March 2011
doc.: IEEE 802.11-11/0323r0
Views on 802.11ah Use Cases
Date: 2011-03-14
Authors:
Submission
Name
Affiliations
Address
Phone
email
Ron Porat
Broadcom
16340 West Bernardo Dr., San
Diego, CA 92127
858-521-5409
[email protected]
Vinko Erceg
Broadcom
16340 West Bernardo Dr., San
Diego, CA 92127
Matthew Fischer
Broadcom
Slide 1
Ron Porat, Broadcom
March 2011
doc.: IEEE 802.11-11/0323r0
Background
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802.11ah goal is to standardize a new amendment for unlicensed S1G
frequencies [1].
However, since those frequencies are unlicensed, there are currently
802.11b/g products that are sold in the 900MHz band (by re-banding) to
provide improved outdoor WiFi (for example see [2]). The reason being is
that lower frequencies provide improved propagation characteristics.
Note that typically S1G frequencies have been used for long range
outdoor systems such as broadcast terrestrial TV, cellular and military
systems.
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The value of this spectrum is high - recently Verizon Wireless paid ~$10B for 20MHz of
spectrum in the 700MHz band to deploy LTE
It is unlikely that more unlicensed S1G spectrum will be allocated in the
future since this spectrum is considered ‘beach front property’ coveted by
many entities such as broadcasters and cellular carriers
Hence, we should support applications that benefit most from S1G
frequencies which are given to us for free
Submission
Slide 2
Ron Porat, Broadcom
March 2011
doc.: IEEE 802.11-11/0323r0
802.11ah Applications
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Currently, a large range of applications are proposed for 802.11ah and
are summarized in [3].
They can be classified into several categories in several ways. For
example:
– Indoor and Outdoor extensions of 802.11
• To be used for any application used today by WiFi users as an added option for extended
range (albeit at lower maximum rates) and preferably in conjunction with 802.11n and/or
802.11ac to allow for efficient usage of S1G spectrum when necessary
• The required bit rate is only limited by user demand
• A typical range may be few tens and up to few hundreds meters in NLOS conditions
– Indoor and Outdoor extensions for 802.11 for M2M applications
• Rates can be high for Video applications such as surveillance
• Rates can be extremely low for other applications such as healthcare, home and industrial
automation and control, menu and coupon distribution , transportation control
– Can be easily accommodated by using <500KHz channels
• A typical range may be few tens and up to few hundreds meters in NLOS conditions
• In general M2M rates are somewhat more predictable
Submission
Slide 3
Ron Porat, Broadcom
March 2011
doc.: IEEE 802.11-11/0323r0
Cont.
– Outdoor smart grid
• Rates per client are extremely low (can also be accommodated by using <500KHz
channels) but the required range is highest among the proposed applications.
• The number of STA per AP is also highest (several thousands) among other scenarios
•
To summarize, a mix of very low rate and medium rate applications in
LAN and WAN scenarios (all four options)
Submission
Slide 4
Ron Porat, Broadcom
March 2011
doc.: IEEE 802.11-11/0323r0
Similarities With TVWS
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S1G frequencies under consideration are similar to TVWS frequencies
and we can expect the same applications to benefit from both TGah and
Tgaf amendments.
In particular we refer to [4] for a good description of TVWS use cases and
briefly state them below. It is clearly seen that they are quite similar to
what has been proposed for TGah
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Submission
Extended Coverage Wi-Fi
Bridge among Small Networks
In home media distribution
WISP/WAN
Cellular Offloading
Wi-Fi Direct
M2M
Smart Grid
Slide 5
Ron Porat, Broadcom
March 2011
doc.: IEEE 802.11-11/0323r0
Views
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Scenarios - 802.11ah benefits range extension scenarios when compared to current
802.11. As such, use cases 1a-1d, 2,3,4a,5 from [3] are more inline with TGah PAR
with the following comments:
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Mobility – some outdoor use case can benefit from mobility support. The system should be
optimized for up to pedestrian speeds. Support for higher speeds is FFS.
Medium rates use cases are supported provided they meet the system capability based on its
BW and MIMO configuration (number of concurrent HDTV transmissions may be very limited
and usage of SDTV instead of HDTV may be preferred).
System BW – in order to have a manageable number of modes we propose bandwidths of
2.5/5/10MHz. Narrower bandwidths are FFS
Dynamic usage of frequencies – many of the scenarios proposed can benefit from
the new 900MHz but can also be deployed at 5GHz at least to some extent. For
example video streaming can use 5GHz for shorter distance and 900MHz for far
away clients – to the extent possible we support efficient and dynamic usage of all
available frequencies.
Submission
Slide 6
Ron Porat, Broadcom
March 2011
doc.: IEEE 802.11-11/0323r0
Cont.
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Interference between low BW applications and high BW applications - many
schemes can be explored i.e. per country channel maps whereby for example in the
case of the US the lowest X (e.g. 5) MHz of the available 26MHz spectrum can be
reserved to low BW applications.
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Indoor applications - some indoor applications can benefit from the improved
propagation at 900MHz but low bit rate applications (e.g. 1e-1h) can definitely also
work at higher frequencies as the plot in the Appendix shows and using current
802.11b/g/n/ac.
Submission
Slide 7
Ron Porat, Broadcom
March 2011
doc.: IEEE 802.11-11/0323r0
References
[1] 11-10-0001-13-0wng-900mhz-par-and-5c.doc
[2] http://www.caworldwifi.com/900-Mhz-WiFi.html
[3] 11-11-0301-00-00ah-categories-of-use-cases-and-straw-polls.pptx
[4] TVWS MTG Use Cases Draft v0.03_clean.doc
Submission
Slide 8
Ron Porat, Broadcom
March 2011
doc.: IEEE 802.11-11/0323r0
Appendix
Submission
Slide 9
Ron Porat, Broadcom
March 2011
doc.: IEEE 802.11-11/0323r0
Indoor Link Budget
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The following plot shows the SNR for a low power indoor system at 5.5Ghz
Assumptions:
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11n path loss formula
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10m breaking point, 5db shadowing std
Path loss includes one shadowing std
NF=5dB
Transmit power 0dBm
Transmission BW – 100KHz
Indoor SNR
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SNR [dB]
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Submission
15
Slide 10
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25
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Tx-Rx distance [meters]
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Ron Porat, Broadcom