• This presentation gives set of issues in channel modeling for dense Wi-Fi environments.
Sept. 2013
Slide 2 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Channel Modeling in HEW [4]
• Initial version of both indoor and outdoor channel model considered– Indoor channel models
• TGn (IEEE 802.11-03/940r4) and TGac (IEEE 802.11-09/0308r12) channel model documents provided SISO, MIMO and MU-MIMO channels models.
• Principle: take advantage of well-established TGn and TGac channel models
– Outdoor channel model• Three outdoor channel model proposals have been proposed in HEW (summary in
following slides)• Current principle: adopt outdoor channel model from other organizations instead
of developing outdoor channel model based on measurements from IEEE 802.11 working group.
• General structure seems good. • But, not fully reflects some specific environments for HEW
– e.g., super-dense environment
Sept. 2013
Slide 3 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Need of Supplements to Current Model
• High density of STAs – such as usage model 4a “Super-dense Urban Street - public access
and cellular offload”
Sept. 2013
Slide 4 Minho Cheong (ETRI)
Street Supporting in Word Cup 2002 PSY’s Performance Outdoor Man. United’s Street Parade
doc.: IEEE 11-13/1113r0
Submission
Need of Supplements to Current Model
• High density of STAs [5]– All the usage models (only except category 5) may be very dense
– With density of users up to 1.0 user/m2
Sept. 2013
Slide 5 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Need of Supplements to Current Model
• High density scenarios [6]
– 1a-Stadium: High density of users (0.5users/m²), inter-AP distance between 12 and
20 meters.
– 1b-Airport/trains: Each AP serves 120 users in a 200m2 area (0.6 users/m²). The
inter-AP distance is in the range of 15~20m. Single/multiple operators.
– 1c- Exhibition halls: Each AP serves 100 users in a 100m2 (1.0 user/ m²) area. The
inter-AP distance is in the range of 5~10m.
– 1d- Shopping malls: High density of users and high density of APs (undefined user/
m², but similar to “1c-Exhibition hall”)
– 1e-Education: Dense STAs (40~60 STAs) in one classroom with one AP. Class
room size is ~ 300 m² (0.2 user/ m²).
Sept. 2013
Slide 6 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Need of Supplements to Current Model
• High density scenarios [6]
– 2a-Wireless office: Typical distances between STAs and AP in the room are <
50m. 20-30 STAs per AP . Max. user/ m² =30/(3.14*50^2)= 0.04 user/ m²
– 3a-Dense apartment building: Building with 100 apartments. One AP in each
apartment of 10mx10m randomly positioned. 5 STA per AP randomly positioned
in the apartment. Max. user/ m² = 0.01 user/ m²
– 4a-Super-dense urban street: The inter-AP distance is in the range of 20-50m.
STA distribution density is about 0.5 user/ m2. In specific city squares, public
events gather even higher densities 1.0 user/m² and inter-AP distance is in the
range of 10-20m.
Sept. 2013
Slide 7 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Need of Supplements to Current Model
• There need additional considerations to reflect high density of STAs in the HEW – which the HEW SG has regarded as very important starting point
• such as – (1) Additional path-loss due to human body blockage
– (2) Adjustment of indoor scattering parameters
– (3) Adjustment of indoor LOS/NLOS breakpoints
• because – many people very close near by induce quite more ray-scatterings
and non-negligibly frequent blockage by human bodies
Sept. 2013
Slide 8 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• In super-dense scenarios, in addition to general indoor (from 802.11n/ac channel model) or outdoor (from WINNER or ITU model), we need to consider the following environments as well
Sept. 2013
Slide 9 Minho Cheong (ETRI)
AP
My STA(smart phone)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• Blockage effect due to head-to-hand (purple in slide 9)– Whenever a person watches his smart-phone in super-dense
environments, his own head is likely to block the link to AP many times, which has been a problem even in nowadays
• Blockage effect due to other people (red in slide 9)– 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 additional path loss
Sept. 2013
Slide 10 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• Human body blockage modeled in other standards– IEEE 802.11ad channel modeling using 60GHz band [7]
Sept. 2013
Slide 11 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• Human body blockage modeled in other standards– IEEE 802.11ad channel modeling using 60GHz band [7]
• Because 60GHz band ray have quite a directivity– There is lots of power gap between main path and remaining paths
– Penetration loss due to human body is only about 20dB
Sept. 2013
Slide 12 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• Human body blockage modeled in other standards– IEEE 802.15.6 (Body Area Network) channel modeling [8]
• Using 13.5MHz band, 5-50MHz band
• Using 400MHz band, 600MHz band, 900MHz band
• Using 2.4GHz band
• Using 3.1-10.6GHz band
Sept. 2013
Slide 13 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• Human body blockage modeled in other standards– IEEE 802.15.6 (Body Area Network) channel modeling [8]
– e.g.) Type C model at 2.36GHz
Sept. 2013
Slide 14 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• Human body blockage modeled in other standards– IEEE 802.15.6 (Body Area Network) channel modeling [8]
– e.g.) Type C.1 model at 3.1-5.1GHz
Sept. 2013
Slide 15 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• Human body blockage modeled in other standards– IEEE 802.11ad channel modeling using 60GHz band [7]
• Because 2.4GHz & 3.1-5.1 GHz band ray have less directivity (maybe very similar to WLAN band)– There isn’t much power gap between 1st path and remaining paths
– Penetration loss due to human body is over 60dB
Sept. 2013
Slide 16 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• Lessons from observation of other channel models– Because IEEE802.15.6 results must be very similar to Wi-Fi bands
– We can regard any Wi-Fi ray touched by human body as almost disappeared in super-dense scenario
• So, whenever there comes disappearance of major paths (main path or other non-negligible paths) due to human body blockage, it will definitely increase a lot its path loss overall
Sept. 2013
Slide 17 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Additional Path-loss due to Human Body Blockage
• Possible Supplements– Path loss = Path loss (current model) + delta– Add an additive (delta) due to human blockage to the current indoor
& outdoor channel model specifically in super-dense environments
• Work to do in the future– Need to measure & investigate the statistics of increased path loss
due to human body blockage in Wi-Fi super-dense environments• According to indoor or outdoor• According to density of STAs • According to location of AP (3 dimensional)
• based on the cluster model developed by Saleh and Valenzuela [10], and further elaborated upon by Spencer et al. [11], Cramer et al. [12], and Poon and Ho [13].
– IEEE802.11ac channel models (SU/MU-MIMO) [14] additionally applied AoD/AoA randomization and BW widening based on 802.11n channel
• Cluster model assumes – Some limited number of clusters in it
– With angular spread statistics
– With delay spread statistics
Sept. 2013
Slide 19 Minho Cheong (ETRI)
-50 0 50 100 150 200 250 300 350 4000
5
10
15
20
25
30
Delay in Nanoseconds
Rel
ativ
e dB
doc.: IEEE 11-13/1113r0
Submission
Adjustment of Indoor Scattering Parameters
Sept. 2013
Slide 20 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Adjustment of Indoor Scattering Parameters
Sept. 2013
Slide 21 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Adjustment of Indoor Scattering Parameters
• There may be need to modify the cluster parameters for newly-introduced super-dense environments – Because number of clusters increased (Model B/C/D may not fit)
– Linear regression analysis between “mean delay spread” and “mean angular spread” may not exactly fit for super-dense scenarios
Sept. 2013
Slide 22 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Adjustment of Indoor Scattering Parameters
• Possible Supplements– Need to check whether relation in the current modeling equation
between “mean angular spread” and “mean delay spread” can be still applicable to super-dense environments
– Need to newly measure delay spread and angular spread statistically in super-dense environments
– But, it may require huge work to do…
Sept. 2013
Slide 23 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Adjustment of Indoor LOS/NLOS Breakpoints
• IEEE802.11n/802.11ac channel model assumed– Within some distance (breakpoint): regarded as LOS channel
– Over some distance (breakpoint): regarded as NLOS channel
Sept. 2013
Slide 24 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Adjustment of Indoor LOS/NLOS Breakpoints
• Breakpoints needs to be quite smaller in super-dense– Because HEW SG assumes that super-dense scenario may have density
of STAs of 0.5 users/m2 or 1.0 users/m2 or more– Current breakpoint values (5m, 10m, 20m and 30m) seems too large
when we consider high density STAs indoor scenarios
• Possible Supplements– Add one more option of “LOS/NLOS breakpoint”
• dBP smaller than 5m for super-dense environments
– (if possible) add one more option of “shadow fading std. dev. after dBP ”
• larger than 6dB for super-dense environments
Sept. 2013
Slide 25 Minho Cheong (ETRI)
doc.: IEEE 11-13/1113r0
Submission
Suggestion
• Additional path-loss due to human body blockage – Add an additive path loss to the current path loss model
• for indoor and outdoor channel model as well
• See slide 18
• Adjustment of indoor scattering parameters– Need to investigate, but it requires huge work to do…
• for indoor channel model only
• See slide 23
• Adjustment of indoor LOS/NLOS breakpoints– Add one more mode for super-dense environments
[11] A.A.M. Saleh and R.A. Valenzuela, “A statistical model for indoor multipath propagation,” IEEE J. Select. Areas Commun., vol. 5, 1987, pp. 128-137.
[12] Q.H. Spencer, et al., “Modeling the statistical time and angle of arrival characteristics of an indoor environment,” IEEE J. Select. Areas Commun., vol. 18, no. 3, March 2000, pp. 347-360.
[13] R.J-M. Cramer, R.A. Scholtz, and M.Z. Win, “Evaluation of an ultra-wide-band propagation channel,” IEEE Trans. Antennas Propagat., vol. 50, no.5, May 2002, pp. 561-570.
[14] A.S.Y. Poon and M. Ho, “Indoor multiple-antenna channel characterization from 2 to 8 GHz,” submitted to ICC 2003 Conference.
