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Fault management is a crucial part of cellular network management systems. The status of the base stations is usually monitored by well-defined key performance indicators (KPIs). The approaches for cell degradation detection are based on either intra-cell or inter-cell analysis of the KPIs. In intra-cell analysis, KPI profiles are built based on their local history data whereas in inter-cell analysis, KPIs of one cell are compared with the corresponding KPIs of the other cells. In this work, we argue in favor of the inter-cell approach and apply a degradation detection method that is able to detect a sleeping cell that could be difficult to observe using traditional intra-cell methods. We demonstrate its use for detecting emulated degradations among performance data recorded from a live LTE network. The method can be integrated in current systems because it can operate using existing KPIs without any major modification to the network infrastructure. peerReviewed

Seppo Hämäläisen tutkimus käsittelee kolmannen sukupolven matkapuhelinjärjestelmän (WCDMA-järjestelmä) suorituskykyyn ja sen simulointiin liittyviä kysymyksiä. Tutkimuksen tuloksena kehitettyjä työkaluja voidaan käyttää kolmannen sukupolven matkapuhelinjärjestelmän radioverkon kapasiteetin tutkimiseen. Useita WCDMA- järjestelmän parametreja on muutettu tai sovittu kansainvälisessä 3GPP-standardointiprojektissa tämän tutkimuksen perusteella. Tällaisia parametreja ovat mm. liikkuvan asemantehovahvistimen lineaarisuusvaatimus, vastaanotinsuodattimen selektiivisyysvaatimus sekä liikkuvan aseman minimitehovaatimus. In this thesis the WCDMA radio network performance and the radio network performance simulations are discussed. As research results, simulation tools are developed that can be used when investigating the WCDMA radio network performance, the effects of the various parameters on the performance and the effects of the various algorithms on the performance. Another research result is performance analysis for a set of WCDMA system parameters and algorithms based on simulations. In addition, two new methods to improve WCDMA and cdma 2000 system performance have been developed. By using the developed radio network simulator, parameters and algorithms of the WCDMA system can be studied for standardization purposes. The developed tools can be used for the development of radio resource management algorithms, radio network planning tool development and as a tool for radio network optimisation. Here two kinds of simulators are considered – static and dynamic tools. Static simulators are simple computer software, which can be used to generate sufficient results in a short time. Dynamic simulators are more complex tools, which model time span, user mobility, traffic, multiple access and realistic radio resource management. In this work, the WCDMA radio network capacity has been investigated by using the developed tools. The WCDMA base station receiver can be implemented by using a so-called multi-user detection. In this work the capacity gain due to the multi-user detection has been studied. Basestation transmission can be based on orthogonal codes or the mobile station receiver can employ interference cancellation. Here the gains from the orthogonal codes and the interference cancellation were investigated. In addition, gains from soft handover were studied. Due to the linearity of the mobile stations power amplifier and selectivity of the mobile station receiver filter, the base stations or the mobile stations operating in the adjacent frequency can cause interference in the desired channel. Here the requirements for the linearity and selectivity have been studied based on static simulations. By using simulations capacity losses due to interference from having the source in the adjacent frequency has been studied. In this thesis the effect due to power control and its parameters, random access, handover algorithms and their parameters, and compressed mode have been studied by using a dynamic radio network simulator. The performance of High Speed Downlink Packet Access (HSDPA) has also been studied with the dynamic tool. In order to improve the performance of CDMA systems two novel methods – diversity random access and Site Selection Diversity Transmit (SSDT) – has been developed. Both methods are in use in both the WCDMA and cdma 2000 systems. Several WCDMA system parameters have been modified or agreed in the 3GPP project based on the research shown here. Such parameters are e.g. the linearity requirement of the mobile station power amplifier, the selectivity requirement of the mobile stations receiver filter and the minimum power requirement of the mobile station.