Proposed ERTS & ECTS Mechanisms

Proposed ERTS & ECTS Mechanisms Author: Matthew Sherman AT&T Labs - Research 180 Park Avenue Florham Park, NJ 07932 973-236-6791 mjsherman@att.com Date: March 12, 2001 Matthew Sherman, AT&T Labs - Research

Problem addressed • 802.11e is developing mechanisms to support QoS • Many situations when the ability to cause groups of STA to cease transmissions would be useful • Accommodate TBTT for Beacon transmission • Accommodate protocol enhancements / coexistence • HCF / Token passing schemes, Bluetooth, HIPERLAN, etc • Hidden terminals • Overlapped BSS mitigation • Would like technique applied to also work with Legacy STA (LSTA) • Would like ability to differentiate between Legacy and groups of 802.11e STA (ESTA) Matthew Sherman, AT&T Labs - Research

Approach to Problem • Develop method to Set NAV in a STA group • Develop method to Reset NAV in a STA group • Deferred to later 802.11 meeting • Use existing frame formats as much as possible • Enhances compatibility with LSTA Matthew Sherman, AT&T Labs - Research

Approach to Problem (Cont.) • Play with usage / interpretation of RTS & CTS • Later CF-End as well • Have ESTA use Addresses for qualifiers and signaling • Apply Duration field based on contents of Addresses • Based signaling / qualifiers on Address types • Unicast • Multicast • Broadcast • Chose mappings that are consistent with current usage of address fields in standard Matthew Sherman, AT&T Labs - Research

Suggested ECTS Mechanisms • Enhance CTS (ECTS) usage to allow setting Duration/ID field to any valid Duration value • Broadens context for Duration field use • Enhance CTS usage to allow any valid address in RA field • LSTA will always set NAV for duration indicated • Rules for Compliant ESTA will vary (See Chart) • Non-compliant ESTA act as LSTA • Allow use of PIFS with this message for preferential media access (EAP / EPC only) Matthew Sherman, AT&T Labs - Research

Map of New Capabilities (CTS) Matthew Sherman, AT&T Labs - Research

Suggested ERTS Mechanism • Enhance RTS (ERTS) usage to allow setting Duration/ID field to any valid Duration • Broadens context for Duration field use • Enhance RTS usage to allow group addresses in TA field • LSTA will always set NAV for duration indicated • Compliant ESTA do not set NAV if not in group • Non-compliant ESTA act as LSTA • ESTA forward CTS if addressed in RA • Allow use of PIFS with this message for preferential media access (EAP / EPC only) Matthew Sherman, AT&T Labs - Research

Map of New Capabilities (RTS) Matthew Sherman, AT&T Labs - Research

What Enhancements Accomplish • If no LSTA • Can set NAV independently in any group of ESTA • Some ability to control remote groups via RTS/CTS relay • Since can have “Group” of one, can set for single ESTA as well • If LSTA are present • Must treat as special case • Always part of addressed group Matthew Sherman, AT&T Labs - Research

Comments on Mechanisms • No new frame formats required • Fully backward-compatible • Additional RTS mappings possible • Open to other mappings • Open to partial acceptance of mappings • Implementation of mechanisms are optional • Indicating support of mapping mandatory in ESTA • Duration field in other frame types could also be used to reserve channel • RTS/CTS seemed most appropriate Matthew Sherman, AT&T Labs - Research

Comments specific to Overlapped BSS • Goal of new mappings is to allow suppression of groups of terminals in overlap • Technique assumes ability exists to assign terminals to groups • Currently those techniques are considered beyond 802.11 • Techniques are identified in 802.1 • Best if applied with ability to solicit interference info from STA • Which other STA are heard at what power level • Mechanisms being developed using Generic Action Frame • Existing proposed elements may need to be enhanced Matthew Sherman, AT&T Labs - Research

Example Applications of New Mechanisms Matthew Sherman, AT&T Labs - Research

Legacy Tx Suppressed RA=Broadcast Prior TX ECTS ETx1 ETx2 ETxN B TBTT NAV Set by Legacy STA PIFS Example ECTS UsageReduction of TBTT Overrun* * Assumes ESTA knows not to overrun TBTT ETxX are transmissions by ESTA Matthew Sherman, AT&T Labs - Research

RA=Senders Address Unsolicited Tx Suppressed Prior Tx ECTS Unknown or Foreign Protocol NAV Set by all STA Duration Expires (NAV Resets) PIFS Example ECTS UsageSharing with Unknown Protocol Matthew Sherman, AT&T Labs - Research

RA=Group 12 Tx to/from ESTA in overlap BSS1 Group 12 Suppressed BSS1 Tx12 Tx12 ECTS Tx1 Tx1 RA=Group 21 BSS2 Group 21 Suppressed Tx to/from ESTA in overlap BSS2 ECTS Tx2 Tx2 Tx21 Tx21 Legend: Group 12 - ESTA in BSS1 that interfere with BSS2 Group 21 - ESTA in BS21 that interfere with BSS1 Tx12 - Transmissions from any BSS 1 STA Tx21 - Transmissions from any BSS 2 STA Tx1 - Transmission from BSS 1 STA not in overlap Tx2 - Transmission from BSS 2 STA not in overlap Example Usage - BSS Overlap* * Multicast addresses for groups 1 and 2 need not be assigned (Never necessary to suppress groups 1 or 2) Matthew Sherman, AT&T Labs - Research

TA=Group A RA=RSTA RA=Group A Hidden STA suppressed ERTS ECTS ERTS ECTS Hidden Node Suppressed Continued Suppression Example UsageHidden STA Suppression* * Assumes Hidden ESTA is only STA in group to begin with (Group A) Matthew Sherman, AT&T Labs - Research

Proposed ERTS & ECTS Mechanisms