• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6B
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• pp.650-662
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• 2011

The competition among companies in converged market of broadcasting and telecommunications has become severe. Companies in this market have vertically integrated critical resources by acquiring or strategically allying with relevant companies. However, the expansion of business territory accompanies financial, organizational, and technological risks. As such, it is important to identify critical success factors that highly affect the company's competency. This study is aimed at delivering strategic implications for firms playing in the converged market of broadcasting and telecommunications by drawing the priorities of competitive resources to acquire. To do this, we selected four teen specific core resources on CPNT (content- platform - network - terminal) value chain. Then, we conducted an Analytic Hierarchical Process (AHP) using data from experts in this industry. As a result, the priority for acquisition of competitive resources is presented as follows: broadcasting programs, implementation of TV application store, multi-platform, investment on wireless network, and diffusion of mobile devices. In addition, the result shows that the platform-centric vertical integration is the most promising strategy for competition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6B
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• pp.592-599
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• 2011

Proxy Mobile IPv6 (PMIPv6) is the network-based mobility management protocol that network supports the mobility of mobile node (MN) on behalf of the MN. In PMIPv6, a multi-homed MN can connect to the PMIPv6 domain by using only one interface even though it has multiple interfaces. It would be efficient when such a multi-homed MN connects to the PMIPv6 domain by using all of its interfaces. If such a multi-homed MN utilizes all of its interfaces, flow mobility can be provided that the MN handovers one or more flows from one interface to another without re-establishing session. In this paper, we propose the flow-based mobility management protocol by considering the intention of the user. The Router Advertisement (RA) message is used in order for the PMIPv6 domain to inform that the MN can utilize the flow mobility. The proposed mechanism is evaluated by analyzing signaling overhead and handover latency, and the numerical results show that the performance is affected by mobility speed of the MN and the failure probability of the wireless link.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.325-338
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• 2012

In this paper, a radio resource allocation scheme for a multi-hop relay transmission in cognitive radio (CR) system is proposed to support the employment of relay nodes in IEEE 802.22 standard for wireless regional area network (WRAN). An optimization problem is formulated to maximize the number of serving secondary users (SUs) under system constraints such as time-divided frame structure for multiplexing and a single resource-unit to every relay-hop. However, due to mathematical complexity, the optimization problem is solved with a sub-optimal manner instead, which takes three steps in the order of user selection, relay/path selection, and frequency selection. In the numerical analysis, this proposed solution is evaluated in terms of service rate denoting as the ratio of the number of serving SUs to the number of service-requesting SUs. Simulation results show the condition of adopting multi-hop relay and the optimum number of relaying hops by comparing with the performance of 1-hop system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.12
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• pp.1245-1255
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• 2012

There are various anti-jamming algorithms for the GNSS system which is vulnerable to jamming, and the methods using array antenna show the best performance. Among them, the DOA estimation algorithms to identify the location of the jammer is very important. However, in case of the rotorcraft, the wireless channel which amplitude and phase changes with time is generated by the rotation of the rotor and it affects the performance of existing anti-jamming algorithms. In this paper, we modeled the effect of the rotor in four scenarios according to the correlation of antennas and assured that the performance of DOA estimation algorithms are degraded and saturated regardless of JNR due to the rotor effect. When we use the averaging method to solve this problem, the performance is improved as increasing samples for estimating. And in case of using moving average method with averaging, it shows similar performance. In addition, it reduces the required memory and moderates the variation of DOA estimation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.12
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• pp.1211-1221
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• 2012

This paper describes separation distance to protect radiocommunication services from the interference of inductive systems using frequencies below 30 MHz for the co-existence between radiocommunication services and inductive systems. For the analysis, the interference scenario model is proposed between inductive system and radiocommunication services. Then the calculation method of protection distance is suggested by comparing the radiation power of inductive system with the allowable interference level of victim services, radiocommunication services, according to the applied propagation model. Also, the protection distance for protecting radiocommunication services in the 30 MHz below is calculated through the interference analysis from RFID(Radio Frequency IDentification) and PDP(Plasma Display Panel) TV based on the suggested method. The proposed calculation method was adopted as ITU-R recommendation in related with resolution 63 at ITU-R SG(Study Group) 1 meeting in June, 2012. It will be available to use for the protection of radiocommunication services from the interference of wireless power transfer system and power line telecommunication system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1B
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• pp.1-7
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• 2008

In group location management, when a transportation system(TS) with multiple mobile subscribers(MSs) changes location area(LA), location management is performed by group location registration by TS, instead of individual location registrations by MSs. In previous works, although it is assumed that LA in group location management is the same as that in individual location management, it is not appropriate to assume the same sized LAs since MSs in a TS have different characteristics from MSs which are not in a TS from the aspect of the speed and aggregate call arrival rates. Thus, in this paper, we propose an efficient location management scheme based on individual and group location managements with different sized LAs, and the performance of the proposed scheme is analyzed from the aspect of signaling cost at the wireless interface. Results reveal that the proposed scheme outperforms the conventional scheme by selecting an appropriate sized LA for group location management.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.577-584
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• 2010

In this paper, a cooperative MAC protocol that is reliable over bad wireless channel environments and thus can enhance the system performance much more is proposed. Its performance is evaluated with the computer simulation. The system throughput and average waiting delay are used as performance measures. According to numerical results, the proposed MAC protocol provides better system throughput by 24% than the traditional rDCF scheme. From the average waiting delay point of view, when the number of terminals is small, the proposed MAC protocol has the better performance in an average view-point than the rDCF scheme. However, when the number of terminals is large, the proposed MAC protocol provides a little worse performance than the rDCF scheme. That is because, when the number of terminals is large, the dominant factor affecting the system performance is channel contention procedure, which results in lots of collisions. However, if the queuing delays in the waiting buffers are included for calculating the average waiting delay, then the total system delay will be smaller than the rDCF scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2A
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• pp.132-138
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• 2009

Cognitive radio is considered as a promising solution to scarce spectrum problem. The primary object of cognitive radio is to increase spectral efficiency, while causing limited interference to primary users who are using the spectrum. Hence, an essential part of cognitive radio systems is spectrum sensing which determines whether a particular spectrum is occupied or not by a primary user at a particular time. However, sensing decision of each individual secondary user alone may not be reliable enough due to shadowing and multipath fading of wireless channels. The so called hidden terminal problem makes the problem even worse, possibly yielding undesired interference to the primary users. Recently, cooperative spectrum sensing is emerging as a remedy to these problems of individual sensing. Cooperative sensing allows a group of secondary users to share local sensing information to extract a global decision with high fidelity. In this paper, we investigate a cooperative spectrum sensing algorithm based on hard decisions of local sensing outcomes. Specifically, we propose an effective scheme for combining local decisions by introducing weighting factors that reflect reliability of the corresponding secondary user. Through computer simulations, the performance of the proposed combining scheme is compared with that of the conventional scheme without weighting factors in various environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3A
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• pp.235-243
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• 2009

In this paper, we investigate the cognitive and cooperative communication scheme to improve the spectral efficiency in multiuser OFDMA systems using wireless relays. First, we propose the frame structure in which the efficient frequency reuse scheme with the cognitive technique is performed to increase the system throughput. And in the case where the THP (Tomlinson-Harashima preceding) is used for the elimination of interference from the relay, we derive the effective signal to noise ratio of the link largely affected by the channel quantization error. From the system level simulation results, it is shown that the proposed cognitive and cooperative communication scheme increases the overall system performance including the feedback overhead.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3A
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• pp.185-196
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• 2009

SCA is proposed in order to operate various wireless systems in the single terminal platforms and uses the CORBA middleware to guarantee the platform-independence for software components. As the reconstruction demand is expanded in the software component to the logic level to many reasons, CORBA has to guarantee the independence of hardware on board. Accordingly. the characteristics depending on hardware board is ed. And the IDL-based interworking interface about the component has to be provided. In this paper, we described about local transport for guaranteeing the independency on the hardware board and the HAO Core for providing a coupling by the CORBA IDL identically with the other component. HAO produced at 2,900 logic cell size in average and provided the performance of the tens times than the software component. Through the use of HAO in the SCA-based development environment, it was naturally expanded to not only the software area but also the FPGA logic.