Ultra-slim design is also a key component of forward compatibility, a basic and specific application of GNR5 for abnormally unidentified targets. The basic rule in implementation processes to allow future developments is to leave as much space as possible, which means minimizing non-data transmissions (such as spectrum utilization and reducing aggregate interference), and reaching a high degree of flexibility and time-domain flexibility in 5G designs. It provides paths for future reconfiguration either in hardware or the specification itself