Tsinghua University Tsinghua University Operators of Long Term Evolution (LTE) networks have been suffering from IPv4 address shortages and are forced to migrate to IPv6. Many operators prefer to build new LTE networks based on IPv6. However, at present there are still a lot of IPv4-only mobile terminals. A large number of high-quality applications are also in the IPv4-only Internet. There exist needs from IPv4 users to access IPv4 Internet across an IPv6-only LTE network. This document describes a tunneling mechanism that enables the IPv4 users to connect to the IPv4 Internet through an IPv6-only LTE network. Port-restricted public IPv4 addresses are assigned to eNodeBs to remove the NAT functionality on the PGW, which helps to offload the processing burden of PGW. The eNodeB is extended to allocate private IPv4 addresses to UEs, as well as the private- public IPv4 address translation.