• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.1
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• pp.147-161
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• 2012

In recent years, machine-to-machine (M2M) communications are under rapid development to meet the fast-increasing requirements of multi-type wireless services and applications. In order to satisfy M2M communications requirements, heterogeneous networks convergence appears in many areas, i.e., mobile cellular networks (MCNs) and wireless sensor networks (WSNs) are evolving from heterogeneous to converged. In this paper, we introduce the system architecture and application requirement for converged MCN and WSN, where mobile terminals in MCN are acting as both sensor nodes and gateways for WSN. And then, we discuss the joint optimization of converged networks for M2M communications. Finally, we discuss the technical challenges in the converged process of MCN and WSN.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9A
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• pp.767-775
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• 2011

In this paper, we propose a new multi-input multi-output (MIMO) channel modeling method for mobile-to-mobile (M2M) communications based on IEEE 802.16n. To reflect the mobilities at the transmitter and the receiver, we propose a new channel model by invoking the geometrical two-ring scattering model and modifying the conventional IEEE 802.16m fixed-to-mobile (F2M) channel model considering M2M communication environments. Through computer simulations, we analyze the statistical properties of proposed channel model in terms of the time correlation and the spatial correlation. Finally, the performance of the system using the proposed M2M channel model is compared with that using the conventional 802.16m F2M channel model by link level simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.325-328
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• 2013

Recently, the national carrier of the next-generation growth engine of M2M (machine to Machine) is attracting attention. Therefore, its uses and utilization of the various disciplines is getting wider, and the increasing number of terminals to be used compared to the existing communication of the information that is sent in every object may have increased. Each data transfer from the bulk terminal to a mobile network, if the traffic situation reaches this limit does not facilitate the processing of M2M communication services, this situation can occur. This study measures the mobile networks will be used in M2M communications when it reaches the breaking point for the smooth processing of M2M services are presented. Things grows increasingly smaller the further development of M2M technology, the explosion in mobile communication network, the data traffic will reach the limitations of these methods will be used in determining the ranking of the M2M communication services should be treated as a priority, to beM2M services to mobile networks will help to facilitate.

• International Journal of Computer Science & Network Security
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• v.23 no.10
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• pp.73-80
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• 2023

The recent growth in the use of mobile devices has contributed to increased computing and storage requirements. Cloud computing has been used over the past decade to cater to computational and storage needs over the internet. However, the use of various mobile applications like Augmented Reality (AR), M2M Communications, V2X Communications, and the Internet of Things (IoT) led to the emergence of mobile cloud computing (MCC). All data from mobile devices is offloaded and computed on the cloud, removing all limitations incorporated with mobile devices. However, delays induced by the location of data centers led to the birth of edge computing technologies. In this paper, we discuss one of the edge computing technologies, i.e., cloudlet. Cloudlet brings the cloud close to the end-user leading to reduced delay and response time. An algorithm is proposed for scheduling tasks on cloudlet by considering VM's load. Simulation results indicate that the proposed algorithm provides 12% and 29% improvement over EMACS and QRR while balancing the load.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.481-484
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• 2013

Many people today are interested in Machine to Machine (M2M) as the new-generation growth engine of mobile communications service providers in Korea. Its use and application are broadening to various areas and the number of devices used for it is increasing to increase the number of information transmitted for each object. When the traffic reaches its limit while each set of data is transmitted from the devices divided into each group through the mobile network, M2M communications service might not be processed smoothly. This study used the Knapsack Problem algorithm to create a virtual simulator for a smooth M2M service when the mobile network used for the M2M communications reaches its limit. The virtual simulator applies smooth processing of services from the M2M communications that should be processed first to other subsequent services when data comes to each group of devices. As the M2M technology develops to make many objects more compact in size, it would help with smoother processing of M2M services for the mobile network with fast-increasing traffic.

• Proceedings of the Optical Society of Korea Conference
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• 2004.07a
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• pp.28-29
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• 2004

Optical wireless mobile communications have the potential to provide wide bandwidth and security . We have proposed and designed the 2-dimensional tracking optical receiver systems for optical wireless mobile communication. The receiver system consist of 4${\times}$4 photodiode array can receive optical signal from the transmitter. The room size is 5${\times}$5m$^2$ and the room height is 3m.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.9
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• pp.1573-1595
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• 2011

In this paper, the outage performance of multiuser multiple-input single-output (MISO) systems exploiting joint spatial and multiuser diversities is investigated for Rayleigh fading channels with outdated feedback. First, we derive closed-form exact outage probabilities for the joint diversity schemes that combine user scheduling with different spatial diversity techniques, including: 1) transmit maximum-ratio combining (TMRC); 2) transmit antenna selection (TAS); and 3) orthogonal space-time block coding (OSTBC). Then the asymptotic outage probabilities are analyzed to gain more insights into the effect of feedback delay. It is observed that with outdated feedback, the asymptotic diversity order of the multiuser OSTBC (M-OSTBC) scheme is equal to the number of transmit antennas at the base station, while that of the multiuser TMRC (M-TMRC) and the multiuser TAS (M-TAS) schemes reduce to one. Further by comparing the asymptotic outage probabilities, it is found that the M-TMRC scheme outperforms the M-TAS scheme, and the M-OSTBC scheme can perform best in the outage regime of practical interest when the feedback delay is large. Theoretical analysis is verified by simulation results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2661-2667
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• 2013

Recently, at Home and abroad, Internet of Things era things(Thing) is participating as a subject of communication in human communication paradigm of existing (lot/M2M) is in full swing. Automobile, refrigerator, bicycle, until shoes, and communication functions generation of information is installed and has created a fusion of new service IT infrastructure. Its use and application are broadening to various areas and the number of devices used for it is increasing to increase the number of information transmitted for each object. When the traffic reaches its limit while each set of data is transmitted from the devices divided into each group through the mobile network, M2M communications service might not be processed smoothly. This study used the Knapsack Problem algorithm to create a virtual simulator for a smooth M2M service when the mobile network used for the M2M communications reaches its limit. The virtual simulator applies smooth processing of services from the M2M communications that should be processed first to other subsequent services when data comes to each group of devices. As the M2M technology develops to make many objects more compact in size, it would help with smoother processing of M2M services for the mobile network with fast-increasing traffic.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.3
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• pp.51-57
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• 2010

A dual-mode direct conversion receiver is developed in $0.13\;{\mu}m$ RF CMOS process for IEEE 802.11n based wireless LAN and IEEE 802.16e based mobile WiMAX application. The RF receiver covers the frequency band between 2.3 and 2.7 GHz. Three-step gain control is realized in LNA by using current steering technique. Current bleeding technique is applied to the down-conversion mixer in order to lower the flicker noise. A frequency divide-by-2 circuit is included in the receiver for LO I/Q differential signal generation. The receiver consumes 56 mA at 1.4 V supply voltage including all LO buffers. Measured results show a power gain of 32 dB, a noise figure of 4.8 dB, a output $P_{1dB}$ of +6 dBm over the entire band.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.2
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• pp.20-26
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• 2013

We propose PHY Frame Structure for M2M direct communications in licensed frequency band. Especially, the proposed PHY Frame Structure coexists in the same licensed frequency band as currently operating cellular systems. Recently, Machine to Machine (M2M) service markets, including SmartGrid, Mobile Health, and Smart Car, are being rapidly expanded. Supporting M2M services in a specific case can waste Radio Resource in cellular systems. For example, when two M2M terminals communicating to each other are closely located, direct communication is radio resource efficient. In this paper, we set the requirement of maintaining the existing PHY frame structure in cellular systems to meet the backward compatibility. Based on this backward compatibility requirement, PHY frame structure for M2M direct communications is developed while satisfying coexistence with current operating cellular system. The proposed PHY frame structure meets backward compatibility. Accordingly, it is expected that the proposed M2M frame structure is useful for its frequency resource efficiency.