The default GSM Alphabet character set (DGSM), as per the GSM338 standards document, supports only a limited set of characters because it is 7-bit encoded.
If you want to send other characters you will need to encode messages in UCS2, which is 16-bit encoded and allows you to send messages using a variety of characters sets, such as, Chinese, Arabic, Russian and accented characters not present in DGSM.
If Content Providers (CPs) don’t know how to encode messages in UCS2 they should use the Digital Interconnect UTF8interface (HTTP only). They will need to encode a message written from an operating system in UTF8 in Base64 to force the UTF8 encoding - and submit messages to our platform. The A2P platform will check if any character is outside of the DGCS and if there is at least one, then the system will encode the message in UCS2.
Because UCS2 is using 2 bytes and because an SMS is 140 bytes UCS2 messages have a maximum of 70 characters. CPs will need to control the message length or they can use the SplitText parameter and concatenated messages will be generated if the message length > 140 bytes.
For Latin alphabet languages the normal usage for CPs is NOT to use characters outside of DGCS. End-users are usually used to receive messages with missing accents.