Dual-Filter Architecture for Blind Feedback Recovery of the Symbol Timing in Bandlimited Optical Intensity Channels

Wilfried Gappmair*, Harald Schlemmer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Reliable recovery of transmission parameters is of paramount importance not only for radio frequency receivers, but also for optical wireless communication solutions. This paper discusses a feedback algorithm for recovering the symbol timing in the context of a bandlimited optical intensity link. The link is determined by a PAM scheme and pulse shaping with squared raised cosine or double jump functions. When preambles or pilot sequences are not available to the receiver, non-data-aided (blind) recovery concepts are useful for tracking smaller variations of the timing error affecting the payload data. The current state-of-the-art solution uses a Gardner detector with two samples per symbol, although this introduces a non-negligible amount of inter-symbol interference resulting in an error floor. To avoid this drawback, the authors propose a dual-filter approach which includes an appropriately designed filter operated in parallel to the receiver filter. Despite the additional complexity of the dual-filter architecture, the recovery loop is very simple and requires only one sample per symbol, representing the lowest degree of complexity in this respect. Open-loop characteristic, jitter performance, and acquisition behavior of the suggested recovery loop are investigated.
Original languageEnglish
Article number1411
Number of pages12
Issue number6
Publication statusPublished - Mar 2023


  • symbol timing recovery
  • optical wireless communications
  • intensity modulation
  • pulse shaping

ASJC Scopus subject areas

  • Signal Processing
  • Electrical and Electronic Engineering
  • Control and Systems Engineering
  • Hardware and Architecture
  • Computer Networks and Communications

Fields of Expertise

  • Information, Communication & Computing

Treatment code (Nähere Zuordnung)

  • Theoretical


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