• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.7A
• /
• pp.620-627
• /
• 2005

We develop an adaptive hot-spot operating scheme(AHOS) to mitigate the negative effects from the nonuniform distribution of user location and the variation in the mixture of QoS requirements in OFDMA downlink systems. The base station in a macrocell can control the operation of picocells within the cell, and turns on or off according to the changes in the estimated user outage probability and the AHOS gain parameter. With the computer simulation, the AHOS has been proved to maximize the system throughput while maintaining the QoS outage probability very low under various system scenarios.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.10
• /
• pp.1-7
• /
• 2007

In WCDMA systems the down-link power allocation directly affects the cell deployment capacity, coverage, and system performances. Down-link power should be controlled at minimum but still satisfy the mobile stations' required signal to noise ratio. This paper mathematically proves that the down-link power allocation depends on the number of active mobile stations accessed to the base station. Therefore this paper proposes the dynamic down-link power allocation should be implemented to the WCDMA cellular systems.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.5 no.5
• /
• pp.916-922
• /
• 2001

A medium access control protocol is proposed for integrated voice and data services in the packet CDMA network with a small coverage. Uplink channels are composed of time slots and multiple spreading codes for each slot. This protocol gives higher access priority to the delay-sensitive voice traffic than to the data traffic. During a talkspurt, voice terminals reserve a spreading code to transmit multiple voice packets. On the other hand, whenever generating a data packet, data terminals transmit a packet based on the status Information of spreading codes in the current slot, which is received from base station. In this protocol, voice packet does not come into collision with data packet. Therefore, this protocol can increase the maximum number of voice terminals.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.5
• /
• pp.520-530
• /
• 2016

Since FDD massive MIMO (multiple-input multiple-output) system deploys hundreds of transmit antennas at base station (BS) compared to conventional MIMO system, the overhead of transmitting channel state information reference signal (CSI-RS) increases proportionally to the number of transmit-antennas. To overcome these disadvantages, we proposed beamforming based CSI-RS transmission technique for FDD massive MIMO system which transmit CSI-RS by limited amount of downlink resources.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.2A
• /
• pp.140-146
• /
• 2004

In this paper we proposed the reducing method of feedback information for transmitting of adaptable data rate in multi-user OFDMA/FDD systems. In order to transmit downlink channel information to Base-Station(BS) through the limited uplink control channel, the proposed algorithm exploits the channel variation level which describes the similarity among the adjacent clusters and uses just one modulation and coding scheme(MCS) level representing channel information of all clusters'. We investigated the performance in single cell environment. It has a similar overhead for feedback information with conventional algorithm and has better performance in that bandwidth efficiency and outage probability than the conventional algorithms.

• Korean Journal of Clinical Laboratory Science
• /
• v.44 no.4
• /
• pp.199-204
• /
• 2012

The purpose of this study is to examine the population density of the mosquito species, and to provide the basic data related to vector mosquitoes to manage the possible epidemic diseases. During a 4-year investigation (2001, 2002, 2004, and 2006), we collected the specimens of the mosquitoes at pier no. 1, 3 and 5 of Busan port with light traps from sunset until the next day morning from April to October each year. Through the research, we collected 5,985 mosquito specimens in total and found 7 mosquito species belonging to 3 genera. A total of 1,575, 1,473, 1,478 and 1,459 mosquito specimens were collected in 2001, 2002, 2004 and 2006, respectively. Among them, 5,568 (93.0%) specimens were Culex pipiens pallens, the West Nile virus infection vector, which showed the highest density among the specimens. The population densities of the other species were: 295(4.9%) Culex tritaeniorhynchus, 94(1.5%) Aedes togoi, 12(0.3%) Aedes albopictus, 10(0.2%) Anopheles sinensis, 4(0.1%) Aedes vexans nipponii, 2(0.1%) Culex inatomii. The monthly abundance of mosquitoes from July through September showed the highest values. Although it was a general mosquito monitoring study, this study could provide a base for securing the statistical data on spreading epidemic diseases by people infected outside Korea.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.8
• /
• pp.3054-3067
• /
• 2015

The phenomena of higher channel cross polarization discrimination (XPD) is mainly observed for future wireless technologies such as small cell network and massive multiple-input multiple-output (MIMO) system. Therefore, utilization of high XPD is very important and space-polarization division multiple access (SPDMA) with dual-polarized MIMO system could be a suitable solution to high-speed transmission in high XPD environment as well as reduction of array size at base station (BS). By SPDMA with dual-polarized MIMO system, two parallel data signals can be transmitted by both vertically and horizontally polarized antennas to serve different mobile stations (MSs) simultaneously compare to conventional space division multiple access (SDMA) with single-polarized MIMO system. This paper analyzes the performance of SPDMA for maximum ratio transmission (MRT) in time division duplexing (TDD) system by proposed dual-polarized MIMO spatial channel model (SCM) compare to conventional SDMA. Simulation results indicate that how SPDMA utilizes the high XPD as the number of MS increases and SPDMA performs very close to conventional SDMA for same number of antenna elements but half size of the array at BS.

• Journal of information and communication convergence engineering
• /
• v.8 no.4
• /
• pp.399-404
• /
• 2010

We propose a seamless IPTV transport technology of mobile device. This technology uses multiple interfaces of wireless communication on mobile device. This proposal for transportation of mobile IPTV contents is more mobile and adaptable than other wireless technologies that are currently being used. Algorithm of proposed technology is as follow. When the signal strength of the connected wireless network interface of mobile device is getting lower than specified level, another wireless network interface is connected to continue downloading the IPTV contents in advance. Another connection is maintained until the signal strength of the first connected interface is stable or the interface is connected to another base station (or AP) that have good signal strength. For more seamless services, we consider classifying the packets of mobile IPTV and using dynamic content quality select techniques. Dynamic content quality selection is based on notifying transfer rate to the content delivery network (CDN) server. The proposed technology is expected to use efficiently with both mobile IPTV and the transportation of mobile P2P/P4P.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2015.10a
• /
• pp.579-581
• /
• 2015

Air threat such as aircrafts or missiles were incresed rapidly after World War II, warships were relatively vulnerable to air threat. Therefore U.S. and allies developed various Tactical Data Link(TDL) to defend warships from air threat. Target information can be managed and shared with other station by real or near-real time due to TDL. TDL is base system to manage battlefield and to carry out C2(Command and Control) effectively and rapidly. In this paper, the type, current operating status and characteristic of TDL is surveyed and newest technical trend such as LINK-K is described.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2016.05a
• /
• pp.591-593
• /
• 2016

Device-to-device (D2D) communications underlaid cellular infrastructure is an competitive local area services technology to promote spectrum usage for next generation cellular networks. These potential can only be tap through efficient interference coordination. Previous works only concentrated on interference from D2D pairs whiles interference from CUs to D2D pairs were neglected. This work focus on solving uplink interference problem emanating from multiple CUs sharing its resource with multiple D2D pairs. The base station (BS) acting as a supervisor selfishly institute a pricing scheme to manage the interference it experience from D2D pairs based on its Quality of service (QoS) requirement. D2D pairs following the supervisor make power allocation decisions considering the price from the BS in a non-cooperative game fashion. In order for the D2D pairs to also meet their QoS requirement, they suggest a price to the BS called discount price which reflects the interference they receive from the CUs. Finally, we analyze the proposed approach.