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Ranging in IEEE 802.16 systems is used to synchronize an uplink or to request an uplink bandwidth. The base station sends a ranging response message as a positive acknowledgment of a successfully received code. However, the base station does not provide a negative acknowledgment; hence, a mobile station is unable to determine if its ranging code is unsuccessfully transmitted. This paper proposes a negative acknowledgment method based on a ranging slot indicator and the frame number of a ranging response message. The results of the performance analysis show that the proposed method can reduce the delay of a code retransmission.