Trade-off of average area spectrum efficiency and energy efficiency

Green communications is put forward to decrease the operational expenditure (OpEx) and carbon emission of communication networks in recent years. The relationship between spectrum efficiency (SE) and energy efficiency (EE) has induced more attentions in academic field, however, most efforts are spent on SE-EE trade-off of link-level not system-level. In this paper, we analyze the trade-off between average area SE (A²SE) and EE under the realistic power consumption model (PCM) in system-level perspective. First, we give the theoretical closed-form expression of A²SE for a cell as a function of edge SNR. And then, closed-form approximation (CFA) of A²SE is derived, and it largely coincides with theoretical A²SE and is reversible. Based on the CFA, we find the closed-form trade-off of A²SEEE concisely. Further, the optimal EE, corresponding A²SE and transmission power of BS under different cell radiuses are got according to the A²SE-EE trade-off. These results are helpful to design cell radius and transmission power which meet different needs for A²SE and EE of wireless networks.