Methods, systems, and devices are described for operating a communications system using both licensed and unlicensed frequency bands. Unlicensed spectrum may be used as a primary band for transmitting data packets and TCP may be implemented for selectively transmitting (e.g., retransmitting) a subset of the transmitted data packets via licensed spectrum. Selective transmission of the subset of data packets via licensed spectrum may be based on a transmitter failing to receive and acknowledgment (ACK) message in response to one or more transmitted data packets on the unlicensed spectrum. Selective retransmission may be based on a transmitter detecting interference and/or it may be based on a receiver reporting information about channel conditions. In some cases, a transmitter may simultaneously receive channel condition information for both licensed and unlicensed spectrum. In other cases, unlicensed spectrum may be utilized for data packet transmission and licensed spectrum may be utilized for ACK messages.