1. doc.: IEEE 802.11-11/1515r0 Submission November 2011 Timo Koskela, Renesas Mobile CorporationSlide 1 802.11ah Wi-Fi Offloading Considerations Date: 2011-11-6 Authors:

2. doc.: IEEE 802.11-11/1515r0 Submission Abstract In our earlier contribution 1011r0 presented in June SF meeting we discussed that the offloading scenario should be evaluated with simulations to verify that 802.11ah would provide meaningful offloading solution –Offloading should not jeopardize end user experience. –Offloading capacity should give real relief to operators cellular network to justify investments. The approved motions in document 1294r1, the 802.11ah selected following supported channel widths: –1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz In this document we show Wi-Fi offloading simulation results (use case 3) on 16MHz channel width downclocked (10x) from 160Mhz 802.11ac PHY Slide 2Timo Koskela, Renesas Mobile Corporation November 2011

3. doc.: IEEE 802.11-11/1515r0 Submission Simulation Parameters The 1311r1 proposed to have same subcarrier spacing for all the supported channel widths –This results in 31.25 kHz spacing To achieve 16MHz channel width 160 MHz 802.11ac was downclocked with factor of 10 –Tenfold increase in symbol time –Affects also to the other timing related parameters Key parameters are presented in the table –802.11ac VHT PPDU format was used November 2011 Slide 3Timo Koskela, Renesas Mobile Corporation ParameterValue Symbol Time 40 us (32us + 8 us GI) SIFS 160 us Slot time 48 us MCS 0-7 (1/2 BPSK – 5/6 64 QAM) Bandwidth and Frequency 16 MHz at 900 MHz Number of subcarriers TOT/DATA/PILOT 484/16/468 Tx Power 20 dBm

4. doc.: IEEE 802.11-11/1515r0 Submission Simulation Scenario One access point –isolated deployment 10 active stations with FTP traffic –5 STAs downloading –5 STAs uploading TCP/IP layer modeled accurately 10 drops (60 seconds each) –stations uniformly randomly distributed, no mobility November 2011 Slide 4Timo Koskela, Renesas Mobile Corporation

5. doc.: IEEE 802.11-11/1515r0 Submission Description of the Performance Metrics Fairness: Jain’s Fairness Index is used –Measures fairness between the users and the index has maximum value when all STAs have the equal share of the resources Throughput: Throughput per STA seen at application layer Aggregate throughput: Aggregate throughput seen at application layer November 2011 Slide 5Timo Koskela, Renesas Mobile Corporation

6. doc.: IEEE 802.11-11/1515r0 Submission Simulation Results November 2011 Slide 6Timo Koskela, Renesas Mobile Corporation Average Jain’s index: –0.43 (1.0 is the optimum with equal rates, 0.1 is the worst one can get) Average aggregated throughput: –2669 kbit/s CDF of per STA achieved throughput

7. doc.: IEEE 802.11-11/1515r0 Submission Conclusions 16 MHz channel capacity is not utilized efficiently –Inadequate rates seen for the offloading use case –Only few STAs can be supported with high rates which results in poor fairness Downclocking increases the PHY and MAC overhead –Downclocking and large coverage area highlight the problems of CDF based access method 802.11ah is not able to support meaningful offloading with current numerology November 2011 Slide 7Timo Koskela, Renesas Mobile Corporation

8. doc.: IEEE 802.11-11/1515r0 Submission Strawpolls Should OFDM PHY characteristics (slot time, SIFS etc.) and PHY frame format of 11ah be reconsidered –Yes –No –Abstain Should the current MAC and DCF procedure be enhanced to obtain higher 11ah performance? –Yes –No –Abstain November 2011 Slide 8Timo Koskela, Renesas Mobile Corporation