A New Connected World Of Mobile-Enabled Sensors (Winter 2014-2015)

Hello, and greetings from the Central Office! Since I wrote last, I have been around the world clockwise once again. It was good to catch up with friends and fellow hackers in Europe and China, and to visit the amazing technology markets in Beijing. Technology changes very rapidly in China and despite being only 6 months from my previous visit, I was really surprised to see how much has changed.

basic GSM handset image

This low cost Arcci GSM phone sells for under $8

One of the most exciting recent developments in telecommunications is the astonishing price drop in mobile phone chipsets, particularly for basic GSM technology. This is combined with massive improvements in both battery technology (which has gotten much greater), charging technology (which can reliably operate off of inexpensive solar cells), and power consumption (which has dropped). In Beijing, you can now buy a brand new, quad band, unlocked GSM world phone for less than $8. These phones can remain powered on, able to make and receive calls, with a standby time of up to two weeks in between charges. Talk time is also truly astonishing. I remember when I barely got an hour of talk time on my enormous Motorola brick analog cellular phone, but basic GSM phones now boast talk time of up to 8 hours of continuous usage—if your voice can hold up for that long!

Just stop for a minute and think about that. For under $15, you can buy a phone that works anywhere in the world for voice, text, and data, and a solar charger to go with it, and even if you don’t charge the phone for 2 weeks, it’ll still be able to make and receive text messages and can even log onto the Internet. It’s completely mind-blowing when you think about it. I think the only reason that most people in Western countries haven’t noticed is that because handsets like these aren’t widely available in wealthier places. When your mobile phone carrier’s lineup is populated with the latest smartphones, it’s hard to notice the availability of no-name Chinese brands at astonishingly low prices.

Now, let me be clear: these inexpensive phones aren’t smart phones, and they don’t support even 3G, let alone 4G technologies. However, they do work just fine for voice, low-speed GPRS data and SMS messaging. And this is the retail price, and even includes value added tax! The wholesale price is about half of this, and it’s for a fully assembled phone. So, you can infer that the component parts are even less expensive than this. Want to support the latest networks and fastest data speeds? The price is about 5 times as much, but we’re still talking about $30 for the components. Making things even more interesting, you don’t necessarily need all of the component parts involved in building a phone when you consider GSM scenarios that aren’t phone calls.

“Wait, a minute,” you may ask. “GSM scenarios that use mobile phone components but don’t involve making phone calls, you say? What might those be?” Well, actually, that’s where things have gotten really interesting. Given the confluence of low cost, low power requirements, and creative charging solutions, some new and really exciting scenarios have been unlocked. Sensors are quietly but steadily being deployed to help automate everything from water and electric meter reading to weather monitoring.

Sure, sensors have existed in various forms and in various places for many years, and there have even been previous efforts at “smart meters.” However, there have been a number of key issues. First of all, most sensors had very limited computing power, because the availability of low-cost microcontrollers with low power consumption was limited. So, the technology was there to gather data, but interpreting it had to be done in a centralized location somewhere; you couldn’t fit enough computing power on a sensor to do much meaningful interpretation. Today, with the availability of Arduino and similar microcontrollers, it’s possible to build sensors with substantial onboard computing resources, without needing a whole lot of energy to do it. This means that sensors don’t necessarily have to upload as much data to centralized locations for real-time processing anymore, because software can be more capable at making real-time decisions. Even if you didn’t need to continuously gather data, or needed to centralize processing, the capability didn’t exist to process data over a wireless WAN at high speed. Nowadays, GSM coverage is available almost everywhere, and 4G allows data transfer at speeds similar to WiFi. This combined with the plummeting cost of sensor technology has unlocked some really incredible new scenarios. Some of the most interesting innovations are in utilities and—oddly enough—agriculture.

Arduino picture

Arduino is an ideal platform for many embedded systems.

Many utilities around the country are starting to deploy smart meters, to which the tinfoil hat crowd has responded with predictable fury (they’re mainly concerned about RF emissions). The Salt River Project in Phoenix has already deployed them in most areas, and the Los Angeles Department of Water and Power is beginning to deploy these as well. While the key reason to (and most important application for) implementing the technology is eliminating the need for meter readers, smart meter technology also allows more data to be collected about energy usage, and more creative billing to take place. You might recall that long distance charges used to vary by time of day and day of week. Calls were billed based on a day rate (the highest price), evening rate (around 20% less), and nights or weekends (around 50% less). This was done to provide an incentive to shift usage to off-peak times, so the phone company didn’t have to build a lot of peak capacity that was otherwise underutilized. Your electric utility could offer similar incentives to use power during off-peak times. For example, Sunday evening is the period of lowest power usage in most cities. So, you might choose to do your laundry on Sunday evening if the rate were half as much as doing it on Monday morning.

crop moisture sensor

This sensor monitors crops for moisture

Agriculture is also seeing a lot of really interesting new scenarios in wireless sensors, which are helping to reduce waste and improve efficiency. For example, farmers waste hundreds of millions of dollars a year replacing spoiled livestock feed. Farmers buy feed and put it in storage. The feed gets wet for one reason or another, and then it spoils. Typically, farmers will find out that this happened when they go to use the feed and find that it has spoiled. So, a company called Kongskilde has developed several types of moisture, temperature and humidity sensors that can be stored with the feed. So, if a leak in the roof develops, the sensors will detect this and notify the farmer before his feed becomes spoiled.

Both of the above smart devices typically rely on a local mesh network, typically WiFi, which then uplinks data to a centralized location via mobile Internet. However, there has been a lot of recent research (with some development) on sensors that communicate directly via mobile Internet. Given the water crisis in California, one of the most interesting pieces of research I have seen involves irrigation systems that are sensor-controlled. Most irrigation systems today operate on timers, and the amount of water used isn’t an exact match for what is actually needed. So, most farmers over-water or under-water their crops (typically the former), which isn’t good for either the crops or the water supply. However, given the vast distances, mesh networks don’t make a lot of sense. These devices, along with other smart devices such as pH monitoring, can literally be “planted” along with crops. The power source? Often solar. In the case of irrigation, the amount of water sprayed can be precisely correct for the exact soil moisture level, leading to both higher crop yields and lower water usage. How can we continue to feed a rapidly expanding human population? Technologies like these will go a long way toward doing so, and they’re all enabled by telecommunications.

And with that, it’s time for me to finish eating this turkey sandwich. Hope you had a happy Thanksgiving, and best wishes for the new year! The world only gets more exciting every day.


https://www.youtube.com/watch?feature=player_detailpage&v=qTqi9xnMf3U – A Smart Meter video from BC Hydro, which provides a good overview of the features and services brought by smart meters.

http://www.bchydro.com/energy-in-bc/projects/smart_metering_infrastructure_program.html?WT.mc_id=rd_smartmeters – Excellent FAQ and information from BC Hydro which in particular describes the science of smart meters. Designed for the tinfoil hat crowd.

http://www.cityofgreensburg.com/MiNet.pdf – Excellent technical whitepaper on Mueller Systems smart meters.

http://www.kongskilde.com/Agriculture/Grain/SensSeed/SensSeed/Wireless%20sensor%20system# -Many technical whitepapers, along with sales brochures, for the Kongskilde agricultural sensor system.

http://ijarcsms.com/docs/paper/volume2/issue1/V2I1-0007.pdf – Detailed academic paper describing a prototype GPRS-based sensor network for irrigation.


Deciphering Tracfone (Spring, 2010)

Hello, and greetings from the Central Office! I’m bundled up, have an electric heater at my feet, and a cup of tea on my desk. Yes, folks, it’s cold and flu season, and I have one or the other of them. Maybe both. It doesn’t matter, though—the company is paying a perfect attendance bonus this month, and all I need to do is make it through at least half of my shift! Outside my Central Office, we have a coin station. It’s an old Western Electric 1D2 set, and it was configured to allow incoming calls until last week. A few months ago, it became one of the busiest coin stations in the city. A shady-looking teenager would hang out all night on Friday and Saturday taking lots of very short incoming calls. A few minutes later, a vehicle would roll into our parking lot, he’d step inside to do business, and then the young entrepreneur would return to his “office.”

An office phone... of sorts.

An office phone… of sorts.

For months, this didn’t bother me. After all, incoming calls generate revenue for the company, the business activities never caused me any trouble, and it made for interesting “service monitoring.” All of that changed last week, though, when a white Camaro pulled into my parking lot at high speed. Squealing tires, skid marks, and the stench of burnt rubber hung in the air… and then the driver did the unthinkable: he burned a donut in my parking lot! Well, that was it. The next morning, my long-neglected coin station had new signage: “OUTGOING CALLS ONLY” – and my young acquaintance moved his business to the mini-mart across the street. His new “office number” became a Tracfone, telecommunications provider to the underworld.

If you have bad credit, run a not-quite-legal business, or are an illegal immigrant, Tracfone is designed for you. No credit checks or identification is required. Better yet, the service is totally anonymous and can be paid for with cash! Owned by Mexican billionaire Carlos Slim, the owner of the dominant Mexican wireline and wireless providers, Tracfone doesn’t actually operate a network in the United States. Instead, it operates as a Mobile Virtual Network Operator, or MVNO, reselling service on both CDMA and GSM networks.

I was interested to learn more about this service, so I purchased a starter kit for about $70 at Wal-Mart. It came with a Samsung T301G handset, 1 year of service, 200 airtime minutes, both wall and car chargers, and a carrying case. The SIM card was pre-installed in the handset, and was designated to AT&T (a “P4” type SIM). Depending upon the market, you may receive a “P5” SIM card, which is designated to T-Mobile.

You can set up the handset either online or over the phone. I set it up online, which was easy and straightforward. To start the process, Tracfone asked for the IMEI of the handset. Next, the site asked for personal information (which isn’t validated—you can enter anything) including a home phone number, and asked if I wanted to opt in for telemarketing and SMS ads (I declined). You can then either port in an existing cellular number or have a new one issued. I chose to have a new number issued. Tracfone requested the ZIP code where I planned to use my phone the most. I entered a Seattle ZIP code and was provided a Seattle number, issued by AT&T Mobility. At that, I was instructed to power cycle the handset. It was automatically programmed over the air and loaded with 210 minutes, with an expiration date 425 days in the future. This was better than the 365 days and 200 minutes promised on the package.

Tracfone has spent a considerable amount of effort to prevent their handsets from being unlocked. This is primarily because of the heavily subsidized nature of their handsets; phones are sold well below cost and the revenue is made up through airtime sales. SIM cards are specialized. They only work on Tracfone-branded handsets loaded with Tracfone “airtime tank” firmware. Once you insert a SIM card for the first time into a Tracfone, it’s forever married to that phone and cannot be used on any other phone. Non-Tracfone SIM cards cannot be used on Tracfone handsets, either.

The firmware of the handset is also locked down, most interestingly in the dial plan. International calls can’t be direct dialed from the handset, even to Canada. Some domestic calls are also blocked even though “Nationwide Long Distance” is promised. Calls to the Commonwealth of the Northern Mariana Islands and Guam are blocked, although calls are permitted to Puerto Rico and the US Virgin Islands. Tracfone does not appear to block calls to high access charge areas, and I was able to complete a call to a chat line in Garrison, Utah (hosted by the independent LEC Beehive Telephone Company). AT&T is the underlying long distance carrier for domestic calls.

To some degree, I was surprised at the friendliness of Tracfone billing. Unlike AT&T Mobility, Tracfone does not bill for ring time beyond the first 30 seconds. Only calls that supervise are charged, and forward audio is even sent on calls that do not supervise. On the other hand, Tracfone bills for calls to customer service, which is unusual for a wireless provider.

While a basic WAP browser is included, you can only visit a pre-approved list of sites linked from the Tracfone portal. Attempting to browse other sites yields a “403 Forbidden” error message. It is possible to download ringtones and some basic applications sold on the Tracfone portal (although some users have worked around this limitation by sending .JAR files to themselves as Gmail attachments). Not surprisingly, Bluetooth is also locked down; only headset profiles are allowed. SMS is allowed (billing 0.3 minutes per message sent or received), but is limited in the dial plan to domestic SMS only.

With all of the efforts made in locking down the handsets and SIM cards, I was curious how much effort Tracfone made to lock down the network. As it turns out, there are a couple of glaring flaws: voicemail and international calling. Voicemail deposits are free with Tracfone, and the AT&T Mobility voicemail platform is used. This service uses a “backdoor number,” to which your handset connects when you check your voicemail. The “backdoor number” is shown briefly on your handset when you hold down the “1” key. Tracfone attempts to conceal this number in the firmware by quickly wiping the display, but by watching carefully and dialing a few times, you’ll be able to capture the number. Calling directly into this number from another phone (such as a land line) prompts you to enter your mobile phone number. You can do this, press * during the announcement, enter your password, and check your voicemail for free. International calling is also free with Tracfone, provided you use a toll-free gateway operated by Auris Technology, a VoIP provider. Calls are of acceptable quality. Most interestingly, the Auris gateway uses only the ANI of your Tracfone for validation, and billing is apparently not synchronized with the AT&T or Tracfone billing platforms. By spoofing the ANI of any Tracfone when dialing this gateway, you can make virtually unlimited long distance calls to over 60 countries.

And… pardon me for a moment. I’m nearly bent in half from coughing fits, and I’m now four hours and one minute into my shift. It’s time for me to go home, and to bring this column to a close. Have a safe and phun spring, and stay healthy!


http://www.tracfone.com – Tracfone official site.

http://www.net10.com – Net10, a Tracfone brand with more expensive phones and cheaper airtime.

http://www.safelinkwireless.com – Safelink Wireless, a Tracfone product targeted toward recipients of public assistance.

http://www.straighttalk.com – Straight Talk Wireless, a Tracfone brand sold exclusively through Wal-Mart and operating on Verizon’s CDMA platform.

http://thejmart.com/difzip.htm – Tracfone tips, tricks and codes.

Other Tracfone Brands

This column focuses on the Tracfone-branded service. For your reference, Tracfone service is marketed under four different brands:

  • Tracfone: The most popular service. Available in all 50 states, offers both GSM and CDMA service depending upon the area in which subscribed. I tested GSM service on the AT&T network. Although monthly plans are available, service is primarily sold by the minute with varying rates depending upon whether the phone subscribed offers “double minutes for life” (DMFL) and the number of minutes purchased at once. Airtime for most cards expires in 90 days, with a 1 year $100 card available. Your minutes roll over if you recharge before they expire.  In general, handsets are heavily subsidized (selling for as little as $10) but minutes are more expensive. International calling is blocked, but dial-around service is available to 60 countries at no additional cost.
  • Net10: Similar to the Tracfone product, using the same billing platform, but all minutes cost 10 cents. Handsets are more expensive and airtime expires sooner. Additionally, international calls cost an extra 5 cents per minute.
  • Safelink Wireless: Operates on the Tracfone billing platform. This service provides a free phone and 55 monthly cellular minutes free for customers who qualify for a federal LifeLine subsidy (generally welfare recipients). Available in 21 states and the District of Columbia.
  • Straight Talk: Marketed exclusively through Wal-Mart, this service is sold with one of two monthly plans costing either $30 (1000 minutes+1000 text+30MB data) or $45 (unlimited text/talk/data). This service includes only Verizon network coverage, with no roaming allowed.