It is used in frequency-division multiplexing and may be used in both wired or wireless communications, so that adjacent frequency bands on the same media can avoid interference.
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 co-exist but are not synchronized then a 5MHz guard band is still required regardless of whether they are co-located or not.
Configuration is simpler for FDD based systems because both LTE FDD and its neighbouring 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 is further reduced in a co-located eNodeB.
For two LTE TDD systems, no guard band is required for co-location or non co-location if both systems are synchronized.
