9.8 Reference Signals Overhead

The downlink reference signal overhead estimates are given in Table 9.13. We note that the relative overheads for non-MBSFN transmissions are higher for the case of an extended cyclic prefix. This is because the number of reference symbols in a subframe are the same between the normal and the extended cyclic prefix, while the total resources within a subframe for the extended cyclic prefix is 85.7% (12/14) of the normal cyclic prefix resources. The MBSFN reference signals are defined for the case of an extended cyclic prefix only as the multicell MBSFN channel experiences a larger delay spread relative to a single-cell non-MBSFN channel. The UE-specific reference signals are defined for a single antenna port with 7.14% (1/14) and 8.33% (1/12) overhead for normal and extended cyclic prefix respectively.

We note that the UE-specific reference signal overhead is more than a single antenna port cell-specific reference signal overhead. The reason for this is that cell specific reference signals are transmitted on all the resource blocks...