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How well do upper millimeter-wave and terahertz frequency bands enable wireless communications? In this work, we approximate the current and estimate the future communication potential with emphasis on antenna and radio frequency hardware technologies, and radio propagation challenges. This is done by performing link budget evaluations with justified estimates of link budget calculus terms, such as the achievable or required noise figure, transmit power, and antenna gain. Estimates are based on current enabling technologies and needs to advance those. In RF viewpoint the bottlenecks are in generating sufficiently high transmit power and low noise with the support of very high antenna gains. As an example, we discuss opportunities around 300 GHz frequency. Challenges to support 100 Gb/s bit rate at 30 GHz bandwidth on 10-meter link distance is analyzed for different kind of devices.

In this paper, we focus on the joint subcarrier and power allocation for an orthogonal frequency division multiple access (OFDMA) full-duplex (FD) system with the goal of maximizing the sum-rate subject to power constraints at the base station (BS) and uplink users, and subcarrier constraints. A greedy subcarrier allocation algorithm based on the necessary conditions of the optimization problem and a power allocation algorithm based on the iterative water-filling (IWF) are proposed. A hybrid scheduler that can switch between FD, half-duplex (HD) uplink and HD downlink mode at each time-slot to maximize the sum-rate is presented. Simulation results reveal that the proposed hybrid scheduling switches to FD scheduling at high self-interference cancellation values, and to HD-time-divisionduplexing (TDD) scheduling at low self-interference cancellation values, and thus improves the sum-rate over the traditional HD-TDD scheduling.Index Terms-Full-duplex, self-interference, subcarrier and power allocation, iterative water-filling, OFDMA, resource allocation.

In-band full-duplex is a promising air interface technique to tackle several of the key challenges of next generation (5G) mobile networks. Simultaneous transmission and reception in the same frequency band increases the throughput and spectral efficiency, and reduces the air interface delay. Its implementation in 5G systems, however, restrains the full-duplex transceiver design requirements. Two analog integrated circuit solutions are presented and evaluated in the frame of 5G applications. The first design is a self-interference cancelling front-end implemented in 65nm CMOS, and the second design is an electrical-balance duplexer implemented in 0.18µm RF SOI CMOS. Both designs are attractive in the context of 5G; they allow dense integration, are configurable to support alternative and legacy standards, are compatible with conventional antenna(s), and they provide an attractive full-duplex performance for wireless communications.

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