Model-based pilot and data power adaptation in PSAM with periodic delayed feedback

  • Authors:
  • Tharaka A. Lamahewa;Parastoo Sadeghi;Rodney A. Kennedy;Predrag B. Rapajic

  • Affiliations:
  • Australian National University, Canberra, ACT, Australia;Australian National University, Canberra, ACT, Australia;Australian National University, Canberra, ACT, Australia;University of Greenwich at Medway, Kent, United Kingdom

  • Venue:
  • IEEE Transactions on Wireless Communications
  • Year:
  • 2009

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Abstract

We consider the optimum design of pilot-symbol-assisted modulation (PSAM) schemes with feedback. The received signal is periodically fed back to the transmitter through a noiseless delayed link and the time-varying channel is modeled as a Gauss-Markov process. We optimize a lower bound on the channel capacity which incorporates the PSAM parameters and Kalman-based channel estimation and prediction. The parameters available for the capacity optimization are the data power adaptation strategy, pilot spacing and pilot power ratio, subject to an average power constraint. Compared to the optimized open-loop PSAM (i.e., the case where no feedback is provided from the receiver), our results show that even in the presence of feedback delay, the optimized power adaptation provides higher information rates at low signal-to-noise ratios (SNR) in medium-rate fading channels. However, in fast fading channels, even the presence of modest feedback delay dissipates the advantages of power adaptation.