METHOD AND APPARATUS FOR TRANSMITTING DOWNLINK IN WIRELESS COMMUNICATION SYSTEM

• US 20150365972A1
• Filed: 02/05/2014
• Published: 12/17/2015
• Est. Priority Date: 02/05/2013
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: SEOK, Yongho
• Granted Patent: US 10,342,045 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04W 74/0816 with collision avoidance
• CPC Class Codes: H04W 74/0891 for synchronized access
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Disclosed are a method and an apparatus for transmitting a downlink in a wireless communication system. A method for transmitting the downlink in a WLAN comprises the steps of: an access point (AP) transmitting, to a plurality of stations (STA), each of a plurality of request to send (RTS) frames through each of a plurality of channels; and the AP receiving a clear to send (CTS) frame from at least one of the plurality of STAs through at least one channel from the plurality of channels, wherein each of the plurality of RTS frames may include channel information for indicating a channel to be used from among the plurality of channels when transmitting the downlink to each of the STAs, and identifier information for indicating the plurality of STAs.

Claims

1. A method for transmitting a downlink in a wireless local area network (WLAN), the method comprising:

transmitting, by an access point (AP), each of a plurality of request to send (RTS) frames to each of a plurality of stations (STAs) through each of a plurality of channels; and

receiving, by the AP, a clear to second (CTS) frame from at least one of the plurality of STAs through at least one channel of the plurality of channels,

wherein each of the plurality of RTS frames includes channel information indicating a channel to be used when performing the downlink transmission to the plurality of STAs among the plurality of channels and identifier information indicating the plurality of STAs.

2. The method of claim 1, further comprising:

wherein the CTS frame is transmitted from at least two STAs of the plurality of STAs to the AP through at least two channels of the plurality of channels,

transmitting, by the AP, a plurality of data frames to the at least two STAs of the plurality of STAs,

wherein each of the plurality of data frames are transmitted to correspond to the at least two STAs of the plurality of STAs.

3. The method of claim 2,

wherein a time when the transmission of the plurality of data frames ends is the same as a time when transmission of a maximum interval transmission data frame ends,

wherein the maximum interval transmission data frame is a frame in which effective downlink data is transmitted by the AP during the longest interval, and

wherein residual data frames other than the maximum interval transmission data frame among the plurality of data frames are null-padded.

4. The method of claim 3, wherein the null padding includes a repeated MPDU delimiter field in which a MAC protocol data unit (MPDU) length field is configured as 0.

5. The method of claim 2,

wherein each of the plurality of data frames includes at least one long training field (LTF) used for channel prediction,

wherein the number of LTFs included in each of the plurality of data frames is determined based on the largest number of spatial streams, and

wherein the spatial stream is used to transmit at least two data streams among the plurality of data frames to a specific STA based on multiple input multiple output (MIMO).

6. The method of claim 1,

wherein one of the plurality of channels is a primary channel and the residual channels are secondary channels,

wherein the AP performs back-off only in the primary channel, and

wherein the plurality of channels include 20 MHz channels

wherein a number of the 20 MHz channels is 8.

7. The method of claim 1,

wherein the identifier information indicating the plurality of STAs includes a partial AID value other than 1 bit corresponding to a most significant bit (MSB) among association identifiers (AIDs) of each of the plurality of STAs.

8. An access point (AP) transmitting a downlink in a wireless local area network (WLAN), the AP comprising:

a radio frequency (RF) unit configured to transmit and receive a radio signal;

a processor configured to;

transmit each of a plurality of request to send (RTS) frames to each of a plurality of stations (STAs) through each of a plurality of channels; and

receive a clear to second (CTS) frame from at least one of the plurality of STAs through at least one channel of the plurality of channels,

wherein each of the plurality of RTS frames includes channel information indicating a channel to be used when performing the downlink transmission to the plurality of STAs among the plurality of channels and identifier information indicating the plurality of STAs.

9. The AP of claim 8,

wherein the CTS frame is transmitted from at least two STAs of the plurality of STAs to the AP through at least two channels of the plurality of channels,

wherein the processor is configured to transmit a plurality of data frames to the at least two STAs of the plurality of STAs,

wherein each of the plurality of data frames are transmitted to correspond to the at least two STAs of the plurality of STAs.

10. The AP of claim 9,

wherein a time when the transmission of the plurality of data frames ends is the same as a time when transmission of a maximum interval transmission data frame ends,

wherein the maximum interval transmission data frame is a frame in which effective downlink data is transmitted by the AP during the longest interval, and

wherein residual data frames other than the maximum interval transmission data frame among the plurality of data frames are null-padded.

11. The AP of claim 10, wherein the null padding includes a repeated MPDU delimiter field in which a MAC protocol data unit (MPDU) length field is configured as 0.

12. The AP of claim 9,

wherein each of the plurality of data frames includes at least one long training field (LTF) used for channel prediction,

wherein the number of LTFs included in each of the plurality of data frames is determined based on the largest number of spatial streams, and

wherein the spatial stream is used to transmit at least two data streams among the plurality of data frames to a specific STA based on multiple input multiple output (MIMO).

13. The AP of claim 8,

wherein one of the plurality of channels is a primary channel and the residual channels are secondary channels,

wherein the AP performs back-off only in the primary channel, and

wherein the plurality of channels include 20 MHz channels

wherein a number of the 20 MHz channels is 8.

14. The AP of claim 8,

wherein the identifier information indicating the plurality of STAs includes a partial AID value other than 1 bit corresponding to a most significant bit (MSB) among association identifiers (AIDs) of each of the plurality of STAs.