July 2012 Lei Wang, InterDigital - PowerPoint Presentation

1. July 2012Lei Wang, InterDigital CommunicationsSlide 1Discussions about 802.11ai FILS Discovery Frame (DF) Content Design Date: 2012-07-14Authors:

2. July 2012Lei Wang, InterDigital CommunicationsSlide 2AbstractThis document is intended to facilitate further discussions about passive scanning enhancement, by presenting some considerations and analysis about the design of the FILS Discovery Frame contents.This is a follow-up contribution with regarding to 802.11ai passive scanning enhancements as discussed in the contributions, 12/0406r5 and 12/0669r1. Also, it is about further details for a feature that has been accepted in the 802.11ai SFD.

3. July 2012Lei Wang, InterDigital CommunicationsSlide 3Conformance w/ TGai PAR & 5C Conformance QuestionResponseDoes the proposal degrade the security offered by Robust Security Network Association (RSNA) already defined in 802.11?NoDoes the proposal change the MAC SAP interface???Does the proposal require or introduce a change to the 802.1 architecture?NoDoes the proposal introduce a change in the channel access mechanism?NoDoes the proposal introduce a change in the PHY?NoWhich of the following link set-up phases is addressed by the proposal?(1) AP Discovery (2) Network Discovery (3) Link (re-)establishment / exchange of security related messages (4) Higher layer aspects, e.g. IP address assignment1,2

4. July 2012Lei Wang, InterDigital CommunicationsSlide 4BackgroundStraws poll conducted in 2012-May meeting about FILS Discovery Frame content design clearly shows two different opinions:Enough info for initiating associationCertain info for assisting scanning, but need to receive more info for initiating associationThis contribution will focus on further discussions about the 11ai FILS Discovery frame content design.Another related but separate contribution, 12/0742, focuses on the discussions about the 11ai FILS Discovery frame format design.

5. Basic Approach of FD Frame Content DesignInvestigating Existing Reference Materials802.11ah Short BeaconMeasurement Pilot FrameBeacon Frame / Probe Response frame11ai relevant contributionsIdentifying FD Frame contents based on its basic functions:Advertize the presence of the AP on the channelSynchronize the STAsProvide necessary information for a fast AP/Network selectionProvide necessary information to enable STA to transmitAnything else ???Slide 5Lei Wang, InterDigital CommunicationsJuly 2012

6. Slide 6Lei Wang, InterDigital CommunicationsJuly 2012Recap of 802.11ah Short Beacon Frame802.11ah has introduced a Short Beacon Frame into 11ah SFD (11/1137r9), based on proposals presented in contributions, 11/1503r2 and 12/129r3;Overview of 11ah short beacon:A short beacon allows for reduced medium occupancy reduced power consumption for TX at AP and RX at STAsOr, for the same overhead as a ‘normal’ beacon, allows for shorter Beacon Intervals, improving synchronization and power save at the STAs Asynchronous STAs waking up at a random time can get in synch quicklyThe short beacon is not meant to displace the normal beaconAP may e.g. send a normal ‘full’ beacon every N short beaconsShort beacon is an additional frame for optimized operationFrame Format and Contents of 802.11ah Short Beacon Frame:

7. Investigation of 802.11ah Short Beacon FrameSlide 7Lei Wang, InterDigital CommunicationsJuly 2012Informationdescription / Notessize (bytes)Apply to 11ai FILS Discovery (FD) frame?size in 11ai FD frameNotes Short Timestampused for Time Synchronization Function (TSF); mandatory in 11ah-SB.4yes, 4Based on slide 11 on the 11ah-short beacon contribution, 11/1503r1, it shows it is sufficient to have 4 bytes TSF field, not 8 bytes.Change sequenceused to Signal if network information has changed; Mandatory in 11ah-SB;mainly for power saving operations, e.g., sleep mode, after STA's initial association.1no, but debatable.0mainly for power saving operations, e.g., sleep mode, after STA's initial association.time of next full beaconInforms the STA of the arrival time of the next full beacon; optional in 11ah-SB; 3Yes, but could be designed to use only 1 byte.1could be designed as an offset value for the FD frame Tx time, so that only need 1 byte in sizeconpressed SSIDThe SSID element indicates the identity of an ESS or IBSS. optional in 11ah-SB; 4Yes, 411ah Proposal 12/0129r3: Compressed SSID should be a hash of the full SSID; and Hashing function should be standardizedAccess network optionsindicate access services provided by AP/Network; optional in 11ah-SB;1Yes,1can use the same format as Figure 8-352, in 802.11-2012BSS bandwidthmandatory in 11ah-SB; inside FC field of the new MAC header design3bitsyes, but not as a separate parameter.0should be considered as part of the Channel descriptor along with other channel parameters

8. Recap of Measurement Pilot (MP) FrameBased on 802.11-2012, the Measurement Pilot (MP) frame is a compact Action frame transmitted pseudo-periodically by an AP at a small interval relative to a Beacon Interval;provides reduced information relative to a Beacon frame to allow for the required small interval.The purpose of the Measurement Pilot frame is to assist a STA with the following functions:Rapid discovery of the existence of a BSS via passive scanning;Rapid collection of neighbor AP signal strength measurements via passive scanning;Enable transmission of a Probe Request.Slide 8Lei Wang, InterDigital CommunicationsJuly 2012

9. Recap of Measurement Pilot (MP) Frame – con’tFrame Format and Contents of Measurement Pilot (MP) frameSlide 9Lei Wang, InterDigital CommunicationsJuly 2012

10. Investigation of 802.11 Measurement Pilot FrameSlide 10Lei Wang, InterDigital CommunicationsJuly 2012Informationdescription / Notessize (bytes)Apply to 11ai FILS Discovery (FD) frame?size in 11ai FD frameNotesMP intervalbasic periodicity of MP frames1yes, but it should be changed to FD interval1** in units of TUs (i.e., 1024us)** is it really needed, considering STA already received the FD frame?Capabilityonly two bits are used: spectrum management; short slot time.1yes, but should be re-designed to cover more.2 to cover critical initial link setup capabilities, based on MP capability and beacon/probe response capability, further capability considerations, e.g., IPv4/IPv6, security capabilitiesCountry MP-frame uses a 2-byte condensed country string; although 3 bytes in dot11CountryString2Yes,2 operation classindicates the operating class value for the operating channel, as defined in Annex E.1yes1 operation channelindicates the operating channel, as defined in Annex E.1yes1 

11. References in Beacon, Probe Response, and 11ai ContributionsLots of additional information items in Beacon and Probe Response frames, as well as in other 11ai contributions;A fundamental consideration: what other information items are really needed to be transmitted to STA in the first AP-to-STA message for setting up the link?Channel descriptorsPHY specific infoSecurity infoBSS/AP load infoNeighbor AP infoWhat else????Slide 11Lei Wang, InterDigital CommunicationsJuly 2012

12. Investigation of Beacon, Probe Response, 11ai Contributions, …Slide 12Lei Wang, InterDigital CommunicationsJuly 2012CategoryInformationdescription / Notessize (bytes)Apply to 11ai FILS Discovery (FD) frame?size in 11ai FD framechannel descriptors (beyond Country, Operation class, Operation channel)power constraintsthe information necessary to allow a STA to determine the local maximum transmit power in the current channel. 1yes1channel bandwidththe channel bandwidth info is actually provided by the operation class and operation channel.0no, don't need a separate parameter0PHY specific infoERP (Extended Rate PHY)11g PHY, 1 byte as used in ERP IE in beacon frame; page 487, 3yes, PHY dependant1HT operation/HT capability11n PHY, current HT operation IE, HT capability IE, Overlapping BSS scan IE, and 20/40 coexistence IE77yes, PHY dependant, defined a compressed version2BSS load infoBSS load / average delay / channel unitlization …there are 5 BSS load related IEs in current beacon and probe response frame, i.e., 1) BSS load IE: 2+5 bytes2) BSS Available Admission Capacity IE: 2+2+2*n bytes; 3) QoS Traffic Capability IE: 2+1+n bytes; 4) BSS Average Access Delay IE: 2+1 bytes5) BSS AC Access Delay IE: 2+4 bytes35yes, should be compressed, e.g., an 1-byte indication, either using the average access delay or channel utilization1

13. Investigation of Beacon, Probe Response, 11ai Contributions, …-- Con’tSlide 13Lei Wang, InterDigital CommunicationsJuly 2012CategoryInformationdescription / Notessize (bytes)Apply to 11ai FILS Discovery (FD) frame?size in 11ai FD frameSecurity infosecuirty info Security capability; info from the current RSNE; any other security related info?48Yes, should be very selective and compressed.4Neighbor AP infoNeighbor AP inforeferences in 802.11-2012:1) Neighbor report element, in Figure 8-215 2). Beacon timing IE, page 695, section 8.4.2.107; for neigbhor's next becon Tx time;3). AP channel report IE, page 580, section 8.4.2.3813+ per neighboryes, should be designed in a very compressed way. Variable, 3*n; n is the number of neighbors

14. Discussions about FILS Discovery (FD) Frame ContentsBasic FD Frame Functions vs. Required Info Contents:Advertize the presence of the AP on the channel:BSSID, SSID, Channel descriptors, e.g., Country, Operation class, and Operation channelSynchronize the STAsTimestamp for Time Synchronization Function (TSF)Provide necessary information for a fast AP/Network selectionCapabilities; Time to next TBTT; BSS load; Security; Access Network options; neighbor info; etc.Provide necessary information to enable STA to transmitPHY specific parameters; power constraint; etc.FD frame information content selection considerations :Minimize the mandatory info contents, e.g., only the AP presence parameters are mandatory;Include additional info contents in a flexible and incremental way.A summary of FD frame content discussion is provided in next two slides;more details can be found in the Appendix section of this contribution.Slide 14Lei Wang, InterDigital CommunicationsJuly 2012

15. Summary of FILS Discovery Frame Content ConsiderationsSlide 15Lei Wang, InterDigital CommunicationsJuly 2012IndexInformationdescription / Notessize (bytes)mandatory / optional1compressed SSIDThe SSID element indicates the identity of an ESS or IBSS.4mandatory2 Short Timestampused for Time Synchronization Function (TSF)4Optional3Condensed Country stringuses the same 2-byte condensed country string as in MP frame; although 3 bytes in dot11CountryString2mandatory4operation classindicates the operating class value for the operating channel, as defined in Annex E.1mandatory5operation channelindicates the operating channel, as defined in Annex E.1mandatory6power constraintsthe information necessary to allow a STA to determine the local maximum transmit power in the current channel. 1optional7time of next TBTTInforms the STA of the arrival time of the next full beacon, an offset value in unit of Tus from the FD frame Tx time1mandatory8Access network optionsindicate access services provided by AP/Network1optional9FILS Discovery (FD) Intervalbasic periodicity of FILS Discovery frames, in units of TUs (i.e., 1024us)1optional

16. Summary of FILS Discovery Frame Content Considerations-- Con’tSlide 16Lei Wang, InterDigital CommunicationsJuly 2012IndexInformationdescription / Notessize (bytes)mandatory / optional10Capabilityused to indicate requested or advertised capabilities; covering critical initial link setup capabilities, based on MP capability and beacon/probe response capability, further capability considerations, e.g., IPv4/IPv6, etc.2optional11PHY InfoPHY specific parameters, e.g., ** 11g PHY, 1 byte as used in ERP IE in beacon frame; page 487, **11n PHY, current HT operation IE, HT capability IE, Overlapping BSS scan IE, and 20/40 coexistence IEvariableoptional12Security infoindicate security related capabilities, and further security info that requires early provisioning, e.g., info abstracted from the current RSNE4optional13BSS load InfoCompressed indication of the BSS load info, e.g., average access delay and/or Channel utilization1optional14Neighbor AP infoprovide a list of neighbor APs/Channels and their TBTTs, e.g., just list the channel class / channel number and next beacon time.Variableoptional15Other optional IEsused to include other additional IEsvariableoptional

17. Discussions about FD Frame Contents and Relevant ProceduresEnabling multiple use cases with optional FD frame content itemsExample-1: the FD frame body contains a minimum set of info, e.g., only the info for advertising the presence of AP and the info of next TBTT, which enables STA:To decide whether waiting for the regular beacon or switching to scan another channel and then coming back to receive beacon at the proper time; andTo minimize the needs of sending probe request with wildcard SSID.Example-2: the FD frame body contains enough info for STA to initiate association, which enables STA to complete the scanning of the channel without waiting for beacon or sending probe request.Example-3: the FD frame body contains a minimum set of info plus neighbour APs’ next TBTTs, which enables STA :to optimally schedule the scanning of multiple channels/APs by minimizing the total waiting time for scanning the multiple channels.Slide 17Lei Wang, InterDigital CommunicationsJuly 2012

18. Discussions about FD Frame Contents and Relevant Procedures – Con’tThe flexible inclusions of FD frame body contents:Allows AP to decide what information to carry in FD frames, based on certain real-time factors, e.g., traffic loading, percentage of medium time consumed by FD frames; etc.Enables STA to decide what to do next, depending on the available info in a received FD frame, e.g., switching to another channel, initiating association, etc.Slide 18Lei Wang, InterDigital CommunicationsJuly 2012

19. Straw-PollsStraw-Poll-1: Do you support including the following information items in the FILS Discovery Frame body?Compressed SSIDCondensed Country StringOperation ClassOperation ChannelTime of Next TBTTResult Yes No Abstain_______________Slide 19Lei Wang, InterDigital CommunicationsJuly 2012

20. Straw-PollsStraw-Poll-2: Do you support optionally including the following information items in the FILS Discovery Frame body?Short TimestampPower ConstraintsAccess Network OptionsFILS Discovery frame intervalCapability informationSecurity InformationBSS Load InformationPHY information Neighbor AP informationResult Yes No Abstain_______________Slide 20Lei Wang, InterDigital CommunicationsJuly 2012

21. Motions for Proposed Text for SFDMotion-1: add the following text to Subsection “6.2.1 General Approach”, on page 8, in the TGai SFD, 12/0151r8The FILS Discovery frame shall include the following information fields:A Compressed SSID fieldA Condensed Country String fieldAn Operation Class fieldAn Operation Channel fieldA Time of Next TBTT fieldMover: Seconder: Result Yes No Abstain_______________Slide 21Lei Wang, InterDigital CommunicationsJuly 2012

22. Motions for Proposed Text for SFDMotion-3: add the following text to Subsection “6.2.1 General Approach”, on page 8, in the TGai SFD, 12/0151r8The FILS Discovery frame may include the following information items:Short TimestampPower ConstraintsAccess Network OptionsFILS Discovery frame intervalCapabilitySecurity InformationBSS Load InformationPHY informationNeighbor AP informationMover: Seconder: Result Yes No Abstain_______________Slide 22Lei Wang, InterDigital CommunicationsJuly 2012

23. July 2012Lei Wang, InterDigital CommunicationsSlide 23References:IEEE Std 802.11™-201211-12-0191-03-00ai-call-for-contributions-to-the-tgai-specification-framework11-12-0151-07-00ai-proposed-specification-framework-for-tgai11-12-0406-05-00ai-passive-scanning-improvements-draft11-12-0669-01-00ai-passive-scanning-improvements-ad-hoc-report11-12-0742-00-00ai-FILS-Discovery-Frame-Format-Discussions11-11-1137-09-00ah-specification-framework-for-tgah11-11-1503-02-00ah-short-beacon11-12-0129-03-00ah-short-beacon

24. July 2012Lei Wang, InterDigital CommunicationsSlide 24Appendix

25. Detailed Discussions about FD Frame ContentsA fundamental question: what information items are needed for the FD frame’s basic functions:Advertize the presence of the AP on the channel:BSSID, SSID, Channel descriptors, e.g., Country, Operation class, and Operation channelSynchronize the STAsTimestamp for Time Synchronization Function (TSF)Provide necessary information for a fast AP/Network selectionCapabilities; Time to next TBTT; BSS load; Security; Access Network options; neighbor info; etc.Provide necessary information to enable STA to transmitPHY specific parameters; power constraint; etc.Slide 25Lei Wang, InterDigital CommunicationsJuly 2012

26. Information for Advertizing the presence of the AP on the channelBSSID: uniquely identifies each BSS6-byte MAC address of the AP for an infrastructure BSS;address-3 field in the MAC header of MAC management frame.SSID: the identity of an ESS or IBSSCurrently in 802.11-2012, encoded as IE with 0 to 32 bytes SSID field;Compressed SSID: proposed in 802.11ah short beacon, 12/0129r3, 4-byte, Contains a representation of the SSID of the BSSA device that knows the full SSID can discover the presence of the BSS by decoding the compressed SSIDProposal: Compressed SSID should be a hash of the full SSID Hashing function should be standardizedQuestion: Can the 11ah compressed SSID proposal be re-used for 11ai FILS Discovery frame? Slide 26Lei Wang, InterDigital CommunicationsJuly 2012

27. Information for Advertizing the presence of the AP on the channel – Con’tChannel descriptors:Country, Operation Class, and Operation Channel together specify the channel frequency and spacing for the operating channel.Country string: identifying the country where the STA locates and operates.3-byte parameter: dot11CountryStringCondensed Country string: first 2 bytes in dot11CountryString, used in Measurement Pilot frame.Operation class: identifying the operation class for the operation channel1-byte, as defined in Annex E in 802.11-2012 spec.Operation channel: identifying the operation channel within the operation class1-byte, as defined in Annex E in 802.11-2012 spec.Slide 27Lei Wang, InterDigital CommunicationsJuly 2012

28. Information for Synchronizing STATimestamp for Time Synchronization Function (TSF):8-byte in beacon frame as specified in 802.11-2012 spec;4-byte proposed for 11ah-short beacon, with the following reasons to support that 4 LSBs of the full TSF is Sufficient for maintaining synchronizationWith a 4 byte time stamp rollover occurs every ~71 minutesWith a +/- 20 ppm drift for the clock, to drift by 30 min (~71/2) will take 1.4 yearsA sensor node can maintain time sync with its AP if it checks a short beacon as rarely as once a dayQuestion: is 4-byte Timestamp sufficient for 11ai FILS Discovery frame?Slide 28Lei Wang, InterDigital CommunicationsJuly 2012

29. Information for Facilitating a Fast AP/Network SelectionTime to next TBTTIndicating the arrival time of next regular beacon frame from the transmitting AP of the current FD frame;1-byte, in unit of Transmission Unit (TU), i.e., 1024us;Setting to the offset value referencing from the current FD frame transmission time.Slide 29Lei Wang, InterDigital CommunicationsJuly 2012

30. Information for Facilitating a Fast AP/Network Selection – con’tCapabilities:What type of capability indications are needed in FD frame? capabilities that assist STA for a fast AP/Network discoveryReferences: Multiple capability information items in Beacon / Probe Response, e.g., Capability information field, Extended Capability IE, etc.Capability indications considered in FD frame:PHY capability indications: should be considered as part of PHY info?Short Preamble, PBCC, Security capability indications: should be considered as part of security info?ESS indicatorShort slot timeSpectrum ManagementIPv4/IPv6????Slide 30Lei Wang, InterDigital CommunicationsJuly 2012

31. BSS load information indicating the level of traffic loading at the BSS5 relevant IEs in 802.11-2012 spec:BSS load IE: 2+5 bytes, containing the info of STA count: the total number of STAs currently associated with this BSS;Channel utilization: the percentage of time, linearly scaled with 255 representing 100%, that the AP sensed the medium was busy;Admission Capability: the remaining amount of medium time available via explicit admission control, in units of 32 μs/s.BSS Available Admission Capacity IE: 2+2+2*n bytes, containing the info of Admission Capabilities for each UP/AC (User Priority / Access Category);QoS Traffic Capability IE: 2+1+m bytes, containing the info of STA counts for each UP/AC ;BSS Average Access Delay IE: 2+1 bytes, containing the info of a scalar indication of average medium access delay;BSS AC Access Delay IE: 2+4 bytes; containing the info of Access Delay for each UP/AC.Slide 31Lei Wang, InterDigital CommunicationsJuly 2012Information for Facilitating a Fast AP/Network Selection – con’t

32. BSS load information – Con’t Question: do we need this many different BSS load related IEs in the 11ai FILS Discovery frame? Answer: No, not at all!What is it really needed in FD frame regarding BSS load? An indication of how busy the AP is, i.e., the level of loading at the AP;One or two parameters should be sufficient, e.g., ;Average access delay: 1-byte info; specified in Section 8.4.2.41 in802.11-2012;Channel utilization: 1-byte info; specified in Section 8.4.2.30 in 802.11-2012.Can we define an 1-byte data to indicate the BSS load info? Yes!It can be one parameter, e.g., Average Access Delay;Or, it can contain two parameters, e.g., 5 bits for Average Access Delay3 bits for channel utilizationSlide 32Lei Wang, InterDigital CommunicationsJuly 2012Information for Facilitating a Fast AP/Network Selection – con’t

33. Security infoSecurity info in Beacon and Probe Response:RSNE: Robust Security Network ElementPrivacy capability indication in the Capability info fieldAny additional security info considerations:FILS Fast-EAP based authenticationFILS EAP-RP based authenticationFILS Non-EAP Fast authenticationWhat else?Questions:What security info should be included in the FD frame?Is it possible to have a fixed-size security info field, e.g., 4-byte field, in the FD frame?Slide 33Lei Wang, InterDigital CommunicationsJuly 2012Information for Facilitating a Fast AP/Network Selection – con’t

34. Access Network options: indicates access services provided by AP/Network ;1-byte info as defined in Figure 8-352, in 802.11-2012 spec, also adopted in 802.11ah short beacon.Slide 34Lei Wang, InterDigital CommunicationsJuly 2012Information for Facilitating a Fast AP/Network Selection – con’t

35. Neighbor AP Info Provide info of the neighbor APs/Channels;What info should be included for each neighbor AP?Channel class: 1-byte, as defined in Annex E; assume the same country string as the transmitting AP;Channel number: 1-byte, as defined in Annex E;Next TBTT: 1-byte, an offset value in unit of TUs referencing from this FD frame transmission time;BSSID or SSID: do we really need this info? Debatable! Example of the Neighbor AP IE in FILS Discovery frame:Slide 35Lei Wang, InterDigital CommunicationsJuly 2012Information for Facilitating a Fast AP/Network Selection – con’t

36. Information for Enabling STA to TransmitQuestion: when a STA can receive and decode FD frame, how much PHY and RF channel information does it have already before reading any contents in the FD frame?Dot11 system is TDD, i.e., Rx and Tx on the same channel, therefore, there should be some channel info obtained through the reception of FD frame or Beacon frame.The PHY header must also contains some info about PHY, e.g., PHY type, PHY specific info:11g: 1 byte info body in the ERP IE, 11n: HT capability IE; HT operation IE; 20/40 coexistence IE; Overlapping BSS scan IE;11ac: VHT Capabilities; VHT Operation; VHT Transmit Power Envelope element;Power ConstraintOne IE in current Beacon and Probe Response frame, with 1 byte info body.Slide 36Lei Wang, InterDigital CommunicationsJuly 2012

37. Information for Enabling STA to Transmit – con’tPHY specific info:11g: 1 byte info body in the ERP IE, with only 3 bits actually used. Slide 37Lei Wang, InterDigital CommunicationsJuly 2012BitsB0B1B2B3B4B5B6B7ReservedNonERP_PresentUse_ProtectionBarker_Preamble_ModeQuestions:Are the PHY capability indications in the current Capability field, e.g., short preamble, PBCC, applied to 11g?If so, can we use the current reserved bits in the ERP info body for those PHY capability indications?

38. Information for Enabling STA to Transmit – con’tPHY specific info – Con’t11n: multiple IEs in Beacon and Probe Response based on 802.11-2012HT capability IE: 26-byte info body; could be cut down to 1-byte info body, in FD frame, as defined in next slide.HT operation IE: 22-byte info body; could be cut down to 1-byte info body, i.e., the Primary Channel field, in FD frame20/40 coexistence IE: variable-size info body; not needed in FD frame;Overlapping BSS scan IE: 14-byte info body; not needed in FD frame.2-byte info body for11n PHY Specific Info in FD frame:1-byte for Short HT capability 1-byte for Primary Channel.Slide 38Lei Wang, InterDigital CommunicationsJuly 2012

39. Information for Enabling STA to Transmit – con’tPHY specific info – Con’tShort HT Capability Information Field:Slide 39Lei Wang, InterDigital CommunicationsJuly 2012HT Capability ItemSize (bits)Supported Channel Width Set1HT-Greenfield1Tx STBC1Rx STBC2Reserved240 MHz Intolerant1HT PHY Info in FD Frame:BitsB0B1B2B3B4B5B6B7Supported Channel Width SetHT-GreenfieldReserved40 MHz IntolerantB8B15Primary ChannelRX STBCTX STBC

40. Information for Enabling STA to Transmit – con’tPHY specific info:11ac: multiple IEs in Beacon frame and Probe Response frame based on P802.11ac/D3.0, e.g.,VHT Capabilities element: 12 bytes for info fields;VHT Operation element: 5 bytes for info fields;VHT Transmit Power Envelope element: 2 to 5 bytes for info fields;What’re needed in FILS Discovery frame for 11ac PHY specific?Slide 40Lei Wang, InterDigital CommunicationsJuly 2012

41. Information for Enabling STA to Transmit – Con’tPower ConstraintPower Constraint IE in Beacon and Probe Response frame, 1 byte info body;contains the information necessary to allow a STA to determine the local maximum transmit power in the current channel.Questions: do we really need this parameter in the FD frame?If so, should it be part of the PHY specific info?Slide 41Lei Wang, InterDigital CommunicationsJuly 2012

42. Detailed Discussions about FD Frame Contents – con’tOther Optional IEs ??????Slide 42Lei Wang, InterDigital CommunicationsJuly 2012