When it comes to mobile network speeds, most people only talk about the downlink direction. Few think about the uplink and what it’s capabilities are today. Relatively little has happened there since LTE was launched around a decade ago until recently.
The main challenge in the uplink direction is UE transmit power. A mobile device is limited to a transmit power of 23 dBm which is 0.2 Watts or 200 mW. That’s not very much to work with so in most cases there’s no chance of using a better modulation and coding scheme, let alone MIMO. So when LTE was launched, the LTE uplink was limited to 50 Mbit/s in a 20 MHz channel. This figure can be reached with 16QAM modulation and in practice, one can see such a speed if the device is very close to the base station, let’s say 50 meters or less and has a line of sight to the antenna. Without a line of sight or further away, data rates drop quite quickly and it is not uncommon to see data rates below 10 or even 5 Mbit/s in the uplink direction. Nothing to be done about that, 23 dBm is 23 dBm.
But in those rare line of sight scenarios, uplink power is not the limiting factor and the device could actually transmit faster. This is why later incarnations of the 3GPP standard have introduced two interesting uplink features: 64QAM and Uplink Carrier Aggregation. Both can be found in live networks these days and high end devices of the year 2019 usually come with support for Uplink CA. So I was very positively surprised when I made an uplink speed test at a favorable location recently at which I reached a sustained uplink data rate of 90 Mbit/s. That is quite something and I wished I’d see that more often as I don’t only consume data in the downlink direction but quite often send huge files in the gigabyte range in the uplink direction as well. And here’s the iperf log of my 80-90 Mbit/s uplink run:
08:04:34 martin@xxxxxxxx:~$ iperf3 -c ping-ams1.online.net -p 5204 -t 240 Connecting to host ping-ams1.online.net, port 5204 [ 4] local 192.168.43.250 port 43056 connected to 163.172.208.7 port 5204 [ ID] Interval Transfer Bandwidth Retr Cwnd [ 4] 0.00-1.00 sec 3.50 MBytes 29.3 Mbits/sec 0 270 KBytes [ 4] 1.00-2.00 sec 7.58 MBytes 63.6 Mbits/sec 0 588 KBytes [ 4] 2.00-3.00 sec 11.2 MBytes 93.8 Mbits/sec 0 1.07 MBytes [ 4] 3.00-4.00 sec 10.0 MBytes 83.9 Mbits/sec 0 1.61 MBytes [ 4] 4.00-5.00 sec 11.2 MBytes 94.4 Mbits/sec 0 2.14 MBytes [ 4] 5.00-6.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.67 MBytes [ 4] 6.00-7.00 sec 10.0 MBytes 83.9 Mbits/sec 0 3.13 MBytes [ 4] 7.00-8.00 sec 10.0 MBytes 83.9 Mbits/sec 164 2.32 MBytes [ 4] 8.00-9.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.52 MBytes [ 4] 9.00-10.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.71 MBytes [ 4] 10.00-11.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.86 MBytes [ 4] 11.00-12.00 sec 11.2 MBytes 94.4 Mbits/sec 0 2.98 MBytes [ 4] 12.00-13.00 sec 10.0 MBytes 83.9 Mbits/sec 38 2.14 MBytes [ 4] 13.00-14.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.26 MBytes [ 4] 14.00-15.00 sec 11.2 MBytes 94.4 Mbits/sec 0 2.35 MBytes [ 4] 15.00-16.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.42 MBytes [ 4] 16.00-17.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.47 MBytes [ 4] 17.00-18.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.50 MBytes [ 4] 18.00-19.00 sec 8.75 MBytes 73.4 Mbits/sec 1 1.76 MBytes [ 4] 19.00-20.00 sec 8.75 MBytes 73.4 Mbits/sec 0 1.85 MBytes [ 4] 20.00-21.00 sec 7.50 MBytes 62.9 Mbits/sec 0 1.94 MBytes [ 4] 21.00-22.00 sec 8.75 MBytes 73.4 Mbits/sec 0 2.02 MBytes [ 4] 22.00-23.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.07 MBytes [ 4] 23.00-24.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.10 MBytes [ 4] 24.00-25.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.12 MBytes [ 4] 25.00-26.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.13 MBytes [ 4] 26.00-27.00 sec 8.75 MBytes 73.4 Mbits/sec 0 2.14 MBytes [ 4] 27.00-28.00 sec 10.0 MBytes 83.9 Mbits/sec 0 2.14 MBytes