Friday, May 17, 2013

Why LTE has 15Khz sub carrier spacing

One argument for adopting a 15 kHz subcarrier spacing for LTE was that it may simplify the implementation of WCDMA/HSPA/LTE multi-mode terminals. Assuming a power-of-two FFT size and a subcarrier spacing f = 15 kHz, the sampling rate fs = f · NFFT will be a multiple or sub-multiple of the WCDMA/HSPA chip rate fcr = 3.84 MHz. Multi-mode WCDMA/HSPA/LTE terminals can then straightforwardly be implemented with a single clock circuitry.In addition to the 15 kHz subcarrier spacing, a reduced subcarrier spacing flow = 7.5 kHz is also defined for LTE.


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