Jilong Li

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.

An adaptive rate control for congestion avoidance 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 an adaptive rate control for congestion avoidance 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 between the network layer and the data link layer 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 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.

A Fast Adaptive Frequency Hopping Scheme Mitigating the Effect of Interference in Bluetooth Low Energy Networks

The speed and the efficiency of short range communication has increased with the evolution of wireless technologies i.e. Wireless Local Area Network (WLAN), ZigBee, and Bluetooth Low Energy (BLE). Especially, the BLE shows promising results in different fields such as Internet of Things (IoT), health-care, body area networks, etc. As a result of dramatic increase in the wireless device, the frequency interference in 2.4 GHz Industrial Scientific Medical (ISM) band has raised, resulting a higher packet loss. In this paper, we propose Fast Adaptive Frequency Hopping Scheme (FAFH) to mitigate the effects of interference in BLE. The proposed FAFH scheme immediately hops to a new channel without waiting for completion of the current connection event when the channel quality becomes worse by interference. The simulation results show that the FAFH performs better in dense wireless networks as well as improved performances comparing to AFH scheme.

Energy Efficient Sleep Scheduling for Wireless Sensor Networks

Recently, wireless sensor network (WSN) has become a formidable force in almost all areas of our everyday life. However, there are still many issues with wireless sensor networks among which is the energy problem. One of the numerous techniques that have been introduced as a way of solving the problem of energy deficit inherent in a WSN is sleep scheduling. Sleep scheduling allows sensor nodes to periodically take turns to sleep in order to minimize energy cost in a WSN. Apparently, Overemission in a WSN is one of the main causes of energy drainage in sensor nodes. Traditional schemes fail to take into consideration the sleeping timetable of other nodes; hence they let transmitter nodes repeatedly send RTS preamble packets and similar control packets to sleeping nodes. Our proposed sleep scheduling scheme addresses this problem from a whole new perspective using a system called Designated Sensor Node (DSN) mechanism. The DSN scheme significantly reduces flooding of the network with unnecessary control packets. The effect in turn leads to the minimization of unnecessary energy waste in a WSN.

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.

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.

A mobility management solution to support personal mobile station in wireless body mesh networks

In expanded service area of wireless mesh network to support mobility of the mobile station research is recognized as an important issue. The wireless body area networks promise to revolutionize health monitoring. 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.