The capacity requirements of cellular networks continue to grow. This has forced cellular operators to seek new ways of improving the availability and transmission rate experienced by users. The majority of cellular network data users are located inside buildings, where coverage is difficult to ensure due to high penetration loss. Indoor users also cause high load to outdoor networks, reducing the quality and availability for outdoor users. This has given rise to a growing need for implementing dedicated indoor systems, and further optimizing their performance to provide high capacity.
It was estimated that in 2011 there were 5.37 billion mobile subscriptions in 3GPP-supported GSM, UMTS/HSPA and LTE networks, of which 890.7 million were using UMTS/HSPA. Currently, UMTS is the leading standard for providing mobile broadband, although LTE is becoming increasingly popular. The planning of radio networks is well known and documented. However, the planning and optimization of indoor networks has not been widely studied, although clear improvements in both coverage and capacity can be achieved by optimizing cell- and antenna line configuration.
This thesis considers the special characteristics of the indoor environment with regard to radio propagation and radio network planning. The aspects of radio network planning are highlighted especially for WCDMA radio access technology. The target is to provide guidelines for indoor radio network planning and optimization using an outdoor-to-indoor repeater or a dedicated indoor system with various antenna and cell configurations. The studies conducted here are intended to provide better understanding of the indoor functionality and planning of WCDMA radio access, and UMTS cellular system including the latest HSPA updates.
The studies show that the indoor performance of a high data rate WCDMA system can be improved by increasing the antenna density in the distributed antenna system, or by utilizing uplink diversity reception. It is also shown how system capacity can be further improved by adding more indoor cells to a single building. The inter-cell interference is analyzed, and the limits for cell densification are discussed.
The results show that compared to dedicated indoor systems, similar indoor performance can be provided by extending macrocellular coverage inside buildings using an outdoor-to-indoor repeater. However, good performance of repeater implementation needs careful repeater antenna line and parameter configuration. Nevertheless, capacity is in any case borrowed from an outdoor mother cell.
Sharing frequencies between outdoor and indoor systems is often necessary due to high capacity demand and limited available frequency band. A co-channel indoor system was measured to affect both uplink and downlink performance of an outdoor cell. In the uplink, a clear increase in uplink intercell interference was observed. Throughput degradation was also measured in downlink, but the affect is limited to the area close to the indoor system. However, the added high capacity of an indoor network usually justifies performance degradation.
The results can help mobile operators design their networks to provide better coverage, higher capacity and better quality for indoor users. After taking into account the implementation costs, the results also help operators to reach a techno-economic trade-off between the various deployment options
