e filter g(t) spans an integer K (overlapping factor) multiple length of symbol period TF = KT. It must be noted that real mathematics, the Balian-Low theorem in Fourier analysis states that there is no well-localized window func- tion or Gabor function either in time or frequency domain for an exact Gabor frame. Let g denote a square- integrable function on the set of real numbers, and consider the so-called Gabor system gm,n(x) = g(x-na)e2njmbx for integers m and n, and a,b>0 satisfying ab = 1. The Balian-Low - theorem states that if {8m,n:m,neZ} is an orthonormal basis for the Hilbert space L2(R), then either = 00 [ Note g(o) is the Fourier transform ofg(x)]. The Balian-Low theorem has been extended to exact Gabor frames. New Radio Access Physical Layer Aspects (Part 1) 339 and imaginary data values alternate on subcarriers and symbols, which is called offset QAM (OQAM). Since PAM symbols convey only one half of information content compared to QAM symbols, a data rate loss factor 2 is implicit. Nevertheless, the symbol period in FBMC is also halved to T/2 in order to compensate for the efficiency loss of OQAM modu- lation. Furthermore, CP is not essential anymore in FBMC due to the well-localized pulse shape. Filtering can use different overlap factors (i.e., K factor) to provide varying levels of OOB rejection. As K factor is reduced, the OOB characteristics have a spectrum-rejection profile similar to that of OFDM. The critical step for FBMC design is to implement filters for each subcarrier and to align multiple filters into a filter bank. One way to implement the filter bank is to design a prototype filter. Once the prototype filter is designed, the next step is to make a copy of the prototype filter and shift it to neighboring subcarriers as illustrated in Fig. 3.20. The comparison of the PSDs of the OFDM and FBMC signals is shown in Fig. 3.21. The FBMC signal was processed with overlapping factors K = 2 and 3. It is shown that with the increase of the overlapping factor, the OOB emissions of the FBMC sig