Pankaj Das

Publications (5)0 Total impact

• Conference Proceeding: Effects of Channel Estimation Error and Nonlinear HPA on the Performance of OFDM in Rayleigh Channels with Application to 802.11n WLAN.

  David W. Chi, Mishal Al-Gharabally, Pankaj Das
  WCNC 2008, IEEE Wireless Communications & Networking Conference, March 31 2008 - April 3 2008, Las Vegas, Nevada, USA, Conference Proceedings; 01/2008
• Conference Proceeding: Effects of Nonlinear Amplifier and Partial Band Jammer in OFDM with Application to 802.11n WLAN

  David W. Chi, Pankaj Das
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  ABSTRACT: In this paper, we analyze the combined effects of nonlinear distortion and partial band jamming in an OFDM system through a Rayleigh fading channel. In addition to the effects of nonlinearity and jamming, the system is also subject to the channel estimation error. The nonlinear distortion is produced by a high power amplifier (HPA) located at the transmitter. The jammer is assumed to transmit a collection of single tone jamming signals which have a frequency off set with respect to the desired signal. The analytical model is then extended based on IEEE 802.11n standard. Finally, the simulation results are compared with the theoretical results.
  Military Communications Conference, 2007. MILCOM 2007. IEEE; 12/2007
• Conference Proceeding: An Intercarrier Interference Reduction Receiver for OFDM Systems in Time Varying Channels

  Mishal Al-Gharabally, Pankaj Das
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  ABSTRACT: In this paper, we propose a scheme to improve the performance of orthogonal frequency division multiplexing (OFDM) systems when operating in time varying channels. When the channel is time varying, the orthogonality among the subcarriers of a transmitted OFDM symbol is destroyed, causing intercarrier interference, and degrading the system performance. The proposed scheme aims to effectively reduce the effect of intercarrier interference. The advantages of the proposed scheme are shown via analysis and simulation.
  Military Communications Conference, 2007. MILCOM 2007. IEEE; 11/2007
• Conference Proceeding: OFDM Receiver Performance in Fading Channels and The Effects Of The Phase Noise Distribution with Imperfect Channel Estimation

  Mohamed Jalloh, Pankaj Das
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  ABSTRACT: The time-varying nature of multipath channels in Orthogonal Frequency Division Multiplexing (OFDM) systems causes intercarrier interference (ICI) and complicates the channel estimation at the receiver. The introduction of the local oscillator phase noise further destroys the orthogonality between subcarriers, thus increasing the ICI contribution. In this paper, we investigate the combined effects of channel estimation errors and receiver oscillator phase noise. Furthermore, the common phase error (CPE) is also accounted for in the OFDM system. Using M-QAM modulation in Rayleigh fading channels, we also compare the system performance when the phase noise process assumes different distributions, and present analytical results for illustration, followed by simulation results for validation.
  Military Communications Conference, 2007. MILCOM 2007. IEEE; 11/2007
• Article: Performance of OFDM Systems in Rayleigh Fading Channels with Phase Noise and Channel Estimation Errors

  Mohamed Jalloh, Mishal Al-Gharabally, Pankaj Das
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  ABSTRACT: This paper provides the analysis of the joint effects of oscillator phase noise and channel estimation errors on the performance of OFDM in Rayleigh Fading channels. The contribution of the above impairments to the signal distortion is mathematically described, and a proof of the distribution of the Intercarrier Interference (ICI) is also provided. Analytic and simulation results for the bit error rate (BER) of the system, with and without channel estimation errors, are then presented.
  MILCOM.