USSD service is mostly like SMS service. Read below to understand more:
A message is always first sent to short message service center (SMSC) before message get deliver to the recipient. The sender receives a deliver confirmation once message was successfully received by SMSC. Message is not guaranteed to reach the destination user instantly.
Let’s take an example of balance enquiry to understand this clearly:
General telecom flow of USSD service is as below:
USSD gateway is a GSM node that enables communication between users and USSD applications across the network. It enables communication between USSD applications and other network nodes like HLR, VLR and MSC.
USSD gateway and applications also generate log files to track sessions and also used in troubleshooting.
USSD gateway generates CDR at the end of every transaction.
Alarms are also generated for USSD gateway and USSD application. Alarms are sent to users via SMS/email.