doc.: IEEE /0338r1 Submission March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 1 DeepSleep: Power Saving Mode to Support a Large Number of Devices Date: Authors:

doc.: IEEE /0338r1 Submission Abstract In this contribution, we propose a power saving mechanism that supports low-power STAs in ah. March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 2

doc.: IEEE /0338r1 Submission Motivation To save power, STAs could reduce the time in active state. To save power, a STA could spend a long time in power saving mode. Upon waking up, the STA wakes up to communication shortly and then goes back to power save mode as soon as possible. March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 3

doc.: IEEE /0338r1 Submission Spend Less Time in Active State for Energy Efficiency Reducing backoff time and listening time could improve energy efficiency. –A STA with reduced CWmin has shorter contention time and could go back to power saving mode sooner –There are concerns about reducing CWmin Fairness to contention Collision probability To be fair, only STAs that have been stay in sleep mode for a while should be qualified for setting small CWmin value. March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 4

doc.: IEEE /0338r1 Submission Reduce Contention Nodes for Energy Efficiency With large number of devices, reducing channel contention improves energy efficiency A large percentage of STAs are configured to enter sleep mode to reduce contention and to save energy –Similar solutions to resolve issues caused by large number of STAs have been proposed for 11ah [1][2] March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 5

doc.: IEEE /0338r1 Submission Contention and Waste of Energy March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 6 Energy waste during this time period

doc.: IEEE /0338r1 Submission Proposal Overview We propose an enhanced mechanism to save power for low-power ah STAs –The low-power STAs (which have been stayed in sleep mode for a long time) has higher priority when it wakes up. These STAs could have shorter idle listening period and going back to power-saving mode sooner The channel access fairness is also considered. –Only STAs that do not access channel for a while are qualified for high priority access because of fairness March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 7

doc.: IEEE /0338r1 Submission Design Overview 1.STAs go to DeepSleep –Enter DeepSleep mode randomly If (P < Prob_Threshold) Optional extension: a STA considers its energy status –Stay in DeepSleep for a while (DeepSleep_Duration ) 2.STAs wake up –If the STA has slept for a long enough time The wake-up STA applies smaller contention window to have high priority to transmit. –Otherwise, The wake-up STA operates in the original mode March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 8

doc.: IEEE /0338r1 Submission Our proposal Algorithm: –Randomly Enter DeepSleep Mode if(P < Threshold) then{ Enter DeepSleepMode (Stay in sleep for DeepSleep_Duration) Bool_Sleep = TRUE; } –Wakeup if (Bool_Sleep) then{ CWmin = CW_Sleep; Bool_Sleep = FALSE; } else{ CWmin = CW_Original; } March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 9

doc.: IEEE /0338r1 Submission Simulation Settings March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 10 Use NS-2 simulator Number of devices : 100 traffic interval: 1s beacon period: 1s TX power: 550 mW RX power: 250 mW Idle power: 200 mW Sleep power: 40 mW CWmin_Orignal: 31 CWmin_DeepSleep: 15 DeepSleep_Duration : 10 beacon periods Case 1: 100 devices use the proposed scheme Case 2: 100 devices use default scheme Case 3: 50 devices with the proposed scheme, 50 default scheme

doc.: IEEE /0338r1 Submission Better Energy Efficiency March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 11

doc.: IEEE /0338r1 Submission Lower Collision Probability March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 12

doc.: IEEE /0338r1 Submission Stay in Sleep Mode Longer March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 13 Sleep time rate is defined as the time ratio that a STA is stayed in PSM mode. For example, sleep time rate = 0.95 implies a STA operates in active mode 5% of time and stays in power save mode 95% of time.

doc.: IEEE /0338r1 Submission Lower Retransmission Count March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 14 To successfully deliver a packet, how many time does a STA needs to transmit (e.g. transmission per packet delivered = 1, if there is no packet loss; transmission per packet delivered = 2, if the average re-transmission count is 1).

doc.: IEEE /0338r1 Submission The Same Packet Delivery Ratio March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 15

doc.: IEEE /0338r1 Submission Conclusions We proposed a power saving mechanism for the STAs. –Reducing the contention level caused by large number of devices. –Reducing the backoff time and channel listening time upon a STA wakes up. Simulation results show the proposed mechanism effectively improve energy efficiency. –Better energy efficiency –Lower collision probability –Stay in doze time more often –Lower collision probability Suitable for scenarios with a large number of lower- power STAs March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 16

doc.: IEEE /0338r1 Submission References [1] ah-dcf-enhancements-for-large- number-of-stas [2] ah-power-saving-possibilities-for- networks-supporting-a-large-number-of-stas March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 17

doc.: IEEE /0338r1 Submission Straw Poll (1) Do you agree that a power saving mechanism to reduce the channel sensing period should be developed in Specification Framework? –Y –N –A March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 18

doc.: IEEE /0338r1 Submission Straw Poll (2) Do you agree to use a smaller CWmin parameter when STAs wakes up after a long doze (e.g. with grouping)? –Y –N –A March 2012 Hung-Yu Wei, National Taiwan UniversitySlide 19