Network Reference - SMS
Short Messaging Service or SMS is a mechanism to deliver short data messages over the Iridium satellite network. Iridium SMS service incorporates a subset of the GSM SMS features. Each SMS message can be up to 160 text characters (7-bit coded) in length. The text characters are based on a 7-bit alphabet, which is encoded and transmitted as 8-bit data, hence the 140 octet (byte) maximum message size. Non-text based SMS (for example binary format) are also possible.
SMS service is a store and forward method of transmitting messages to and from a mobile device. The short message from the originator is stored in a central Short Message Center (SMSC) which then forwards it to the destination. In the case that the recipient is not available, the SMSC will attempt to deliver the SMS until it is delivered or the validity period expires. SMS supports a limited confirmation of message delivery. The sender of the short message can request to receive a return message notifying them whether the short message has been delivered or not. With this option, the originator gets a confirmation that the message was delivered to the SMSC. Unlike standard GSM, the Iridium SMS can only acknowledge that the message was delivered to the SMSC and not the end-destination.
SMS messages can be sent and received simultaneously on an ISU while a voice call is in progress. This is possible because SMS messages travel over and above the radio channel using the signaling path, whereas the voice call uses a dedicated "traffic" radio channel for the duration of the call.
SMS is capable of both Mobile Origination (MO-SMS) and Mobile Termination (MT-SMS). There are numerous GSM-SMS applications developed for terrestrial GSM networks. It is possible to adapt existing terrestrial based applications and also develop new applications using the Iridium SMS service. The Iridium SMS service offers the following capabilities:
- Two-way global text messaging
- Send to and receive from other ISU
- Send to and receive from e-mail addresses. Iridium subscribers are able to receive SMS messages via <MSISDN>@msg.iridium.com, where <MSISDN> is the Iridium phone number.
- Send to and receive from cellular subscribers
- Messages will be stored until delivered up to 8 days