10 ms latency? Huawei delivers in 4G
5G at Verizon and AT&T is delivering latency around 10 ms. Mei Meiyuan writes, "For 4G mode, the best round-trip radio latency is about 10ms for FDD and about 13ms for TDD model2). In theory, With short TTI, the best round-trip radio latency is about 2ms（FDD,2 OFDM symbols 8ms(TDD, 7 OFDM symbols under planning，model2)."
(Editor's note: Those measures are from the base station to the receiver. To reflect the real user experience, you must add the latency from the base station back to the relevant server. That's 20-50 milliseconds or much more. In the future, edge clouds will often reduce the combined latency to 20-30 ms total.)
Many politicians and salesmen still think 5G latency is much better than 4G latency. As the new equipment reaches the field, people will discover the difference in latency is only a few
milliseconds.
Both will be much lower than what is today in the field, but technology has advanced in 4G, not just 5G.
5G can get close to 1 ms in the lab using a short TTI, Transmission Time Interval. 4G using short TTI is only 1-2 ms longer. Short TTI was developed before 2010 and is included in the 3GPP standards for both 4G & 5G. Today's equipment, both 4G & 5G, does not support it. That will change. The illustration is from an Ericsson paper, which also has a good set of references. The fastest methods, on the left, are still in the lab.
Huawei has a goal for 4G "To be consistent with 5GNR in term of frequency utilization as much as possible."
The problem is when you get retransmissions in LTE. Then HARQ and ARQ add many ms due to how retransmissions have been implemented. You can compare it with Wi-Fi where multiple immediate retransmissions push other packets away immediately (hence the low OTA latency there). I call the ARQ/HARQ implementation "wrong by design" (but to be fair, ms latency was never the target of LTE). Anyway, this is fixed in several ways with NR, so 5G will deliver more constant, low latency. That said, LTE also gets upgraded with new features that will reduce latency. The interesting part is always what happens with the system capacity/latency/jitter under load. That's the real set of metrics that people should look at. Peak throughput and lab latency in unloaded conditions are for the marketing department.
Co-creator of world’s first quantum-safe mobile network. Mentoring start-up founders and execs. Consciousness, AI, Quantum, 5G. Father. Husband. Views are only my own and no reflection or connection to my employer.
5 年Dave Burstein We deployed the world’s first LTE smartgrid in 2011 at 11 ms RTT latency already using Athonet core network and Ericsson eNBs on 2.6 GHz TDD.