Design and implementation of an underlay control channel for NC-OFDM-based networks

Ratnesh Kumbhkar, Gokul Sridharan, Narayan B. Mandayam, Ivan Seskar, Sastry Kompella

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Scopus citations

Abstract

This paper designs an underlay control channel for noncontiguous-OFDM-based cognitive networks. Noncontiguous OFDM (NC-OFDM) provides a fast and flexible manner of accessing disjoint parts of the spectrum and is ideally suited for dynamic spectrum access. While similar to OFDM, NC-OFDM explicitly restricts transmission to only certain subcarriers that are free of incumbent transmissions. In particular, this paper considers designing a control channel for a cognitive network consisting of multiple point-to-point (p2p) links that operate over a wide bandwidth that might encompass some primary transmissions. In such a scenario, control channel becomes vital not only to share basic transmission parameters but also to aid timing and frequency recovery of NC-OFDM transmission; a nontrivial problem in itself. The proposed design is a low-power underlay transmission that spans the entire bandwidth regardless of any incumbent transmissions and uses direct sequence spread spectrum (DSSS). The control channel operates in one of two modes. The first mode aids timing and frequency recovery through a two-step process, while the second mode is used for control data transmission. To enable multiple access, the p2p links use orthogonal pseudo-noise (PN) sequences. The proposed control channel is implemented on USRPs in the ORBIT testbed using GNU Radio. Experimental results suggest robust timing and frequency offset recovery even in the presence of concurrent primary transmissions and support for about 10 to 20kbps over a 1 MHz bandwidth at an uncoded symbol-error-rate of about 10-2 under typical operating conditions.

Original languageEnglish (US)
Title of host publication2016 50th Annual Conference on Information Systems and Sciences, CISS 2016
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages228-233
Number of pages6
ISBN (Electronic)9781467394574
DOIs
StatePublished - Apr 26 2016
Event50th Annual Conference on Information Systems and Sciences, CISS 2016 - Princeton, United States
Duration: Mar 16 2016Mar 18 2016

Publication series

Name2016 50th Annual Conference on Information Systems and Sciences, CISS 2016

Other

Other50th Annual Conference on Information Systems and Sciences, CISS 2016
CountryUnited States
CityPrinceton
Period3/16/163/18/16

All Science Journal Classification (ASJC) codes

  • Information Systems
  • Computer Networks and Communications

Keywords

  • Control channel design
  • Frequency offset estimation
  • Noncontiguous-OFDM
  • PN sequences
  • Timing recovery

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    Kumbhkar, R., Sridharan, G., Mandayam, N. B., Seskar, I., & Kompella, S. (2016). Design and implementation of an underlay control channel for NC-OFDM-based networks. In 2016 50th Annual Conference on Information Systems and Sciences, CISS 2016 (pp. 228-233). [7460506] (2016 50th Annual Conference on Information Systems and Sciences, CISS 2016). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/CISS.2016.7460506