Re: Comcast thinks it ok to install public wifi in your house

["Livingood, Jason" <Jason_Livingood () cable comcast com>]

On 12/11/14, 4:47 PM, "Grant Ridder" <shortdudey123 () gmail com<mailto:shortdudey123 () gmail com>> wrote:
I think it may have already been slightly mentioned, but any reason why this is not being rolled out on a separate 
radio than the private customer facing one?  Even if the bandwidth out to the internet is separated with DOCSIS 
channels, you are still using the same radio and one user streaming a large amount of data could bog down the radio.  I 
have seen 1 or 2 clients destroy speed and cause large amounts (adding 100+ms) of latency for all clients 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 have 
multiple radios. I’m not sure what the pros and cons are of dedicating individual radios to different SSIDs rather than 
letting some logic in the WiFi chipset and radios determine that stuff more dynamically. That’s probably 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=337>, Director, Home Network Product 
Development, Comcast Cable in Internet<http://corporate.comcast.com/comcast-voices?category=internet>

Comcast’s new Xfinity Wireless Gateway, the DPC3941T, features the latest industry technology to provide superior 
performance and make it the fastest on the market. The DCP3941T features cutting edge 
802.11ac<http://en.wikipedia.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 256-QAM 
modulation<http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation>. All of this means that the Comcast Gateway 
can provide increased range and wireless throughput.  Third party lab tests demonstrated more than 700 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 DPC3941T were positioned optimally to produce 
the most efficient gain patterns to offer the best performance. Fine-tuned calibration of 
EIRP<http://en.wikipedia.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.com/>, a 3rd party Wi-Fi certification 
facility, as well as in our partners’ labs to constantly evaluate and improve the Gateway’s performance. Anechoic 
chamber<http://en.wikipedia.org/wiki/Anechoic_chamber> based tests provide good insight into the Gateway’s maximum 
capabilities; controlled interference is injected on to Wi-Fi channels to evaluate gateway performance in congested and 
interference prone environments. Tests are also conducted 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 tests).  Finally the gateway is tested against our formalAcceptance Test 
Plan<http://en.wikipedia.org/wiki/Acceptance_testing>, which includes interoperability testing with popular consumer 
electronics, and then our devices are tested with real Comcast customers to ensure excellent performance in a variety 
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 design stages to ensure the DPC3941T has the best 
Wi-Fi and antenna design and solid performance. The DPC3941T is the first Comcast device to support an 802.11ac high 
power amplifier solution boosting power by 3dB at the higher MCS 
rates<http://en.wikipedia.org/wiki/IEEE_802.11n-2009#Data_rates>. Also featured 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.