Wireless communication technologies such as cellular and WiFi are indispensable for modern society. However, existing wireless networks are under severe stress due to the explosive demand caused by smart mobile devices capable of creating and consuming large amounts of multimedia content (especially images and video). Meeting these demands is estimated to require 1000-fold increases in wireless network capacity, which cannot be obtained by incremental advances using existing spectrum. A promising approach for delivering the required revolutionary advances in wireless by employ the so-called 'millimeter (mm) wave' band, which has huge amounts of available spectrum (e.g., 7 GHz in the unlicensed 60 GHz band alone). The wavelength in these bands is an order of magnitude smaller than that in today's wireless networks, drastically changing the physical and propagation characteristics: for example, mm waves are easily blocked by obstacles such as human bodies, but steerable antenna arrays with a very large number of elements (up to 1000) can fit in compact form factors, enabling us to potentially steer around obstacles using bounces from reflectors. As a consequence, realizing the potential for mm wave communication requires a comprehensive reexamination of existing wireless design principles, using an interdisciplinary approach that goes all the way from antenna design to network protocols. The goal of this project is to take such an approach for establishing fundamental principles for design of next generation mm wave communication networks, with a research agenda combining cross-layer modeling, design, and performance evaluation, firmly grounded in experiment. A key technical issue is to how to efficiently adapt electronically steerable arrays with a large number of elements, and to integrate them into network protocols.
The research is driven by the following cutting edge system concepts: (a) Cellular 1000X, aimed at relieving the cellular capacity bottleneck via 60 GHz cellular links delivering Gbps data rates to the mobile, together with a seamless extension to indoor networks; (b) 'Wireless fiber' backhaul at 140 GHz for enabling Cellular 1000X, based on easy to deploy outdoor wireless mesh networks with link speeds approaching 40-100 Gbps; (c) 40 Gbps indoor 60 GHz links, aimed at going beyond nascent industry efforts such as NG60 that aim to upgrade link speeds in the recently developed IEEE 802.11ad wireless local area network standard. The goal of this project is to design a system that will achieve the stated objectives, and prototype an advanced proof-of-concept that will help pave the way for eventual technology transfer leveraging the close ties of the project team to industry. A 60 GHz experimental platform developed to support the research will be made available to the research community, to stimulate a broader academic effort in this area.
Due to the small carrier wavelengths, beamforming at both ends is critical to make the link budget work, but it is essential to make the beams electronically steerable to steer around obstacles (which ``look bigger at smaller wavelengths''), and to allow automatic network configuration. Cross-layer frameworks for resilient pencil beam networking for both Cellular 1000X and indoor WLANs will be developed and demonstrated. These will incorporate compressive array adaptation techniques, a core innovation to be demonstrated in this project. Compressive adaptation enables 3D beamforming for robust link budgets, steering around blockage, and spatial reuse, and enables scaling of both the number of antenna elements and the nodes in the network, unlike existing scan-based IEEE 802.11ad medium access control (MAC) techniques. System concepts to be designed and tested include (a) `Picocloud' network architectures that employ tight coordination between base stations and APs (for outdoor and indoor environments, respectively) to provide seamless connectivity in the face of blockage; (b) Integration of beamforming with spatial multiplexing in LoS or near-LoS environments, demonstrating the scaling of available degrees of freedom with carrier frequency through prototypes at 60 GHz and 140 GHz.
A reconfigurable phased array at 60 GHz will be developed and integrated with the NSF/CRI-funded WiMi software defined radio platform, in order to enable the preceding system-level explorations (while beamsteering ICs developed by industry have been incorporated into products, external control of the beamsteering coefficients is not available). In addition, a hardware testbed for LoS spatial multiplexing at 140 GHz will be developed to demonstrate the potential for 'wireless fiber' backhaul links beyond 100 GHz.
