Limits on the Capacity of In-Band Full Duplex Communication in Uplink Cellular Networks

Simultaneous co-channel transmission and reception, denoted as in-band full duplex (FD) communication, has been promoted as an attractive solution to improve the spectral efficiency of cellular networks. However, in addition to the self-interference problem, cross-mode interference (i.e., between uplink and downlink) imposes a major obstacle for the deployment of FD communication in cellular networks. More specifically, the downlink to uplink interference represents the performance bottleneck for FD operation due to the uplink limited transmission power and venerable operation when compared to the downlink counterpart. While the positive impact of FD communication to the downlink performance has been proved in the literature, its effect on the uplink transmission has been neglected. This paper focuses on the effect of downlink interference on the uplink transmission in FD cellular networks in order to see whether FD communication is beneficial for the uplink transmission or not, and if yes for which type of network. To quantify the expected performance gains, we derive a closed form expression of the maximum achievable uplink capacity in FD cellular networks. In contrast to the downlink capacity which always improves with FD communication, our results show that the uplink performance may improve or degrade depending on the associated network parameters. Particularly, we show that the intensity of base stations (BSs) has a more prominent effect on the uplink performance than their transmission power

DbSWPT: A Novel Distance-based Switch for Efficient Wireless Power Transfer in Battery-less Wireless Capsule Endoscopy

The restricted power supply of batteries hampered the development of capsule endoscopy. Accordingly, a distance-based switch is proposed for efficient wireless power transfer (WPT) system. It targets battery-less wireless capsule endoscopy (WCE). The proposed system consists of two separate coils with distance significant impact. To tackle problem, a distance-based switch configuration is proposed between two variable load resistances according to distance between transmitting and receiving circuits. Results proved high efficiency at short distances using potentiometer in decreasing direction which starts with high resistance values and then decreases to a certain value of resistance according to measured distance whereas the other has a high efficiency at long distances using potentiometer in increasing direction which starts with low resistance values and then increases to certain value of resistance according to measured distance. The results illustrated that the system performance using series-series (S-S) configuration is superior to using the parallel-parallel (P-P) configuration. It is found that the minimum efficiency for the proposed P-P distance-based switch is 51%, while for the proposed P-S is 83.33% . Accordingly, the proposed switch-based S-S configuration achieved minimum efficiency 90.91%. It increases the efficiency by 8.34%

In-Band Full-Duplex Communications for Cellular Networks with Partial Uplink/Downlink Overlap

In-band full-duplex (FD) communications have been optimistically promoted to improve the spectrum utilization in cellular networks. However, the explicit impact of spatial interference, imposed by FD communications, on uplink and downlink transmissions has been overlooked in the literature. This paper presents an extensive study of the explicit effect of FD communications on the uplink and downlink performances. For the sake of rigorous analysis, we develop a tractable framework based on stochastic geometry toolset. The developed model accounts for uplink truncated channel inversion power control in FD cellular networks. The study shows that FD communications improve the downlink throughput at the expense of significant degradation in the uplink throughput. Therefore, we propose a novel fine-grained duplexing scheme, denoted as $\alpha$-duplex scheme, which allows a partial overlap between uplink and downlink frequency bands. To this end, we show that the amount of the overlap can be optimized via adjusting $\alpha$ to achieve a certain design objective.Comment: To be presented in IEEE Globecom 201