International roaming is one of the many essential services a carrier enables on its customer's subscriber identity module (SIM) cards that allows its users to send and receive calls, messages, and e-mails whenever they travel to another country. From its beginnings in voice roaming in the last 1.5 decades up to today, international roaming has been a pivotal contributor to the sales of telecommunications carriers. It does however come at a high cost, which the users end up paying, due to

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... us factors such as roaming agreements between home carriers and visited carriers as well as clearinghouses needed by companies to settle disputes in agreements between the carriers involved. This paper proposes a consortium blockchain approach coupled with smart contract application. The decentralized nature of a blockchain and the automation that smart contracts provide solves two of international roaming problems-intermediaries and high cost. Together with Tendermint-a consensus mechanism that requires no mining, implementation of the consortium blockchain can be done involving all carriers around the world with them being the privileged users and verify the transactions of two engaging carriers. With this setup, the blockchain is privatized yet still able to perform the essential functions of a blockchain, which are immutability, security, and transparency of data. The proposal can eliminate the need for continually changing roaming agreements and clearing houses that increase the price for the users as well as slow down the processing time making international roaming services much more efficient, user-friendly and cost-effective for both its consumers and carriers.