Ultra-broadband femtocells via opportunistic reuse of multi-operator and multi-service spectrum

Recently, two important trends concerning cellular networks operating in licensed spectrum have emerged. First, the cellular operators are considering femtocells deployed in indoor environments such as homes and enterprise buildings as a complement to macrocells for the purposes of enhancing capacity and coverage indoors. Second, standards such as Long Term Evolution (LTE), and Worldwide Interoperability for Microwave Access (WiMAX) are designing air interfaces that use increasingly wider bands of spectrum (e.g., up to 20 MHz per channel) to increase access rates. However, given the restricted size of operator licenses, the number of wideband channels is limited. As broadband wireless access gains adoption and media-rich end user devices (e.g., iPhones) proliferate, the next frontier will be ultra-broadband wireless access which inevitably needs more spectrum. Given end users often spend 40 percent of their time indoors, femtocells may be the first user equipment to offer such ultra-broadband access. In this paper, we propose a novel way to enable such ultra-broadband femtocells by opportunistically accessing wider swaths of spectrum. Our solution is based on three new concepts—intra-operator spectrum white space reuse, multi-operator spectrum sharing, and multi-service spectrum reuse—which exploit the spectrum of multiple cellular operators and of multiple non-cellular services such as digital television (DTV) broadcasts in femtocells deployed in a relatively isolated indoor environment. We describe an end-to-end architecture consisting of four main components: a multi-operator spectrum server (MOSS), a femto coordination/controller server (FCS), a cognitive femto base station, and associated end user devices that support a new air interface operating in non-contiguous spectrum bands. We also describe application of our concepts and solutions in the context of refarming the Global System for Mobile Communications (GSM) spectrum worldwide to enable smooth evolution of GSM to third generation (3G) LTE standards.