What is HARQ process in LTE?
Hybrid automatic repeat request (hybrid ARQ or HARQ) is a combination of high-rate forward error correction (FEC) and automatic repeat request (ARQ) error-control. In standard ARQ, redundant bits are added to data to be transmitted using an error-detecting (ED) code such as a cyclic redundancy check (CRC).
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 RTT timer in LTE?
Simple way to understand: the HARQ Round Trip Time (RTT) timer is defined for UE to sleep during HARQ RTT. When decoding DL TB for one HARQ fails, UE can next retransmission TB after at least HARQ RTT sub frames. While HARQ RTT timer is running, UE need not monitor PDCCH.
Why there is no Phich in 5G?
PHICH is present in LTE but is not required in NR. PHICH channel is used in LTE to handle uplink re-transmissions and are tightly coupled to use of synchronous hybrid-ARQ protocol, but as the HARQ protocol is asynchronous in NR in both downlink as well as uplink. Hence the PHICH is not required in NR.
What is 5G HARQ?
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 LTE?
The redundancy version tells the UE, about amount of redundancy added into the codeword while turbo encoding. There can be 4 different redundancy versions in LTE corresponding to new transmission, 1st, 2nd or 3rd re-transmission. Number of bits = 2.
What is redundancy version in 5G?
Similar to 4G, HARQ operation and the corresponding rate matching operation of 5G LDPC codes is controlled by redundancy version (rv) from 0 to 3. Each redundancy version corresponds to a certain column position of the base graph which divides the base graph excluding punctured two columns into four chunks.
What is the formula for HARQ process ID in LTE?
In LTE, there is no specific formula is defined in the 3GPP specification, but following can be one of the simplest rule in LTE case. Does the reciever (eNodeB in LTE case) need to know exact HARQ process ID?
What is the HARQ processor number?
To keep track of each HARQ process even when they are not running in order, the sender and reciever in the HARQ process should know the exact HARQ process number for each transmission/reception of the HARQ data. For this, DCI carries the field called HARQ Processor number.
What is HARQ codebook in 5G NR?
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 are the features of 5G HARQ?
UE Sends the ACK/NACK for corresponding PDSCH in PUSCH/PUCCH. On the very high level, 5G HARQ supports following features: Multiple HARQ process (upto 16) is supported per UE and there has to be separate feedback for each HARQ Process.