Yung-Mu Chen

SCTP-based handoff based on MIH triggers information in campus networks

Wireless VoIP services require not only end-to-end transmission delay between end users but also small handoff delay between heterogeneous networks. This study designs and implements a SCTP-based mobile VoIP system in a campus network. The multi-homing capability and dynamic address configuration extension of SCTP are applied in the VoIP system to provide seamless handoff. Also, IEEE 802.21 specifies 802 media access-independent mechanisms (MIH) to optimize handoffs between heterogeneous 802 systems and cellular systems. The proposed VoIP system combines SCTP and 802.21 MIH function to improve the performance of handoff in a campus network

MACD-Based Motion Detection Approach in Heterogeneous Networks

Optimizing the balance between handoff quality and power consumption is a great challenge for seamless mobile communications in wireless networks. Traditional proactive schemes continuously monitor available access networks and exercise handoff. Although such schemes achieve good handoff quality, they consume much power because all interfaces must remain on all the time. To save power, the reactive schemes use fixed RSS thresholds to determine when to search for a new available access network. However, since they do not consider user motion, these approaches require that all interfaces be turned on even when a user is stationary, and they tend initiate excessive unnecessary handoffs. To address this problem, this research presents a novel motion-aware scheme called network discovery with motion detection (NDMD) to improve handoff quality and minimize power consumption. The NDMD first applies a moving average convergence divergence (MACD) scheme to analyze received signal strength (RSS) samples of the current active interface. These results are then used to estimate users motion. The proposed NDMD scheme adds very little computing overhead to a mobile terminal (MT) and can be easily incorporated into existing schemes. The simulation results in this study showed that NDMD can quickly track user motion state without a positioning system and perform network discovery rapidly enough to achieve a much lower handoff-dropping rate with less power consumption.

Adaptive Momentum-Based Motion Detection Approach and Its Application on Handoff in Wireless Networks

Positioning and tracking technologies can detect the location and the movement of mobile nodes (MNs), such as cellular phone, vehicular and mobile sensor, to predict potential handoffs. However, most motion detection mechanisms require additional hardware (e.g., GPS and directed antenna), costs (e.g., power consumption and monetary cost) and supply systems (e.g., network fingerprint server). This paper proposes a Momentum of Received Signal Strength (MRSS) based motion detection method and its application on handoff. MRSS uses the exponentially weighted moving average filter with multiple moving average window size to analyze the received radio signal. With MRSS, an MN can predict its motion state and make a handoff trigger at the right time without any assistance from positioning systems. Moreover, a novel motion state dependent MRSS scheme called Dynamic MRSS (DMRSS) algorithm is proposed to adjust the motion detection sensitivity. In our simulation, the MRSS- and DMRSS-based handoff algorithms can reduce the number of unnecessary handoffs up to 44% and save battery power up to 75%.

Adaptive VoIP Service QoS Control based on Perceptual Speech Quality

Integrated environment of wireless network can provide a ubiquitous and continuous communication for voice over Internet protocol (VoIP) service. However, the major problems, which VoIP performs over wireless networks, are varying delay of each packet, high packet loss rate and handoff. This paper proposed an adaptive QoS playout (AQP) algorithm to offer a high quality wireless VoIP service. AQP integrates the effect of dejitter buffer control, retransmission, and handoff delay based on the E-model. Simulation results show that AQP can reduce the lateness loss rate and improve speech quality under high frame error rate when the wireless link has small end-to-end network delay and also performs well when a handoff occurs.

Momentum-Based Motion Detection Methodology for Handoff in Wireless Networks

This paper presents a novel motion detection scheme by using the momentum of received signal sstrength (MRSS) to improve the quality of handoff in a general wireless network. MRSS can detect the motion state of a mobile node (MN) without assistance of any positioning service. Although MRSS is sensitive in detecting users motion, it is static and fails to detect quickly the motion changes of users. Thus, a novel motion state dependent MRSS scheme called dynamic MRSS (DMRSS) algorithm is proposed to address this issue. Extensive simulation experiments were conducted to study performance of our presented algorithms. The simulation results show that MRSS and DMRSS can be used to assist a handoff algorithm in substantially reducing unnecessary handoff and saving power.

Reducing Power Consumption in Network Discovery with Motion Detection in Heterogeneous Wireless Networks

Seamless handoff is critical to providing high-quality services for mobile users. Before handoff, a mobile terminal (MT) must be aware of the impending handoff and determine what other wireless networks are available in time. In the network discovery stage, an MT must activate its interfaces for base station search, association, AAA (authentication, authorization, accounting), address acquisition, and so on. Therefore, if insufficient time is available for the MT to perform these procedures, then the connection will be disrupted. However, frequent interface activation can cause considerable battery drain. This paper presents a network discovery algorithm with motion detection, NDMD, to solve these problems. NDMD can simply use the received signal strength (RSS) to predict a users motion without the assistance of a positioning system. Based on the predicted moving behavior, an MT can perform network discovery in time to reduce handoff dropping rate and prevent unnecessary activation of its interfaces to save the battery power. Simulation results show that NDMD can effectively detect user behavior, reduce power consumption in network discovery, and improve handoff quality.

An overlay resource monitor system

This study proposes an overlay resource monitor system which is highly scalable, extendable and self-configurable called ORMAN. The monitor system is build upon a cluster-based topology P2P system and consisted of a monitor agent. The monitor agent contains a set of sensors, called information collection modules (ICMs). ICMs collect the states of monitored attributes, record the attributes and compute the statistic values of monitored attributes in each node. ORMAN provides several resource management mechanisms, such as event notification, admission control, fault tolerance and load balance. ORMAN also provides a set of APIs for developers to design customized ICMs and plug them into system on the fly

SSTIF: Stable Self-Organized Infrastructure-based Peer-to-Peer Network

This study presents a stable self-organized infrastructure-based (SSIF) P2P networking scheme to build an infrastructure-based model (IFM) P2P network with both location aware and stable clustering features. SSIF employs clustering and infrastructure node election to construct an IFM P2P network. The clustering divides peers into many clusters according to their geographical proximity. A novel positioning scheme called dynamic hybrid network positioning (DHNP) was proposed to offer accurate peer coordinates. SSIF makes a peer join a cluster with gravity close to its position. SSIF also associates each peer with a novel metric power that represents the capability and stability of the peer. According to the power of peers, peers are elected as cluster leaders or infrastructure nodes to offer stable and high-performance services in the P2P network. Finally, SSIF adopted a novel concept called confederation to achieve the stability of a search domain to offer efficient resource search. Simulation results confirm that SSIF does offer very stable and high-performance service than previous P2P systems.

PFC: A New High-Performance Packet Filter Architecture

As communication technology has advanced, network capacity has grown exponentially in recent years. The performance of network monitoring tools is becoming more important as they must process many more packets in a unit of time than they ever did before. A common core component of any network monitoring tool is a packet filter that processes every packet header and passes those packets according to filter rules, to user spaces for further processing. This study presents a packet filter architecture called Packet Filter Cache (PFC) to improve the performance of existing packet filters. The PFC architecture adds a filter rule cache in front of an existing packet filter. Rather than caching the instruction set as in warm caching, the filter rule cache stores the hash value of a filter rule as a hash table entry that can be found in a O(1) memory access. By exploiting the hash lookup speed, PFC can boost filtering performance using only a small cache size. Additionally, PFC also caches unmatched packet flows to achieve a high hit rate. PFC is only a cache mechanism and is added before a traditional packet filter, so it does not depend on the re-engineering of existing filter module. It can therefore be applied to most packet filters. Simulation reveals that PFC can improve the processing time by a factor of around four, at a cache hit rate of 70%.

QMNF: QoS-aware multicasting routing protocol using N-hop dominating flooding approach on active network

In this investigation, we propose a new multicast protocol, QoS multicasting routing protocol on N-hop dominating flooding (QMNF), based on a layered routing architecture of active network approach. In this architecture, QMNF invites the N-hop flooding component and the shortest path routing table from OSPF by open signaling interfaces, floods the path-finding messages in capsules and employs two-pass resource reservation scheme to avoid unnecessary resource reservation. In our simulation, we compare the performance of QMNF with a traditional flooding algorithm, an optimal flooding algorithm, PIM and QMBF. The simulation results confirm that QMNF has the high success rate, the better resource utilization and the traffic can be distributed evenly in a network