The present document is a technical report for NR sidelink evolution services in Rel-18. The purpose is to specify radio solutions that are necessary for NR to support sidelink services working on unlicensed spectrums.
In Rel-16, sidelink communication was developed in RAN mainly to support advanced V2X applications. In Rel-17, SA2 studied and standardized Proximity based service including public safety and commercial related service. As part of Rel-17, power saving solutions (e.g., partial sensing, DRX) and inter-UE coordination have been developed in RAN1 and RAN2 to improve power consumption for battery limited terminals and reliability of sidelink transmissions.
Although NR sidelink was initially developed for V2X applications, there is growing interest in the industry to expand the applicability of NR sidelink to commercial use cases. For commercial sidelink applications, two key requirements have been identified:
Increased sidelink data rate
Support of new carrier frequencies for sidelink
Increased sidelink data rate is motivated by applications such as sensor information (video) sharing between vehicles with high degree of driving automation. Commercial use cases could require data rates in excess of what is possible in Rel-17. Increased data rate can be achieved with the support of sidelink carrier aggregation and sidelink over unlicensed spectrum. Furthermore, by enhancing the FR2 sidelink operation, increased data rate can be more efficiently supported on FR2. While the support of new carrier frequencies and larger bandwidths would also allow to improve its data rate, the main benefit would come from making sidelink more applicable for a wider range of applications. More specifically, with the support of unlicensed spectrum and the enhancement in FR2, sidelink will be in a better position to be implemented in commercial devices since utilization of the ITS band is limited to ITS safety related applications.
Another aspect to consider is the V2X deployment scenario where both LTE V2X and NR V2X devices are to coexist in the same frequency channel. For the two different types of devices to coexist while using a common carrier frequency, it is important that there is mechanism to efficiently utilize resource allocation by the two technologies without negatively impacting the operation of each technology. This requirement was also mentioned as part of the input from 5G Automotive Association to the Rel-18 RAN Workshop.