• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.485-492
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• 2003

This paper presents a new modified input buffered switch, which called a grouped input buffered (GIB) switch, to eliminate the influence of HOL blocking when using multiple input buffers in ATM switches. The GIB switch consists of grouped sub switches per a network stage. The switch gives extra paths and buffered switching elements between groups for transferring the blocked cells. As the result, the proposed model can reduce the effect by the HOL blocking and thereafter it enhances the performance of the switch. The simulation results show that the proposed scheme has good performance in comparison with previous works by using the parameters such as throughput, cell loss, delay and system power.

• KIISE Transactions on Computing Practices
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• v.23 no.12
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• pp.677-683
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• 2017

Apache Storm is a representative real-time distributed processing system, which is able to process data streams quickly over distributed servers. Storm currently provides several stream grouping methods to distribute data traffic to multiple servers. Among them, the shuffle grouping may cause a processing delay problem and the local-or-shuffle grouping used to solve the problem may cause the problem of concentrating the traffic on a specific node. In this paper, we propose the locality-aware grouping to solve the problems that may arise in the existing Storm grouping methods. Experimental results show that the proposed locality-aware grouping is considerably superior to the existing shuffle grouping and the local-or-shuffle grouping. These results show that the new grouping is an excellent approach considering both the locality and load balancing which are limitations of the existing Storm.

• The KIPS Transactions:PartC
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• v.12C no.1 s.97
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• pp.105-110
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• 2005

With the proliferation of multimedia group applications, the construction of multicast trees satisfying QoS requirements is becoming a problem of prime importance. In this paper, we study the delay- and delay variation-bounded multicast tree (DVBMT) problem which is NP-complete. The problem is to construct a spanning tree for destination node, which has the minimized multicast delay variation, and the delay on the path from the source to each destination is bounded. A solution to this problem is required to provide decent real-time communication services such as on-line games, shopping, and teleconferencing. Performance comparison shows that the proposed scheme outperforms DDVCA which is known to be effective so far in any network topology. The enhancement is up to about $3.6{\%}{\~}11.1{\%}$ in terms of normalized surcharge for DUVCA. The time complexity of our algorithm is $O(mn^2)$.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.48-55
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• 2015

This paper studies how to solve a problem caused by M2M terminals sending a few data based on $3^{rd}$ Generation Partnership Project(3GPP) Long Term Evolution-Advanced(LTE-A) system and then it is analyzed, proposed, and introduced into the techniques. Especially, it is introduced solution for the lack of Random Access Channel and an increasing number of latency caused by countless M2M devices. It is proposed the technology for M2M grouping as well as allowable access probability according to user type. As it decreases the number of terminal by grouping M2M devices to try random access at PRACH, it can be reduced collision between Cellular users and M2M devices. So, it is proved that the proposed mechanism can solve the increasing average latency of random access on system coexisting Cellular users and M2M devices through simulations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.7
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• pp.1602-1608
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• 2013

PoC (Push-to-Talk over Cellular) provides one-to-one as well as one-to-many communications with VoIP technology based on SIP over cellular networks. According to above property, PoC is considered as perscrptive technology for public protection for disaster relief networks. For this networks, group communication is the essential function. However, since current standardization process takes into general scenarios account without any consideration for mentioned networks, it have some problems in the point of adaptability. To solve above problem, in this paper, we propose how to reduce the overhead on the PoC server to reduce the transmission delay. Simulation results are shown to evaluate the improved performance.

• Journal of KIISE:Databases
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• v.29 no.6
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• pp.502-512
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• 2002

Most of previous replication schemes assume lazy schemes, which asynchronously propagate replica updates to other nodes after the updating transaction commits. While lazy schemes are novel in the sense that they can resolve high deadlock frequencies of eager schemes, they suffer from the fact that users should be responsible for the data consistency. Recently replication schemes based on the messaging order of group communication have been studied. They can reduce the deadlock frequencies using the messaging order, but they have another problem of increasing execution overhead of aborted transactions at high degree of concurrency. This is because the sender node validates global serializability after multicasting replica update messages to other nodes. In this paper, we propose an efficient eager replication scheme for reducing the number of messaging and overhead of aborted transactions significantly. The proposed scheme validates any conflicts before multicasting and does not multicast when there is any conflict; hence, it can exploit performance improvement by alleviating the message traffic for replica update or by reducing the number of disk accesses and locking delay due to aborted transactions.

• Journal of KIISE:Databases
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• v.29 no.6
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• pp.500-500
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• 2002

Most of previous replication schemes assume lazy schemes, which asynchronously propagate replica updates to other nodes after the updating transaction commits. While lazy schemes are novel in the sense that they can resolve high deadlock frequencies of eager schemes, they suffer from the fact that users should be responsible for the data consistency. Recently replication schemes based on the messaging order of group communication have been studied. They can reduce the deadlock frequencies using the messaging order, but they have another problem of increasing execution overhead of aborted transactions at high degree of concurrency. This is because the sender node validates global serializability after multicasting replica update messages to other nodes. In this paper, we propose an efficient eager replication scheme for reducing the number of messaging and overhead of aborted transactions significantly. The proposed scheme validates any conflicts before multicasting and does not multicast when there is any conflict; hence, it can exploit performance improvement by alleviating the message traffic for replica update or by reducing the number of disk accesses and locking delay due to aborted transactions.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.9 s.339
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• pp.29-40
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• 2005

In this paper, we propose a Cluster-based Multicast Routing (CMR) suitable for mobile ad-hoc networks. The main features that our proposed method introduces are the following: a) mobility-based clustering and group based hierarchical structure in order to effectively support stability and scalability, b) group based mesh structure and forwarding tree concepts in order to support the robustness of the mesh topologies which provides limited redundancy and the efficiency of tree forwarding simultaneously, and c) combination of proactive and reactive concepts which provide low route acquisition delay and low overhead. The performance evaluation of the proposed protocol is achieved via modeling and simulation. The corresponding results demonstrate the Proposed multicast protocol's efficiency in terms of packet delivery ratio, scalability, control overhead, end-to-end delay, as a function of mobility, multicast group size, and number of senders.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1B
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• pp.45-54
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• 2003

In the Protocol-Independent Multicast Sparse Mode(PIM-SM), we need a careful selection scheme for the Rendezvous Point(RP) which influences much on the QoS due to the delay among multicast group members and packet loss The QoS based RP selection schemes choose RPs which satisfy the restriction conditions such as bandwidth, delay, and other QoS parameters In this paper, we propose a new RP selection scheme which is a variation of the group-based RP selection scheme The new algorithm, MCT(Maximum Cross Tree), is implemented by taking advantages of the topology-based selection scheme and the group-based selection scheme as well In order to verify the proposed algorithm, we first measure the multicast traffic data of the Virtual Conference System implemented on the IPv6 network via KOREN, then expand the results to two types of network models and analyze the performance by computer simulation.

• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.307-315
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• 2003

This paper proposes a Multicast Tree Extension (MTE) scheme for multicast in IP-based wireless networks. If a group receiver Joins a multicast group in a visited foreign network, multicast service may be disrupted when the foreign network does not have a multicast router. To avoid disruption, our scheme creates a bi-directional tunnel between the previous foreign agent (FA) and new foreign agent, if a mobile node (MN) moves from a foreign network with multicast capability to another foreign network with non-multicast capability. The MN thus continues to receive the multicast packets through the tunnel from the previous FA. Our scheme can avoid a long latency due to a long tunneling for group membership as well as multicast service disruption, even if the MN enters foreign networks with non-multicast capability. Simulation results show that our scheme offers lower costs for multicast delivery, tunneling and handoff latency than the existing scheme.