Online PDU Encoder and Decoder

Posted August 8th, 2007 by thoughtworks

SMS (Short Message Service) is specified by the ETSI (standards GSM 03.40₁ and 03.38₂ ). It can contain up to 160 characters, where each character is written according to the 7-bits GSM default alphabet.[ 7 bits default table ]

SMS also contains some meta-data, e.g.

• 1. Info about the senders ( Service center number, sender number)

  2. Protocol information (Protocol identifier, Data coding scheme)

  3. Timestamp

There are 2 ways to receive and send SMS messages _a, PDU (protocol discription unit) and Text mode. In this document we focus on PDU mode.

PDU format can be used on any encoding.

As an example:

07911326040000F0040B911346610089F600002080629 17314080CC8F71D14969741F977FD07

The above PDU string contains the message "How are you?" and was read from a Siemens C35i mobile phone.The string is built from hexadecimal-octets and semi decimal-octets. As mentioned, SMS contains metadata about itself.

We explain it using the example above:

PDU Encoder and Decoder