OTA (Over-The-Air) is a wireless technology used to:

  • communicate with a SIM card, 
  • download applications to a SIM card, 
  • and manage a SIM card 

without being connected physically to the card.

what is ota

In other words: Over-The-Air (OTA) is a technology that updates and changes data in the SIM card without having to reissue it.It is also referred to as Over-the-Air provisioning.It's both crucial for subscribers and carriers.

How does Over-The-Air work?

OTA enables a Network Operator to introduce new SIM services or to remotely modify the contents of SIM cards, already in the field, rapidly and cost-effectively.

OTA is based on client/server architecture where at one end there is an operator back-end system (customer care, billing system, application server ... ) and at the other end, there is a SIM card.

The operator's back-end system sends service requests to an OTA Gateway (or OTA Platform) which transforms the requests into Short Messages and forwards them onto a Short Message Service Centre (SMSC) which transmits them to one or several SIM cards in the field.

The end-user can receive individual messages from the operator, download or activate new services on his telephone, and much more..., without having to return to a retail outlet.

The OTA architecture: 6 components

To implement OTA technology, the following components are needed:

  • A back end system to send requests
  • An OTA Gateway to process the requests in an understandable format to the SIM card
  • An SMSC to send requests through the wireless network
  • A bearer to transport the request: today it is the SMS bearer.
  • Mobile equipment to receive the request and transmit it to the SIM card
  • A SIM card to receive and execute the request

 Back-end System

The back end system can be anything from a customer care operator to a billing system, a content provider or a subscriber web interface. 

The provisioning system has to be connected to the mobile network (either per LAN or via the Internet). Service requests contain the service requested (activate, deactivate, load, modify ...), the subscriber targeted, and the data to perform the service. 

The back-end system then sends out service requests to the OTA gateway.

OTA Gateway

The OTA Gateway receives Service-Requests through a Gateway API that will indicate the actual card to modify/update/activate. In fact, inside the OTA Gateway, there is a card database that shows for each card, the SIM vendor (e.g. Thales, etc.), the card's identification number, the IMSI and the MSISDN.

The second step is to format the service request into a message that can be understood by the recipient SIM card. To achieve this, the OTA Gateway has a set of libraries that contain the formats to use for each brand of SIM cards. The OTA Gateway then formats the message differently depending on the recipient card.

The third step consists of sending a formatted message to the SMSC using the right set of parameters as described in GSM 03.48. Then the OTA Gateway issues as many SMS as required to fulfil the Service-Request. In this step, the OTA Gateway is also responsible for the integrity and security of the process.


Services centre for short messages (SMS) exchanged between the management system of these messages (OTA Gateway) and the cellular network. A message consisting of a maximum of 160 alphanumeric characters can be sent to or from a Mobile Phone. If the Mobile Phone is powered off or has left the coverage area, the message is stored and offered back to the subscriber when the mobile is powered on or has reentered the coverage area of the network.

SMS Channel

The communication between the SIM card or eSIM) and the OTA Gateway can be done by SMS exchange and in this case, named the SMS channel.

Mobile phone

Has to be phase 2+ in the GSM standard. Mobile Phone has all the required features for handling a part or all of standardized GSM services. Regarding OTA services, the Mobile Phone has to be Sim Tool Kit compliant.

SIM card

Smart card provides secure user authentication and is mainly used in GSM standard as a Subscriber Identification Module (SIM cards). The SIM is the major component of the GSM market, paving the way to value-added services. 

SIM cards now offer new menus, prerecorded numbers for speed dialling, and the ability to send pre-formatted short messages (SMS) to query a database or secure transactions.

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