1. A method for deciding a target packet error rate (PER) in a wireless communication system, the method comprising: setting a target packet error rate; comparing a variance of the target packet error rate (Δp(k)) with a previous target PER variance (Δp(k−1)); and updating a next target PER variance (Δp(k+1)) using an average capacity and a previous average capacity in accordance with the comparison result between the target PER variance (Δp(k)) and the previous target PER variance (Δp(k−1)).