the scrambling sequence is unique and known to both the base station and the wtru the scrambling code may be generated in a number of ways or selected in accordance with criterion that the distance between the scrambling code and the all u201c zero u201d sequence is maximized fig5 is a block diagram of a wtru 500 in accordance with the third embodiment the wtru 500 includes a transceiver 502 a decoder 504 a descrambler 506 and a controller 508 the transceiver 502 receives a bit sequence of a data block from the base station 400 the decoder 504 performs fec decoding on the received bit sequence as in the prior art if the data block does not include a pan field and therefore the bits corresponding to the header was not scrambled at the base station 400 the decoder 504 may succeed in decoding however if the data block includes a pan field and therefore the bits corresponding to the header was scrambled at the base station 400 the received bit sequence will be rejected due to having too many bit errors if the received bit sequence is rejected the received bits corresponding to the header are descrambled i e moculo 2 added with the scrambling sequence by the descrambler 506 the received bit sequence with the descrambled header portion of the bit sequence is then decoded again by the decoder 504 if the second fec decoding is successful the controller 508 detects that a pan field is included in the data block in accordance with a fourth embodiment a modified hcs is used to indicate the presence of the pan field a radio block for data.