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RF Shorts for June 28, 2013

Cable System Wi-FI ‘Hotspots’ Provide 4G Alternative
The ever growing demand for data from smartphone users is pushing the FCC to reallocate more and more spectrum for wireless carriers to use to meet that demand. What if there was another lower cost, same performance alternative in the areas where spectrum is most congested that didn’t require providing wireless carriers with more spectrum?

That alternative already exists in some areas and Steve Donohue describes it in his story Jefferies predicts cable MSOs will launch 'disruptive Wi-Fi/MVNO' products.

Regarding the Jefferies report, Donohue writes: “The widespread roll out of Wi-Fi hotspots from MSOs such as Comcast and Cablevision could help operators sell services to mobile device users who are charged data fees from wireless phone providers, Seitz said. He pointed to the 150,000 hotspots that have been built by the CableWi-Fi consortium, which includes Comcast, Time Warner Cable, Cox Communications, Bright House Networks and Cablevision. Seitz also noted the significance of Comcast's recent announcement that it will use wireless home gateways in subscriber homes to offer neighborhood hotspots run from a separate antenna, which could potentially allow it to offer millions of hotspots.”

Envelope Tracking Termed Key to Digital Transmitter Efficiency
Digital signals require linear amplifiers, and conventional linear amplifier technology is not that efficient. Doherty amplifiers significantly improve efficiency, but envelope tracking amplifiers offer even better efficiency. But there is a tradeoff—complications due to the need for the power being supplied to the amplifier to vary instantaneously with the peak power output.

Lou Frenzel provides a good overview of the state of envelope tracking technology in his article Envelope Tracking Now Essential to Achieve PA Linearity and Efficiency. He writes:

“What ET [envelope tracking] does is dynamically modulate the PA [power amplifier] DC power supply. The modulating signal is used to vary the PA supply voltage to keep it at a level that provides the best efficiency. This point is where the amplifier is at or near compression. Best efficiency occurs when the peak signal levels are near the DC supply level. The result is that the overall efficiency is increased from an average of 25 percent to over 60 percent. This has the overall effect of greatly decreasing the power dissipation and the attendant heat. An increase in battery life is another positive outcome.”

Thomson (now Comark) showed a TV amplifier with envelope tracking at the NAB Show two years ago. This technology has the potential to change the solid-state TV transmitter marketplace similar to the way in which the IOT replaced the klystron and the MSDC-IOT has largely replaced conventional IOTs in high-power TV transmitters.

Home Networks Vulnerable to Hack Attacks
Do you have a Zi-Wave wireless system controlling your home?

What about Internet connected home automation? reports on Hacking and attacking automated homes. The article says there will be several presentations at Black Hat USA 2013 and Def Con 21 about attacking the automated house, including automated homes using the Z-Wave wireless protocol.

The Z-Wave session synopsis reads, “Zigbee and Z-wave wireless communication protocols are the most common used RF technology in home automation systems...Z-wave is a proprietary wireless protocol that works in the Industrial, Scientific and Medical radio band (ISM). It transmits on the 868.42 MHz (Europe) and 908.42 MHz (U.S.) frequencies designed for low-bandwidth data communications in embedded devices such as security sensors, alarms and home automation control panels.... Z-wave chips have 128-bit AES crypto engines, which are used by access control systems, such as door locks, for authenticated packet encryption. An open source implementation of the Z-wave protocol stack, openzwave, is available but it does not support the encryption part as of yet. Our talk will show how the Z-Wave protocol can be subjected to attacks.”

The article describes several other sessions and offers a few basic tips for securing your automated home.

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