

Why text messages are limited to 160 characters - bootload
http://latimesblogs.latimes.com/technology/2009/05/invented-text-messaging.html

======
corin_

      Text messaging has become the prevalent form of mobile communication worldwide.
    
      an average of 357 texts per month in [Q2 2008 vs] an average of 204 calls
    

I would think this suggests that calls are still the bigger method of
communication. The average call will last much longer than what could be
written in 160 characters. Also, a ninety second call discussing something
could easily span a number of text messages back and fourth.

 _Edit:_ New point after reading further:

    
    
      Just look at your average e-mail today, he noted. Many can be summed up in the subject line, and the rest often contains just a line or two of text asking for a favor or updating about a particular project.
    

First, I don't accept the premise. Trying to suggest that 160 characters is
more or less enough for the average email is laughable. Hell, a lot of the
time it's not even enough for an SMS message or tweet.

Second, why are they even being compared? Is SMS meant to be just the same as
email but on your phone? Not in my book...

~~~
masklinn
> Second, why are they even being compared? Is SMS meant to be just the same
> as email but on your phone? Not in my book…

They are both ways to interact with others. The argument here is that most
communication do fit in 160 characters when pared down to its essential
components, and thus for most communications SMS are sufficient to replace
emails.

~~~
pavel_lishin
Now say that in 160 characters. :)

~~~
masklinn
Both are communication channels. 160 characters is enough for most thought to
come across. Therefore SMS can replace email in most cases (though not all).

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nicpottier
This is kind of a weird article, it almost contradicts itself a bit.

As the article mentions, SMS'es are kind of piggy-backed with control signals
sent on the network. At first they found they could tack on a 128 character
message, but then reduced the character set further to get to 160 characters.

What isn't clear in the article is when this 'proof' that 160 was enough
occurred. Did it occur after they figured out they could jam 160 in, in order
to validate that 160 would be useful enough? Or did it really occur in the
order that the article talks about, that they first picked 160 characters out
of the sky, then managed to jam that into the signal.

I find the latter to much less likely. 160 just happens to be the most you can
fit in to the packet, which he then validated was probably enough to be
useful.

Anybody know definitely otherwise?

~~~
dkersten
Having spent two and a half years of my life getting intimate with GSM-based
(ie, not CDMA, though a lot of the protocol stack is the same) SMS messages (I
worked for a company that did security, anti spam, anti fraud and other VAS
systems (parental control, blacklist, SMS backup etc) for mobile
operators)[1], I know a little bit about it. Admitedly I could tell you a lot
more about the protocols used by SMS than its history

GSM networks consist of two signalling links: voice and control. The contol is
used to, for example, set up or terminate voice calls. This meant that, in
practice, the control signalling links were generally idle and so they piggy-
backed SMS on it. I don't know anything about the 128 bytes, but the 160
characters comes from the 140 byte payload, when using the 7bit GSM default
packed alphabet. I don't know the numbers offhand (been a year since I've
worked there now), but quite possibly this is, indeed, the maximum packet size
available, though there certainly is a large range of differently sized
packets. In fact, a lot of things are piggy backed on the SMS payload. For
example, when using concatenated messages (or binary data - there was a range
of predefined things that are biggy-backed on SMS as "user data"), the header
telling the phone which message it is is placed at the start of the message
payload (reducing the maximum characters per text by (I don't remember offhand
anymore) ~6 octets. Of course, 160 characters only applies to the 7bit GSM
default alphabet. SMS messages also support 8bit and 16bit payloads.

Mobile operators absolutely love SMS as it is probably the most expensive form
of communication they offer.

Somebody else below mentioned ubiquitous internet as an SMS replacement. While
I think its true for a lot of people in well built-up parts of the world (and
who have a smart phone, a lot of people still don't), its certainly not
global. Hell, even here in Ireland theres areas where cell phone reception is
pretty bad, so while you might manage to send or receive text messages, if you
want to go online you're out of luck. Other, poorer, parts of the world are
even worse off. Actually, I remember one company at the 2009 GSMA Mobile World
Congress in Barcelona was demonstrating a solar panel powered mobile cell
tower, for use in places like Africa, which was designed to provide better
coverage of mainly SMS to large open spaces.

[1] <http://dublindan.posterous.com/things-ive-worked-on-4> We did a lot using
transparent Home Routing <http://en.wikipedia.org/wiki/SMS_home_routing> The
wikipedia article says that transparent home oruting is limited. I disagree.
At least in the lab, we implemented everything from the technical realization
(and then some) on a transparent home routing system. I believe when I left
the company, others were working on a non-transparent version too (because it
is easier/cheaper to get and install hardware for non-transparent operation
than for transparent). But then, we did a lot of non-standard things, we just
did them in ways that don't interfere with the rest of the network.

EDIT: comment didn't end up as interesting as it sounded in my head. Hopefully
somebody found it useful nontheless.

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vilius
Mr. Hillebrand is not a rich man, although given that the text message is a
number 1 overpriced product ([http://www.walletpop.com/2010/09/27/10-most-
overpriced-produ...](http://www.walletpop.com/2010/09/27/10-most-overpriced-
products-you-should-avoid/)) it seems that his work has made huge amounts of
money for the others.

~~~
dkersten
I can confirm that mobile operators absolutely LOVE SMS because it is so
highly overpriced for the amount of data you get to send. They love it so
much, in fact,t hat they are willing on spending large sums of money on
services to improve the SMS network in some way (eg, we did anti-fraud and
anti-spam stuff, amongst other more niche things).

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jarin
Slightly off-topic, but it's a little mind-boggling that they charge 10 cents
per message for something that rides on control signals and gets the lowest
priority on the network.

~~~
muriithi
Here in Kenya we pay between Kshs 1-2 per message to send.

Receiving is free.

Considering that the exchange rate is Kshs 80 to 1$ a message is about 1.25 to
2.50 cents.

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singular
In the UK you can combine several texts together seamlessly so this limit is
meaningful only with respect to billing, and most plans provide so many free
texts that it simply isn't something you think about - is that similar in the
US?

~~~
Qz
Yes for modern phones, although I can't say how many free texts is considered
enough. If you're not on an unlimited plan and you start texting with someone
who is, you can quickly stack up hundreds of texts without realizing it...

~~~
singular
True, and that is of course applicable here in the UK too, however it is rare,
in my experience at least, to see people being too concerned about text
length. In the past people would be very anal about using 'text speak' i.e. hi
m8, how r u? partly to fit into the char limit.

------
perlgeek
Somehow this reminds me of the story that the length of audio CDs was chosen
so that Beethoven's Symphony No. 9 would fit onto one CD (see for example
<http://www.snopes.com/music/media/cdlength.asp> )

~~~
corin_
Seems it may actually be more than just a myth.

See the penultimate paragraph on
[http://www.dutchaudioclassics.nl/?strPage=Info&strBrand=...](http://www.dutchaudioclassics.nl/?strPage=Info&strBrand=Various&strType=The_cd_laser&blnSefURL=true)

Wikipedia also gives
[http://www.aes.org/historical/store/oralhistory/?code=OHP-01...](http://www.aes.org/historical/store/oralhistory/?code=OHP-016-DVD)
as a source for the Beethoven story being true, although you have to buy that
interview to actually hear it.

------
smanek
_U.S. mobile users sent an average of 357 texts per month in the second
quarter of 2008 versus an average of 204 calls, the report said._

The average person sends ~ 10 text messages and makes 7 calls a day?

Wow, I'm behind the curve ...

~~~
dododo
the mean isn't a robust statistic. i don't think your inference is correct in
this case.

a single user can theoretically throw the mean off from the central tendency
completely. i would imagine there are a few users that send a lot more text
messages and calling more than most people, biasing the result. it would be
more useful to talk about the median in this case, i think.

[http://en.wikipedia.org/wiki/Robust_statistics#Examples_of_r...](http://en.wikipedia.org/wiki/Robust_statistics#Examples_of_robust_and_non-
robust_statistics)

~~~
kenjackson
Agreed. I know many ppl who send 1000 or more texts per month. But I don't
think there exist many in the world who make that many calls for personal use.

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Derbasti
What an anachronistic technology in a world of ubiquitous internet
connections. I, for one, _hate_ SMS.

~~~
gaius
_a world of ubiquitous internet connections_

Haha, I dunno what world that is, I regularly travel to places where there's
no GPRS/EDGE/whatever but there is good ol' GSM. Or sometimes there is data
but it's prohibitively expensive.

Incidentally if you hate SMS you probably just have a crap phone. BlackBerry
for one presents the same interface for SMS, IM, whatever, the underlying
transport is irrelevant to the experience. I guess iPhone and Android are the
same.

~~~
Derbasti
I can tell you what world that is. It is the 'old world', Europe. I live in
Germany. I have an iPhone. I have 'net access virtually everywhere including
all of western Europe. I pay 30$ per month for it.

I have lived in the US for a while, and I can tell you: US mobile carriers
offer incredibly bad service for incredibly high prices. All of western Europe
is _way_ ahead of AT&T or Comcast in these regards. I have not had a single
'dropped call', ever. This problem just does not exist outside the US (except
when you enter a tunnel, of course).

Hence, I can always send emails, or even Facebook or Twitter updates from
anywhere. Why would I want to send an SMS instead?

~~~
jarek
Your "old world", western Europe, is an outlier. Head out into the middle of
nowhere in northern Norway and see how your Facebook works.

~~~
Derbasti
You could argue that Norway would be 'Northern Europe', but I guess that is
hypocritical.

Germany, France, Switzerland, Austria, Netherlands, Belgium and England have
very good coverage, though.

~~~
jarek
Those countries combine for approximately 242.63 million people and 1,236,644
km^2, or 3.5% of the world's population and about 0.8% of the world's total
land area.

------
masklinn
They're not limited to 160 characters, _any_ GSM phone is able to create and
receive segmented SMS (a single message over multiple segments), up to 255
segments of 134 bytes.

I have read CDMA phones are not able to perform such an amazing feat though.

~~~
dkersten
User Data Header => UDH Length + Information Element Identifier + Information
Element Length + Concatenated Message reference number + Sequence Number of
Part + Number of Parts. Each is one octet, for a total of 6. Hence 134 octets,
Note that the user data header can, conceptually (I have not seen it in
practice, but the spec allows it) contain multiple information elements of
varying sizes.

I don't know much about CDMA, but from the little I did interact with it, the
upper levels of the protocol stack (TCAP upwards) looked almost identical to
me. Does this mean that CDMA "phones" never implemented this or is it a
protocol issue?

~~~
masklinn
> Does this mean that CDMA "phones" never implemented this or is it a protocol
> issue?

I do not know, I just read recently that CDMA had no segmented SMS (in
relation to the CDMA iPhone I believe, but for the life of me I can't remember
the source). I just threw it out there in case somebody had the knowledge to
infirm or confirm it.

If it was in relation to the CDMA iphone indeed, I'd expect it's either in the
baseband or a protocol issue, since GSM iPhone has no issue with segmented SMS
(in either production or consumption)

~~~
dkersten
It would be very strange if the phones just didn't implement it, so at a guess
I'd say its a protocol issue too, but as far as I remember, the upper levels
of the protocol stack were the same between GSM and CDMA so I don't see why
the protocol wouldn't support it (since the user data is inside the message
payload itself and doesn't interact with the rest of the payload. I guess CDMA
must not support a user data header for some reason?

I'd be very interested in hearing if this is true or not, if anybody knows.

~~~
masklinn
Googling a bit, I found the following on an SMSC's website:

> In CDMA environments, no standard for segmentation exists. Therefore, the
> WAP Forum defined its own standard for the sending of segmented WDP messages
> in a CDMA environment.

> A key requirement of this standard is that each segment of the message must
> use the same CDMA SMS message id. However, the CDMA SMS message id field is
> a value that is generated by the SMSC, and cannot be set by an application
> that is submitting messages to the SMSC, such as an MMSC or WAP Push Proxy
> Gateway.

A number of email threads seem to indicate concatenated SMS are available on
some CDMA phones but not others (and most notably appear missing on a number
of CDMA Blackberry devices, to the point that there are software built for
auto-splitting:
[http://www.mobihand.com/product.asp?id=28752&n=Beyond160](http://www.mobihand.com/product.asp?id=28752&n=Beyond160)),
I have found no indication on whether the process was as seamless as on GSM,
but the quote above seems to indicate the limitations are quite heavy and
segmented SMS are _not_ supported by CDMA itself.

~~~
dkersten
Oh, interesting. Thanks for that.

I only worked with GSM messages myself, so I don't know how it compares to
CDMA. From what little I did see of CDMA I thought they would be fairly
similar, but I guess theres more involved. GSM is a pretty versatile system,
though.

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jcromartie
Because cellular providers love massive piles of cash?

