Methods and apparatus are provided for transmission preemption and its indication. In one novel aspect, the UE receives a downlink resource assignment and determines whether an ultra-low latency (ULL) alert signal exists, wherein the ULL alert signal indicates a set of soft bits are overridden. The UE discards the set of soft bits from the overridden resources upon determining the ULL alert signal exists. In one embodiment, the ULL alert signal resides in the assignment subframe, and the overridden soft bits are in the assignment subframe. The alert timing for the ULL alert signal is preconfigured. In another embodiment, the ULL alert signal resides in a subframe that is right after the assignment subframe. The alert signal is enabled through an enabling of an enhanced mobile broadband and ULL service. The alter signal indicates a superset of the overridden soft bits or part of the overridden soft bits.