Hyunduk Jung

A seamless voice call handover scheme for next generation cellular network

This paper proposes the world first complete voice call handover scheme between the 3G LTE and 3G CS systems. To achieve seamless handover, a powerful network entity called FW_MME is proposed. Features of the FW_MME contribute to reducing handover service interruption time; hence the resulting voice call handover performance is also improved. The evaluation result shows that the proposed FW_MME exclusively meets the strict service interruption time requirement which is smaller than 300 ms, whereas other conventional handover schemes spend more than twice large time in voice call handover.

Downlink resource management for OFDMA femtocells using stochastic subchannel allocation

The Femtocell becomes an effective solution to support indoor high data rate services. The macrocell systems require expensive costs to improve the performance of indoor users. Although the advantage of the femtocells, the co-channel interference between the femtocells and the macrocells is the most significant problem to deploy femtocells. In this paper, a novel downlink resource management algorithm for OFDMA femtocells using the stochastic subchannel allocation is proposed. The stochastic subchannel allocation selects available subchannels used by the femtocells to reduce the interference. Monte-Carlo simulation results show the performance of the proposed algorithm in terms of the average user throughput.

Interference-Aware Downlink Resource Management for OFDMA Femtocell Networks

Femtocell is an economical solution to provide high speed indoor communication instead of the conventional macro-cellular networks. Especially, OFDMA femtocell is considered in the next generation cellular network such as 3GPP LTE and mobile WiMAX system. Although the femtocell has great advantages to accommodate indoor users, interference management problem is a critical issue to operate femtocell network. Existing OFDMA resource management algorithms only consider optimizing system-centric metric, and cannot manage the co-channel interference. Moreover, it is hard to cooperate with other femtocells to control the interference, since the self-configurable characteristics of femtocell. This paper proposes a novel interference-aware resource allocation algorithm for OFDMA femtocell networks. The proposed algorithm allocates resources according to a new objective function which reflects the effect of interference, and the heuristic algorithm is also introduced to reduce the complexity of the original problem. The Monte-Carlo simulation is performed to evaluate the performance of the proposed algorithm compared to the existing solutions.

Proportional Delay Differentiation in Multi-hop Wireless Networks

In this paper, we propose MWTP (Multi-hop Waiting Time Priority) scheduler to guarantee proportional delay differentiation in a multi-hop wireless network with contention- based MAC protocol. The existing single-hop delay differentiation schedulers can not differentiate the contention delay suffered at multi-hop links, and whole delay differentiation accuracy is destroyed in the multi-hop wireless communications. MWTP marks packets with departing time at the upstream node to decide scheduling order at the downstream node. The marked departing time becomes a reference point of waiting time in the scheduling process. Analysis and simulation results support that MWTP guarantees more accurate delay differentiation than existing schedulers.

Route optimization for network mobility with tree-based care of address

Network Mobility (NEMO) supports the movement of some part of the network that a group of the Mobile Nodes (MNs) or the Mobile Routers (MRs) moves together. To support NEMO, the NEMO basic support protocol (NBSP) was proposed [1]. In the nested mobile network, however, the NBSP exhibits pinball routing problem. As the degree of nesting increase, the problem becomes more serious. In this paper, we propose a new NEMO management scheme using Tree-based Care of Address (TCoA) and Mobile Network Prefix (MNP). In proposed scheme, all the MRs belonging to the Root-MR in the nested mobile network configure their care-of addresses (CoA) based on the MNP of Root-MR. It mitigates the pinball routing problem. Performance analysis indicates that proposed scheme can reduce end-to-end packet delay and handoff delay.

A CICQ Switch Architecture Using Blocking Avoidance & Virtual Threshold Scheme for QoS Guaranteed Multicast Service

Recently the multicast based contents transmission is rapidly increasing due to the various multimedia services and the importance of switching technology to handle it is increasing as a consequence. Though the CICQ architecture has advantages that reduction of HoL blocking probability and simple scheduling using cross point buffer, it has disadvantage that the processing rate of multicast traffic can be significantly degraded corresponds to the traffic load increment. Several schemes have been proposed to solve this problem however they still can`t provide enough processing ratio for multicast traffic. Therefore this paper proposes the BA cell assignment scheme and the VT scheme, and the processing rate of multicast traffic can be guaranteed by reducing the HoL blocking probability of multicast traffic and reservation of cross point buffer. Also simulation results verify that using the proposed scheme, the QoS of multicast service can be improved.

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.