How much energy can be saved by energy-delay tradeoff in Radio access network?

The energy-delay tradeoff is one of the fundamental tradeoffs when looking for energy efficient wireless access networks. The potential to save energy at the base station (BS) by introducing delay in the downlink is constrained by both the non-ideal efficiency characteristics of power amplifier (PA) and the energy cost suffered by the mobile terminals (MT) due to the longer reception time. One possible way to control energy consumption at the MT is to introduce transmission delay in the uplink too. In this paper, we study the potential for energy saving by introducing transmission delay both in the uplink and in the downlink of a wireless network. We show that the energy saving potential depends on the network load (both uplink and downlink) and the PA efficiency (employed at the BS and the MT). Energy can be saved for most of the load combinations in uplink and downlink without draining out the battery of MT. One exception is the case with very low uplink load and very high downlink load. In that case, energy can be still saved at the cost of small excess energy consumption at the MT.