They are installed on pretty much on every bridge over major roads these days: Traffic jam sensors. Recently, I got to see one close up and found it quite interesting that they are totally autonomous, no network cable (of course) but also no power cable. Have a look at the picture on the left. According to the website of the company that has deployed those sensors, data is sent over the GSM network when necessary, i.e. only when the traffic flow changes. No mention whether SMS or GPRS is used for the data exchange.
Then I wondered how much power the sensor draws and if the solar panel could supply enough power for a round the clock operation? The module has a size of about a quarter of a square meter so how much power could it deliver per day? From experience with a solar panel that had a size of about 4 square meters that could deliver about 500 watts under best conditions this module could perhaps deliver around 30 watts under the best conditions. Now the sun is not always shining so perhaps the module delivers 100 Wh per day. Is that enough?
That depends on how much power the device draws. The radio module itself is probably pretty efficient. Idle mode power consumption of embedded modules is typically less than 10 mW. So letting it run around the clock would result in a power consumption of the radio module of around 0.24 Wh per day plus the increased power consumption for communication. I assume the device only communicates rarely so this value should not increase much. And then there's the application processor board and the sensors themselves. As their main job is to count and analyze impulses it gets when cars move under the sensor I can imagine that its power consumption is equally low. But even if it takes a full watt, the solar panel and a battery to store energy for nighttime should be way sufficient to drive the device. And a full watt is already quite a lot, even a Raspberry Pi Model A under full load is specified to take only 1.5 Watts.
With all that is going on at the moment in the UK with the Orange/T-Mobile merger, LTE in 1800 MHz, upcoming auctions for 800 and 2600 MHz spectrum in 2012, potential sale of 1800 MHz spectrum of EE to H3G, etc. it's a bit difficult to keep track of who actually has spectrum where and how much. Is your head spinning? Mine does.
But here's an interesting document released by Ofcom that shows who has what kind of spectrum in 2012 that sheds some light on the current situation. The details are on page 8. Quite insightful.
It looks like even though SMS messages can't be sent free of charge, SMS spam and fraud seem to be on the increase and I suspect a significant part of the population may be vulnerable to be tricked into calling premium numbers that way.
When I recently talked to a somewhat elderly person I was told a story about an SMS the person had received which looked like it was sent by a popular parcel service company. The message said that they had tried to deliver a parcel but found nobody at home to receive it. The message then requested the person to dial the number in the SMS message (or click on it) to call the parcel service to arrange for another delivery. The number, of course was a premium number but not all people recognize such numbers, especially in countries that don't use 0900 or other well known codes for such numbers.
In this particular case, no damage was done because when the person tried to call the number it was already deactivated. It looks like the fraud was discovered and shut down.
What is really bad about the whole thing is that even after I explained that the SMS message was a scam to trick people into calling premium numbers, the person still insisted that the message has come from the parcel delivery service. I am not sure my explanation has sunk in :-( And the person I was talking to was not dumb, just not born in the mobile age...
When watching the Sol 4 press conference for the Mars Science Laboratory (MSL) mission, better known for the Curiosity rover, the person responsible for the on-board computers was saying that the on-board computer was less powerful than an iPhone. One reporter in the audience was totally baffled by this and asked how it was possible to fly to Mars with something that had less power than the smartphone in his pocket.
A very revealing question as it shows that the general public has no idea of how much processing power is required if no screen is attached to a device and software is highly optimized for a specific purpose. It would probably be even more incomprehensible to him that when flying to the moon, the Apollo Guidance Computer did not run at 1 GHz like his iPhone, but at a mere 2 MHz (500 times slower clock speed), and instead of Gbytes of RAM and flash it contained the equivalent of a meager 4 kbytes of RAM and 64 kbytes of ROM. For the details see here and for the details on the bit level have a look at this excellent book which I just recently finished reading. In other words, the specs are similar to those of a 1980's Commodore 64, even though it's difficult to compare those two computers due to their very different purposes.
But anyway, this made me wonder how many times you could store a C64 game that filled the better part of a 5.25" disc or tape in the days of the C64 on an iPhone with 16 GB of flash today. Let's take the original Giana Sisters game on the C64 for the calculation. The disk image has a size of 174 kbytes to play it in a C64 simulator today. And that's already quite big as the C64 only had 64k of RAM so perhaps it was compressed in some form or shape in memory. But anyway, 174 kbytes it is, more than the ROM of the Apollo Guidance computer could have held only a decade and a half earlier. For the comparison let's take an iPhone with 16 GB of flash, which is roughly 16 000 MB or roughly 16 000 000 kb. The game would fit into the flash memory 91 954 times!
An annoyance when working on the settings of a network is that the PC used for the task becomes part of that network and depending on the job, looses Internet connectivity. Even if a 3G stick or second network adapter is used, DHCP settings, which are part of the setup mingle with the PCs settings and again cut the Internet connection. A hassle I have now found a remedy for: Wi-Fi in a Virtual Machine.
A few weeks ago I had a post on how to do 3G testing in a virtual machine but this did not extend to working in wired or Wi-Fi network. But by simply getting a USB Wi-Fi stick and making it available to the guest operating system running in the virtual machine, working on a network is completely isolated from the host computer. The picture on the left shows how this looks in practice. The host operating system uses the built in Wi-Fi chip while the guest operating system (Windows XP in the window) uses a USB Wi-Fi stick and connects to the network to be configured. No matter what is done there and how that affects the client operating system, the host operating system (Ubuntu in my case) is entirely unaffected from the changes as it uses a different network and Internet connectivity remains in place.
And if you have enough RAM you can even launch two or three virtual machines simultaneously, each using a different Wi-Fi or 3G dongle connecting to different networks. Great for testing VPN solutions, NATing, etc. etc. The more I play with Virtual machines, the more uses I find for them.