Why Slow Internet Speed in Certain Period of Time in Japan?

I received a very interesting inquiry from a visitor to Japan, asking

In Japan, why is the data communication speed limited for 30 minutes from 12:15 to 12:45?
Is it a technical reason, or a cultural one?

This is seemingly easy question to answer, but actually, it can be deep.
Here on this article, I’d like to answer this question, and propose a solution to it.

This issue is caused by both a technical and a cultural reason.

If I would make a brief summary of the answer, it will be like this:

12:15 to 12:45 on weekday is the midst of lunch time for a large majority of people in Japan.
During that time, the people using their mobile phones increase rapidly.
The more people use the internet at the same time, the less data communication speed will be.

Let me be specific.

Bandwidth of all the network providers are limited for a certain amount. And, even when a large amount of data is being used at the same time, they have to provide data to each user under the limited bandwidth. That is why, we may experience lowered data speed temporarily during such time.

So actually, it cannot be happened only at “30 minutes from 12:15 to 12:45,”
but also, similar peak times or crowded areas such as:

Commuting hours on weekdays (7:00-9:00, 18:00-19:00)
Lunch time (12:00-13:00)
Celebration moments (New Year, etc.)
Terminal stations (Tokyo, Osaka, etc.)
Concert venues (Budokan, Tokyo Dome, etc.)

By the way, what “Bandwidth” exactly is?

Well . . . let’s think about peak-hour traffic congestion.

In this situation,
bandwidth = a lane,
a packet of data = a car,
internet = the road.

When the traffic jam occurs,
the lane (bandwidth) is full of cars (packets of data),
and nobody can through the road (internet) without waiting much time.


Let me be MORE specific.

Through your research on using the internet in Japan,
you might have come across words “MNO” and “MVNO.”
These are terms which divide all the providers into two categories.

In Japan, major MNOs (Mobile Network Operator) are Docomo, KDDI (au), and SoftBank.
They own wireless network infrastructures & physical stores, and deliver various services directly to their end users .
If we use “auto traffic” metaphor above, it’s like they own their lanes.

There are lots of MVNOs (Mobile Virtual Network Operator) in Japan, and the numbers of them are increasing rapidly.
They have No suggestions business agreements with MNOs to obtain bulk access to network services at wholesale rates, then set retail prices respectively.
If we use “auto traffic” metaphor above, it’s like they borrow lanes from MNOs.

Differences of MNO and MVNO also effect on the limitation on the data communication speed.

MNOs have wireless network infrastructures, which form part of society’s infrastructure.
To fulfill its social responsibility as a company, each has made systems for responding to emergency needs.
That’s why, their services enable users to continue to use the internet relatively stable even when the peak time.
In other words, you can say that their service prices are relatively pricey because of it.

MVNOs do not have wireless network infrastructures.
They just use fixed network bandwidth from MNOs, and which makes them free from the social responsibility MNOs have. And most of them also do not have any physical stores.
That’s why, they are more flexible than MNOs on setting various plans.
However, instead of it, data speeds in their plans tend to be reduced when people use the same fixed bandwidth at the same time.

I think the relationship between them is a kind of trade-off.
MNO = stable connection / pricey + long contract period (2 years at least)
MVNO = reasonable + flexible contract period / unstable when the peak time or area

Currently, most visitors to Japan technically have to use services from MNOs to avoid a long contract.
So, now we only have a few options to choose:
Buying a prepaid SIM card or renting a SIM card or a pocket WiFi router.


A Solution To Avoid Lowered Internet Speed

Now you’ve come a long way. Thank you very much for reading through so far.
Let me propose a solution to this “Slow Internet Speed in Peak Time” issue.

How about renting a data SIM card or a pocket WiFi router, not purchasing a prepaid SIM card?

In case of Prepaid SIM Card

Bandwidth is fixed, and cannot be proved soon.
Although most MVNOs somewhat estimate peak times and set bandwidth accordingly,
it is difficult to grab the maximum amount of data as they cannot know when users actually activate their prepaid SIM cards.
From this point, you may be able to say that prepaid SIM cards are not made to be used in peak times/areas comfortably.

If the data speed is low when you purchased it especially on peak seasons,
it may keep that lowered speed until you back to your home from Japan.
If we use “auto traffic” metaphor,
limited lanes are already occupied by other cars before you enter, and you have to be in the traffic jam.


In case of Rental SIM Card / Pocket WiFi

Bandwidth is fixed, but may/can be proved before the limitation occurs.
Because it is easy to grab the maximum amount of data from numbers of rental orders and fixed rental periods.
If we use “auto traffic” metaphor,
they can add lanes before the lanes are occupied by other cars, and you don’t have to worry about the traffic jam.

In addition to that, for example, LightPocket, one of MVNO, give you a refund if their SIM card/pocket WiFi didn’t work well in your location/situation.

Of course, this may not the only way to solve this issue.
However, as we look through so far, this should be the one of the best solutions logically and reasonably.

Good travel always starts from good preparation.
Hope your Japan travel will be memorable.


Source and Reference:
Nikkei Trendy Net (Japanese)

Pocket WIFI is the best for your trip or business trip to Japan for more stable communication than SIMcard or eSIM.

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I am Japanese and my nickname is Momo. I have been working in the mobile telecommunications industry for about 7 years and am familiar with Japanese telecommunications services. Although my English is not very good, I would like to provide useful telecommunication-related information to those who stay in Japan as accurately as possible.

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