 Layer late, it returns a message indicating the lateness in us and the transmit offset can be adjusted for next transmission. The nFAPI delay management mechanism can be used to establish the timing reference differences between the VNF and PNF. It can also, optionally, be used by the VNF to instruct the PHY instance to update its slot number based on the offset defined by the VNF. Network monitor mode API Well-described in, Self-Organizing Networks (SON) are introduced to reduce operator Capital Expene (CAPEX) and Operational Expense (OPEX) in deployed 3GPP networks like LTE and 5G. This is driven by the increasing complexity in configuration parameters associ- ated with the wireless network-think of transmit power, operational band, TDD pattern and many more. Especially when having to operate multiple network generations (2G, 3G, 4G and 5G) across many operational bands, all interfering with each other and becoming more and more dense to support increased demand for performance, network configuration becomes incredibly complex. There are many papers written on SON. SONs can be organized centralized where organizing algorithms are executed in a central network location (the operator cloud), distributed where each node (Base Station/Access Point) configures itself, or in a hybrid mode where the configuration is done partially from the cloud and partially by each node itself. The associated SON algorithms target to optimize the performance of the network with minimum human interference and are typically consid- ered proprietary/secret as they impact system performance greatly. Performance can be measured in aggregate throughput across all users, minimum downtime, best coverage and other parameters. SON targets Configuration of PCI as defined in 3GPP Release 8 ("eNB self-configuration")-the Cell ID needs to be unique to each base station so that UE can distinguish between cells for the purpose of handovers. Chapter 5 System software Management of Automatic Neighbor Relations (ANR)-each cell needs to own a database