Spectral and energy efficiency in multi hop OFDMA based networks

In recent decades, due to limitation of radio spectrum and increasing users in wireless networks, spectral efficiency has been a considerable issue in literatures. In addition, energy consumption is rapidly increasing in wireless communications due to growing demand for wireless technologies especially cellular networks. Therefore, energy efficiency has become an important issue in such networks. This contribution proposes an approach to improve energy efficiency while provides minimum spectrum required for an Orthogonal Frequency Division Multiple Access (OFDMA) based, multi relay, multi user cellular network. An objective function is formulated initially as a ratio of spectral efficiency and power, and then Interior Point Method is employed to solve the optimization problem. In this paper, power allocation and subcarrier allocation are formulated jointly to provide minimum required spectrum and maximum energy efficiency in the system. In addition, Inter Cell Interference effect on spectral efficiency has studied. The results show that considering the minimum Spectral Efficiency provides required Quality of Service for users, however in low amount of maximum available power, Energy Efficiency is decreased.