Eunhyun Kwon

A performance model for admission control in IEEE 802.16

For systems based on connection-oriented services, such as IEEE 802.16, call admission control (CAC) strategy is essential to provide a desired level of quality of service (QoS). Although many handoff-prioritized CAC schemes, which assume a fixed channel capacity, have been introduced, this assumption is not always valid for IEEE 802.16 that uses adaptive modulation and coding (AMC). With AMC, the modulation type of a user’s connection can be changed dynamically and the ongoing connection might fail due to the change of modulation. In this paper, we approach the AMC-induced CAC problem by focusing on the guaranteed connection. Three kinds of calls, new, handoff, and modulation-changed calls, are considered. We propose a modified guard channel CAC scheme that allows the modulation-changed and handoff calls to use the guard channel. Then we analyze a Markov model for the CAC scheme with long-term AMC in mind. According to the simulation results, the proposed approach reduces the call dropping probability for modulation-changed calls, which suggests the threshold of guard channels in IEEE 802.16 can be determined based on the proposed approach.

Comparison of symmetric and asymmetric routing for fixed two-hop cellular relaying network

In this paper, routing strategies for fixed two-hop cellular relaying networks are discussed in terms of area spectral efficiency. We consider symmetric and asymmetric routing in uplink and downlink. Simulation results show that relaying increases the average throughput in comparison with conventional cellular networks and the area spectral efficiency of asymmetric routing is slightly better than that of the symmetric

Markov Model for Admission Control in the Wireless AMC Networks

In wireless adaptive modulation and coding (AMC) systems, modulation type of a users connection can change and the ongoing connection might fail due to the change of modulation. In this paper, we approach the AMC-induced call admission control (CAC) problem by focusing on the guaranteed connection. Three classes of calls, new, handoff, and modulation-changed, are considered. We modify the guard-channel CAC scheme such that the modulation-changed calls, in addition to the handoff calls, are allowed to use the guard channel. Then we analyze a Markov model for the CAC scheme designed with long-term AMC in mind. The proposed approach will be an essential tool to determine the guard-channel thresholds in the wireless AMC networks.

Overload Control with Removal Algorithm for Real-time Flows in Wireless Networks

In the real-time multimedia applications, packet delay should meet stringent quality of service (QoS) requirements. Delay earliest due date (EDD) scheduler, originally designed for wireline data networks to operate under a maximum allowed delay, cannot be directly applied to wireless networks, due to the location-dependent errors and time-varying channel conditions. Several modifications of EDD scheduler have been proposed for wireless applications, which typically assume successful admission control, a condition hard to provide for wireless networks. In this paper, we propose a removal algorithm for downlink scheduler that is designed to perform under an overloaded situation. Simulation result shows that our algorithm outperforms the previous ones in the QoS guaranteed flows. Last, we discuss an extension of our works to integrate with admission control

Dynamic Resource Allocation in Cellular Radio Networks with Downlink Relaying

In this paper, we propose dynamic resource allocation with spatial reuse to improve total system throughput in multi-user system and multi-hop communication. The comparison of optimal and heuristic reuse scheme shows the heuristic reuse scheme is still good enough with low complexity. The simulation result shows that dynamic resource reuse scheme among fixed RSs increases the system throughput.

Performance Analysis of Wireless Relaying Networks Using Asymmetric Relay Path

In this paper, we present a concept and the related performance analysis for a wireless relay system which counts asymmetric relay path as one of the possible transmission paths. Most approaches of current literature to analyze relay system do not take into account the asymmetric relay path between uplink and downlink transmission. Asymmetric relaying may not be easy to apply to wireless networks but has potential to get more gain via throughput enhancement than symmetric relaying. We derive expression for the total link throughput including both uplink and downlink and verify that asymmetric relaying is valuable.

An overload-resilient flow removal algorithm for M-LWDF scheduler

In the real-time multimedia applications, packet delay should meet stringent Quality of Service (QoS) requirements Delay Earliest Due Date (EDD) scheduler, originally designed for wireline data networks to operate under a maximum allowed delay, cannot be directly applied to wireless networks, due to the location-dependent errors and time-varying channel conditions Several modifications of EDD scheduler have been proposed for wireless applications, which typically assume successful admission control, a condition hard to satisfy with wireless networks In this paper, we propose a removal algorithm for downlink scheduler designed to perform under overloaded situations Simulation results show that our proposed algorithm outperforms the conventional ones in the QoS guaranteed flows.