HARQ is synchronous in the UL. Whenever, a re-transmission occurs in UL, it can be either Adaptive and Non-adaptive
a. triggered when NDI bit is not toggled relative to the previous transmission. This information should be present in the PDCCH DCI0.
b. MCS and RB's may change as per resources allocated by the eNB on PDCCH DCI0 transmission
a. trigerred when NACK is received on PHICH
b. use same resources as per the previous transmission i.e. MCS and RB's remains unchanged