Youchan Jeon

A wireless access network based on WDM-PON for HMIPv6 mobility support

In this paper, an IP-based wireless access network is proposed, which is designed to support the hierarchical MIPv6 standard on the wavelength division multiplexed passive optical network access network in order to provide a fast and seamless handoff support. Two schemes for enhancing the mobility management are included in the proposed network’s infrastructure support. Firstly, the local-link channels between sub-networks are provided to improve the mobility management efficiency for the mobile nodes roaming between neighboring sub-networks. Secondly, the early route optimization scheme has been applied, which optimizes the mobility management process between the corresponding node and the home agent (HA), resulting in reduced bandwidth waste and long end-to-end packet delays, as well as lowering the heavy burden on the HA. The performance of the proposed mobility management scheme has been evaluated in terms of handoff delays, packet losses and transmission costs. The superior performance of the proposed scheme has been verified and compared to other schemes.

QoS-aware dynamic resource allocation for wireless broadband access networks

The development of the advanced wireless access technologies is focusing on the enhancement of mobile user satisfaction in terms of quality of service (QoS). As the number of mobile users increases, the amount of traffic passing through base station (BS) significantly increases so that the preplanned capacity of downlink or uplink can be exceeded from time to time resulting in the degradation of users’ QoS satisfaction. A way to utilize the downlink (DL) and the uplink (UL) of an orthogonal frequency division multiple access frame efficiently is therefore needed subject to users’ bandwidth demand which changes continuously over the time. In this paper, we propose a QoS-aware dynamic resource allocation (QDRA) scheme which dynamically adjusts the DL/UL ratio to allocate bandwidth for QoS support to users based on the usage statistics. The performance of the proposed QDRA scheme was examined by applying to the WiMAX standard specifications, to show its superiority of maintaining a higher QoS support for various classes of services compared to the pre-reported adaptive method.

Real-time white spectrum recognition for cognitive radio networks over TV white spaces

A key technical challenge in TV white spaces is the efficient spectrum usage without interfering with primary users. This paper considers available spectrum discovery scheme using in-band sensing signal to support super Wi-Fi services effectively. The proposed scheme in this paper adopts non-contiguous orthogonal frequency-division multiplexing (NC-OFDM) to utilize the fragmented channel in TV white space due to microphones while this channel cannot be used in IEEE 802.11af. The proposed solution is a novel available spectrum discovery scheme by exploiting the advantages of a sensing signaling. The proposed method achieves considerable improvement in throughput and delay time. The proposed method can use more subcarriers for transmission by applying NC-OFDM in contrast with the conventional IEEE 802.11af standard. Moreover, the increased number of wireless microphones (WMs) hardly affects the throughput of the proposed method because our proposal only excludes some subcarriers used by WMs. Additionally, the proposed method can cut discovery time down to under 10 ms because it can find available channels in real time by exchanging sensing signal without interference to the WM.

A seamless channel handover method for service continuity in super Wi-Fi

A key technical challenge in the Super Wi-Fi applications is how to provide a seamless Internet service even when a Super Wi-Fi user should give up the channel in use due to an active incumbent user. In this paper, we propose a channel handover method to support service continuity of Super Wi-Fi, in which AP selects an available channel and provides the channel information to MSs. Performance evaluation shows that the proposed scheme is superior to the conventional Wi-Fi in channel handover delay.

Rotation multiple-channel allocation scheme for seamless handoff in IEEE 802.11 WLANs

IEEE 802.11 Wireless LANs can provide broadband wireless data services without dealing with a cable in a limited area. However, when a MS moves to a neighboring AP, it has significant constraints on seamless mobile services. In this paper, we propose a rotational multiple-channel allocation scheme to manage mobility between APs that are equipped with multiple wireless interfaces, prohibiting from using the same channel as neighboring APs simultaneously. Performance evaluations show that the proposed scheme can achieve low handoff delay.

Seamless mobility provisioning by dual cross-linking method in WLAN

While the wireless local area network (WLAN) has been the most common technology for static indoor wireless services, its applications has limited performance in seamless mobile services because of its inherent static service transaction mechanisms. In this paper, we propose a mobility provisioning handoff method called dual cross-linking method to support seamless services in WLAN. A mobile node (MN) has two wireless interfaces and access points (APs) are controlled by a mobility management (MM) agent. In the area where the service areas of two adjacent APs are overlapped, one wireless interface is used to maintain the wireless services while the other interface searches for a next available AP. After finding a new AP, MN forms dual communication path from the MM to the MN so that the MN is ready to move to a newly found AP service area without service loss. Once the MN is moved to a new AP area, the first interface is disconnected leaving only one interface connection. It was proved that the proposed method can effectively reduce the handoff delay and packet loss through the analysis.

Seamless Handoff Support for Real-Time Applications in the Next-generation Wireless Access Network Architecture

In this paper, we propose the seamless handoff support scheme for broadband real-time services, which is based on the wavelength division multiplexing-passive optical network (WDM-PON) technologies and HMIPv6 in the wireless access network. Firstly, the proposed scheme provides fast and seamless handoff support through the proposed reliable and efficient local-link channels between sub-networks in WDM-PON-based wireless access network. Secondly, the proposed WDM-PON-based access network architecture develops broadband wireless access network that accommodates the emerging bandwidth-intensive applications and multimedia services. We evaluated the performance of the proposed mobility management scheme in terms of handoff delay and packet loss by performing a computer simulation.