To find the number of RBs in a 5G cell, we need to know the bandwidth and the subcarrier spacing of the cell. The bandwidth is the total frequency range allocated for the cell, while the subcarrier spacing is the frequency separation between adjacent subcarriers in the cell. A RB is a group of 12 consecutive subcarriers in the frequency domain 12. Therefore, the number of RBs in a 5G cell can be calculated by dividing the bandwidth by the product of the subcarrier spacing and 12.
Given that the bandwidth is 100 MHz and the subcarrier spacing is 60 kHz, we can use the following formula to find the number of RBs:
Number of RBs = Bandwidth / (Subcarrier spacing * 12) Number of RBs = 100 MHz / (60 kHz * 12) Number of RBs = 100000 kHz / 720 kHz Number of RBs = 138.888…
However, since the number of RBs must be an integer, we need to round it down to the nearest multiple of 3 3. This is because the NR standard defines different frequency ranges for different subcarrier spacings, and each frequency range has a minimum and maximum number of RBs that are multiples of 3 4. For example, for subcarrier spacing of 60 kHz, the frequency range is from 24250.08 MHz to 52600.08 MHz, and the minimum and maximum number of RBs are 66 and 273, respectively.
Therefore, the closest multiple of 3 to 138.888… is 135. However, this number is not valid because it is lower than the minimum number of RBs for subcarrier spacing of 60 kHz. The next valid multiple of 3 is 273, which is also the maximum number of RBs for subcarrier spacing of 60 kHz. Therefore, the correct answer is C. 273.
