Survey of Green Radio Communications Networks: Techniques and Recent Advances

Table 1

Classification of some energy efficiency metrics.

Level	Units	Description
Facility level	Power usage efficiency is a ratio ≥ 1.	Defined as the ratio of total facility power consumption to total equipment power consumption
	Data centre efficiency is a percentage (%)	Defined as the reciprocal of PUE
Equipment level	PA efficiency is a ratio	The ratio of output to input power
	W/Gbps	The ratio of energy consumption to effective system capacity
	Gbps/W	The ratio of useful work to power consumption
	MIPS/W	Millions of instructions per second per Watt
	MFLOPS/W	Millions of floating-point operations per second per watt
Access node level	b/s/Hz	Spectral efficiency refers to the rate at which information can be transmitted over a given bandwidth in a specific communication system
	b/s/Hz/W	The spectral efficiency per Watt
	(b·m)/s/Hz/W	The radio efficiency measures the rate at which data are transmitted and the transmission distance attainable for a given bandwidth and power resources supplied
	J/bit	The energy consumption rating is defined as the number of bits transmitted per Joule of energy
Network level	km^2/W	The ratio of coverage area to site power consumption
	W/km^2	The power consumed per unit area
	Users/W	The ratio of users served during the peak traffic hour to site power consumption
	J/bit/m^2	The energy consumption with respect to the number of transferred bits and the coverage area
	W/bps/m^2	The average power usage with respect to the average transmission rate and the coverage area