LTE ARQ and HARQ techniques for reliable data transmissions
HARQ is Hybrid Automatic Repeat Request. Its an enhancement over Layer 2 ARQ protocol. These techniques are used to transfer data packets reliably over radio link. Lets discuss details for 4G LTE standard.
In LTE there is a signal quality threshold limit. When the signal quality is above that limit, HARQ is used to correct Received Packets. When signal quality goes below that threshold the L2 software automatically replaces HARQ with plain ARQ technique.
LTE ARQ technique -