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 MRSSand DMRSS-based handoff algorithms can reduce the number of unnecessary handoffs up to 44% and save battery power up to 75%.

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 user's 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.

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.

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.