Explain LTE uplink (UL) channels.
There are very few uplink channels in LTE compare to legacy technology.
Uplink logical channels:
CCCH and DCCH is called Control channels – These LTE control channels is used to carry the different control plane information.
DTCH is called Traffic Channels – These traffic channels is used to carry the user plane data.
- Common Control Channel (CCCH): This channel is used for random access information, e.g. for actions including setting up a connection.
- Dedicated Control Channel (DCCH): This control channel is used for carrying user-specific control information, e.g. for controlling actions including power control, handover, etc.
- Dedicated Traffic Channel (DTCH) : This traffic channel is used for the transmission of user data.
Uplink transport channels:
- Random Access Channel (RACH): This is used for random access requirements.
- Uplink Shared Channel (UL-SCH): This transport channel is the main channel for uplink data transfer. It is used by many logical channels.
Uplink physical channels:
- Physical Uplink Control Channel (PUCCH) : The Physical Uplink Control Channel, PUCCH provides the various control signaling requirements. There are a number of different PUCCH formats defined to enable the channel to carry the required information in the most efficient format for the particular scenario encountered. It includes the ability to carry SRs, Scheduling Requests.
- Physical Uplink Shared Channel (PUSCH) : This physical channel found on the LTE uplink is the Uplink counterpart of PDSCH
- Physical Random Access Channel (PRACH) : This uplink physical channel is used for random access functions. This is the only non-synchronized transmission that the UE can make within LTE. The downlink and uplink propagation delays are unknown when PRACH is used and therefore it cannot be synchronized.The PRACH instance is made up from two sequences: a cyclic prefix and a guard period. The preamble sequence may be repeated to enable the eNodeB to decode the preamble when link conditions are poor.