LTE bandwidth: LTE eNodeB supports a possible list of bandwidths for deployment like 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz. The bandwidth can be divided into term of RBs. Some portion of bandwidth is used as guard band. I mean t say if eNodeB is operating is 20MHz bandwidth, it does not mean it is utilizing fully.
RB : Resource block is group of resource elements. A resource block consists of 12 sub carrier and 7 OFDM symbols. 1 RB = 12 * 7 = 84 Resource elements.
Sampling Frequency = sub carrier spacing * FFT size. In LTE, sub carrier spacing is 15Khz and size of FFT depends on bandwidth is being used.
If eNodeB is operating on 1.4 Mhz then only 128 FFT size is used.
if eNodeB is operating on 5 MHz then 512 FFT size is used and so on.