1 / 17

DeepSleep: Power Saving Mode to Support a Large Number of Devices

This paper proposes a power-saving mechanism for low-power STAs in 802.11ah that reduces contention and improves energy efficiency by allowing STAs with longer sleep periods to have higher priority access to the channel.

cmcnally
Télécharger la présentation

DeepSleep: Power Saving Mode to Support a Large Number of Devices

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DeepSleep: Power Saving Mode to Support a Large Number of Devices Date: 2012-03-12 Authors: Hung-Yu Wei, National Taiwan University

  2. Abstract • In this contribution, we propose a power saving mechanism that supports low-power STAs in 802.11ah. Hung-Yu Wei, National Taiwan University

  3. 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. Hung-Yu Wei, National Taiwan University

  4. 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. Hung-Yu Wei, National Taiwan University

  5. 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] Hung-Yu Wei, National Taiwan University

  6. 802.11 Contention and Waste of Energy Energy waste during this time period Hung-Yu Wei, National Taiwan University

  7. Proposal Overview • We propose an enhanced mechanism to save power for low-power 802.11ah 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 Hung-Yu Wei, National Taiwan University

  8. Design Overview • 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 ) • 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 802.11 mode Hung-Yu Wei, National Taiwan University

  9. 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; } Hung-Yu Wei, National Taiwan University

  10. Simulation Settings • 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 802.11 scheme • Case 3: 50 devices with the proposed scheme, 50 default scheme Hung-Yu Wei, National Taiwan University

  11. Better Energy Efficiency Hung-Yu Wei, National Taiwan University

  12. Lower Collision Probability Hung-Yu Wei, National Taiwan University

  13. Stay in Sleep Mode Longer 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. Hung-Yu Wei, National Taiwan University

  14. Lower Retransmission Count 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). Hung-Yu Wei, National Taiwan University

  15. The Same Packet Delivery Ratio Hung-Yu Wei, National Taiwan University

  16. 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 Hung-Yu Wei, National Taiwan University

  17. References • [1] 11-11-1255-00-00ah-dcf-enhancements-for-large-number-of-stas • [2] 11-12-0028-01-00ah-power-saving-possibilities-for-networks-supporting-a-large-number-of-stas Hung-Yu Wei, National Taiwan University

More Related