There is a need to support narrowband TDD frame structure for narrowband communications. The present disclosure provides a solution by supporting one or more narrowband TDD frame structure(s) for narrowband communications. In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. In one aspect, the apparatus may receive information associated with a narrowband TDD frame structure. The apparatus may also transmit an uplink transmission a predetermined number of times using a first scrambling sequence. In one aspect, the first scrambling sequence may be determined using a first number of least significant bits (LSBs) associated with a first radio frame. In another aspect, the first number of LSBs may be larger than a second number of LSBs used in a second scrambling sequence associated with a narrowband frequency-division duplex (FDD) uplink transmission.