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Untangling smartphone tethering plans

by Kazuaki Nagata

Staff Writer

With the spread of smartphones and high-speed communication networks, so-called Internet-tethering services are now a possibility in Japan. But what is actually involved in such services can be confusing — such as what phones are tethering-ready, how much the service costs and if there are differences among carriers. To help you decipher the various tethering plans being offered by Japanese carriers, here are some answers to frequently asked questions.

What is tethering?

Tethering is a function that enables phones to work as a wireless Internet router, so that other devices such as handheld game consoles and laptops can connect to the Internet via the phone.

Do all major carriers provide tethering?

No, but they soon will, as SoftBank plans to launch its service on Dec. 15, pulling it in line with rival carriers.

NTT DoCoMo began its smartphone tethering service about a year ago, while KDDI’s au brand has been offering tethering since April 2011. EAccess Ltd.’s Emobile — which SoftBank announced earlier this month it will acquire — also provides a tethering service with its smartphones.

SoftBank CEO Masayoshi Son said he was worried that the tethering service would drastically increase the traffic of data and severely strain its network. But as tethering has become a standard service for other carriers, SoftBank had no choice but to also offer the service — in particular in order to compete with KDDI.

Apple’s iPhone 5, which debuted last month, is tethering-ready and KDDI had announced that its iPhone 5 users would be able to use tethering from the beginning, while SoftBank’s iPhone 5 would have the function disabled. Son said he received many requests for tethering from customers, so he decided to offer the service.

What phones are tethering-ready?

Most recently released smartphones that can connect to high-speed communication networks such as WiMAX and LTE — which are several times faster than the current mainstream 3G network — can be used to tether other devices to the Internet.

Nearly all DoCoMo’s LTE smartphones released in the past year have a tethering function. DoCoMo calls its LTE network Xi.

Most smartphones from KDDI’s au released in the past year are also tethering-ready with the WiMAX network. KDDI’s subsidy UQ Communications operates the WiMAX network.

Last week, KDDI introduced more LTE smartphones that will ship in November, and they are all tethering-ready, too.

Emobile runs its own LTE network, but no LTE-ready smartphones have been released yet. Emobile subscribers, however, can use a tethering service through its recent 3G smartphones, though this is much slower.

Other than the iPhone 5, SoftBank is expected to have two models — the China-based Huawei Technologies’ Stream and U.S.-based Motorola Mobility’s Razar M — available with tethering when it launches the service on Dec. 15. Those two models are compatible with the SoftBank 4G or TD-LTE network, which is another type of high-speed mobile network.

How fast is the tethering Internet speed?

The fastest network at this point is LTE. DoCoMo’s Xi LTE and KDDI’s LTE provide maximum speed of 75 megabits per second (Mbps) of downloads and 25 Mbps upload speed.

KDDI’s WiMAX network reaches 40 Mbps downloads and 15.4 Mbps uploads.

SoftBank’s 4G LTE, which is currently only used by the iPhone 5, can also reach 75 Mbps downloads and 25 Mbps uploads, while SoftBank 4G (TD-LTE) has 76 Mbps downloads and 10 Mbps uploads. While the upload speed of Emobile’s 3G maxes out at 5.8 Mbps, the download speed differs depending on the handset, ranging from 7.2 Mbps to 21 Mbps.

DoCoMo, KDDI and SoftBank also offer 3G tethering when users are outside of high-speed network areas.

These are all theoretical top speeds — the actual speed is usually slower.

How much does it cost? Do we need to pay extra for tethering?

It’s common for smartphone users to sign up for a two-year contract with unlimited monthly Internet access at a flat-rate fee, so the following is based on that situation.

DoCoMo offers an unlimited data-usage plan for ¥5,985. This includes all Internet and data activities on smartphones, such as Web browsing, e-mail, posting photos on Facebook and tethering.

KDDI’s plan for unlimited data usage on smartphones costs either ¥5,460 or ¥5,985 depending on which phone you choose. For its tethering option, it costs an additional ¥525 monthly, but the carrier is offering tethering free for its LTE smartphones at the moment.

The same plan on SoftBank is currently ¥5,460 per month with tethering free for two years — after which it will be ¥525 a month.

Emobile’s data-plans range from ¥4,280 to ¥5,980 monthly with no additional cost for tethering depending on how much of a downpayment users make up front.

These prices are subject to change from time to time due to pricing competition, and they may also change during promotional campaigns.

Is the service really unlimited?

Yes, but if subscribers use a large amount of data monthly or daily, such heavy users will find their Internet connection throttled.

For example, if subscribers use 7 GB of data in a month through tethering, DoCoMo and SoftBank drop the maximum speed to 128 kilobits per second for the rest of that month.

KDDI applies the same restriction to users who use 7.5 GB data a month with the LTE tethering service. WiMAX phone users have a 5 GB limit with the use of the 3G network, but as long as they are using WiMAX, there is no limit.

Once DoCoMo, KDDI and SoftBank users reach those limits, they can keep the high-speed connection by paying ¥2,625 for an extra 2 GB.

Those three carriers may also put a speed restriction on those who have used more than 1 GB of data in three days depending on the traffic situations.

Emobile enforces a speed restriction from 9 p.m. to 2 a.m. once the amount reaches 366 MB per day, but it does not disclose how low the speed drops.

How much data is 7 GB?

According to DoCoMo, if, every day for a month, users were to browse the Internet for 2½ hours, send 40 e-mails, download two songs and watch 40 minutes of video, then their monthly data consumption is likely to reach 7 GB.

All carriers said that most smartphone subscribers do not reach those limits.