Office workers now use their smartphones to get the job done, regardless of what phone system is actually installed in the workplace. But relying on a remote radio tower, one that could be miles away, to route calls is a recipe for full-on fail. You can have five bars on your phone and still be unable to connect a call or run an app.

“Even perfect coverage does not always mean you have access to the needed capacity.” That’s how SpiderCloud VP of marketing Ronny Haraldsvik explained it in response to my questions about the company’s new second funding round of $25 million, led by Opus Capital. Previous investors Matrix Partners and Charles River Ventures also participated, along with new investor Shasta Ventures.

The Santa Clara-based company’s management team have Cisco, Flarion, Juniper Networks, and Qualcomm on their résumés. They founded SpiderCloud in 2007.

SpiderCloud’s technology is a mini wireless phone network that can be set up inside an office building. It’s designed to mimic the well-known setup of an Ethernet network with Wi-Fi. The system consists of a bunch of radio nodes — sometimes called access points — set up where they’re most needed, controllable from a single controller, known as a services node to the people who manage the networks. SpiderCloud calls the whole setup an Enterprise Radio Access Network, or E-RAN.

Haraldsvik says SpiderCloud is in tests with a major wireless carrier in Europe — they call them operators over there — to make SpiderCloud part of that carrier’s offerings to business customers. The E-RAN’s 3G technology (it’s UMTS, if you care) would be compatible with AT&T and T-Mobile in America. In the end, the actual sale of a SpiderCloud network will be done by a network technology partner. Think Ericsson, Alcatel-Lucent or Cisco rather than Telefónica or AT&T. Presuming they pass testing, that’s a pretty good business model.