Comcast thinks it ok to install public wifi in your house

Livingood, Jason Jason_Livingood at
Thu Dec 11 22:02:29 UTC 2014

On 12/11/14, 4:47 PM, "Grant Ridder" <shortdudey123 at<mailto:shortdudey123 at>> 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 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.


>From the URL above:

By Jill Formichella<>, Director, Home Network Product Development, Comcast Cable in 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<> Wi-Fi technology, a high power 3x3MIMO<> 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<>. 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<> helps to provide better range and throughput compared to other Wireless Gateways.

Performance Tuning

Our gateways are tested at Allion Engineering Services<>, 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<> 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<>, 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<> and Qualcomm Atheros<> 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<>. Also featured in the 3941T, which the previous Wireless Gateway 2 did not have, is a higher power Atom based CPU<> from Intel and an additional 512MB RAM to help future proof the device.

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