OFDM or single-carrier block transmissions?

Zhengdao Wang, Xiaoli Ma, Georgios B. Giannakis

Research output: Contribution to journalArticlepeer-review

271 Scopus citations


We compare two block transmission systems over frequency-selective fading channels: orthogonal frequency-division multiplexing (OFDM) versus single-carrier modulated blocks with zero padding (ZP). We first compare their peak-to-average power ratio (PAR) and the corresponding power amplifier backoff for phase-shift keying or quadrature amplitude modulation. Then, we study the effects of carrier frequency offset on their performance and throughput. We further compare the performance and complexity of uncoded and coded transmissions over random dispersive channels, including Rayleigh fading channels, as well as practical HIPERLAN/2 indoor and outdoor channels. We establish that unlike OFDM, uncoded block transmissions with ZP enjoy maximum diversity and coding gains within the class of linearly precoded block transmissions. Analysis and computer simulations confirm the considerable edge of ZP-only in terms of PAR, robustness to carrier frequency offset, and uncoded performance, at the price of slightly increased complexity. In the coded case, ZP is preferable when the code rate is high (e.g., 3/4), while coded OFDM is to be preferred in terms of both performance and complexity when the code rate is slow (e.g., 1/2) and the error-correcting capability is enhanced. As ZP block transmissions can approximate serial single-carrier systems as well, the scope of the present comparison is broader.

Original languageEnglish (US)
Pages (from-to)380-394
Number of pages15
JournalIEEE Transactions on Communications
Issue number3
StatePublished - Mar 2004

Bibliographical note

Funding Information:
Paper approved by C. Tellambura, the Editor for Modulation and Signal Design of the IEEE Communications Society. Manuscript received August 16, 2001; revised April 3, 2003. This work was supported in part by the National Science Foundation (NSF) under Grant 01-0516, and in part by the Applied Research Laboratory/Collaborative Technology Alliance (ARL/CTA) under Grant DAAD19-01-2-011. This paper was presented in part at the IEEE Wireless Communications and Networking Conference, Orlando, FL, March 17–21, 2002.


  • Capacity
  • Coding
  • Diversity
  • Frequency-selective fading
  • Multicarrier
  • Orthogonal frequency-division multiplexing (OFDM)
  • Peak-to-average ratio (PAR)
  • Single carrier
  • Synchronization


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