Ultra-Reliable and Low-Latency Wireless Communications in the High SNR Regime: A Cross-Layer Tradeoff

Yalei Wang, Wei Chen, H. Vincent Poor

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Ultra-Reliable and Low-Latency Communications (URLLC) has attracted considerable attention because of its potential applications in factory automation, automated driving, and telesurgery anticipated for the era of the sixth-Generation (6G) networks. In URLLC with random channel gains and a hard delay constraint, the scheduling of backlogged queues and finite blocklength coding in the physical layer will make it very challenging to specify its performance limits. In this paper, we focus our attention on the asymptotic cross-layer analysis of URLLC when the Signal-to-Noise Ratio (SNR) is sufficiently high. More specifically, we find that a fundamental tradeoff exists among the service capability, latency, and error probability in the high SNR regime, which is characterized by a gain conservation equation. The main result of this work reveals that the sum of our defined service rate gain, real-time gain, and reliability gain is equal to one under the optimal policy. Numerical simulations are also exploited to validate that the derived gain conservation equation holds even with bounded random arrival.

Original languageEnglish (US)
Pages (from-to)149-162
Number of pages14
JournalIEEE Transactions on Communications
Issue number1
StatePublished - Jan 1 2022
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering


  • Ultra-reliable and low-latency communications (URLLC)
  • asymptotic analysis
  • cross-layer design
  • delay violation probability
  • finite blocklength coding
  • gain conservation equation
  • hard delay constraint
  • high SNR regime
  • zero delay communications


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