... Timely -published in 2020 or later [6], [8], [9], [12], [14], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25] Cloud-RAN [5], [7], [8], [9], [10], [11], [12], [13], [14], [15], [17], [21], [22] Open RAN [20], [21], [22] Virtual RAN [5], [7], [8], [10] , [13], [18], [21] Network sharing Network slicing [7], [8], [13] Sleep modes [23], [24] Power amplifier improvements [24] Artificial Intelligence [5], [7], [8], [20], [23], [25], [26] Renewable energy [5], [22] Energy harvesting [6], [7], [12], [17], [26] B5G and 6G energy saving directions [27], [16], [17], [18], [19] A critical review of litterature Energy savings overview and comparison [24] Overview of research projects [5], [8], [21], [28] to current networks [54]. Results in the area on energy reduction contributions include: [5], [55], [56]. ...