Researchers at Fraunhofer Institute for Telecommunications have developed algorithms to share 4G LTE networks between carriers. The idea: two or more providers use the network jointly, meaning they are sharing the frequencies and the infrastructure. “This way, for example, customers of network provider A in Bavaria could use the base stations of network provider B in Brandenburg and vice versa,“ says Dr. Volker Jungnickel of HHI. 4G LTE Spectrum sharing offers carriers many advantages beyond cost savings such as better coverage.
http://www.fraunhofer.de/en/press/research-news/2012/february/jointly-utilizing-ltenetworks.html