Pilot Symbol Parameter Optimization Based on Imperfect Channel State Prediction for OFDM Systems

The optimization of pilot symbol parameters can improve the spectral efficiency of adaptive modulation for orthogonal frequency division multiplexing (OFDM) systems, since pilot symbols impose an overhead on the system consuming power and bandwidth. An optimal pilot symbol assisted adaptive modulation (PSAAM) scheme for OFDM systems is proposed that maximizes spectral efficiency by adapting the power and constellation size of each subcarrier based on employing imperfect channel state information (CSI) at the transmitter. The pilot symbol power and spacing is also optimized in this scheme. A suboptimum scheme that decreases computational complexity without perceivable loss in performance is also presented. The optimality of minimum mean square error (MMSE) channel prediction for OFDM systems expressed in terms of a lower bound on spectral efficiency is approached. It is proved that the rectangular pilot pattern with equi-spaced and equal power pilot tones achieves the minimum MSE of the channel prediction in addition to having the advantage of simplifying PSAAM design. Numerical results show the importance of optimal pilot parameter adjustment for rapidly fading channels.

[1]  Kjell Jørgen Hole,et al.  Impact of channel prediction on adaptive coded modulation performance in Rayleigh fading , 2004, IEEE Transactions on Vehicular Technology.

[2]  José F. Paris,et al.  Impact of channel estimation error on adaptive modulation performance in flat fading , 2004, IEEE Transactions on Communications.

[3]  Yong-Hwan Lee,et al.  Optimum pilot pattern for channel estimation in OFDM systems , 2005, IEEE Transactions on Wireless Communications.

[4]  A. Olfat,et al.  Optimum power and rate adaptation with imperfect channel estimation for MQAM in rayleigh flat fading channel , 2005, VTC-2005-Fall. 2005 IEEE 62nd Vehicular Technology Conference, 2005..

[5]  M. Abramowitz,et al.  Handbook of Mathematical Functions With Formulas, Graphs and Mathematical Tables (National Bureau of Standards Applied Mathematics Series No. 55) , 1965 .

[6]  L. Hanzo,et al.  Adaptive multicarrier modulation: a convenient framework for time-frequency processing in wireless communications , 2000, Proceedings of the IEEE.

[7]  Charles R. Johnson,et al.  Matrix analysis , 1985, Statistical Inference for Engineers and Data Scientists.

[8]  Brian M. Sadler,et al.  Optimal pilot placement for channel tracking in OFDM , 2002, MILCOM 2002. Proceedings.

[9]  Georgios B. Giannakis,et al.  Capacity maximizing MMSE-optimal pilots for wireless OFDM over frequency-selective block Rayleigh-fading channels , 2004, IEEE Transactions on Information Theory.

[10]  Rick S. Blum,et al.  Adaptive OFDM Systems With Imperfect Channel State Information , 2006, IEEE Transactions on Wireless Communications.

[11]  Arne Svensson,et al.  An Introduction to Adaptive QAM Modulation Schemes for Known and Predicted Channels , 2007, Proceedings of the IEEE.

[12]  Stephen P. Boyd,et al.  Convex Optimization , 2004, Algorithms and Theory of Computation Handbook.

[13]  Norman C. Beaulieu,et al.  Optimum Pilot Symbol Assisted Modulation , 2007, IEEE Transactions on Communications.

[14]  Georgios B. Giannakis,et al.  Adaptive PSAM accounting for channel estimation and prediction errors , 2005, IEEE Transactions on Wireless Communications.

[15]  A. Goldsmith,et al.  Adaptive multicarrier modulation for wireless systems , 2000, Conference Record of the Thirty-Fourth Asilomar Conference on Signals, Systems and Computers (Cat. No.00CH37154).

[16]  Andrea J. Goldsmith,et al.  Degrees of freedom in adaptive modulation: a unified view , 2001, IEEE Trans. Commun..

[17]  Andrea J. Goldsmith,et al.  Adaptive coded modulation for fading channels , 1998, IEEE Trans. Commun..

[18]  John G. Proakis,et al.  Digital Communications , 1983 .

[19]  Daniel Zwillinger,et al.  CRC standard mathematical tables and formulae; 30th edition , 1995 .

[20]  J. Cavers.  An analysis of pilot symbol assisted modulation for Rayleigh fading channels (mobile radio) , 1991 .

[21]  Norman C. Beaulieu,et al.  Pilot Symbol Assisted Adaptive Modulation for OFDM Systems with Imperfect Channel State Information , 2010, 2010 IEEE Global Telecommunications Conference GLOBECOM 2010.

[22]  John M. Cioffi,et al.  Spatio-temporal coding for wireless communication , 1998, IEEE Trans. Commun..

[23]  Charles R. Johnson,et al.  Topics in Matrix Analysis , 1991 .

[24]  Yueming Cai,et al.  Optimal pilot patterns for OFDM system based on two-dimension sampling theory , 2003, International Conference on Neural Networks and Signal Processing, 2003. Proceedings of the 2003.

[25]  Abbas Jamalipour,et al.  Wireless communications , 2005, GLOBECOM '05. IEEE Global Telecommunications Conference, 2005..

[26]  Mohamed-Slim Alouini,et al.  An adaptive modulation scheme for simultaneous voice and data transmission over fading channels , 1999, IEEE J. Sel. Areas Commun..

[27]  Mohammad Shikh-Bahaei,et al.  Optimum Power and Rate Adaptation for MQAM in Rayleigh Flat Fading With Imperfect Channel Estimation , 2008, IEEE Transactions on Vehicular Technology.

[28]  Kaare Brandt Petersen,et al.  The Matrix Cookbook , 2006 .

[29]  Are Hjrungnes,et al.  Complex-Valued Matrix Derivatives: With Applications in Signal Processing and Communications , 2011 .

[30]  S. Sampei,et al.  Rayleigh fading compensation for QAM in land mobile radio communications , 1993 .