Sensors_**2009**, \(9\), 5715-5739; doi:10.3390/s90705715  
_Series_  
**ISSN 1424-8220**  
www.mdpi.com/journal/sensors  
_Article_  
**Adaptive Momentum-Based Motion Detection Approach and Its Application on Handoff in Wireless Networks**  
**[PERSON] \({}^{\star}\), [PERSON] and [PERSON]**  
Department of Computer Science & Engineering, Yuan Ze University, No. 135 Yuan-Tung Rd., Chung-Li, Taoyuan, 32003, Taiwan  
E- Mails: [EMAIL_ADDRESS] (Y.-M.C. ); [EMAIL_ADDRESS] (C.-H.H.) \({}^{\star}\) Author to whom correspondence should be addressed; E-Mail: [EMAIL_ADDRESS]; Tel. : +886-3-4638800 ext. 2370; Fax: +886-3-4638850  
_Received: 15 June 2009; in revised form: 3 July 2009 / Accepted: 15 July 2009 / Published: 17 July 2009_  
**Abstract:** 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%. **Keywords:** exponentially weighted moving average; handoff; MRSS; momentum; motion detection; ping-pong effect; received signal strength Introduction  
With the rapid development of wireless network technologies, the next generation wireless network is expected to integrate various wireless access technologies, such as Ultra-Wideband, WLAN, WiMAX, UMTS and 3 GPP LTE to provide an all-IP communication environment and support various IP-based services, such as WWW, VoIP, IPTV, vehicle safety inspection [1; 2], intelligent transport systems [3], security monitor [4; 5] and homecare health, to mobile users anytime anywhere. In the environment, communication systems with various coverages could overlap one another. When a multi-mode mobile node (MN) is moving out of the coverage of its current serving access point (AP) or base station (BS), it needs to perform a vertical handoff or a horizontal handoff to switch its connections from the current serving AP to another AP to avoid connection interruption. Therefore, the performance of handoff mechanism significantly affects the quality of communication services. The handoff procedure can be divided into three stages [6]: handoff initiation, handoff decision and handoff execution. In the first stage, an MN turns on all its wireless interfaces to discover which wireless networks are available. Then, the MN selects the best network. Finally, the MN executes a handoff process to switch its connection from the current access network to the one newly selected while minimizing handoff delay. In the past, several network discovery schemes [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27] have been proposed to reduce the handoff delay and the packet loss rate. These network discovery schemes can be classified into received signal strength (RSS) threshold-based methods [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19] and motion-aware methods [20; 21; 22; 23; 24; 25; 26; 27]. The RSS threshold-based schemes make an MN turns on all interfaces for network discovery only when the RSS of the current active interface is below a pre-defined threshold. However, power consumption and handoff dropping rate are in a tradeoff.