In an attempt to address a growing demand for global mobile data traffic, one proposed solution has been to deploy what is known as small cells, which involve an isolated or clustered deployment of low powered base stations in footprints of macro cellular networks such as GSM based macro cellular networks. With Long Term Evolution (LTE) becoming a key standard for high speed data services in cellular networks, deployment of LTE small cells has proven to be an efficient and inexpensive way to address the growing demand for mobile data traffic.
However, a problem with introducing LTE small cells in footprints of macro cellular networks, meaning having both the small cells and a macro cellular network use the same frequency spectrum, is a resulting interference occurring between signals transferred between user equipment (UEs) operating based on the LTE technology and those that operate based on a technology of the macro cellular networks. This interference in turn results in degraded communication between UEs of each technology.
One solution to address the problem of interference has been to deploy the two technologies in separate spectrums. However doing so requires additional dedicated spectrums for the small cells, which given the ever increasing scarcity of wireless communication resources, is not a desirable solution.
An alternative solution has been to refarm a spectrum used by a macro cellular network, in particular, spectrum in use by an older generation macro cellular network, to allow one or more small cells deployed within a coverage area of the macro cellular network to also use portions of the same spectrum for transmitting signals. In doing so, a concept of frequency partitioning has been introduced. This concept is based on the idea that as demand for older technologies such as Global System for Mobile (GSM), based on which macro base stations of cellular networks operate diminishes, more and more of GSM's spectrum may be allocated for utilization by small cells such as LTE smalls cells deployed within the coverage area of the macro cells. Frequency partitioning, also known as Static Spectrum Refarming (SSR), allows for the configuration of the LTE smalls cells to occupy a determined portion of the macro cell's spectrum and thus UEs operating based on the technology of the macro cell can avoid using frequency channels of the spectrum occupied by the LTE small cells.
However, this approach incurs inefficiencies with regard to optimal utilization of the spectrum. LTE systems are deployed in bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz. FIG. 1 illustrates refarming of a GSM spectrum according to a static spectrum refarming method known in the Prior Art. As shown in FIG. 1, there is a 10 MHz spectrum 101 available for use by the technology of the macro cell, i.e., GSM technology. Only 2.4 MHz of spectrum 102 is needed to satisfy the demand of GSM based UEs, owing to diminished capacity requirements. Given the limitations on bandwidths in which LTE systems can be deployed, of the 7.6 MHz of spectrum left unused, LTE system are deployed in either the 1.4 MHz, 3 MHz or 5 MHz. Deploying the LTE system in the 5 MHz spectrum results in, as can be seen from FIG. 1, 3.6 MHz of unused bandwidth 104 that is simply going to be wasted.
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