Functions of X2 Interface

The X2 is a new type of interface introduced by the LTE Radio Access Network. It connects neighboring eNodeBs in a peer to peer fashion to assist handover and provide a means for rapid co-ordination of radio resources. This paper considers in detail the functions that are performed over the X2 interface. X2 does not require a significant bandwidth. RAN Vendors expect that traffic levels will be only a few percent of the main S1 backhaul interface. Delay requirements are more challenging X2 delay for user traffic is additional to that on the S1, so should be as small as possible. Furthermore, interference co-ordination features proposed for future releases of LTE-Advanced are highly sensitive to small delays.