Cost efficient capacity expansion strategies using multi-access networks

Multi-access networks and hierarchical cell structures are two common capacity expansion strategies for mobile network operators. In both cases costs can be minimized for a set of available radio access technologies, given heterogeneous requirements on area coverage, capacity and quality of service. In this paper we quantify the infrastructure cost for a multi-access network composed of macro cellular HSDPA base stations and IEEE 802.11g WLAN access points. The network is dimensioned for an urban environment using a stochastic model for heterogeneous traffic density. With the used assumptions and modelling it is shown that a combination of HSDPA base stations deployed with 400 m cell radius together with WLAN in hot spots are sufficient for average traffic densities up to around 50 Mbps/km² (50 times the traffic of typical private voice users today). In order to evaluate the sensitivity to different design features, we introduce the elasticity of infrastructure cost and can thereby show that it is more important to improve capacity in HSDPA than coverage per 802.11g access point. However, with a sparse deployment of HSDPA macro cells (800 m radius) infrastructure cost is more elastic to 802.11g coverage. The paper also indicates some possibilities to differentiate future radio access technologies towards current systems.