since the spreading algorithm is performed per OFDM symbol, for example, 14 times per subframe (TTI) in an LTE system, the number of QAM symbols per OFDM symbols has to be always the same. Unfortunately, this requirement is not satisfied when the LTE downlink pilot pattern is employed as the pilots are mapped in a diamond shape within the resource grid. To enable the symbol spreading, suited pilot pattern needs to be implemented, such as the pattern for the LTE uplink, which employs DFT spreading. In this case, there are either no pilots in an OFDM symbol, or an OFDM symbol consists exclusively of pilot symbols. This enables to employ spreading, but is unfortunately not implemented yet. Please compare the LTE uplink and downlink pilot allocation schemes for clarification.