Docomo's FY2010 end of year report (PDF) includes some more information on LTE plans for this year.
Docomo has seen a steady year over year increase in data traffic and is projecting a doubling during 2011. Docomo plans for increased demand to be partially offset by increased Xi coverage, which will improve overall network quality due to the dynamic network controls and data offloading provided by LTE.
Somewhat interestingly, however, is that projected revenue from data in 2011is to come overwhelming from smartphones, primarily at the expense of feature phones, rather than from data devices. Since only one LTE handset is in the works so far, and the Spring 2012 models would hardly contribute to FY2011 earnings at all, it would seem that most of this revenue would be coming from FOMA 3G smartphones. This means the network enhancements that LTE brings to the game, as mentioned above, would be not have so much of an effect on improving network quality. To be fair, though, Docomo's network seems robust enough to handle the extra traffic.
Of course revenue does not necessarily scale linearly with the number of consumed data packets; there most certainly will be heavy discounts offered to customers who sign 2 year Xi contracts. Also, I am assuming that bandwidth consumed by non-voice enabled tablets is not included in the smartphone category but rather in the data device category (based on the APN and service plan required for these tablets).
Since rolling out service in December 2010, Docomo has amassed only 26,000 subscribers but is aiming to raise that to one million by the end of FY2011. Growth is then projected to slow with only 1.5 million subscribers by 2014.
The slow addition of customers so far is certainly related to the lackluster product offering, which is limited to a USB and an ExpressCard dongle. Planned for release this year are a router in summer, followed by a (Fujitsu?) tablet this fall, and finally a (Samsung?) smartphone in winter. (brands via juggly).
By April 2011, there were approximately 1,100 Xi base stations covering around 8% of the population. By July 2011, service is planned for roll out in Sapporo, Sendai, Kanazawa, Takamatsu, Hiroshima, and Fukuoka. By April 2012, coverage is expected to grow to 20% with a total of 5,000 stations this year.
A word of warning to those eagerly awaiting the start of service. Note the patchiness in Tokyo at the moment. While less urban areas would be easier to blanket, be certain to confirm that you are in a coverage area before signing up.
Finally, two words on the potential problem of interference with GPS in Japan: No Problem.
A few more words. LightSquared has tentative approval from the United States FCC to build a wholesale LTE network using a ~ 1500 MHz frequency that is directly adjacent to a band used by GPS. US GPS manufacturer Garmin tested the proposed system in the lab (PDF) and determined that it will create significant interference. A representative car navigation system began to be jammed at a power level equivalent to an approximately 6 km distance from a single tower, with complete loss of signal at around 3 km and 1 km in urban and open areas, respectively.
In the US, the issue arrises from the repurposing of a band originally not intended for relatively high-power terrestrial transmissions. Docomo, as far as I can tell, is using a different 1500 MHz band that was set aside for cellular use, band 21 that doesn't interfere with GPS signals. Besides, given the coverage map above, we'd know already if jamming was an issue. Obviously it is not (in Japan).