SMS Elements

Short message service comprised of seven elements which helps Service Center in receiving and sending Short messages in accordance with the standards. These are common set of standards agreed by the mobile phone manufacturers and the same set of standards are used by the Service centers as well. Any equipment other than a mobile phone such as a GSM modem should adhear to these standards if they want to send SMS.

Following is a list of those elements

Validity-Period;

Service-Centre-Time-Stamp;

Protocol-Identifier;

More-Messages-to-Send;

Priority;

Messages-Waiting;

Alert-SC

Validity period

Validity period is the element which is decided by the Short Messaging entity and inserted in the SMS-SUBMIT which is to be sent to the Short Message Service Center (SMSC). This value let SMSC decide how long the message should be kept on retrying to send to the intended receipient if not delivered. If SMSC has a default validiy period less than the value specified by the SME, then the parameter "Tp-Validity-Period" is overwritten to avoid the infinity waiting of message in SC.

Service center time stamp

Time stamp is the service element which is inserted by the SMSC in the SMS-Deliver message which is sent to the receipient. It gives an idea to the receiver the arrival time of the message to the SMSC. The parameter "TP-Service-Centre-Time-Stamp"should also be adjusted in accordance with the receivers time zone difference and a count which is of 15 minutes intervals is used for this.

E.g. GTA +5.30= 330 minutes, 330/15=22, so GTA +5.30 is indicated by the code 22.

Protocol identifier

Protocol identifier is the element in which the protocol used by a higher layer is identified at transfer layer. It includes in all of the following message types. SMS-SUBMIT, SMS-SUBMIT-REPORT for RP-ACK, SMS-DELIVER DELIVER, SMS-DELIVER-REPORT for RP-ACK, SMS_STATUS_REPORT and SMS-COMMAND TP-Protocol-Identifier (TP-PID).

More messages to send

This is the parmeter used in SMS-DELIVER to indicate the Mobile Station by the Service Center that there are more messages waiting in the SC to be sent to the MS. TP-More-Messages-to-Send (TP-MMS) is the paramer name and this is a boolen value which indicates the true/ false situation of the more messages are there or not. If not --> 0 and if yes --> 1.

Priority

Priority is the paramer entered by the Sc or the MS to indicate the priority of delivering the message. A message is not attempted continuously to send if it is not an priority SM. If a non priority SM doesn't get delivered due to the absense of the mobile station, it is informed to the HLR asking to notify SC once the MS become available. But for priority SMs it is being continuously attempted to send the message by the SC itself.

Message waiting

In the above explined delvery procedure of non priority messages, HLR neeeded to be informed that there is a message waiting in the SMSC to be sent to a particular reciepient. The service element used for this task is Messages-Waiting-Indication (MWI) and it comprises of Messages-Waiting-Data (MWD), the Mobile-station-Not-Reachable-for-GPRS (MNRG), the Mobile-Station-Not-Reachable-Flag (MNRF), the Mobile-Not-Reachable-Reason (MNRR) and the Mobile-Station-Memory-Capacity-Exceeded-Flag (MCEF) located in the HLR; the Mobile-station-Not Reachable-for-

GPRS (MNRG) located in the SGSN, and the Mobile-Station-Not-Reachable-Flag (MNRF) located in the VLR.

Alert SC

Alert SC is the element used by HLR to inform SC that the availability of the mobkile stations which were unavailble before due to:

1. Delivery attempt has failed because the MS is not reachable or because the MS memory capacity was exceeded; and

2. Not recognized by the PLMN:

a) to have resumed operation (e.g. to have responded to a paging request); or

b) to have memory newly available (which implies that the mobile is reachable).