Jamming Cell Phones

Jamming cell phone signals is illegal in the United States but not illegal in other countries. As a result, people in the United States are finding and buying these devices on the Internet. The New York Times ran an interesting piece on November 2 titled Devices Enforce Silence of Cellphones, Illegally. The piece starts with the following:

One afternoon in early September, an architect boarded his commuter train and became a cellphone vigilante. He sat down next to a 20-something woman who he said was “blabbing away” into her phone.

“She was using the word ‘like’ all the time. She sounded like a Valley Girl,” said the architect, Andrew, who declined to give his last name because what he did next was illegal.

Andrew reached into his shirt pocket and pushed a button on a black device the size of a cigarette pack. It sent out a powerful radio signal that cut off the chatterer’s cellphone transmission — and any others in a 30-foot radius. “She kept talking into her phone for about 30 seconds before she realized there was no one listening on the other end,” he said.

I've written about wireless signal jamming in the past - specifically when I wrote about the New England Patriots video taping scandal that included rumors of wireless communications signal jamming. I have to admit, while watching the Colts/Patriots game yesterday and seeing Tom Brady struggle hearing plays using his helmet headset, jamming was on my mind. It got to the point plays were being relayed in the old fashioned way - was it crowd noise or could it have been signal jamming?

Let's take a basic look at the technology. Communications technicians and engineers are constantly aware of something called the signal-to-noise ratio, commonly abbreviated as SNR. The noise we are typically dealing with in unjammed situations is commonly referred to as Johnson or White Noise and it's always there. If systems are designed properly and when in range, communications signals are stronger than the noise and the noise is less significant because the SNR is high (think divide signal strength by noise strength). Basically, if a wanted communications signal is stronger than the noise then communications happens. If the noise is stronger than the communications signal then communications does not happen. We've all experience this in our cars while driving and listening to a radio station. As we get closer to a station signal source (antenna), the signal gets stronger and we hear the station clearer.

Now back to jammers - in simplest terms, jammers work by sending out strong signals that overpower the wanted communications signals between a cell phone and cellular antenna towers. Basically they generate the equivalent of noise at specific cell frequencies. Phones end up not communicating with the towers and users see a "No Service" type message on their phones.

A quick search of the Internet brings up a number of off-shore companies selling signal jammers. One of the more popular companies is London based PhoneJammer.com. PhoneJammer.com sells lots of different jamming devices ranging from a $149 portable jammer that runs on 9V batteries and has a range of 5m to a $3995 ultra high power phone jammer which is described as the most sophisticated digital cell phone jammer of its class, with tough die-cast aluminum casing and dual inter cooler, ideal for large hall type rooms or outdoor locations. It comes with a high gain base station type antenna.

The New York Times quotes PhoneJammer.com's site operator as follows:

"Victor McCormack, the site’s operator, says he ships roughly 400 jammers a month into the United States, up from 300 a year ago. Orders for holiday gifts, he said, have exceeded 2,000."

I'll write more about different kinds of wireless signal jamming this week. Remember - the devices are illegal in the United States.

Muni WiFi : One Year and a Minneapolis Bridge Tragedy Later

Minnie Ingersoll, Chris Sacca and Larry Alder from the Google Alternative Access Team have released some first year Mountain View, CA Google Wireless "data points" on the Official Google Blog. Here's some highlights:

- the network' has over 400 mesh routers that cover approximately 12 square miles - 95% of the mesh routers are used each day
- approximately 25,000 homes are served
- approximately 15,000 unique users are currently using the network each month
- since January 2007, network traffic has grown almost 10 percent each month
- the network is currently handling approx 300 gigabytes each day
- each day approximately 100 distict types of WiFi devices are accessing the network (I wonder how many are iPhones?:)

A Mountain View WiFi coverage map is linked here, Areas that do not have coverage typically do not have light poles to place the network equipment. If you happen to live in an area of Mountain View that currently does not have coverage you can contact Goggle about hosting a Google WiFi node on your property. Contact information is listed on the coverage map page.

Municipal WiFi networks were all the rage last year. Today a lot of the excitement has worn off - it's time to get some of this enthusiasm back. CNET News published an interesting but unfortunate piece on August 8 titled Citywide Wi-Fi network put to test in Minneapolis with reference to the I-35 bridge collapse tradegy on August 1. It just so happened USI Wireless had been deploying subscription based Wi-Fi in Minneapolis (one of my favorite cities) since April, with about 18 square miles of the city currently covered. Much of the initial installation was in the area of the I-35 bridge collapse. Here's a few quotes from the CNET piece:

"Within moments of the bridge's collapse, USI CEO Joe Caldwell said he was on the phone with James Farstad, a wireless consultant for Minneapolis involved in setting up the Wi-Fi network, to see what he could do to help".

"The first thing Caldwell did was open up the subscription-based Wi-Fi service so anyone could use it for free. Because the network had only been built around part of the disaster, Caldwell then ordered additional Wi-Fi radios to be placed in areas surrounding the catastrophe to blanket it with signals, providing an additional 12 megabits per second of capacity to the area around the bridge collapse.

Caldwell hoped that people with Wi-Fi-enabled smart phones would use the wireless network instead of their cell phones to make calls, thus alleviating the flooded cellular network. Cellular service in the area was overloaded within 30 minutes of the collapse, Farstad wrote in a blog he posted earlier this week".

"That evening, usage on the network jumped from 1,000 registered USI Wireless customers before the disaster struck to 6,000. Exactly how many of those 6,000 users were actually using the Wi-Fi network in lieu of the cell phone network isn't known. It's unlikely that many people were able to use the network for voice communications, given that most cell phones don't have Wi-Fi capability and those that do may not be able use voice over IP clients".

Here's more from CNET:

"... it provided a network for the community to City of Minneapolis resources, hospital emergency coordination units, State of Minnesota Department of Transportation traffic routing information, Red Cross Blood Bank collection points, and local and national news outlets".

"The USI Wireless team also quickly installed three Wi-Fi-enabled cameras that had been purchased by the city for a community policing effort, but hadn't been deployed yet. The cameras were set up along the river banks near the disaster site to provide a live video feed over the network directly to the command center".

"I'm not really sure what the relieve effort would have looked like if this network had not been in place," Caldwell said. "You can't really download these detailed maps easily using an EV-DO card. And you definitely couldn't have the kind of video streaming that is there down there now."

This story reminds me of my frustration with the saturated cellular networks as I was trying to contact friends and relatives in Manhattan after the Sept 11 World Trade Center attacks..... So many Muni WiFi projects have stalled in this country including the most publicized one in San Francisco. It's time to get these projects back on track..... Kudos to forward thinking municipalities like Mountain View and Minneapolis along with companies like Google and USI Wireless.