• Journal of Korea Multimedia Society
• /
• v.6 no.4
• /
• pp.601-609
• /
• 2003

In wireless mobile networks, the service area is partitioned into several registration areas (RAs). Every RA is associated with a mobility database called Visitor Location Register (VLR). The VLR is used to achieve the location management of the mobile terminals. When a mobile terminal enters a new RA, the VLR stores the current location information of the mobile terminal before serving any mobile services. At that time, if the VLR is full, the registration procedure fails, and the system can not deliver services to the mobile user under the existing cellular technology To resolve this problem, we propose a VLR overflow control scheme considering mobility of mobile users to accomodate incoming users during VLR overflow. The performance of the proposed scheme is evaluated by an analytic model in terms of costs for the location search and the location update, and compared with those of the overflow control scheme proposed by Lin[1].

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.247-248
• /
• 2008

A recent dynamic increase in demand for wireless multimedia services has greatly accelerated the research on dynamic channel adaptation of high quality video applications. In this paper, we explore a theoretical approach to cross-layer optimization between multimedia and wireless networks by means of a quality criterion termed "visual throughput" for downlink video transmission using a layered coding algorithm. We obtain the optimal loading ratio of orthogonal frequency division multiple access (OFDMA) subcarriers through an optimization problem balancing the trade-off relationship between inter-cell interference (ICI) and channel throughput. In the simulation, we show that the visual throughput gain at the cell boundary is increased by about 32%.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.3B
• /
• pp.232-238
• /
• 2006

We propose a novel call admission control scheme which improves the handoff drop and the new call block probabilities of high priority services, minimizing the negative impact on low priority services, in multimedia service cellular networks. This paper proposes three schemes to solve this problem; the packing scheme in which available channels of a cell distributed to each frequency channel are concentrated on one frequency channel and a high transmission rate service is assigned to the frequency channel; the queuing scheme in which the queue is used for high transmission rate calls; and the power reallocation scheme in which the power assigned to calls under service is temporarily reduced and a high transmission rate service is allowed. The simulation results revealed that our scheme improved the drop and the block probabilities of the high priority services compared with the conventional scheme.

• Proceedings of the Korea Contents Association Conference
• /
• 2006.11a
• /
• pp.729-733
• /
• 2006

Short message service (SMS) is a Popular mobile data service in cellular networks. One SMS message can carry 50 Korean alphabets. Cellular operators standard and develop multimedia message service (MMS) based on P2P as color phones having multimedia solutions such as MIDI, MP3, JPG, PNG, and MPEG have been developed. MMS can be a key cash flow in the non-voice mobile revenue together with SMS. Copyrights protection of contents in a MMS message can be issued as MMS can be the popular P2P service such as MMS. In this paper, we propose MMS DRM system to protect copyrights of contents in MMS with the minimum change of MMS system. The proposed MMS DRM system protect copyrights of contents using DRM Packager, DRM Server, and DRM Agent and support various use cases to activates MMS in mobile networks.

• International Journal of Contents
• /
• v.1 no.2
• /
• pp.31-34
• /
• 2005

The new realtime applications like multimedia and realtime services in a wireless network will be dramatically increased. However, many realtime services of mobile hosts in a cell cannot be continued because of insufficiency of useful channels. Conventional channel assignment approaches didn't properly consider the problem to serve realtime applications in a cell. This paper proposes a new realtime channel assignment algorithm based on time constraint analysis of channel requests. The proposed algorithm dynamically borrows available channels from neighboring cells. It also supports a smooth handoff which continuously serves realtime applications of the mobile hosts.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2003.05a
• /
• pp.441-447
• /
• 2003

Recently there is a growing Interest In mobile cellula r network providing multimedia service. However, the link bandwidth of mobile cellular network is not sufficient enough to provide satisfactory services to use rs. To overcome this problem, an adaptive framework has been proposed in this study, we propose a new method of estimating DPR(degradation period ratio) in an adaptive multimedia network where the bandwidth of ongoing call can be dynamically adjusted during its lifetime. DPR is a QoS(quality of service) parameter which represents the ratio of allocated bandwidth below a pre-defined target to the whole service time of a call. We improve estimation method of DPR using DTMC(discrete time Markov chain) model. We also calculate mean degradation period and degradation probability more precisely than in existing studies. Under Threshold CAC(call admission control) algorithm, we present analytically how to guarantee QoS to users and illustrate the method by numerical examples. The proposed method is expected to be used as one of CAC schemes in guaranteeing predefined QoS level of DPR

• Journal of information and communication convergence engineering
• /
• v.1 no.4
• /
• pp.183-188
• /
• 2003

The $4^{th}$ generation mobile communications, through several radio access networks such as WLAN, Bluetooth, UMTS, GPRS, CDMA 1X, and IMT-2000 in the same area offering different type of coverage, will support interactive multimedia services in additions to wider bandwidths, higher bit rates, and service portability. Regardless of various radio access networks, they will also support robust security mechanisms, as well as seamless mobility and common authentication. In this paper, we give an overview of WLAN security and examine its security problems. We also explain the enhanced security schemes, such as port-based authentication, EAP, and IEEE 802.1X. For secure wireless communications, several possible security solutions are offered and evaluated in various respects to improve WLAN security. This paper will make a contribution to provide more secure wireless communications to cellular operators embracing WLAN technology as a means to generate new revenues based on data services.

• Journal of the Korea Society of Computer and Information
• /
• v.21 no.1
• /
• pp.59-64
• /
• 2016

This paper suggests heuristic algorithm with O(mn) polynomial time complexity using Excel for partially survivable networks optimization problem of cellular telecommunication systems with m cells and n hubs. This problem only can be get the solution using linear programming or LINGO software package. The proposed algorithm connects the cell to hubs in ring network with minimum cost as the connection diversity of each cell. If the traffic of ring network (T) is T>2K for ring capacity (K), we adjust the maximum cost hub to MTSO that has a ascending order of (D/DC)/${\Delta}^+$ cell with each cell traffic demand (D) and ${\Delta}^+$=(MTSO cost-maximum cost hub) than we get the $T{\leq}2K$. Finally, we adjust MTSO to the removed maximum cost hub for the cell with 2K-$T{\geq}$(D/DC) and $_{max}{\Delta}^-$. While we using like this simple method, the proposed algorithm can be get the same optimal solution for experimental data as linear programing and LINGO software package.

• Proceedings of the Korean Information Science Society Conference
• /
• 2006.06d
• /
• pp.217-219
• /
• 2006

4G mobile networks are expected to support various multimedia services over IP networks and also satisfy high spectral efficiency requirement. In cellular systems including 4G networks, hotspot cells can occur when available wireless resources at some location are not enough to sustain the needs of users. The hotspot cell can potentially lead to blocked and dropped calls, which can deteriorate the service quality for users. In a 4G mobile network, a band of users enjoying multimedia services can move around, which may generate heavy flows of traffic load. This situation can generate the hotspot cell which has a short life span of only a few minutes. In this paper, we propose a handover-based scheme which can effectively manage hotspot cells in 4G mobile networks. With the scheme, the current serving cell can recognize the load status of the target cell in advance before handover execution. Adaptive handover time control according to the amount of traffic load of cells can effectively and flexibly manage the hotspot cell in the network. And, through our hotspot cell management scheme, acceptable service quality can be supported as users continuously maintain connections with the network. In the simulation results, we find that our scheme generates smaller number of hotspot cells and supports higher service quality than the compared schemes.

• Electronics and Telecommunications Trends
• /
• v.36 no.4
• /
• pp.72-80
• /
• 2021

Multimedia broadcast multicast services (MBMS) have evolved to accommodate broadcasting services in 3GPP standards. One long-standing approach is to comprise the multimedia broadcast multicast service single-frequency network based on the cellular networks of mobile operators, and another approach adds a broadcasting network to 3GPP standards. In this paper, we overview the MBMS architecture and key entities in MBMS services. In addition, the trends of MBMS are discussed in terms of technology and 3GPP standards, where MBMS functionality is described according to 3GPP releases. Finally, we discuss its capability through a comparison with ATSC 3.0, which is the latest terrestrial broadcasting standard, and then we present the current status and future perspectives of MBMS in 3GPP.