The paper addresses the frequency allocation and power setting problems in a cellular system with two cell layers. The macro cell layer provides coverage while the micro cell layer adds extra capacity to parts of the service area. A frequency allocation principle is studied where no division of the spectrum is made between the cell layers. The micro cells are instead reusing frequencies from the macro layer. In order not to cause excessive interference to the macro layer, a transmitter power restriction is put on the micro cell base stations and the mobile stations connected to the micro cells. Simulations show that the principle is feasible as long as the micro cells are small enough compared to the macro cells. It is also shown that an adequate frequency plan for the micro cells can be found automatically.
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