Jeongbae Yun

AdaptiveScan: The Fast Layer-2 Handoff for WLAN

Recently, handoff is a critical issue for stations in IEEE 802.11-based wireless networks. In order to provide VoIP (Voice over IP) and real-time streaming applications for stations, handoff mechanism must be provided for reducing latency and seamless communication. However, the IEEE802.11 standards handoff is not appropriate to supply their QoS, because it is based on a full-scanning approach. Full-scanning spends too much time searching Access Point (AP). Therefore, the various pre-scan handoff protocols such as Sync Scan and Deuce Scan have been proposed. They perform scanning to find nearby APs before station is out of contact with AP, but they have much overhead for pre-scanning. Our handoff mechanism reduces the delay and overhead associated with link layer handoff by periodically scanning the channel groups. We prove that our per-scanning mechanism supports a faster handoff and has a lower overhead compared to the conventional schemes.

Path management scheme to support mobile station in wireless mesh networks for U-healthcare applications

In expanded service area of wireless mesh network to support mobility of the mobile station research is recognized as an important issue. Due to the mobile station move frequently to changing the path, data loss and network performance degradation are often occur, such as the service broken. In the existing research of support mobility, the Layer 3 or mobility is required, but it may cause the backup server overhead. This paper is based the 802.11s, the proposed scheme supports station mobility without any additional elements by using Layer 2.

A Self-Adjustable Rate Control in Wireless Body Area Networks

The convergent feature of traffic in wireless body area networks (WBANs) makes congestion in certain areas which are the place of events and/or the location of sensor nodes near a sink. Congestion brings packet loss, retransmission, and delay at the node and it also causes the consumption of additional energy. Therefore there is no doubt that congestion needs to be controlled efficiently. In this paper, we suggest a self-adjustable rate control in WBANs. Our scheme performs rate control dynamically each node based on a predication model which uses rate function including congestion risk degree and valuation function, without requiring congestion detection and congestion notification steps. We carry out the operation of our scheme and have demonstrated our rate control to be efficient. We also show that the negative effects from network congestion can be greatly mitigated as compared with a no rate control mechanism.

A Repeated Group Sequence Rendezvous Scheme for Cognitive Radio Networks

In cognitive radio network, two or more nodes need to establish a link on an available channel when they want to transmit a data. Rendezvous is a process that nodes explore the available channels to establish a link when a pair of nodes wants to communicate with each other. The method of finding a common channel is a challenging problem. To use of a dedicated control channel can be a solution to find the common channel but it may result in a bottleneck and create a single point of failure. In this letter, we present a rendezvous sequence scheme to find a common channel. The proposed scheme guarantees the successful rendezvous within the bounded time.

Traffic Classification Approach Based on Support Vector Machine and Statistic Signature

As network traffic is dramatically increasing, classification of application traffic becomes important for the effective use of network resources. Classification of network traffic using port-based or payload-based analysis is becoming increasingly difficult because of many peer-to-peer (P2P) applications using dynamic port numbers, masquerading techniques, and encryption. An alternative approach is to classify traffic by exploiting the distinctive characteristics of applications. In this paper, we propose a classification method of application traffic using statistic signatures based on SVM (Support Vector Machine). The statistic signatures, defined as a directional sequence of packet size in a flow, are collected for each application, and applications are classified by SVM mechanism.

Movable Rendezvous Channel Selection for Distributed Cognitive Radio Networks

Cognitive Radio (CR) technology has emerged as a suitable technology for providing a possible solution to the lack of the spectrum problem. For this, CR has to identify opportunistically and heuristically the available spectrum, in which primary users (PUs) do not exist on it. It is critical that the secondary users (SUs) use the vacant portions of the spectrum without causing a loss of efficiency for PUs and without any interference effects on PUs in CR networks. Among the recent research on CR MAC protocols, we focused on the selection of rendezvous channel (RC), which is the core of the Cognitive MAC (C-MAC) protocol. In this paper, we propose a new RC selection scheme that can always maintain only one RC at a certain time. The design and performance of our scheme is presented and evaluated in this paper.

Analysis and Proposal of Wireless Mesh Network's Routing Metric for WBAN

Existing routing protocols such as AODV were used to simplify the shortest path metric. It assumes that all link quality must be the same. It does not consider link quality such as bandwidth, packet loss rate, packet size, etc. Several performance metrics that consider different link quality for WMNs such as ETX and ETT. Although, these metrics can provide more effective performance than the hop count metric, they did not consider the backbone feature of WMNs. In this paper, a new routing metric for load balancing in WMNs is proposed. These routing metric is called Expected Transmission Time - Load Balancing (ETT-LB) and this metric is using ETT and Bandwidth usage.

An application dependent and sequential scanning scheme for vertical handover management in heterogeneous wireless networks

A mobile device with multiple interfaces consumes more energy for scanning of available networks during handover compared with one having a single interface. As the number of available networks increases, the discovery and selection of an optimal network consumes much energy for scanning, therefore, reduces battery life time. To cope with such problems, we propose an energy efficient scanning scheme for vertical handover management in heterogeneous networks. The proposed scheme employs a sequential scheduling strategy to avoid unnecessary scan, and controls scanning period depending on the type of application running on a Mobile Node (MN) to speed up discovery process. Performance evaluation shows that the proposed scheme uses less energy compared with the periodic and adaptive scanning procedures.

An Efficient Propagation Method for Emergency Messages in Urban VANETs

If an accident vehicle propagates emergency messages to other vehicles close to it, the other drivers may realize and avoid the accident spot. In this letter, we propose a broadcast scheme to propagate emergency messages fast in urban VANETs (Vehicular Ad-Hoc Networks) with the help of GPS (Global Position System). In our scheme, a transmitting vehicle chooses the farthest node as the next relay vehicle to propagate emergency messages. And, we suggest an algorithm for intersection recognition and SCF (Store-Carry-Forward) task by taking advantage of periodic hello packets to reduce the propagation time and enhance the delivery ratio.

A Scheduling Scheme for Early Detection of Primary User in Cognitive Radio Networks

Cognitive Radio (CR) technology has emerged as a way to improve the overall spectrum usage by exploiting spectrum opportunities in both licensed and unlicensed bands. The Medium Access Control (MAC) protocol in CR network should support interference control for Primary Users (PU) and collision avoidance amongst Secondary Users (SU). In this paper, we propose a scheduling scheme for CR MAC protocol to detect PU as fast as possible, and demonstrate performance of our scheme through a simulation.