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First octet of the SMS-DELIVER PDU

Louis — Thu, 09 Nov 2006 02:12:14 +0000

First octet of the SMS-DELIVER PDU

The first octet of the SMS-DELIVER PDU has the following layout:

Bit no	7	6	5	4	3	2	1	0
Name	TP-RP	TP-UDHI	TP-SRI	(unused)	(unused)	TP-MMS	TP-MTI	TP-MTI

where the fields have the following meaning:

Name	Meaning
TP-RP	Reply path. Parameter indicating that reply path exists.
TP-UDHI	User data header indicator. This bit is set to 1 if the User Data field starts with a header
TP-SRI	Status report indication. This bit is set to 1 if a status report is going to be returned to the SME
TP-MMS	More messages to send. This bit is set to 0 if there are more messages to send
TP-MTI	Message type indicator. Bits no 1 and 0 are both set to 0 to indicate that this PDU is an SMS-DELIVER

Example

A first octet of “04″ (hex) has the following meaning:

Bit no	7	6	5	4	3	2	1	0
Name	TP-RP	TP-UDHI	TP-SRI	(unused)	(unused)	TP-MMS	TP-MTI	TP-MTI
Value	0	0	0	0	0	1	0	0

AT commands interface

Louis — Thu, 09 Nov 2006 02:08:29 +0000

The following link is AT commands interface document v90

This document describes the messages exchanged between an external application module and the WAVECOM GSM mobile station, based on AT commands in order to control incoming and outgoing calls.

This document presents the AT-commands implemented for the voice call teleservice, the data teleservice and the short message teleservice.

AT v90 Commands Interface

The Type-of-Address octet

Louis — Thu, 09 Nov 2006 02:00:06 +0000

The Type-of-Address octet

The Type-of-Address octet indicates the format of a phone number. The most common value of this octet is 91 hex (10010001 bin), which indicates international format. A phone number in international format looks like 46708251358 (where the country code is 46). In the national (or unknown) format the same phone number would look like 0708251358. The international format is the most generic, and it has to be accepted also when the message is destined to a recipient in the same country as the MSC or as the SGSN.

Bit no	7	6	5	4	3	2	1	0
Name	Always set to 1	Type-of-number			Numbering Plan Identification

Note that bit no 7 should always be set to 1
Bits 6, 5 and 4 deonte the Type-of-number
Bits 3, 2, 1, 0 denote the Numbering-Plan-Identification

Type of number

Bits 6 5 4	Meaning of the Type-of-number bits (6, 5 and 4)
0 0 0	Unknown. This is used when the user or network has no a priori information about the numbering plan. In this case, the Address-Value field is organized according to the network dialling plan, e.g. prefix or escape digits might be present.
0 0 1	International number.
0 1 0	National number. Prefix or escape digits shall not be included.
0 1 1	Network specific number. This is used to indicate administration/service number specific to the serving network, e.g. used to access an operator.
1 0 0	Subscriber number. This is used when a specific short number representation is stored in one or more SCs as part of a higher layer application. (Note that “Subscriber number” shall only be used in connection with the proper PID referring to this application).
1 0 1	Alphanumeric, (coded according to GSM TS 03.38 7-bit default alphabet)
1 1 0	Abbreviated number
1 1 1	Reserved for extension

Numbering Plan Identification

The Numbering-plan-identification applies for Type-of-number = 000, 001 and 010. For Type-of-number = 101 bits 3,2,1,0 are reserved and shall be transmitted as 0000. Note that for addressing any of the entities SC, MSC, SGSN or MS, Numbering-plan-identification = 0001 will always be used. However, for addressing the SME, any specified Numbering-plan-identification value may be used.

Bits 3 2 1 0	Meaning of the Numbering Plan Identifiation bits (3, 2, 1 and 0)
0 0 0 0	Unknown.
0 0 0 1	ISDN/telephone numbering plan (E.164/E.163).
0 0 1 1	Data numbering plan (X.121).
0 1 0 0	Telex numbering plan
1 0 0 0	National numbering plan
1 0 0 1	Private numbering plan
1 0 1 0	ERMES numbering plan (ETSI DE/PS 3 01-3)
1 1 1 1	Reserved for extension

All other values are reserved.

Example

A Type-of-Address octet of “81″ (hex), unknown phone number format, looks like:

Bit no	7	6	5	4	3	2	1	0
Name	Always set to 1	Type of number			Numbering plan identification
Value	1	0	0	0	0	0	0	1

SMS and the PDU format

Louis — Thu, 09 Nov 2006 01:58:07 +0000

SMS and the PDU format

Introduction

The SMS message, as specified by the Etsi organization (documents GSM 03.40 and GSM 03.38), can be up to 160 characters long, where each character is 7 bits according to the 7-bit default alphabet. Eight-bit messages (max 140 characters) are usually not viewable by the phones as text messages; instead they are used for data in e.g. smart messaging (images and ringing tones) and OTA provisioning of WAP settings. 16-bit messages (max 70 characters) are used for Unicode (UCS2) text messages, viewable by most phones. A 16-bit text message of class 0 will on some phones appear as a Flash SMS (aka blinking SMS or alert SMS).

The PDU format

There are two ways of sending and receiving SMS messages: by text mode and by PDU (protocol description unit) mode. The text mode (unavailable on some phones) is just an encoding of the bit stream represented by the PDU mode. Alphabets may differ and there are several encoding alternatives when displaying an SMS message. The most common options are “PCCP437″, “PCDN”, “8859-1″, “IRA” and “GSM”. These are all set by the at-command AT+CSCS, when you read the message in a computer application. If you read the message on your phone, the phone will choose a proper encoding. An application capable of reading incoming SMS messages, can thus use text mode or PDU mode. If text mode is used, the application is bound to (or limited by) the set of preset encoding options. In some cases, that’s just not good enough. If PDU mode is used, any encoding can be implemented.

Receiving a message in the PDU mode

The PDU string contains not only the message, but also a lot of meta-information about the sender, his SMS service center, the time stamp etc. It is all in the form of hexa-decimal octets or decimal semi-octets. The following string is what I received on a Nokia 6110 when sending the message containing “hellohello” from www.mtn.co.za.

917283010010F5

040BC87238880900F10000993092516195800AE8329BFD4697D9EC37

This octet sequence consists of three parts: An initial octet indicating the length of the SMSC information (“07″), the SMSC information itself (“917283010010F5″), and the SMS_DELIVER part (specified by ETSI in GSM 03.40).

Note: on some phones (e.g. Ericssson 888?) the first three (colored) parts are omitted when showing the message in PDU mode!

Octet(s)	Description
07	Length of the SMSC information (in this case 7 octets)
91	Type-of-address of the SMSC. (91 means international format of the phone number)
72 83 01 00 10 F5	Service center number(in decimal semi-octets). The length of the phone number is odd (11), so a trailing F has been added to form proper octets. The phone number of this service center is “+27381000015″. See below.
04	First octet of this SMS-DELIVER message.
0B	Address-Length. Length of the sender number (0B hex = 11 dec)
C8	Type-of-address of the sender number
72 38 88 09 00 F1	Sender number (decimal semi-octets), with a trailing F
00	TP-PID. Protocol identifier.
00	TP-DCS Data coding scheme
99 30 92 51 61 95 80	TP-SCTS. Time stamp (semi-octets)
0A	TP-UDL. User data length, length of message. The TP-DCS field indicated 7-bit data, so the length here is the number of septets (10). If the TP-DCS field were set to indicate 8-bit data or Unicode, the length would be the number of octets (9).
E8329BFD4697D9EC37	TP-UD. Message “hellohello” , 8-bit octets representing 7-bit data.
Octet(s)	Description
00	Length of SMSC information. Here the length is 0, which means that the SMSC stored in the phone should be used. Note: This octet is optional. On some phones this octet should be omitted! (Using the SMSC stored in phone is thus implicit)
11	First octet of the SMS-SUBMIT message.
00	TP-Message-Reference. The “00″ value here lets the phone set the message reference number itself.
0B	Address-Length. Length of phone number (11)
91	Type-of-Address. (91 indicates international format of the phone number).
6407281553F8	The phone number in semi octets (46708251358). The length of the phone number is odd (11), therefore a trailing F has been added, as if the phone number were “46708251358F”. Using the unknown format (i.e. the Type-of-Address 81 instead of 91) would yield the phone number octet sequence 7080523185 (0708251358). Note that this has the length 10 (A), which is even.
00	TP-PID. Protocol identifier
00	TP-DCS. Data coding scheme.This message is coded according to the 7bit default alphabet. Having “04″ instead of “00″ here, would indicate that the TP-User-Data field of this message should be interpreted as 8bit rather than 7bit (used in e.g. smart messaging, OTA provisioning etc).
AA	TP-Validity-Period. “AA” means 4 days. Note: This octet is optional, see bits 4 and 3 of the first octet
0A	TP-User-Data-Length. Length of message. The TP-DCS field indicated 7-bit data, so the length here is the number of septets (10). If the TP-DCS field were set to 8-bit data or Unicode, the length would be the number of octets.
E8329BFD4697D9EC37	TP-User-Data. These octets represent the message “hellohello”. How to do the transformation from 7bit septets into octets is shown here

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