2 Overview:

MS SME

MS	Mobile Station
SME	Short Message Entity
SMSC	Short Message Service Center
MMI	Man Machine Interface
PDUs	Protocol Data Units
SM-AL	Short Message Application Layer
SM-TL	Short Message Transport Layer
SM-RL	Short Message Relay Layer
SM-LL	Short Message Link Layer

The MMI is based on the command set of AT+Cellular, and could be realized by means of a terminal (for example Triodata, Telix, WIN-Terminal) or the display of a handy.

The SM-TL provides a service to the Short Message Application Layer. This service enables the SM-AL to transfer short messages to its peer entity, receive short messages from its peer entity and receive reports about earlier requests for short messages to be transferred. The SM-TL communicates with its peer entity with six several PDUs (Protocol Data Units):

· SMS-DELIVER, conveying a short message from the SMSC to the MS

· SMS-DELIVER-REPORT, conveying a failure cause (if necessary)

· SMS-SUBMIT, conveying a short message from the MS to the SMSC

· SMS-SUBMIT-REPORT, conveying a failure cause (if necessary)

· SMS-STATUS-REPORT, conveying a status report from the SMSC to the MS

· SMS-COMMAND, conveying a command from the MS to the SMSC

The SMS-DELIVER and SMS-SUBMIT PDUs are described in the following sections.

2.1 SMS-DELIVER (Mobile Terminated)

2.2 SMS-SUBMIT (Mobile Originated)

notice: Any unused bits will be set to zero by the sending entity and will be ignored by the receiving entity

SCA	Service Center Address information element	Telephone number of the Service Center
PDU Type	Protocol Data Unit Type
MR	Message Reference	successive number (O. .255) of all SMS-SUBMIT Frames set by the MOBILE
OA	Originator Address	Address of the originating SME
DA	Destination Address	Address of the destination SME
PID	Protocol Identifier	Parameter showing the SMSC how to process the SM (as FAX, Voice etc)
DCS	Data Coding Scheme	Parameter identifying the coding scheme within the User Data (UD)
SCTS	Service Center Time Stamp	Parameter identifying time when the SMSC received the message
VP	Validity Period	Parameter identifying the time from where the message is no longer valid in the SMSC
UDL	User Data Length	Parameter indicating the length of the UD-field
UD	User Data	Data of the SM
RP	Reply Path	Parameter indicating that Reply Path exists
UDHI	User Data Header Indicator	Parameter indicating that the UD field contains a header
SRI	Status Report Indication	Parameter indicating if the SME has requested a status report
SRR	Status Report Request	Parameter indicating if the MS has requested a status report
VPF	Validity Period Format	Parameter indicating whether or not the VP field is present
MMS	More Messages to Send	Parameter indicating whether or not there are more messages to send
RD	Reject Duplicate
MTI	Message Type Indicator	Parameter describing the message type 00 means SMS-DELIVER 01 means SMS-SUBMIT

3 Parameter description

3.1 Service Center address information element (SCA info element)

len:

The octet “len” contains the number of octets required for the number of the Service Center plus the 1 byte ,,type of number”

type of number:

81H: the following number is national

91H: the following number international

(for further information see GSM 04.08 chapter 10.5.4.6)

octet:

One octet includes two BCD-digit Fields

If the called party BCD number contains an odd number of digits, the last digit shall be filled with an end mark coded as “FH”

Example:

if you have the SC-number +49 1 7 1 0760000 you have to type:

0791947101670000

notice: If the “len” field is set to Zero the MOBILE takes the default value of the Service Center address set by the AT+CSCA command

3.2 Protocol Data Unit Type (PDU Type)

! notice: you have to write the PDU-type in Hex-Format, a possible example is “11H”!

RP: 0 Reply Path parameter is not set in this PDU

1 Reply Path parameter is set in this PDU

UDHI: 0 The UD field contains only the short message

1 The beginning of the UD field contains a header in addition of the short message

SRI: (is only set by the SMSC)

0 A status report will not be returned to the SME

1 A status report will be returned to the SME

SRR: O A status report is not requested

1 A status report is requested

VPF: bit4 bit3

0 0 VP field is not present

0 1 Reserved

1 0 VP field present an integer represented (relative)

1 1 VP field present an semi-octet represented (absolute)

any reserved values may be rejected by the SMSC

MMS: (is only set by the SMSC)

0 More messages are waiting for the MS in the SMSC

1 No more messages are waiting for the MS in the SMSC

RD: 0 Instruct the SMSC to accept an SMS-SUBMIT for an short message still

held in the SMSC which has the same MR and DA as a previosly

submitted short message from the same OA.

1 Instruct the SMSC to reject an SMS-SUBMIT for an short message still

held in the SMSC which has the same MR and DA as a previously

submitted short message from the same OA.

MTI: bit 1 bit 0 Message type

0 0 SMS-DELIVER (SMSC ==> MS)

0 0 SMS-DELIVER REPORT (MS ==> SMSC, is generated automatically by the MOBILE, after receiving a SMS-DELIVER)

0 1 SMS-SUBMIT (MS ==> SMSC)

0 1 SMS-SUBMIT REPORT (SMSC ==> MS)

1 0 SMS-STATUS REPORT (SMSC ==> MS)

1 0 SMS-COMMAND (MS ==> SMSC)

1 1 Reserved

(the fat-marked lines represent the features supported by the MOBILE)

notice: not every PDU Type is supported by the Service Center

3.3 Message Reference MR

The MR field gives an integer (O. .255) representation of a reference number of the SMSSUBMIT submitted to the SMSC by the MS.

notice: at the MOBILE the MR is generated automatically, -anyway you have to generate it-

a possible entry is for example “00H”

3.4 Originator Address OA Destination Address DA

OA and DA have the same format explained in the following lines:

The octet “len” contains the number of BCD digits

type of number:

81H: the following number is national

91H: the following number international

(for further information see GSM 04.08 chapter 10.5.4.6)

BCD-digits:

The BCD-digit Field contains the BCD-number of the Destination e.g. of the Originator

If the called party BCD number contains an odd number of digits, the last digit shall be filled

with an end mark coded as “FH”

Example:

if you have the national number 1234567 you have to type:

0781214365F7

3.5 Protocol Identifier PID

The PID is the information element by which the Transport Layer either refers to the higher layer protocol being used, or indicates interworking with a certain type of telematic device. here are some examples of PID codings:

00H:The PDU has to be treat as a short message

41H: Replace Short Message Type 1

42H: Replace Short Message Type 2

43H: Replace Short Message Type 3

47H: Replace Short Message Type7

If “Replace Short Message Type x” is present, then the MS will check the associated SC address and originating address and replace any existing stored message having the same Protocol Identifier code, SC address and originating address with the new short message and other parameter values. If there is no message to be replaced, the MS shall store the message in the normal way.

(for further information see GSM 03.40 chapter 9.2.3.9)

notice: it is not guaranteed that the SMSC supports every PID codings

3.6 Data Coding Scheme DCS

The DCS field indicates the data coding scheme of the UD (User Data) field, and may indicate a message class. the octet is used according to a coding group which is indicated in bits 7. .4. The octet is then coded as follows:

Default alphabet indicates that the UD (User Data) is coded from the 7-bit alphabet given in the appendix.

When this alphabet is used, eight characters of the message are packed in seven octets, and the message can consist of up to 1 60 characters (instead of 140 characters in 8-bit data coding)

In 8-bit data coding, you can relate to the INTEL ASCII-HEX table.

In Class O (immediate display) the short message is written directly in the display, as the Ml has no display the Class O message can be realised only in a roundabout way.

In Class 1 to Class 3 the short message is stored in the several equipments ME, SIM-card and TE.

In time the Class 2 is supported, if you choose Class 1 or Class 3 the short message is treated the same way as a Class 2 message.

note: It is recommended to use the Class2 message, or the coding group “0000 bin”

3.7 Service Center Time Stamp SCTS

The SCTS is the information element by which the SMSC informs the recipient MS about the time of arrival of the short message at the Transport Layer entity of the SMSC. The time value is included in every SMS-DELIVER being delivered to the SMSC, and represents the local time in the following way:

The Time Zone indicates the difference, expressed in quarters of an hour, between the local time and GMT (Greenwich Main Time).

3.8 Validity Period VP

The Validity-Period is the information element which gives an MS submitting an SMSSUBMIT to the SMSC the possibility to include a specific time period value in the short message. The Validity Period parameter value indicates the time period for which the short message is valid, i.e. for how long the SMSC shall guarantee its existence in the SMSC memory before delivery to the recipient has been carried

The VP field is given in either integer or semi-octet representation. In the first case, the VP comprises 1 octet, giving the length of the validity period, counted from when the SMSSUBMIT is received by the SMSC. In the second case, the VP comprises 7 octets, giving the absolute time of the vality period termination.

In the first case, the representation of time is as follows: