How does 5G HARQ enhance the latency and throughput performance compared to 4G?

2 How does HARQ work in 4G?

In 4G, HARQ uses a variant called chase combining, which means that the retransmitted packet is identical to the original one. The receiver adds the two packets together to enhance the signal quality and decode the data. However, this method has some limitations, such as the need for a fixed retransmission delay and a fixed number of retransmission attempts. Moreover, chase combining does not exploit the channel quality information (CQI) feedback from the receiver, which indicates the optimal modulation and coding scheme for the current channel conditions.

3 How does HARQ work in 5G?

In 5G, HARQ uses a variant called incremental redundancy, which means that the retransmitted packet contains different bits of information than the original one. The receiver combines the two packets using a rateless coding scheme to decode the data. This method has several advantages over chase combining, such as the ability to adapt the retransmission delay and the number of retransmission attempts according to the channel conditions and the data traffic. Moreover, incremental redundancy exploits the CQI feedback from the receiver, which enables the transmitter to adjust the modulation and coding scheme for each packet.

4 Why does HARQ enhance the latency performance of 5G?

One of the main benefits of HARQ in 5G is that it reduces the latency, or the time it takes for a data packet to travel from the transmitter to the receiver. This is because incremental redundancy allows for a shorter retransmission delay and a lower number of retransmission attempts than chase combining. Furthermore, incremental redundancy uses a rateless coding scheme, which means that the receiver can decode the data as soon as it receives enough bits, without waiting for a fixed number of packets. This improves the responsiveness and reliability of 5G applications, such as online gaming, cloud computing, and virtual reality.

5 Why does HARQ enhance the throughput performance of 5G?

Another benefit of HARQ in 5G is that it increases the throughput, or the amount of data that can be transmitted in a given time. This is because incremental redundancy allows for a higher data rate and a lower error rate than chase combining. Moreover, incremental redundancy uses the CQI feedback from the receiver, which enables the transmitter to select the most suitable modulation and coding scheme for each packet. This optimizes the spectral efficiency and the power consumption of 5G networks, which can support more users and devices with higher quality of service.