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Wi-Fi Interference Measurement in Korea (Part I)

This document predicts when Korea's 5GHz band will be saturated by Wi-Fi devices and presents measurement results on Wi-Fi hotspots in Korea.

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Wi-Fi Interference Measurement in Korea (Part I)

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  1. Wi-Fi Interference Measurement in Korea(Part I) Authors: Date: 2013-05-15 Minho Cheong (ETRI)

  2. Abstract This document supports one prediction on when Korea’s 5GHz band will be also saturated by Wi-Fi devices and some simple measurement results on Wi-Fi hotspot in Korea. Minho Cheong (ETRI)

  3. Contents • Introduction • When will 5GHz band be saturated? • Without Wi-Fi tech. enhancement • Wi-Fi Interference Measurements in Korea • Scenario #1 (Train Station) • Scenario #2 (Underground Mall) • Comparison between two scenarios • Conclusion and Next steps Minho Cheong, ETRI

  4. Introduction • Current Status of 2.4GHz/5GHz Unlicensed Band and Wireless Devices • IEEE 802.11b/g : 2.4GHz, IEEE 802.11a/ac : 5GHz, IEEE 802.11n : 2.4/5GHz • IEEE 802.15.1(Bluetooth): 2.4GHz • IEEE 802.15.4/4a(low rate WPAN/ZigBee): 2.4GHz • Microwave oven(2450MHz), Cordless phone(2.4/5GHz), Video Transceiver (2.4/5GHz) • Wireless Speaker (2.4/5GHz), Some harmonics of cellular (2.4GHz) • Interference sources • Wi-Fi interferences from OBSS (at the same channel or the overlapped channels) • Non-Wi-Fi interferences Minho Cheong, ETRI

  5. Introduction 5.15~5.35GHz (200MHz) 5.47~5.65GHz (180MHz) 5.725~5.825GHz (100MHz) (75MHz) Band 20MHz (19 Channels) 40MHz (9 Channels 80MHz (4 Channels) 160MHz (1 Channels) 2400~2483.5MHz (83.5MHz) • 2.4GHz band and 5GHz band • 5.35-5.47GHz, 5.825-5.925GHz are now under consideration • In Korea, 5.650-5.725GHz cannot be used for Wi-Fi due to the Broadcast relay service Band 20MHz (13 Channels) Broadcast 1 2 3 4 5 6 7 8 9 10 11 12 13 Minho Cheong, ETRI

  6. Introduction • Current Status of Wi-Fi Deployment in Korea • Over 50 % of cellular traffic is already offloaded to the Wi-Fi • World-most density of AP deployment for Seoul metropolitan area • Use of Wireless controllers • Have been widely used for security, billing, data gathering, et, al. since 2005. < CommercialWi-Fi Deployment Korea> * Wi-Fi in the fixed phone included [Ref]: Jae-Hyun Kim, ‘Wi-Fi Workshop’ 2012.11.26.) Minho Cheong, ETRI

  7. Introduction Potential Sources of the saturation of Wi-Fi band • Radio interferences from neighboring Wi-Fi and non-Wi-Fi • Statistical analysis of Korea’s regulation body says that • 40~60% degraded by microwave oven, 23% degraded by RFID, 13% degraded by Bluetooth • 6~95% degraded by co-channel interferences from other Wi-Fi’s • Lack of shared information among neighboring AP’s about each other • Mitigation of Wi-Fi interferences cannot be possible now • Various generations of Wi-Fi devices are inevitably co-existed • Network throughput may be approaching very low due to legacy devices and conventional beaconing with very low data rate • Lots of waste of air-time due to flooding during probe response • When initial selection of channels, packets flooding may be induced highly depending on the channel condition and number of STAs to be associated Minho Cheong, ETRI

  8. When will 5GHz be saturated without Wi-Fi technology enhancement? • As well-known, Korea has world-most deployment density of hot spots in Seoul metropolitan area. • A couple of years ago, 2.4GHz band is already too saturated to try any internet access in downtown in Seoul. • Since then, lots of new Wi-Fi devices (firstly 802.11n, nowadays quickly transferring to 802.11ac) has explosively been spread at the 5GHz band mainly from huge number of smart-phones. • FYI, all three biggest Korea’s operators have already done their deployment of 4G-LTE nationwide and more than 50% of Korea’s cellular traffic is already being offloaded to Wi-Fi, which may result in very quick saturation of 5GHz band as well. • So, it seems very meaningful to predict on when Korea’s 5GHz band will be saturated again without any Wi-Fi technology enhancement, as a typical benchmark to other countries as well. Minho Cheong, ETRI

  9. When will 5GHz be saturated without Wi-Fi technology enhancement? • In order to partially solve this problem, Korea government announced “Channel Usage Guideline for 2.4GHz Band” on Jan. 18, 2012. • Recommend to use channel 1 or 5 or 9 or 13 • Recommend to use Bandwidth smaller than 22MHZ • Recommend to set an easily-readable SSID • However, contrary to the intention, • This guideline seems not to have success • Because of many private AP’s which does not follow the recommendation [Ref] KCC’s Guideline (since 2012.01.18) Minho Cheong, ETRI

  10. When will 5GHz be saturated without Wi-Fi technology enhancement? • Let me compare these two following cases each other • Utilization of 2.4GHz band in 2010 vs. utilization of 5GHz band in 2015 • Note 1) Year 2010 is the year when Korea’s 2.4GHz is informed as quite saturated • Note 2) Year 2015 is believed as the first or second year 802.11ac will overwhelm 802.11n • Firstly, when comparing the allowable frequency resources for Wi-Fi, • Resource of 2.4GHz band vs. Resource of 5GHz band is almost 1 : 6 • Because currently allowable resource in 2.4GHz and 5GHz is 83MHz and 475MHz, respectively. • Secondly, when comparing the weighted sum of “number of each type of device multiplied by its occupying bandwidth”), • Estimated resource occupancy of 2.4GHz vs. 5GHz is almost 1 : 11 • Assuming 11a/b/g as 20MHz, 11n(40MHz), 11ac(80MHz for first 2 years, 160MHz for the subsequent days as a guess) • When estimating the number of each specific type of Wi-Fi devices, I accumulated during the latest a couple of years before the very year considered, thinking general life cycle of those. • I also referred to “InStat’ 2011, 2012” to estimate the number of Wi-Fi devices for each generation type in the following years. Minho Cheong, ETRI

  11. When will 5GHz be saturated without Wi-Fi technology enhancement? • Additional considerations possible • Assuming the similar TX power regardless of Wi-Fi generation • 802.11ac may be more vulnerable to interferences because it is more likely to have larger MCS’s than previous days • When 802.11ac overwhelms, there may come more kind of applications which is hardly imagined before • Because dynamic BW/channel switching with the use of the operating mode notification is made possible since 802.11ac, it may make some partially overlapped interferences in the frequency domain when it is not informed enough to other AP’s • Prediction results • Saturation of 5GHz in 2015 may be 2 times worse than that of 2.4GHz in 2010unless there is no big enhancement of the Wi-Fi technology. • It may be too big a potential problem to simply neglect the need of new tech. Minho Cheong, ETRI

  12. Hot-Spot Measurements • In order to check the current severity of hot spot deployment in Korea, did some simple measurements in Seoul metropolitan area. • Train Station (Seoul KTX) much crowded with people • Underground Mall (COEX Seoul) crowded as well • Measurements are done with the use of “AirMagnet Wi-Fi Analyzer” • can gather all the Wi-Fi data within a wide area (200m x 200m) • can analyze all the statistics of Wi-Fi signals Minho Cheong, ETRI

  13. Hot-Spot Measurements (TrainStation, Seoul KTX) • Measurements are done on Christmas Eve, 2012 • The number of AP’s is 351 and the number of STA’s is 1101. Minho Cheong, ETRI

  14. Hot-Spot Measurements(TrainStation, Seoul KTX) • There are not so many private AP’s relatively. • Most of AP’s are good (and non-AP STA’s are new-fashioned, too) Minho Cheong, ETRI

  15. Hot-Spot Measurements(TrainStation, Seoul KTX) • Most of AP’s follow the 2.4GHz band recommendation. (Interference = co-channel + overlapped ch. + non-Wi-Fi) Minho Cheong, ETRI

  16. Hot-Spot Measurements (Underground Mall, COEX Seoul) • Measurements are done on Christmas Eve, 2012, too. • The number of AP’s is 277 and the number of STA’s is 917. Minho Cheong, ETRI

  17. Hot-Spot Measurements (Underground Mall, COEX Seoul) • There are so many private AP’s rather than operator-deployed. • Most of AP’s are good (while non-AP STA’s are old-fashioned) Minho Cheong, ETRI

  18. Hot-Spot Measurements (Underground Mall, COEX Seoul) • While most of operator-deployed AP’s follow the 2.4GHz band recommendation, it seems not to have big success due to relatively large number of private AP (most of them are legacy devices) Minho Cheong, ETRI

  19. Comparison between Two Scenarios • “Underground Mall” seems to experience severer retrials and more air-time occupancy with the basic rate due to relatively large number of legacy devices(11b). Number of non-AP STA’s across Wi-Fi generations Ratio of number of data packets and other packets Minho Cheong, ETRI

  20. Comparison between Two Scenarios • It can be seen that the more number of legacy devices or private AP’s (which are mainly not upgraded) make the severer throughput drop due to the quite more inefficient waste of air-time Minho Cheong, ETRI

  21. Conclusion & Next Steps • It is checked in the field that quasi-super-dense deployment scenarios can become quite worse if there are non-negligible number of private AP’s or legacy devices(11b). • More detailed analysis for 2.4GHz band (including the analysis of PER, average packet delay and real-time spectrum of Wi-Fi and non-Wi-Fi) may be additionally needed. • Measurements and analysis may be needed also for 5GHz band in the future. Minho Cheong, ETRI

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