Channel uncertainty in ultra-wideband communication systems

Dana Porrat, David N.C. Tse, Şerban Nacu

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Channel uncertainty limits the achievable data rates of certain ultra-wideband systems due to the need to estimate the channel. The use of bursty duty-cycled transmission reduces the channel uncertainty because the receiver has to estimate the channel only when transmission takes place, but the maximum amount of burstiness and hence the possible reduction of channel uncertainty both depend on the spectral efficiency of the modulation scheme used. This general principle is demonstrated by comparing the channel conditions that allow duty-cycled direct-sequence spread spectrum (DSSS) and pulse position modulation (PPM) to achieve the additive white Gaussian noise (AWGN) channel capacity in the wideband limit. We show that duty-cycled DSSS systems achieve the wideband capacity as long as the number of independently faded resolvable paths increases sublinearly with the bandwidth, while duty-cycled PPM systems can achieve the wideband capacity only if the number of paths increases sublogarithmically. The difference is due to the fact that DSSS is spectrally more efficient than PPM and hence allows more bursty transmission.

Original languageEnglish
Pages (from-to)194-208
Number of pages15
JournalIEEE Transactions on Information Theory
Issue number1
StatePublished - Jan 2007
Externally publishedYes

Bibliographical note

Funding Information:
Manuscript received February 28, 2005; revised September 18, 2006. This work was funded in part by the Army Research Office (ARO) under Grant DAAD19-01-1-0477, via the University of Southern California. The material in this paper was presented in part at the 41st Annual Allerton Conference on Communication, Control, and Computing, Monticello, IL, October 2003. D. Porrat is with the School of Engineering and Computer Science, Hebrew University, Jerusalm 91904, Isreal (e-mail: D. N. C. Tse is with the Department of Electrical Engineering and Computer Science, University of California, Berkeley CA 94720-1770 USA (e-mail: S¸. Nacu is with Department of Statistics, Stanford University, Stanford, CA 94305 USA (e-mail: Communicated by R. R. Müller, Associate Editor for Communications. Color versions of Figs. 1, 2, and 4–7 are available online at http://ieeexplore. Digital Object Identifier 10.1109/TIT.2006.887063


  • Channel uncertainty
  • Direct sequence spread spectrum
  • Flash signaling
  • Pulse position modulation (PPM)
  • Spectral efficiency
  • Wideband communications


Dive into the research topics of 'Channel uncertainty in ultra-wideband communication systems'. Together they form a unique fingerprint.

Cite this