Time-Asynchronous Robust Cooperative Transmission for the Downlink of C-RAN

Seok Hwan Park, Osvaldo Simeone, Shlomo Shamai Shitz

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


This letter studies the robust design of downlink precoding for cloud radio access network (C-RAN) in the presence of asynchronism among remote radio heads (RRHs). Specifically, a C-RAN downlink system is considered in which nonideal fronthaul links connecting two RRHs to a baseband unit (BBU) may cause a time offset, as well as a phase offset, between the transmissions of the two RRHs. The offsets are a priori not known to the BBU. With the aim of counteracting the unknown time offset, a robust precoding scheme is considered that is based on the idea of correlating the signal transmitted by one RRH with a number of delayed versions of the signal transmitted by the other RRH. For this transmission strategy, the problem of maximizing the worst-case minimum rate is tackled while satisfying per-RRH transmit power constraints. Numerical results are reported that verify the advantages of the proposed robust scheme as compared to the conventional nonrobust design criteria as well as noncooperative transmission.

Original languageEnglish (US)
Article number7546840
Pages (from-to)1444-1448
Number of pages5
JournalIEEE Signal Processing Letters
Issue number10
StatePublished - Oct 2016

All Science Journal Classification (ASJC) codes

  • Signal Processing
  • Electrical and Electronic Engineering
  • Applied Mathematics


  • Asynchronous transmission
  • cloud radio access network (C-RAN)
  • fronthaul latency
  • robust optimization


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