Throughput is a term used to describe how many messages can be sent per second. For example, a throughput of 10 messages per second suggests an SMS account can submit (and receive an acknowledgement) for up to 10 SMS messages per second. Typically, throughput is limited by account service or by bind. You can increase message throughput by ensuring the SMPP/UCP client software you use is set to allow up to 10 pending operations. This is also called the asynchronous window. You can also increase your message throughput by using two separate BINDs for transmission.
