Here I write on simple how guard band requirement for LTE for 2 option. Guard band requirement LTE verses GSM and guard band requirement LTE FDD verse LTE TDD
Guard Band Requirement: LTE-FDD vs GSM/UMTS
Configuration is simpler for FDD based systems because both LTE FDD and its neighboring technologies are based on frequency duplex and offer sufficient frequency separation between transmit and receive signals. With the introduction of SDR and SRAN product, the requirement of guard band for LTE has been further reduced in a co-located eNodeB.
GuardBand Requirement: LTE FDD vs LTE TDD
For two LTE TDD systems, no guard band is required for co-location or non co-location if both systems are synchronized. However, if FDD LTE is to co-exist with LTE TDD, a 5MHz guard band and separate antenna implementation is recommended. Moreover, if 2 LTE TDD systems that co-exist but not synchronized, a 5MHz guard band is still required regardless of whether they are co-located or not.