Estimators for Space-Time Block-Coded ARTM CPM in Aeronautical Mobile Telemetry

The use of space-time coded ARTM continuous phase modulation to solve the two-antenna problem in aeronautical mobile telemetry requires estimates of the parameters that define the propagation environment. The maximum likelihood estimator problem is defined and used to motivate reduced-complexity estimators suitable for use in a real system. A modified gradient descent algorithm performs the search required to find the delay parameters. An “inner” phase-lock loop operating with an “outer” frequency-lock loop computes decision-directed estimates of the frequency offset. Computer simulations were used to assess the impact on bit error rate performance introduced by the estimators. The simulation results show that the combined joint estimator for the delays, channel gains, and frequency offset imposes a 1.15-dB loss in performance.