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Comment by aditya | Hacker News Reader

It is quite a coup, especially because text messages are essentially free to the carrier:

Looking for a data pipeline that would fit these micro messages, Hillebrand came up with the idea to harness a secondary radio channel that already existed on mobile networks.

This smaller data lane had been used only to alert a cellphone about reception strength and to supply it with bits of information regarding incoming calls. Voice communication itself had taken place via a separate signal.

"We were looking to a cheap implementation," Hillebrand said on the phone from Bonn. "Most of the time, nothing happens on this control link. So, it was free capacity on the system."

via: http://latimesblogs.latimes.com/technology/2009/05/invented-...

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Maybe for the radio part of it, but between cell tower and service center (and vice versa), SMS goes over the signaling links - which are also used for call setup, notifications, WAP push, and routing queries.

Theres nothing free about them, theres no such a thing as free in the telco world - everything costs someone something, though I agree, SMS is extremely cheap for the carrier - definitely NOT worth paying 20 cent for. Carriers love SMS for that exact reason.

Having said that, SMS can also cause the carrier a world of pain... I obviously can't provide any details, but one specific network had a problem where two thirds of all signaling traffic was caused by some virus which a large percentage of their customers' phones were infected with. This was costing them many thousands a day! Thankfully, we were able to block these messages at an early stage in the transaction and reduce network traffic by a substantial amount and over the air traffic by about half.

They are essentially free, because the carriers provide no delivery guarantees for SMS messages. That is, if the channel is busy with other signalling traffic, then SMS messages will be silently dropped.

The TCAP transaction would be retried approx. ten minutes later, up to three times (on the networks I've seen, anyway).

That is true for original GSM networks. However SMS might be using a data channel for delivery instead of control in the latest EDGE,CDMA.

I googled for UTMS 3G (the most usual here in europe), and they still use the FREE signal channel:

"On umts, sms is packet switched - bit rate will be 16k...... cos it is sent on signalling channel."

ref: http://www.wirelessforums.org/uk-telecom-mobile/anyone-know-...

If they were using the regular data channel, and they charged the regular (even though they are inflated as is) data prices, this would be a non-issue.

It's like if the USPS decided to charge a buck for post cards because people liked them more, so the logical thing to do would be to just stick the post-card in an envelope, but then the USPS declared that illegal and outlawed post card sized envelopes.

Quick recap - founding of SMS:

"Mr Matti Makkonen had discussed the idea of a Message Handling Service for GSM digital mobile phone in 1984 in a pizzeria in Copenhagen with two other Finns Mr Tiainen and Mr Tapiola during a conference of mobile phone communication's future.

When the development of GSM digital mobile phone standard was extended from the Nordic countries initiative to the global ETSI workgroup, the idea of SMS was proposed to be included as a global standard. "Without this international collaboration SMS would not have become a global success story", says Makkonen.

Mr Makkonen, did not receive financial payback for his pioneering work because he didn't apply for a patent. "At that time there was an open sharing of ideas by monopoly operators so we never even considered to write a patent application" said Makkonen. "We just started to spread the idea and take care of it into the specifications. The mobile system today is open source and developed from innovations by hundreds of people" he said."

http://www.bookit.net/news/en_GB/makkonen_economist/

We don't know that this is still the case. Text messaging is very popular, and what was once a little-used patch of bandwidth might not be so spare these days. This is not to say that the charges are warranted (except that people pay them) but that the 1985 unused-band consideration isn't as applicable.

This is the basic problem. Geeks like the idea of unlimited bandwidth, but it really isn't a possibility. Physics tells us that you can't have it, especially over wireless.

The only scarcity is in your cell, right now. In 99% of cells, txt messages are free as the signal time slices are going unused (no other texters, low signalling use). At, say, a rock concert, the wireless tubes might be crammed but that's why SMS doesn't have a latency (or delivery?!) guarantee. Also, a mobile base station could be set up at the concert to get more airwaves or there may not be enough voice channels.

So... txt messages are essentially free.

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