Cell Coupling in UMTS Radio Networks: Models and Methods for Automatic Capacity Optimization

摘要

A mobile phone manufacturer recently introduced a new "3G" model, which relies on UMTS radio technology. The launch soon produced a surge of complaints. Customers criticized poor coverage, constantly switching between networks, or simply slow data connections. Apparently, the gadget could not reliably live up to the marketing promise of a twofold increase in connection speed. Experts suspected an immature chipset, bad hardware assembly, or flawed firmware as culprits. It soon became clear, however, that poor radio network planning was to blame [1]. Operators had failed to provide sufficient infrastructure and capacity for the unexpectedly high demand. UMTS is fundamentally different from previous radio systems. Remedying this situation is particularly difficult, because the radio links interact through interference. Known recipes for planning problems no longer apply. Unlike before, for example, the directions the radio antennas point to are a major lever on network capacity. This article shows how the notion of cell coupling is the key to an efficient decision support system for 3G radio network planning. An operator facing the above problem can thus increase capacity significantly by merely adapting antenna configurations. The present article outlines a structured approach at solving this complex problem. First, we introduce a concise system model for UMTS, which is amenable to new analytical insights. For optimizing performance, we derive a further simplified optimization model, which we finally test under realistic conditions. For a detailed report on previous and related work and for full technical details, see [3].