A-10 (Leutert) WLAN 802.11n MIMO Analysis - Sharkfest - Wireshark
A-10 (Leutert) WLAN 802.11n MIMO Analysis - Sharkfest - Wireshark A-10 (Leutert) WLAN 802.11n MIMO Analysis - Sharkfest - Wireshark
Block-ACK MechanismRather than sending an individual acknowledgefollowing each data frame, 802.11n introduces thetechnique of confirming a burst of up to 64 frameswith a single Block ACK (BA) frameThe Block ACK even contains a bitmap to selectivelyacknowledge individual frames of a burst(comparable to selective acknowledges of TCP)The use of combined acknowledges can berequested by sending a Block ACK Request (BAR)SHARKFEST ‘10 | Stanford University | June 14 –17, 2010
Block-ACK Mechanism (cont.)A-MPDUsBlock ACKSequence # 1 2 3 4 61 62 63 64Bitmap (64 bits)Start Sequence # 1 + 1111 1111 …. 1111 1111= 65lost frameA-MPDUsBlock ACKSequence # 65 66 67 68 125 126 127 128Bitmap (64 bits)Start Sequence # 65 + 1111 1111 …. 1111 1011= 129retransmitted frameA-MPDUsBlock ACKSequence # 126 129 130 131 188 189 190 191Bitmap (64 bits)Start Sequence # 128 + 1111 1111 …. 1111 1111= 192SHARKFEST ‘10 | Stanford University | June 14 –17, 2010
- Page 1 and 2: WLAN 802.11n MIMO AnalysisJune 17,
- Page 3 and 4: Design Goals for 802.11n• IEEE 80
- Page 5 and 6: PHY layer improvementsModified OFDM
- Page 7 and 8: Channel Bonding (Channel 6 & 10)Rec
- Page 9 and 10: Channel Bonding (configuration)802.
- Page 11 and 12: Multi-Streaming Modulation802.11a/g
- Page 13 and 14: MCS Configuration1 spatial stream 2
- Page 15 and 16: MAC layer improvementsFrame Aggrega
- Page 17: A-MSDU AnalysisAll trace files made
- Page 22 and 23: Block-ACK Bitmap AnalysisSHARKFEST
- Page 24 and 25: Block-ACK negotiation/activationThe
- Page 26 and 27: New HT Capabilities in Beacon Frame
- Page 28 and 29: Per-Packet Information Header (cont
- Page 30 and 31: AirPcap Nx and WiresharkAirPcap Nx
- Page 32 and 33: Analysing ‘Bad BAR’ problemSHAR
- Page 34 and 35: Analysing ‘Deadlock’ problemPro
- Page 36 and 37: Analysing ‘Deadlock’ problem (c
- Page 38 and 39: Backwards compatibility to a/b/gPre
- Page 40 and 41: Backwards compatibility to a/b/g (c
- Page 42 and 43: Future of 802.11nStandard has been
Block-ACK Mechanism (cont.)A-MPDUsBlock ACKSequence # 1 2 3 4 61 62 63 64Bitmap (64 bits)Start Sequence # 1 + 1111 1111 …. 1111 1111= 65lost frameA-MPDUsBlock ACKSequence # 65 66 67 68 125 126 127 128Bitmap (64 bits)Start Sequence # 65 + 1111 1111 …. 1111 <strong>10</strong>11= 129retransmitted frameA-MPDUsBlock ACKSequence # 126 129 130 131 188 189 190 191Bitmap (64 bits)Start Sequence # 128 + 1111 1111 …. 1111 1111= 192SHARKFEST ‘<strong>10</strong> | Stanford University | June 14 –17, 20<strong>10</strong>
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