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20MHz Protection Mode

20MHz Protection Mode. Authors:. Date: 2008-08-05. Current 20MHz Protection Mode in 11n Draft. A 20MHz HT STA can not decode the received 40MHz HT frame, it invokes EIFS to protect the response transmission (See the resolution to comment 7040 in [1]). AP1. AP1. 40MHzAP/STA.

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20MHz Protection Mode

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  1. 20MHz Protection Mode Authors: Date: 2008-08-05 L. Chu Etc.

  2. Current 20MHz Protection Mode in 11n Draft • A 20MHz HT STA can not decode the received 40MHz HT frame, it invokes EIFS to protect the response transmission (See the resolution to comment 7040 in [1]). AP1 AP1 40MHzAP/STA 40MHzData (STA1) 40MHzData (STA1) 20MHzSTA STA1 ACK ACK STA1 STA2 EIFS EIFS STA2 Received corrupted frame L. Chu Etc.

  3. EIFS EIFS Normal ACK Protection in 20/40MHz Infrastructure BSS • EIFS based protection does not work if 40MHz AP1 is the receiver. • Using NAV based protection, this will not occur. STA1 40MHzData (STA1) 40MHzData (STA1) RTS AP1 ACK CTS AP1 40MHzAP/STA Data (AP1) STA2 20MHzSTA Backoff Backoff Failed normal ACK protection based on EIFS STA1 STA2 Received corrupted frame L. Chu Etc.

  4. EIFS BlockAck Protection in 20/40MHz Infrastructure BSS • EIFS-based protection can not protect BlockAck transmission. • Using NAV based protection, this will not occur. AP1 40MHzAP/STA 20MHzSTA STA1 STA2 BLKREQ STA1 Data (AP1) Data (AP1) Data (AP1) RTS AP1 CTS Data (AP1) Data (AP1) STA2 Backoff No ACK Backoff Failed blockack protection based on EIFS Received corrupted frame L. Chu Etc.

  5. EIFS-based protection can not protect PSMP transmission. Using NAV based protection, this will not occur.. EIFS PSMP in 20/40MHz Infrastructure BSS AP1 40MHzAP/STA 20MHzSTA STA1 STA2 PSMP AP1 40MHz A-MPDU (STA1) MTBA 40MHz A-MPDU (AP1) STA1 Data (AP1) STA2 Backoff Failed blockack protection based on EIFS Received corrupted frame L. Chu Etc.

  6. Different Protection Levels Between 20MHz Protection and Non-HT Protection • If 20MHz protection can use EIFS, non-HT protection can also use EIFS. • 11n does not need to invent new non-HT protection features. • But actually 11n introduces new non-HT protection features. • So 11n should provide stronger 20MHz protection. 40MHz AP1 AP1 40MHzData (STA1) 40MHzData (STA1) STA1 ACK ACK EIFS EIFS STA2 40MHz STA1 20MHz STA2 Received corrupted frame HT-AP1 AP1 HT frame (STA1) HT frame (STA1) STA1 ACK ACK EIFS EIFS STA2 HT-STA1 Non-HT STA2 L. Chu Etc.

  7. In a 20/40MHz infrastructure BSS, before transmitting a 40MHz HT frame, a STA or the AP shall first transmit a 20MHz HT frame in the primary channel. OR In a 20/40MHz infrastructure BSS, before transmitting a 40MHz HT frame, a STA or the AP shall first transmit a 40MHz non-HT duplicate frame. Proposed 20MHz Protection in 20/40MHz Infrastructure BSS L. Chu Etc.

  8. [1] 11-08/0746r2, “COEX LB129 20-40”, Matthew Fischer Reference L. Chu Etc.

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