Coexistence of OFDM transmissions with different sampling rates, subcarrier spacing, symbol duration, bandwidths, but a constant FFT size, all with the same integer ratio (downclocking or upclocking) N=2, 4, 8 . . . Now called different numerology. Problem of Time alignment due to the presence of alternating long CP and short CPs in a slot. At the slot level the transmissions are aligned, but not at the symbol level. The application proposes to send after the first symbol for N=1 a so-called Time Alignment Period of same duration for each transmission in order allegedly to allow the network nodes to synchronize their timings or clocks without interfering with the transmission or reception of any symbols or CPs of other transmissions.