  Future integrated terrestrial, aerial, and space networks will involve
thousands of Low Earth Orbit (LEO) satellites forming a network of
mega-constellations, which will play a significant role in providing
communication and Internet services everywhere, at any time, and for
everything. Due to its very large scale and highly dynamic nature, future LEO
satellite networks (SatNets) management is a very complicated and crucial
process, especially the mobility management aspect and its two components
location management and handover management. In this article, we present a
comprehensive and critical review of the state-of-the-art research in LEO
SatNets location management. First, we give an overview of the Internet
Engineering Task Force (IETF) mobility management standards (e.g., Mobile IPv6
and Proxy Mobile IPv6) and discuss their location management techniques
limitations in the environment of future LEO SatNets. We highlight future LEO
SatNets mobility characteristics and their challenging features and describe
two unprecedented future location management scenarios. A taxonomy of the
available location management solutions for LEO SatNets is presented, where the
solutions are classified into three approaches. For each of the reviewed
approaches, the "Issues to consider" section draws attention to important
points that should be considered in future LEO SatNets location management. To
identify the gaps, the current state of LEO SatNets location management is
summarized and the challenges facing future LEO SatNets location management are
discussed. Worthy research directions are recommended. This article is
providing a road map for researchers and industry to shape the future of LEO
SatNets location management.
