The Third-Generation Partnership Project (3GPP) defines standards and technical specifications for a 3G mobile system referred to as Long Term Evolution (LTE). In contrast to the circuit-switched configurations utilized by previous cellular communication systems, LTE has been designed to support packet-switched services, thereby providing seamless Internet Protocol (IP) connectivity between user equipment (UE) devices and one or more packet data networks (PDNs) without disruption during the geographic movement of end users.
While the term “LTE” includes the evolution of the Universal Mobile Telecommunications System (UMTS) radio access through the Evolved UTRAN (E-UTRAN), it is also accompanied by an evolution of the non-radio aspects under the term “System Architecture Evolution” (SAE), which includes the Evolved Packet Core (EPC) network. Together LTE and SAE form the Evolved Packet System (EPS).
In most LTE networks, the E-UTRAN access network is made up of Evolved NodeB (eNodeB, or eNB) radio base stations that directly communicate with UE devices. One or more eNodeBs may be located in a grouping and coupled to the EPC mobile core (through a mobile backhaul network) via a cell site router (CSR). The mobile backhaul network may utilize one or more of IP, Multiprotocol Label Switching (MPLS), Hierarchical MPLS (H-MPLS), or another protocol.
The EPC typically includes at least the following three logical nodes: a Mobility Management Entity (MME), a Serving Gateway (S-GW), and a Packet Data Network Gateway (PDN-GW). These nodes, and other logical nodes of the EPC, are well known to those of skill in the art.
As the UE devices utilizing LTE networks are often mobile, changes of geographic location by the UE devices occur. As a UE device moves away from one eNodeB and closer to another eNodeB, the LTE network manages a handover of the UE device from the first “source” eNodeB to the second “target” eNodeB to ensure seamless connectivity. Depending upon the scenario and the particular network configuration, the handover may also require a change of cell site, MME, and/or S-GW. In many LTE network configurations, handover communications are exchanged between the two eNodeBs through the EPC mobile core network and are switched centrally at a Local/Regional Switching Site. These handover communications are typically referred to as X2 traffic, which is named after the X2 virtual interface used by eNodeBs for such communications. In some typical configurations, each eNodeB is assigned one or more network addresses (e.g., IP addresses), and one such network address is be used by the eNodeB primarily for X2 communications. In some embodiments, however, an eNodeB has a first network address for X2 control plane (X2-C) traffic, and a second network address for X2 user plane (X2-U) traffic.
Instead of sending the X2 traffic back to the EPC to be sent to a remote eNodeB, it is also possible for network operators to manually configure static routes between eNodeBs in a mobile backhaul network for the X2 traffic, which may include placing a pair of X2 members in an MPLS Virtual Private Network (VPN). However, a given eNodeB may typically have approximately 20-30 neighboring eNodeBs at a time, each of which will require a configured route with each of its neighbors, which requires a large and error-prone configuration, and which further consumes a large amount of routing state to be maintained in the network. Additionally, as the number of eNodeBs in a network tends to fluctuate as networks are extended, reconfigured, and maintained, a huge administrative overhead is thus created for maintaining such static routes. Accordingly, because of the complexity of creation and maintenance, many network operators forego creating and maintaining inter-base station routes, and simply allow X2 traffic to flow back through the EPC mobile core to be switched.
Recently, the 3GPP has begun working on defining new applications that will be carried over the X2 interface. These new applications include Coordinated Multi-Point (CoMP), Enhanced InterCell Interference Cancellation (eICIC), and Location services, among others. These applications require much higher bandwidth and are also much less delay tolerant than current X2 traffic. Accordingly, there is a need for easily and efficiently routing X2 traffic between eNodeBs.