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Issues With Off-channel TDLS

Issues With Off-channel TDLS. Authors:. Date: 2008-03-05. Abstract. Issues with off-channel Tunneled Direct Link (TDL) are presented for study group discussion. Is Off-Channel TDL in scope?. From item 5.2 Scope:

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Issues With Off-channel TDLS

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  1. Issues With Off-channel TDLS Authors: Date: 2008-03-05 Michael Livshitz, Metalink

  2. Abstract Issues with off-channel Tunneled Direct Link (TDL) are presented for study group discussion Michael Livshitz, Metalink

  3. Is Off-Channel TDL in scope? • From item 5.2 Scope: • This amendment defines a new Direct Link Setup (DLS) mechanism to allow operation with non-DLS capable access points and allow stations with an active DLS session to enter power save mode. The scope is specifically limited to modifications related to the DLS mechanism. • Off-channel operation does not contribute to the solution that allows DLS operations with legacy access points nor it helps enabling power save modes, therefore: • It seems like off-channel TDL is outside the scope of current TGz PAR Michael Livshitz, Metalink

  4. How useful is off-channel TDL? • The common view on usefulness of off-channel TDL: • The purpose of going off-channel is to take traffic out of a congested network and move it to an empty channel • The traffic needs to be exchanged somewhere, and it is better to do so on an empty channel than on a busy channel • However, • With limited unlicensed spectra available, the term “empty channel” becomes less and less practical. Even relatively under-utilized channel can become heavily used in the next instance with new load, or with new networks settling on it • Therefore, issues of coexistence, fairness in media access, effective spectrum sharing are becoming more important • The need for new bandwidth shall promote more effective utilization, (using new technologies, for example) Michael Livshitz, Metalink

  5. Problems with off-channel TDL • Off-channel DLS traffic may use significant amount of shared bandwidth without participating in network coexistence • STAs [participating in off-channel TDL] will not advertise their capabilities and policies (no beaconing). • STAs will not respond to probe requests • STAs will not respond to any 11k management frames • This makes other networks unaware of what is going on and impedes their decision in allocating and using shared resource Michael Livshitz, Metalink

  6. Examples of potential problems • Voice/Video network with ACM policies • Note that the problem is different from OBSS problem, since OBSS can be detected, managed and avoided • Negative impact on QoS enabled WLANs • WLANs with 11k radio resource management • 802.11n 20/40 coexistence mechanism • Off-channel is not detected, not avoided, resulting in mutual collision. Draft 802.11n 20/40 coexistence algorithm specifically addresses legacy OBSS • Intelligent channel selection for multimedia networks • AP scanning for better channels, STAs scanning for OBSSs are not capable of DLS traffic detection Michael Livshitz, Metalink

  7. Moving forward options • Option 1 • Do nothing. Resolve possible no-votes in comment resolution phase • Option 2 • Consider modifying PAR to include off-channel TDL support, and • Consider developing appropriate coexistence mechanisms, like • Scanning before going off-channel • Adding limited beaconing • Switching back on OBSS detection • Option 3 • Consider removing off-channel TDL from TGz draft specification • Other options? Michael Livshitz, Metalink

  8. Discussion and Straw Poll(s) Michael Livshitz, Metalink

  9. References • Draft IEEE P802.11z/D0.2, January 2008 (Draft Amendment to IEEE Std 802.11™) • P802.11z PAR • http://standards.ieee.org/board/nes/projects/802-11z.pdf Michael Livshitz, Metalink

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