Uplink is much slower.

Because of the mobile size - battery life

Physical Channels

PUSCH (Physical Uplink Shared Channel): Carries the uplink data from user devices to the network.​

PUCCH (Physical Uplink Control Channel): Carries HARQ acknowledgement and channel state information. It also carries request for uplink grant. Also, Uplink Control Information (UCI) is carried by PUCCH​