Adaptive M-QAM modulation over Nakagami fading channels

M. S. Alouini, A. Goldsmith

Research output: Contribution to conferencePaperpeer-review

74 Scopus citations


We study the performance of constant-power variable-rate M-QAM schemes over Nakagami fading channels. We obtain closed-form expressions for the outage probability, spectral efficiency and average bit-error-rate (BER) assuming perfect channel estimation and negligible time delay. For a target BER of 10-3, the spectral efficiency of adaptive continuous rate M-QAM comes within 5 dB of the Shannon capacity limit, and adaptive discrete rate M-QAM comes within 6.2 dB of this limit. Nonadaptive BPSK suffers a large spectral efficiency penalty relative to these adaptive techniques. We also analyze the impact of time delay on the BER of adaptive M-QAM. Results show that systems with low BER requirements will be more sensitive to time delay, but will still operate satisfactorily if the delay is below a critical value.

Original languageEnglish (US)
Number of pages16
StatePublished - 1997
Externally publishedYes
EventProceedings of the 1997 IEEE Global Telecommunications Mini-Conference - Phoenix, AZ, USA
Duration: Nov 3 1997Nov 8 1997


OtherProceedings of the 1997 IEEE Global Telecommunications Mini-Conference
CityPhoenix, AZ, USA

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering
  • Global and Planetary Change


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