• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.6
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• pp.77-82
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• 2012

In this paper, the new location management scheme based on region and movement threshold has been proposed in order to minimize the required cost to handle the resource location management signaling traffics under the wire/wireless convergent networks when the users are moving around the cold and hot regions. In this scheme, the sequential paging is supposed to be performed according to the movement threshold which can be changed in accordance with the number of movements that each mobile user had made while it is moving around the resource regions. With the proposed scheme, the cost of managing the location management traffics and efficient spectrum assignment overhead can be minimized by placing signaling traffics for location managements and also allocating radio spectrum considering individual movement behaviors.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.950-975
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• 2016

Device-to-Device (D2D) communication underlaying cellular networks is a promising add-on component for future radio communication systems. It provides more access opportunities for local device pairs and enhances system throughput (ST), especially when mobile relays (MR) are further enabled to facilitate D2D links when the channel condition of their desired links is unfavorable. However, mutual interference is inevitable due to spectral reuse, and moreover, selecting a suitable transmission mode to benefit the correlated resource allocation (RA) is another difficult problem. We aim to optimize ST of the hybrid system via joint consideration of mode selection (MS) and RA, which includes admission control (AC), power control (PC), channel assignment (CA) and relay selection (RS). However, the original problem is generally NP-hard; therefore, we decompose it into two parts where a hierarchical structure exists: (i) PC is mode-dependent, but its optimality can be perfectly addressed for any given mode with additional AC design to achieve individual quality-of-service requirements. (ii) Based on that optimality, the joint design of MS, CA and RS can be viewed from the graph perspective and transferred into the maximum weighted independent set problem, which is then approximated by our greedy algorithm in polynomial-time. Thanks to the numerical results, we elucidate the efficacy of our mechanism and observe a resulting gain in MR-aided D2D communication.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.7
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• pp.2530-2547
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• 2015

In the recent years, femtocell technology has received a considerable attention due to the ability to provide an efficient indoor wireless coverage as well as enhanced capacity. However, under the spectrum sharing between femtocell user equipment (FUEs) and the owner of spectrum macrocell user equipment (MUEs), both may experience higher uplink interference to each other. This paper proposes a novel distributed power control algorithm for the interference management in two-tier femtocell networks. Due to the assignment of licensed radio frequency to the outdoor macrocell users, the access priority of MUEs should be higher than FUEs. In addition, the quality of service (QoS) of MUEs that is expressed in the target signal-to-interference-plus-noise ratio (SINR) must always be achieved. On the other hand, we consider an efficient QoS provisioning cost function for the low-tier FUEs. The proposed algorithm requires only local information and converges even in cases where the frontiers of available power serve the target SINRs impossible. The advantage of the algorithm is the ability to implement in a distributed manner. Simulation results show that the proposed algorithm based on our cost function provides effective resource allocation and substantial power saving as compared to the traditional algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.12
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• pp.1102-1112
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• 2012

We propose a cell selection and resource allocation scheme that assigns users to nearby accessible cells in heterogeneous wireless networks consisting of macrocell, femtocells, and Wi-Fi access points, under overload situation. Given the current power level of all accessible cells nearby users, the proposed scheme finds all possible cell assignment mappings of which user should connect to which cell to maximize the number of users that the network can accommodate at the same time. We formulate the cell selection problem with heterogeneous cells into an optimization problem of binary integer programming, and compute the optimal solution. We evaluate the proposed algorithm in terms of network access failure compared to a local ad-hoc based cell selection scheme used in practical systems using network level simulations. We demonstrate that our cell selection algorithm dramatically reduces network access failure in overload situation by fully leveraging network resources evenly across heterogeneous networks. We also validate the practical feasibility in terms of computational complexity of our binary integer program by measuring the computation time with respect to the number of users.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.5
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• pp.724-729
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• 2008

This paper presents the calculation of the required bandwidth of common frequency bandwidth applying queueing theory for maximizing the efficiency of frequency resource of WPAN(Wireless Personal Area Network) based Digital acoustic and communication devices. It assumed that LBT device(ZigBee) and FH devices (DCP, RFID and Bluetooth) coexist in the common frequency band for WPAN based Digital acoustic and communication devices. Frequency hopping (FH) and listen before talk (LBT) have been used for interference avoidance in the short range device (SRD). The LBT system transmits data after searching for usable frequency bandwidth in the radio wave environment. However, the FH system transmits data without searching for usable frequency bandwidth. The queuing theory is employed to model the FH and LBT system, respectively. As a result, the throughput for each channel was analyzed by processing the usage frequency and the interval of service time for each channel statistically. When common frequency bandwidth is shared with SRD using 250mW, it was known that about 35 channels were required at the condition of throughput 84%, which was determined with the input condition of Gaussian distribution implying safety communication. Therefore, the common frequency bandwidth is estimated with multiplying the number of channel by the bandwidth per channel. These methodology will be useful for the efficient usage of frequency bandwidth.

• The Korean Journal of Air & Space Law and Policy
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• v.29 no.2
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• pp.239-272
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• 2014

The rights and obligations of the Member States of ITU in the domain of international frequency management of the spectrum/orbit resource are incorporated in the Constitution and Convention of the ITU and in the Radio Regulations that complement them. These instruments contain the main principles and lay down the specific regulations governing the major elements such as rights and obligations of member administrations in obtaining access to the spectrum/orbit resource, as well as international recognition of these rights by recording frequency assignments and, as appropriate, any associated orbits, including the geostationary-satellite orbits used or intended to be used in the Master International Frequency Register (MIFR) Coordination is a further step in the process leading up to notification of the frequency assignments for recording in the MIFR. This procedure is a formal regulatory obligation both for an administration seeking to assign a frequency in its network and for an administration whose existing or planned services may be affected by that assignment. Regulatory problem lies in allowing administrations to fulfill their "bringing into use" duty for preserving his filing simply putting any satellites, whatever nationlity or technical specification may be, into filed orbit. This sort of regulatory lack may result in the emergence of the secondary market for satellite orbit. Within satellite orbit secondary market, the object of transaction may be the satellite itself, or the regulatory rights in rem, or the orbit registered in the MIFR. Recent case of selling the Koreasat belongs to the typical example of orbit transaction between private companies, the legality of which remains doubtedly controversial from the perspective of international space law as well as international transaction law. It must be noted, however, that the fact is the Koreasat 3 and its filed orbit is for sale.