WO2013069906A1 - 액티브 스캐닝 방법에서 링크 적응 방법 및 장치 - Google Patents
액티브 스캐닝 방법에서 링크 적응 방법 및 장치 Download PDFInfo
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- WO2013069906A1 WO2013069906A1 PCT/KR2012/008640 KR2012008640W WO2013069906A1 WO 2013069906 A1 WO2013069906 A1 WO 2013069906A1 KR 2012008640 W KR2012008640 W KR 2012008640W WO 2013069906 A1 WO2013069906 A1 WO 2013069906A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W24/00—Supervisory, monitoring or testing arrangements
- H04W24/06—Testing, supervising or monitoring using simulated traffic
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W48/00—Access restriction; Network selection; Access point selection
- H04W48/16—Discovering, processing access restriction or access information
Definitions
- the present invention relates to wireless communications, and more particularly, to a method and apparatus for performing link adaptation.
- M2M Machine-to-Machine
- IEEE 802.11 WLAN is establishing a new standard to support it.
- M2M system refers to a network in which a machine, not a person, is a communication agent and sends and receives information.
- Home appliances such as temperature sensors, humidity sensors, cameras and TVs, process machines in factories, and even large machines such as cars can be an element of M2M.
- Recently, various communication services such as smart grid, eHealth, and ubiquitous have appeared, and M2M technology has been widely used to support such services.
- the characteristics of the M2M system are as follows.
- M2M Large number of stations: Unlike conventional networks, M2M assumes a large number of stations. This is because not only the machines owned by the individual but also the sensors installed in the house and the company must be considered. Therefore, a considerable number of stations can be connected to one AP.
- M2M terminal has a traffic pattern that collects and reports the surrounding information, it does not need to send information frequently and the amount of information sent is small.
- M2M has a structure of receiving commands by downlink, taking actions, and reporting the result data to uplink. Since the main data is usually transmitted on the uplink, the uplink is the center of the M2M.
- M2M terminals are mainly battery operated and are often difficult for users to charge frequently. Therefore, it is required to ensure long life by minimizing battery consumption.
- M2M terminal needs to recover itself because it is difficult for a person to directly operate in a specific situation.
- An object of the present invention is to provide a link adaptation method between an STA and an AP in a WLAN system.
- Still another object of the present invention is to provide an apparatus for performing a link adaptation method between an STA and an AP.
- a link adaptation method includes transmitting a probe request frame including a null data packet announcement (NDPA) information element. And transmitting a null data packet (NDP) frame including only a physical layer convergence protocol (PLCP) header after transmitting the probe request frame and a feedback information element calculated based on the NDP frame. receiving a probe response frame including an element; wherein the NDPA information element includes whether the probe request frame serves as an NDPA frame.
- NDP information (information) indicating whether or not, the feedback information element (information element) is MCS (modulation and coding scheme) may include at least one of feedback information and sounding feedback information.
- the link adaptation method may further include receiving an NDP frame after receiving the probe response frame when the probe response frame includes an NDPA information element and the NDP. And transmitting an authentication request frame including an feedback information element based on the frame, wherein the feedback information element includes MCS feedback information and sounding feedback. It may include at least one of sounding feedback information.
- the NDPA information element further includes a feedback type, beamforming, and Nc index, wherein the feedback type indicates whether the feedback information is transmitted to a single user or multiple users.
- the beamforming is an indicator indicating whether beamforming is performed, and the Nc index may be an indicator indicating a feedback dimension required when using the beamforming. .
- the MCS feedback information includes the number of spatial streams, the MCS index, and the number of the spatial streams is an indicator indicating the number of spatial streams used for transmission, and the MCS index is It may be an indicator indicating a modulation and coding scheme used for transmission.
- the sounding feedback information includes a compressed beamforming report, and the compressed beamforming report includes a signal to SNR for each spatial stream. noise ratio) and at least one beamforming matrix.
- the link adaptation method may further include transmitting an authentication request frame by a multiple input multiple output (MIMO) transmission method using beamforming based on the MCS feedback information.
- MIMO multiple input multiple output
- a wireless terminal for achieving the above object of the present invention includes a transceiver (transceiver), the transceiver includes a probe request including a null data packet announcement (NDPA) information element (information element) After transmitting a probe request frame and transmitting the probe request frame, a null data packet (NDP) frame including only a physical layer convergence protocol (PLCP) header is transmitted and based on the NDP frame. And receive a probe response frame including a calculated feedback information element, wherein the NDPA information element includes a probe request frame in which the probe request frame is an NDPA frame.
- NDP information (information) indicating whether to play the role of, and the feedback information element (information eleme) nt) may include at least one of modulation and coding scheme (MCS) feedback information and sounding feedback information.
- MCS modulation and coding scheme
- the probe response frame includes an NDPA information element
- an NDP frame is received and a feedback information element based on the NDP frame is received.
- the authentication information frame is configured to transmit an authentication request frame including an information element, wherein the feedback information element includes at least one of MCS feedback information and sounding feedback information. Can be.
- the NDPA information element further includes a feedback type, beamforming, and Nc index, wherein the feedback type indicates whether the feedback information is transmitted to a single user or multiple users.
- the beamforming is an indicator indicating whether or not the beamforming is transmitted. .
- the MCS feedback information includes a number of spatial streams and an MCS index, and the number of spatial streams is an indicator indicating the number of spatial streams used for transmission, and the MCS index May be an indicator indicating a modulation and coding scheme used for transmission.
- the sounding feedback information includes a compressed beamforming report, and the compressed beamforming report includes a signal to SNR for each spatial stream. noise ratio) and at least one beamforming matrix.
- the transceiver may be implemented to transmit an authentication request frame by a multiple input multiple output (MIMO) transmission method using beamforming based on the MCS feedback information.
- MIMO multiple input multiple output
- the STA performs the link adaptation initially by using a management frame transmitted during the scanning / authentication / association process, and thus, from the initial connection.
- Data transmission efficiency can be improved by using a modulation coding scheme (MCS) suitable for a channel situation.
- MCS modulation coding scheme
- FIG. 1 is a conceptual diagram illustrating a method for receiving feedback of channel state information from an access point (AP) based on a sounding protocol.
- FIG. 2 is a conceptual diagram illustrating a scanning method in a WLAN.
- FIG. 3 is a conceptual diagram illustrating an authentication and combining process after scanning of an AP and an STA.
- FIG. 4 is a conceptual diagram illustrating a link adaptation method according to an embodiment of the present invention.
- FIG. 5 is a conceptual diagram illustrating a link adaptation method according to an embodiment of the present invention.
- FIG. 6 is a conceptual diagram illustrating a link adaptation method using SU-MIMO according to an embodiment of the present invention.
- FIG. 7 is a conceptual diagram illustrating a data transmission and reception method using beamforming according to an embodiment of the present invention.
- FIG. 8 is a conceptual diagram illustrating a data transmission and reception method using beamforming according to an embodiment of the present invention.
- FIG. 9 is a conceptual diagram illustrating an NDPA element format according to an embodiment of the present invention.
- FIGS. 10 and 11 are conceptual diagrams illustrating an MCS feedback information element and a sounding feedback element according to an embodiment of the present invention.
- FIG. 12 is a block diagram illustrating a wireless device to which an embodiment of the present invention can be applied.
- IEEE 802.11 used in an embodiment of the present invention is IEEE P802.11ac TM / D2.0 Draft STANDARD for Information Technology Telecommunications and information exchange between systems Local and metropolitan area networks Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications Amendment 4: Enhancements for Very High Throughput for Operation in Bands below 6 GHz.
- MAC Wireless LAN Medium Access Control
- PHY Physical Layer
- the link adaptation method disclosed in an embodiment of the present invention may be applied to an M2M system, but may also be applied to other wireless local area networks (WLANs).
- WLANs wireless local area networks
- the name or subfield of a frame used in the link adaptation method disclosed in the present invention may be changed or additionally removed except for a subfield including an indication for performing an essential operation performed in the present invention. Can be.
- FIG. 1 is a conceptual diagram illustrating a method for receiving feedback of channel state information from an access point (AP) based on a sounding protocol.
- channel state information feedback between the AP 100 and STAs 110, 120, and 130 may be obtained through a sounding protocol.
- An access point (AP) 100 may receive feedback on channel state using a null data packet announcement (NDPA) 102 frame and a null data packet (NDP) frame.
- NDPA null data packet announcement
- NDP null data packet
- the NDPA frame 102 is a frame including association identifier (AID) information, feedback type information, and the like of an STA to which the NDP frame 104 is to be transmitted. Prior to transmitting the NDP frame 104, the NDPA frame 102 may be transmitted to prepare the STA 110, 120, and 130 for CSI feedback before receiving the NDP frame 104.
- the structure of NDPA frame 102 is described in IEEE 802.11 8.3.1.20.
- a null data packet (NDP) frame is a frame having a VHT PPDU structure excluding a data field and is transmitted after a short interface space (SIFS) after transmitting the NDPA frame 102.
- SIFS short interface space
- the AP 100 may transmit the NDPA frame 102 and may transmit the NDP frame 104 after SIFS.
- the first STA 110 may receive the NDP frame 104 through the NDPA frame 102 and transmit a frame including the feedback information 115 to the AP 100 after SIFS.
- the feedback information 115 may be feedback information related to MCS, channel feedback information related to beamforming, and the like.
- the AP 100 may transmit a poll frame 106 to obtain channel information from the second STA 120.
- the second STA 120 that receives the poll frame 106 may transmit feedback information 125 to the AP 100.
- the poll frame 106 is a frame performing the same role as the NDP frame 104 and may measure a channel state based on the poll frame 106 transmitted from the second STA 120.
- feedback information 135 may be generated between the AP 100 and the third STA 130 and transmitted to the AP 100.
- channel state information measurement between an AP and an STA using an NDPA frame and an NDP frame may be performed through a management frame transmitted in a scanning / authentication / association process.
- the CSI measurement result using the management frame format may be used to determine a modulation coding scheme (MCS) and perform link adaptation.
- MCS modulation coding scheme
- FIG. 2 is a conceptual diagram illustrating a scanning method in a WLAN.
- the scanning method may be divided into a passive scanning method 200 and an active scanning method 250.
- the passive scanning method 200 may be performed by a beacon frame 230 periodically broadcasted by the AP 200.
- the AP 200 of the WLAN broadcasts the beacon frame 230 to the non-AP STA 240 every 100 msec.
- the beacon frame 230 may include information about the current network.
- the non-AP STA 240 may perform scanning of the AP 210 and the channel to receive the network information and to perform the authentication / association process by receiving the beacon frame 230 broadcast periodically.
- the passive scanning method 200 only needs to receive the beacon frame 230 transmitted from the AP 210 without the need for the non-AP STA 240 to transmit the frame. Therefore, passive scanning 200 has an advantage that the overall overhead generated by data transmission / reception in the network is small. However, since the scanning can be performed manually in proportion to the period of the beacon frame 230, the time taken to perform scanning increases.
- the active scanning 250 refers to a method in which a non-AP STA 290 transmits a probe request frame 270 to the AP 260 to proactively perform scanning.
- the AP 260 After receiving the probe request frame 270 from the non-AP STA 290, the AP 260 waits for a random time to prevent frame collision and then includes network information in the probe response frame 280. Send to 290.
- the non-AP STA 290 may obtain network information based on the received probe response frame 280 and stop the scanning process.
- the probe request frame 270 is disclosed in IEEE 802.11 8.3.3.9 and the probe response frame 280 is disclosed in IEEE 802.11 8.3.3.10.
- the AP and the STA may perform an authentication and association process.
- FIG. 3 is a conceptual diagram illustrating an authentication and combining process after scanning of an AP and an STA.
- FIG. 3 (A) is a conceptual diagram showing an authentication and combining process after passive scanning
- FIG. 3 (B) is a conceptual diagram showing an authentication and combining process after active scanning.
- the authentication and association process may be performed by using an AP (authentication request frame 310) / authentication response frame (320) and association request frame (330) / association response frame (340) regardless of whether active scanning is used or passive scanning is used. The same may be performed by exchanging between 300 and 350 and non-AP STAs 305 and 355.
- AP authentication request frame 310
- authentication response frame 320
- association request frame 330
- association response frame 340
- the authentication process may be performed by transmitting the authentication request frame 310 from the non-AP STAs 305 and 355 to the APs 300 and 350.
- the authentication response frame 320 may be transmitted from the AP 300, 350 to the non-AP STAs 305, 355.
- the authentication frame format is described in IEEE 802.11 8.3.3.11.
- the association process may be performed by transmitting the association request frame 330 to the APs 300 and 305 in the non-AP STAs 305 and 355.
- the association response frame 340 may be transmitted from the AP 305 and 355 to the non-AP STA 300 and 350.
- the transmitted association request frame 330 includes information about the capabilities of the non-AP STAs 305 and 355. Based on the performance information of the non-AP STAs 305 and 355, the APs 300 and 350 may determine whether support is possible for the non-AP STAs 305 and 355.
- the AP 300 or 350 may include the non-AP STA 305 in the association response frame 340 by including whether the association request frame 330 is accepted and the reason thereof, and capability information that can be supported. , 355).
- the association frame format is disclosed in IEEE 802.11 8.3.3.5/8.3.3.6.
- association step normal data transmission and reception are then performed. If the association is not performed, the association may be performed again or the association may be performed to another AP based on the reason why the association is not performed.
- MCS may be determined using open-loop rate adaptation.
- open-loop rate adaptation is a method of adjusting a coding rate without feedback of channel conditions.
- transmission starts at a lower code rate.
- the frame is transmitted without error (for example, when the transmitting end of the frame receives the ACK transmitted by the receiving end)
- a frame using a high index MCS using a high code rate may be transmitted.
- a frame using a low MCS index with a low code rate can be transmitted.
- low MCS (or low MCS index) is an MCS method used when channel conditions are not good, and is modulated by a low bit / symbol modulation technique or channel coded with a low coding rate and low data. Indicates the transmission method with the transmission speed.
- High MCS (or high MCS index) refers to a method used when channel conditions are good and is modulated by a high bit / symbol modulation technique or a channel coded at a high coding rate and transmitted at a high transmission rate.
- a probe request frame 360, a probe response frame 370, an authentication request frame 310, an authentication response frame 320, and an association are performed while performing a scanning / authentication / association process.
- Various management frames such as request frame 330 and association response frame 340 are transmitted and received between the AP and the non-AP STA, and a lot of time is required to perform this process.
- An embodiment of the present invention discloses a method of improving data throughput in an initial stage of performing an access between an AP and a STA by transmitting and receiving a frame using an MCS for a channel state in a scanning / authentication / association process.
- FIG. 4 is a conceptual diagram illustrating a link adaptation method according to an embodiment of the present invention.
- link adaptation may be performed using the probe request frame 455 as a role of the NDPA frame.
- the probe request frame 455 for performing active scanning in the STA 450 may be transmitted to the AP 400.
- the probe request frame 455 may play the same role as the NDPA frame by adding an NDPA element as an information element of the probe request frame 455.
- the information element of the newly defined probe request frame 455 will be further described below. That is, the MCS may be applied from the scanning step by knowing the channel state information in the process of exchanging the initial management frame.
- the STA 450 transmits the NDP frame 460 to the AP 400.
- the STA 450 may transmit the NDP frame 460 after transmitting the probe request frame 455 serving as the NDPA frame to the AP 400.
- the NDP frame 460 may be used by the AP 400 receiving the NDP frame 460 to feed back a channel state.
- the probe response frame 410 is transmitted from the AP 400 to the STA 450.
- the MCS feedback element may be added as a new information element in the probe response frame 410 transmitted from the AP 400 to the STA 450.
- the MCS feedback element may include an MCS feedback value calculated based on the NDP frame 460.
- the information element of the newly defined probe response frame 410 will be further described below.
- the STA 450 transmits an authentication request frame 465 to the AP 400.
- the STA 450 may transmit the authentication request frame 465 generated based on the MCS value fed back from the probe response frame 410 to the AP 400. That is, unlike the conventional method of transmitting authentication request frames with a low MCS regardless of the channel state, the data rate can be increased by increasing the transmission speed by adaptively changing the MCS according to channel conditions.
- the AP 400 transmits an authentication response frame 410 to the STA 450.
- the authentication response frame 410 may also be generated and transmitted based on the same MCS as the authentication request frame 465.
- the association request frame 470 is transmitted from the STA 450 to the AP 400, and the association response frame 420 is transmitted from the AP 400 to the STA 450 in response thereto.
- the association request frame 470 and the association response frame 430 may also be generated and transmitted based on the MCS value fed back by the probe response frame 410.
- the probe response frame may serve as NDPA and receive MCS feedback from the STA.
- link adaptation may be performed using the probe response frame 482 as a role of the NDPA frame.
- a probe request frame 492 for performing active scanning in the STA 490 may be transmitted to the AP 480.
- the AP 480 transmits a probe response frame 482 to the STA 490 in response to the probe request frame 492.
- the probe response frame 482 may play the same role as the NDPA frame by adding an NDPA element as an information element of the probe response frame 482. That is, the MCS may be applied from the scanning step by knowing the channel state information in the process of exchanging the initial management frame.
- the NDP frame 484 is transmitted from the AP 480 to the STA 490.
- the AP 480 may transmit the NDP frame 484 to the STA 490 after a predetermined time after transmitting the probe response frame 482.
- the NDP frame 484 may be used for the purpose of feeding back the channel state of the AP 480 receiving the NDP frame 484.
- the authentication request frame 494 is transmitted from the STA 490 to the AP 480.
- an MCS feedback element may be added as a new information element.
- the MCS feedback element may include an MCS feedback value calculated based on the NDP frame 484.
- the AP 480 transmits the authentication response frame 486 generated based on the MCS value fed back from the authentication request frame 494 to the STA 490.
- the data rate can be increased by increasing the transmission speed by adaptively changing the MCS according to the channel condition.
- the STA 490 transmits an association request frame 496 to the AP 480 and transmits an association response frame 488 from the AP 480 to the STA 490 in response thereto.
- association request frame 496 and the association response frame 488 may also be generated and transmitted based on the MCS value fed back by the probe response frame 482.
- an NDPA element is included in an information element of a probe request frame or a probe response frame among management frames used in the scanning / association / authentication step, and the NDP frame is transmitted after a predetermined time.
- the receiving end calculates the MCS feedback based on the received NDP frame, and the calculated MCS feedback is included as an information element of the management frame and transmitted to the transmitting end which transmitted the NDP frame, thereby receiving a frame to which the MCS is applied in the scanning / association / authentication step.
- FIG. 5 is a conceptual diagram illustrating a link adaptation method according to an embodiment of the present invention.
- a probe response frame 510 may also be used as a role of an NDPA frame to perform a plurality of link adaptations in a scanning / association / authentication process. Can be.
- a probe request frame 555 for performing active scanning in the STA 550 may be transmitted to the AP 500.
- the NDPA element may be added as an information element of the probe request frame 555 to allow the probe request frame 515 to play the same role as the NDPA frame.
- the information element of the newly defined probe request frame 555 will be further described below.
- the STA 550 transmits an NDP frame 560 to the AP 500.
- the STA 550 may transmit a NDP frame 560 after transmitting a probe request frame 555 serving as an NDPA frame to the AP 500.
- the NDP frame 560 may be used by the AP 500 receiving the NDP frame 560 to feed back a channel state.
- the probe response frame 510 is transmitted from the AP 500 to the STA 550.
- an MCS feedback element and an NDPA element may be added as new information elements.
- the MCS feedback value calculated based on the NDP frame 560 transmitted by the STA 550 may be transmitted to the STA 550 using the MCS feedback element.
- the link adaptation may be performed once again by adding and transmitting an NDPA element to the information element.
- the information element of the newly defined probe response frame 510 will be further described below.
- the N500 frame 560 is transmitted from the AP 500 to the STA 550.
- the AP 500 may transmit a NDP frame 515 after transmitting a probe response frame 510 serving as an NDPA frame to the STA 550.
- the NDP frame 515 may be used for the STA receiving the NDP frame 515 to feed back the channel state.
- the STA 550 transmits an authentication request frame 565 to the AP 500.
- the STA 550 may include the MCS measured based on the NDP frame 560 transmitted from the AP 500 in the information element of the authentication request frame 565 and transmit the same. Unlike FIG. 4, in FIG. 5, a link adaptation process may be performed twice in a scanning / authentication / association process.
- the information element of the newly defined authentication request frame 565 will be further described below.
- the AP 500 transmits an authentication response frame 520 to the STA 550.
- the authentication response frame 520 may be generated based on the MCS fed back by the authentication request frame 565 and transmitted to the STA 550.
- the STA 550 transmits the association request frame 570 from the STA 500 to the AP 500 and transmits the association response frame 525 from the AP 500 to the STA 550 in response thereto.
- the association request frame 570 and the association response frame 525 may also be generated and transmitted based on the MCS value fed back by the authentication request frame.
- the NDPA element may be included in the management frame used in the scanning / association / authentication process and transmitted after a predetermined time.
- the subsequent frame including the authentication request frame may further include link adaptation by receiving the MCS feedback value after measuring the channel information including the NDPA element.
- Such an embodiment is also included in the scope of the present invention.
- Management frames transmitted and received at the association / authentication stage may be transmitted not only to a single input single output (SISO) but also to multiple input multiple output (MIMO).
- SISO single input single output
- MIMO multiple input multiple output
- FIG. 6 is a conceptual diagram illustrating a link adaptation method using SU-MIMO according to an embodiment of the present invention.
- the AP 600 has four antennas and the STA 650 has four antennas to perform data transmission based on a single user (SU) -MIMO.
- SU-MIMO a plurality of different data streams transmitted by the AP 600 may be transmitted to one STA 650.
- all four antennas are used for spatial multiplexing, four transmission channels exist between the AP 600 and the STA 650.
- the number of spatial streams used to transmit and receive a frame in the MCS feedback information and the channel situation in which each spatial stream is transmitted are determined.
- MCS index may be included. That is, the MCS feedback information may be signal to noise ratio (SNR) information of a channel in a single input single output (SISO) environment, and in the MIMO environment, the number of spatial streams that can be used for data transmission and the MCS for each stream are determined. May be included.
- SNR signal to noise ratio
- the AP 600 determines channel state information of all available MIMO transport stream channels based on the NDP frame transmitted after the probe request frame including the NDPA element.
- the number of spatial streams to be used for obtaining spatial diversity may be determined, and the optimal MCS information may be calculated for each stream and fed back to the STA 650 as an information element of the probe response frame.
- additional feedback information may be received and beamforming may be used.
- FIG. 7 is a conceptual diagram illustrating a data transmission and reception method using beamforming according to an embodiment of the present invention.
- the AP 700 may increase the utilization efficiency and data throughput of a medium by concentrating transmission power to a specific STA 750 using beamforming to transmit data.
- the aforementioned NDP frame may be used to calculate sounding feedback including feedback information for beamforming.
- only a sound feedback element may be used without using an MCS feedback element.
- a spatial stream for each channel may be transmitted by additionally using an MCS feedback element.
- FIG. 7 illustrates data transmission using beamforming based on one spatial stream without performing MIMO.
- the STA 750 may transmit a probe request frame including an NDPA information element to the AP 700 and may transmit an NDP frame after SIFS.
- the AP 700 may perform channel sounding for beamforming based on the NDP frame.
- the AP 700 may calculate a channel sounding result and include the sound feedback element as an information element of the probe response frame and transmit the same.
- the STA 750 may also transmit the beam 700 using beamforming when transmitting to the AP 700.
- a sounding feedback information element transmitted may include a field including feedback information such as a compressed beamforming report field.
- the compressed beamforming report field may include, for example, a beamforming feedback matrix for each subcarrier index, and average SNR information about a spatial stream used for beamforming.
- the STA 750 may perform beamforming by determining the radiation pattern of the antenna, the antenna transmission power, and the like in transmitting the authentication request frame based on the sounding feedback information included in the information element.
- the AP 700 may also transmit the authentication response frame in response to the authentication request frame using beamforming using the calculated sounding feedback information.
- the NDPA element may be included in the information element of the management frame used in the scanning / association / authentication process, and the NDP frame may be transmitted after a predetermined time.
- the receiving end calculates the sounding feedback based on the received NDP frame, and the calculated sounding feedback is included as an information element of the management frame and transmitted to the transmitting end transmitting the NDP frame, which can be used for beamforming.
- FIG. 8 is a conceptual diagram illustrating a data transmission and reception method using beamforming according to an embodiment of the present invention.
- beamforming may be performed while performing SU-MIMO between the AP 800 and the STA.
- SU-MIMO using beamforming may use both MCS feedback information and sounding feedback information as feedback information.
- the AP 800 has three antennas and the STAs 810, 820, and 830 have two antennas.
- the STA 810 may include an NDPA element as an information element of a probe request frame and transmit the same. After SIFS, the STA 810 can transmit the NDP frame to the AP 800 for sounding feedback and MCS feedback.
- the AP 800 may calculate MCS feedback information and sounding feedback information based on the received NDP frame.
- the MCS feedback information and the sounding feedback information may be included in the probe response frame and transmitted to the STA 810.
- the MCS feedback information transmitted to the STA 810 may include, for example, the number of spatial streams that can be used for MIMO and MCS information for each spatial stream.
- the sounding feedback information may include feedback information such as a compressed beamforming report field.
- the compressed beamforming report field may include, for example, a beamforming feedback matrix for each subcarrier index, and average SNR information for each spatial stream used for beamforming. When there is overlapping information among two feedback information, only one feedback information may be included and transmitted.
- the STA 810 may transmit an authentication request frame to the AP 800 through SU-MIMO operation using beamforming based on the feedback information.
- FIG. 8 discloses a method of performing beamforming while performing SU-MIMO between an AP and a STA
- multi-user (MU) MIMO may be performed between one AP and a plurality of STAs.
- the NDPA element may be included in the information element of the management frame used in the scanning / association / authentication process, and the NDP frame may be transmitted after a predetermined time.
- the receiving end calculates MCS feedback and sounding feedback based on the received NDP frame, and the calculated MCS feedback and sounding feedback are included as information elements of the management frame, and are transmitted to the transmitting end which transmitted the NDP frame, thereby receiving a plurality of spatial streams. It can be used for link adaptation and beamforming.
- an embodiment of the present invention shows an element added to an information element according to a role of a management frame used in a scanning / association / authentication process.
- the role of the NDPA frame in the probe request frame it is assumed that the role of the NDPA frame in the probe request frame. It is assumed that MCS feedback and sounding feedback are performed on the NDPA information element of the probe request frame while replaying the role of the NDPA frame in the probe response frame.
- the authentication request frame is assumed to perform MCS feedback and sounding feedback on the NDPA element of the probe request frame.
- a role played in the corresponding frame is limited to a part, only an information element for performing only the corresponding role may be included in the management frame.
- a probe request frame serving as an NDPA transmitted from an STA used in the scanning step may include information elements as shown in Table 1 below.
- NDPA may be newly defined as an information element included in a data field of a prove request frame.
- the order for each information element in Table 1 may be changed to arbitrary.
- the information element may indicate information included in the framebody of the frame.
- Each information element of a probe request frame is disclosed in IEEE 802.11 8.3.3.9.
- the NDPA may be additionally included in the information element of the probe response frame.
- FIG. 9 is a conceptual diagram illustrating an NDPA element format according to an embodiment of the present invention.
- the NDPA element format may include an element ID 900, a length 920, NDP information 940, and STA information 960.
- the element ID 900 may be assigned to a bit of 1 octet (8) as a value indicating what information the information element is.
- the length 920 is a value representing the length of the information element and may be allocated to 1 octet of bits.
- the NDP information 940 may include an NDPA indication 940-1 and a sequence number 940-5.
- the NDPA indication 940-1 may indicate that the frame is a frame serving as the NDPA.
- the sequence number 940-5 may be information used when the NDP frame plays a role of sounding and may include sounding sequence number information. If the NDP frame does not play a role for calculating sounding feedback but only serves for MCS feedback, the corresponding bit may be used to convey other information.
- the NDPA may be included in the information element of the probe response frame.
- the STA information 960 may include a feedback type 960-3, a beamforming 960-6, and an Nc Index 960-9.
- the feedback type 960-3 may include information on whether to provide feedback for the NDP frame to a single user or feedback to multiple users.
- the beamforming 960-6 may include information on whether to perform beamforming when using MIMO. When receiving an NDPA frame, it may be determined whether to perform feedback on beamforming based on the beamforming 960-6.
- the Nc Index 960-9 may include a required feedback dimension when performing beamforming.
- the STA information 960 may not be used when only the MCS feedback is provided at the receiving end based on the NDP frame without performing beamforming.
- the AP may include feedback information on the NDP frame transmitted from the STA in the information element and transmit the feedback information in the probe response frame.
- Tables 2 to 4 show information elements of a probe response frame including MCS feedback and sound feedback to perform feedback on information elements and NDPA to perform the role of NDPA.
- NDPA in order 40 MCS feedback in order 41, and sounding feedback in order 42 may be included.
- the information element may include only some information elements of NDPA, MCS feedback, and sounding feedback depending on the role of the probe request frame.
- a probe response frame when used as the role of NDPA, only the NDPA except for MCS feedback and sounding feedback may be included in the information element.
- a probe response frame serving as an NDPA does not serve as a probe request frame but serves as an NDPA and performs an MCS feedback on an NDP frame, only an MCS feedback is used as an information element. It may include.
- the authentication request frame may serve to transmit MCS feedback information to the AP, and in this case, the information element of the authentication request frame MCS feedback or sounding feedback may be additionally included.
- FIGS. 10 and 11 are conceptual diagrams illustrating an MCS feedback information element and a sounding feedback element according to an embodiment of the present invention.
- the MCS feedback may include an element ID 1000, a length 1020, a number of spatial streams 1040, and an MCS index 1060.
- the element ID 1000 includes ID information of an information element of MCS feedback, and length 1020 includes information about the length of the MCS feedback information element.
- the number of spatial streams (1040) may include information on the number of available spatial streams when MIMO is available. It may include.
- the sounding feedback may include an element ID 1100, a length 1120, and a compressed beamforming report 1140.
- the element ID 1100 includes ID information of an information element of sounding feedback and the length 1120 includes information about the length of the sounding feedback information element.
- the compressed beamforming report 1140 may include feedback information for performing beamforming, such as a signal to noise ratio (SNR) and a beamforming feedback matrix, for each spatial-time stream.
- SNR signal to noise ratio
- a beamforming feedback matrix for each spatial-time stream.
- Table 5 shows an information element of an authentication request frame that performs MCS feedback and sounding feedback on an NDPA element of a probe request frame.
- MCS feedback in order 10 and sounding feedback in order 11 may be included.
- the AP may calculate MCS feedback and sounding feedback and include the information in an information element and transmit the same to the STA.
- FIG. 12 is a block diagram illustrating a wireless device to which an embodiment of the present invention can be applied.
- the wireless device 70 is a terminal capable of implementing the above-described embodiments and may be an AP or a non-AP STA.
- Wireless device 70 includes a processor 72, a memory 74, and a transceiver 76.
- the transceiver 76 transmits / receives a radio signal, but implements a physical layer of IEEE 802.11.
- the processor 72 is functionally connected to the transceiver 76 to implement the MAC layer and the physical layer of IEEE 802.11.
- the processor 72 may generate a frame according to an embodiment of the present invention.
- the transceiver 76 transmits a probe request frame including a null data packet announcement (NDPA) information element and transmits a probe request frame and then physical layer convergence (PLCP).
- NDPA null data packet announcement
- PLCP physical layer convergence
- a NDP (null data packet) frame including only a protocol header may be transmitted, and a probe response frame including an feedback information element calculated based on the NDP frame may be received. That is, each component of the wireless device 70 may be implemented to practice the present invention.
- Processor 72 and / or transceiver 76 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices.
- Memory 74 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices.
- ROM read-only memory
- RAM random access memory
- flash memory memory cards, storage media, and / or other storage devices.
- the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function.
- the module is stored in the memory 74 and can be executed by the processor 72.
- the memory 74 may be internal or external to the processor 72 and may be coupled to the processor 72 by various well-known means.
Abstract
Description
Claims (12)
- 링크 어뎁테이션 방법에 있어서, 상기 링크 어뎁테이션 방법은,
NDPA(null data packet announcement) 정보 요소(information element)를 포함하는 프로브 리퀘스트 프레임(probe request frame)을 전송하는 단계;
상기 프로브 리퀘스트 프레임(probe request frame)을 전송한 후에 PLCP(physical layer convergence protocol) 헤더만을 포함하는 NDP(null data packet) 프레임을 전송하는 단계; 및
상기 NDP 프레임에 기초하여 산출된 피드백 정보 요소(information element)를 포함하는 프로브 리스폰스 프레임(probe response frame)을 수신하는 단계를 포함하되,
상기 NDPA 정보 요소(information element)는 상기 프로브 리퀘스트 프레임(probe request frame)이 NDPA 프레임(frame)의 역할을 수행하는지 여부를 지시하는 NDP 정보(information)를 포함하고,
상기 피드백 정보 요소(information element)는 MCS(modulation and coding scheme) 피드백(feedback) 정보 및 사운딩 피드백(sounding feedback) 정보 중 적어도 하나를 포함하는 링크 어뎁테이션 방법. - 제1항에 있어서, 상기 링크 어뎁테이션 방법은,
상기 프로브 리스폰스 프레임(probe response frame)이 NDPA 정보 요소(information element)를 포함한 경우, 상기 프로브 리스폰스 프레임(probe response frame)을 수신한 후 NDP 프레임을 수신하는 단계; 및
상기 NDP 프레임에 기초하여 피드백 정보 요소(information element)를 포함하는 인증 요청 프레임(authentication request frame)을 전송하는 단계를 더 포함하되,
상기 피드백 정보 요소(information element)는 MCS 피드백(feedback) 정보 및 사운딩 피드백(sounding feedback) 정보 중 적어도 하나를 포함하는 링크 어뎁테이션 방법. - 제1항에 있어서, 상기 NDPA 정보 요소(information element)는 피드백 타입, 빔포밍, Nc 인덱스(Nc index)를 더 포함하고,
상기 피드백 타입은 피드백 정보가 단일 사용자(single user)에게 전송되는지 아니면 복수의 사용자(multiple user)에게 전송되는지를 나타내는 지시자이고,
상기 빔포밍은 빔포밍이 수행되는지 여부를 나타내는 지시자이고,
상기 Nc 인덱스(Nc index)는 상기 빔포밍을 사용할 경우 요구되는 피드백 차원(dimension)을 나타내는 지시자인 링크 어뎁테이션 방법. - 제1항에 있어서, 상기 MCS 피드백 정보는 공간 스트림(spatial stream)의 개수, MCS 인덱스를 포함하고,
상기 공간 스트림(spatial stream)의 개수는 전송에 사용되는 공간 스트림(spatial stream)의 개수를 나타내는 지시자이고,
상기 MCS 인덱스는 전송에 사용되는 변조 및 코디 방법(modulation and coding scheme)을 나타내는 지시자인 링크 어뎁테이션 방법. - 제1항에 있어서, 상기 사운딩 피드백(sounding feedback) 정보는 컴프레스트 빔포밍 리포트(compressed beamforming report)를 포함하고,
상기 컴프레스드 빔포밍 리포트(compressed beamforming report)는 각각의 공간 스트림(spatial stream)에 대한 SNR(signal to noise ratio) 및 적어도 하나의 빔포밍 메트릭스(beamforming matrix)를 포함하는 링크 어뎁테이션 방법. - 제1항에 있어서, 상기 링크 어뎁테이션 방법은,
상기 MCS feedback 정보를 기초로 빔포밍(beamforming)을 사용한 MIMO(multiple input multiple output) 전송 방법에 의해 인증 요청 프레임(authentication request frame)을 전송하는 단계를 더 포함하는 링크 어뎁테이션 방법. - 링크 어뎁테이션을 수행하는 무선 단말에 있어서,
상기 무선 단말은 트랜시버(transceiver)를 포함하고, 상기 트렌시버는 NDPA(null data packet announcement) 정보 요소(information element)를 포함하는 프로브 리퀘스트 프레임(probe request frame)을 전송하고,
상기 프로브 리퀘스트 프레임(probe request frame)을 전송한 후에 PLCP(physical layer convergence protocol) 헤더만을 포함하는 NDP(null data packet) 프레임을 전송하고
상기 NDP 프레임에 기초하여 산출된 피드백 정보 요소(information element)를 포함하는 프로브 리스폰스 프레임(probe response frame)을 수신하도록 구현되되,
상기 NDPA 정보 요소(information element)는 상기 프로브 리퀘스트 프레임(probe request frame)이 NDPA 프레임(frame)의 역할을 수행하는지 여부를 지시하는 NDP 정보(information)를 포함하고,
상기 피드백 정보 요소(information element)는 MCS(modulation and coding scheme) 피드백(feedback) 정보 및 사운딩 피드백(sounding feedback) 정보 중 적어도 하나를 포함하는 무선 단말. - 제7항에 있어서, 상기 트렌시버는,
상기 프로브 리스폰스 프레임(probe response frame)이 NDPA 정보 요소(information element)를 포함한 경우, 상기 프로브 리스폰스 프레임(probe response frame)을 수신한 후 NDP 프레임을 수신하고,
상기 NDP 프레임에 기초하여 피드백 정보 요소(information element)를 포함하는 인증 요청 프레임(authentication request frame)을 전송하도록 구현되되,
상기 피드백 정보 요소(information element)는 MCS 피드백(feedback) 정보 및 사운딩 피드백(sounding feedback) 정보 중 적어도 하나를 포함하는 무선 단말. - 제7항에 있어서, 상기 NDPA 정보 요소(information element)는 피드백 타입, 빔포밍, Nc 인덱스(Nc index)를 더 포함하고,
상기 피드백 타입은 피드백 정보가 단일 사용자(single user)에게 전송되는지 아니면 복수의 사용자(multiple user)에게 전송되는지를 나타내는 지시자이고,
상기 빔포밍은 빔포밍이 수행되는지 여부를 나타내는 지시자이고,
상기 Nc 인덱스(Nc index)는 상기 빔포밍을 사용할 경우 요구되는 피드백 차원(dimension)을 나타내는 지시자인 무선 단말. - 제7항에 있어서, 상기 MCS 피드백 정보는 공간 스트림(spatial stream)의 개수, MCS 인덱스를 포함하고,
상기 공간 스트림(spatial stream)의 개수는 전송에 사용되는 공간 스트림(spatial stream)의 개수를 나타내는 지시자이고,
상기 MCS 인덱스는 전송에 사용되는 변조 및 코디 방법(modulation and coding scheme)을 나타내는 지시자인 무선 단말. - 제7항에 있어서, 상기 사운딩 피드백(sounding feedback) 정보는 컴프레스트 빔포밍 리포트(compressed beamforming report)를 포함하고,
상기 컴프레스드 빔포밍 리포트(compressed beamforming report)는 각각의 공간 스트림(spatial stream)에 대한 SNR(signal to noise ratio) 및 적어도 하나의 빔포밍 메트릭스(beamforming matrix)를 포함하는 무선 단말. - 제7항에 있어서, 상기 트랜시버는,
상기 MCS feedback 정보를 기초로 빔포밍(beamforming)을 사용한 MIMO(multiple input multiple output) 전송 방법에 의해 인증 요청 프레임(authentication request frame)을 전송하도록 구현된 무선 단말.
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