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Discussions about 802.11ai FILS Discovery (FD) Frame Content Design

Discussions about 802.11ai FILS Discovery (FD) Frame Content Design. Date: 2012-09-06. Authors:. Abstract.

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Discussions about 802.11ai FILS Discovery (FD) Frame Content Design

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  1. Discussions about 802.11ai FILS Discovery (FD) Frame Content Design • Date:2012-09-06 Authors: Lei Wang, InterDigital Communications

  2. Abstract • This contribution is intended to facilitate further discussions about passive scanning enhancement, particularly regarding to further detailed design of the FILS Discovery Frame contents. • This contribution proposes further detailed text that is intended to be adopted to the TGai Specification document, for the functionality of FILS Discovery Frame, as specified Section 6.3.1 in the TGai SFD (Specification Framework Document, 12/0151r12). Lei Wang, InterDigital Communications

  3. Conformance w/ TGai PAR & 5C Lei Wang, InterDigital Communications

  4. Lei Wang, InterDigital Communications Background • Progress has been made regarding the FILS Discovery Frame content design in both the 2012 May and July meetings; • However, the FILS Discovery frame content design is not complete; • This contribution continues the discussions to further define the 11ai FILS Discovery frame contents.

  5. Lei Wang, InterDigital Communications The focus of this Contribution • The focus of this contribution will be the FD frame content design, including the detailed information items and their encoding; • Another related but separate contribution, 12/1029, will focus on the discussions related to the 11ai FILS Discovery frame format design, i.e., the MAC framing issues.

  6. Recap of FD Frame Content Design Status • Decisions made in 2012-July meeting (12/0913r3): • Mandatory info item in FILS Discover frame: • SSID • Optional info items in FILS Discovery frame: • Capability • Access network options • Security • AP Configuration change count • AP’s next TBTT • Neighbor AP’s next TBTT • Format of “Access Network Options” info item: re-use the 1-byte information as defined in Figure 8-352 in 802.11-2012. Lei Wang, InterDigital Communications

  7. Recap of FD Frame Content Design Status – con’t • Open issues regarding FILS Discover Frame content design: • Detailed contents and encodings for info items: • SSID, • Capability, • security, • AP Configuration change count, • AP’s next TBTT, • Neighbor AP’s next TBTT Lei Wang, InterDigital Communications

  8. SSID Info Item in FILS Discovery Frame • Purpose of SSID info item in FD frame • Advertise the presence of ESS & AP on the channel • Reference materials • 802.11-2012: SSID IE with 0 to 32 bytes • 11ah short beacon: compressed SSID 4 bytes (11/1503r2, 12/0129r3) • Re-cap of the Discussions in 2012-July meeting (12/0913r3) • About compressed SSID: • Compressed SSID is not enough to initiate association based on current 802.11 spec! • Can FILS Discovery frame use compressed SSID? • Does compressed SSID provide enough info to advertise AP’s presence in the channel? • 11ah compressed SSID only provides one-way mapping • Compressed SSID could be useful to STAs that have associated with the AP previously • Should the FILS discovery frame information items be designed to keep backward compatible? • Truncated SSID • Use full SSID • Use condensed SSID with 8 bytes, as the current commonly used SSIDs are from 6 to 8 bytes Lei Wang, InterDigital Communications

  9. SSID Info Item in FILS Discovery Frame – con’t • Key Open Issues and Discussions: • Should the FILS discovery frame information items be designed to keep backward compatible? • Not Necessary! FD frame is intended to be used by 11ai-capable STAs. • Also, suggest not to enforce it, as optimized encodings are needed! • Full SSID is needed to initiate association based on current 802.11 spec! • Seems not acceptable in TGai to impose any constraints to SSID selection. • Can the condensed SSID be deterministically mapped back to the full SSID? • Compressed SSID: • Possible, if the STA has associated with the AP previously, otherwise; • No, if using the 11ah Compressed SSID; • TBD (although very difficult), open for any new proposals about compressed SSID. • Truncated SSID • No, if the “truncation” really occurs; • Yes, if actually no truncation occurs, for the cases where the full SSID is within the retention-size, e.g., Use 8 bytes as the retention-size, considering the current commonly used SSIDs are from 6 to 8 bytes. Lei Wang, InterDigital Communications

  10. SSID Info Item in FILS Discovery Frame – con’t • Proposal: • Allow variable-size SSID in FD frame; • Do not use the information element format of SSID in 802.11-2012; • Introduce a separate control sub-field to signal the actual size of the SSID in a FD frame, for a better encoding efficiency; see next slide for details; • Consider two options: • Option-1: keep the same size range for the SSID as specified in 802.11-2012, i.e., 0 to 32 bytes; • Option-2: using a smaller size range, i.e., truncated SSID range, e.g., 0 to 8 bytes. Lei Wang, InterDigital Communications

  11. Introduction of FD Frame Control Field • FD Frame Control Field: • The first info field in the FD frame body; • Used to indicate the presence of the optional info items in the FD frame body; • Also used to accommodate variable-size info items in the FD frame body. Lei Wang, InterDigital Communications

  12. Proposed SSID Info Item Details in FD Frame Lei Wang, InterDigital Communications

  13. Capability Info Item in FILS Discovery Frame • Discussion points from2012-July meeting (12/0913r3) • It is one of the optional info items in FD frame; • Its purpose is to provide info for AP/Network initial de-selection; • Additional discussion about the Support data rates • Attempt to eliminate the supported rates element, by using the reserved bits in capability info field to indicate the identified minimum rates. • Reference materials identified in 2012-July meeting (12/0913r3) • Beacon/Probe Response in 802.11-2012 spec • Capability info field: p438, section 8.4.1.4 • Supported Rates element, p478, 8.4.2.3 • Extended Capabilities element, p562, section 8.4.2.29 • Neighbor Report element, 8.4.2.39 • Measurement Pilot frame • 11ah short beacon (11/1503r2, 12/0129r3) • Further Design Considerations • What capability indicators are needed in FD frame? • Detailed encodings of the capability indicators? Lei Wang, InterDigital Communications

  14. Capability Info Item in FILS Discovery Frame – con’t • Proposal: • Design a fixed-size new capability field in FD frame, e.g., 3 bytes; • Use the 2-byte Capability field as defined in Figure 8-38 in 802.11-2012 as starting point; and remove the unnecessary subfields for FD frame uses, e.g., • DSSS-OFDM • PBCC • Channel Agility • APSD • Add some new info items, e.g., • Supported minimum rate • PHY type • IPv4 / IPv6 support • Use a 1-bit indicator in the FD frame control field to indicate the presence of the Capability info item in the FD frame. Lei Wang, InterDigital Communications

  15. Capability Info Item in FILS Discovery Frame – con’t Lei Wang, InterDigital Communications

  16. Access Network Options Info Item in FILS Discovery Frame • Re-cap of the Decisions made about the Access Network Options info item in 2012-July meeting (12/0913r3) • One of the optional info items in FD frame; • Re-use the 1-byte encoding as defined in Figure 8-352 in 802.11-2012. • One open issue: • how to indicate the presence of the Access Network Options info item in FD frame? • Proposal: • Use a 1-bit sub-field in the FD frame control to indicate the presence of the Access Network Options info item in FD frame! Lei Wang, InterDigital Communications

  17. Access Network Options Info Item in FILS Discovery Frame – con’t Lei Wang, InterDigital Communications

  18. Security Info Item in FILS Discovery Frame • Discussion points from 2012-July meeting (12/0913r3) • It is one of the optional info items in FD frame; • Its purpose is to provide info for AP/Network initial de-selection; • Reference materials • RSNE in Section 8.4.2.27 in 802.11-2012 spec • Further Design Considerations • What Security indicators are needed in FD frame? • Detailed encodings of the Security indicators? Lei Wang, InterDigital Communications

  19. Security Info Item in FILS Discovery Frame – con’t • Proposal: • Design a fixed-size new Security field in FD frame, e.g., 4 bytes; • Use the RSNE as defined in Section 8.4.2.27 in 802.11-2012 as starting point; and consider changes to make it smaller in size, e.g., • Re-design the RSN Capabilities subfield to reflect its practical uses and 11ai specific considerations; • Limit the numbers of Pairwise suites and AKM suites, e.g., 2 for each • Introduce 4-bit codes to identify Cipher Suites and AKM Suites • Remove PMKID count and PMLID list • Add some new info items, e.g., • Security capability indicators for FILS authentication methods support, e.g., • FILS Fast-EAP based authentication • FILS EAP-RP based authentication • FILS Non-EAP Fast authentication • FILS Fast Authentication without 3rd-party • Use a 1-bit indicator in the FD frame control field to indicate the presence of the Security info item in the FD frame. Lei Wang, InterDigital Communications

  20. Security Info Item in FILS Discovery Frame – con’t Lei Wang, InterDigital Communications

  21. AP Configuration Change Count (AP-CCC) Info Item in FILS Discovery Frame • Discussion points from 2012-July meeting (12/0913r3) • It is one of the optional info items in FD frame; • Its purpose is to enable some STAs to initiate association, e.g., those STAs that have known the AP’s configuration previously. • Reference materials • 11ah configuration sequence (11/1503r2) • 1Byte, updated every time management info changes; • To Alert STAs to get on synch with new Info, by either listening to the (optional) IE in this beacon, by listening to a Full beacon or through probe request • 11ai GAS configuration change count (12/0053r1, 12/0158r3) • AP may include a GAS configuration-change element in the Beacon and Probe Response to indicate changes in a set of static GAS parameters. • Further Design Considerations • What’s a set of AP/Network configuration parameters, for which the AP Configuration Change Count (AP-CCC) is used? • What’s the size of the AP-CCC in FD frame? Lei Wang, InterDigital Communications

  22. AP Configuration Change Count (AP-CCC) Info Item in FILS Discovery Frame – con’t • Proposal: • Decouple the design of the set of AP/Network configuration parameters from the design of the AP-CCC in FD frame, i.e., • Only address the design of the AP-CCC in FD frame in this contribution; • Leave the design of the set of AP/Network configuration parameters and other relevant issues to separate contribution(s), under the assumption that the configuration parameters are static or semi-static, e.g., at least hours between two changes; • Use an one byte AP-CCC in FD frame; • Use a 1-bit indicator in the FD frame control field to indicate the presence of the AP-CCC in the FD frame Lei Wang, InterDigital Communications

  23. AP Configuration Change Count (AP-CCC) Info Item in FILS Discovery Frame – con’t Lei Wang, InterDigital Communications

  24. AP’s Next TBTT Info Item in FILS Discovery Frame • Discussion points from 2012-July meeting (12/0913r3) • It is one of the optional info items in FD frame; • Its purpose is to enable optimizations for multiple APs/Channels scanning. • Reference materials • Time of next full beacon in11ah Short Beacon (12/0129r3) • 3-byte: Higher 3 bytes of the 4 LSBs of the AP time stamp at the next full beacon • Informs the STA of the arrival time of the next full beacon. • Enables STAs to go to sleep until the next full beacon • Time of next beacon: derived by the Timestamp and Beacon Interval fields in Probe Response • Design Considerations for Next TBTT info item in FD frame • Cannot use a value from AP timestamp of next regular beacon, because: • STA is not expected to be synchronize with the AP at the FD frame reception time, as the FD frame does not contain the TimeStamp info, based on the decisions made in 2012-July meeting (12/0913r3) Lei Wang, InterDigital Communications

  25. AP’s Next TBTT Info Item in FILS Discovery Frame – con’t • Proposal • Use an 1-byte offset value to indicate AP’s Next TBTT in FD frame; • The offset value is the time in unit of in unit of Transmission Unit (TU), i.e., 1024us, between the current FD frame transmission time and next regular beacon transmission time; • Use a 1-bit indicator in the FD frame control field to indicate the presence of the AP’s next TBTT info field in the FD frame. Lei Wang, InterDigital Communications

  26. AP’s Next TBTT Info Item in FILS Discovery Frame – con’t Lei Wang, InterDigital Communications

  27. Neighbor AP’s TBTT Info Item in FILS Discovery Frame • Discussion points from 2012-July meeting (12/0913r3) • It is one of the optional info items in FD frame; • Its purpose is to enable optimizations for multiple APs/Channels scanning. • Reference materials in 802.11-2012 • Neighbor report element, Section 8.4.2.39; • Beacon timing IE, Section 8.4.2.107, for neighbor's next beacon Tx time; • AP channel report IE, Section 8.4.2.38 • Design Considerations • Similarly, cannot use a value from the transmitting AP’s timestamp or the neighbor AP’s timestamp to indicate the neighbor AP’s next TBTT, due to the un-synchronized status of the STA and the APs; • How to identify a neighbor AP? Lei Wang, InterDigital Communications

  28. Neighbor AP’s TBTT Info Item in FILS Discovery Frame – con’t • Proposal: • Use a 3-byte info field in the FD frame to provide a neighbor AP’s TBTT info, consisting of 3 subfields, 1-byte each, • Operating Class subfield: 1 byte, an enumerated value defined in Annex E in 802.11-2012 specifying the operating class of the neighbour AP; • Channel Number subfield: 1 byte, an enumerated value defined in Annex E in 802.11-2012 specifying the operating class within the Operating Class of the neighbor AP; • Next TBTT subfield: 1-byte, an offset value in unit of TU, specifying the time between the FD frame Tx time and the Neighbour AP’s next TBTT. • Allow up to 2 neighbor AP’s TBTT info fields in a FD frame, i.e., provide info of up to 2 neighbor APs; • The included neigbhor APs may be selected among all the neighbors, based on their next TBTTs relatively to the current AP’s next TBTT. • Use a 2-bit indicator in the FD frame control field to indicate the presence of Neighbor APs’ TBTT info in the FD frame. Lei Wang, InterDigital Communications

  29. Neighbor AP’s TBTT Info Item in FILS Discovery Frame – con’t Lei Wang, InterDigital Communications

  30. Summary of FD Frame Control Field Lei Wang, InterDigital Communications

  31. Discussion on FILS Discovery Frame Body Size • Typical FD Frame Body Sizes • Assume a typical SSID is of 8 bytes, then, • Without any optional info items, the FD frame body size is 10 bytes; • With all the optional info items, the FD frame body size is 26 bytes, which is also the maximum FDM frame body size for a typical SSID. • Beacon Frame Sizes • Based on a 11g-based system traffic measurement (11/1031r0) • About 75% Beacon frames have the size of 158 bytes; • 11g-based MAC framing overhead is 28 bytes, including management frame MAC header and FCS; • Then, a typical Beacon frame body size is about 130 bytes. • Comparisons • The proposed FD frame body without optional info items is of only 7.7% of a typical Beacon frame body size (130 bytes). • The proposed FD frame body with the all optional info items is of 20% of a typical Beacon frame body (130 bytes). Lei Wang, InterDigital Communications

  32. Discussion on FD Frame Body Extensibility • The proposed FD frame body design is extendible, when needed; • Two basic mechanisms: • Use the available bits in the FD frame control field; • Use information elements. Lei Wang, InterDigital Communications

  33. Straw-Polls • Straw-Poll-1: • Do you support the proposal of introducing the FILS Discovery (FD) frame control field as described in Slide 11 of this contribution? • (Notes: The FD frame control field is proposed to indicate the presences of the optional info items in the FD frame and also to accommodate variable size info items in the FD Frame) • Result Yes No Abstain_______________ Lei Wang, InterDigital Communications

  34. Straw-Polls • Straw-Poll-2: • Which option of SSID info item encoding proposals do you support as presented on Slide 12 of this contribution? • (Notes: • Option-1: 0 to 32 bytes SSID, with a 6-bit subfield in FD frame control field to indicate its length; • Option-2: 0 to 8 bytes SSID, with a 4-bit length subfield and an 1-bit full/truncated SSID indicator.) • Result Option-1 Option-2 None of them__________ Lei Wang, InterDigital Communications

  35. Straw-Polls • Straw-Poll-3: • Do you support the proposal of the FILS Discovery (FD) capability info item encoding as described in Slide 15 of this contribution? • Result Yes No Abstain_______________ Lei Wang, InterDigital Communications

  36. Straw-Polls • Straw-Poll-4: • Do you support the proposal of the FILS Discovery (FD) Access Network Options (ANO) info item encoding as described in Slide 17 of this contribution? • (Notes: The only difference between the proposal on Slide 17 and the decision made in July meeting about FD ANO is that, on Slide 17, one control subfield is used in the FD frame control to indicate if FD ANO is present. ) • Result Yes No Abstain_______________ Lei Wang, InterDigital Communications

  37. Straw-Polls • Straw-Poll-5: • Do you support the proposal of the FILS Discovery (FD) Security info item encoding as described in Slide 20 of this contribution? • Result Yes No Abstain_______________ Lei Wang, InterDigital Communications

  38. Straw-Polls • Straw-Poll-6: • Do you support the proposal of the FILS Discovery (FD) AP Configuration Change Count (AP-CCC) info item encoding as described in Slide 23 of this contribution? • Result Yes No Abstain_______________ Lei Wang, InterDigital Communications

  39. Straw-Polls • Straw-Poll-7: • Do you support the proposal of the FILS Discovery (FD) AP’s Next TBTT info item encoding as described in Slide 26 of this contribution? • Result Yes No Abstain_______________ Lei Wang, InterDigital Communications

  40. Straw-Polls • Straw-Poll-8: • Do you support the proposal of the FILS Discovery (FD) Neighbor AP info item encoding as described in Slide 29 of this contribution? • Result Yes No Abstain_______________ Lei Wang, InterDigital Communications

  41. Lei Wang, InterDigital Communications References: • IEEE Std 802.11™-2012 • 11-12-0151-12-00ai-proposed-specification-framework-for-tgai • 11-12-0913-03-00ai-paasive-scanning-discussions • 11-12-0741-01-00ai-discussions-about-fils-discovery-frame-content-design • 11-12-0406-05-00ai-passive-scanning-improvements-draft • 11-12-0669-01-00ai-passive-scanning-improvements-ad-hoc-report • 11-12-0742-00-00ai-FILS-Discovery-Frame-Format-Discussions • 11-11-1137-09-00ah-specification-framework-for-tgah • 11-11-1503-02-00ah-short-beacon • 11-12-0129-03-00ah-short-beacon • 11-11-1031-00-00ai-air-time-consumption-by-beacon-and-probe • 11-12-0053-01-00ai-gas-version-control-including-normative-text • 11-12-0158-03-00ai-proposed-additions-to-sfd • 11-12-1029-00-00ai-FILS-Discovery-Frame-Format-Discussions

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