Evolved Packet System (EPS): The LTE and SAE Evolution of 3G UMTS

3.8 Uplink Scheme: SC-FDMA (FDD/TDD)

3.8.1 Uplink Physical Channel and Signals

An uplink physical channel corresponds to a set of resource atoms carrying information originating from higher layers. The following uplink physical channels are defined (Figure 3.57):

• Physical Uplink Shared Channel, PUSCH, used for uplink shared data transmission.
• Physical Uplink Control Channel, PUCCH. The PUCCH shall be transmitted on a reserved frequency region in the uplink. It is used to carry ACK/NACK, CQI for downlink transmission and scheduling request for uplink transmission.
• Physical Random Access Channel, PRACH.

An uplink signal is used by the physical layer but does not carry information originating from higher layers. The following uplink physical signals are defined:

• Reference signal.

3.8.2 SC-FDMA

The basic uplink transmission scheme is single-carrier transmission (SC-FDMA) with cyclic prefix to achieve uplink inter-user orthogonality and to enable efficient frequency–domain equalization at the receiver side. Frequency–domain generation of the signal, sometimes known as DFT-SOFDM (Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplex), is assumed and illustrated in Figure 3.58. This allows a relatively high degree of commonality with the downlink OFDM scheme and the same parameters, e.g. clock frequency, can be re-used.

The subcarrier mapping determines which part of the spectrum is used for transmission by inserting a suitable number of zeros at the upper and/or ...