A Study on the Impact of Out-of-Band Emissions on Performance of 5G New Radio-Unlicensed (NR-U) Networks

New Radio-Unlicensed (NR-U) is a technology that allows fifth generation mobile networks to utilize unlicensed frequency bands, in particular, the 5 GHz band. To increase throughput, an NR-U base station (gNB) can simultaneously operate in several frequency channels within the 5 GHz band. However, the gNB cannot always transmit data through one channel and, at the same time, perform the channel access procedure in another channel due to the out-of-band emission problem, which leads to channel underutilization. As a result, the throughput of NR-U networks can heavily depend on the out-of-band emission level. In this paper, by means of simulation, the impact of out-of-band emissions on NR-U performance is studied when NR-U uses all channel access methods defined in the specification. It is shown that the out-of-band emission level affects the choice of channel access method optimal in terms of throughput. We also show that out-of-band emissions do not always have a negative impact on NR-U performance; sometimes they make it possible to achieve more than 30% throughput gain.