Hi,
we can say two matrices for load balancing , like no of UE and resource available at ENB. Each ENB will have some limitation in supporting no of UE (spec says each can serve upto 65535 based on 2byte RNTI) based on the PHY capability and limitation of resource based on UE activity. so if any of these exceeding the threshold value which is configured by OEM then load balancing is required.