In contrast with most existing dynamic spectrum access (DSA) paradigms which impose a `foe' relationship between primary users (PUs) and secondary users (SUs), this project investigates a new DSA paradigm which encourages PUs and SUs to help each other by trading spectrum ownership for improved overall performance. Specifically, this project designs two different schemes: (1) Give-And-Take (GAT) and (2) Network Coding + Secondary User Relay (NC+SR). The former does not need to change the radio or the protocol stack of PUs, while the latter assumes that PUs and SUs are capable of performing network coding. In GAT, SUs help deliver the traffic of PUs and in return are allowed to access licensed spectrum in a manner disruptive to PUs. The help constitutes the `give' part, and the disruptive spectrum accesses constitute the `take' part. In NC+SR, SUs help relay PU traffic between PUs. When relaying PU packets, SU relay nodes may encode SU packets onto PU packets via network coding, so that SU packets get a `free ride' on PU packets. Both GAT and NC+SR promise the improved performance of PUs as well as SUs. The project studies the issues of protocol design and performance optimization of the two schemes. Results from this project are expected to encourage incumbent licensed users to embrace DSA to further improve the capacity of wireless network. The project sustains a collaborative research team, and involves both graduate and undergraduate students, particularly the underrepresented minority students, in research.
Most existing dynamic spectrum access (DSA) paradigms impose a `foe' relationship between primary users (PUs) and secondary users (SUs), where the spectrum is exclusively used by either PUs or SUs. In particular, an SU may access the spectrum only when PUs cease using the spectrum, and the resurgence of PU traffic disrupts SU traffic. Such paradigms, although addressing the issue of spectrum scarcity, primarily benefit SUs without offering sufficient incentive to PUs for embracing DSA. Furthermore, to comply with stringent DSA policies, SUs are demanded to behave conservatively to sense and access the spectrum, resulting in an actual spectrum utilization significantly lower than what is feasible. In this project, we have proposed a new DSA paradigm which encourages PU and SU to help each other by trading spectrum ownership for improved overall performance. In particular, we have proposed two different schemes to realize this paradigm: (1) Credit-based Overlay and Interweave (CONI), and (2) Incentivized Cooperative Dynamic Spectrum Access Network (IC-DSAN). In CONI, SUs help deliver the traffic of PUs and in return are allowed to access licensed spectrum in a manner disruptive to PUs. In IC-DSAN, SUs help relay PU traffic between PUs. When relaying PU packets, SU relay nodes may encode SU packets onto PU packets via network coding, so that SU packets get a `free ride' on PU packets. We have studies the issues of protocol design and performance optimization of the two schemes. The proposed solutions have been evaluated via both simulation and numerical analysis. Results have demonstrated the effectiveness of the proposed solutions. For broader impacts, the research results have been integrated into the wireless networking curricula taught by the PI. In particular, we have disseminated the research results via web posting, seminars, conference presentations, and journal publications. The research also showed to further improve the capacity of wireless networks, and encourage incumbent licensed users to embrace DSA. With DSA, both civilian and military applications could be deployed seamlessly across national and international boundaries, resulting in significant societal, economical, and national security impacts.
