Contents
- 1 What is logical channel?
- 2 What are the different types of logical channels and how these differ from the physical channel?
- 3 Which layer support logical channel prioritisation?
- 4 How many channels are there in LTE?
- 5 Which channel is used for downlink scheduling?
- 6 Which layer handles DRX in LTE?
- 7 What is demultiplexing and multiplexing in transport layer?
- 8 Can a logical channel be multiplexed into a transport block?
- 9 How is logical channel prioritization applied to uplink transmission?
What is logical channel?
A logical channel is defined by the type of information it carries and is generally classified as a control channel, used for transmission of control and configuration information necessary for operating an LTE system, or as a traffic channel, used for the user data.
What are the different types of logical channels and how these differ from the physical channel?
There are three categories into which the various data channels may be grouped. Physical channels: These are transmission channels that carry user data and control messages. Logical channels: Provide services for the Medium Access Control (MAC) layer within the LTE protocol structure.
Which layer support logical channel prioritisation?
MAC layer
The MAC layer is responsible for mapping between logical channels and transport channels, multiplexing and demultiplexing of upper layer PDUs, scheduling air interface resources in both uplink and downlink, error correction through HARQ, priority handling between UEs by means of dynamic scheduling, and priority …
Which is the specific transport channel that is not mapped to any logical channel?
Random Access Channel
Random Access Channel (RACH): A specific transport channel that is not mapped to any logical channel. It transmits relatively small amounts of data for initial access or, in the case of RRC, state changes.
What is the purpose of logical channels in LTE?
Logical channels define what type of data is transferred. These channels define the data-transfer services offered by the MAC layer. Data and signalling messages are carried on logical channels between the RLC and MAC protocols.
How many channels are there in LTE?
3.3. The MAC layer uses the services offered by the physical layer in terms of using the transport channels. The LTE transport channels are: Broadcast Channel (BCH), Downlink Shared Channel (DL-SCH), Paging Channel (PCH), Multicast Channel (MCH), Uplink Shared Channel (UL-SCH), and Random Access Channel (RACH).
Which channel is used for downlink scheduling?
1 Dynamic downlink scheduling. The base station schedules downlink transmission on PDSCH dynamically using DCI Format 7-1A to 7-1F.
Which layer handles DRX in LTE?
In addition, the MAC layer handles the semi-persistent scheduling (SPS) procedure and the discontinuous reception (DRX) procedure. The SPS procedure is used to increase the cell capacity for a voice service, and the DRX procedure is used to reduce the power consumption of the UE.
What is the purpose of transport channels in LTE?
Transport channels: The physical layer transport channels offer information transfer to Medium Access Control (MAC) and higher layers. Logical channels: Provide services for the Medium Access Control (MAC) layer within the LTE protocol structure.
How many LTE channels are there?
LTE radio channel bandwidths
| Radio Channel Bandwidths Specified in LTE | |
|---|---|
| Channel Bandwidth | Number of Resource Blocks |
| 1.4 MHz | 6 |
| 3 MHz | 15 |
| 5 MHz | 25 |
What is demultiplexing and multiplexing in transport layer?
This process is called multiplexing. At the destination, received message is unwrapped and constituent messages (viz messages from hike and whatsapp application) are sent to appropriate application by looking to the destination the port number. This process is called demultiplexing. Similarly, B can also transfer the messages to A.
Can a logical channel be multiplexed into a transport block?
Multiple logical channels of different priorities can be multiplexed into the same transport block using the MAC multiplexing functionality. Except for the case when the uplink scheduling grant provides resources sufficient to transmit all data on all logical channels, the multiplexing needs to prioritize between the logical channels.
How is logical channel prioritization applied to uplink transmission?
Based on the uplink transmission resource grant message signalled on the PDCCH, the UE has to decide on the amount of data for each logical channel to be included in the newMAC PDU, and, if necessary, also to allocate space for a MAC Control Element. The Logical Channel Prioritization procedure is applied when a new transmission is performed.
How are logical channels mapped to physical channels?
Each logical channel is mapped onto one or more basic physical channels in a predefined manner. A basic physical channel is defined by a set of resources using the one and the same TS in each TDMA frame over the full hyperframe.