Carrier recovery and tracking performance for CDMA land mobile satellite links

The performance of carrier recovery and tracking for CDMA systems was evaluated in a realistic land mobile satellite channel as function of elevation angle and pilot channel signal-to-noise ratio. The carrier frequency is recovered by an AFC loop assuming a rough estimate of the carrier frequency is available. After frequency recovery and tracking is accomplished, the residual phase error is estimated by a feedforward structure. The performance results are presented in terms of the AFC loop acquisition time, the rms frequency error and the rms phase error. The results indicate that a two-step frequency acquisition strategy is useful to reach a good compromise between short acquisition time and low rms frequency error. The worst-case acquisition times of the AFC loop were achieved at low elevations, being below 297 ms at signal-to-noise ratios of 9 dB or higher. The worst-case frequency and phase errors were also found at low elevations, being 11.4 Hz and 23.3 degrees at 9 dB SNR, respectively.