Performance Analysis of Cross-Tier Routing Strategy in Multitier LEO Satellite Constellation

With the rapid growth of global traffic and the construction of large-scale low-orbit satellites, the hybrid network of multitier LEO satellite has become the future trend, which also brings challenges to satellite routing. In this article, we propose a flexible satellite cross-tier routing method under the control of gateway, considering on-board processing ability and satellite congestion to realize low lantency routing. First, we model the multitier satellite constellations as marked Poission point process (MPPP), in which each tier follows Poission point process (PPP) distribution with marked different satellite queueing length. Then, the analytical expressions of routing outage probability, end-to-end delay are derived, considering search radius, packet arrival rate, routing distance and intertier distance. Finally, the search range expansion approach is proposed to solve the problem of traffic congestion, and the tradeoff between routing success probability and search range deflection angle is obtained. Numerical results show that the cross-tier routing mechanism can significantly reduce the routing outage probability under high load and reduce the end-to-end delay under medium load, respectively. In addition, the search range expansion approach can significantly reduce the routing outage probability without influencing the sum delay significantly. This work is expected to be instructive to the future sixth generation (6G) network.