In this letter, an algorithm that estimates one of the most important channel parameters, maximum Doppler frequency, fD, is proposed. The algorithm uses phase variations of received pilot signals, which is strongly related with fD in a fading environment. In addition, a phase variation measurement method for binary phase shift keying (BPSK) modulated signals is also proposed and it makes possible to estimate fD from BPSK modulated information signals as well as unmodulated pilot signals. The results show that the proposed algorithm is very simple and shows good performance over wide Doppler frequency range.

We propose an enhanced packet access scheme for IMT-2000/UMTS random access channel (RACH). In the proposed scheme, 2-level preamble detection threshold and 2-level message transmission power are used to mitigate the power imbalance in RACH. Simulation results demonstrate that the proposed scheme improves the interference characteristics of the conventional RACH and makes wider range of the detection threshold available.