Uplink data transmission in LTE
The mapping of transport channels and UL control information (UCI) to physical channels is a task of the physical layer (PHY). Furthermore reference signals are provided by the physical layer which do not transfer any higher layer information.
Logical channel mapping is provided by the MAC layer.
Physical channel for data and signaling from higher layers:
- Physical Uplink Shared Channel, PUSCH.
- Physical Random Access Channel, PRACH.
Physical channels with UL control – related signaling:
- Physical Uplink Control Channel, PUCCH.
and signals with no information of higher layers:
- Demodulation Reference Signals (DRS).
- Sounding Reference Signal (SRS).
The baseband signal representing the physical uplink shared channel is defined in terms of the following steps:
- modulation of scrambled bits to generate complex-valued symbols
- transform precoding to generate complex-valued symbols
- mapping of complex-valued symbols to resource elements
- generation of complex-valued time-domain SC-FDMA signal for each antenna port.
PUSCH transmission takes place on frequency – consecutive resource elements. PUSCH is used to transport higher layer data and UCI if needed.