Live in Japan: Next GenPHS to Rival WIMAX and LTE - Commsday

Live in Japan: Next Gen PHS to rival WIMAX and LTE
Commsday

May 9, 2008

The vendors and operators behind the Japanese PHS (Personal Handyphone System) are promoting a new standard called XGP that will offer mobile broadband speeds that rival WiMAX and LTE, it’s emerged at ITU Asia in Bangkok.

PHS was an early digital cellular offshoot with roots in cordless phone technology. It has low power, low range characteristics and was adopted there mostly because it was deemed suitable for Japan’s high urban densities back in the 1990s. It’s much cheaper to deploy thanGSM but isn’t so good at high-speed handover and is now losing ground in its home market to GSM.

But its fortunes may revive somewhat if it can produce a cost-effective next gen platform for data. According to Nobuaki Takamatsu from the engineering department of Kyocera, a trial XGP service will go live in three Japanese cities as early as next April by PHS operator, Willcom, who was awarded one of two blocks of spectrum in the 2.5 GHz band from the government last December.

A KDDI-led group with a WiMAX strategy was the other winner of the license and spectrum allocation beauty contest for the development of next generation wireless services. TheWillcom trial next April will cover Tokyo, Nagoya and Osaka and offer 20Mbps of symmetrical data speeds using a 10MHz spectrum block. A full commercial service is scheduled for August 2009.

On display at the XGP booth at the ITU Asia show was a base station that was the size of small hand luggage as well as prototype data cards and USB dongles. At this point, the system is designed for data only services, but handsets are expected at a later stage.

“This system will offer faster data speeds than 3G,” Takamatsu told CommsDay. “The service is ideal for heavy Internet users from the business sector.”

The technology behind is based on the PHS architecture of numerous microcells offering limited coverage, but will incorporate a new air radio interface based on OFDMA/TDMA/TDD methodologies. Kyocera and UTStarcom will manufacture the radio access equipment for XGP while NEC Infrontia and NetIndex are developing the data card modules for the service. Canada’s Wavesat and Israel’s Altair is supplying the baseband chips for XGP. Like LTE and WiMAX, XGP will support viable spectrum blocks.

But while LTE and WiMAX are based on increments of 1.6MHz for its carrier size, XGP has aligned itself with CDMA and supports increments of 1.25MHz carriers.

With a basic 10MHz carrier system, XGP will offer data speeds of 20Mbps, but future systems incorporating MIMO and SDMA (space division multiple access) will be capable of supporting maximum symmetrical data speeds of 100Mbps, Takamatsu said. At the same time, the technical description for XGP will support handoffs between base stations for users travelling at up to 300 km/h, he added.

Takamatsu says the XGP vendors are looking to market the system outside Japan with fellow PHS vendor UTStarcom already planning a trial service in China at the 1.9GHz spectrum band.

Outside Japan, the obvious market for XGP will be the PHS networks deployments in markets such as China, Thailand, Taiwan, Bangladesh and Indonesia.
But if it proves its performance, theXGP system offers an intriguing alternative for CDMA operators in that it is aligned with their spectrum plans based on 1.25MHz carriers. With UMB, the CDMA-based 4G technology, now dropping rapidly off the industry radar, XGP may find a niche in upgrading CDMA networks with limited spectrum with mobile broadband capabilities.

As shown by two planned trials in Japan and China on different spectrum (2.5GHz and 1.9GHz) the system can be adopted for different bands, Takamatsu said.

One of the disadvantages for XGP may be its PHS legacy, which has an architecture based on many micro cells, as opposed to the wider coverage of macro cells for cellular systems. The typical coverage radius of anXGP base station is less than 1 kilometre, which means that XGP deployments – like their PHS predecessors – will require more base stations than cellular.

More importantly, given the high-speed nature of the service, backhaul capacity to each of these base stations will have to ramp up significantly to support users, which would impact deployment and operating costs.