Tag Archives: cellular

How mobile phones reveal your location

Obviously, when your phone’s GPS receiver is on, your location within 30 feet or so is usually available.

Cellular antenna system on monopole
photo Steve Kazella

There’s another way that remotes, your cellular service provider, 9-1-1 call centers [also known as Public Safety Answering Points (PSAPs)], and law enforcement can determine your phone’s location, even when your GPS is off, or even if your plain-Jane flip-phone has no GPS receiver. It’s called Uplink-Time Difference of Arrival U-TDOA). Here’s a brief simplified video description. Each cell tower has an antenna array with three or four 90 or 120 degree (when viewed from above) antenna sectors. Each tower knows, by comparing your phone’s received signal strength in each sector, which sector your phone is in. By measuring the propagation time for a “ping” to travel between the tower, your phone, and back again, it also knows the range to your phone. In a populated area your phone is likely to be talking with more than one tower, so all that’s needed is to know the bearing and range to your phone relative to two or more towers, and your location can be estimated within maybe a 100 foot radius. (You will be at the intersection of the two or more arcs.)

Even with only one tower talking to your phone, it knows that you are located somewhere along that 90 or 120 degree arc within the sector with the strongest signal. U-TDOA is used in Enhanced 9-1-1 Phase II systems so that first responders may be dispatched to wherever your cell phone is located when you place a 911 call for emergency assistance.

The only way to stop this is to remove the battery from your phone. (Oops. Sorry, iPhone users.) Switching it off won’t stop the communication. Switching it to Airplane Mode will prolly stop it, but there are no guarantees.

Update Here’s a clear explanation of mobile phone positioning techniques.

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© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

CTIA’s stolen cellphone blacklist

A stolen smartphone can fetch $200 to $300, so smartphone theft remains a problem. CTIA’s website includes tips on how to deter smartphone thefts.

CTIA logoThe CTIA (Cellular Telecommunications Industry Association) announced in November that it had integrated its stolen cellphone database with similar international databases. A recent Verge article describes the importance of the overseas stolen cellphone market and the controversy that surrounds a built-in “kill switch” for smartphones.

The CTIA insists that its new improved cellphone blacklist will make “kill switches” unnecessary. We’ll see what happens to the market value of stolen phones.

Where are T-Mobile’s cell sites?

T-Mobile’s GSM signal inside my house is marginal. My Android phone indicates field strengths from about -100 dBm to -113 dBm. (I *think* that GSM needs a minimum field strength of about -109 dBm.) I have a vague idea where T-Mobile’s nearest cell site is located, but I’m having difficulty pinpointing it.

I’ve found conflicting information from these sources:

Transmitting_tower_top_usLast week I stopped at the nearby T-Mobile store. To my surprise, none of their salespeople knew where the nearest T-Mobile cell site is located . . . nor were they interested. One guy has worked there since 1998, and never thought to learn the nearest cell site location. I’m amazed.

I spoke with a T-Mobile tech support person on the phone, who volunteered an approximate cell site location within a mile of my house. I walked in that residential neighborhood, and my phone indicated a signal strength of about -71 dBm — which would indicate that I was getting warm — but I was unable to visually identify a cellular antenna. There’s no tower, but there is a church nearby, and I’ve read that T-Mobile likes to place cell sites within church steeples. My guess is that this cell site is just a repeater, with no fiber backhaul.

If that’s the nearest cell site to my house, the signal’s path loss to my house is about 30 to 40 dB. That seems reasonable, as I *think* that T-Mobile operates in the 1700 and 1900 MHz bands and there are lots of mature trees in the path to my house.

Can you recommend a method of determining exactly where the nearest T-Mobile cell site to my house is located? Please?

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

I killed my Smartphone’s battery

I’ve had my Samsung SGH-T679 Insight II phone for about 13 months. It’s small, as is its battery. Battery runtime has never been great, but recently it’s been terrible. Last week, the phone turned itself off several times, and it refused to recharge today.

An expanded worn-out Lithium-ion battery and new one (upper-left)
An expanded worn-out Lithium-ion battery and new one (upper-left)

Jenson at the T-Mobile store tested my charger and pronounced it healthy. Kristen at the Batteries Plus store took one look at the battery, whose sides were slightly bulging, and pronounced it dead. She told me that a quick test is to place the battery on its flat side on a tabletop and spin it. If it spins easily, it’s bulging. Bulging sides = Dead battery.

I confess that I’ve left my phone on the charger for hours overnight, long after the battery was fully charged. I’ve also recharged it whenever it fell below 80 percent charge. Kristen explained that although the phone is supposed to have current limiting circuitry, it isn’t perfect. It’s much better to unplug the charger once the battery is fully charged, and to allow the battery to discharge to 20 percent or so before recharging it. I’ll follow her recommendations with my new battery.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

Power to the peoples’ cell phones

The Power Matters Alliance (PMA) is a group of companies and government and academic bodies that wish to promote the concept of wireless power delivery to mobile devices. Power Matters Alliance markThe smartphone is a 21st century invention, but the dream of wireless power transmission is at least a century old. My articles Wireless hype existed a hundred years ago, also and Wardenclyffe site to be acquired for proposed Tesla museum touched on this ancient dream. Tesla and Marconi dreamed of long-distance wireless power transmission. The PMA’s goals are more modest: they want you to place your phone on a hot-plate at Starbuck’s, where it will receive power through the miracle of inductive coupling. (Discovered by Michael Faraday and Joseph Henry c 1831, electromagnetic induction is the principle behind transformers and motors.)

As part of the IEEE Standards Association (IEEE-SA) Industry Connections program, the PMA is fleshing out a suite of standards that provide advanced wireless power – called ‘Power 2.0’

It sounds good, but there’s one pesky law of physics that interferes: The efficiency of inductive coupling is inversely proportional to the distance between the two coils.

Meanwhile, in the world of wired battery chargers . . .
In 2009, all GSM phone manufacturers except Apple agreed on a standard low-voltage DC charger-to-phone interface specification (GSM phones will have a standard battery charger), which was a big step forward.

The PMA has lofty goals:

It is estimated that by 2020 wireless charging could offset the equivalent of 289.4 million metric tons of CO2 and the equivalent of 482 100MW power plants. These savings could amount to a cancellation of the entire embedded energy usage of external power supplies by over 118%, thereby saving the unnecessary disposal of an estimated 4.5 billion transformers and associated toxic components into landfills.

It’s going to be tough to achieve good efficiency. I wish them luck.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

Manage your Android phone’s battery.

I like the well-done GSam battery monitor app for my Android (Gingerbread) phone. It tells me how much current each process is consuming, and estimates remaining charge time and talk times, as well as battery charge state and temperature and RF signal strength as a function of time. My Samsung SGH-T679 has a small battery, whose charge is quickly depleted when streaming audio and especially video, so this gauge is essential for my phone. It’s just what the doctor ordered. I found it in my phone’s Android Play Store. It was free of charge.

You can see that the screen gobbles most of my battery’s current, so I try to turn the screen off whenever possible.

GSam battery monitor screens
GSam battery monitor for Android Screenshots.
The leftmost screen is running on battery.
The center screen is running on charger.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

Tom Wheeler as FCC Chairman?

President Obama has nominated Tom Wheeler, another in a long line of political hacks at the FCC, for the FCC chair. This choice receives mixed reviews from observers: Obama’s new FCC chairman isn’t a reflexive shill for carriers, but he’s still a bad pick. Tom WheelerHis close ties to the cable TV and mobile phone industries worry me. Wheeler is former head of the National Cable and Telecommunications Association and the mobile wireless trade group CTIA (Cellular Telecommunications Industry Association). Translation: he lobbied for these industries. He’s also a major Obama campaign fund raiser. (His predecessor, Julius Genachowski, was an Obama election campaign committee official.) Nothing new here — it merely continues a long tradition of patronage at the FCC.

Remember Obama’s “no lobbyists in my administration” pledge?

In my opinion, Mr. Wheeler is way too closely connected to industries that fall under the FCC’s oversight. You can bet that his cable TV and cellular provider buddies hope that Congress approves his nomination as FCC Chairman. It’s ironic that the two segments of the American electronic communications market that are infamous for gouging the consumer are the industries for which he’s been a champion. If he runs the FCC, don’t expect change in either of these cozy shared marketplaces. Both industries are fat and happy, with limited competition. In fact, expect legislation to prevent municipalities and Google Fiber et al from competing with the incumbents.

Now, more than ever, the FCC Chairman should be independent of industry associations. Tim Wu, respected telecommunications observer, writing in The New Yorker, described The Coming War Over Net Neutrality. uncoveror comments,

The FCC, by getting in bed with the industries it is supposed to regulate, has undermined its very reason to exist. They are a corrupt agency for sale to the highest bidder.

I hope that Wheeler’s appointment is bounced by Congress and Mr. Obama instead nominates Susan Crawford, who doesn’t seem to be in any industry’s pocket. I almost forgot: she didn’t raise election funds for Mr. Obama. Hey, I can dream, can’t I?

Video clip: former FCC board member Nicholas Johnson calls Wheeler’s nomination “somewhere between bizarre and outrageous”.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

Breakup of AT&T, 30 years later

ListenC-Span recorded a fascinating 30-minute discussion about the breakup of AT&T thirty years ago and its impact on today’s telecommunications industry. Podcast-icon-200wThe gist is that on the whole, the breakup was beneficial. They do express misgivings about the lack of technical leadership within the entity that now calls itself AT&T. I share their concern; when AT&T lost Bell Labs and Western Electric, they lost their technical chops. What was left was a bunch of sales people, union workers, MBAs, and lawyers. The Bell operating companies were appliance operators with little in-house technical expertise.

Whence technical leadership?

One participant points out that two key breakthroughs were invented at AT&T’s Bell Labs:

  1. the transistor (1947)
  2. cellular telephone (1970s)

(I’d add that Claude Shannon’s groundbreaking 1948 article titled A Mathematical Theory of Communication (PDF) in Bell System Technical Journal 27 (3): 379–423 was a huge step forward.)

Today’s AT&T (which is a holding company created when Southwestern Bell renamed itself “AT&T”) does nothing like that sort of fundamental research.

They also correctly point out that the migration from wired to wireless telecommunications puts pressure on a limited resource — radio frequency spectrum. They seem to think that if the FCC opens more spectrum for telecom use, everything will be fine. I’m less sanguine. (See Claude Shannon’s Information Theory, published in 1948.) It’s hard to bend the laws of physics, despite sales hyperbole and cheering MBAs.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

These are not the droids you are looking for.

Android is an impressive operating system, but it’s far from perfect.

Android employs pre-emptive multi-tasking: the operating system retains control of the CPU even after starting a new process. It will, without warning, shut down background applications to free up memory. (Most modern operating systems on computers with disk drives, as they run low on memory, will swap least-recently-used memory contents to disk. This is called virtual memory. My Android phone has no disk, so there is no virtual memory.)

Block Diagram of Android's functions
diagram: Alvaro Fuentes Vasquez (Kronox)

Unfortunately, when it needs memory, Android will shut down background apps without warning. Sometimes it shuts down Tunein, and that app doesn’t allow streams to resume from the interruption point. Trying to resume the audio stream can waste tens of minutes.

High-Level programming provides fast app development but poor control

Android provides high-level system calls to its apps, and the apps are written in high-level languages. The result is that for real-time functions such as streaming media, the user has very little idea of program progress or user control. At least half the time that I try to stream media, my attempt fails a few minutes later, with no real indication of why it failed.

This reminds me of the MS-DOS days: MS-DOS and PC-DOS provided system calls for communication. They were limited and slow, so communication application programmers simply ignored the MS-DOS system calls and instead used low-level routines to talk directly to the underlying hardware. They could do this without breaking the system, because MS-DOS was a single-user, single-tasking operating system. It broke some portability between hardware platforms. The world of Android is much more complex: the phone’s stability requires that each Android app behaves itself by communicating via Android system calls only. (It’s easy to forget that this thing is, after all, a phone.)

I don’t know where this is headed. Clearly Android needs work on its user interface. It probably ought to ask permission before shutting down a background app. It should provide low-level system calls, and the app writers need to use those system calls to improve the interface for the poor Android user.

This article is based upon my experience with my Samsung SGH-T679 Insight II 4G (aka Galaxy Exhibit 4G) T-Mobile phone. It uses Android 2.3.6, which I guess is named Gingerbread.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

My Android phone has become an audio library.

Podcast icon 200w

icon: Yagraph
For me, having podcasts in my pocket is the smartphone’s killer app.

I’ve mentioned that I like to listen to audio as I program computers. (One exception: when I must concentrate on a stubborn problem, I need silence.) With my new Android phone, I can listen as I take walks, as well. At the moment, I’m listening to a 15-minute long biographical sketch of mathematician Joseph Fourier.

This podcast is part of BBC’s A Brief History of Mathematics. I found this series within the History section of the free BBC Podcasts app that I downloaded from the Google Play Store. The BBC Podcasts app is loaded with podcasts, neatly arranged by category. So far, I’ve stuck with the factual, scientific, and historical ones. It’s a goldmine that costs nothing.

I’ve also been listening to the technology podcasts that are available within the Tunein app. These include Michio Kaku’s Explorations in Science, The Wall Street Journal’s Technology Marketplace Report, etc. You can download the Tunein app from the Google Play Store, as well.

I’m overjoyed to have stumbled upon these podcast apps, because (as you may have guessed) the program content that I like to listen to isn’t standard broadcast fare. For me, the promise of “content on demand” has been fulfilled. I’m grateful to these podcasters for making this material available.

If you have an iPhone, I’d guess that the same apps are available from the iTunes store.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

Streaming NPR to my Android phone

Here’s a great use for my new Android smartphone.

prairiehome.publicradio.org website
Gary Keillor and cast of A Prairie Home Companion radio show performing in Lanesboro, Minnesota. June, 2007
photo: Jonathunder

Finally, my new Android phone is paying for itself. I followed the suggestion that Sue made in a comment and loaded some apps on my new Android phone. One of my faves is the Tunein app. I’m now listening to one of my favorite weekly radio programs, A Prairie Home Companion, broadcast on NPR (National Public Radio) stations. I love its freewheeling live radio show feel, its music, the humorous skits, and the writing.

Ah, the writing! The show’s creator, producer, writer, singer, and emcee is a talented fellow in his late 60s named Gary Keillor. He likes to call himself Garrison, for some reason. He’s a terrific writer, revealing gentle humor and a tender heart. He’s also a master at running a tight show.

As a person, Mr. Keillor seems less than perfect. He’s left a trail of unhappy people behind him. He’s invariably in favor of Democrats and reserves real criticism for Republicans. I recall Winston Churchill’s observation, “If when you’re young you’re not a liberal, you have no heart. If, when you’re older, you’re not a conservative, you have no brain”. Mr. Keillor long ago should have matured into a conservative, but he has not. I chalk it up to provincialist naïveté. I don’t care what his politics are, but it bugs me that he feels free to express them, while accepting taxpayers’ money.

I love the witty Guy Noir, Lefty and Dusty, Ruth Gordon Reference Librarian, Ketchup Advisory Board, and Professional Organization of English Majors skits. Mr. Keillor has surrounded himself with a brilliant cast to perform his droll dialogue.

touchAbout the phone
My biggest problem is its touchscreen. I keep accidentally choosing icons when I mean to merely scroll the screen. Maybe if I lost about a hundred pounds, my fingers would shrink enough to work that dinky touchpad.

Visit my website: http://russbellew.com© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

Samsung Exhibit II 4G phone: my second impression

Second impressions are rarely as good as the first impression. Neither is this one.

Samsung Exhibit II SGH-T679 phone

As a phone, this Android phone sounds good. As everything else, it’s frustrating to use. Reasons: short battery life, user-hostile touchscreen interface, confusing windowing, LCD washes out in sunlight.

Yesterday I thought that I’d listen to an interview with an astronomer while I walked a couple of miles, so I logged unto Michio Kaku’s Explorations in Science link on tunein.com, got the MP3 stream going, and stuck the phone in my pocket. Things went fine for a few minutes, until the audio stopped. I examined the phone (carefully trying to avoid pressing on the case, which is a good trick) and discovered that the screen had blanked. I unblanked the screen, and suddenly the Android browser decided that I’d like to see the latest trash news, so I got a page full of Brad and Angelina nonsense. Then I tried to return to Michio Kaku’s page, and when I did, I was forced to restart the entire interview. I did, and maybe five minutes later, it halted again. It went downhill from there.

I suspect that some of this misbehavior is caused by the crapware that T-Mobile has installed on this phone. My next step is to gain root access to the phone, delete the crapware, install Dropbox and Keepass on it, and give it another try.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

My first impressions of Samsung Exhibit II 4G phone

So far, so good.

Samsung Exhibit II SGH-T679 phone

I recently purchased a T-Mobile Samsung Exhibit II 4G SGH-T679 phone from Amazon for about $190. (T-Mobile’s stores sell it for $330. That’s the unsubsidized price.) It’s a second-tier smartphone, but has all of the features that I want in a smallish package. It’s advertised as a prepaid phone, but my postpaid T-Mobile SIM card from my flip-phone worked fine. Based on my few days’ use, I’m not convinced that I want to always carry a smartphone. In many ways, my little Samsung SGH-T439 flip-phone makes more sense for voice, text, and consulting Wikipedia. I predict that I’ll continue to swap my SIM card between the two phones.

I added a Sandisk 30GB microSD card for $20 from Amazon, and a silicone case and screen cover ($8). The phone is lightweight and easily fits in my pants pocket. Its replaceable battery drains quickly, but the phone allows you to turn off power-draining circuits such as WiFi and Bluetooth when they’re not needed. I like the fact that from the Settings menu, I can monitor what purports to be real-time RF signal strength in dBm. I’ve seen this vary from -73 dBm to -109 dBm in my neighborhood.

T-Mobile has loaded this Android phone with apps, most of which I think I’ll delete, once I gain root privileges. That should be an adventure, but is apparently the only way to gain the privileges necessary to delete the apps.

My initial impression of the touchscreen interface is that it’s horrible. Maybe I’ll grow fonder of it with use.

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

Facebook quickly withdraws its stalker’s app

Facebook Friendshake screen
screenshot: facebook
Another reason why I’m glad I don’t have a Facebook account.


Months ago, Facebook acquired Glancee, a small company that had developed a smartphone app that used smartphones’ GPS information to locate people. Facebook renamed it Friendshake, while they tested it within their Facebook mobile apps. In June they renamed it “Find Friends Nearby” (FFN) and quietly rolled it out.

The FFN app was quickly dubbed “the stalker’s app” and within 10 days of release, Facebook withdrew it. You can see if it works or not by going to www.fb.com/ffn.

I’m surprised that Facebook and other social networks can change their games’ rules, as the games are being played. What sort of Terms Of Service (TOS) have Facebook users signed? Apparently it’s a carte blanche.

If you provide an online service, try to change your privacy policy. Most jurisdictions will require that all existing users first agree to the change. The U.S. is lax in its privacy protection, but the EU is strict. I won’t be surprised if they bring suit against Facebook over “Find Friends Nearby”.

I found an informative cellphone site.

LCD-Display of a Mobile Phone under Microscope with 400X
photo: MrPlow
PhoneScoop.com is helping me choose a new cellphone.

The web is loaded with hyperbole about cellphones. The hotter the phone, the hotter the hype. Now that I have a T-Mobile plan that gives me unlimited web access, I realize just how limited my trusty Samsung SGH-T439 clamshell phone’s web capability is. I want my next phone to include at least 3G connect speed, and real email and web browser software.

The Samsung Galaxy S3 seems to be the flavor of the month, but I don’t like to pay a premium just to have the latest gadget. I’m content to stay slightly behind the leading edge and buy gadgets whose prices have cooled since their introduction.

I’ve found phonescoop.com to have what I need: objective data on what seems to be every cellphone ever made, with user reviews. Now I just need to wade through them. I’ll also peruse howardforums.com. Do you have a phone suggestion?

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695