Systems, procedures, and instrumentalities are disclosed for transmissions with polar codes. A transmitting entity may determine a mother code length. The mother code length may be based on value(s), e.g., a maximum number of transmissions. The transmitting entity may determine a number of information bits to be polar encoded. The number of information bits may be larger than a number of payload bits. The transmitting entity may map the number of information bits to a number of bit channels of a polar code. The transmitting entity may polar encode the information bits in the bit channels using the determined mother code length. The transmitting entity may partition the polar encoded bits into a number of parts. The number of parts may be based on one or more values, e.g., the maximum number of transmissions. The transmitting entity may transmit bits that have been interleaved to a circular buffer.