SMS Messaging

1.0 Introduction

To use the SMS you have to declare the number of the Short Message Service Centre (SMSC[1]) in the Mobile Station (MS), provided that the MS supports Short Message Service-Mobile Orginated (SMS-MO).

The M20 Terminal supports SMS-MO.

At the M20 Terminal you enter the SMSC-number with the AT+Celular command:

at+csca = ?<SMSC-number>?

If the receiver of the SMS possesses a Telstra SIM card, the AT command has to be entered in the following way:

at+csca = "+61418706700"

With the command

at+csca? 

you can question the current SMSC-number.

Ask your network operator for the right SMSC-number !!

2.0 Overview

SMS Messaging Files
MS: Mobile Station
SME: Short Message Entity
SMSC: Short Message Service Centre
MMI: Man Machine Interface
PDUs: Protocol Data Units
SM-AL: Short Message Aplication 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 Win-Terminal, HyperTerminal, etc) 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):

The M20 Terminal supports the SMS-DELIVER and SMS-SUBMIT PDUs as 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 !
SCAService Centre Address ? information elementTelephone number of the Service Centre
PDU Type
MR
Protocol Data Unit Type
Message Reference
Sucessive number (0..255) of all SMS-SUBMIT Frames set by the M20
OAOriginator AddressAddress of the originating SME
DADestination AddressAddress of the destination SME
PIDProtocol IdentifierParameter showing the SMSC how to process the SM (as FAX, Voice etc)
DCSData Coding SchemeParameter identifying the coding scheme within the User Data (UD)
SCTSService Centre Time StampParameter identifying time when the SMSC received the message
VPValidity PeriodParameter identifying the time from where the message is no longer valid in the SMSC
UDLUser Data LengthParameter indicating the length of the UD-field
UDUser DataData of the SM
RPReply PathParameter indicating that Reply Path exists
UDHIUser Data Header IndicatorParameter indicating that the UD field contains a header
SRIStatus Report IndicationParameter indicating if the SME has requested a status report
SRRStatus Report RequestParameter indicating if the MS has requested a status report
VPFValidity Period FormatParameter indicating whether or not the VP field is present
MMSMore Messages to SendParameter indicating whether or not there are more messages to send
RDReject Duplicate 
MTI Message Type Indicator
00 means SMS-DELIVER
Parameter describing the message type
01 means SMS-SUBMIT

3.0 Parameter description

3.1 Service Centre address information element (SCA info element)

SMS messaging files len:

The octet ?len? contains the number of octets required for the number of the Service Centre 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 +61418706700 you have to type:

07911614786007F0

! Notice: If the �len� field is set to Zero the M20 Terminal takes the default value of the Service Centre address set by the AT+CSCA command!

3.2 Protocol Data Unit Type (PDU Type)

SMS-SUBMIT:                                                  SMS-DELIVER:

! 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:   0    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 previously      
           submitted short message from the same OA.
       1   Instruct the SMSC to reject an SMS-SUBMIT for a 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:   bit1    bit0    Message type
       0       0       SMS-DELIVER (SMSC ==> MS)
       0       0       SMS-DELIVER REPORT (MS ==> SMSC, is generated automatically by

the M20, 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 M20 Terminal)

! Notice: not every PDU Type is supported by the Service Centre !

3.3 Message Reference (MR)

The MR field gives an integer (0..255) representation of a reference number of the SMS-SUBMIT submitted to the SMSC by the MS.

! Notice: at the M20 Terminal 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:

len:

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. 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
01H: The PDU has to be treat as a telex
02H: The PDU has to be treat as group3 telefax
03H: The PDU has to be treat as group4 telefax

(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:

Coding group:
Bits 7..4
bits 3..0
0000

Alphabet indication

Unspecified message handling at the MS

0000 Default alphabet (7 bit data coding in the User Data)

0001-1111 reserved

0001-1110Reserved coding groups
1111

Data Coding/message class

bit 3 is reserved, set 0

bit 2 (message coding)

0 Default alphabet (7 bit data coding in the User Data)

1 8-bit data coding in the User Data

bit 1 bit 0 (message class)

0 0 Class0 immediate display

0 1 Class1 ME (Mobile Equipment)- specific

1 0 Class2 SIM specific message

1 1 Class3 TE (Terminate Equipment)- specific

Default alphabet indicates that the UD (User Data) is coded from the 7-bit alphabet given in appendix A. When this alphabet is used, eight characters of the message are packed in seven octets, and the message can consist of up to 160 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 0 (immediate display) the short message is written directly in the display, as the M20 Terminal has no display the Class 0 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 Centre 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 SMS-SUBMIT 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 out.

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 SMS-SUBMIT 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:

VP Value Validity period value
0-143(VP + 1) x 5 minutes (i.e 5 minutes intervals up to 12 hours)
144-16712 hours + ((VP-143) x 30 minutes)
168-196(VP-166) x 1 day
197-255(VP - 192) x 1 week

In the second case, the representation of time is identical to the representation or the SCTS (Service Centre Time Stamp).

The case of representation is set in the VPF (Validity Period Format) in the PDU-type.

3.9 User Data Length (UDL) and User Data (UD)

The UDL field gives an integer representation of the number of characters within the User Data field to follow.

4. PDU Examples

Here are two examples of how to send a short message with AT+Cellular (refer to Appendix B for more details on how to send the SMS messages):

First enter PIN-number and the Service Centre Address:

at+cpin="XXXX"            enter the PIN-number
OK
at+csca="+61418706700"    enter the Service-Centre-Address (Telstra)
OK
== 1st Example ==


at+cmgs=18                                enter �send message�, 18 is the actual length of the PDU
                                          message in octet
> 0011000A81409079344400000105E8329BFD06  type the PDU (SMS-SUBMIT) and finish with �ctrl Z� the thin-typed
                                          characters are the Destination Address e.g. the own 
                                          tel.-number(0409974344) the Service Centre address is the same 
                                          as set via at+csca command

+CMGS: 0
OK

at+cpms?                                  are messages stored on the SIM-Card?
+CPMS: "SM" , 1 , 7 , "SM" , 1 , 7        on this SIM-Card is 1 message stored
OK                                        you can store at most 7 messages

at+cmgr=1                                 read stored message in location 1
+CMGR: 0,,24
07911614786007F0040B911604994743F400009930139100406B05E8329BFD06     This is a PDU (SMS-
OK                                        -DELIVER) sent by the
                                          Service Centre
== 2nd Example ==


at+cmgw=18                                write message in the memory of the SIM-card
> 07911614786007F011000781409079344400F6AA0568656C6C6F  type the PDU (SMS-SUBMIT) and finish with �ctrl Z� the thin-typed characters are the Destination Address e.g. the own tel.-number (0409974344). The Service Centre Address is �+61418706700�
+CMGW: 2

OK

at+cmgr=2                                 read stored message in location 2
+CMGR: 2,,18
07911614786007F011000A81407008090500F6010568656C6C6F      this is the PDU stored in location 2
OK

at+cmss=2                                 send the message stored in location 2
+CMSS: 3
OK

at+cmss=2,�0407485455�,129                send the message stored in location 2 to the national 
                                          (129 = 81H) destination address �0407485455�
at+cmss=2,�+61419877302�,145              send the message stored in location 2 to the international 
                                          (145 = 91H) destination address �+61419877302�

at+cpms?                                  are messages stored on the SIM-Card?
+CPMS: "SM" , 3 , 7 , "SM" , 3 , 7        on this SIM-Card are 3 message stored
OK                                        you can store at most 7 messages

at+cmgr=3                                 read stored message in location 3
+CMGR: 0,,24
07911614786007F0040B911604994743F400009930139100406B05E8329BFD06     This is a PDU (SMS-
OK                                        -DELIVER) sent by the

Appendix A - Default Alphabet

    b700001111
    b600110011
    b501020101
b4b3b2b101234567
00000@ SP0 P p
00011  !1AQAq
00102$  2BRBr
00113   3CSCs
01004   4DTDt
01015  %5EUEu
01106  &6FVFv
01117  7GWGw
10008  (8HXHx
10019  )9IYIy
101010LF *:JZJz
101111  +;KK
110012  ,<LL
110113CR -=M M 
111014 .>NN
111115  /?O O 

Abbreviations:

Error codes:

Appendix B- SMS set up for the M20 Terminal

This document describes the process of sending SMS messages between a mobile phone and the M20 Terminal. The mobile phone referred to in this document is the Ericsson GH688. However, SMS message can be sent out or received in a similar fashion using other mobile phones.

Hardware Requirements

The following items are needed.

Hardware Set Up

Mobile Phone Set Up

Insert a SIM card into the mobile phone and turn the phone on. The phone is now ready for sending and receiving SMS. Note that you need the phone number for SMS messages.

M20 Terminal Set Up

Connect the M20 Terminal to a PC as shown in Figure 1. Then do the following:

AT+CMGF=0[ENTER][2]                 Set the M20 Terminal to PDU mode
AT+CMGF=1[ENTER]                    Set the M20 Terminal to text mode[3]
		
AT+CSCA=�+61418706700�[ENTER] Enter the SMS Centre Address
		
Note that the Service Centre Address only needs to be entered once for all SMS.

Figure 1: M20 Terminal Set Up

Sending a SMS Message

Phone initiated SMS Message

A mobile phone that is capable of sending and receiving SMS messages can be used to send a SMS message to the M20 Terminal. Note that the SIM card for the mobile phone must be on the same network as the SIM card in the M20 Terminal for SMS messages. eg. both SIM cards must be Telstra, or Optus.

To send a SMS message to the M20 Terminal, select [Send Messages] from the [Mail] menu and then select [New]. Enter your text and when you have finished press the �YES� button. You will then need to enter the destination number for the SMS message. This is the phone number on the SIM card used by the M20 Terminal[4].

M20 Terminal initiated SMS Message

Send a PDU SMS

In PDU mode, to send a message like the word �hello�, initially, you have to convert it to a PDU format message. Refer to section 3 (Parameter description) for details on how to construct the PDU message. Note that the actual length of the PDU string (without the Service Centre Address) must be specified for all SMS. Follow the steps below for sending the SMS message.

Step 1. Enter the actual length of the SMS message in octets[5]

AT+CMGS=18[6]

Step 2. Enter the SMS message in PDU format and terminate it with �CTRL Z�

>0011000A81409178699100000105E8329BFD06[CTRL Z]

The M20 Terminal should return

+CMGS: 12
OK

where 12 is the message reference MR, which is different for every SMS message sent.

Send a text SMS

In text mode, to send a message, eg. �hello�, follow the three steps below.

Step 1: Set the M20 Terminal for text SMS using

AT+CMGF=1[ENTER]

Step 2: Enter the destination phone number in international format[7]

AT+CMGS=�+61419879619�[ENTER]

Step 3: Enter the text message and terminate it with �CTRL Z�

>hello[CTRL Z]

The M20 Terminal should return

+CMGS: 1
OK

where 1 is the message reference MR, which is different for every SMS message sent.

Receiving/Reading/Deleting a SMS Message

Mobile Phone

When there is a new SMS message arrived, the phone will beep and the SMS message indicator will appear on the phone screen.

To read the SMS message, select [Read Messages] from the [Mail] menu using the left or right arrow button and the new message is usually shown first. Press the �YES� button to read the message. The message can be deleted using the �CLR� button.

M20 Terminal

Read a PDU SMS

In PDU mode, when the M20 Terminal receives a SMS message, the following message will appear on the PC screen.

  +CMTI: �SM�, 1

where 1 is the memory location in which the message can be read from.

To read a SMS message from a particular location in memory (eg. location 1) use the AT+CGMR command as follow.

AT+CMGR=1[ENTER]

The M20 Terminal should return the PDU message as follow.

+CMGR: 0,,24
07911614786007F0040B911604994743F400009930139100406B05E8329BFD06
OK

where 0 is the status code indicating a received and already read message, 24 is the hexadecimal number indicating the length of the message.

Read a text SMS

Like PDU mode, when the M20 Terminal receives a SMS message, the following message will appear on the PC screen.

+CMTI: �SM�, 1

where 1 is the memory location in which the message can be read from.

To read the SMS message use the AT+CGMR command as follow.

AT+CMGR=1[ENTER]

The M20 Terminal should return the text message as follow.

+CMGR: �REC READ�,�+61407809050�,�98/12/01,20:16:11+44�
hello
OK

Delete a SMS message

The SMS message can be deleted from memory (eg. location 1) using the AT+CMGD command as follow. Note that there is no AT command to delete all the SMS messages at once.

AT+CMGD=1[ENTER]

The M20 Terminal should return OK.


  1. Sometimes the abbreviation SC (Service Centre) means the same as SMSC.
  2. PDU mode is the default setting for the M20 Terminal.
  3. To be able to read the SMS message directly in text format, ensure that the M20 Terminal has been set to text mode.
  4. The phone number can be entered as a national number or an international number (+61�).
  5. One octet contains two BCD-digit fields, eg. 11, 00, or 0A etc.
  6. 18 is the length of the PDU message in octets, as shown in step 2.
  7. The phone number can be entered in either national or international format with or without the �+� sign at the front.