1. Wi-Fi Interference Measurement in Korea (Part I)
May 2013
doc.: IEEE /xxxxr0
May 2013
Wi-Fi Interference Measurement in Korea (Part I)
Date:
Authors:
Name
Affiliations
Address
Phone
Minho Cheong
ETRI
161 Gajeong-dong, Yuseong-Gu, Daejoen, Korea
Hyoung Jin Kwon
Jae Seung Lee
Sok-Kyu Lee
Minho Cheong (ETRI)
Osama Aboul-Magd (Huawei Technologies)

2. Month Year
doc.: IEEE yy/xxxxr0
May 2013
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)
John Doe, Some Company

3. Contents Introduction When will 5GHz band be saturated?
May 2013
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. May 2013
Introduction
Current Status of 2.4GHz/5GHz Unlicensed Band and Wireless Devices
IEEE b/g : 2.4GHz, IEEE a/ac : 5GHz, IEEE n : 2.4/5GHz
IEEE (Bluetooth): 2.4GHz
IEEE /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 2.4GHz band and 5GHz band
May 2013
Introduction
2.4GHz band and 5GHz band
GHz, GHz are now under consideration
In Korea, GHz cannot be used for Wi-Fi due to the Broadcast relay service
Band
20MHz
(19 Channels)
40MHz
(9 Channels
80MHz
(4 Channels)
160MHz
(1 Channels)
5.15~5.35GHz
(200MHz)
5.47~5.65GHz
(180MHz)
5.725~5.825GHz
(100MHz)
Broadcast
(75MHz)
Band
20MHz
(13 Channels)
2400~2483.5MHz
(83.5MHz) 1 2 3 4 5 6 7 8 9 10 11 12 13
Minho Cheong, ETRI

6. Introduction May 2013 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.
< Commercial Wi-Fi Deployment Korea>
Until
Until
Until KT
42,000
67,000
99,000
SKT
17,000
41,000
60,000
LGU+
160,000*
765,000*
1,282,000*
Total
219,000
873,000
1,441,000
* Wi-Fi in the fixed phone included
[Ref] : Jae-Hyun Kim, ‘Wi-Fi Workshop’ )
Minho Cheong, ETRI

7. May 2013
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?
May 2013
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 n, nowadays quickly transferring to ac) 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?
May 2013
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 )
Minho Cheong, ETRI

10. When will 5GHz be saturated without Wi-Fi technology enhancement?
May 2013
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 ac will overwhelm n
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?
May 2013
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 ac 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 ac, 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 2010 unless 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
May 2013
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 (Train Station, Seoul KTX)
May 2013
Hot-Spot Measurements (Train Station, 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 (Train Station, Seoul KTX)
May 2013
Hot-Spot Measurements (Train Station, 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 (Train Station, Seoul KTX)
May 2013
Hot-Spot Measurements (Train Station, 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)
May 2013
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)
May 2013
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)
May 2013
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
May 2013
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
May 2013
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
May 2013
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