Article

Iterative channel estimation and decoding for convolutionally coded anti-jam FH signals

Electr. Eng. Dept., Maryland Univ., College Park, MD
IEEE Transactions on Communications (Impact Factor: 1.98). 03/2002; DOI: 10.1109/26.983327
Source: IEEE Xplore

ABSTRACT An iterative algorithm for joint decoding and channel estimation
in frequency-hopping (FH) networks is proposed. In the proposed
algorithm, soft decoder outputs are used in the iterative estimation of
the time-varying variance of the additive interference resulting from
the sum of the thermal noise, partial-band noise jamming, and other-user
interference. The soft outputs are also used in the estimation of the
independent random carrier phases and multiplicative Rayleigh fading
coefficients in different frequency dwells. The estimation process is
further enhanced through the insertion of known symbols in the
transmitted data stream. The proposed iterative symbol-aided
demodulation scheme is compared with the coherent scenario, where the
channel state information is assumed to be known a priori at the
receiver, for both convolutionally coded and turbo coded FH systems. The
proposed iterative channel estimation approach is suited for slow FH
systems where the channel dynamics are much slower than the hopping
rate. This observation motivates the consideration of another robust
approach for generating the log-likelihood ratios for fast hopping
systems in additive white Gaussian noise channels. Simulation results
that demonstrate the excellent performance of the proposed algorithms in
various scenarios are also presented

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