• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39A no.3
• /
• pp.161-163
• /
• 2014

We consider the device-to-device (D2D) communication underlaying multi-cell interference system, in which the cellular downlink (DL) resource is reused by K cells and two D2D transmission links within each cell. In this paper, it has been shown that the downlink intra-cell and inter-cell interference can be effectively handled by interference alignment (IA) technique, as long as the simultaneous D2D links are properly selected or power-controlled so that they may not incur interference to the base stations in the same and neighbor cells. In particular, we provides the IA technique that can achieve the theoretically maximum possible degree of freedom (DOF), demonstrating that a total of (K+1)M degrees of freedom (DOFs) can be achieved for K-cell interference system with two underlaying D2D links, where base stations, cellular UE's, and D2D UE's all have M transmit and receive antennas.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.9B
• /
• pp.602-609
• /
• 2005

In this paper, the performance of HCS (hierarchical cell structure), which consists of macro-cell and micro-cell, has been analyzed by assuming that the cells in HAPS (high altitude plat(on station) are tessellated to provide wide coverage, control the co-channel interference and give the higher spectrum efficiency. Since the outside-cell interference factor is well blown to analyze the effects of interference between cells, the effects of interference from the micro-cells into the macro-cells has been estimated using the factor as a performance estimation of HCS in HAPS. HCS served by HAPS can be realized by permitting the suitable power control and the proper number of users in micro-cell because the interference from the micro-cell into the macro-cell is not a function of the distance between cells but a function of the power control and the number of users.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.5
• /
• pp.920-926
• /
• 2005

In this paper, we analyzed the effect by building materials in the case of floor cell design and the penetration loss value by material in each frequency bands through an experiment in high building. Specially, the penetration loss measured about interference signal that is received to direct path, interference signal and flowed in slant path. Also, we analyzed system performance according to path of standard Cell received interference signal.

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.229-230
• /
• 2006

In this thesis, we analyze performance related to reduction scheme of inter-cell interference causing serious problems in portable internet system. Frequency reusing factor(FUF) is 1 in portable internet system, and it means that a adjacent cell uses same frequency band. This channel environment raises inter-cell interference problem, which provokes serious problems related to system performance and channel capacity. Consequently, it affects deterioration in system performance as a whole. We analyze inter-cell interference when appling a various schemes such as (DCA)Dynamic Channel Allocation, CS(Channel Segregation), IDMA(Interleave Division Multiple Access), FH-OFDM, CRSA(Conceptual Random Subcarrier Allocation), and HDD

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.10a
• /
• pp.693-696
• /
• 2008

The systems for mobile communication services of fourth generation use OFDM (Orthogonal Frequency Division Multiplexing) scheme that ran transmit large amounts of data to support the multimedia services, and consist of several types of cell, such as Macro Cell, Pico Cell, Femto Cell to improve the qualify of service. According to subdivision of communication region, superposition of cells in co-channel different from conventional single cell is used, but it cause inter band interference between systems. In particular, an OFDM signal consists of a number of independently modulated subcarriers, and superposition of these subcarriers causes a problem that ran give a large PAPR. Increased PAPR induces signal distortion passing through components such as power amplifier so that inter band interference is caused by out-of-band spectrum radiation. In order to minimize the inter band interference, this paper applies PAPR reduction scheme and analyzes the out-of-band spectrum radiation when the signal passes through nonlinear components such an power amplifier.

• Journal of Communications and Networks
• /
• v.15 no.5
• /
• pp.469-475
• /
• 2013

In this paper, we propose an efficient interference management technique which controls the number of resource blocks (or subcarriers) shared with other cells based on statistical interference levels among cells. The proposed technique tries to maximize average throughput of a femto cell user under a constraint on non-real time control of a femto cell network while guaranteeing a target throughput value of a macro cell user. In our proposed scheme, femto cells opportunistically use resource blocks allocated to other cells if the required average user throughput is not attained with the primarily allocated resource blocks. The proposed method is similar to the underlay approach in cognitive radio systems, but resource block sharing among cells is statistically controlled. For the statistical control, a femto cell sever constructs a table storing average mutual interference among cells and periodically updates the table. This statistical approach fully satisfies the constraint of non-real time control for femto cell networks. Our simulation results show that the proposed scheme achieves higher average femto user throughput than conventional frequency reuse schemes for time varying number of users.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.15 no.4
• /
• pp.105-117
• /
• 2015

In this paper, we consider 19 cells with the two tiers for polar-rectangular coordinates (PRCs) and provide the cell edge performance of cellular networks based on distance from cell center i.e., BS (base station). When FFR is applied(or adopted) to cell edge, it is expected that BS cooperation, or a coordinated multipoint (CoMP) multiple access strategy will further improve the system performance. We proposed a new method to evaluate the sum rate capacity of the MIMO DC of multicell system. We improve the performance of cell edge users for intercell interference cancelation in cooperative downlink multicell systems. Simulation results show that the proposed scheme outperforms the reference schemes, in terms of cell edge SINR (signal-to-interference-noise ratio) with a minimal impact on the network path loss exponent. We show 13 dB improvements in cell-edge SINR by using reuse of three relative to reuse of one. BS cooperation has been proposed to mitigate the cell edge effect.

• Journal of Internet Computing and Services
• /
• v.22 no.6
• /
• pp.9-15
• /
• 2021

In ultra-dense heterogeneous networks, the amount of interference from small-cell base stations(SBS) to macro-cell user equipments (MUEs) increases significantly as the number of SBSs increases and it causes the MUEs to decrease the signal-to-interference and noise ratio(SINR) and system capacity. In this paper, we propose a small-cell based cooperative multi-point(CoMP) communication scheme that can guarantee the performance of MUEs even when the number of SBSs increases. In the proposed scheme, MUEs first find SBSs that give signal strength equal to or greater than a given SINR threshold and then they are served by different numbers of the selected SBSs using CoMP to improve the performance of MUEs. Simulation results show that the proposed small-cell based CoMP scheme outperforms other interference management or CoMP schemes in terms of the SINR and system capacity of MUEs.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.5A
• /
• pp.517-525
• /
• 2008

In this paper, we cary out system level simulations to investigate the effect of cell shape(i.e., different base station displacements in the two directions defined by the street grid) on minimizing transmitter power, interference power, and blocking probability for CDMA system in urban microcellular environments. In urban microcell, path loss to the base station depends on the orientation of the street where the mobile is located. Interference from mobile stations to the base station in the reference cell is considered up to second tier. The wrap around method is used to include the second tier interference with realistic computational complexity without reducing the accuracy of interference calculations. The investigation shows that the transmitter power, interference power, and blocking probability in a cell can be reduced by proper selection of the efficient cell shape.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.7
• /
• pp.2231-2245
• /
• 2014

Cognitive Radio (CR) has very promising potential to improve spectrum utilization by allowing unlicensed Secondary Users (SUs) to access the spectrum dynamically without disturbing licensed Primary Users (PUs). Mitigating interference is a fundamental problem in CR scenarios. This is particularly problematic for deploying CR in cellular networks, when users are located at the cell edge, as the inter-cell interference mitigation and frequency reuse are critical requirements for both PUs and SUs. Further cellular networks require higher cell edge performance, then SUs will meet more challenges than PUs. To solve the performance decrease for SUs at the cell edge, a novel Dynamic Spectrum Allocation (DSA) scheme based on Game Theory is proposed in this paper. Full frequency reuse can be realized as well as inter-cell interference mitigated according to SUs' sensing, measurement and interaction in this scheme. A joint power/channel allocation algorithm is proposed to improve both cell-edge user experience and network performance through distributed pricing calculation and exchange based on game theory. Analytical proof is presented and simulation results show that the proposed scheme achieves high efficiency of spectrum usage and improvement of cell edge SUs' performance.