• The KIPS Transactions:PartC
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• v.16C no.6
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• pp.773-782
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• 2009

A DHT(Distributed Hash Table) based P2P is a method to overcome disadvantages of the existing unstructured P2P method. If a DHT algorithm is used, it can do a fast data search and maintain search efficiency independent of the number of peer. The peers in the DHT method send messages periodically to keep the routing table updated. In a mobile environment, the peers in the DHT method should send messages more frequently to keep the routing table updated and reduce the failure of a request. Therefore, this results in increase of network traffic. In our previous research, we proposed a method to reduce the update load of the routing table in the existing Chord by updating it in a reactive way, but the reactive method had a disadvantage to generate more traffic than the existing Chord if the number of requests per second becomes large. In this paper, we propose an adaptive method of routing table update to reduce the network traffic. In the proposed method, we apply different routing table update method according to the number of request message per second. If the number of request message per second is smaller than some threshold, we apply the reactive method. Otherwsie, we apply the existing Chord method. We perform experiments using Chord simulator (I3) made by UC Berkeley. The experimental results show the performance improvement of the proposed method compared to the existing methods.

• Smart Media Journal
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• v.9 no.2
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• pp.16-21
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• 2020

Recently, mobile traffic is increasing exponentially as major traffic is transferred to IoT and visual media data in the dissemination of mobile communication terminals and contents use. In order to overcome the limitations of the existing LTE system, 5G mobile communication technology (5G) is a technology that meets 1000 times data traffic capacity, 4G LTE system acceptance, low latency, high energy efficiency, and high cost compared to 4G LTE system. The path loss due to the use of the frequency domain is very high, so it may be difficult to provide a service compared to the existing 4G LTE system. To overcome these shortcomings, various techniques are under study. In this paper, small cell technology is introduced to improve the system performance of 5G mobile communication systems. The performance is analyzed by comparing the results of small cell technology application, macro communication and small cell communication, and the results of the proposed algorithm application for power control. The analysis results show that the use of small cell technology in the 5th generation mobile communication system can significantly reduce the shadow area and reduce the millimeter wave path loss problem.

• Journal of Satellite, Information and Communications
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• v.9 no.1
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• pp.51-56
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• 2014

High-availability seamless redundancy (HSR) is a protocol for fault-tolerant Ethernet (FTE) networks. It provides two frame copies and each copy is forwarded on a separate physical path, which provides zero fail-over time. Therefore, the HSR is becoming a potential candidate for various real-time FTE applications. However, the generation and circulation of unnecessary frames due to the duplication of every sending frame is inherent drawback of HSR. Such drawback degrades the performance of the network and may deplete its resources. In this paper, we present a new algorithm called port locking (PL) based on the media access control (MAC) address to solve the abovementioned problem in popular connected-rings network. Our approach makes the network gradually learn the locations of the source and the destination nodes without relying on network control frames. It then prunes all the rings that do not contain the destination node by locking corresponding rings' entrance ports. With the PL algorithm, the traffic can be significantly reduced and therefore the network performance will be greatly enhanced specially in a large scale connected-rings network. Analytical results are provided to validate the PL algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.717-727
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• 2003

The HIPERLAN/2(HIgh PERformance Local Area Network Type2) is one of the wireless LAN standards for providing raw data rates of up to 54 Mbps. The MAC protocol of HIPERLAN/2 is based on TDMA/TDD, and resources in one MAC frame can be allocated dynamically by Access Point(AP). The random channel(RCH) is defined for the purpose of giving a mobile terminal the opportunity to request transmission resources in the uplink MAC frames. It is desirable that the number of RCHs is dynamically adapted by the AP depending on the current traffic situation. Allocation of excessive RCHs may waste radio resources and insufficient RCHs compared to traffic loads may result in many collisions in access attempts. We propose an RCH allocation scheme based on split algorithm in HIPERLAN/2. The simulation and analytic results show that the proposed scheme achieves a higher channel throughput, lower access delay and delay jitter than previously proposed RCH allocation schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1067-1074
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• 2004

In the wireless mobile networks, it IS important to provide the quality-of-service (QoS) guarantees as they are increasingly expected to support the multimedia applications Although the QoS provisioning problem arises in the wire-line networks as well, the mobility of hosts and the scarcity of bandwidth make QoS provisioning a challenging task in wireless mobile networks. The resource allocation to multimedia applications of varying QoS reqUlrement 15 a complex issue. In this paper, we propose a new adaptive resource allocation scheme based on the concept of the resource reservation and the renegotiation in order to guarantee the QoS of the real-tune traffic. The proposed scheme is aimed at improving the perfonnance in terms of the new call blocking rate, the bandoff dropping rate, and the bandwIdth utilization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.8
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• pp.1792-1798
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• 2010

Home Gateway is always on for continuous services of home networks. Ubiquitous home networks are extended. so power consumption of home gateways increases by geometric progression. Our algorithm is for home gateway to sleep, listen or wakeup according to network traffic adaptively, as well as to keep always-on service. To do this, it traces the accumulated average of previous sleep periods. In addition to this basic algorithm, we make the profiles for user's living pattern per the day to reflect network usages in detail and adaptively. As the simulation results by comparing with overall accumulated average and per-day accumulated average, in case of the overall accumulated average, the difference the estimation and real value is distributed from 0.43% to 4%. In contrast of this, in case of the per-day accumulated average is distributed from 0.06% to 2%. From this results, we know the profiling of per-day usage pattern can help reduce the difference of the real sleep period and the estimated sleep period.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10A
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• pp.1501-1506
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• 1999

DSRC(Dedicated Short Range Communications), which is a radio mobile communication protocol in ITS, is suited for traffic related information services. But in WAC(Wide-Area wireless communications), we could consider a conventional communication infrastructure in the case of supporting other applications besides ITS. Especially considering the current the trends to introduce wireless internet service into the mobile communication network, wireless internet service in ITS system is valuable. Although ITS LLC(Logical Link Control) protocols recommended by Europe and Japan are effective for traffic related services, it is not suitable for services related with geographical information, image or internet. That is because the data traffic characteristics is changed according to service types. Therefore we suggest a logical link control algorithm effective for traffic information related services as well as internet web service, and analyze its performance. As a result of numerical analysis and simulation, proposed algorithm shows larger performance improvements. For traffic information related services, the performance of DSRC LLC recommended by Europe and Japan is the same as that of proposed LLC protocol. However, for wireless internet web service, the performance of proposed protocol is much better than that of LLC protocol used in Europe and Japan.

• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.299-313
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• 2002

Recently, the demand for mobile communications and multimedia services has rapidly increased so that conventional cellular system cannot fulfill the requirement of users (capacity and QoS) any more. Therefore, the hierarchical cellular system has been suggested in order to guarantee the QoS and to admit large population of users. IMT-2000 adopts the hierarchical cellular structure, which requires a call control algorithm capable of manipulating and utilizing the complicated structure of hierarchical cellular structure with handiness and efficiency. In this thesis, as an improvement of conventional combined algorithm, a new call control algorithm considering the moving speed of terminal and bandwidth is suggested. This algorithm employs buffers and guard channels to reduce the failure rate. Also, this algorithm considers the moving speed of terminal and bandwidth to elevate the efficiency. Furthermore, calls are handled separately according to the moving speeds of terminal and bandwidths to improve the QoS and reduce the handover rate. As an evaluation of the suggested algorithm, a model hierarchical cellular system is constructed and simulations are conducted with various types of traffic. As the result of the simulations, such indices as block rate, drop rate, channel utilization, and the number of inter layer handovers are examined to demonstrate the excellency fo the suggested algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4B
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• pp.566-575
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• 2010

In recent, artificial immune system has become an important research direction in the anomaly detection of networks. The conventional artificial immune systems are usually based on the negative selection that is one of the computational models of self/nonself discrimination. A main problem with self and non-self discrimination is the determination of the frontier between self and non-self. It causes false positive and false negative which are wrong detections. Therefore, additional functions are needed in order to detect potential anomaly while identifying abnormal behavior from analogous symptoms. In this paper, we design novel network attack detection and response schemes based on artificial immune system, and evaluate the performance of the proposed schemes. We firstly generate detector set and design detection and response modules through adopting the interaction between dendritic cells and T-cells. With the sequence of buffer occupancy, a set of detectors is generated by negative selection. The detection module detects the network anomaly with a set of detectors and generates alarm signal to the response module. In order to reduce wrong detections, we also utilize the fuzzy number theory that infers the degree of threat. The degree of threat is calculated by monitoring the number of alarm signals and the intensity of alarm occurrence. The response module sends the control signal to attackers to limit the attack traffic.

• Journal of KIISE:Information Networking
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• v.30 no.1
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• pp.134-142
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• 2003

We present an ATM switch architectures based on the multistage interconnection network(MIN) for the efficient multicast traffic control. Many of these applications require multicast connections as well as point-to-point connections. Muiticast connection in which the same message is delivered from a source to arbitrary number of destinations is fundamental in the areas such as teleconferencing, VOD(video on demand), distributed data processing, etc. In designing the multicast ATM switches to support those services, we should consider the fairness(impartiality) and priority control, in addition to the overflow problem, cell processing with large number of copies, and the blocking problem. In particular, the fairness problem which is to distribute the incoming cells to input ports smoothly is occurred when a cell with the large copy number enters upper input port. In this case, the upper input port sends before the lower input port because of the calculating method of running sum, and therefore cell arrived into lower input port Is delayed to next cycle to be sent and transmission delay time becomes longer. In this paper, we propose the cell splitting and group splitting algorithm, and also the fairness scheme on the basis of the nonblocking characteristics for issuing appropriate copy number depending on the number of Input cell in demand. We evaluate the performance of the proposed schemes in terms of the throughput, cell loss rate and cell delay.