Categories of UE in LTE is divided by its function which is as per below.
Functionality:
eNB obtains the UE radio capabilities via:
• The S1AP initial setup request message
• The X2AP in case of handover
• The RRC in any other cases
eNB sends the UE radio capabilities to:
• The MME if it has been retrieved from RRC signaling
• The neighbor eNB in case of handover
UE category determines:
• MIMO settings
• PRB allocation and AMC limitation (e.g. 64QAM in UL)
• ROHC (Robust Header Compression) profile
• Inter RAT handover support
• All categories support 20 MHz
• 64QAM mandatory in downlink, but not in uplink (except Class 5)
• 2×2 MIMO mandatory in other classes except Class 1
