Frequency clearance is mandatory requirement in designing, implementing and optimizing radio frequency for cellular networks. Though a good frequency plan has been defined to ensure acceptable of internal interference level, an external interference sometime disturbs the radio networks not only in the operational phase but also when the mobile operator optimizing their radio networks.
Continuous radio performance quality monitoring activities should cover major KPIs as well as interference level in the network. Identification on interference level can be performed through BSS performance statistic such as radio quality issues relate to handover activities and signaling and traffic channel drops analysis.
There are many reasons causing radio quality problem such as defective RF module on the BTS, non optimized coverage design, bad frequency planning, external interference, etc.
Unluckily, not all of root causes of the radio quality problems can be easily identified by the RF engineers, especially when the problem occurred due to external interference on the uplink direction. At the end, a field measurement test has to be conducted, e.g. using spectrum analyzer.
To ease the field measurement test in identifying interference sources in office interference level analysis shall be initialized using dedicated mode or idle mode performance data. Measurement Reports send by MS is common statistic data used by radio networks during dedicated mode, and specific vendor RF feature like Idle Interference Measurement is available as well for idle interference analysis.
Through geographical information system application available in market such as MapInfo, those RF measurement statistic data can be easily manipulated using data interpolation thus become useful information for RF engineer to conduct external interference sources identification.
Hence, corrective actions shall be taken placed in the form of frequency tuning or external frequency clearance.