|
| Approach | Techniques | Energy savings/enhancements | Considerations | Comments |
|
| Power amplifier improvement | Digital predistorted Doherty-architectures and GaN [22] | Up to 50% | Linearity
PAPR
Cost |
Improvement depends on a special design and material |
| CFR and DPD with Doherty [18, 22] | |
| class-AB with digital predistortion [11] | Approximately 50% |
| class J amplifier [11] | 70% to 90% |
| inverse class F [23] | 74% |
| Switched-mode power amplifier (SMPA) [22, 24] | 80–90% |
|
| Time domain energy-efficient | Unicast [27] | 40% to 50% | Synchronising
UE battery life
QoS |
Energy savings depend on the PA operating time |
| MBSFN [27, 30] | 55% |
| DTX [28] | Up to 85% |
| Optimise subframes per frame [31] | 90% |
|
| Cell switch on/off | Increase ON cell radius [35, 36] | Residential scenario [35] | 37.5% | Coverage
UE battery life
QoS |
Energy savings depend on the number of BSs and the period of time over which each of the BSs is switched off |
| Office scenario [35] | 25–50% |
| Hierarchical scenario [35] | 17% |
| Uniform scenario [36] | 26–40.7% |
| Hierarchical scenario [36] | 30% |
| Switch off any fraction of the cell according to a deterministic traffic scheme [37] | 25–30% |
| Optimise the number of active BSs [9] | 12–40% |
| Ecological protocooperation [38] | 72.9% |
| Maximum average distance between BSs [39] | 29% |
|
| Energy-efficient architectures | Cell Zooming [42–45] | Up to 40% | Interference
Dead zone problem |
Must take into account interference management between heterogeneous environments |
| HetNets [22, 46, 55] | Macrocell-microcell | 44% |
| Macrocell-picocell | 60% |
| Macrocell-femtocell | 78–80% |
| Relay [57, 59] | 8%–18% |
|
| Transmission scheme | Reduce the number of antennae [69, 70] | 50%, depending on the number of antennae. | QoS
Impact on the UE | Energy savings depend on the number of antennae that will be switched off |
|
