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802.11 PCF Model Progress Update Nov 2000

802.11 PCF Model Progress Update Nov 2000. Author: Matthew Sherman AT&T Labs - Research 180 Park Avenue Florham Park, NJ 07932 973-236-6791 mjsherman@att.com. Date: November 8, 2000. Introduction / Background. Prior descriptions in: IEEE 802.11-00/264r1 IEEE 802.11-00/318r1

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802.11 PCF Model Progress Update Nov 2000

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  1. 802.11 PCF Model Progress Update Nov 2000 Author: Matthew Sherman AT&T Labs - Research 180 Park Avenue Florham Park, NJ 07932 973-236-6791 mjsherman@att.com Date: November 8, 2000 Matthew Sherman, AT&T Labs - Research

  2. Introduction / Background • Prior descriptions in: • IEEE 802.11-00/264r1 • IEEE 802.11-00/318r1 • PCF model developed by AT&T Labs • Validation still required • Jumping off point for MAC enhancements • Currently available under NDA from AT&T • May become part of OPNET Standard Library • Eventual contributed model with enhancements • No NDA for contributed model Matthew Sherman, AT&T Labs - Research

  3. Mods Since Sept ‘00 Meeting • Implemented more_data bit in frame format • PCF use only • Streamlined frame formats • New packet formats called: • Wlan_mac_pcf • Wlan_control_pcf • Added all possible fields that might be needed for data / management frames • Reduced Control Frame fields since some irrelevant • Fix to beacon header size • Off by 6 bytes • Receiver busy / SIFS fix • Receiver busy now ignored during SIFS Matthew Sherman, AT&T Labs - Research

  4. Mods Since Sept ‘00 Meeting (Cont.) • Fixed frame timeout for PCF side traffic • AP was not waiting long enough for traffic • EIFS fix • Was still being set in NAV for some cases • PCF Duration field fixes • Was setting to 0 rather than 32768 • AP NAV reset at start of CFP • May reconsider later • Option to reset NAV for CF_END for all BSSs or only own BSS • NS Compatible trace capability • Update to October models capability Matthew Sherman, AT&T Labs - Research

  5. Mods Since Sept ‘00 Meeting (Cont.) • Assorted Retry fixes • Wrong frame type, duration filed, trace info, etc. • Added support for multi-source model • “Ghost Packet” and other receiver fixes • TBTT overrun fix • Max packet size fix • Broadcast packet CW reset fix • Fragment train before Beacon Fix • Various other minor fixes • PCF poll flag fixes • sometimes PCF active flag was set by mistake Matthew Sherman, AT&T Labs - Research

  6. Current Scenario Simulated • Based on most current “Model 3 Scenario” • Modified Video Conference packet generation • Packets were too large • Added bulk traffic stream 10 sec into simulation • Load system beyond channel capacity • Addresses assigned to favor higher priority traffic • Addresses used as AID by poll scheduler • Will update scenario to final “Model 3” once completed • MPEG sources • Finalize Video Conference and data streams Matthew Sherman, AT&T Labs - Research

  7. OPNET Scenario Matthew Sherman, AT&T Labs - Research

  8. MAC Parameters Matthew Sherman, AT&T Labs - Research

  9. Traffic Sources Matthew Sherman, AT&T Labs - Research

  10. Global Stats PCF DCF Matthew Sherman, AT&T Labs - Research

  11. Global Stats • 100 values / bin in simulations • Groups of values (100) are processed at a time to generate displayed statistics • Global Stats are aggregate values across all streams • Delay is time from when packet queued in MAC until final Ack indicating successful delivery • Load is traffic presented to MAC from upper layers • Media Access Delay is time from packet queued in MAC until first access of medium • Throughput is traffic forwarded to upper layers • Packets dropped self explanatory Matthew Sherman, AT&T Labs - Research

  12. Global Stats - Performance • PCF outperforming DCF from start • Some packet drops on DCF, none on PCF • PCF delays lower • See effects of Bulk data kick in at 10 sec • Large number of packet drops • Delays start getting really bad • Throughput on PCF increases slightly when Bulk data starts • Throughput on DCF seems to slightly decrease • More retrys / backoffs Matthew Sherman, AT&T Labs - Research

  13. Dropped Packets Voice Voice Voice Audio Ack Bulk Data Audio Video Conf. Video Conf. MPEG Data Ack PCF DCF Matthew Sherman, AT&T Labs - Research

  14. Dropped Packets • Clearly see that DCF is dropping MPEG traffic almost from the start • Probably running out of buffer room • When Bulk data starts, DCF drops even more MPEG and bulk video • No other data affected (in first 20 sec) • Video conferencing is affected in longer simulations (>30 sec) • Seems to be function of overall rate (buffer room) • PCF drops bulk data but nothing else • Only drops lowest priority stream • Maintains all QoS streams Matthew Sherman, AT&T Labs - Research

  15. Retransmission Attempts PCF DCF Matthew Sherman, AT&T Labs - Research

  16. Retransmission Attempts • Substantial retransmission activity for DCF • Bulk Data has no obvious effects on retry • Medium already saturated • Retransmissions consume capacity • No Retransmissions required in PCF • Obvious and Expected • Efficiency advantage over DCF Matthew Sherman, AT&T Labs - Research

  17. Packet Delays Voice Voice Voice Audio Ack Bulk Data Audio Video Conf. Video Conf. MPEG Data Ack PCF DCF Matthew Sherman, AT&T Labs - Research

  18. Packet Delays • PCF packet delays very stable and well bounded on all streams but bulk data • Can maintain QoS • Especially true for voice • Some dependence on polling order • DCF shows substantially greater delay variation in all streams • MPEG already degraded • Video Conferencing and Audio hit hard by bulk data • QoS is not maintained • Streams sharing AP with Bulk data hit hardest Matthew Sherman, AT&T Labs - Research

  19. DCF Trace - Synchronized Data s -t 0.078352 -Hs 6 -Hd -2 -Ni 6 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms 6 -Mt WlanC_Ack x -t 0.078464 -Hs 6 -Hd -2 -Ni 6 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms 6 -Mt WlanC_Ack r -t 0.078465 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms -2 -Mt WlanC_Ack r -t 0.078465 -Hs 5 -Hd -2 -Ni 5 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms -2 -Mt WlanC_Ack r -t 0.078465 -Hs 4 -Hd -2 -Ni 4 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms -2 -Mt WlanC_Ack r -t 0.078465 -Hs 2 -Hd -2 -Ni 2 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms -2 -Mt WlanC_Ack r -t 0.078465 -Hs 3 -Hd -2 -Ni 3 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms -2 -Mt WlanC_Ack r -t 0.078465 -Hs 1 -Hd -2 -Ni 1 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms -2 -Mt WlanC_Ack s -t 0.080000 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md -1 -Ms 0 -Mt WlanC_Beac s -t 0.080000 -Hs 1 -Hd -2 -Ni 1 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 2 -Ms 1 -Mt WlanC_Data s -t 0.080000 -Hs 2 -Hd -2 -Ni 2 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data s -t 0.080000 -Hs 3 -Hd -2 -Ni 3 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 0 -Ms 3 -Mt WlanC_Data x -t 0.080087 -Hs 1 -Hd -2 -Ni 1 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 2 -Ms 1 -Mt WlanC_Data x -t 0.080087 -Hs 2 -Hd -2 -Ni 2 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data x -t 0.080087 -Hs 3 -Hd -2 -Ni 3 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 0 -Ms 3 -Mt WlanC_Data d -t 0.080087 -Hs 3 -Hd -2 -Ni 3 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 2 -Ms 1 -Mt WlanC_Data d -t 0.080087 -Hs 1 -Hd -2 -Ni 1 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 0 -Ms 3 -Mt WlanC_Data d -t 0.080087 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 1 -Ms 2 -Mt WlanC_Data d -t 0.080087 -Hs 4 -Hd -2 -Ni 4 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 0 -Ms 3 -Mt WlanC_Data d -t 0.080088 -Hs 5 -Hd -2 -Ni 5 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 0 -Ms 3 -Mt WlanC_Data x -t 0.080504 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 1 -Ms 2 -Mt WlanC_Beac d -t 0.080504 -Hs 2 -Hd -2 -Ni 2 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md -1 -Ms 0 -Mt WlanC_Beac d -t 0.080504 -Hs 6 -Hd -2 -Ni 6 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md -1 -Ms 0 -Mt WlanC_Beac s -t 0.081074 -Hs 2 -Hd -2 -Ni 2 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data x -t 0.081161 -Hs 2 -Hd -2 -Ni 2 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data r -t 0.081162 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data r -t 0.081162 -Hs 1 -Hd -2 -Ni 1 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data r -t 0.081162 -Hs 3 -Hd -2 -Ni 3 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data r -t 0.081162 -Hs 6 -Hd -2 -Ni 6 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data r -t 0.081162 -Hs 4 -Hd -2 -Ni 4 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data r -t 0.081162 -Hs 5 -Hd -2 -Ni 5 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 1 -Ms 2 -Mt WlanC_Data s -t 0.081172 -Hs 1 -Hd -2 -Ni 1 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 2 -Ms 1 -Mt WlanC_Ack x -t 0.081284 -Hs 1 -Hd -2 -Ni 1 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 2 -Ms 1 -Mt WlanC_Ack r -t 0.081284 -Hs 3 -Hd -2 -Ni 3 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 2 -Ms -2 -Mt WlanC_Ack r -t 0.081284 -Hs 4 -Hd -2 -Ni 4 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 2 -Ms -2 -Mt WlanC_Ack r -t 0.081284 -Hs 2 -Hd -2 -Ni 2 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 2 -Ms -2 -Mt WlanC_Ack r -t 0.081284 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 2 -Ms -2 -Mt WlanC_Ack r -t 0.081284 -Hs 5 -Hd -2 -Ni 5 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 2 -Ms -2 -Mt WlanC_Ack r -t 0.081284 -Hs 6 -Hd -2 -Ni 6 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 2 -Ms -2 -Mt WlanC_Ack Matthew Sherman, AT&T Labs - Research

  20. Key Trace features • NS compatible • First letter is event type • T: packet Tx start • X: packet Tx end • R: packet received • D: packet drop • -t indicates simulation time (rounded to microsec) • -Hs is observing (reporting) station address • -Na is Duration field • -Md is packet destination • -Ms is packet source • Frame type at end of line Matthew Sherman, AT&T Labs - Research

  21. DCF Trace - Synchronized Data • Multi-packet collision is common in simulations • Prior to beacon all STA have completed post-backoff • Data frame generated in sources at same time • 3 voice calls have identical parameters • Also synchronized with Beacon • Collisions could be avoided by phasing sources to discourage simultaneous triggering • What about network synchronization • Can devices in real network become synchronized so that this becomes a common problem? Matthew Sherman, AT&T Labs - Research

  22. DCF Trace - Delayed Beacon s -t 0.118858 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 4 -Ms 0 -Mt WlanC_Data x -t 0.119943 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 4 -Ms 0 -Mt WlanC_Data s -t 0.119954 -Hs 4 -Hd -2 -Ni 4 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 0 -Ms 4 -Mt WlanC_Ack x -t 0.120066 -Hs 4 -Hd -2 -Ni 4 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 0 -Ms 4 -Mt WlanC_Ack s -t 0.120337 -Hs 5 -Hd -2 -Ni 5 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 6 -Ms 5 -Mt WlanC_Data x -t 0.121451 -Hs 5 -Hd -2 -Ni 5 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 6 -Ms 5 -Mt WlanC_Data s -t 0.121461 -Hs 6 -Hd -2 -Ni 6 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms 6 -Mt WlanC_Ack x -t 0.121573 -Hs 6 -Hd -2 -Ni 6 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 5 -Ms 6 -Mt WlanC_Ack s -t 0.121684 -Hs 3 -Hd -2 -Ni 3 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 0 -Ms 3 -Mt WlanC_Data x -t 0.121771 -Hs 3 -Hd -2 -Ni 3 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 0 -Ms 3 -Mt WlanC_Data s -t 0.121782 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 3 -Ms 0 -Mt WlanC_Ack x -t 0.121894 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 3 -Ms 0 -Mt WlanC_Ack s -t 0.121965 -Hs 1 -Hd -2 -Ni 1 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 2 -Ms 1 -Mt WlanC_Data x -t 0.122052 -Hs 1 -Hd -2 -Ni 1 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 2 -Ms 1 -Mt WlanC_Data s -t 0.122062 -Hs 2 -Hd -2 -Ni 2 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 1 -Ms 2 -Mt WlanC_Ack x -t 0.122174 -Hs 2 -Hd -2 -Ni 2 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 1 -Ms 2 -Mt WlanC_Ack s -t 0.122265 -Hs 4 -Hd -2 -Ni 4 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 0 -Ms 4 -Mt WlanC_Data x -t 0.123350 -Hs 4 -Hd -2 -Ni 4 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 123 -Md 0 -Ms 4 -Mt WlanC_Data s -t 0.123360 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 4 -Ms 0 -Mt WlanC_Ack x -t 0.123472 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md 4 -Ms 0 -Mt WlanC_Ack s -t 0.123623 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md -1 -Ms 0 -Mt WlanC_Beac x -t 0.124127 -Hs 0 -Hd -2 -Ni 0 -Nx -53.26 -Ny 24.91 -Nz 100.00 -Ne -1.000000 -Nl MAC -Nw --- -Na 0 -Md -1 -Ms 0 -Mt WlanC_Beac Matthew Sherman, AT&T Labs - Research

  23. DCF Trace - Delayed Beacon • For DCF, Beacon is required to follow DCF rules • Must back off and defer like any other frame • In simulations backoff and deference can cause Beacon to be delayed beyond TBTT by several frames • In this case delayed 9 frames • Delayed roughly 3.6 milliseconds • Nothing wrong, but interesting to observe • Demonstrates utility of trace Matthew Sherman, AT&T Labs - Research

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