580 California St., Suite 400
San Francisco, CA, 94104
Key research themes
1. How does energy harvesting influence protocol design and performance in wireless-powered cooperative communication systems?
This research theme focuses on integrating wireless energy harvesting with cooperative communication networks to sustain information transmission without embedded energy supplies. It examines protocol designs that enable nodes to harvest energy from access points for subsequent cooperative transmission, analyzing throughput performance and the effects of system parameters such as time allocation and relay positioning. This is important because it addresses the energy constraints in cooperative networks, which is critical for sustainable and energy-efficient wireless communication.
Key finding: Proposes the harvest-then-cooperate (HTC) protocol where source and relay nodes harvest energy from a hybrid access point's downlink transmission and cooperatively transmit in uplink. Derives closed-form expressions for... Read more
Key finding: Designs and implements a time exchange (TE) based cooperative forwarding scheme where transmission time slots serve as incentives for relaying. Formulates joint time slot exchange and relay selection as a mixed integer... Read more
Key finding: Analyzes space and time diversity schemes in cooperative communication systems employing amplify-and-forward relays combined with OFDM. Demonstrates that cooperative diversity significantly enhances diversity reception and... Read more
2. What are the impacts of hardware impairments and power control strategies on the reliability and error performance of decode-and-forward cooperative networks?
This theme investigates the degradation caused by practical hardware impairments (such as phase noise, I/Q imbalance, amplifier nonlinearities) and the role of adaptive power allocation in DF cooperative networks. It aims to quantify outage probability and error rates under realistic conditions and to design power control methods to minimize frame error rates, thereby enhancing network robustness and efficiency in fading environments.
Key finding: Derives closed-form outage probability expressions for amplify-and-forward and decode-and-forward dual-hop relaying systems considering non-ideal hardware impairments such as noise and gain errors. Shows that hardware... Read more
Key finding: Develops an adaptive power control scheme combined with partner selection to minimize frame error rate in decode-and-forward collaborative networks under block fading. The proposed convex deterministic and search-based... Read more
Key finding: Although this paper targets radio etiquette rather than hardware impairments per se, it addresses practical coordination challenges of diverse radio technologies causing interference. By proposing a common spectrum... Read more
Key finding: Proposes an adaptive power control method for turbo-coded decode-and-forward collaborative networks under Rayleigh block fading. Demonstrates through theoretical frame error rate expressions and simulations that power control... Read more
3. How do cooperative MAC protocols address challenges of relay selection, cooperation coordination, and network-level cooperation to optimize wireless multi-hop network performance?
The focus here is on medium access control (MAC) layer protocols tailored for cooperative communication. Critical issues include determining when to cooperate, selecting appropriate relay nodes, and coordinating transmission sequences efficiently. Additional emphasis is on session-based network-level cooperation models in cognitive radio networks (CRNs) aiming to maximize spectrum access opportunities by integrating primary and secondary user cooperation. Solutions target throughput enhancement, interference mitigation, and resource fairness in dynamic multi-hop and cognitive wireless environments.
Key finding: Provides a comprehensive overview of cooperative MAC protocols highlighting three core design challenges: when to cooperate, whom to cooperate with, and how to cooperate. Discusses relay selection, cooperative transmission... Read more
Key finding: Introduces the network level cooperative (NLC) principle in cognitive radio networks, where groups of secondary users collaboratively assist primary users session-by-session rather than frame-by-frame. Demonstrates that NLC... Read more
Key finding: Proposes a novel two-way double-relay selection strategy combined with orthogonal space-time coding and network coding, improving bit error rate and diversity gain while maintaining low decoding complexity. Analytical BER... Read more
Key finding: Presents a novel bandwidth allocation technique incorporating traffic priority and buffer load in cooperative relay nodes to meet QoS requirements. Provides analytical and simulation results showing that buffer load... Read more