doc.: IEEE 802.11-12/0130r0 Submission January 2012 Seunghee Han, LG Electronics Slide 1 Beacon Reception of Long Sleeper Date: 2012-01-16 N am e A ffiliations A ddress Phone em ail Seunghee H an LG Electronics LG R& D Com plex A nyang-Shi, K yungki-D o, K orea seunghee.han@ lge.com Y ongho Seok LG Electronics [email protected]H yangsun Y ou LG Electronics [email protected]Jonghyun Park LG Electronics [email protected]Seunghee H an LG Electronics Jinsam Kw ak LG Electronics M inyoung Park IntelCorp. Tom Tetzlaff IntelCorp. Em ily Q i IntelCorp. Y ong Liu M arvell H ongyuan Zhang M arvell Raja Banerjea M arvell M atthew Fischer Broadcom Eric W ong Broadcom Authors:
Transcript
doc.: IEEE 802.11-12/0130r0
Submission
January 2012
Seunghee Han, LG ElectronicsSlide 1
Beacon Reception of Long Sleeper
Date: 2012-01-16
Name Affiliations Address Phone email Seunghee Han LG Electronics LG R&D Complex
Name Affiliations Address Phone email Simone Merlin Qualcomm
Zhi Quan Qualcomm
Santosh Abraham Qualcomm
Hemanth Sampath Qualcomm
VK Jones Qualcomm
Menzo Wentink Qualcomm
ChaoChun Wang MediaTek
James Wang MediaTek
Jianhan Liu MediaTek
Vish Ponnampalam MediaTek
James Yee MediaTek
Osama Aboul-Magd
Huawei
Edward Au Huawei
Lin Cai Huawei
Kim Chang Huawei
Yunsong Yang Huawei
Authors:
doc.: IEEE 802.11-12/0130r0
Submission
Introduction
• TSF (Time Synchronization Function) timer accuracy– For STAs in a long sleep state (e.g., over 10 min.), problems of the
TSF timer accuracy may arise• Example: When the timer accuracy is ±0.01%, after 1000s, it becomes
±100ms
– Due to the expanded possible TSF timer offset, such longer sleeper may not easily find periodic beacon frames
January 2012
Seunghee Han, LG ElectronicsSlide 3
doc.: IEEE 802.11-12/0130r0
Submission
Introduction
• Most sensor devices in 11ah are long sleepers [1,2]
– Current spec. states that the accuracy of the TSF timer shall be no worse than ±0.01%• Considering the worst case accuracy, after 1000s the time offset
becomes ±100ms, almost like a beacon interval
• But, if the TSF timer accuracy of an AP is ± 0.001%, TSF timer error of the AP is ±10ms when the sleep period is 1000s
– If TSF timer error becomes larger, anticipating Target Beacon Transmission Time (TBTT) becomes much harder• To a STA listening to a Beacon frame, it should wake up at 100ms
before for ±0.01% timer accuracy (the worst case)
January 2012
Seunghee Han, LG ElectronicsSlide 4
doc.: IEEE 802.11-12/0130r0
Submission
Beacon Reception of Long Sleeper
• TSF timer accuracy information from AP– If a STA knows TSF time accuracy information of an AP, it can
calculate the TSF timer error occurred during its sleep period
– Then, the STA can wake up at more exact time and it can reduce the unnecessary power consumption
January 2012
Seunghee Han, LG ElectronicsSlide 5
doc.: IEEE 802.11-12/0130r0
Submission
Beacon Reception of Long Sleeper
• Actual TSF timer accuracy– Power saving gain of the proposal depends on the actual TSF
timer accuracy value of AP & STA• Proposal: Announce the TSF timer accuracy information of AP to
STAs
• If the accuracy isn’t much better than the worst case (±100 ppm), the effect of the TSF timer accuracy information is insignificant
– Actual timer accuracy• In general, oscillator accuracy value for WLAN is ±1ppm ~ ±50ppm
– AP timer accuracy: ±20ppm, STA timer accuracy : ±10ppm
– STA knows its timer accuracy
– STA w/ TSF timer accuracy can obtain power saving gain of (78-30)/78 = 61.5%
January 2012
Seunghee Han, LG ElectronicsSlide 8
doc.: IEEE 802.11-12/0130r0
Submission
Beacon Reception of Long Sleeper
• Advantages of the TSF timer accuracy information– More flexible for various TSF timer accuracy values
• STA can predict TBTT more accurately for various TSF timer accuracy values
• E.g. 1) Wi-Fi Direct– A Group Owner (GO) stays awake and transmits beacon frames– This operation requires large power consumption– To reduce the power consumption, this GO can increase clock interval, even
though it has an accurate oscillator– Then, the timer accuracy of this GO will become worse
– But, overhead for TSF timer accuracy information is very small• TSF timer accuracy information can be transmitted in Association Response• This information requires only few bytes
January 2012
Seunghee Han, LG ElectronicsSlide 9
doc.: IEEE 802.11-12/0130r0
Submission
Conclusions
• Longer sleeper may not easily find periodic beacon frames
• For reducing the power consumption of listening to Beacon frame, an AP may provide its TSF timer accuracy information to a long sleeper– Long sleeper can wake up at more exact beacon reception time
January 2012
Seunghee Han, LG ElectronicsSlide 10
doc.: IEEE 802.11-12/0130r0
Submission
References
[1] Rolf de Vegt, “Potential Compromise for 802.11ah Use Case Document,” 11-11/457r0.
[2] Minho Cheong, “TGah Functional Requirements and Evaluation Methodology,” 11-11/905r4.
January 2012
Seunghee Han, LG ElectronicsSlide 11
doc.: IEEE 802.11-12/0130r0
Submission
Straw Poll 1
• Do you support that an AP may provide its TSF timer accuracy information to non-AP STAs ?
