In wireless Frequency Division Multiple Access (FDMA) systems, one factor that reduces the spectrum utilization efficiency is the Adjacent Channel Interference (ACI). In a cellular structure, adjacent frequencies are not used within the same cell. This fact provides an opportunity to reducing the frequency spacing between adjacent frequency to the extend of allowing for partial overlap of the radiated spectra of two adjacent channels. The ACI is limited by distance, however, it is possible for two mobile units operating in an overlapped area between two cells to exhibit excess interference. The excess interference can be controlled by adaptive equalizers.

This thesis investigates the performance of Decision Feedback equalizers (DFE) in controlling excess ACI caused by partial spectral overlap. To evaluate the system performance, analytical methods and computer simulations were used. In the analysis, the Minimum Mean Square Error (MMSE) criterion was used. Mathematical expressions for the MMSE were derived under various system parameters and configurations. The MMSE is obtained as a function of the Signal to Interference Ratio (SIR). The computer simulations were run under the same conditions.

The thesis concludes that in a cellular FDMA systems, the frequency spacing between two adjacent channels can be reduced (hence improving the spectrum utilization), and that a DFE equalizers can effectively control any excess interference.