a single channel wireless digital communication network has a cellular topology which includes a central unit controlling communications with a plurality of remote units in a star configuration . network access is synchronously controlled through a time division multiplexed cycle of variable total duration having an up - link phase of a variable number of fixed size time slots , each pre - assigned by reservation by a remote unit , and a down - link phase of a variable number of variable size slots which are adaptively utilized . the cu adaptively manages all slot assignments according to a variety of parameters . ru up - link slot reservations are confirmed by the cu in a variety of ways . during the up - link phase , ru &# 39 ; s which did not reserve a slot on the previous up - link cycle are temporarily suspended and are then polled or periodically tested for re - entry . a repeater unit having a back - to - back coupled ccu - tu pair operates as a minicell within the major cell where major cell coverage is not broad enough to reach all major cell tu &# 39 ; s .