Testing the CMHK SIM card I have to see how fast it can run 
🗒️ Related Information
Device: Samsung Galaxy S23, roaming with 5G SA enabled
Time: 2025-08-23
Roaming: Shenzhen, Luohu
Local: Hong Kong, Wong Tai Sin
🚀 Speedtest test
| Roaming |
Local |
 |
 |
| Roaming |
Local |
 |
 |
🎬 FAST test
| Roaming |
Local |
 |
 |
⏬ iPerf3 TCP single-thread speed test (single 30-second test)
| Node |
Roaming download(Mbps) |
Retransmits |
Latency(ms) |
Local download(Mbps) |
Retransmits |
Latency(ms) |
| 🇭🇰 Hong Kong DMIT T1 |
142 |
1 |
62.05 |
210 |
0 |
20.91 |
| 🇭🇰 Hong Kong RFC JINX |
231 |
15 |
64.50 |
225 |
136 |
21.25 |
| 🇭🇰 Hong Kong RFC CTC |
189 |
0 |
60.00 |
330 |
0 |
16.70 |
| 🇯🇵 Tokyo RFC JP1 T1 |
45.1 |
5 |
265.13 |
104 |
242 |
206.77 |
| 🇯🇵 Tokyo BAGE CTC |
150 |
3 |
108.70 |
144 |
0 |
73.21 |
| 🇸🇬 Singapore RFC T1 |
150 |
10 |
99.44 |
281 |
0 |
45.82 |
| 🇺🇸 Los Angeles DMIT T1 |
65 |
21 |
306.77 |
273 |
20 |
252.90 |
| 🇺🇸 Los Angeles RFC T1 |
75.2 |
0 |
303.83 |
41.4 |
608 |
465.59 |
🗒️ Summary
RoamingCompared with local use, roaming adds 40-60ms of latency (Guangdong). Latency may not match a good proxy route, but it wins on convenience. Mainland roaming appears to be capped at 300Mbps