Panasonic Singapore Laboratories TG5 Teleconference #3 21/02/2006 Michael Sim Panasonic Singapore Laboratories michael.simhc@sg.panasonic.com

Time Synchronization (Overview) In 15.3, a PNC provides time synchronization to all DEVs and child/neighbor piconets. (section 8.6 Synchronization) In 802.11 IBSS mode (ad hoc mode where EVERY device beacons) time synchronization, every station maintains a TSF (Time Synchronization Function) timer. Each device adopt the timing received from beacon or any probe response that has a TSF value later than its own TSF timer. (section 11.1 Synchronization) In time synchronization, we synchronized to a reference device rather than a “Slot Boundary” or a “BP start time” because those are relative and may be different from each device’s perspective due to clock inaccuracy. Mentioned in doc 05-0469-01 slide 15, that for distributed beaconing to work optimally, how to do MS or time synchronization need to be tackled 2019/6/16 Panasonic Singapore Lab

Time Synchronization (How?) Suggestions: Use similar TSF as 802.11 Every beacon includes TSF timer Every device follows the fastest/slowest TSF and its adopt slot boundary Philips proposed following the fastest device in guard interval Clarifications: Non-BP approach have the option to synchronize slot boundary using standard methods stated above For distributed beaconing to work optimally, non-BP approach only need to synchronize slot-boundary For BP approach, not just slot boundary need to be synchronized, the start of superframe need to synchronized such that all start at the same slot 2019/6/16 Panasonic Singapore Lab

Time Synchronization (Details) Using guard time for synchronization: Note: For Non-BP approach, do not need “late start guard time” as CAP is contention based RX-TX turnaround time is 10µs for 15.3 PHY Reference for 15.3 guard time calculation in section 8.4.3.6 Guard Time Non-BP approach BP approach B CAP B Early start Guard time Early start Guard time Early start Guard time Beacon CAP Beacon Beacon RX-TX turnaround time RX-TX turnaround time RX-TX turnaround time Late start Guard time RX-TX turnaround time 2019/6/16 Panasonic Singapore Lab

Panasonic Singapore Lab Power Saving Issue How much power does it require to switch a PHY from RX to TX (and vice-versa)? Does switching PHY to RX/TX mode for beacon frame TX or RX constitutes significant power issue? Let: PS be power consumed to switch to PHY RX/TX mode TS = RX-TX turnaround time PSRX be the power consumed to be in RX mode for duration of TS PBTX and PBRX be the power required to receive and transmit beacon frame respectively Question 1: Is PS >> PRX ? Question 2: How much power does it take for a particular device for beaconing? (Assume N beaconing devices) 2019/6/16 Panasonic Singapore Lab

Panasonic Singapore Lab Power Calculation (1) Case 1: Non-BP Approach: Assumption: Do not include power consumed while listening in guard time Power used: = 2PS + PBTX + (PS + PBRX)(N-1) = [PBTX + (N-1)PBRX] + (N+1)PS x (N-1) PS PBTX PS PS PBRX … … 2019/6/16 Panasonic Singapore Lab

Panasonic Singapore Lab Power Calculation (2) Case 2: BP Approach: Assumption: Do not include power consumed while listening in guard time Do not include power consumed while listening to additional 3 announcement slots Power Used: = PS + PBRX + (PRX + PBRX)M + PS + PBTX + PS + PBRX + (N-M-3)(PRX + PBRX) + PS = [PBTX + (N-1)PBRX] + 4PS + (N-3)PRX 1 Beacons x M x 2 x (N–M–3) PS PBRX PRX PBRX PS PBTX PS PBRX PRX PBRX PS … … 2019/6/16 Panasonic Singapore Lab

Panasonic Singapore Lab Power Calculation (3) Verdict: On top of power required to RX and TX beacon frames, Non BP method needs additional: (N+1)PS BP method needs additional: 4PS + (N-3)PRX If PS ≈ PRX, Power required for both is about the same Note that: BP method have additional guard time and RX time during guard time and is not considered in calculation BP method requires additional 3 announcement slots which is also not considered 2019/6/16 Panasonic Singapore Lab

Already provide backward Power Saving Issue (2) What if PS >> PRX ? If so, to provide backward compatibility to 15.3, in using beaconing using beacon period + additional PN beaconing, isn’t it a power issue? BP approach Non-BP approach < + Already provide backward compatibility to 15.3 2019/6/16 Panasonic Singapore Lab

Panasonic Singapore Lab In Summary… Time synchronization is important for distributed beaconing Provide slot boundary synchronization Optimal use of medium access time Details need to be worked out. (Good news: There are existing methods we can use ) Panasonic proposal provides for time synchronization Same time synchronization method can be used for beaconing or non-beaconing approach Non-beaconing approach does not need to synchronize superframe start time Power consumption in switching from RX to TX (and vice versa) for beacon TX and RX is lesser in non-beaconing approach since inherently it is already fully compatible with 15.3 superframe structure and does not need to perform additional PN beaconing 2019/6/16 Panasonic Singapore Lab