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Doc.: IEEE 802.11-01/319 Submission May 2001 Georg Dickmann, BridgeCo AG. AV Timing BridgeCo AG Georg Dickmann

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Presentation on theme: "Doc.: IEEE 802.11-01/319 Submission May 2001 Georg Dickmann, BridgeCo AG. AV Timing BridgeCo AG Georg Dickmann"— Presentation transcript:

1 Doc.: IEEE /319 Submission May 2001 Georg Dickmann, BridgeCo AG. AV Timing BridgeCo AG Georg Dickmann

2 Doc.: IEEE /319 Submission May 2001 Georg Dickmann, BridgeCo AG. Principles Implicit Time Distribution –Lock on FIFO level associated with streams Explicit Time Distribution –Synchronize timers throughout AV network, timers are used to generate timestamps, recover clocks associated with each stream based on timestamp and local timer (IEC 61883)

3 Doc.: IEEE /319 Submission May 2001 Georg Dickmann, BridgeCo AG. Principles (2) Timing Master HC Wireless Node Wired Node

4 Doc.: IEEE /319 Submission May 2001 Georg Dickmann, BridgeCo AG. Timers Use wireless TSF timer for AV –Wireless timers need to be adjustable even in AP –Granularity/rate of 1  s is not appropriate Use independent timer –Any granularity/rate is feasible –Isochronous multicast/broadcast channel for clock distribution required –Timing master can be non-HC

5 Doc.: IEEE /319 Submission May 2001 Georg Dickmann, BridgeCo AG. Independent Timer Updates Sync. as in HL/2 sublayer for IEEE Every (E)STA latches timer value upon reception of a beacon. 2.The timing master broadcasts its latched timer value within the BSS 3.Each timing slave adjusts its local timer by the difference between received time and latched time.

6 Doc.: IEEE /319 Submission May 2001 Georg Dickmann, BridgeCo AG. Independent Timer Update (2) Multicast channel from timing master to timing slaves required (the AP/HCF may be required to relay the timing channel) Define dynamic selection of timing master

7 Doc.: IEEE /319 Submission May 2001 Georg Dickmann, BridgeCo AG. Sources of clock error (Local oscillator deviation) x (Update Interval Length) Granularity of timer Beacon processing delay Signal propagation delay

8 Doc.: IEEE /319 Submission May 2001 Georg Dickmann, BridgeCo AG. Bounds on clock error IEC61883 requires jitter < 400ns AES11 requires any two digital audio signals to have a relative phase offset < 5% of sampling interval (approx. 1  s for 48 kHz sampling clock)

9 Doc.: IEEE /319 Submission May 2001 Georg Dickmann, BridgeCo AG. Implications on Introduce tight bounds on both TSF timer jitter and phase offset between AV enabled AP/HC and (E)STAs Ensure efficient operation with beacon periods < 10 ms Provide multicast channel for time distribution


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