LTE employs two distinct multiple access technologies to optimize performance in each direction. On the downlink the tower transmits to handsets using Orthogonal Frequency Division Multiple Access, which splits the available bandwidth into thousands of narrowly spaced 15 kHz subcarriers and assigns subsets of them to different users simultaneously. This approach is inherently resistant to multipath fading because each subcarrier experiences a flat channel even when the wideband channel is frequency selective. A cyclic prefix inserted before every OFDM symbol absorbs delayed reflections and prevents inter-symbol interference.