Here's the exact calculation of the PDU splitting borders.
On the wire and in the air, a SMS PDU always contains a maximum of
140 octets.
Thats why you can pack 140*8/7 = 160 characters into an SMS.
If a UDH header is used (udh indicator bit is set), then the
beginning of the SMS-PDU contains the UDH (universal data header).
The UDH is 6 octets for a splitted text sms. This leaves us with 134
octets remaining.
134 octets are 1072 bits. in 1072 bits you can pack 153 septets and
you are left over with one spare bit.
This is where the 153 character limits for split SMS comes from.
On 31.01.2007, at 10:16, Alexander Malysh wrote:
Hi,
for 7bit (text message) kannel send 154 octets of text + 6 octets
udh that give you 160 Octets together. SMPP doesn't pack because
it's not necessary following the spec but SMSC packs then those.
Am 31.01.2007, 09:41 Uhr, schrieb Hillel <[EMAIL PROTECTED]>:
Hi,
I've been looking at the spec 03.40 and I've also tested and 154
is the max
amount of chars you can use before becoming another SMS.
If I re-read the spec below with this information, can I assume
Kannel is
using compressed GSM Default alphabet 7 bit data and you always
lose 6
octets to give you 134 octets left which translates into 154 chars.?
(If it was using uncompressed GSM Default 7 bit data then you
would only
have 153 chars per concatenated SMS.)
Is my understanding correct?
9.2.3.24.1 Concatenated Short Messages
This facility allows short messages to be concatenated to form a
longer
message.
In the case of uncompressed 8?bit data, the maximum length of the
short
message within the TP?UD field is 134 (140?6) octets.
In the case of uncompressed GSM Default 7 bit data, the maximum
length of
the short message within the TP?UD field is 153 (160?7) characters.
In the case of 16 bit uncompressed USC2 data, the maximum length
of the
short message within the TP?UD field is 67 ((140?6)/2) characters.
A UCS2
character must not be split in the middle; if the length of the
User Data
Header is odd, the maximum length of the whole TP-UD field is 139
octets.
In the case of compressed GSM Default alphabet 7 bit data, 8 bit
data or
UCS2 the maximum length of the compressed short message within the
TP-UD
field is 134 ( 140-6) octets including the Compression Header and
Compression Footer, both or either of which may be present ( See
subclause
3.9).
The maximum length of an uncompressed concatenated short message
is 39015
(255*153) default alphabet characters, 34170 (255*134) octets or
17085
(255*67) UCS2 characters.
Thanks for your great response.
Rgds
--
Thanks,
Alex
Andreas Fink
Fink Consulting GmbH
Global Networks Schweiz AG
BebbiCell AG
---------------------------------------------------------------
Tel: +41-61-6666330 Fax: +41-61-6666331 Mobile: +41-79-2457333
Address: Clarastrasse 3, 4058 Basel, Switzerland
E-Mail: [EMAIL PROTECTED]
www.finkconsulting.com www.global-networks.ch www.bebbicell.ch
---------------------------------------------------------------
ICQ: 8239353 MSN: [EMAIL PROTECTED] AIM: smsrelay Skype: andreasfink
Yahoo: finkconsulting SMS: +41792457333
