains information on a transmission power value of the first frame, an expected received power value of the third frame and an expected received power value of the fourth frame.

19. The method according to claim 15 , wherein the second frame is transmitted after the first frame is transmitted.

20. The device according to claim 10 wherein

the receiver is configured to receive the first frame and the second frame in compliance with IEEE 802.11 standards, and

the transmitter is configured to transmit the third frame in compliance with IEEE 802.11 standards.