On the other hand, unlike in LTE, in NR the SS Blocks can be transmitted in different and multiple in frequency locations (e.g., not only in the center of the carrier frequency). In more detail, in the RAN1 #87 meeting it was agreed that (1) for an NR cell, the center frequency for the synchronization signal can be different from the center frequency of the NR carrier; and (2) there may be a relationship between the center frequency of the NR carrier and the center frequency of synchronization signals and there may be a tradeoff between UE complexity and flexibility.

And, in RAN1 NR Ad Hoc #1, it was agreed that (1) when the synchronization signal bandwidth is smaller than the minimum system bandwidth for a given frequency band, RAN1 strives to make the synchronization signal frequency raster sparser compared to channel raster to reduce the UE initial cell selection burden without limiting the NR deployment flexibility; and (2) when the synchronization signal bandwidth is the same as the minimum system bandwidth for a given frequency band that the UE searches, the synchronization signal frequency raster is made the same as the channel raster. In either scenario, the UE searches for all the possible synchronization signal frequency locations defined by the synchronization signal frequency raster.

One of the reasons for having this flexibility is to enable the UE to perform measurements on multiple frequencies different from the serving frequency without performing retuning (e.g., in the case of overlapping carriers).

Measurement Framework in NR