LTE-Advanced has the same frame structure for both single-hop and relay based networks. However, the frame structure for relaying will accommodate the resource allocations of two hops, either in a centralized or distributed manner. Currently, there is no standardization for the relay frame structure.
Figure 10.4 shows a frame structure for relay-based LTE-Advanced that is similar to that of single hop with a slight difference. In Figure 10.4, the UL and the DL subframes are further organized into access and relay zones. This structure supports backwards compatibility, in addition to the communication over relay and access links. While the relay zone is used for the communication between the relay node and the eNB, the access zone is used for direct communication between the MSs and eNB or the MS and the relay node. The relay mode in LTE-Advanced is currently at its pre-draft stage. Hence, there is no detailed standardized description for the difference, if any, between Types 1 and 2 frame structure.