NeTS: Small: Mobile mmWaves: Addressing the Cellular Capacity Crisis with 60 GHz Picocells

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

Smart phones and tablets enable consumers to enjoy rich audio and video content on the go, but the proliferation of such increasingly sophisticated mobile devices has created a capacity crisis for mobile operators. It is estimated that supporting rich media content for a rapidly increasing fraction of mobile users requires a 1000-fold increase in cellular network capacity, which current cellular bands simply cannot support. The research pursued under this grant explores an alternative, and potentially transformational, approach to cellular data, using unlicensed spectrum in the 60 GHz band, where the available bandwidth is orders of magnitude higher than those used in existing systems, at the level of multiple Gigabits per second throughput on the downlink to the mobile devices. Base stations for the envisioned network will be deployed opportunistically (e.g., on lampposts and rooftops). Due to the small carrier wavelength, many antenna arrays with a very large number (e.g., 1000) of elements can be built into base stations which are no larger than a typical WiFi access point. Such antenna arrays can be used to direct pencil beams at mobile users, with peak data rates of multiples of Gigabits per second (order of magnitude higher than the highest WiFi data rates available today). However, the small carrier wavelength also implies that the radio waves are easily blocked by obstacles such as buildings, walls, and humans, including the body of the person carrying the mobile device. In order to handle such rapid changes in the propagation environment, novel techniques are developed for multiple base stations to coordinate, such that they can adapt their beams to maintain connectivity with a given mobile device, and can ensure that the data destined for the mobile follows it around. A novel asymmetric network architecture is employed, with low-bandwidth 60 GHz beaconing and multi-Gbps data on the downlink, and LTE feedback and lower-speed data on the uplink. The base stations employ compressive signal processing for rapid channel estimation and beam adaptation, based on the feedback from the mobiles. Distributed base station coordination mechanisms are developed for seamlessly switching base stations or paths. The architecture minimizes complexity and power consumption in the mobile device: the device's 60 GHz radio only needs to receive, and the device is oblivious of handoffs. The mobile broadband capacity crisis is the greatest challenge facing cellular providers today, hence the success of this project can impact a multi-billion dollar industry. In order to maximize the potential for impact, the results and models will be widely disseminated to both industry and academia. The investigators plan significant efforts for recruitment and mentoring of female undergraduate and graduate students, organized around the concept of a caring community.