Methods, systems, and devices for wireless communication are described. A method may include identifying a reference number of tones for an overhead channel of a transport block and segmenting the transport block into a code block based at least in part on the reference number of tones for the overhead channel. In some examples, a code block indicator or the reference number of tones may be transmitted on a control channel. Another method may include receiving a code block size indicator associated with a code block of a transport block, decoding the code block based at least in part on the code block size indicator and assembling the transport block based at least in part on the decoded code block. In some examples, the code block size indicator may be received using a control channel.