Figure 8 shows the performance of both receivers for correlated fading on each tap exhibiting a Doppler spread of 40 Hz corresponding to a normalized Doppler spread of 0.01 at a data rate of 4 ksps.
With the DVB-T sampling rate of T s − 1 = 9. 14 MHz, this corresponds to a normalized Doppler spread of 20% of the subcarrier spacing.
A straight line is drawn when the normalized spread-F occurrence rate is equal to 0% as in Fig. 12.
Figures 12 and 13 show the post-sunset foF2 and h′F variations compared with the normalized spread-F occurrence rates at the four sites.
where (left { c_{l,i}^{k}right }) is the normalized spreading sequence (so as to make the autocorrelations of the signature sequences unity) of user k for the l t h symbol.
The normalized spread-F occurrence rate is defined as follows: p_{i} = frac{{m}_{i} }{{mathop sum nolimits_{i} {m}_{i} }} (2) mathop sum limits_{i} {p}_{i} = 1 (3)where p is the normalized FSF or RSF occurrence rate, m i is the number of FSF or RSF event occurrences when the foF2 or h′F is within a certain interval.
where P k is the chip energy of the k th user, c k = [c k (0), c k (1), ⋯, c k (M − 1)] is the normalized spreading code vector of the k th user, and Q1 = diag{q1, 0, q1, 1, …, q1, M − 1} denotes the channel matrix of the first user, whose diagonal elements are the channel frequency response given by q 1, m = ∑ l = 0 L 1 − 1 β 1 l e − j 2 π ml / M, m = 0, 1, ⋯, M − 1.
Such a normalized measure for geometric spreading is chosen since the effect of the excitation source on the energy density will be canceled out.
A normalized basic sequence generates a spreading model if for some, for all, and, (2.22).
