 NR supports a large number of channel bandwidth com- binations and subcarrier spacings, which makes the realization of a unified B-IFDMA design very challenging. A typical B-IFDMA design can be characterized by three para- meters: the number of subcarriers per block Nsc, number of blocks per interlaces L, and number of interlaces per symbol N as illustrated in Fig. 8.26. In LTE-based eLAA, NRB =100 and with RB-based interlaced design, Nsc = 12,L = 10, and N = 10. The set of subcarriers Sn allocated for a specific interlace n can be represented as Sn = + m|0 m <Nsc, ISI<|NRB/N Note that it is not always possible to Operation in Unlicensed and Shared Spectrum NscxN Unused RBs Interlace 0 NSCXN Interlace 0 Figure 8.26 B-IFDMA design parameters and various design options [35]. divide NRB by N. As an example, in NR, for a channel bandwidth of 20 MHz and subcarrier spacing of 15 kHz, NRB = 106, and if the LTE-based eLAA parameters are maintained, then six RBs will not be used by any interlace. To avoid resource wastage, one can assign the remaining blocks to some of the interlaces. For example, if we assign R remaining blocks to the first R interlaces, then the set of subcarriers S' allocated for a specific interlace n can be represented as S'n = {Nsc m00m<Nsc, OSI<(NRB - n - 1)/N}. In this case, the number of blocks per interlace is a function of n as shown in Fig. 8.26. To meet the OCB requirement, one can design interlaces such that all interlaces occupy channel band- widths larger than what the minimum OCB requires. In that case, the interlace parameters Nsc,- L, and N need to be carefully chosen. In particular, assuming nominal channel band- width B and subcarrier spacing Af, the minimum normalized OCB among all interlaces is given by Bmin Nsc 12NRB/(NscN) - 1]N + 1) /B. As an example, in LTE-based eLAA, = 15 kHz and B=20 MHz, thus Bmin 0.819, which indicates that eLAA inter- lace scheme can only satisfy 80% of the minimum OCB requirements. If we consider an NR numerology with Af = 60 kHz, B = 20 MHz, and NRB = 2