Variable threshold M-QAM with feedback delay over Nakagami-m fading channels

Sang Do Lee, Young-Chai Ko

Research output: Chapter in Book/Report/Conference proceedingConference contribution


In this paper, we propose an adaptive M-ary quadrature amplitude modulation (M-QAM) with variable threshold, which adapts the threshold of rate-region boundaries to the variation of feedback delay between the transmitter and the receiver, over independent and identically-distributed (i.i.d) Nakagami-m fading (NMF) channel. The proposed scheme exploits the estimation of instantaneous bit error rate (BER) which is based on the maximum a posteriori (MAP) criterion in [1]. Based on the proposed scheme, we derive the threshold adaptation algorithm to minimize the effect of the feedback delay on the spectral efficiency and the average BER. Numerical results show that our proposed scheme is more reliable to the feedback delay than conventional adaptive M-QAM with fixed thresholds.

Original languageEnglish
Title of host publicationIEEE Vehicular Technology Conference
Publication statusPublished - 2009 Dec 1
Event2009 IEEE 70th Vehicular Technology Conference Fall, VTC 2009 Fall - Anchorage, AK, United States
Duration: 2009 Sep 202009 Sep 23


Other2009 IEEE 70th Vehicular Technology Conference Fall, VTC 2009 Fall
CountryUnited States
CityAnchorage, AK



  • Adaptive modulation
  • BER estimation
  • MQAM
  • Threshold adaptation

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Computer Science Applications
  • Applied Mathematics

Cite this