# US 11,452,135 B2 · Method and device for transmitting and receiving PPDU on basis of FDD in wireless LAN system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,452,135 B2 - Document ID: US11452135B2 - Status: Granted - Kind: B2 - Application number: 17/052,165 - Filed: 2019-05-23 - Published: 2021-05-13 - Granted: 2022-09-20 - Earliest claimed: 2018-05-23 - Assignees: LG Electronics Inc. - Applicants: LG Electronics Inc. - Inventors: Jinmin Kim - Web page: https://patentgrep.com/patent/US11452135B2 ## CPC - H04W 74/06: using polling - H04W 74/0816: with collision avoidance - H04L 1/1621: {Group acknowledgement, i.e. the acknowledgement message defining a range of identifiers, e.g. of sequence numbers} - H04L 1/1664: {the supervisory signal being transmitted together with payload signals; piggybacking} - H04L 5/0053: {Allocation of signalling, i.e. of overhead other than pilot signals} - H04L 5/14: Two-way operation using the same type of signal, i.e. duplex - H04L 27/2603: {Signal structure ensuring backward compatibility with legacy system} - H04L 1/0003: {by switching between different modulation schemes} - H04L 1/0025: {Transmission of mode-switching indication} - H04W 84/12: WLAN [Wireless Local Area Networks] - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method and a device for transmitting and receiving a PPDU on the basis of an FDD in a wireless LAN system are presented. Particularly, an AP transmits a trigger frame to a first STA and a second STA. The AP transmits a first downlink (DL) PPDU to the first STA on the basis of the trigger frame. The AP transmits a second DL PPDU to the second STA on the basis of the trigger frame. The AP receives a first uplink (UL) PPDU from the second STA on the basis of the trigger frame. The trigger frame includes bandwidth information of a primary channel and a secondary channel. The first DL PPDU is transmitted through the primary channel. The second DL PPDU and the first UL PPDU are transmitted through the secondary channel. The first and second DL PPDU are simultaneously transmitted. The first UL PPDU is received after a preset period after the second DL PPDU is transmitted. ## Claims ### Claim 1 A method in a wireless local area network (WLAN) system, the method comprising: transmitting, by an access point (AP) supporting a primary channel and a secondary channel, a first downlink (DL) PPDU to a first STA; and receiving, by the AP, a first uplink (UL) PPDU from a second STA, wherein the first DL PPDU is transmitted through the primary channel while the first UL PPDU is received through the secondary channel. ### Claim 2 (depends on 1) The method of claim 1, further comprising: transmitting, by the AP, a second DL PPDU to the second STA, wherein the first DL PPDU comprises a first preamble and a first data field, wherein the second DL PPDU comprises only a second preamble or comprises the second preamble and a quality of service (QoS) null frame, and wherein the second preamble is a preamble obtained by duplicating the first preamble. ### Claim 3 (depends on 2) The method of claim 2, wherein the second preamble comprises a legacy-short training field (L-STF), a legacy-long training field (L-LTF), a legacy-signal (L-SIG), and an FDD-signal (FDD-SIG), and wherein the FDD-SIG comprises bandwidth information of the primary channel and secondary channel. ### Claim 4 (depends on 1) The method of claim 1, wherein the pre-set duration is set to a first duration or a second duration, wherein the first duration is a short inter-frame space (SIFS), and wherein the second duration is a duration having a value greater than the SIFS and less than a point coordination function inter-frame space (PIFS). ### Claim 5 (depends on 1) The method of claim 1, wherein the first UL PPDU comprises only a second data field, or comprises only an ACK frame for the first DL PPDU, or comprises a frame obtained by aggregating the second data field and the ACK frame, and wherein the ACK frame comprises a block Ack (BA) frame. ### Claim 6 (depends on 5) The method of claim 5, wherein the first UL PPDU does not include an ACK frame for the second DL PPDU, and wherein the ACK frame for the second DL PPDU is not required. ### Claim 7 (depends on 3) The method of claim 3, wherein a transmission end time of the first UL PPDU is equal or prior to a transmission end time of the first DL PPDU, and wherein the L-SIG comprises information on the transmission end time of the first DL PPDU. ### Claim 8 (depends on 1) The method of claim 1, further comprising: transmitting, by the AP, a trigger frame to the first STA and the second STA, wherein the trigger frame comprises bandwidth information of the primary channel and the secondary channel, information on a center frame, a channel number of the primary channel and secondary channel, indication information of DL and UL PPDUs, duration information of the DL and UL PPDUs, and transmission opportunity (TXOP) information of the DL and UL PPDUs, and wherein the trigger frame further comprises a first trigger frame transmitted in the primary channel and a second trigger frame transmitted in the secondary channel. ### Claim 9 (depends on 8) The method of claim 8, wherein the second trigger frame is obtained by duplicating the first trigger frame. ### Claim 10 (depends on 8) The method of claim 8, wherein if the second trigger frame is aggregated with a physical layer service data unit (PSDU) comprised in the second DL PPDU, the first UL PPDU is received when an SIFS elapses after the trigger frame is transmitted. ### Claim 11 An access point (AP) supporting a primary channel and a secondary channel in a wireless local area network (WLAN) system, the AP comprising: a memory; a transceiver; and a processor operatively coupled to the memory and the transceiver, wherein the processor is configured to: transmit a first downlink (DL) PPDU to a first STA; and receive a first uplink (UL) PPDU from a second STA, wherein the first DL PPDU is transmitted through the primary channel while the first UL PPDU is received through the secondary channel. ### Claim 12 (depends on 11) The wireless device of claim 11, wherein the processor is further configured to: transmit a second DL PPDU to the second STA, wherein the first DL PPDU comprises a first preamble and a first data field, wherein the second DL PPDU comprises only a second preamble or comprises the second preamble and a quality of service (QoS) null frame, and wherein the second preamble is a preamble obtained by duplicating the first preamble. ### Claim 13 (depends on 12) The wireless device of claim 12, wherein the second preamble comprises a legacy-short training field (L-STF), a legacy-long training field (L-LTF), a legacy-signal (L-SIG), and an FDD-signal (FDD-SIG), and wherein the FDD-SIG comprises bandwidth information of the primary channel and secondary channel. ### Claim 14 (depends on 11) The wireless device of claim 11, wherein the pre-set duration is set to a first duration or a second duration, wherein the first duration is a short inter-frame space (SIFS), and wherein the second duration is a duration having a value greater than the SIFS and less than a point coordination function inter-frame space (PIFS). ### Claim 15 (depends on 11) The wireless device of claim 11, wherein the first UL PPDU comprises only a second data field, or comprises only an ACK frame for the first DL PPDU, or comprises a frame obtained by aggregating the second data field and the ACK frame, and wherein the ACK frame comprises a block Ack (BA) frame. ### Claim 16 (depends on 15) The wireless device of claim 15, wherein the first UL PPDU does not include an ACK frame for the second DL PPDU, and wherein the ACK frame for the second DL PPDU is not required. ### Claim 17 (depends on 13) The wireless device of claim 13, wherein a transmission end time of the first UL PPDU is equal or prior to a transmission end time of the first DL PPDU, and wherein the L-SIG comprises information on the transmission end time of the first DL PPDU. ### Claim 18 (depends on 11) The wireless device of claim 11, wherein the processor is further configured to: transmit a trigger frame to the first STA and the second STA, wherein the trigger frame further comprises bandwidth information of the primary channel and the secondary channel, information on a center frame, a channel number of the primary channel and secondary channel, indication information of DL and UL PPDUs, duration information of the DL and UL PPDUs, and transmission opportunity (TXOP) information of the DL and UL PPDUs, and wherein the trigger frame further comprises a first trigger frame transmitted in the primary channel and a second trigger frame transmitted in the secondary channel. ### Claim 19 (depends on 18) The wireless device of claim 18, wherein the second trigger frame is obtained by duplicating the first trigger frame.