d consists of replacing the antenna with a load and creating a standing wave along the antenna line. The SWR is the ratio of the maximum to the adjacent mini- mum magnitude of the signal level. When this ratio exceeds a value of 1.3, it means that feeder loss is high. Site Re-engineering One of the network maintenance operations is site re-engineering. This has been explained in previous sections. Radio Network Optimisation NMS Maintenance The NMS is an important entity as it is the supervision system that monitors the whole network. The NMS is used to change the settings of the network, collect statistics, detect alarms, etc. It runs over an operating system, SO the NMS care activity consists of checking that this operating system works properly. The system administration task is required on either a daily, weekly or monthly basis. Daily Tasks Internal alarms are the first thing to check daily. They indicate what are the faulty processes or applications. Special database log files record all the errors that occurred during the previous day. Some alarms can even indicate the processes that are still running but will encounter some problems soon. Incremental backup is performed on a daily basis, where only changes from the previous day are stored. The aim is to optimise the storage space and to activate the backup in the case of a system crash. The advantage of such backup is that it is performed online without cutting into the network. Another task is to check that this daily backup is well done. In terms of parameter handling, a regular consistency check is done to compare the parameter values on the network (i.e. in the BSC and BTS local databases) and the OMC. So that the radio optimisation process runs correctly, it is also important to check the status of statistics transfer from the network towards the NMS databases and fix all relative problems. Weekly Tasks On a weekly basis, the team verifies the available disk size and cleans all temporary files and logs. It is the duty of the NMS care team to ensure th