An Enhanced NOMA-based Frameless Slotted ALOHA Scheme for IoT-Satellite
Terrestrial Relay Networks
Abstract
The low earth orbit (LEO) satellite Internet of Things (IoT) has
attracted widespread attention as an effective complement to terrestrial
IoT. However, given the large number of service terminals, it is
essential to design an access scheme that satisfies high capacity and
low latency. In this work, a non-orthogonal multiple access based
enhanced frameless slotted ALOHA (NOMA-EFSA) scheme is proposed for the
access of massive IoT terminals through a LEO satellite terrestrial
relay network. In this scheme, terminals are categorized into free,
backlogged, and pseudo-backlogged states. Terminals in different states
transmit data packets at discrete power levels according to specific
rules and the relay decodes them using inter-slot and intra-slot
successive interference cancellation (SIC). Most importantly, an effect
of imperfect channel state information (CSI) is considered, and
signature codes are employed to mitigate the power collision in
multi-terminal transmission within this scheme. The Markov chain is used
to derive the lower bound of the system throughput and the upper bound
of the number of backlogged terminals, while taking into account the
performance loss caused by satellite link outage. Moreover, simulation
results confirm the aforementioned analysis and show that the proposed
scheme outperforms remarkably the existing enhanced frameless slotted
ALOHA (EFSA) scheme in terms of throughput and the number of backlogged
terminals.