We consider the optimization of the Core Network section of a mobile cellular network. While we focus on GPRS the proposed method can be applied to UMTS as well. The problem is to find an optimal assignment of PCUs (Packet Control Units, a module of the BSC) to SGSNs based on measured data. Two concurrent optimization goals apply: balance the number attached Mobile Stations among the available SGSNs, and at the same time minimize the inter-SGSN Routing Area Updates. The input data for the optimization can be extracted from the live traffic signaling by passively monitoring the Gb links between the PCUs and SGSNs. We show how to estimate the mobility matrix and the distribution of attached Mobile Stations for each Routing Area, and how to clean-up the data at hand. A novel ILP formulation is provided for the (re)assignment problem. We present exemplary numerical results for a case study based on real traces from an operational network.
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