Why LTE use frequency hopping only for Uplink?

Question

Actually there are three resource allocation types being used to allocate resources to UE(s) in downlink and uplink. For downlink all three (Type 0, 1 and 2) used but for uplink only resource allocation type 2 is being used.

Answer 1

Because SC-FDMA is used in uplink requiring contiguous RB allocation for a single UE, intra and inter-subframe frequency hopping can be applied to mitigate the impact of interference on specific sub-band(s). In DL, RB allocation can be done from across the band for a single UE, therefore no need for frequency hopping.