How Does USSD Function?
USSD (Unstructured Supplementary Service Data) is a communication protocol that enables the transmission of small data packages without the need for a data connection or incurring SMS costs. It is commonly used for sending concise requests and commands, with a maximum limit of 182 characters (16 bits of data). USSD, however, does not support multimedia content such as audio, video, or images. USSD messages, unlike SMS, are exclusively exchanged between network entities such as the Home Location Register (HLR), Mobile Switching Center (MSC), Short Message Service Center (SMSC), or dedicated USSD applications. On the receiving end, these messages can be directed to mobile phones, applications, or IoT devices.
Real-Time Communication and Instant MessagingWhile SMS messages pass through an SMSC for storage and forwarding, USSD transmissions take a different approach. They utilize a USSD gateway, establishing an open session between the network entities involved. This allows for real-time communication and the provision of instant messaging services.
USSD Message FormatUSSD messages consistently start with an asterisk, followed by digits, and conclude with the pound sign. The numbers represent codes employed by the network to establish connections with specific entities. Different Mobile Network Operators (MNOs) utilize their own unique codes. USSD Service Code: 123# User Input: 1 Session Identifier: 12345678 Response Message: