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

• Published in: IEEE transactions on wireless communications Vol. 8; no. 5; pp. 2247 - 2252
• Main Authors: Lamahewa, T., Sadeghi, P., Kennedy, R., Rapajic, P.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.05.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptation; Applied sciences; Channel capacity; Channel estimation; Channels; Constraint optimization; Delay; Detection, estimation, filtering, equalization, prediction; Exact sciences and technology; Fading; Feedback; Gaussian channels; Information, signal and communications theory; Mathematical models; Modulation, demodulation; Optimization; Pilot-symbol-assisted modulation; Pilots; power adaptation; Radiocommunications; Signal and communications theory; Signal processing; Signal, noise; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Time-varying channels; time-varying fading channel; Transmission and modulation (techniques and equipments); Transmitters; Transmitters. Receivers; Fading channels; Fading; Markov process; Lower bound; Time variable channel; Parameter estimation; Channel capacity; power adaptation; Information rate; Transmitter; time-varying fading channel; Information transmission; Optimization; Gaussian process; Channel estimation; Modulation; Pilot-symbol-assisted modulation; Open loop; Delay time; Signal to noise ratio
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2009.080526

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.