# An Efficient 5G Data Plan Approach Based on Partially Distributed Mobility Architecture
## 3 The Proposed 5G Procedure
### Inter-Gateway Handover  
Inter-gateway handover occurs between a source eNB and a target eNB when the U.E. moves to a new gateway's domain. Deploying distributed architecture is a critical step in the suggested network to provide flat network architecture. Figure 7a illustrates the mobility situation in 4G architecture, While our proposed architecture is illustrated in Figure 7b. The signaling communications during handover have been reduced immensely by eliminating the involvement of P-GW. In our proposed 5G concept with distributed M-GWs, a direct communications connection between the M-GWs, as illustrated in Figure 8, can be established. There are three main steps during the handover procedure, including establishing X2 tunnel, inter M-GW tunnel, and switching destination G.W., shown in Figure 8.  
The X2 tunnel establishment is similar to traditional LTE/EPC. The source eNB chooses the target eNB and decides to handover. This decision is based on the neighbor cell list and information on the signal strength after exchanging measurement report messages to other eNBs, by preparing X2 signaling and sending a Handover request message to the target eNB. The target eNB replies with an acknowledgment that it can serve U.E. An X2 tunnel is established to the target eNB to buffer data. The U.E. starts the detach procedure from the source eNB and attaches it to the target eNB. After the attachment, buffered data will be forwarded to U.E. through a radio connection from the source eNB. Figure 6: The handover without gateway relocation procedure in the proposed 5G concept. The most significant modification of the proposed scenario is inter-GW tunneling. While in the 4g network, the S-GW has to establish a GTP tunnel to P-GW by sending a modified bearer request message. Instead, in the proposed network, the packets are delivered directly through the proposed 5G concept inter-tunnel from the source M-GW (MGW-S) to the target M-GW (MGW-T). While U.E. moves to a new eNB belonging to the new M-GW, C.E. receives a path switch request from the target eNB, depending on the target M-GW. The C.E. allocates parameters and distributes the forward data plane to the corresponding gateway and eNB. GTP protocol has remained for tunneling between E-UTRAN and Core network devices. After establishing the inter-GW tunnel, packet routing in the optimal path through the direct tunnel, thus reducing end-to-end latency and enhancing performance in the core layer. The final step is re-routing to the target M-GW. This scenario assumes packets are routed initially to the source M-GW from M-GWn located close to the source M-GW. Two scenarios for M-GWn: it either is under control of the current C.E. or belongs to another C.E. If M-GWn is under control of the current C.E., C.E. sends a request message to re-route the data path. Otherwise, C.E. does not know the M-GWn. So it has to request MCE to get information, then forward the information to gateways to re-route the data path. Figure 9 illustrates handover with gateway relocation. After X2 tunnel establishment, the target eNB sends a path switch request to the C.E. entity.Then C.E. determines that the M-GW is relocated (target M-GW); next, C.E. allocates new parameters for the target M-GW. Then it sends a Session control message to the source M-GW and the target M-GW. In the next step, C.E. sends a Path switch to respond to the message from the target M-GW to the target eNB. The target eNB releases the X2 tunnel and creates a GTP tunnel to the  
Figure 8: Three main steps of handover procedure with gateway relocation in proposed 5G concept: (**a**) establishing X2 tunnel, (**b**) inter M-GW tunnel, and (**c**) switching destination GW. Figure 7: The mobility with gateway relocation in (**a**) 4G and (**b**) proposed 5G concept. target M-GW, and an inter-GW tunnel is also established. C.E. sends the U.E. context release message to inform the handover's success to the source eNB and triggers the release of resources. In the final step, C.E.