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802.11ah Wi-Fi Offloading Considerations

802.11ah Wi-Fi Offloading Considerations. Authors:. Date: 2011-11-6. 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

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802.11ah Wi-Fi Offloading Considerations

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  1. 802.11ah Wi-Fi Offloading Considerations Authors: Date: 2011-11-6 Timo Koskela, Renesas Mobile Corporation

  2. 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 Timo Koskela, Renesas Mobile Corporation

  3. 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 Timo Koskela, Renesas Mobile Corporation

  4. 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 Timo Koskela, Renesas Mobile Corporation

  5. 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 Timo Koskela, Renesas Mobile Corporation

  6. Simulation Results • 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 Timo Koskela, Renesas Mobile Corporation

  7. 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 Timo Koskela, Renesas Mobile Corporation

  8. 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 Timo Koskela, Renesas Mobile Corporation

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