  Energy efficiency is critical for future sustainable cellular systems. Power
saving optimization has been a key part of the fifth generation (5G) new radio
specifications. For 5Gadvanced and future 6G, with the anticipation of a
trillion internet of things (IoTs) devices with non-rechargeable or low-density
batteries, device power efficiency is rather essential. There are numerous
contributions from industry and academia which present the potential power
saving gains of the various 5G power saving techniques; however, there is a
lack of art on the performance cost paid to achieve such power saving gains.
Therefore, this paper presents a comprehensive evaluation of the radio latency
and reliability cost, which is lost due to a certain 5G new radio power saving
feature. A thorough review of the state of-the-art 5G power saving techniques
is introduced. Extensive system level simulations are performed to evaluate the
latency and reliability cost of the considered power saving features. The paper
offers valuable recommendations for supporting power efficient latency-critical
traffic for beyond 5G-advanced systems.
