UPDATE 2-Canada aims for more competition in wireless auction

* Ottawa sets Nov. 19 to start 700 MHz spectrum auction

* Sets floor on opening bids totaling C$897 million

* Expands roaming, cell tower sharing rules

* No immediate plans to lift foreign limits on big telcos

OTTAWA/TORONTO, March 7 (Reuters) - The Canadian government said on Thursday it would start the process of auctioning prime wireless spectrum on Nov. 19 and announced other steps designed to stimulate competition and reduce high roaming charges.

It confirmed its intention, announced last March, to use the auction of prime 700 MHz spectrum to assure at least four competitors in each region of the country, limiting the incumbents to three of four prime blocks in each area.

Canada's wireless market, which has some of the highest roaming charges in the world, is dominated by BCE Inc's Bell , Rogers Communications Inc and Telus Corp , which together control some 90 percent of the business.

The government's last auction of airwaves in 2008 brought in some new competitors, including Wind Mobile, which is in the process of being acquired by Amsterdam-based VimpelCom Ltd .

The latest spectrum to be auctioned is highly valued for its ability to penetrate buildings and travel long distances.

Ottawa set an opening bid level totaling C$897 million ($870 million) for the auction. Industry Minister Christian Paradis would not say how much revenue he hoped to raise from the auction but said he expected there to be strong investor interest.

"There is no certainty with this. We put a floor with which we are comfortable," he told reporters. "We expect there will be interesting competition."

The 2008 spectrum brought in C$4.25 billion for the government.

Last March, Paradis reduced foreign investment restrictions on small carriers that have a market share of 10 percent or less. He said on Thursday it was premature to talk about expanding this to the larger companies.

"What we understand is that we would have to hold public consultations. We're not there yet," he said. "What we sent here is a clear signal that we want to have more competition in the telecom sector."

Paradis said since the government set aside wireless spectrum for new entrants in 2008, wireless prices for consumers have fallen by 10 percent.

The government is also indefinitely extending the requirement for wireless carriers to provide roaming on their network to competitors, and expanding the requirement to all carriers. It had introduced roaming policies in 2008 but some provisions were only available to new entrants for five years.

The new rules require greater accountability by carriers to increase the sharing of antenna towers and sites, and reduce negotiation and arbitration timelines.

The changes are intended to make it easier for small companies to provide wider access. It pledged further action if progress is not made on tower-sharing.

"Our government's priority is to provide greater wireless coverage at lower rates for consumers," Paradis said.

There are seven blocks available in the wireless spectrum auction, but bidders will likely covet four aligned with spectrum bought by AT&T and Verizon Wireless in the United States. Verizon is a venture of Verizon Communications Inc and Vodafone Group Plc.

Those carriers hold more sway with device manufacturers and can push to ensure future smartphones and tablet computers work on those specific frequencies.

The government has said BCE, Telus and Rogers can only obtain one of these prime blocks each, leaving the new entrants and regional cable operators such as Quebecor Inc and Shaw Communications Inc to compete for the fourth.