Multistage interference canceller

A method of tentative decision in an interference canceller which includes an interference canceller unit including a despreader, a channel estimation unit, a despreading unit which inputs received signals or error and interference replica signals from a previous stage, a first synthesis unit which synthesizes a signal output from the despreading unit, a decision unit which evaluates a signal output from the first synthesis unit, a spreader, a spreading unit which inputs a decision output signal from said decision unit and the estimated channel value from said despreading unit, and a second synthesis unit which synthesizes the signal output from the spreading unit and outputs an estimated interference residual signal, the method of tentative decision comprising the steps of:

• switching of decision operations by said decision unit of the said interference canceller unit;
• comparing in said decision unit the total amplitude of a received symbol vector output from the first synthesis unit with the total amplitude of the estimated channel value output from the channel estimation unit;
• executing by the decision unit a hard decision when the total amplitude of the received symbol vector output from the first synthesis unit is equal to or greater than the total amplitude of the estimated channel value, or executes soft decision when the total amplitude of the received symbol vector output from the first synthesis unit is less than the total amplitude of the estimated channel value.