• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3C
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• pp.170-174
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• 2011

We introduce the network coding which cooperative communication for two-way relay channel. We propose a new network coding scheme using orthogonality for cooperative communication system. The proposed network coding scheme via orthogonal mapping shows better BER performance because proposed scheme weakens error propagation which is disadvantage of DF scheme. And proposed scheme maintains same throughput compared to conventional scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.1
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• pp.64-71
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• 1997

Digital communication channels are imparied by linear effects such as dispersion, ISI(intersymbol Interference), fading phenomenon etc. But, the practical channel equalization system is required to design for compensating the nonlinear distortion caused by harmonic distortion etc. This paper is a study on the performance of nonlinear channel equalization using RBF(Radial Basis Funclion) network, which has the equivalent structure to the optimal Basian filter. Expecially, the variance of RBF network is modifiedby nonlinear polynomial filters to compare the convergence characteristic of nonlinear channel equalization. Experimental results show that the modified RBF network achieves the faster convergence property than conventional RBF network. Moreover, the RBF network ofhigher order variance modified represents the better performance than that of lower order variance in the bandpass channels and second/third order polynomial channels.

• Journal of Information Processing Systems
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• v.18 no.1
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• pp.12-25
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• 2022

In recent years, deep convolutional neural networks have made significant progress in the research of single image super-resolution. However, it is difficult to be applied in practical computing terminals or embedded devices due to a large number of parameters and computational effort. To balance these problems, we propose CSRNet, a lightweight neural network based on channel split residual learning structure, to reconstruct highresolution images from low-resolution images. Lightweight refers to designing a neural network with fewer parameters and a simplified structure for lower memory consumption and faster inference speed. At the same time, it is ensured that the performance of recovering high-resolution images is not degraded. In CSRNet, we reduce the parameters and computation by channel split residual learning. Simultaneously, we propose a double-upsampling network structure to improve the performance of the lightweight super-resolution network and make it easy to train. Finally, we propose a new evaluation metric for the lightweight approaches named 100_FPS. Experiments show that our proposed CSRNet not only speeds up the inference of the neural network and reduces memory consumption, but also performs well on single image super-resolution.

• The KIPS Transactions:PartA
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• v.12A no.7 s.97
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• pp.627-636
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• 2005

This paper presents a PC cluster-based distributed video on demand (VOD) server that minimizes the load of the interconnection network by adopting channel bonding-based MVIA and the interval cache algorithm Video data is distributed to the disks of each server node of the distributed VOD server and each server node receives the data through the interconnection network and sends it to clients. The load of the interconnection network increases because of the large volume of video data transferred. We adopt two techniques to reduce the load of the interconnection network. First, an Msupporting channel bonding technique is adopted for the interconnection network. n which is a user-level communication protocol that reduces the overhead of the TCP/IP protocol in cluster systems, minimizes the time spent in communicating. We increase the bandwidth of the interconnection network using the channel bonding technique with MThe channel bonding technique expands the bandwidth by sending data concurrently through multiple network cards. Second, the interval cache reduces traffic on the interconnection network by caching the video data transferred from the remote disks in main memory Experiments using the distributed VOD server of this paper showed a maximum performance improvement of $30\%$ compared with a distributed VOD server without channel bonding-based MVIA and the interval cache, when used with a four-node PC cluster.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.153-164
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• 2010

In this paper, we propose a multi-channel MAC protocol to improve the channel efficiency and network performance in wireless ad hoc networks. There are two main problems encountered in designing multi-channel MAC protocols. The first problem is the rendezvous problem and the second is multi-channel hidden node problem. In order to solve these problems, most of previous researches that have considered multi-channel MAC protocols use a common control channel to exchange control packets. However, they have a bottleneck problem at common control channel as increasing the number of data channels. The proposed MAC protocol solves the multi-channel hidden node problem using a TDMA scheme and increases the network throughput because transmitting and receiving data at the same time is possible. Also, since there is no common control channel, the network does not suffer from the common control channel saturation problem. Moreover, it achieves energy savings by allowing nodes that are not involved in communication to go into sleep mode. Simulation results show that the proposed MAC protocol improves the network throughput and channel efficiency and provides energy savings.

• 한국디지털정책학회:학술대회논문집
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• 2005.06a
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• pp.277-283
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• 2005

In this paper, the performance of high data rate-wirelesss personal area network(HDR-WPAN) system is analyzed under multi-path indoor channel. In the analysis, Saleh and Valenzuel channel model is used for the multi-path indoor channel. From the results, HDR-WPAN system has reliability of 10-5 at Eb/No = 18.5dB in multi-path indoor channel. It is a suitable performance for high data rate personal area network applications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.248-255
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• 2009

We proposed a power line channel model. We adopted advantages of other power line channel models to calculate channel responses correctly and simply. Infinite geometric series reduced the calculation complexity of the multipath signal propagation. Description Matrices were also adopted to handle the network topology easily. It represents complex power line network precisely and simply. Newly proposed model considered the effect of the adjacent nodes to channel responses, which have been not considered so far. Several simulations were executed to verify the effect of the adjacent nodes. As a result we found out that it affected channel responses but its effect was limited within certain degree.

• The Journal of the Acoustical Society of Korea
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• v.26 no.2E
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• pp.63-68
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• 2007

Using the neural network model for oriented principal component analysis (OPCA), we propose a solution to the data least squares (DLS) problem, in which the error is assumed to lie in the data matrix only. In this paper, we applied this neural network model to channel equalization. Simulations show that the neural network based DLS outperforms ordinary least squares in channel equalization problems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.7
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• pp.1465-1470
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• 2011

In this paper, we propose a new MAC protocol, namely DM-MMAC (Doze Mode Multi-Channel MAC) for ad hoe wireless networks which can utilize multiple channels effectively, thereby enhancing the network throughput considerably. Basically, the IEEE 802.11 specification allows for the use of multiple channels available at the physical layer, but its MAC protocol is designed only for a single channel with the fatal drawback, so called multi-channel hidden terminal problem in multi-channel environments. In this vein, several multi-channel MAC protocols have been proposed, but most of them demonstrate the performance problem that its throughput drastically decreases as the number of mobile hosts residing in a given network increases with small number of available channels. In this work, we tried to improve the performance of multi-channel MAC protocols in terms of network throughput as well as power saving effects by simplifying the channel assignment and channel capturing procedures and reducing the possibility of collisions between mobile hosts.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.5
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• pp.2362-2378
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• 2017

To mitigate the performance degradation caused by performance anomaly, a number of channel assignment algorithms have been proposed for multi-rate wireless mesh networks. However, network conditions have not been fully considered for routing process in these algorithms. In this paper, a joint scheme called Multi-rate Dijkstra's Shortest path - Rate Separated (MDSRS) is proposed, combining routing metrics and channel assignment algorithm. In MDSRS, the routing metric are determined through the synthesized deliberations of link costs and rate matches; then the rate separated channel assignment is operated based on the determined routing metric. In this way, the competitions between high and low rate links are avoided, and performance anomaly problem is settled, and the network capacity is efficiently improved. Theoretical analysis and NS-3 simulation results indicate that, the proposed MDSRS can significantly improve the network throughput, and decrease the average end-to-end delay as well as packet loss probability. Performance improvements could be achieved even in the heavy load network conditions.