• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.12
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• pp.2267-2273
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• 2016

In this paper, WiMedia Distributed-MAC protocol is adopted for development of an OSMU (One Source Multi Use) N-screen wireless multicast service. But, when considering wireless communication environment where channel error rate is time-variant, N-screen high-speed data is vulnerable to be lost. For this problem, a multicast relay scheme is proposed by analyzing Distributed-MAC protocol. In proposed multicast relay scheme, Multicast-free DRP Availability IE is combined and the relay node suitable for N-screen multicast transmissions is selected. Through this operation, it can avoid wireless channel with high errors and can transmit N-screen high-speed data. In simulation results, the proposed multicast relay scheme is compared with conventional Distributed-MAC multicast scheme in view points of throughput and energy consumption according to various numbers of multicast nodes and BER (Bit Error Rate) values in wireless channel. Through simulation results, it is explained that proposed multicast relay scheme should be adopted in WiMedia Distributed-MAC protocol to realize OSMU N-screen wireless multicast services.

• Journal of KIISE
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• v.43 no.2
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• pp.246-255
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• 2016

The orthogonal frequency-division multiple access (OFDMA) systems are well suited to multi-rate multicast transmission, as they allow flexible resource allocation across both frequency and time, and provide adaptive modulation and coding schemes. Unlike layered video coding, the multiple description coding (MDC) enables flexible decomposition of the raw video stream into two or more substreams. The quality of the video stream is expected to be roughly proportional to data rate sustained by the receiver. This paper describes a mathematical model of resource allocation and throughput in the multi-rate video multicast for the OFDMA wireless and mobile networks. The impact on mean opinion score (MOS), as a measurement of user-perceived quality (by employing a variety of scheduling disciplines) is discussed in terms of utility maximization and proportional fairness. We propose a pruning algorithm to ensure a minimum video quality even for a subset of users at the resource limitation, and show the optimal number of substreams and their rates can sustain.

• Journal of Korea Multimedia Society
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• v.7 no.8
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• pp.1078-1085
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• 2004

The SARLM(Source Adaptive Receiver-Driven Multi-Layered Multicast) has been proposed to address heterogeneous bandwidth constraints through layer merging and splitting. However, this method causes that receivers subscribing to the higher layer drop down to the lower layer and hence may decrease utilization of available bandwidth after layer merging. In this paper, we proposed a multicast regrouping method considering distributive status of receivers according to loss rates. The proposed method weights receivers according to loss rates. And then it groups higher layer with receivers subscribing to lower layer have extra bandwidth and lower layer with receivers subscribing to higher layer have high loss rate. Experimental results show that receivers subscribing to higher layer can receive in high transmission rate and consequently the proposed method effectively improves utilization of available bandwidth.

• The KIPS Transactions:PartA
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• v.8A no.2
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• pp.157-166
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• 2001

A simulation package has been developed as an event-driven system that can handle the hardware configuration of STC104 and algorithm proposed in the sister paper of ‘Study on High Speed Routers(II).’After various STC104 topology of meshes, torus, and hypercubes are constructed using up to 512 switches, the performance of each topology has been analyzed under different message generation rate in terms of throughputs, latency, and packet blocking time. Modified multicast algorithms for STC104 have been proposed for STC104 after U-mesh and U-torus in order to overcome the multicasting difficulty because of the point-to-point communication method found in STC104. The performance of the multicast algorithms have been analyzed over meshes and torus configuration. Throughput gets higher in the order of mesh, torus, and hypercube. Throughput difference among topology were distinctive in the zone of high message generation rate. Latency and blocking time increased in the order of hypercube, torus, and mesh. U-mesh and U-torus of software multicast showed similar throughput, however, U-mesh peformed slightly better result. These algorithms showed eight to ten times better results compared to individual message pass for 90 destination nodes. Multi-link environment also showed better performance than single-link environment because multi-link network used the extra links for communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.931-937
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• 2015

Distributed relay scheme for wireless ad hoc multi-hop multicast network composed of low-power and low-complexity wireless devices with high density is proposed. The proposed relay scheme is shown to be better than flooding, which is the distributed relay scheme applied to ZigBee, in the outage probability and the multicast transmission rate by simulations.

• Journal of Communications and Networks
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• v.8 no.1
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• pp.116-122
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• 2006

Most of the multimedia applications require strict quality of service (QoS) guarantee during the communication between a single source and multiple destinations. This gives rise to the need for an efficient QoS multicast routing strategy. Determination of such QoS-based optimal multicast routes basically leads to a multi-objective optimization problem, which is computationally intractable in polynomial time due to the uncertainty of resources in Internet. This paper describes a network model for researching the routing problem and proposes a new multicast tree selection algorithm based on genetic algorithms to simultaneously optimize multiple QoS parameters. The paper mainly presents a QoS multicast routing algorithm based on genetic algorithm (QMRGA). The QMRGA can also optimize the network resources such as bandwidth and delay, and can converge to the optimal or near-optimal solution within few iterations, even for the networks environment with uncertain parameters. The incremental rate of computational cost can close to polynomial and is less than exponential rate. The performance measures of the QMRGA are evaluated using simulations. The simulation results show that this approach has fast convergence speed and high reliability. It can meet the real-time requirement in multimedia communication networks.

• 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 the Korea Society of Computer and Information
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• v.11 no.1 s.39
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• pp.157-165
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• 2006

This paper proposes a new output-buffered multicast ATM switch with tandem crosspoints switching fabric, named the MTCOS(Multicast Tandem Crosspoint Output-buffered Switch). The MTCOS consists of multiple simple crosspoint switch fabrics, named TCSF(Tandem Crosspoint Switch Fabric) , and concentrated output buffers for efficient multicasting. The TCSF resolves the cell delay deviation problem which the self-routing crossbar switches inherently have. Further, it offers multiple concurrent pathes from one input to multiple output ports. It also provides multi-channel switching by easy software configuration and has several desirable characteristics such as scalability, high Performance, and modularity. A shared traffic concentration and output queuing strategies of the MTCOS results in lower cell loss as well as lower cell delay time over a wide range of multicast traffic. Furthermore, it has lower hardware complexity than that of the SCOQ and Knockout multicast switch to achieve the same Knockout concentration rate as the conventional switches. It is shown that the proposed switch can be easily applied to design high performance for any multicast traffic by analytic analysis and computer simulation.

• Journal of the Korea Society of Computer and Information
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• v.13 no.6
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• pp.233-241
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• 2008

The overlay multicast that has been recently presented as an alternative for the IP multicast needs scheduling method that can apply the system resource and the network bandwidth for the many users. We propose a efficient overlay multicasting network policy for multimedia services with composite stream service topology. And in order to evaluate the ability of the proposed scheme's performance, We test the performance of multi_casting nodes with RTT values, the bandwidth attrition rate for building the network topology and MOR effects with Overcast[5] The result of simulation shows improves about $8{\sim}20%$ of performance.

• Journal of KIISE:Information Networking
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• v.35 no.3
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• pp.227-234
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• 2008

The development of wireless network technology allows high data rate seamless communication irrespective of the place and time in various emerging mobile service environment. Unlike wired networks, however, wireless networks utilize expensive limited bandwidth. MBS(Multicast Broadcast Service), which is supported by mobile WiMAX system based on IEEE802.16e, overcomes this problem using a shared downlink channel for efficiently supporting a number of users. However. the coverage and throughput of the system are significantly affected by the channel condition. In this paper we propose on MBS system employing Mobile Multi-Hop Relay(MMR) and adaptive modulation and coding(AMC) scheme. The result of NS-2 computer simulation shows that the throughput and transmission time are substantially improved by the proposed approach compared to the existing MBS system.