A method and an apparatus of generating a signal for an initial ranging in an OFDMA(Orthogonal Frequency Division Multiple Access) system are provided to simply generate plural symbols with continuous phases irrespective of the number of symbol for the initial ranging by using a single mathematical equation. A ranging code generator(308) generates a ranging code. A ranging channel generator(310) modulates the ranging code and generates L symbols by phase-rotating the modulated ranging codes according to a symbol index and a sub-carrier index. The ranging channel generator maps the symbols on a constellation to the sub-carrier according to an index of the sub-carrier. A converter converts the mapped symbols into a time domain and generates sample data of the ranging symbol. A guard interval insertion unit(304) copies a tail portion of the sample data corresponding to the size of the guard interval, and inserts the copied portion in front of the sample data as the guard interval, such that the initial ranging signal is formed.
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