Japan’s UQ Communications has been achieving up to 16Mbps on the downlink and up to 3.9Mbps on the uplink since free trials of the service began in February 2009, reports Wireless Watch Japan.
The Japanese Mobile WiMAX license holder is running a 4 month trial period, prior to a formal network launch expected in July.
The trials are taking place in Tokyo (all 23 wards), Yokohama and Kawasaki using some 600 Samsung base stations, which are compliant to WiMAX Forum Wave-2 Phase-2 specifications. Wave-2 Phase-2 supports various additional features compared with Wave-2 Phase-1, such as QoS for real-time and near real-time video, multicast broadcast services, and IPv6.
UQ is the first major mobile WiMAX operator to use FFR (fractional frequency reuse), which, says UQ, can improve overall spectrum efficiency by 85 per cent compared with a typical ‘3-frequency’ operation.
Mobile WiMAX is deployed like a cellular network. While Clear and Sprint in the US have spectrum to burn, using different 10 MHz spectrum on each of 3 sectors, most operators don’t have 120 MHz available and must use their 30MHz-50MHz of bandwidth more efficiently.
When all sectors within a cell and all cells within a network operate on the same frequency channel, it’s called frequency reuse one. But users at a cell edge can get degraded signals due to interference from adjacent cells.
Mobile WiMAX “tweaks” frequency reuse one using sub-channels. It works by allowing users at a cell center to operate on all available sub-channels. Cell center is the area closer to a base station (BS) and is largely immune to co-channel interference.
With fractional frequency reuse, users at a cell edge are only allowed to operate on a fraction of all available sub-channels. Users on adjacent cell edges operate on different sets of sub-channels, avoiding interference.
Fractional frequency reuse takes advantage of OFDMA sub-channels. The three sectors for one BTS each use one-third of the sub-channels. WiMAX sub-channels don’t occupy an entire frequency, unlike 3G (CDMA or HSPA). It’s time sliced.
Fractional frequency reuse, say WiMAX proponents, squeezes the most performance out of available frequencies and delivers better throughput at the cell edge. LTE will likely have a similar capability.
The biggest single investor in UQ is KDDI, the CDMA cellular provider. UQ is the only company that has a nationwide approach for their 2.5 GHz spectrum and expects to have more than 90 percent population coverage by 2012.
UQ Communications has selected NEC to supply it with 802.16e base stations. The deal is a major boost for the Japanese vendor’s recently developed PasoWings BS202 mobile WiMAX base station, described as the world’s first with UL-BF (uplink-beamforming), which are used to improve communications speed and increase base station coverage.
Japan’s four main cellular operators – NTT, KDDI, SoftBank and Emobile – plan to invest up to USD10 billion into so-called ‘3.9G’ mobile services. What’s 3.9G? Both LTE and FDD Mobile WiMAX meet the definition. True “4G” comes after LTE. Both LTE-Advanced and IEEE 802.16m are candidates for “real” 4G — called IMT-Advanced by the ITU.
Japan’s 112 million Mobile subscribers
87.82% penetration rate. (March 2009) Source: Wikipedia
Japan plans to launch 3.9G services as early as 2010 and will divide the available 45 MHz to four bands, 10MHz*3 + 15MHz, amongst the four incumbents in Japan. Not really enough to provide sufficient capacity for LTE, some argue. Japan, like the United States, believes abandoned analog tv channels may provide spectrum for future growth.
UQ was one of the two 2.5GHz licenses awarded last year. The other license went to Willcom, which operates the country’s PHS network for low cost voice, and is likely to use its license mainly for that.
Clearwire expects to launch mobile WiMax in eight more US markets in 2009, spending between $1.5 billion and $1.9 billion on the deployments. Clearwire will deploy new networks in Atlanta, Las Vegas, Chicago, Philadelphia, and Dallas/Ft. Worth this year and convert its fixed wireless Seattle, Honolulu, and Charlotte networks to mobile WiMax in 2009.
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