html5-img
1 / 19

Dynamic BSS Condition

Dynamic BSS Condition. Matthew Fischer Broadcom. Proposal to Remedy NO comments. Legacy BSS causes ERP BSS to use legacy slot – all BSS in a chain of overlapping ERP BSS fall like dominoes When legacy BSS disappears, entire chain of ERP BSS is stuck at legacy slot, cannot revert

louvain
Download Presentation

Dynamic BSS Condition

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Dynamic BSS Condition Matthew Fischer Broadcom

  2. Proposal to Remedy NO comments • Legacy BSS causes ERP BSS to use legacy slot – all BSS in a chain of overlapping ERP BSS fall like dominoes • When legacy BSS disappears, entire chain of ERP BSS is stuck at legacy slot, cannot revert • Mixing of dynamic vs static bits in elements

  3. Objectives • Limit propagation of 802.11g directive information (short slot and protection required) found in beacons and probe responses to a physical extent of no more than one hop beyond the originator of the directive. • Separate static capability information from dynamic STA-directive information. • Change the name of the NonERP Information Element to Dynamic BSS Condition Element

  4. Objectives (2) • Extend Dynamic BSS Condition Element required usage to beacon and probe response transmissions by 802.11g STA in IBSS. • Establish rules for setting of bits PREQ and USESSLOT of Dynamic BSS Condition Element • Establish rules for setting GSTA bit of Capability Information Element

  5. Objectives (3) • Establish rules of propagation of received Dynamic BSS Condition Element information • Establish rules for ageing of information in received Dynamic BSS Condition Elements

  6. Locked Legacy Slot Problem (1) • 2 TGg BSS overlapping • Operating with short slot ERP1 ERP2

  7. Locked Legacy Slot Problem (2) • Legacy IBSS appears • Causing ERP1 to drop to legacy slot…. • Causing ERP2 to drop to legacy slot Legacy IBSS ERP1 ERP2

  8. Locked Legacy Slot Problem (3) • Legacy IBSS disappears • ERP1 remains at legacy slot, because adjacent ERP2 is operating at legacy slot, and vice versa… ERP1 ERP2

  9. Dynamic vs Static • Capability Element, currently defined: • Short Slot – dynamic – other bits are all static • NonERP Indication Element, currently defined: • Mitigation instructions – dynamic (from AP) – static (from STA, sort of) • Propose to: • Move all static together • Move all dynamic together

  10. 1 0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ESS IBSS CF Poll Req Priv-acy Short Pre-amble CCK- OFDM CF Poll-able PBCC Channel Agility Short Slot Octets 2 Figure 27 Capability information Field Updated Capability Element • Capability element: • Add gsta bit – to identify Legacy and non-Legacy • More properly, to discriminate 802.11g from non 802.11g • Make ShortSlot Capability = now STATIC Gsta

  11. Use of gsta bit • Rather than rely on presence or absence of nonERP Indication Element • Use gsta bit to determine if a beacon/PR came from legacy STA

  12. 1 0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Prop gdir Octets 2 Figure xx Dynamic BSS Condition Field Updated nonERP Element • Change name to Dynamic BSS Condition Element • propgdir = Propagate G Directives (I.e. same as “I directly observed a NonG device”) • Instruction to the recipient of the element • preq = protection required • Usesslot = Use short slot preq Use sslot

  13. Propagation of Directives • Domino problem is due to unlimited propagation of directives • Limit propagation to one hop • Covers the hidden node interferer possibilities • Accomplished with propgdir bit • Fixes locked legacy-slot problem • Other solution is to never propagate directives (I.e. 0 hops) • I.e. only respond to legacy STA that you can directly observe

  14. Propagation of Information • Use one-hop propagation of info: • Determine local values for D_propgdir, D_preq and D_usesslot, based on local information (D_ = desired) • I.e. gsta bit = 0 in RX beacon/PR OR presence of associated legacy STA forces D_propgdir = 1, else 0 • Determine values for L_propgdir, L_preq and L_usesslot based on OR of all received propgdir, preq and usesslot bits, respectively (L_ = local = mybss) • Corresponding F_ bits for foreign (Vs local)

  15. TX Values • Determine values to be transmitted (T_ = transmitted): • T_propgdir = D_propgdir • T_preq = D_preq + R_preq * R_propgdir • T_usesslot = D_usesslot * (R_usesslot + !R_propgdir)

  16. STA behavior • STA shall use protection mechanism if S_PREQ is TRUE • AP: s_preq = t_preq • STA in BSS: s_preq = d_preq + l_preq • STA in IBSS: s_preq = d_preq + l_preq + f_preq

  17. STA behavior (2) • STA shall use short slot if S_USESSLOT is TRUE • AP: s_usesslot = t_usesslot • STA in BSS: s_usesslot = d_usesslot + l_usesslot • STA in IBSS: s_usesslot = d_usesslot + l_usesslot + f_usesslot

  18. Ageing Received Information • Age Received information with timeouts • Timeout value 30 sec

  19. Include IBSS • The proposed text includes IBSS in the mechanisms to discover non-802.11g devices and generate and propagate directives in response to this information

More Related