Deployment of a large number of femtocells to jointly provide coverage in an enterprise environment raises critical challenges especially in future self-organizing networks which rely on plug-and-play techniques for configuration. This paper proposes a multi-objective heuristic based on a genetic algorithm for a centralized self-optimizing network containing a group of UMTS femtocells. In order to optimize the network coverage in terms of handled load, coverage gaps, and overlaps, the algorithm provides a dynamic update of the downlink pilot powers of the deployed femtocells. The results demonstrate that the algorithm can effectively optimize the coverage based on the current statistics of the global traffic distribution and the levels of interference between neighboring femtocells. The algorithm was also compared with the fixed pilot power scheme. The results show over fifty percent reduction in pilot power pollution and a significant enhancement in network performance. Finally, for a given traffic distribution, the solution quality and the efficiency of the described algorithm were evaluated by comparing the results generated by an exhaustive search with the same pilot power configuration. 1. Introduction Coverage and capacity are two major aspects which operators have to address while offering new mobile multimedia services to their customers such as video on demand, web 2.0 services, and social networking. At the same time, indoor coverage presents many challenges in the current 3rd generation (3G) (e.g., UMTS) and future 4th generation (4G) (e.g., LTE) cellular networks. Those networks operate at higher frequencies in comparison with the conventional 2nd generation (2G) (e.g., GSM) networks [1]. Consequently, signal penetration through building walls becomes a complex process. This fact creates a real challenge, especially that studies on wireless usage show that more than 50% of voice calls and more than 70% of data traffic are generated indoors [2]. Therefore, proposing data intensive services in conjunction with the presence of the indoor coverage challenges are the main drives for deploying specific devices such as femtocells to complement the traditional outdoor base stations. A femtocell is a short-range (up to 40？m) low-cost low-power base station (BS) installed by end users indoors to enhance voice and data receptions. Femtocells make use of the broadband connections such as digital subscriber line (DSL), cable modem, or a separate radio frequency (RF) backhaul channel to communicate with the cellular network [3] as shown in Figure 1.
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