Arq block processing method for receiver of wibro system

A receiver of WIBRO(Wireless Broadband) systems and a method for processing ARQ blocks thereof are provided to manage effectively fuzzy timer by reducing the generation of useless fuzzy timers in a reception window. At least one or more ARQ(Automatic Repeat Request) block groups are generated by grouping ARQ blocks having successive BSNs(Block Sequence Number) among ARQ blocks, which are received through a frame in an ARQ reception window(503). It is determined whether or not the ARQ block groups are merged in a group list that the received ARQ groups are aligned(504). A fuzzy timer, which is set at a first ARQ group of the largest ARQ block group, is generated(505). When a time of the fuzzy timer is over, a start point of the reception window is slid up to a next ARQ block of the last ARQ block of the generated ARQ block groups(506). Then, an SDU(Service Data Unit) is generated from the ARQ block groups out of the reception window and the generated SDU is transmitted to an upper layer.