  Polar codes achieve outstanding error correction performance when using
successive cancellation list (SCL) decoding with cyclic redundancy check. A
larger list size brings better decoding performance and is essential for
practical applications such as 5G communication networks. However, the decoding
speed of SCL decreases with increased list size. Adaptive SCL (ASCL) decoding
can greatly enhance the decoding speed, but the decoding latency for each
codeword is different so A-SCL is not a good choice for hardware-based
applications. In this paper, a hardware-friendly two-staged adaptive SCL
(TA-SCL) decoding algorithm is proposed such that a constant input data rate is
supported even if the list size for each codeword is different. A mathematical
model based on Markov chain is derived to explore the bounds of its decoding
performance. Simulation results show that the throughput of TA-SCL is tripled
for good channel conditions with negligible performance degradation and
hardware overhead.
