  This letter presents a complete framework Meeting-Merging-Mission for
multi-robot exploration under communication restriction. Considering
communication is limited in both bandwidth and range in the real world, we
propose a lightweight environment presentation method and an efficient
cooperative exploration strategy. For lower bandwidth, each robot utilizes
specific polytopes to maintains free space and super frontier information (SFI)
as the source for exploration decision-making. To reduce repeated exploration,
we develop a mission-based protocol that drives robots to share collected
information in stable rendezvous. We also design a complete path planning
scheme for both centralized and decentralized cases. To validate that our
framework is practical and generic, we present an extensive benchmark and
deploy our system into multi-UGV and multi-UAV platforms.
