Struggles with 5G power levels risk damaging Japan’s 5G experience

In this new analysis, Opensignal has observed substantially lower signal strength experienced by our users in Japan when connected to 5G, compared with other East Asian markets — Hong Kong, South Korea and Taiwan. As we have seen in Europe and the U.S. lower signal power levels often mean a worse 5G experience for users. However, 4G signal strength in Japan is comparable to other markets which indicates Japan’s operators face a specific challenge with 5G deployments.

To focus our 5G analysis and make it comparable across markets we analyzed 5G and looked at connections that used either the 3.5 GHz band (n77 and n78) or the 4.5 GHz band (n79). The 3.5 GHz band is commonly used across many markets — however, the 4.5 GHz band — while a similar type of mid-band 5G spectrum — is mainly used by Japan’s operators. We have excluded measurements from operators that have relied on low-band spectrum, like the 700 MHz band, to deploy their 5G services as that is not as commonly deployed across these markets.

In the case of Synchronization Signal Reference Signal Received Power (SS RSRP), which quantifies 5G signal strength, Japan scored -106.1 dBm on average. Based on Tutela’s signal strength thresholds (free registration required), this would place this market in the Weak signal strength category (higher than -115 dBm but below -105 dBm) — however, narrowly misses the Fair category (higher than -105 dBm but below -95 dBm).  By contrast, we observed significantly higher results in other analyzed markets.

However, looking at the 4G / LTE RSRP results, Japan’s 4G signal strength was comparable to most of the other markets. Hong Kong, Japan and Taiwan’s average 4G signal strength varied between -95.4 and 93.4 dBm. But there was a noticeable difference between these three and South Korea where our users connected to 4G services with an average signal strength of -89 dBm.However, all four markets rated as Good in terms of 4G signal strength.

Japan’s operators must work within power emission guidelines designed to protect other services. For example, to avoid interference between 5G and fixed satellite frequencies in the 3400-4200 MHz range or to avoid issues with altimeters near airports. In addition, NTT DoCoMo has 5G spectrum holdings in two bands — 3.5 GHz band and 4.5 GHz, and the latter is the higher frequency where, due to physics means received, power levels would reduce more quickly further from a cell tower than on lower frequency bands such as the 3.5GHz band.

Lower 5G signal power correlates with slower 5G Download Speed 

As 5G signal strength reduced, our users also saw that their 5G mobile experience greatly deteriorated across different categories. Based on Tutela’s Network Coverage analysis tool, we combined the Excellent (above -85 dBm) and Good (higher than -95 dBm but below than -85 dBm) categories into Good or better (above -95 dBm), to simplify our analysis. We also merged the Weak (higher than -115 dBm but below -105 dBm), Very Weak (higher than -120 dBm but below -115 dBm) and Dead Zone (below -120 dBm) categories into Weak or worse (below -105 dBm).

For Japan, average download 5G speeds with a weak or worse signal were 62.4% slower than the speeds seen with a Good or better signal. Our users in other East Asian markets witnessed slightly smaller decreases in average 5G download speeds between these two categories — ranging from 52.3% in South Korea to 59.1% in Taiwan.

We also looked at the distributions of 4G and 5G readings by signal strength categories across East Asian markets. Only in Japan did we see more than 50% of 5G readings with a Weak or worse signal. This is a significantly higher proportion compared to other markets — 8.5% in Hong Kong, 3.9% in South Korea and 9.7% in Taiwan. Only 19.4% of readings in Japan placed in the Good or better category, as opposed to 64.3-74.8% in the other markets.

Turning to 4G readings, Japan’s distribution results were more aligned with its East Asian peers. We observed 16.6% of readings with a Weak or worse 4G signal in Japan, close to 13.6% in Hong Kong or 18.3% in Taiwan. In South Korea, only 5.9% of 4G signal readings were rated as Weak or worse. Japan, Hong Kong and South Korea all exceeded 50% of Good or better 4G signal strength readings (with the latter reaching even 70.1%), while Taiwan saw a lower proportion of 46.1%.

Limited signal strength for 5G also has had an impact on 5G Availability levels in Japan — the proportion of time Opensignal users with a 5G device and a 5G subscription had an active 5G connection. In the first quarter of 2022, our users in Japan connected to 5G networks only 4.1% of the time. Other markers in East Asia saw much higher scores — ranging from 21.7% for Hong Kong to 30.9% in South Korea. Again, 4G connections in Japan seemed less impacted by signal strength, as all four markets achieved nearly perfect scores in Availability (which takes 3G, 4G and 5G into consideration), between 98.8% and 99.8%.

Stronger 5G signals should improve the 5G experience in Japan

While Japan had a slower start with rolling out its 5G networks compared to other global or regional markets, it has been catching up with 5G global leaders. However, it did not make it to the top 15 global markets in any of our 5G categories in Opensignal’s latest Benchmarking the Global 5G Experience published in March 2022. Meanwhile, its regional peers South Korea and Taiwan featured in every 5G speed category, while also appearing in some 5G experiential metrics along with Hong Kong. All three markets made it to the top 15 for both global 5G extent categories — 5G Reach and 5G Availability.

If Japan’s operators were able to match the power levels Opensignal users have seen in other East Asian markets, it would help Japan’s operators to further close the 5G experience gap with leading international 5G markets.