Enhancing Spectral Access through Adaptive Terahertz Communication Systems

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High-speed wireless communication has attracted extensive attention in the past decades because of dramatic changes in the ways people create and share information. The expected data rate to satisfy the needs of the customers is projected to be 100 Gbit/s by 2020. However, the speed of today's wireless communication systems is limited by the narrow bandwidth of existing transmitters and receivers and the heavy use of the electromagnetic spectrum up to 60 GHz. This trend has been forcing researchers to push the carrier frequencies of transceivers to higher frequencies to allow operation at frequency bands which have not been allocated to any specific active service yet. In order to increase the channel capacity, researchers have been trying to operate at terahertz frequencies, which cover the frequency range of 0.3-10 THz in the electromagnetic spectrum. While communication systems with such high carrier frequencies have been hard to develop so far, a data link operating at terahertz frequencies with data rates exceeding 100 Gbit/s over 10-20 meters distance is believed to be viable now thanks to recent advancements in terahertz photonics and electronics. The research component of this program plans to develop such a high data rate wireless communication system at terahertz carrier frequencies for indoor communication applications. A system with this capability can be very suitable for the next generation indoor wireless communication systems such as wireless local area networks and wireless personal area networks, kiosk downloads, wireless backhauling, data center connection, and real-time data analysis for wearable devices. Additionally, this program plans to integrate research with education and outreach activities by developing new courses, recruitment and involvement of undergraduate students, and organizing high-school seminars. During this program a directional terahertz transceiver system based on an adaptive two-dimensional array of plasmonic photomixers operating under novel communication protocols is designed, fabricated, and experimentally demonstrated. The proposed work presents an entirely new perspective on the potential use of terahertz bandwidth for increasing wireless communication data rates to levels that could not be envisioned before due to low output power and limited adaptability of existing terahertz transmitters. This limitation can be tackled through use of plasmonic photomixer arrays that offer significantly higher terahertz radiation powers and higher level of transmitter adaptability compared to other terahertz transmitter candidates. Additionally, the adaptive nature of the proposed terahertz transceiver system allows compensation for accidental misalignments and shadowing effects through beam-forming and non-line-of-sight communication links. While theoretical investigations provide a deep understanding of fundamental physical limitations of terahertz transceiver systems based on plasmonic photomixer arrays and achievable wireless communication data rates, the experimental effort provides valuable data to develop accurate channel models at terahertz frequencies in order to utilize appropriate communication modalities, equalization techniques, and adaptive signal tracking systems to mitigate signal fading in indoor terahertz communication systems.