Dual-mode Mobile Research Articles

The impact of IMS mobility management with google mobile phone on quality of experience

The widespread of a Wireless Local Area Network (WLAN) access network in residential areas provides low-cost and high-speed access to the Third-Generation Partnership Project (3GPP) services for end users. This has virtually made WLAN to be a complementary access network to Universal Mobile Telecommunications System (UMTS). The interoperability of WLAN and UMTS is made possible with the use of a mobility management mechanism in IP Multimedia Subsystems (IMS) architecture. Current problems in mobility management mechanisms are found in device mobility such as mobile phones. Such problems affect several layers and disrupt services. In this paper, IMS mobility management mechanisms with G1 mobile phone as an IMS client testbed is implemented, and its impact on the Quality of Experience (QoE) during end-to-end VoIP call session and its conformity to the 3GPP requirements of seamless service continuity is evaluated. The QoE driven mobility management mechanism is then proposed and evaluated to improve the QoE and to meet the 3GPP requirements of seamless service continuity during the handover between UMTS and WLAN access networks. Preliminary results show that there is an improvement in QoE and the requirements of 3GPP service continuity were met. The proposed Quality of Service (QoS) driven mobility management mechanism will help in the development of dual-mode mobile handsets with QoE adaptability.

날갯짓 기능을 가진 도약 로봇의 종방향 안정성 해석

Due to safety concerns, it is difficult for human beings to access a disaster area to rescue survivors. Even a robot may fail to conduct a rescue mission if it can use only one mode of transportation. A robot with multiple modes of transportation may have a greater chance to successfully search for survivors within the golden time. In previous work to develop a dual-mode mobile robot, we introduced a jumping robot assisted by flapping wings called Jump-flapper. The robot was equipped with one driving motor and dual transmissions to operate a winching mechanism for elastic energy storage used for jumping and flapping mechanisms to provide additional thrust in the air immediately after jumping. In this paper, we analyzed the stability of Jump-flapper using a linearized equation of motion. With commercial software ANSYS-Fluent, computational fluid dynamics were used to compute stability derivatives included in the system matrix. The eigenvalue analysis finds that the robot eventually becomes unstable due to two unstable oscillatory modes. For a more accurate estimation of vertical jumping height, the drag of the robot body was included in the equation. Consequently, the equation of motion became non-linear and we used the Euler method to solve the non-linear equation. The estimated vertical jumping height agreed with the prediction by a simple model and with the measured height from our previous work.

Portable Dual Mode Mobile Charger with Hand Crank Generator and Solar Panel

<p>A new method of charging a mobile phone with the help of hand crank generator, and solar panel is being presented in this paper. Solar panel is useful during daylight and hand crank generator can be used at night. So this is a dual mode charger which is operated in either way and both ways do not consume system power. This type of mobile charger is very useful when traveling because it uses solar panel to convert renewable source light into electricity. Mechanical hand crank generator is used which converts mechanical energy into electrical energy and then charges the mobile. No electrical sources are needed for it. Our design uses a compound gear train for transformation of the mechanical energy generated from the hand crank to the generator. For that reason it is convenient as well as economical to use such kind of mobile charger for our mobile phone.</p>

Implementation of an SDR system using an MPI-based GPU cluster for WiMAX and LTE

This paper presents an implementation of a 2 × 2 Multi-Input Multi-Output Software Defined Radio (SDR) Base Station system using a Message Passing Interface (MPI)-based Graphic Processing Unit (GPU) cluster as its modem processor for a high-speed data processing. Recently, GPUs have been widely researched especially for SDR systems because of their capability for exploiting parallel processing using a large number of Arithmetic Logic Units. MPI-based GPU clusters have been adopted in order to further increase performance capability. From our experimental results, it has been found that the implemented system consisting of three GPU nodes can enhance the modem speed by more than 2.5 times compared to a single GPU system. A dual-mode Mobile Device (MD) prototype supporting Worldwide Interoperability for Microwave Access and Long Term Evolution communications systems is implemented. In our design, one of the two waveforms can automatically be selected by the MD itself using a dual-mode controller that determines the reconfiguration of the MD modem depending on the received signal quality.

Radiation efficiency enhancement using lumped inductors for dual-mode mobile phone

This letter proposes a radiation efficiency enhancement technique using a lumped inductor for a dual-mode mobile phone.Two planar inverted-F antennas (PIFAs) with a collinear arrangement are used for dual-mode operation at the CDMA band of 824–894 MHz and GSM band of 880–960 MHz. Each antenna is separately connected to a lumped inductor of 4.7 nH. The electric field is more confined on each inverted-F section at its operating band in this configuration and the coupling between PIFAs is less than −10 dB. The simulated and measured results show that radiation efficiency of the proposed antenna is improved by up to 33%. The radiation patterns are similar to those of a dipole antenna with slightly tilted main beam directions due to the PIFA placement. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1011–1013, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26735

IPv6 based relay gateway protocol in hybrid networks

During the past few years, WMAN (Wireless Metropolitan Area Network) and WLAN (Wireless Local Area Network) provided fast, convenient and reliable solution for all kinds of users. With the development of the communication technology, the future wireless networks will allow mobile users access Internet anywhere, anytime. Therefore, it is a natural trend to combine different wireless networks to provide a seamless roaming for users. It is feasible for mobile terminal which have multiple modes to handoff between different networks. A relay gateway protocol for the WLAN-mode nodes (mono-mode WLAN nodes and dual-mode nodes) in the hybrid network of IEEE 802.16 WMANs and IEEE 802.11 WLANs is proposed to provide wider mobility. Dual-mode mobile nodes with good service can provide WLAN links to nearby WLAN-mode nodes with bad service or out of the WLAN coverage. Simulation results show that the relay gateway scheme can improve network performance of the hybrid networks. Moreover, the relay gateway method can bring additional service coverage and increase the capacity of WMANs and WLANs.

Radiation efficiency improvement for dual-mode mobile phone using a slot on a ground plane

A dual-band mobile phone antenna with dual feeders is proposed to improve antenna radiation efficiency in the CDMA band of 824–894 MHz and the GSM band of 880–960 MHz. The proposed antenna consists of two planar inverted-F antennas and a common ground plane with a slot. The electric fields are more confined on each radiating element region at each band in this configuration. Measured results show that radiation efficiencies of the proposed antenna are improved by up to 20% compared to those of the antenna without a slot.

Embedded system architecture for an WLAN-based dual mode mobile phone

This paper presents new embedded system architecture (ESA) for improving the voice quality in a WLAN/Cellular dual-mode mobile phone. The proposed architecture is based on a dual-core scheme and its main functional blocks are composed of VoIP Remote Procedure Call (VRPC), an audio bridging scheme, and a Server-Assisted Call Management (SACM) algorithm. In order to illustrate the aims of the proposed approach, prototype systems are implemented, and evaluated by measuring average Mean Opinion Score (MOS), and Mouth-To-Ear (M2E) delay. The experimental results show that the proposed approach results in greatly improved voice quality.

Handoff with DSP Support: Enabling Seamless Voice Communications across Heterogeneous Telephony Systems on Dual-Mode Mobile Devices

In this paper we investigate the problem of voice communications across heterogeneous telephony systems on dual-mode (WiFi and GSM) mobile devices. Since GSM is a circuit-switched telephony system, existing solutions that are based on packet-switched network protocols cannot be used. We show in this paper that an enabling technology for seamless voice communications across circuit-switched and packet-switched telephony systems is the support of digital signal processing (DSP) techniques during handoffs. To substantiate our argument, we start with a framework based on the session initiation protocol (SIP) for vertical handoffs on dual-mode mobile devices. We then identify the key obstacle in achieving seamless handoffs across circuit-switched and packet-switched systems, and explain why DSP support is necessary in this context. We propose a solution that incorporates time alignment and time scaling algorithms during handoffs for supporting seamless voice communications across heterogeneous telephony systems. We conduct testbed experiments using a GSM-WiFi dual-mode notebook and evaluate the quality of speech when the call is migrated from WiFi to GSM networks. Evaluation results show that such a cross-disciplinary solution involving signal processing and networking can effectively support seamless voice communications across heterogeneous telephony systems.

Modeling power saving for GAN and UMTS interworking

3GPP 43.318 specifies the generic access network (GAN) for interworking between wireless local area network (WLAN) and Universal Mobile Telecommunications System (UMTS) core network. A dual-mode mobile station (MS) is equipped with two communication modules to support both WLAN and UMTS radio technologies, which shortens the battery lifetime of the MS. This paper proposes an analytical model and conducts simulation experiments to study the power consumption of dual-mode MSs in terms of the power consumption indicator and mean packet waiting time. Our study provides guidelines for designing WLAN-UMTS dual-mode MSs.

Moving toward end-to-end support for handoffs across heterogeneous telephony systems on dual-mode mobile devices

More and more handsets manufactured today are being equipped with WLAN modules, allowing users to access VoIP service whenever they are within the coverage of WLAN service area. One of the greatest challenges for such dual-mode (say GSM and WiFi) handsets to support ubiquitous communication is the ability to maintain session continuity so a phone call established through one mode can be transferred to the other mode without user intervention. While related work has investigated the problem of supporting vertical handoffs for data communications across heterogeneous wireless data networks (e.g. GPRS and WiFi), these approaches cannot be directly used for vertical handoffs across heterogeneous telephony systems that involve both circuit-switched and packet-switched systems. In this paper, we investigate the problem of supporting vertical handoffs for voice communications across circuit-switched and packet-switched telephony systems on dual-mode mobile devices. We first contend that an end-to-end solution has advantages over infrastructure-based solutions due to the unique characteristics of the problem considered. We then propose an end-to-end approach that builds atop existing cellular network and VoIP infrastructure without introducing new entities for supporting vertical handoffs on dual-mode mobile devices. The proposed approach is based on the Session Initiation Protocol (SIP) and requires modifications only on end devices. We conduct testbed experiments using a GSM–WiFi dual-mode PDA and a SIP soft phone, and evaluate the quality of speech on the dual-mode PDA when the call is migrated from WiFi to GSM. Evaluation results show that the proposed approach allows soft handoffs and is a promising solution for seamless vertical handoffs on dual-mode mobile devices.

The Complementary Use of 3G WCDMA and GSM/GPRS Cellular Radio Networks

The traffic performance of integrated 3G wide-band code division multiple access (WCDMA) and GSM/GPRS network is evaluated. This type of network links two cellular radio systems which have different set of frequency bands and the same coverage size. The base station of 3G WCDMA is installed on an existing GSM/GPRS site. Dual-mode mobile terminals use handoff to establish calls on the better system. The soft handoff or inter-frequency hard handoff occurs when mobile terminals of 3G WCDMA or GSM/GPRS move between two adjacent cells, respectively. The inter-system hard handoffs are used between 3G WCDMA and GSM/GPRS systems. The data rate conversions between different systems, soft handoff region size, multiple data rate multimedia services, and the effect of the mobile terminal mobility on the user mean dwell time in each system are considered in the study. The simulation results demonstrate that a great traffic performance improvement on the complementary use of 3G WCDMA and GSM/GPRS cellular radio networks compared with the use of GSM/GPRS cellular radio networks. When high-data rate transmission is chosen for low-mobility subscribers, both the handoff failure probability, and carried traffic rates increase with the new call generation rate. However, both rates decrease conversely with the increasing new call generation rate as soon as the new call generation rate exceeds a critical value. This causes the integrated networks saturation. The higher mean speed for the mobile terminals produces lower new call blocking probabilities and total carried traffic. The new call blocking probabilities and total carried traffic increase with the size of the soft handoff region.

PIANO: A power saving strategy for cellular/VoWLAN dual-mode mobiles

The integration of cellular and VoIP over WLAN (VoWLAN) systems recently has attracted considerable interest from both academia and industry. A cellular/VoWLAN dual-mode system enables users to access a low-cost VoIP service in a WLAN hotspot and switch to a wide-area cellular system without WLANs. Unfortunately, cellular/VoWLAN dual-mode mobiles suffer the power consumption problem that becomes one of the major concerns for commercial deployment of the dual-mode service. In this study, we present a novel power saving mechanism, called PIANO (paging via another radio), for the integration of heterogeneous wireless networks, and further apply the proposed methods to implement a cellular/VoWLAN dual-mode system. Based on the proposed mechanisms, a dual-mode mobile can completely switch off its WLAN interface, only leaving the cellular interface awake to listen to paging messages. When a mobile receives a paging message from its cellular interface, it wakes up the WLAN interface and responds to connection requests via WLAN networks. Therefore, a dual-mode mobile reduces the power consumption by turning off the WLAN interface during idle, and can also receive VoWLAN services. Measurement results based on the prototype system demonstrate that the proposed methods significantly extend the standby hours of a dual-mode mobile.

Effective VoIP call routing in WLAN and cellular integration

In cellular-WLAN integration, a dual-mode mobile station (MS) typically disables the WLAN module for power saving. A major problem is that for an incoming VoIP call (or data session), the MS will not be able to receive this call from the WLAN. It turns out that the call is directed to the cellular network. This letter proposes a simple push solution where an MS can accurately detect a VoIP call from paging signaling of the cellular network. Then the WLAN module of the MS is turned on and the VoIP call is connected to the MS through the relatively inexpensive WLAN.

Two-hop-relay architecture for next-generation WWAN/WLAN integration

Next-generation wireless systems (4G and beyond) are envisioned to provide ubiquitous high-speed access over heterogeneous radio technologies. The integration of cellular WWANs and WLANs has drawn considerable attention from the research and commercial communities (e.g., 3G+802.11). Emerging dualmode mobile terminals could provide flexibility and system performance enhancement by providing seamless roaming between WWANs and WLANs. In this article we propose a novel integrated WWAN/WLAN two-hop-relay architecture that both enhances the system capacity of existing WWAN systems and extends the system coverage of WLAN terminals. The proposed two-hop-relay architecture can be considered as a system-level macro diversity technique that utilizes temporal channel quality variation to achieve increased system capacity. Significant capacity gain is achieved with the proposed twohop-relay architecture in both a fixed-rate uplink CDMA system and a variable data rate downlink HDR-like system.