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.
For example:
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.