Basic Function of Uplink & Downlink Transport Channel in LTE

Uplink Transport Channel:

Purpose: Facilitates the transmission of user data from the User Equipment (UE) to the eNodeB (base station).
Channels: Includes the Physical Uplink Shared Channel (PUSCH) for user data and the Physical Uplink Control Channel (PUCCH) for control information.
Data Transmission: Carries information such as user-generated data, acknowledgments, and control signals from the UE to the network.

Downlink Transport Channel:

Purpose: Enables the transmission of data from the eNodeB to the User Equipment (UE).
Channels: Comprises the Physical Downlink Shared Channel (PDSCH) for user data, the Physical Broadcast Channel (PBCH) for system information, and the Physical Downlink Control Channel (PDCCH) for control information.
Data Delivery: Delivers user-specific data, broadcast information, and control signals from the network to the UE.

Downlink Transport ChannelBroadcast Channel (BCH)

A fixed TF
Used for transmission of parts of BCCH, so called MIB

Paging Channel (PCH)

Used for transmission of paging information from PCCH
Supports discontinuous reception (DRX)

Downlink Shared Channel (DL-SCH)

Main transport channel used for transmission of downlink data in LTE
Used also for transmission of parts of BCCH, so called SIB
Supports discontinuous reception (DRX)

Multicast Channel (MCH)

Used to support MBMS

Uplink Transport Channel

Uplink Shared Channel (UL-SCH)

Uplink counterpart to the DL-SCH

Random Access Channel(s) (RACH)

Transport channel which doesn’t carry transport blocks
Collision risk

Basic Function of Uplink & Downlink Transport Channels in LTE

In LTE, transport channels are used to transfer data between the User Equipment (UE) and the Evolved NodeB (eNB). They handle both user data and control information in both the uplink (from UE to eNB) and downlink (from eNB to UE). These channels play a key role in the communication process by defining how and where data is transmitted.

Downlink Transport Channels

PDSCH (Physical Downlink Shared Channel): Carries user data from the eNB to the UE. It is the primary transport channel for downlink data transmission, and the eNB schedules its use based on available resources.
PBCH (Physical Broadcast Channel): Broadcasts critical system information such as cell identity and network configurations, allowing UEs to connect to the network.
PDCCH (Physical Downlink Control Channel): Carries control information, such as scheduling assignments and resource allocation, to guide the UE on how to receive data on the PDSCH.
PHICH (Physical Hybrid-ARQ Indicator Channel): Sends feedback on whether the data received by the UE was successfully decoded or if retransmission is needed.

Uplink Transport Channels

PUCCH (Physical Uplink Control Channel): Transmits control information from the UE to the eNB, such as scheduling requests, acknowledgment signals, and channel quality indicators (CQI).
PUSCH (Physical Uplink Shared Channel): Used to carry user data from the UE to the eNB, similar to the PDSCH in the downlink.
PRACH (Physical Random Access Channel): Used by the UE to initiate communication with the eNB, especially for initial access, handovers, or re-establishing lost connections.

Conclusion

The uplink and downlink transport channels in LTE ensure efficient transmission of both user data and control signaling. By managing how data is sent and received, these channels enable seamless communication, efficient resource allocation, and reliable network performance.