1. Considerations on HEW Evaluation Methodology
May 2013
doc.: IEEE /xxxxr0
July 2013
Considerations on HEW Evaluation Methodology
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 tries to list up additional considerations on design of HEW evaluation methodology.
Minho Cheong (ETRI)
John Doe, Some Company

3. July 2013
PHY Impairments
PHY impairments defined in ac Evaluation Methodology
PA nonlinearity
Carrier frequency offset
For single user communications
For Downlink MU-MIMO transmission
For Uplink MU-MIMO transmission
Phase noise
Noise figure
Antenna configuration (mix of vertically or horizontally polarized)
Fluorescent light effect
Timing offset for Uplink MU-MIMO transmission, [ ]ns with respect to reference
Power difference needs to be considered due to non-ideal ranging
For UL MU-MIMO transmission, [-TBD TBD] dB with respect to avg. power
Minho Cheong (ETRI)

4. Network-Level Impairments
July 2013
Network-Level Impairments
In terms of topology and deployment of multiple BSS’s
It may be desirable to newly introduce network-level impairments as well in addition to PHY impairments, which have a significant influence on the network performance
Different from evaluation methodology till ac, HEW really wants to consider network-level evaluation taking multiple neighboring BSS’s scenario into account
Such as
Non-ideal deployment of AP and STA
Hidden AP’s each other
Non-ideal network sync. among multiple neighboring AP’s
Minho Cheong (ETRI)

5. Network-Level Impairments (2)
July 2013
Network-Level Impairments (2)
How much is location of AP’s distorted from a originally expected location based on a fixed organized pattern design?
One of key characteristics of Wi-Fi network is that it does not have a fixed pattern topology (such as hexagonal deployment) in real world, which is very specific feature of Wi-Fi compared to cellular network
Location of STAs
It seems OK to set in a purely random modeling over a area
Location of AP
Deviation from an expected location seems quite a more adequate design rather than just purely random positioning over an area, because every AP is likely to be deployed having some distance with others though it is not a well-organized design
Example
3-D random deviation within [-V, V] + (X, Y, Z), where (X, Y, Z) is an originally expected location of AP based on design of hexagonal fixed pattern topology
Minho Cheong (ETRI)

6. Network-Level Impairments (3)
July 2013
Network-Level Impairments (3)
How much portion of private AP’s or old-fashioned STA’s are existing in the simulation scenario?
Private AP’s or old-fashioned STA’s are one of key reasons for big degradation on network performance
We need to take into account several generations of Wi-Fi devices coexisting when try statistical modeling of multiple AP’s and STA’s in the simulation scenario
Example
X % of AP’s are private AP’s, which cannot be coordinated with other neighboring AP’s
Y % of STA’s are old-fashioned STA’s
[Y1 Y2 Y3 Y4] % for 11b/11g/11n/HEW STA’s in 2.4GHz
Minho Cheong (ETRI)

7. Network-Level Impairments (4)
July 2013
Network-Level Impairments (4)
Timing offset among neighboring AP’s due to non-ideal network synchronization
Irrespective of what level of AP-to-AP coordination we will really introduce, it may not be a bad idea to introduce non-ideal timing alignment offset among neighboring AP’s which may have a big impact on the performance of some coordination schemes
Example
When network synchronization is not applied
Do not consider a specific range for timing offsets
When network synchronization is applied
Timing offset per each AP lies within [-t t] (ns) with respect to reference
Minho Cheong (ETRI)

8. Simulation Scenarios Frequency allocation of neighboring BSS’s
July 2013
Simulation Scenarios
Frequency allocation of neighboring BSS’s
We need to consider cases in which neighboring BSS’s have different frequency channels
Also need to consider cases in which primary channels are not aligned with each other among neighboring BSS’s while supporting the same frequency resources in total
In addition, we need to consider cases in which frequency channels of neighboring BSS’s are partially overlapped
It is already introduced one in ac evaluation methodology reflecting the real world problem very common even now
Minho Cheong (ETRI)

9. Simulation Scenarios (2)
July 2013
Simulation Scenarios (2)
Hidden AP’s each other while some of belonging STAs collide
In most of HEW usage models, many BSS’s are likely to be much populated within a limited area
So, there may be so many cases in which neighboring AP’s are hidden each other while those belonging STAs collide. So, we also need to take into account in the simulation scenarios.
Minho Cheong (ETRI)

10. Channel Model Blockage effect in a dense scenario
July 2013
Channel Model
Blockage effect in a dense scenario
In addition to general indoor (from n/ac channel model) or outdoor (from WINNER or ITU channel model), we need to consider the following environments as well
Head-to-hand blockage effect
Whenever a person watches his smart-phone, his own head is likely to block the link to AP many times, which has been a problem even in nowadays
Other human body blockage effect
In most of HEW usage models, many people are very crowded within a limited area with super high density more than 0.5 person/m2 or 1.0 person/m2.
In these environments, we can hardly expect an LOS link between AP and STA due to blockage effect from other human bodies, which seems to require new channel modeling to solve this HEW-dedicated problem.
Minho Cheong (ETRI)

11. July 2013
Channel Model (2)
Different antenna direction depending on usage models
In usual Wi-Fi hot-spot use scenario, physical direction of antennas equipped in the laptops or smart-phones may be purely random
But, in some important scenarios of HEW usage models,
such as super-dense urban usage model or exhibition hall in which most of people are very actively generating UGC and uploading/downloading
Most of hand-held devices involved are likely to have a specific physical direction to the event in common.
So, we also need to consider this characteristics of antenna direction effect depending on each specific usage model
Because this also have a significant impact on network performance
Minho Cheong (ETRI)

12. References [1] 11-09-0161-02-00ac-802-11ac-usage-model-document
March 2012
doc.: IEEE /0330r0
July 2013
References
[1] ac ac-usage-model-document
[2] ac-tgac-functional-requirements-and-evaluation-methodology
[3] hew-Usage-models-for-HEW [4] hew-hew-sg-usage-models-and-requirements-liaison-with-wfa
[5] hew-usage-scenarios-and-applications
[6] n-usage-models
[7] hew-HEW-functional-requirements-follow-up
Minho Cheong (ETRI)
Wookbong Lee, LG Electronics