SMS Technology

SMS Technology - Reference for Developers

The Short Message Service (SMS) allows text messages to be sent and received to and from mobile telephones. The text can comprise words or numbers or an alphanumeric combination. SMS was created as part of the GSM Phase 1 standard. The first short message is believed to have been sent in December 1992 from a PC to a mobile phone on the Vodafone GSM network in the UK. Each short message is up to 160 characters in length when Latin alphabets are used, and 70 characters in length when non-Latin alphabets such as Arabic and Chinese are used.

SMS is essentially similar to paging, but SMS messages do not require the mobile phone to be active and within range, as they will be held for a number of days until the phone is active and within range. SMS messages are transmitted within the same cell or to anyone with roaming capability. They can also be sent to digital phones from a web site equipped with a PC Link or from one digital phone to another. An SMS gateway is a web site that lets you enter an SMS message to someone within the cell served by that gateway or acts as an international gateway for users with roaming capability.

The SMS is a store and forward service. In other words, short messages are not sent directly from sender to recipient, but via an SMS Center. Each mobile telephone network that supports SMS has one or more messaging centers to handle and manage the short messages.

Validity Period of an SMS Message

An SMS message is stored temporarily in the SMS center if the recipient mobile phone is offline. It is possible to specify the period after which the SMS message will be deleted from the SMS center so that the SMS message will not be forwarded to the recipient mobile phone when it becomes online. This period is called the validity period.

Message Status Reports

Sometimes you may want to know whether an SMS message has reached the recipient mobile phone successfully. To get this information, you need to set a flag in the SMS message to notify the SMS center that you want a status report about the delivery of this SMS message. The status report is sent to you in the form of an SMS message.

Message Submission Reports

After leaving the mobile phone, an SMS message goes to the SMS center. When it reaches the SMS center, the SMS center will send back a message submission report to the mobile phone to inform whether there are any errors or failures (e.g. incorrect SMS message format, busy SMS center, etc). If there is no error or failure, the SMS center sends back a positive submission report to the mobile phone. Otherwise it sends back a negative submission report to the mobile phone. The mobile phone may then notify the user that the message submission was failed and what caused the failure.

Message Delivery Reports

After receiving an SMS message, the recipient mobile phone will send back a message delivery report to the SMS center to inform whether there are any errors or failures (example causes: unsupported SMS message format, not enough storage space, etc). This process is transparent to the mobile user. If there is no error or failure, the recipient mobile phone sends back a positive delivery report to the SMS center. Otherwise it sends back a negative delivery report to the SMS center.


What is SMSC (SMS Center) ?

An SMS center (SMSC) is responsible for handling the SMS operations of a wireless network. When an SMS message is sent from a mobile phone, it will reach an SMS center first. The SMS center then forwards the SMS message towards the destination. An SMS message may need to pass through more than one network entity (e.g. SMSC and SMS gateway) before reaching the destination. The main duty of an SMSC is to route SMS messages and regulate the process. If the recipient is unavailable (for example, when the mobile phone is switched off), the SMSC will store the SMS message. It will forward the SMS message when the recipient is available.


What is sms Gateways?

One problem of SMS messaging is that SMSCs developed by different companies use their own communication protocol and most of these protocols are proprietary. For example, Nokia has an SMSC protocol called CIMD whereas another SMSC vendor, CMG, has an SMSC protocol called EMI. We cannot connect two SMSCs if they do not support a common SMSC protocol. To deal with this problem, an SMS gateway is placed between two SMSCs. The SMS gateway acts as a relay between the two SMSCs. It translates one SMSC protocol to another one. This way can be used by two different wireless carriers to interconnect their SMSCs for purposes such as enabling the exchange of inter-operator SMS messages.Besides wireless carriers, content providers and SMS application developers may also find an SMS gateway useful.



SMPP

The Short Message Peer to Peer (SMPP) protocol is an open industry standard messaging protocol designed to simplify integration of data applications with wireless mobile networks such as GSM, TDMA, CDMA and PDC. The protocol is widely deployed in the mobile telecommunications industry.The protocol is most widely known for its use in text messaging between cellular phones. It is also frequently used to permit third parties (for example, value added service providers such as news organizations) to pass messages, usually in bulk.


SMS MT

Mobile Terminated SMS (MT) also known as Bulk SMS or Push SMS enables the delivery of messages from a mobile business application to a mobile subscriber's handset.


SMS MO

Mobile Originated SMS / Inbound SMS , Receiving Messages originated from cellphones to an application. Also the same can be sent to some users. Basically used for customer interaction.