Sunrise has become the last of Switzerland's major mobile operators to rollout LTE.
Its network, which went live on Wednesday in 26 towns and cities, should deliver maximum download speeds of 100Mbps, Sunrise said.
Initially the network will cover around 22 percent of the company's customers, and will be extended gradually from there. Sunrise intends to provide 50 percent coverage by the end of October.
LTE connectivity will be available to anyone with a 4G-compatible smartphone, the company said, whether they're prepay or postpaid users. Those on Sunrise NOW tariffs will be able to the LTE network without any monthly data limits until the end of this year.
Customers of MVNOs that use Sunrise's network will also be able to get on its 4G from today.
"This year, our main priority is to modernise the entire network and rollout HSPA+ and the 42Mbps it brings across the country. At the same time, we're launching our LTE 4G network, which we'll be progressively extending," Elmar Grasser, Sunrise's COO, said in a statement.
The areas where 4G will be rolling out initially are: Zurich-Ville, Lac de Zurich, Winterthour, Oberland zurichois, Vallée de la Limmat, Vallée de la Glatt, Berne, Geneva, Morges, Préverenges, Lausanne Bâle-Ville, Birsfelden, Muttenz, Binningen, Reinach, Zoug, Cham, Baar, Steinhausen, Coire-Ville, Flim /Laax, Saas Fee, Zermatt, and Verbier.
Sunrise's 4G launch follows just weeks after rival operator Orange rolled out. Orange's 4G covered 35 percent of the Swiss population at launch and saw the company upping its total network investment to CHF 100m (€81m).
Swisscom, the country's largest mobile operator, has had its own 4G network up and running since late 2012, and is aiming to have 70 percent population coverage by the end of this year. Last month, it increased the, up from its previous 100Mbps top speed.