In wireless communication system, there is a large frequency bias between carrier frequency and local oscillating frequency. AFC is contributed to eliminate it. A traditional AFC adopts analog loop filter that must work consecutively. However, in W CDMA system, the pilot parts are discontinuous. A novel digital approach of AFC is presented. In this algorithm, we first estimate the fading channel to get the phases and amplitudes of the pilot part symbols, and then combine estimations of multiple paths in one slot length, i.e., obtain one decision variable in each slot. Finally, these judged variables adjust the local oscillating frequency to track the carrier frequency by NCO. The simulation results show that the new AFC algorithm is effective and credible.
Turbo code has drawn more and more attractions for high data rate transmission these years especially in W CDMA and CDMA2000 of the third generation mobile communications systems. In this paper, the simulation performance of turbo code under Rayleigh fading channel and additive white Gaussian channels are depicted. Comparison with the performance of convolutional code are made respect to different parameters, such as pilot length, interleaver size, frame length, mobile velocity and data rate, etc. Faithful results are drawn out.
The Enhanced Variable Rate Codec (EVRC) is a standard for the Speech Service Option 3 for Wideband Spread Spectrum Digital System, which has been employed in both IS-95 cellular systems and ANSI J-STC-008 PCS (Personal Communications Systems). This paper investigated the combination of turbo codes with Unequal Error Protection (UEP) and 16-QAM modulation for EVRC codec of Rate 1 to get power and bandwidth efficient coding scheme. The results show that the UEP system outperforms the Equal Error Protection (EEP) one by 1.45 dB at BER of 10 -5.
