Yeon-Woo Lee

Hybrid Division Duplex System for Next-Generation Cellular Services

The paper proposes a new duplexing scheme, which is called the hybrid division duplex (HDD), that is suitable for fourth-generation mobile communication systems. The proposed mobile communication system is much more flexible and efficient in providing asymmetric data service and managing intercell interference by exploiting the advantages of both time division duplex (TDD) and frequency division duplex (FDD) schemes. The HDD scheme has a pair of frequency bands such as the FDD, performing a TDD operation using one of the bands in such a manner that allows for simultaneous FDD and TDD operations. Considering the properties of the HDD system architecture, frequency hopping orthogonal frequency division multiple (OFDM) access is adopted in one band for the TDD operation and code division multiple access (CDMA) in the other band for the FDD uplink operation. The important advantage of the HDD scheme is the robustness against cross time slot interference that is inherent to the TDD system, which is caused by the asynchronous downlink/uplink switching boundaries among all neighbor cells. From the simulation results, the proposed system can achieve approximately 7% and 30% improvement with regard to the downlink and uplink throughput, respectively, as compared to the conventional TDD system under cell-independent downlink/uplink traffic asymmetries. It demonstrates that the HDD scheme is a viable solution for future communication systems that are projected to have a cell-independent asymmetric-traffic-supported hierarchical cell structure.

A dynamic spectrum allocation between network operators with priority-based sharing and negotiation

This paper discusses a spectrum sharing problem in multiple network operators (NOs). Most of the previous works have illustrated the dynamic spectrum allocation (DSA) gain achieved by utilizing the time or regional variations in traffic demand between NOs. In this paper, we introduce the functionalities required for the entities related with the spectrum allocation and propose a spectrum allocation algorithm. In the proposed spectrum allocation algorithm, the priority between NOs and the priorities of multiple class services are incorporated into the spectrum sharing metric (SSM), while also accommodating the urgent bandwidth request by proposing a negotiation procedure. It is shown that the proposed scheme allocates the spectrum dynamically, reflecting the long-term occupation ratio between NOs and the priorities of multiple class services