Smarter UMTS planning

Moe Rahnema
26 Apr 2006

GSM operators have an edge in the cost-effective deployment of UMTS by intelligently processing measurements from their GSM network to guide UMTS network planning

Incumbent GSM operators can exploit their existing network infrastructures in multiple ways to facilitate cost-effective optimal planning of UMTS in their networks. These include substantial radio base station co-location to save on site costs, sharing of access transmission facilities to achieve higher trunking efficiencies and use of network provided radio propagation measurements.

Most critically, existing GSM radio access facilities can be used to obtain radio propagation related measurements to characterize path loss and interference geometries to guide link budgeting and the site engineering for a UMTS overlay scenario.

Monitoring usage

Link budgeting arguments can show that a UMTS network around the 1700/2100 band will more than meet the link budgeting requirement to provide the same coverage as 1900 GSM for voice and real-time data rates up to about 144 kbps. This means the incumbent GSM operators can implement basically a one-to-one overlay of UMTS in their existing network to complement the GSM coverage with more voice capacity and in the meantime provide higher bit rate data services. Then, the built-in mechanisms in some of the existing GSM BSS equipments provide an edge for the in-operation measurement of path loss and interference in the network. Such mechanisms can be used to collect and process vast amounts of data from the live network. The resulting data are then used to characterize the interference and path loss geometries in the network on where the users are and from where they actually make their calls.

It is well known that UMTS is a power sharing radio access technology, based on W-CDMA, in which capacity and coverage are more impacted by interference than is the case in GSM. This means accurate realistic models to estimate path losses and the interference geometry are needed for optimum link budgeting, capacity planning, service coverage design and the required site engineering. A well-tuned propagation model to estimate path losses with sufficient accuracy is critical to UMTS planning and optimization. Most of the existing propagation tools such as the Okumura Hata, modified Hata, and Cost 232-Hata are based on statistical inferences made over a limited amount of measurements obtained through drive testing of selected network coverage areas. Therefore, such models are expected to provide only rough estimates of the actual propagation environment. Meanwhile, the new alternative methods of ray tracing requires detailed building and terrain height data, not always easily available, and has high computational demand.

However, the interference and paths loss geometries obtained from measurements made by mobiles operating in the existing GSM networks are expected to provide a practically more realistic and effective basis for guiding the UMTS radio planning and site engineering.

To fully and efficiently exploit such measurements on a large scale for UMTS planning, certain post processing routines and steps have to be scripted and implemented to routinely collect and characterize the measurement for easy and efficient use in network planning and model tuning.

Such measurements, as obtained for instance through the Ericsson's BSS ICDM mechanism, can be used after any necessary frequency related propagation corrections to obtain multiple data based models to serve multiple purposes for UMTS planning and pre-launch optimization.

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