• The KIPS Transactions:PartC
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• v.12C no.6 s.102
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• pp.799-808
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• 2005

This paper proposes low latency handover procedure for seamless connectivity and QoS support between wired (e.g. Ethernet) and wireless (e.g. WLAN, WiBro(802.16-compatible), CDMA) networks by the mobile-assisted and server-initiated handover strategy. It is assumed that the server decides the best target network considering network status and user preferences. In this algorithm a mobile terminal associates with the wireless link decided at the server In advance and receives CoA as well. When handover occurs without the prediction in wired networks, the server performs fast binding update using physical handover trigger through the MIH(media independent handover) function. As a result, a mobile terminal does not need to perform L2 and L3 handover during handover so that this procedure decreases handover latency and loss.

• Information and Communications Magazine
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• v.19 no.7
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• pp.72-77
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• 2002

This paper introduces the Future Technologies for Universal Radio Environment (FUTURE), which is China's wireless communications research project oriented to beyond 3G systems. The features and basic requirements of the FUTURE project are described, and the system structure, which is based on IPv6 core network, is proposed. The key techniques for FUTURE project are also addressed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.6
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• pp.1689-1706
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• 2012

The preservation of temporal dependencies among a group of processes that exchange continuous media at runtime is a key issue for emerging mobile distributed systems (MDS), such as monitoring of biosignals and interactive multiuser games. Although several works are oriented to satisfy temporal dependencies, most of them are not suitable for MDSs. In general, an MDS is characterized by the absence of global references (e.g. shared memory and wall clock), host mobility, limited processing and storage capabilities in mobile hosts, and limited bandwidth on wireless communication channels. This paper proposes an asymmetric synchronization protocol to be used at runtime in an MDS without using a common reference. One main aspect of our synchronization protocol is that it translates temporal constraints to causal dependencies of the continuous media data as seen by the mobile hosts. We simulate the protocol by considering a cellular network environment and by using MPEG-4 encoders. The simulation results show that our protocol is effective in reducing the synchronization error. In addition, the protocol is efficient in terms of processing and storage costs at the mobile devices, as well as in the overhead attached per message across the wired and wireless channels.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.49 no.1
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• pp.46-53
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• 2012

The WBAN technology means a short distance wireless network which provides each device's interactive communication by connecting devices inside and outside of body located within 3 meters. Standardization on the physical layer, data link layer, network layer and application layer is in progress by IEEE 802.15.6 TG BAN. It is necessary to develop the WBAN core technology that sensor node device, WBAN middleware and WBAN application service for WBAN environment. In this paper we designed the medical message structure and implemented medical application for purpose of vital information reliability. The message structure was proposed for WBAN environment and application can be check biometric information from BN on smart device through WBAN gateway.

• International Journal of Computer Science & Network Security
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• v.24 no.6
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• pp.23-32
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• 2024

Mobile Ad hoc Network is a network of multiple wireless nodes which communicate and exchange information together without any fixed and centralized infrastructure. The core objective for the development of MANET is to provide movability, portability and extensibility. Due to infrastructure less network topology of the network changes frequently this causes many challenges for designing routing algorithms. Many routing protocols for MANET have been suggested for last few years and research is still going on. In this paper we review three main routing protocols namely Proactive, Reactive and Hybrid, performance comparison of Proactive such as DSDV, Reactive as AODV, DSR, TORA and Hybrid as ZRP in different network scenarios including dynamic network size, changing number of nodes, changing movability of nodes, in high movability and denser network and low movability and low traffic. This paper analyzes these scenarios on the performance evaluation metrics e.g. Throughput, Packet Delivery Ratio (PDR), Normalized Routing Load(NRL) and End To-End delay(ETE).This paper also reviews various network layer security attacks challenge by routing protocols, detection mechanism proposes to detect these attacks and compare performance of these attacks on evaluation metrics such as Routing Overhead, Transmission Delay and packet drop rates.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.222-230
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• 2005

This article presents a field evaluation of an IP-based architecture for heterogeneous environments that has been developed under the aegis of the Moby Dick project, covering UMTS-like (universal mobile telecommunications system) TD-CDMA (time division-code division multiple access) wireless access technology, wireless and wired LANs. The architecture treats all transmission capabilities as basic physical and data-link layers, and replaces all higher-level tasks by IP-based strategies. The Moby Dick architecture incorporates mobile IPv6, fast handovers, AAA-control (authentication, authorisation, accounting), charging and quality of service (QoS) in an integrated framework. The architecture further allows for optimised control on the radio link layer resources. It has been implemented and tested by expert users, and evaluated by real users on field trials with multiple services available.

• Electronics and Telecommunications Trends
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• v.39 no.2
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• pp.43-53
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• 2024

The media environment is rapidly evolving to be tailored to viewers using personal mobile devices in accordance with technological evolution and changes in social structures. Broadcast media technology is also advancing to enable new services, including data casting, in various reception environments beyond the existing fixed environment and one-way audio/video content services. In addition, technologies to increase the transmission capacity to accommodate next-generation large-capacity media content as well as communication network utilization and convergence technologies are being developed to facilitate interactive services and expand the broadcasting coverage. We discuss the current status and future prospects in broadcasting technology for terrestrial and mobile communication systems and analyze broadcasting technology elements for upcoming media environments relying on generative artificial intelligence.

• Electronics and Telecommunications Trends
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• v.39 no.1
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• pp.36-47
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• 2024

Virtualization technology supports the execution of software unrelated to the hardware environment through the decoupling of software and hardware. Additionally, it enables network slicing, allowing one physical device to be divided and used by a function or service by supporting sharing with isolation. Virtualization enables flexible platform use, allowing a variety of services to be launched without changes or additions to the hardware platform. We describe virtualization technology trends in satellite/mobile communication systems. Basic concepts and technical definitions are included, and the current status of research and development by domestic and foreign organizations, including the Electronics and Telecommunications Research Institute, is analyzed. Finally, future prospects and implications are discussed.

• Journal of Internet Computing and Services
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• v.6 no.5
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• pp.123-132
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• 2005

By complementary integration of WLAN and UMTS, a Beyond third Generation(B3G) mobile network can be constructed to establish the fastest global roaming environments, There are 2 types of B3G networks: loosely-coupled and tightly-coupled, A tightly-coupled network demands lots of investment and considerable amount of time to construct. On the other hand a loosely-coupled network is more scalable and easier to implement than a tightly-coupled one, But it has critical drawbacks of packet loss and blocking of services due to handover delay, To alleviate these drawbacks this thesis proposes a vertical handover procedure between WLAN and UMTS, which is based on MAP of HMIPv6, Performance of the proposal is evaluated in terms of blocking probabilities, The proposed procedure based on HMIPv6 shows better performance than those based on MIP.

• International Journal of Computer Science & Network Security
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• v.23 no.9
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• pp.8-16
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• 2023

In Japan, high-speed ground transportation service using linear motors at speeds of 500 km/h is scheduled to begin in 2027. To accommodate 5G services in trains, a subcarrier spacing frequency of 30 kHz will be used instead of the typical 15 kHz subcarrier spacing to mitigate Doppler effects in such high-speed transport. Furthermore, to increase the cell size of the 5G mobile system, multiple base station antennas will transmit identical downlink (DL) signals to form an expanded cell size along the train rails. In this situation, the forward and backward antenna signals are Doppler-shifted in opposite directions, respectively, so the receiver in the train may suffer from estimating the exact Channel Transfer Function (CTF) for demodulation. In a previously published paper, we proposed a channel estimator based on Delay and Doppler Profiler (DDP) in a 5G SISO (Single Input Single Output) environment and successfully implemented it in a signal processing simulation system. In this paper, we extend it to 2×2 MIMO (Multiple Input Multiple Output) with spatial multiplexing environment and confirm that the delay and DDP based channel estimator is also effective in 2×2 MIMO environment. Its simulation performance is compared with that of a conventional time-domain linear interpolation estimator. The simulation results show that in a 2×2 MIMO environment, the conventional channel estimator can barely achieve QPSK modulation at speeds below 100 km/h and has poor CNR performance versus SISO. The performance degradation of CNR against DDP SISO is only 6dB to 7dB. And even under severe channel conditions such as 500km/h and 8-path inverse Doppler shift environment, the error rate can be reduced by combining the error with LDPC to reduce the error rate and improve the performance in 2×2 MIMO. QPSK modulation scheme in 2×2 MIMO can be used under severe channel conditions such as 500 km/h and 8-path inverse Doppler shift environment.