TABLE OF CONTENTS We noted that the downlink reference signals employ a hybrid TDM/FDM approach. In principle, a similar approach can be envisaged for uplink reference signals. However, the uplink access is based on single-carrier FDMA and frequency-multiplexing reference signals with data transmissions would violate the single-carrier property resulting in increased PAPR/CM. Therefore, the uplink reference signals are strictly time-multiplexed to assure the single-carrier property of SC-FDMA.
Another difference relative to downlink reference signals is that uplink reference signals are always UE-specific. The two types of reference signals supported on the uplink include demodulation reference signals (DMRS) used for channel estimation for PUSCH or PUCCH demodulation and sounding reference signals (SRS) used to measure the uplink channel quality for channel sensitive scheduling. The uplink demodulation reference signals for normal cyclic prefix and extended cyclic prefix cases are shown in Figures 9.18 and 9.19 respectively. The demodulation reference signals for PUSCH are transmitted in the middle of the slot in symbol with l = 2, 3 for the extended and normal cyclic prefix respectively. For PUCCH format 1, 1A and 1B, the demodulation reference signals are transmitted in three symbols ( l = 2, 3, 4) for the normal cyclic prefix and two symbols ( l = 2, 3) for the extended cyclic prefix. For PUCCH format 2, 2A and 2B, the demodulation reference signals are transmitted in two symbols ( l = 1, 5) for the normal cyclic prefix. For PUCCH...
