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The Short Message Service Centre SMSC
ME ME
MASTMAST
SMSC
LOCAL MOBILE
NET
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 etcSHORT MESSAGE SERVICE – SMSGPRS
BASIC SMS COMMANDSAT+CMGS=”+447967123456”>ENTER TEXTCONTROL Z
AT+CMGR=NN
AT+CMGD=NN
AT+CMGW=”+44796123456”>ENTER TEXTCONTROL 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 TRANSMITTINGTHE ME WILL USE THE DEEFAULT PRE-SET SMSC NUMBER
SMS SUBMIT
SMSC 00
SMS SUBMIT
SMSC 00
SUM_SUBMIT 11
Courtesy of Dream Fabrics
User HeaderIf 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
Courtesy of Dream Fabrics
Status ReportRequest 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
Courtesy of Dream Fabrics
Validity Period
How to intepret the VP field, relative, enhanced, absolute or not-used
SMS SUBMIT
SMSC 00
SUM_SUBMIT 11
Courtesy of Dream Fabrics
Reject Duplicate SMS
SMS SUBMIT
SMSC 00
SUM_SUBMIT 11
Courtesy of Dream Fabrics
Message Type Indicator01 = SMS Submit
Reply path existsAll commercial SMSC's ignore this
SMS SUBMIT
SMSC 00
SUM_SUBMIT 11
Courtesy of Dream Fabrics
Reference Number 00 lets the ME decide
SMS SUBMIT
SMSC 00
SUM_SUBMIT 11
Courtesy of Dream Fabrics
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
SMS SUBMIT
SMSC 00
SUM_SUBMIT 11
Courtesy of Dream Fabrics
Reference Number 00 lets the ME decide
Destination Address 0C 91 44 97 76 21 43 65
SMS SUBMIT
SMSC 00
SUM_SUBMIT 11
Courtesy of Dream Fabrics
Reference Number 00 lets the ME decide
Destination Address 0C 91 44 97 76 21 43 65
PID or Protocol Identifiere.g. SMS, Telefax, Telex, Voice, EMRES, Paging, Teletex, Universal Computer Interface,X400, email and a few moreBut we only use SMS which is 00
SMS SUBMIT
SMSC 00
SUM_SUBMIT 11
Courtesy of Dream Fabrics
Reference Number 00 lets the ME decide
Destination Address 0C 91 44 97 76 21 43 65
PID 00
DCSDataCodingScheme
SMS SUBMIT
SMSC 00
SUM_SUBMIT 11
Courtesy of Dream Fabrics
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
SMS DELIVER
SMSC 0791449776214365
SMS_DELIVER 04
Courtesy of Dream Fabrics
Sender Address 0C 91 44 97 76 21 43 65
PID 00
DCS 00
User data prefixed by a data length – NOTE 7-bit data is compressed into 8 byte memory
Time Stamp – Year, Month, Day, Hours, Minutes, Seconds, Time ZoneReverse BCD