• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.1
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• pp.87-99
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• 1998

In the multicasting communications, the quality of service is not guaranteed occasionally, according to the shortage of resources, because all resources such as communication buffer, processing power for the packet multiplication, and bandwidth, should be shared among each members. This problem can be solved through the hierarchical multicaster construction mechanism which guarantees that all multicaster can be operated within the required performance. This paper proposes the architecture of multipoint communication server based on hypercube type massively parallel computer. Through the simulation, it is verified that the traffic of links between each node of hypercube computer is under the some bandwidth. So, it is certified that the hypercube computer is suitable for the multicast communication servers supporting the various groups.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1999.10a
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• pp.50-50
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• 1999

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.85-85
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• 2004

• The KIPS Transactions:PartB
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• v.9B no.6
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• pp.835-844
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• 2002

The number of channels available to a video server is limited since the number of channels a video server can support is determined by its communication bandwidth. Several approaches such as batching, piggybacking and patching have been proposed to reduce I/O demand on the video server by sharing multicast data. Patching has been shown to be efficient in the matter of the cost for VOD systems. Unlike conventional multicast techniques, patching is a dynamic multicast scheme which enables a new request to join an ongoing multicast. In addition, true VOD can be achieved since a new request can be served immediately without having to wait for the next multicast. In this paper. we propose two types of channel reservation patching algorithm : a fixed channel reservation patching and a variable channel reservation patching. To immediately schedule the requests for popular videos, these algorithms reserve the channels of video server for the fixed number of popular videos or for the variable number of popular videos which is determined dynamically according to the load of video server. The performance of the proposed algorithms is evaluated through simulations, and compared with that of simple patching. Our performance measures are average defection rate, average latency, service fairness and the amount of buffered data according to video server loads. Simulation results show that the proposed channel reservation patching algorithms provide better performance compared to simple patching algorithm.

• The KIPS Transactions:PartC
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• v.13C no.3 s.106
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• pp.339-344
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• 2006

Secure delivery of multicast data can be achieved with the use of a group key for data encryption in mobile ad hoc network (MANET) applications based on the group communication. However, for the support of dynamic group membership, the group key has to be updated for each member joining/leaving and, consequently, a mechanism distributing an updated group key to members is required. The two major categories of the group key distribution mechanisms proposed for wired networks are the naive and the tree-based approaches. The naive approach is based on unicast, so it is not appropriate for large group communication environment. On the other hand, the tree-based approach is scalable in terms of the group size, but requires the reliable multicast mechanism for the group key distribution. In the sense that the reliable multicast mechanism requires a large amount of computing resources from mobile nodes, the tree-based approach is not desirable for the small-sized MANET environment. Therefore, in this paper, we propose a new key distribution protocol, called the proxy-based key management protocol (PROMPT), which is based on the naive approach in the small-sized MANET environment. PROMPT reduces the message overhead of the naive through the first-hop grouping from a source node and the last-hop grouping from proxy nodes using the characteristics of a wireless channel.

• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.88-96
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• 2001

Future mobile communication networks, which consist of ATM-based B-ISDN backbone networks and wireless ATM networks, will provide u user with broadband connection and QoS service. These network systems need the lossless handoff methods which support user mobility, satisfy ATM features such as ATM cell ordering and no ATM cell duplication and minimize buffer requirement for ATM cell buffering. In this paper we suggest a multicast-based handoff method to supp$\alpha$t lossless connection as well as to minimize buffer overhead. It establishes a dynamic multicast connection between source terminal and wireless member AP (access point)s. When the mobile terminal receives data packet correctly, it notifies the positive acknowledgement of the packet to all member APs. And member APs then release the MT related temporary buffer space for MT's future movement. Therefore member APs can eliminate unnecessary buffer usage and manage the buffer space efficiently. Analysis result shows that our handoff method has better performance in buffer requirement for lossless and seamless connection services over VCT (virtual connection tree) method and other dynamic multicast-based handoff methods.

• Journal of the Korea Computer Industry Society
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• v.3 no.9
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• pp.1235-1244
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• 2002

This paper proposes a group key management protocol for a secure of all the multicast user in PIM-SM multicast group communication. With prosed architect, subgroups for multicast secure group management will be divided by RP (Rendezvous-Point) unit and each RP has a subgroup manager. Each subgroup manager gives a secure key to it's own transmitter md the transmitter compress the data with it's own secure key from the subgroup manager. Before the transmitter send the data to receiver, the transmitter prepare to encrypt a user's service by sending a encryption key to the receiver though the secure channel, after choking the user's validity through the secure channel. As the transmitter sending a data after then, the architecture is designed that the receiver will decode the received data with the transmitter's group key. As a result, the transmitting time is shortened because there is no need to data translation by group key on data sending and the data transmition is possible without new key distribution at path change to SPT (Shortest Path Tree) of the router characteristic. Additionally, the whole architecture size is samller than the other multicast secure architecture by using the conventional PIM-SIM routing structure without any additional equipment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.55-63
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• 2007

Multicast is an efficient transport mechanism for community communications and MANET is recently regarded as a promising solution for support ubiquitous computing as an underlying network technology. However, it is hard to deploy multicast mechanism into MANET owing to scarce resources in wireless networks and unpredictable changes in network topology. Several multicast mechanisms have been proposed in the literature to overcome the limitations. Especially, overlay multicasting schemes present several advantages over network based multicasting schemes. Yet, the overlay multicasting schemes still introduce redundant data transmissions that waste network bandwidth and battery of relay nodes. As a result the performance of the network is degraded. To reduce the redundancy, we propose an efficient way to construct an overlay structure as a multicast data delivery tree that utilizes a branch node which belongs to the tree. By using network simulation, we show that the proposed scheme presents higher packet delivery ratio and lower transmission cost than previously proposed schemes.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.1
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• pp.29-34
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• 2012

Wireless multicast service can be used for video streaming service to save the network resources by sending the same popular multimedia contents to a group of users at once. For better multimedia streaming multicast service, we propose a quality-aware rate adaptation (QARA) scheme for scalable video multicast in rate adaptive wireless networks. In QARA, transmission rate is determined depending on the content's type and users' channel conditions. First, the base layer is transmitted by a low rate for high reliability. That means we provide basic service quality to all users. On the contrary, the transmission rate for enhancement layer is adapted by using channel condition feedback from a randomly selected node. So, the enhancement layer frames in a multimedia content is sent with various transmission rates. Therefore, each node can be provided with differentiated quality services. Consequently, QARA is capable of serving heterogeneous population of mobile nodes. Moreover, it can utilize network resources more efficiently. Our simulation results show that QARA outperforms utilization of the available transmission rate and reduces the data transmission time.

• Journal of KIISE:Information Networking
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• v.36 no.5
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• pp.437-455
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• 2009

In the near future, various multicast based services will be provided over clustered wireless networks. To provide multicast services in secure manner, multicast messages are encrypted by using group key which is shared by group members. Therefore, various group key management schemes have been introduced until now. Among them, tree based approach is one of the most representative paradigms in group key management. Traditional tree based approaches effectively reduce rekeying message transmissions of the key distribution center. However, they do not consider the network bandwidth used for transmitting the rekeying messages. In this paper, we firstly present formulas that describe bandwidth consumption of tree based group key management scheme. Based on our formulations, we propose a bandwidth efficient key tree management scheme for clustered wireless networks where membership changes occur frequently. Simulation results show that our scheme effectively reduces the bandwidth consumption used for rekeying compared to existing key tree schemes.