• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.73-76
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• 2003

The capacity of backbone networks has largely kept pace with the tremendous of growth of Internet traffic. But there has been little progress in the access networks. In this paper, we introduce the access network that is able to offers high bandwidth and its simple protocol. The network architecture is basically multiple ring and use WDM(Wavelength Division Multiplexing), SCM (SubCarrier Multiplexing), and static WADM (Wavelenth Add/Drop Multiplexer) for simplicity, low cost, and offering high bandwidth.

• The Journal of the Korea Contents Association
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• v.6 no.10
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• pp.153-162
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• 2006

The WDM/SCM-FTTH is an advanced optical access Network that can efficiently support various kinds of access network requirements using the WDM and SCM technologies in the near future. In this paper, we propose new network structures of the FTTH(Fiber To The Home) in the WDM(Wavelength Division Multiplexing) and WDM/SCM(Sub-Carrier Multiplexing) FTTH, and evaluate its performance with simulation results for the optical characteristics of the network and the dynamic allocation of bandwidth on demand of the users.

• Journal of Broadcast Engineering
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• v.15 no.3
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• pp.407-413
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• 2010

In DCA (Dynamic Channel Allocation) scheme of uplink cellular system appling a frequency reuse factor of one, when a new call requests a channel, the new call will be blocked if its SINR (Carrier to Noise and Interference Ratio) is less than the required SINR or there is no available channel. The additional channel allocation for the blocked new call can be performed with channel borrowing in the adjacent cells. The channel borrowing causes the CCI (Co-Channel Interference), thus the SINR of the existing calls is deteriorated and the channel reallocation for the existing calls is required. As a result, the channel borrowing leads to a complex calculation so that it is a NP-hard problem. Therefore, to overcome the problem, we propose a novel Group Search-based DCA scheme which decreases the number of the blocked new calls and then reduces the number of the channel reallocation by the channel borrowing for the blocked new calls. The proposed scheme searches the all channels in a group of the adjacent cells and home cell at the same time in order to minimizes the number of the blocked new calls. The simulation results show that proposed Group Search-based DCA scheme provides better new call blocking probability and system throughput than the existing Single Search-based DCA scheme which searches only the channels in home cell.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.307-314
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• 2011

A new predistortion technique for dynamic spectrum allocation systems such as cognitive radio (CR) is proposed. The system model considered in this paper occupies a small band at a time, but the center frequency can be changed in the wide range of frequency. In this scenario. the front-end filter may not eliminate the harmonics of the power amplifier (PA) output. The proposed PD reduces the spectral regrowth of the fundamental signal at the carrier frequency (${\omega}_0$) and removes the harmonics ($2{\omega}_0$, $3{\omega}_0$, ...) at the same time. The proposed PD structure is composed of multiple predistorters (PDs) centered at integer multiples of ${\omega}_0$. The PD at ${\omega}_0$ is for removing spectral regrowth of the fundamental signal, and the others are for harmonic reduction. In the proposed PD structure, parameters of PDs are found jointly. Simulation results show that the spectral regrowth can be reduced by 20dB, and the 2nd and 3rd harmonics can be reduced down to -70dB from the power of the fundamental signal.