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US-RE50891-E1 - Wireless communication device and wireless communication method

Abstract

A wireless communication device includes a transmitter and a receiver. The transmitter transmits a first frame containing notification information to specify first and second wireless terminals and a second frame for channel estimation. The receiver receives a third frame transmitter from the first wireless terminal and a fourth frame transmitted from the second wireless terminal. The third frame and the fourth frame are transmitted in a multiplexing scheme by the first and the second wireless terminals. The third frame contains first channel information estimated based on the second frame. The fourth frame contains second channel information estimated based on the second frame. The first frame contains at least either information to specify a preamble of the third frame and a preamble of the fourth frame or information to specify a subcarrier used for transmission of the third frame and a subcarrier used for transmission of the fourth frame.

Inventors

  • Toshihisa Nabetani
  • Tsuguhide Aoki
  • Hiroki Mori

Assignees

  • INTERNATIONAL SEMICONDUCTOR GROUP

Dates

Publication Date
20260512
Application Date
20230711
Priority Date
20131227

Claims (20)

  1. 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. 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. 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. 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. 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. 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. 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. 8 . The device according to claim 1 , wherein the transmitter is configured to transmit the second frame after the first frame is transmitted.
  9. 9 . The device according to claim 1 , further comprising: at least one antenna.
  10. 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. 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. 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. 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. 14 . The device according to claim 10 , further comprising: at least one antenna.
  15. 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. 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. 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. 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. 19 . The method according to claim 15 , wherein the second frame is transmitted after the first frame is transmitted.
  20. 20. A wireless communication device, comprising: a transmitter configured to transmit a first packet containing notification information to specify a first wireless terminal and a second wireless terminal and transmit a second packet for channel estimation after the first packet is transmitted; and a receiver configured to receive a third packet transmitted from the first wireless terminal in response to the first packet and a fourth packet transmitted from the second wireless terminal in response to the first packet, after the second packet is transmitted, wherein the third packet and the fourth packet are transmitted in a multiplexing scheme by the first wireless terminal and the second wireless terminal, wherein the third packet contains first channel information estimated based on the second packet, wherein the fourth packet contains second channel information estimated based on the second packet, and wherein a preamble of the third packet and a preamble of the fourth packet include mutually-orthogonal bit patterns for channel estimation, and the receiver receives the third packet and the fourth packet whose preambles include the bit patterns specified by the wireless communication device from the first terminal and the second terminal in a same frequency band, or the receiver receives preambles of the third packet and the fourth packet transmitted via a first subcarrier used for transmission of a preamble of the third packet and a second subcarrier orthogonal to the first subcarrier used for transmission of a preamble of the fourth packet respectively specified by the wireless communication device 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 packet and the fourth packet in a same frequency band.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This applicationMore than one reissue application has been filed for the reissue of U.S. Pat. No. 10,063,342. The applications are the present application and Application Serial No. 17/006,357, filed Aug. 28, 2020. The present application is a reissue continuation of reissue application Serial No. 17/006,357, which is a reissue application of U.S. Serial No. 15/192,403, filed Jun. 24, 2016 (now U.S. Patent No. 10,063,342), which is a Continuation of International Application No. PCT/JP2015/050420, filed on Jan. 5, 2015, the entire contents of which isare hereby incorporated by reference. FIELD Embodiments described herein relate to a communication controlling device, a wireless terminal, a memory card, an integrated circuit, and a wireless communication method. BACKGROUND As a wireless communication system in which a wireless access point and a wireless terminal communicate with each other, the wireless LAN (Local Area Network) based on the IEEE 802.11 standard that uses CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) is widely known. IEEE Std 802.11™-2012 and IEEE Std 802.11ac™-2013 are known as wireless LAN specification. In the IEEE 802.11n standard, MIMO (Multi-Input Multi-Output) technology is used, which achieves an increased speed of wireless communication. In the MIMO technology, a transmission-side apparatus and a reception-side apparatus each include a plurality of antennas installed therein. The transmission-side apparatus simultaneously transmits a plurality of pieces of data with the plurality of antennas. The reception-side apparatus simultaneously receives the plurality of pieces of data with the plurality of antennas, and separates the plurality of received pieces of data from one another. This allows a plurality of data streams to be transmitted and received. The higher the number of data streams is, the higher throughput can be obtained as compared with conventional SISO (Single-Input Single-Output). In addition, in an effort to increase the speed, the IEEE 802.11ac standard is now being formulated. The IEEE 802.11ac standard uses a downlink multiuser MIMO (DL-MU-MIMO) technology, which is an expansion of the MIMO technology. In the downlink multiuser MIMO, an access point simultaneously transmits different pieces of data to a plurality of wireless terminals from a plurality of antennas. This allows the access point to simultaneously communicate with the plurality of wireless terminals. The downlink multiuser MIMO uses a technique called beamforming. In the beamforming, a beam that causes data streams addressed to the wireless terminals to least interfere with one another, that is, a beam that makes data streams addressed to the wireless terminals spatially orthogonal, are formed and transmitted for each wireless terminal. This makes spatial multiplexing available, which in turn allows the access point to simultaneously transmit different pieces of data to the plurality of wireless terminals. To implement the downlink multiuser MIMO, the access point needs to obtain information on channels between the antennas thereof and the wireless terminals. That is, the access point needs to detect how the wireless terminals receive signals transmitted from the antennas thereof. Using information on the channels allows the access point to form an optimal beam that does not interfere with other wireless terminals. The IEEE 802.11ac standard defines such a protocol that allows for estimation of the channels between the access point and the wireless terminals. According to the protocol defined in the IEEE 802.11ac standard, the access point causes the wireless terminals to estimate channel responses and to feed them back in turn, so as to detect a state of the channels with respect to the wireless terminals. As a result, the higher the number of the wireless terminals performing channel estimation, the longer it takes for the estimation to be performed. This increases an overhead time taken to start the downlink multiuser MIMO. In addition, this decreases a correlation between a state of the channels when the wireless terminals estimated them and a state of the channels when the downlink multiuser MIMO is actually started. Thus, in the downlink multiuser MIMO transmission using the channel information obtained from the wireless terminals, an adequate beam may not be formed due to temporal fluctuations of the channels. Also, an inadequately formed beam may disadvantageously interfere with other wireless terminals. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a wireless communication system according to a first embodiment; FIG. 2 is a diagram illustrating an outline of a manner an access point obtains pieces of channel information on downlinks from wireless terminals; FIG. 3 is a diagram showing an example of a frame format of a notification frame; FIG. 4 is a diagram showing another example of the frame format of the notification frame;