We present a case of design and implementation of a high-speed burst QPSK (Quaternary Phase Shift Keying) receiver. Since the PSK modulation carries its information through the phase, the baseband digital receiver can recover transmitted symbol from the received phase. The implemented receiver estimates symbol time and frequency offset using sampled data over 32 symbols without transmitted symbol information, and embedded RAM is used for received phase delay over estimation time. The receiver is implemented using about 92,000 gates of Samsung KG75 SOG library which uses 0.65 µm CMOS technology. The fabricated chip test result shows that the receiver operates at 40 MHz clock rate on 5.6 V, which is equivalent to the 40 Mbps data rate.

In this paper, we evaluate the average bit error rate (BER) and bits per symbol (BPS) performances of CDMA system employing the adaptive modulation according to the position of mobile station since the performance of CDMA system is highly dependent on user location especially in the downlink, and further we evaluate the overall performance by considering the user distribution at the level of cell. To evaluate the performance of the considered system in the forward link, we derive the distribution of the received signal to noise ratio (SNR) by Mobile Station located at arbitrary cell position with which we investigate the average BER and BPS performances of the common shared channel, one of the downlink channels of beyond IMT-2000 systems such as 1xEV-DO, 1xTEME and HSPDA. As a result, we observe that the CDMA system adopting the adaptive modulation can get about 2.47 bits per symbol at the cell level, while satisfying the required BER performance over all cell area.