• Journal of Korea Multimedia Society
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• 제12권2호
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• pp.257-271
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• 2009

In this paper, we propose a protocol compression scheme for enhancing the performance of call processing of PTT(Push-to-Talk) which is one of the important services in IMS(IP Multimedia Subsystem), a next generation integrated wired/wireless packet communication network. To service the PTT on an IMS network, it should use the same call setup procedure as legacy Mobile and TRS(Trunked Radio System) networks and have a fast call setup time and enough communication bandwidth because a number of terminals should be able to exchange same data in real time. The proposed A+SigComp scheme reduces the initial call setup delay of SIP by about 10%, which is used by PTT service for call setup. In addition, the A+ROHC scheme is proposed to compress the header of RTP packets transferred during PTT voice transmission and, as a result, about 5% of increase in communication efficiency is observed.

• Journal of KIISE:Information Networking
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• 제32권5호
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• pp.551-560
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• 2005

To reduce the amount of the signaling messages occurred in movement, HMIPv6 has been introduced as the hierarchical mobility management architecture tor MIPv6 by regarding the locality of movements. When approaching the visited link, the authentication procedure should be done successfully prior to any motility support message exchanges. The AAA(Authentication, Authorization and Account) authentication service is applied gradually to the wireless LAN and Cellular networks. However, It may bring about the service latency for the sessions of requiring the real-time processing due to not providing the optimized signaling in local and frequent movements. In this paper, we propose the authentication architecture with 'delegation' scheme to reduce the amount of signaling message and latency to resume for local movements by integrating it with HMIPv6 architecture. We provide the integrated authentication model and analyze the performance and effectivity of our proposal and finally offer the analysis materials comparing to the exiting authentication scheme. It cuts down the cost to $33.6\%$ at average measurement.

• Journal of Communications and Networks
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• 제11권1호
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• pp.84-93
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• 2009

This paper focuses on message complexity performance analysis of mobile ad hoc network (MANET) address autoconfiguration protocols (AAPs) in reference to link errors generated by mobile wireless nodes. An enhancement was made using a proposed retransmission limit, S, to be computed for error recovery (based on the link error probability), to measure message complexity of AAPs in reference to the link error probability, $P_e$. The control procedures for the retransmission limit have been included for each of the AAPs. Retransmission limit control is critical for efficient energy consumption of MANET nodes operating on limited portable energy. O-notation has been applied to analyze the upper bound of the number of messages generated by a MANET group of nodes. The AAPs investigated in this paper are strong duplicate address detection (DAD), weak DAD with proactive routing protocol (WDP), weak DAD with on-demand routing protocol (WDO), and MANETConf. Each AAP reacts different to link errors, as each AAP has different operational procedures. The required number of broadcasting, unicasting, relaying, and received messages of the nodes participating in a single-node joining procedure is investigated to asymptotically calculate the message complexity of each AAP. Computer simulation was conducted and the results have been analyzed to verify the theoretical message complexity bounds derived. The message complexity of WDP was lowest, closely followed byWDO, based on the simulation results and analysis of the message complexity under nominal situations. The message complexity of MANETConf was higher than WDO, and strong DAD resulted to be most complex among the four AAPs.

• The Transactions of the Korea Information Processing Society
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• 제7권8S호
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• pp.2608-2619
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• 2000

This paper proposes the Handover Scheme for the mobile and describes the result of the performance analysis. In the conventional scheme of handover request, the withdrawal of terminal may occur because handover request is performed based on fixed signal level without considering network load and terminal mobility. The proposed scheme offers the minimization of withdrawal and handover blocking probability by means of the handover request of terminal based on the network load and terminal mobility. Conventional handover scheme has the sequential procedure that network performs resource check and path rerouting on the handover by MT(Mobile Terminal). Proposed handover scheme pre-processes the resource check before the handover request by predicting the handover request timo so that handover latency can be reduced. Moreover, path optimization is executed after the completion of handover in order to reduce handover latency. The rdduction of handover latency prevents the dropping of service by minimizing backward handover blocking. In summary, we propose the prediction of handover request time and decision method based on terminal, validating the performance of proposed scheme considering various cases of simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제32권11A호
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• pp.1173-1181
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• 2007

A number of routing algorithms have been studied for wireless mobile ad-hoc network. Among them, the AODV routing algorithm with on-demand method periodically transmits hello message and monitors link state during data transmission in order to maintain routing paths. When a path is disconnected, a node that senses it transmits a RERR packet to the transmitting node or transmits a RREQ locally so that the path could be repaired. With that, the control packet such as a RREQ is broadcast, which causes the consumption of bandwidth and incurs data latency. This paper proposes a LRRLBP algorithm that locally repairs a path by predicting link state before disconnecting the path based on the AODV routing protocol for solving such problems. Intensive simulations with the results using NS-2 simulator are shown for verifying the proposed protocol.

• Journal of the Institute of Electronics and Information Engineers
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• 제49권12호
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• pp.81-88
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• 2012

As the performance of the next-generation broadband wireless networks is dramatically enhanced, various services (i.e., education, Live video streaming, Live video conferencing, online games, etc.) have been provided to users through a smart mobile platform. Those services are usually provided by using the centralized communication server. However, since all multimedia traffic is exchanged through a communication server, it often has the scalability problem with regard to traffic management. Our main purpose is for group smart users to provide scalable live multimedia streaming service based on P2P network. To do this, we have designed an architecture of P2P-based service management for mobile group communication management and service management protocol. In order to verify the performance of the proposed scheme, we have mathematically analyzed the performance in terms of the average transmission delay and bandwid th utilization.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권3호
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• pp.1204-1227
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• 2020

The tradeoff between energy conservation and traffic balancing is a dilemma problem in Wireless Sensor Networks (WSNs). By analyzing the intrinsic relationship between cluster properties and long distance transmission energy consumption, we characterize three node sets of the cluster as a theoretical foundation to enhance high performance of WSNs, and propose optimal solutions by introducing rendezvous and Mobile Elements (MEs) to optimize energy consumption for prolonging the lifetime of WSNs. First, we exploit an approximate method based on the transmission distance from the different node to an ME to select suboptimal Rendezvous Point (RP) on the trajectory for ME to collect data. Then, we define data transmission routing sequence and model rendezvous planning for the cluster. In order to achieve optimization of energy consumption, we specifically apply the economic theory called Diminishing Marginal Utility Rule (DMUR) and create the utility function with regard to energy to develop an adaptive energy consumption optimization framework to achieve energy efficiency for data collection. At last, Rendezvous Transmission Algorithm (RTA) is proposed to better tradeoff between energy conservation and traffic balancing. Furthermore, via collaborations among multiple MEs, we design Two-Orbit Back-Propagation Algorithm (TOBPA) which concurrently handles load imbalance phenomenon to improve the efficiency of data collection. The simulation results show that our solutions can improve energy efficiency of the whole network and reduce the energy consumption of sensor nodes, which in turn prolong the lifetime of WSNs.

• Journal of the Institute of Convergence Signal Processing
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• 제15권2호
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• pp.64-69
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• 2014

Ultrasound system is one of the complex wireless signal processing systems that are widely used in the fields of modern industry such as medical diagnostics, underwater communications, and sensor-networks. Miniaturization of ultrasound system has been raging recently. In this paper, a hybrid LNA that is suitable for miniaturization and mobile diagnostic ultrasound system has been developed. The proposed LNA has low noise figure of less than 5dB, and the feedback resistor is designed to be electrically adjusted in order to attain the impedance-matching for various ultrasound transducers. It supports the whole ultrasound frequencies from 10KHz to 150MHz frequency band and also provides sleep modes. A gain from -18.8 to -29.5 dB is achieved by adjusting each transducer to fit the system character. Power consumption can be reduced up to 90% in similar performance as compared to the existing LNA.

• Journal of the Institute of Convergence Signal Processing
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• 제10권3호
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• pp.181-185
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• 2009

Recently, much attention to a self-organizing mobile ad-hoc network is escalating along with progressive deployment of wireless networks in our everyday life. Being readily deployable, the MANET (mobile ad hoc network) can find its applications to emergency medical service, customized calling service, group-based communications, and military purposes. In this paper we investigate a time slot exchange problem found in the time slot based MAC, that is designed for IEEE 802.11b interfaces composing a MANET. The paper provides a method to maintain the quality of voice call by providing a new time slot when the channel assigned for that time slot gets noisy with interferences induced from other nodes, which belong to the same and/or other subgroups. In order to assess the performance of the proposed algorithm, a set of simulations using the OPNET modeler has been performed assuming that the IEEE 802.11b interfaces are operating under a modified MAC, which is a time slot based reservation MAC implemented in the PCF part of the superframe. In a real-time voice call service over a MANET of a size 500 ${\times}$ 500 meter squares with the number of nodes up to 100, the simulation results are collected and analyzed with respect to the packet loss rate and packet delay. The results show us that the proposed time slot exchange protocol improves the quality of voice call over that of plain DCF.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제13권5호
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• pp.107-119
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• 2013

This paper reinforced security under the network evaluation of wire wireless integration of NEMO (NEwork MObility) supporting mobility and network-based PMIPv6 (Proxy Mobile IPv6). It also proposes $SK-L^2AS$ (Symmetric Key-Based Local-Lighted Authentication Scheme) based on simple key which reduces code calculation and authentication delay costs. Moreover, fast handover technique was also adopted to reduce handover delay time in PMIPv6 and X-FPMIPv6 (eXtension of Fast Handover for PMIPv6) was used to support global mobility. In addition, AX-FPMIPv6 (Authentication eXtension of Fast Handover for PMIPv6) is proposed which integrated $SK-L^2AS$ and X-FPMIPv6 by applying Piggybacks method to reduce the overhead of authentication and signaling. The AX-FPMIPv6 technique suggested in this paper shows that this technique is better than the existing schemes in authentication and handover delay according to the performance analysis.