A channel estimator for use in a receiver node receiving signals from a plurality of user terminals wherein each user terminal is allotted a respective set of transmission subcarriers and respective test signal sequences for transmission over the channel to be estimated. The channel estimator has stored therein information as to the respective sets of transmission subcarriers allotted to the user terminals for transmission as well as the discrete spectra of the respective test signal sequences allotted to the user terminals. Upon receiving from a plurality of user terminals signals including the respective test signal sequences transmitted over the channel by using the respective sets of transmission subcarriers allotted thereto, the estimator generates the discrete spectrum of the combined test signal received and performs channel estimation as a function of the discrete spectrum of the combined test signal and the discrete spectra of the test signal sequences allotted to the user terminals. A frequency domain channel estimation is performed for a single carrier frequency division multiple access system.