The exponential data traffic growth cannot be satisfied anymore with traditional ways by building new Base Stations (BS) or leasing new spectrum bands, which is costly from the operator's point of view. In order to accommodate with this high data proliferation, the Third Generation Partner Ship Project (3GPP) has introduced Long Term Evolution (LTE). An LTE network can handle more traffic with reduced cost and complexity, by adding new spectrum and wider bands. Researchers are more interested in coping with increased capacity by involving a heterogeneous network along with LTE as a better solution. The focus of this research is to discuss a specific variation of heterogeneous networks, which is Multi Radio Access Technology (RAT), as multiple

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