What is HARQ process in LTE?
What is HARQ process in LTE?
HARQ stands for Hybrid Automatic Repeat Request. HARQ = ARQ + FEC (Forward Error Correction)/Soft Combining. ARQ refers to Automatic Repeat Request i.e. if sender doesn’t receive Acknowledgement (ACK) before timeout, the receiver discards the bad packet and sender shall re-transmits the packet.
How many HARQ process in LTE TDD?
There are 8 uplink HARQ processes running on both UE and eNB with 4 processes delay. HARQ process length is same as a subframe (1 ms). When UE sends data to eNB, eNB decodes data and checks CRC. eNB then sends acknowledgement (ACK) or not-acknowledged (NACK) to UE after 4 subframes.
What is HARQ feedback?
The HARQ feedback channels are used to carry ACK/NACK information corresponding to downlink transmissions. The HARQ feedback channels start at predetermined time offsets relative to the corresponding DL transmissions and are frequency-division multiplexed with other control and data channels over an uplink subframe.
What is RV in HARQ?
Rv0 is first Transmission. Rv1 is second transmission for a HARQ Nack.
What is difference between ARQ and HARQ?
ARQ is an error control protocol. HARQ: 1. It works at Physical layer but controlled by MAC layer.
What is difference between ARQ and HARQ in LTE?
HARQ is performed in a lower layer of a layer where conventional ARQ is performed, and thus, errors are corrected by ARQ when the errors are not corrected by HARQ. In general, the retransmission of ARQ is carried out after reaching the maximum number of retransmission attempts of HARQ.
What is HARQ process in NR?
HARQ is a stop-and-wait protocol. Another packet is not sent while waiting for feedback on the current packet. Due to the round trip time, this results in underutilization of radio resources. 5G NR HARQ solves this by allowing multiple concurrent HARQ processes. Each process can have one packet pending an ACK.
What is HARQ 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 redundancy version in HARQ?
In addition to the NDI, HARQ-related downlink control signaling consists of the HARQ process number (3 bits for FDD, 4 bits for TDD) and the redundancy version (2 bits), both explicitly signaled in the scheduling assignment for each downlink transmission.
What is HARQ RTT timer?
What is HARQ RTT Timer? This parameter specifies the min amount of TTIs before a DL HARQ retransmission is expected by the UE. ( 3GPP TS 36.321 V8.0.0) Simple way to understand: the HARQ Round Trip Time (RTT) timer is defined for UE to sleep during HARQ RTT.
What is HARQ RTT timer in LTE?
What is the difference between ARQ and HARQ?
What is fast HARQ?
Fast HARQ Over Finite Blocklength Codes: A Technique for Low-Latency Reliable Communication. Abstract: This paper studies the performance of delay-constrained hybrid automatic repeat request (HARQ) protocols.
What is HARQ process in 5G?
How many HARQ process in 5G?
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. Multiple HARQ process (upto 16) is supported per UE and there has to be separate feedback for each HARQ Process.
What is Harq in 5G?
What is DRX and cDRX?
DRX (Discontinuous Reception) – CDRX (Connected Mode DRX) Even while there is no traffic between the network and UE, UE has to keep listening to Network. At least it should be ready to decode PDCCH. It means UE has to be “ON” all the time even when there is no traffic. But being ON all the time would drain the battery.
How does HARQ 5G work?
In 5G NR , HARQ operates at both MAC and PHY layers. Retransmissions occur at the MAC layer. PHY layer at the receiver combines one or more transmissions to increase the chances of correct decoding. The use of HARQ in 5G NR benefits URLLC and eMBB use cases.
What is DRX cycle in LTE?
DRX in the LTE sense means that the UE is not monitoring the PDCCH in the given sub frame and is allowed to go to power saving mode. As uplink is scheduled in downlink PDCCH, the DRX parameter impacts both uplink and downlink performance for a UE.
What is idle mode DRX in LTE?
DRX can be employed in both idle and connected modes in LTE, but the exact functionality differs to some extent. In idle mode, the DRX cycle is the same thing as the paging cycle, as the UE expects to only receive paging messages. The UE reads the paging channel at certain subframes within specific radio frames.
