Energy efficiency performance in RIS-based integrated satellite–aerial–terrestrial relay networks with deep reinforcement learning

EURASIP Journal on Advances in Signal Processing

Table 1 Abbreviations

SatCom	Satellite communication
ISATRNs	Integrated satellite–aerial–terrestrial relay networks
FSO	Free-space optics
RF	Radio frequency
STNs	Satellite terrestrial networks
RIS	Reconfigurable intelligent surfaces
SDMA	Space division multiple access
NOMA	Non-orthogonal multiple access
OP	Outage probability
IoT	Internet of things
ML	Machine learning
DRL	Deep reinforcement learning
DDQN	Double deep Q-network
LSTM	Long short-term memory
DDPG	Deep deterministic policy gradient
MIMO	Multiple input multiple output
SER	System ergodic rate
ULA	Uniform linear array
WDM	Wavelength division multiplexing
EGC	Equal-gain combing
AWGN	Additive white Gaussian noise
BF	Beamforming
DF	Decode-and-forward
SR	Shadowed-Rician
SNR	Signal-to-noise ratio
FSL	Free-space loss
GEO	Geosynchronous earth orbit
i.i.d	Independent and identically distribution