[176803] in North American Network Operators' Group
Re: Comcast thinks it ok to install public wifi in your house
daemon@ATHENA.MIT.EDU (Livingood, Jason)
Thu Dec 11 17:12:04 2014
X-Original-To: nanog@nanog.org
From: "Livingood, Jason" <Jason_Livingood@cable.comcast.com>
To: Grant Ridder <shortdudey123@gmail.com>
Date: Thu, 11 Dec 2014 22:02:29 +0000
In-Reply-To: <CAPiURgXtzsLGLdwzeW1ze1qjVnpTDqASgKSTytUf6gd=h437cw@mail.gmail.com>
Cc: NANOG <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
On 12/11/14, 4:47 PM, "Grant Ridder" <shortdudey123@gmail.com<mailto:shortd=
udey123@gmail.com>> wrote:
I think it may have already been slightly mentioned, but any reason why thi=
s is not being rolled out on a separate radio than the private customer fac=
ing one? Even if the bandwidth out to the internet is separated with DOCSI=
S channels, you are still using the same radio and one user streaming a lar=
ge amount of data could bog down the radio. I have seen 1 or 2 clients des=
troy speed and cause large amounts (adding 100+ms) of latency for all clien=
ts connected to the same radio.
The latest device (called an XB3, see http://corporate.comcast.com/comcast-=
voices/the-technology-behind-the-industrys-fastest-wireless-gateway) does h=
ave multiple radios. I=92m not sure what the pros and cons are of dedicatin=
g individual radios to different SSIDs rather than letting some logic in th=
e WiFi chipset and radios determine that stuff more dynamically. That=92s p=
robably best asked of a WiFi chipset engineer at Cisco or Qualcomm.
Jason
From the URL above:
By Jill Formichella<http://corporate.comcast.com/comcast-voices?author=3D33=
7>, Director, Home Network Product Development, Comcast Cable in Internet<h=
ttp://corporate.comcast.com/comcast-voices?category=3Dinternet>
Comcast=92s new Xfinity Wireless Gateway, the DPC3941T, features the latest=
industry technology to provide superior performance and make it the fastes=
t on the market. The DCP3941T features cutting edge 802.11ac<http://en.wiki=
pedia.org/wiki/IEEE_802.11ac> Wi-Fi technology, a high power 3x3MIMO<http:/=
/en.wikipedia.org/wiki/MIMO> design with 3 spatial streams that can provide=
up to 1.3 Gbps of raw throughput, 80 MHz wide Wi-Fi channel support, and 2=
56-QAM modulation<http://en.wikipedia.org/wiki/Quadrature_amplitude_modulat=
ion>. All of this means that the Comcast Gateway can provide increased rang=
e and wireless throughput. Third party lab tests demonstrated more than 70=
0 Mbps of actual throughput, providing the fastest speeds for our customers=
and beating our competitors and many high-end retail products.
Antenna Design
After numerous design evaluations, the high power Wi-Fi antennas in the DPC=
3941T were positioned optimally to produce the most efficient gain patterns=
to offer the best performance. Fine-tuned calibration of EIRP<http://en.wi=
kipedia.org/wiki/Equivalent_isotropically_radiated_power> helps to provide =
better range and throughput compared to other Wireless Gateways.
Performance Tuning
Our gateways are tested at Allion Engineering Services<http://www.allion.co=
m/>, a 3rd party Wi-Fi certification facility, as well as in our partners=
=92 labs to constantly evaluate and improve the Gateway=92s performance. An=
echoic chamber<http://en.wikipedia.org/wiki/Anechoic_chamber> based tests p=
rovide good insight into the Gateway=92s maximum capabilities; controlled i=
nterference is injected on to Wi-Fi channels to evaluate gateway performanc=
e in congested and interference prone environments. Tests are also conducte=
d in various test houses to measure performance in a real-world environment=
. Test results include RSSI Heatmaps showing coverage of the Wi-Fi signal, =
average throughput across multiple locations and rate vs. range (chamber te=
sts). Finally the gateway is tested against our formalAcceptance Test Plan=
<http://en.wikipedia.org/wiki/Acceptance_testing>, which includes interoper=
ability testing with popular consumer electronics, and then our devices are=
tested with real Comcast customers to ensure excellent performance in a va=
riety of different conditions.
Close collaboration with Cisco & Qualcomm Atheros
Comcast collaborated closely with Cisco<http://www.cisco.com/> and Qualcomm=
Atheros<http://www.qualcomm.com/about/businesses/qca> from the early desig=
n stages to ensure the DPC3941T has the best Wi-Fi and antenna design and s=
olid performance. The DPC3941T is the first Comcast device to support an 80=
2.11ac high power amplifier solution boosting power by 3dB at the higher MC=
S rates<http://en.wikipedia.org/wiki/IEEE_802.11n-2009#Data_rates>. Also fe=
atured in the 3941T, which the previous Wireless Gateway 2 did not have, is=
a higher power Atom based CPU<http://en.wikipedia.org/wiki/Intel_Atom_(CPU=
)> from Intel and an additional 512MB RAM to help future proof the device.
