Jangkyu Yun

A Channel Switching Scheme for Avoiding Interference of between IEEE 802.15.4 and Other Networks

The key features of low-rate wireless personal area networks (LR-WPAN) are low data rate, low cost, and low power consumption. The LR-WPAN is very useful in many applications such as detection, remote control, tracking and monitoring. But, there are many different networks (WLAN, Bluetooth, HR-WPAN, LR-WPAN ) in the same unlicensed 2.4 GHz ISM band. So, much interference happens. In this paper, we propose a cognitive radio based channel switching mechanism for avoiding interference of between IEEE802.15.4 and other networks.

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.

A Routing Metric for Load Balance in Wireless Mesh Networks

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 (ETTLB) and this metric is using ETT and Bandwidth usage.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.

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.

Dynamic Channel Adjustable Asynchronous Cognitive Radio MAC Protocol for Wireless Medical Body Area Sensor Networks

Medical body area networks (MBAN) impose several requirements to the medium access control layer which have various contexts: energy efficiency, QoS providing, reliability. And a cognitive radio (CR) network should be able to sense its environment and adapt communication to utilize the unused licensed spectrum without interfering with licensed users. As CR nodes need to hop from channel to channel to make the most use of the spectrum opportunities, we consider asynchronous medium access control (MAC) protocols to be solution for these networks. The DCAA-MAC protocol presented in this paper has been designed has been designed specifically for wireless body area network with cognitive radio capability. The DCAA-MAC protocol has energy-efficiency, low latency, and no synchronization overhead by provide asynchronous and fast channel switching. Analytical models are shown to perform at low energy consumption, to scale well with network size.

Self-organized multi-metric routing for QoS in wireless mesh networks

Wireless mesh networking is emerging as an important architecture for the future generation of wireless communications systems. The challenging issue in WMNs is providing Quality of Service (QoS). So, this paper proposes a multiple-metric routing scheme for QoS in WMNs using a system of active networks. The Active Network paradigm offers the attractive capability of being able to carry executable payloads that can change the characteristics of a given platform. In other words, network nodes not only forward packets, but also perform customized computation on the packets flowing through them. It provides a programmable interface to the user.

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.

An Implementation of AODV Testbed with Multi-metrics

The Ad-hoc On-demand Distance Vector (AODV) is the most typical reactive routing protocol in MANET. It has been extensively studied through not only computer simulations but also implementations on real network. In this paper, an implementation of AODV routing protocol with multi-metric was presented. In the implementation, an Uppsala University routing protocol, AODV-UU was modified in order to apply multi-metrics. Moreover, both AODV-UU and modified AODV-UU were implemented within a Linux-based test bed: a real ad-hoc network. Finally, the performance of both protocols was evaluated experimentally.

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.

A Multiple-Metric Routing Scheme for QoS in WMNs Using a System of Active Networks

Wireless mesh networking is emerging as an important architecture for the future generation of wireless communications systems. The challenging issue in WMNs is providing Quality of Service (QoS). So, this paper proposes a multiple-metric routing scheme for QoS in WMNs using a system of active networks. The Active Network paradigm offers the attractive capability of being able to carry executable payloads that can change the characteristics of a given platform. In other words, network nodes not only forward packets, but also perform customized computation on the packets flowing through them. It provides a programmable interface to the user.