Legacy Fairness Enhancement in IEEE 802.11 Networks: Further Considerations

Investigating legacy fairness issues in IEEE 802.11 networks, this document explores methods to address throughput starvation of legacy stations due to enhanced Channel Clear Assessment (CCA) in High Efficiency (HE) stations. Two fairness methods, Legacy Frame Protection and PPDU Size Reduction, are evaluated through simulation studies to mitigate legacy starvations and contend with unfairness arising from multiple HE stations. Recommendations for fairness provisioning methods are discussed to improve coexistence between legacy and HE devices.

• Legacy Fairness
• IEEE 802.11
• CCA Threshold
• Fairness Methods
• Wireless Networks

lpre Follow

Uploaded on Oct 09, 2024 | 0 Views

Download Presentation

Please find below an Image/Link to download the presentation.

The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.

Presentation Transcript

1. Mar 2015 doc.: IEEE 802.11-15/0374r1 Further Considerations on Legacy Fairness with Enhanced CCA Date: 2015-03-10 Authors: Name John (Ju-Hyung) Son Geonjung Ko Affiliations WILUS Institute Address 263-2 Yangjae-dong, Seocho-gu, Seoul, Korea Phone +82-2-552-0110 email john.son@wilusgroup.co m greg.ko@wilusgroup.co m jinsam.kwak@wilusgrou p.com Jin Sam Kwak 9-1 Sunae-dong, Bundang-gu, Seongnam- si, Gyeonggi-do, Korea yd76.kim@sk.com +82-31-710-5378 Young Doo Kim SK Telecom +82-31-710-5377 hongseok.shin@sk.com Hong Seok Shin Submission Slide 1 John Son, WILUS Institute

2. Mar 2015 doc.: IEEE 802.11-15/0374r1 Abstract In [1], we investigated legacy fairness issues of enhanced CCA. Legacy STA s throughput can be starved from HE STA s increased CCA threshold and continuous channel occupation. In this contribution, we evaluate two fairness methods: Legacy Frame Protection [2]where HE STA does not apply increased CCA threshold on legacy frames; PPDU Size Reduction where HE STA limits its PPDU sizes (or TXOP duration [3]) when they obtain a channel with increased CCA threshold. From simulation studies, we show that the above methods effectively mitigate legacy starvations up to moderate CCA threshold levels. Also, we report a new contention unfairness that may become severe when there are multiple HE STAs around Leg STAs. Submission Slide 2 John Son, WILUS Institute

3. Mar 2015 doc.: IEEE 802.11-15/0374r1 Recap: Legacy Fairness Issues [1] 1. CCA threshold unfairness 2. Airtime unfairness HE CCA (e.g. -82dBm) range of Legacy STA CCA (e.g. -62dBm) range of HE STA HE Leg HE Leg HE Data Data backoff HE Data Data HE Data Data backoff backoff backoff Leg Data Leg defer backoff defer defer HE STA applies increased CCA threshold on Legacy frames HE STA can continuously access the channel thus unfair to Legacy STA Two HE STAs apply increased CCA threshold on mutual HE frames HE STAs can continuously occupy the channel thus unfair to Legacy STA (Solution) Legacy Frame Protection (Solution) PPDU Size Reduction Submission Slide 3 John Son, WILUS Institute

4. Mar 2015 doc.: IEEE 802.11-15/0374r1 Fairness Provisioning Methods Legacy Frame Protection PPDU(TXOP) Size Reduction If RSSI>= CCA-SD , If preamble passes, If MYDATA, receive the packet. If OBSS HE PPDU, apply CCA-SD-HE If MYBSS HE PPDU, apply CCA-SD If non-HE PPDU, apply CCA-SD If preamble fails, apply CCA-ED HE Data Data defer backoff backoff HE Data Data defer backoff backoff Leg Data backoff remaining backoff For PPDU transmission, HE STA limits its PPDU size to the OBSS HE PPDU (e.g. limiting the # of MPDUs in A-MPDU) HE STA applies increased CCA threshold when OBSS HE frame is observed HES STA applies the legacy CCA threshold when non-HE frame is observed TXOP HE Data Data TXOP Data HE Data Data Data Leg Data back off For TXOP-based transmission, HE STA limits its TXOP duration to the OBSS HE STA s TXOP duration [3][7] Submission Slide 4 John Son, WILUS Institute

5. Mar 2015 doc.: IEEE 802.11-15/0374r1 Simulation Settings Topography/Channel Model [4][5] 1 floor, 1x2 apartments per floor, each apt. is 10m x 10m x 3m 1 AP, 4 STAs per apt. (1 HE STA, 3 Legacy STAs) AP/STA at random (x,y) locations, all with z=1.5 5GHz, all BSS has the same 80MHz channel (Reuse 1) Pathloss model with Wall/Floor penetration loss, 5dB std log-normal shadowing, no multipath fading Le g Le g Le g Le g HE HE Le g Le g HE HE Traffic DL+UL full buffer Packet size: 1500 Byte, Max # of MPDUs in A-MPDU=8 MCS: Fixed MCS 0 CCA threshold CCA-SD: -82dBm CCA-SD-HE: -82, -72, -62, -52 dBm Submission Slide 5 John Son, WILUS Institute

6. Mar 2015 doc.: IEEE 802.11-15/0374r1 Throughput & Fairness ? ? No? method? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? LFP? only? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? LFP+PSR? Jain's? Fairness? Index? [6]? (HE? STA? vs.? Leg? STA)? 25? 1? LFP+PSR? Leg? STA? HE? STA? LFP? only? 0.9? 20? No? method? Fairness? Index? Throughput? (Mbps)? 0.8? 15? 0.7? 10? 0.6? 5? 0.5? 0? (-82dBm)? (-72dBm)? (-62dBm)? (-52dBm)? (-82dBm)?(-72dBm)?(-62dBm)?(-52dBm)? (-82dBm)?(-72dBm)?(-62dBm)? (-52dBm)? CCA-SD-HE? (-82dBm)?(-72dBm)?(-62dBm)?(-52dBm)? CCA-SD-HE? Without fairness method large unfairness between HE STA vs. Leg STA (starvation of Leg STA) as CCA threshold increases. LFP (Legacy Frame Protection) only prevent legacy starvation up to moderate CCA threshold (-72dBm). LFP+PSR (PPDU Size Reduction) prevent legacy starvation up to high CCA threshold (-62dBm). Submission Slide 6 John Son, WILUS Institute

7. Mar 2015 doc.: IEEE 802.11-15/0374r1 Contention unfairness Le g X Legacy? STA's? avg.? rela ve? throughput? (all? LFP+PSR? applied)? HE 1 Le g HE 1? 1HE-3LEG? BSS? 3HE-1Leg Case Example HE HE 2HE-2Leg? BSS? 0.9? 3HE-1Leg? BSS? HE 3 HE 2 0.8? HE HE 0.7? Ra o? 0.6? HE Data Data backoff HE 1 HE 2 HE 3 0.5? Data defer backoff backoff 0.4? remaining backoff remaining backoff Data defer backoff 0.3? defer backoff defer 0.2? Leg X (-82dBm)? (-72dBm)? (-62dBm)? (-52dBm)? defer defer backoff CCA-SD-HE? Contention unfairness HE STA can decrement its Contention Window value sensing idle channel with increased CCA threshold. Leg STA cannot decrement its Contention Window value sensing busy channel with legacy CCA threshold. It becomes severe when Leg STA is with many HE STAs in a BSS. Submission Slide 7 John Son, WILUS Institute

8. Mar 2015 doc.: IEEE 802.11-15/0374r1 Summary Legacy fairness is an important requirement when 11ax designs spatial reuse technologies. In this contribution, we demonstrated that previously discussed two fairness methods can preserve legacy fairness. We also identified the Contention unfairness issue that needs further discussions in 11ax. Submission Slide 8 John Son, WILUS Institute

9. Mar 2015 doc.: IEEE 802.11-15/0374r1 References [1] 11-15/0085r1, Legacy Fairness Issues of Enhanced CCA [2] 11-14/0629r0, Further discussions on Enhanced CCA [3] 11-14/0637r0, Spatial Reuse and Coexistence with Legacy Devices [4] 11-14/0980r6, Simulation Scenarios [5] 11-14/0571r7, Evaluation Methodology [6] Jain, R.; Chiu, D.M.; Hawe, W. (1984). "A Quantitative Measure of Fairness and Discrimination for Resource Allocation in Shared Computer Systems". DEC Research Report TR-301. [7] IEEE 802.11ah D4.0, 9.50.4 TXOP-based sectorization operation Submission Slide 9 John Son, WILUS Institute