The following relates generally to wireless communication, and more specifically to feedback-based retransmission using mixed-duration transmission time intervals. 
Wireless multiple-access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level.  An example telecommunication standard is Long Term Evolution (LTE).  LTE is designed to improve spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards.  LTE may use orthogonal frequency division multiple access (OFDMA) on the downlink, single-carrier frequency division multiple access (SC-FDMA) on the uplink, and multiple-input multiple-output (MIMO) antenna technology. 
In some examples, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs).  In a LTE or LTE-Advanced (LTE-A) network, a set of one or more base stations may define an eNodeB (eNB).  In other examples (e.g., in a new radio (NR) or 5G network), a wireless multiple access communication system may include a number of smart radio heads (RHs) in communication with a number of access node controllers (ANCs), where a set of one or more RHs, in communication with an ANC, defines a base station (e.g., an eNB or gNB).  A base station may communicate with a set of UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station). 
A base station in some LTE or NR deployments may transmit to one or more UEs using different length transmission time intervals (TTIs) that may be selected based on a service that is being provided.  In some examples, a reduced length TTI may support some low latency wireless services that provide low latency with high reliability for wireless transmissions of the low latency services.  Reduced length TTIs may be a subset of a longer TTI such as a slot-TTI, and in some cases, low latency services using reduced length TTIs may puncture other services that may have longer TTIs.  Such puncturing may result in portions of transmissions of the longer TTI service not being received at the receiver of the transmission.