  This paper studies the outage probability and the throughput of
amplify-and-forward relay networks with wireless information and energy
transfer. We use some recent results on finite block-length codes to analyze
the system performance in the cases with short codewords. Specifically, the
time switching relaying and the power splitting relaying protocols are
considered for energy and information transfer. We derive tight approximations
for the outage probability/throughput. Then, we analyze the outage probability
in asymptotically high signal-to-noise ratios. Finally, we use numerical
results to confirm the accuracy of our analysis and to evaluate the system
performance in different scenarios. Our results indicate that, in
delay-constrained scenarios, the codeword length affects the outage
probability/throughput of the joint energy and information transfer systems
considerably.
