What is ACK and NACK in LTE?
What is ACK and NACK in LTE?
As you may guess from the terminoloty itself, ACK NACK repetition is a method in which a sender (UE in current specification) transmit ACK/NACK multiple times in a row. In an aspect, we can say it is similar concept to TTI Bundling.
What is a HARQ process?
HARQ process relies upon receiving ACK for the packets. If the sender sends a packet and then waits for the ACK to send another packet, it is called a SAW(stop and wait) process. It increases the round trip time ( sender and receiver processing time + propagation delays).
What is MIB Phich?
PHICH is a control channel on LTE downlink, that is used to indicate the reception of PUSCH transmission from a mobile/UE. The number of PHICH groups is a cell level parameter and it is also transmitted as part of MIB, so as to assist the UE in getting the control channel mapping.
Which channel is used for ACK NACK feedback in uplink in 5G?
Index Terms— 5G, NR, PUCCH As a fundamental building component to enable NR system, physical Uplink Control Channel (PUCCH) is mainly utilized to convey Uplink Control Information (UCI), including [4]: HARQ-ACK (Hybrid Automated Repeat Request- Acknowledgement) feedback in response to downlink data transmission.
What is ACK NACK in network?
An Acknowledgement (ACK) or Negative Acknowledgement (NACK) is a short message sent by the receiver to the transmitter to indicate whether it has correctly or incorrectly received a data packet, respectively.
What is MCS in LTE?
MCS (Modulation and Coding Scheme) defines how many useful bits can be transmitted per Resource Element (RE). MCS depends on radio link quality. The better quality the higher MCS and the more useful data can be transmitted.
What is HARQ ACK codebook?
In 5G NR, 3GPP specification has defined HARQ Codebook to provide the feedback to base station for Downlink data transmission i.e., PDSCH Data. UE Sends the ACK/NACK for corresponding PDSCH in PUSCH/PUCCH.
What is the difference between HARQ and ARQ in LTE?
The HARQ is a technique when the receiver gets a new data with some errors then it tries to make correction if the error is minor, but if the error is not minor then it sends re-transmission request to the sender. The ARQ mechanism takes care of residual errors which passed from HARQ.
What is the Phich in LTE?
Physical channel HybridARQ Indicator Channel
PHICH stands for Physical channel HybridARQ Indicator Channel. Simply put, it is a secially designed downlink only channel which carries ACK or NACK for the PUSCH received by the network.
What is Pdcch?
PDCCH is a physical channel that carries downlink control information (DCI) and it has characteristics as described below. Mapped to the first L OFDM symbols in every downlink subframe. Multiple PDCCH are supported and a UE monitors a set of control channels. Modulation Scheme is QPSK.
What is SSB in 5G?
SS Block(SSB) stands for Synchronization Signal Block and in reality it refers to Synchronization/PBCH block because Synchnronization signal and PBCH channel are packed as a single block that always moves together. Synchronization Signal : PSS (Primary Synchronization Signal), SSS (Secondary Synchronization Signal)
What ACK means?
Acknowledge. ACK is also used to mean “Acknowledge,” as in to confirm receipt or understanding of a message. This way of using ACK is probably based on military and law-enforcement usage of the word “Acknowledge” in communications.
Why is there a delay between data transmission and ACK / NACK?
In LTE TDD, the time association between the data transmission and the ACK/NACK cannot be maintained due to the variable numbers of downlink and uplink subframes being present in a frame. The uplink and downlink delay between data and ACK/NACK is dependent on the TDD subframe configuration.
How many bits are required for ACK / NACK signal?
The ACK/NACK signal consists basically of one bit per UE especially when MIMO channel transmission is not employed. However, if the destination is indicated by also sending the UE ID, the required number of bits per UE becomes significantly larger such as 17 assuming a 16-bit UE ID.
Which is ACK / NACK corresponding to multiple DL sub frames?
Ack/Nack corresponding to multiple DL sub frame PRACH Preamble Format 0,1,2,3 0,1,2,3,4(Short RACH) PRACH Configuration Special Slot usage N/A DwPTS : RS, Data and Control UpPTS : SRS and Short RACH HARQ Timing K = 4 (fixed) DL : Async, UL :Sync K = varying depending on Subframe Config DL : Async, UL : Sync Ack/Nack Feedback Mode
How is a HARQ ACK / NACK transmitted in a retransmission?
The terminal attempts to decode the received signal, using soft combining of previous retransmissions, and then it transmits a HARQ ACK/NACK in uplink subframe n + 4. It must be noted that the start of an uplink subframe at the terminal is offset by the timing advance relative to the start of the corresponding downlink subframe at the terminal.
