TR-221 provides technical architecture and equipment requirements for MPLS based mobile backhaul networks. It provides solutions and end-to-end reference architectures for transport services addressing control, user and management traffic in mobile networks. It also includes specifications for various transport scenarios that are depicted in this reference architecture. The intent of TR-221 is to promote the multi-vendor interoperability for equipments used in mobile backhaul networks based on MPLS. TR-221 may be used as a basis for conformance testing. 

With the increase of bandwidth demand per mobile user combined with the decrease of the average revenue per user, mobile operators and transport providers need to evolve their mobile backhaul networks to be faster and more efficient. MPLS provides the convergence of multiple backhaul technologies into one unified technology and supports more efficient use of network resources, reducing operational costs. TR-221 defined the use of MPLS in Mobile Backhaul access and aggregation networks and provided solutions for the transport of traffic in 2G, 3G and LTE mobile networks. It has created reference architectures for MPLS in Mobile Backhaul networks and included specifications for the various transport scenarios that are depicted in the reference architecture. The amendment addresses additional issues and features of the control, user and management planes that were not included in the original TR-221. This document is not changing the main content of TR-221, but rather adds functions to it. 

This provides a new amendment to TR-221 which includes specifications on timing (phase/frequency) synchronization, enhancements on scalability such as support of multi-area LSP signaling and BGP LSP routing. This amendment is applicable to address backhaul up through 3GPP Rel.11 and beyond.