racted antenna sequence of length 2048 as follows [2]: k mod D=g Otherwise (10-14) CHAPTER 10 The IEEE 802. 16m Physical Layer (Part II) where D is the sub-carrier decimation parameter transmitted in the AAI_SCD MAC control message, k is the sub-carrier index Nused 1, Nused is the number of used sub-carriers over the sounding symbol, G(x) is the Golay sequence of length 2048 bits (0<x<2047), NFFT is the FFT size, is a shift whose value is transmitted in the superframe header, offsetD(NFFT) is an offset whose value depends on the FFT size, and B is the group of sub-carrier indices allocated to the sounding channel. If sounding signals transmitted by users or antennas are separated using cyclic shifts, the sequence associated with the nth cyclic shift index is calculated as follows [2]: (10-15) Otherwise where P is the maximum cyclic-shift whose value is conveyed in the AAI_SCD MAC control message and 0 1 denotes the cyclic shift index. 10.3.4 Ranging Channel The ranging channel is used for uplink synchronization. The BS processes the received signal on the ranging channel to estimate the radio-link parameters, such as channel impulse response, SINR, and time of arrival, that are used for timing/frequency/power adjustment of the uplink transmissions from the MS. The ranging process consists of transmission of a deterministic sequence known as a ranging code over a number of OFDM symbols. The phase continuity of the received signal at the OFDM symbol boundaries is crucial to the ranging process. The ranging process is further classified into ranging for non-synchronized mobile stations (i.e., mobile stations that are not uplink-synchronized) and synchronized mobile stations (i.e., mobile stations that are uplink-synchronized with the BS). Note that in an OFDMA system, a mobile station cannot perform any uplink transmission prior to successful completion of the ranging procedures. A contention-based or non-contention based random access procedure is used for ranging. Contention-based random access is used for initial