Tuesday, September 18, 2012

More details on KDDI 4G LTE, iPhone 5 battery, and tethering

AU by KDDI will start their 4G LTE service with release of the iPhone 5 on September 21 and plan to have 98% poulation coverage by March 2013. Voice will be handled by the existing CDMA-2000 3G network, while data will be through LTE (when coverage is present). Maximum theoretical LTE speeds are the same as NTT Docomo's Xi LTE network at 75 Mbps. There will be areas limited to 37.5 Mbps, but as network construction proceeds, these will be converted over to 75 Mbps.

Prior to the September 14 KDDI press conference introducing their 4G LTE service, Ishikawa Tsutsumu was able to sit down with an unnamed KDDI representative who has specific knowledge on KDDI's LTE impletation. (「LTEネットワーク担当者」). Below are highlights from the interview, intermixed with our thoughts.
Network usage
NTT Docomo complained in the past regarding the connection frequency of Android handsets. This, along with popular services such as LINE and the general crappy infrastructure supporting the prone-to-failure Sp Mode, has contributed to network issues for Docomo.

The KDDI LTE rep mentioned that, while the actual bandwidth consumed by existing iPhones on KDDI's CDMA-2000 network is equivalent to that of Androids, the iPhone puts less of a strain on the network because it bundles traffic into fewer connection attempts. Signaling by Androids is more frequent.
The rep didn't offer more information other than they will make sure to have good coverage in the area from Osaka to Tokyo (toumeihan), not by simply focusing on the total number of base stations but by providing a continuous coverage area lacking gaps. By the end of this fiscal year, they intend to have a number of indoor locations, such as subways, well covered with Band 1 FDD-LTE.
KDDI LTE bands
As covered in a previous interview with KDDI CEO Tanaka, original plans called for focusing primarily on the 1500 MHz and 800 MHz bands for LTE, the latter of which provides superior indoor penetration. the iPhone changed those plans and they are focusing on 2100 MHz, though they will build out a network using all three. The focus on 2100 MHz instead of 800 MHz will require that KDDI use femtocells for indoor/underground locations

For now, the 2100 MHz band will be specific to the iPhone, but other handsets will eventually use it as well.
iPhone 5 battery life with LTE
LTE is notorious for draining batteries. Apple is claiming that they have done it right where everyone else is doing it wrong. I'm not sure if I totally buy into this.

Apple is infamous for claiming that anytime they do something new, it's the first time that it's ever been done. More correctly, Apple is famous for being the first to do it and get it right. However, the KDDI rep is claiming that, with all tweaks and improvements considered, the iPhone 5 will have a longer single-charge data transmission time of 8 hours using LTE, where previous iPhones got only 6 with a 3G connection.

The KDDI rep claims that this is not just the result of a higher-capacity battery because talk time is not changed, remaining at 8 hours. (iPhone 5 tech specs claim 8 hours for both 3G and LTE.)

I'll need to see this in the real world before I believe the claims. Is performance sacrificed? Does the phone fall back to 3G often?

Make no mistake though: LTE battery life on the iPhone 5 will be one of, if not the, best of any phone released to date. This is just the natural progression. LTE has been around for several years now, giving all makers ample time to study it. Apple has been slow to release LTE devices, and I'm 100% positive the reason for this is finding a means to do it such that it doesn't turn the phone into a space heater, killing the battery dead in a few hours.

Not that there is an LTE iPhone, it's safe to say Apple is satisfied with battery life.

The KDDI rep also indicates that their implementation of LTE will reduce wasted power searching for an LTE signal when there is none available. Their CDMA-2000 3G network will signal the phone that it has entered an LTE coverage area, triggering the LTE radio to begin connection attempts. Lacking this "There's an LTE network here" (「ここにLTEネットワークがあるよ」) signal, the LTE radio stays off.

The rep says he doesn't know exactly how NTT Docomo is doing things but guesses that they are struggling with determining the level of LTE signal degradation that should force a fallback to 3G. In a couple of more years, however, this won't matter as LTE coverage seriously approaches 100% of the population.
On Tethering
Tethering requires subscription but will be free for the first two years, after which it will cost an additional 500 yen plus tax (¥525 for now). KDDI will be spreading it's LTE services over the three bands mentioned above, so the rep believes they'll have the network capacity to handle it, plus they have the experience of offering wimax.

When asked why Softbank Mobile lacks tethering, as I've also stated, the rep believes that Softbank will eventually offer tethering. The rep indicates that KDDI doesn't have any idea what is going on at Softbank, but that they've probably just been slow to put into place a system for checking if a users is subscribed for tethering and may be dealing with network capacity issues.
The A149 GSM and CDMA models the same (in just Japan?)


Ishikawa: Android makers have introduced country-specific models to overcome regional difference in LTE frequencies, but Apple was able to accomplish this with only 3 models. That was truly surprising. What are your thoughts?

KDDI guy: I think there is essentially only two models. Our CDMA and Softbank's GSM A1429 models are the same. AT&T's main band is band 4. It's apparently difficult to transmit on bands 3 and 4 with the same hardware. This is troublesome to overcome for the radio makers, requiring two separate models. However, it is expected that the next year it will be possible to do this with only one model.

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