osed-loop MIMO. For open-loop MIMO, the midamble can be used to calculate the channel quality indicator. The MIMO midamble is transmitted in every radio frame in the second downlink subframe. The midamble signal occupies the first OFDM symbol in a DL type-1 or type-2 subframe. For the type-1 subframe, the remaining five consecutive OFDM symbols form a type-3 subframe. For a type-2 subframe, the remaining six consecutive OFDM symbols form a type-1 subframe. The MIMO midamble signal transmitted by the BS antenna is described as follows: (9-20) Where the ak coefficients modulate sub-carriers in the midamble symbol and are defined as follows: 2.18{1-2G([k+u+D(NFFT)]mod NFFT)} k=Nuser otherwise (9-21) where k is the sub-carrier index 0 k < Nused - 1, Nused is the number of used sub-carriers, N is a number of transmit antennas, G(x) is the Golay sequence (0 X < 2047), NFFT is the FFT size, is a shift value (0 < < 127) = IDcell mod 256, D(NFFT) is an FFT size-specific offset, g is the BS transmit antenna index ranging from 0 to N - 1, N is the number of BS transmit antennas, parameter S = 0 for k (Nused - 1)/2 and = 1 for k > (Nused - 1)/2, and n is the frame number [2]. The IDcell Golay sequences are pair of sequences with complementary autocorrelation functions. They were introduced as a pair of complementary binary sequences, which have the property that the sum of their autocorrelation functions equals zero for all time shifts, except zero. Mathematically complementary sequences a(n) and b(n) of length N can be defined by Ra(k) + Rb(k) = OAK#0 and Ra (k) + Rb(k) = 2N, k = 0 where Ra(k) and Rb(k) are the autocorrelation functions of a (n) and b(n) sequences. Binary complementary sequences are typically of length 2nd although some even lengths that can be expressed as a sum of two squares were introduced. Several recursive and non-recursive methods for generating complementary sequences have been proposed. The recursive methods are based on the following algorithm: an = [an - 1, - il and bn = [an - 1,-bn il where the 