Local delay and energy efficiency analysis in HetNets with random DTX scheme

Heterogeneous cellular networks (HetNets) are to be deployed for future wireless communication to meet the ever-increasing mobile traffic demand. However, the dense and random deployment of small cells and their uncoordinated operation raise important concerns about energy efficiency. On the other hand, discontinuous transmission (DTX) mode at the base station (BS) serves as an effective technology to improve the energy efficiency of overall system. In this paper, we investigate the energy efficiency under the finite local delay constraint in the downlink HetNets with random DTX scheme. Using a stochastic geometry based model, we derive the local delay and energy efficiency in the general case and obtain closed-form expressions in some special cases. These results give some useful insights on the system performance, taking the tradeoff between local delay and energy efficiency into account. Furthermore, we provide the low-rate and high-rate asymptotic behavior of the maximum energy efficiency. It is analytically shown that it is less energy-efficient to apply random DTX scheme in the low-rate regime. However, in the high-rate regime, random DTX scheme is essential to achieve the finite local delay and higher energy efficiency.