Dong Hoi Kim

Capacity analysis of TDD cell sharing underutilized FDD uplink

This paper considers a two-layer hierarchical cell structure with the microcell employing the TDD system and the macrocell employing the FDD system. We determine the downlink and uplink capacities on the TDD system sharing the underutilized FDD uplink under the condition that the FDD and TDD systems share the same frequency band. Our analysis shows that in the course of planning the hierarchical cell structure, the optimum user distribution in the TDD cell can be found by utilizing the link balance and asymmetry between uplink and downlink in the TDD in order to improve the overall capacity.

Design and implementation of W-CDMA radio interface protocols using SDL development environments

This paper provides a methodology to design, implement and verify the access stratum protocol entities in WCDMA system using the SDL development environments. Simulation experiments are performed to check the verification of call handling logic, message transfer procedures and configuration parameter values in the designed SDL, in which are especially focused on the access stratum protocol entities including radio resource control, radio link control and medium access control. The simulation result indicates that the designed SDL guarantees the good consistency with the target test scenario, and has not any mismatching of logic flows as well as semantic errors in SDL design. The verified source codes were also generated from the designed SDL successfully.

Subchannel Multiplexing Scheme for Mobile Broadband Wireless Access Services in AMC-based OFDMA System

In the adaptive modulation and coding (AMC)-based orthogonal frequency division multiple access (OFDMA) system for broadband wireless service, a large number of users with short packets cause a serious capacity mismatch problem, which incurs resource under-utilization when the data rate of subchannel increases with a better channel condition. To handle the capacity mismatch problem, we propose an AMC-based subchannel multiplexing (ASM) scheme, which allows for sharing the same subchannel among the different simultaneous flows of the same user. Along with the ASM scheme, we also consider multi-class scheduling scheme, which employs the different packet scheduling algorithm for the different service class, e.g., packet loss rate-based (PLR) scheduling algorithm for real-time (RT) service and modified minimum bit rate-based (MMBR) scheduling algorithm for non-real-time (NRT) service. In the typical integrated service scenario with voice, video, and data traffic, we have shown that the proposed schemes significantly improve the overall system capacity.

Wireless packet scheduling for integrated services of real-time and non-real-time applications in mobile broadband wireless access system

This paper considers an opportunistic packet scheduling algorithm to support both RT and NRT service in mobile broadband wireless access system. The design objective of our proposed packet scheduler is to determine the optimal number of RT and NRT users based on the service charges (which differ depending on the type of services) in order to maximize the revenue, while at the same time satisfying their individual QoS requirements, i.e., the maximum allowable packet loss rate for RT traffic and the minimum reserved bit rate for NRT traffic. It takes an urgency of RT users into account only when their head-of-line (HOL) packet delays exceed the given threshold, which allows for maximizing the system capacity of NRT users. Evaluating the proposed approach in orthogonal frequency division multiple access/frequency division duplex (OFDMA/FDD)based mobile access system, it has been shown that, in terms of the number of RT and NRT service users, system capacity can be significantly improved.