The Short Message Service Centre SMSC
SMSC
MAST
MAST
LOCAL
MOBILE
NET
ME
ME
The Short Message Service (SMS)
The SMS service uses part of the bandwidth capacity of the existing 2G voice
network.
It was originally intended for use by the mobile phone companies to contact their
operatives in the field undertaking maintainance work
The SMSC relays SMS messages from a Mobile Equipment (ME) to another ME
The SMS is sent to the nearest call mast, forwarded to the SMSC. The SMSC
stores the SMS and then attempts to deliver it to the destination ME.
After a preset period of time, known as the Validity Period, the message is deleted
from the SMSC if it cannot be delivered.
The SMS can also be forward on to a computer or logical ME is the mobile
network's LAN.
INTRODUCTION TO DATA OVER GSM
ANALOGUE – e.g V22 etc
SHORT MESSAGE SERVICE – SMS
GPRS
BASIC SMS COMMANDS
AT+CMGS=”+447967123456”
>
ENTER TEXT
CONTROL Z
AT+CMGR=NN
AT+CMGD=NN
AT+CMGW=”+44796123456”
>
ENTER TEXT
CONTROL Z
AT+CMSS = NN
HOW TO FORMAT AN SMSC
AN SMSC IS A LOGICAL ME NUMBER e.g. 07976 123456
1) Always use International dialling code 44 7967 123456
2) Prefix by 19 to identify this as an international dialling code 19 44 7967 123456
3) Ensure there are always a pair of digits, if not back-fill with an F
e.g. if we started with 07967 12345 we get 19 44 7967 12345F
4) Avoid national dialling codes as you never know where your code will be installed
national dialling codes are prefixed by 18
5) Transmit as packed BCD, which requires the BCD nibbles to be swapped around
to ensure the first digit sent is the first number in the string 91 44 97 76 21 43 65
6) Prefix this all with the byte count to tell the ME how long the SMSC number is
FINAL STRING 07 91 44 97 76 21 43 65
OR JUST SEND 00 FOR THE LENGTH WHEN TRANSMITTING
THE ME WILL USE THE DEEFAULT PRE-SET SMSC NUMBER
SMS SUBMIT
SMSC
00
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
User Header
Courtesy of Dream Fabrics
If set it means that the User Data
has a command header prefix
which contains more instructions
as to how to use the data field –
e.g. Multi-part messaging
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Status Report
Courtesy of Dream Fabrics
Request that the SMSC advise
the ME of the status of the SMS
forwarding e.g. proof of delivery
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Validity
Period
Courtesy of Dream Fabrics
How to intepret the VP field, relative,
enhanced, absolute or not-used
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Reject Duplicate
SMS
Courtesy of Dream Fabrics
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Reply path exists
All commercial SMSC's
ignore this
Courtesy of Dream Fabrics
Message Type Indicator
01 = SMS Submit
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Reference Number 00 lets the ME decide
Courtesy of Dream Fabrics
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Reference Number 00 lets the ME decide
Destination Address
Length in digits excluding International dialling byte 0C
International Dialling 19
Then the Number itself 44 7967 123456
0C 91 44 97 76 21 43 65
Courtesy of Dream Fabrics
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Reference Number 00 lets the ME decide
Destination Address 0C 91 44 97 76 21 43 65
Courtesy of Dream Fabrics
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Reference Number 00 lets the ME decide
Destination Address 0C 91 44 97 76 21 43 65
PID or Protocol Identifier
e.g. SMS, Telefax, Telex, Voice,
EMRES, Paging, Teletex,
Universal Computer Interface,
X400, email and a few more
But we only use SMS which is 00
Courtesy of Dream Fabrics
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Reference Number 00 lets the ME decide
Destination Address 0C 91 44 97 76 21 43 65
PID 00
DCS
Data
Coding
Scheme
Courtesy of Dream Fabrics
SMS SUBMIT
SMSC
00
SUM_SUBMIT 11
Reference Number 00 lets the ME decide
Destination Address 0C 91 44 97 76 21 43 65
PID 00
DCS 00
Validity Period AA = 4 days
User data prefixed by a data length – NOTE 7-bit data is compressed
into 8 byte memory
Courtesy of Dream Fabrics
SMS DELIVER
SMSC
0791449776214365
SMS_DELIVER 04
Sender Address 0C 91 44 97 76 21 43 65
PID 00
DCS 00
Time Stamp – Year, Month, Day, Hours, Minutes, Seconds, Time Zone
Reverse BCD
User data prefixed by a data length – NOTE 7-bit data is compressed
into 8 byte memory
Courtesy of Dream Fabrics