Abstract   This paper addresses Co-Channel Interference (CCI) problem in cellular networks. Therefore, network performance improvements through reducing CCI are evaluated using different four interference mitigation techniques. These techniques represent traditional sectored Fractional Frequency Reuse (FFR), sectored FFR do Beamforming (BF), Relay Assisted (R-A) sectored FFR and R-A sectored FFR do BF technique. Additionally, each one of the techniques which cooperative BF covers the horizontal, vertical and Three Dimensional (3D) BF techniques. Consequently, sectored FFR do BF contains three different scenarios. These scenarios indicate sectored FFR do horizontal BF, sectored FFR do vertical BF and sectored FFR do 3D BF. Furthermore, there are three different configurations of applying BF in R-A sectored FFR do BF. These configurations signify Relay Station (RS) do BF only, Base Station (BS) do BF only and both RS and BS do BF. Therefore, each configuration consists of three different scenarios according to the applied BF technique. Consequently, nine different scenarios are studied. A comparison of all scenarios in different techniques is introduced to enhance the network Quality of Service (QoS). Analytical treatments are conducted. As a result, closed-form expressions for worst-cases Cell Edge User's (CEU's) Signal to Interference Ratio (SIR), Cell Centre User's (CCU's) SIR and inner radius are implemented. These expressions are used to compare different techniques using various performance evaluation metrics. The results show, that as unpredicted, the performance of R-A sectored FFR is close to that of R-A sectored FFR BF in low SIR threshold and high PL exponent ranges. Therefore, R-A sectored FFR is preferred in use from the network cost and power consumption perspectives. Furthermore, vertical BF shows performance close to 3D BF in low Path-loss (PL) exponent range. Therefore, applying vertical BF is preferable with regard to the network budget and energy preserve. Moreover, it is observed, that configuration of BS do BF is superior to other configurations when horizontal or vertical BF technique is applied. Additionally, the configuration of both RS and BS do BF outperforms the other configurations when 3D BF is applied. However, as unexpected, it performs worse than them when the other BF techniques are applied. The work outcomes attain much higher CEU's SIR improvement. Therefore, the outage probability is decreased. Thus, network can cover more users. Accordingly, the total network cost is reduced. So, this treatment improves the network performance while keeping lower network cost.  .