Two-phase random access procedure for LTE-A Networks

Ray Guang Cheng, Zdenek Becvar, Yi Shin Huang, Giuseppe Bianchi, Ruki Harwahyu

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Simultaneous random access attempts from massive machine-type communications (mMTC) devices may severely congest a shared physical random access channel (PRACH) in mobile networks. This paper presents a novel two-phase random access (TPRA) procedure to deal with the congestion caused by mMTC devices accessing the PRACH. During the first phase, the TPRA splits the mMTC devices into smaller groups according to a preamble selected randomly by the devices. Then, in the second phase, each group of devices is assigned with a dedicated channel to complete the random access procedure. The proposed concept allows a base station to adjust the number of dedicated channels in real-time according to the actual network load. We then present an analytical model to estimate the access success probability and the average access delay of the TPRA. Finally, we propose a simple formula to determine the optimal number of random access resources for the second phase of the proposed TPRA. Simulations are carried out to validate the analytical models and to demonstrate the benefits of the TPRA compared to competitive techniques.

Original languageEnglish
Article number8667033
Pages (from-to)2374-2387
Number of pages14
JournalIEEE Transactions on Wireless Communications
Issue number4
Publication statusPublished - Apr 2019


  • analytical model
  • massive machine-type communications
  • Random access


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