Improved re-transmission capability in semi-persistent transmission

One or more hybrid automatic repeat request process identifications are configured for scheduling without associated control signaling. A particular HARQ process ID to be assumed for a given subframe is determined based on at least one of: a) system frame number; b) number of hybrid automatic repeat request processes that are allocated for semi-persistent scheduling; and c) periodicity for semi-persistent scheduling. In various embodiments: a) is broadcast and b) and c) are sent via RRC signaling; and the assumed particular HARQ process ID is determined as a function of [Current TTI/SP_Period] mod Num_SP_HARQ:wherein Current TTI is a number for the given subframe derived from the system frame number and the term [Current TTI/SP_Period] is rounded to an integer prior to the modulo operation; SP_Period is the periodicity of the semi-persistent scheduling; and Num_SP_HARQ is the number of hybrid automatic repeat request processes that are allocated for semi-persistent scheduling.