Multiplexing Techniques for Scalable Wireless Interconnects at THz Frequencies ECCS-1408490 PI: Kushik Sengupta, Princeton University This proposal aims to investigate and develop spatially multiplexed architectures for wireless interconnects at sub-THz frequencies as scalable, energy-efficient solution towards one terabit per second (1 Tb/s). As we enter the era of terra-scale computing, massive amounts of data crunching by these processors will require inordinately large amount of bandwidth, not currently served by either electrical or optical interconnect solutions. Current methods of scaling of electrical interconnects to higher data rates are either limited by the available bandwidth density (Gb/s/mm2), energy cost, the circuit complexities in driving high-speed data through the long and lossy physical traces, or by the maximum number of parallel physical traces possible to accommodate in a constrained form factor. Wireless interconnects near THz frequencies are promising , but wireless data rates of 10Gb/s and the high energy/bit requirement, falls way short of meeting the bandwidth requirements for future off-chip interconnects. In this proposal, we aim to investigate techniques where the capacity of the channel can be increased many-fold using communication theoretic spatial-domain multiplexing techniques. Under the same total power constraint, such architectures have orders of magnitude more channel capacity, thereby providing a scalable solution towards wireless Tb/s interconnects. A key component in this proposal is to combine seamlessly, high-frequency circuits and systems and antennas with communication-theoretic techniques to increase capacity and data-rates by orders of magnitude, not otherwise possible in a single directional partitioned approach. Metal-based interconnect traces on printed circuit boards(PCB) serve as the most common method of chip-chip interconnects. However, increasing need of computational power to crunch more and more data in specialized server systems, high-performance computing or even portable devices, requires that communication data-rate from the processor to the peripherals be scaled proportionately. In most cases, the number of input-output pins is limited by the form factor, which puts a bottleneck on communication capacity among all the processors. In this proposal, we investigate techniques to use very high-frequency electromagnetic waves located in the Terahertz portion of the spectrum (between microwaves and infra-red) to establish seamless wireless communication links among the chipsets. Moving to such high frequencies enables us to exploit orders of magnitude higher bandwidth needed for sustaining such high data rates. Additionally, we investigate techniques to increase the communication links capacity by another order through spatial multiplexing techniques in a short-range communication setting. The success of this project is envisioned to bring new forms of smart interconnect solutions for a host of various applications from high-performance computing to internet data centers. The results of this research effort are also expected to have major impact in advancing the field of THz electronics benefitting diverse applications such as imaging and sensing. In a broader vision, this will have major impacts in radically new technologies in communication and computation, which not only makes us a more connected society, but also fuel research in other areas of applied science. This research is also expected to train both graduate and undergraduate students in multi-disciplinary fields, which are vitally important for solving challenging research problems for the future.
