Parallelism versus Latency in Simplified Successive-Cancellation Decoding of Polar Codes

Seyyed Ali Hashemi, Marco Mondelli, Arman Fazeli, Alexander Vardy, John Cioffi, Andrea Goldsmith

Research output: Contribution to journalArticlepeer-review


This paper characterizes the latency of the simplified successive-cancellation (SSC) decoding scheme for polar codes under hardware resource constraints. In particular, when the number of processing elements P that can perform SSC decoding operations in parallel is limited, as is the case in practice, the latency of SSC decoding is O(N1-1/μ + N/P log2 log2 N/P), where N is the block length of the code and μ is the scaling exponent of the channel. Three direct consequences of this bound are presented. First, in a fully-parallel implementation where P = N/2, the latency of SSC decoding is O(N1-1/μ), which is sublinear in the block length. This recovers a result from our earlier work. Second, in a fully-serial implementation where P = 1, the latency of SSC decoding scales as O(N log2 log2 N). The multiplicative constant is also calculated: we show that the latency of SSC decoding when P = 1 is given by (2 + o(1))N log2 log2 N. Third, in a semi-parallel implementation, the smallest P that gives the same latency as that of the fully-parallel implementation is P = N1/μ. The tightness of our bound on SSC decoding latency and the applicability of the foregoing results is validated through extensive simulations.

Original languageEnglish (US)
JournalIEEE Transactions on Wireless Communications
StateAccepted/In press - 2021

All Science Journal Classification (ASJC) codes

  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics


  • Codes
  • Complexity theory
  • Decoding
  • Error probability
  • Hardware
  • latency
  • Polar codes
  • Polar codes
  • successive-cancellation decoding
  • Wireless communication


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