in other control channel of the frame structure the cell id allows the user equipments 920 to identify the base station 910 and a particular sector of the base station 910 if sectoring is used note that for each frame type the cell id is different to the legacy user equipments 920 the frames of the first frame type appear as legacy frames from a first legacy cell and the frames of the second frame type appear as legacy frames from a second legacy cell different from the first legacy cell even though in actuality the frames are from the same base station 910 the cell id can be associated with a particular base station or a combination of the base station and a particular sector in a1120 the base station 910 forms the interlaced frames by interlacing the frames of the plurality of frame types the interlacing is such that the downlink portion of a frame of one frame type does not overlap with an uplink portion of a frame of any other frame type conversely an uplink portion of the frame of the one frame type does not overlap with a downlink portion of the frame of any other frame type this is explained with reference to fig6 which illustrates a legacy base station 910 that has been modified to transmit the interlaced frames for simplicity of explanation the legacy base station in fig6 is assumed to form interlaced frames from frames of two frame types u2014 type a and type b u2014 both of which are modified versions of the legacy frame structure the frame of type a is referred to as u201c frame a u201d and the frame of type b is referred to as u201c frame b.