• 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.

• The KIPS Transactions:PartC
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• v.18C no.4
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• pp.227-236
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• 2011

IPTV(Internet Protocol Television) is one of the typical businesses which are the convergence of Broadcast and Communication. It provides broadcasting service using IP networks. Recently, IPTV service is developed to Mobile IPTV or Open IPTV. Especially, Open IPTV uses open platform so not only service providers but also general users can provide contents to other users. Open IPTV system has many content providers, so existing security solution of IPTV cannot be adopted. In this paper, we suggest user authentication and key distribution mechanism on Open IPTV. Our proposed mechanism is based on Kerberos, so it can support distribution environment such as Open IPTV. We demonstrate that proposed mechanism can guarantee secure transmission of contents and reduce the delay of user authentication on Open IPTV system compared to other authentication mechanisms. We also compare our proposal and other mechanisms in various aspects, and analyze efficiency and safety of proposed mechanism. As a result, we insist that this mechanism satisfies the security requirements for IPTV.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.11
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• pp.403-408
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• 2014

In the Internet of Things(IoT) era, many of the things or objects that enclose our environments are able to associate with those things on the Internet. To construct IoT systems, it needs to consider a component for acquiring and aggregating of sensory data via things with sensors and instruments, which is connected by diverse networks, in IoT environment. An IoT system is intrinsically distributed in a variety of ways. In addition, to manage an IoT system efficiently, interoperability is needed to meet requirements while the IoT system is designed to deliver data among its applications. In this paper, a reference architecture based on asynchronous messaging is defined and used for designing an IoT system. To apply the architecture, we discuss how to manage data streams with real-time characteristics and make a prototype based on pipe-and-filter to produce and consume them by a pub/sub messaging system NaradaBrokering.

• Journal of KIISE:Databases
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• v.28 no.4
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• pp.715-722
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• 2001

Mobile computing has become a reality thank to the convergence of two technologies :powerful portable computers and the wireless networks. The restrictions of wireless network such as bandwidth and energy limitations make data broadcasting an attractive data communication method. This paper addresses the clustering of wireless broadcast data for multipoint queries. By effective clustering of broadcast data the mobile client can access the data on the air in short latency In the paper we define the data affinity and segment affinity measures. The data affinity is the degree that two data objects are accessed by queries, and the segment affinity is the degree that two sets of data (i.e segments) are accessed by queries Our method clusters data objects based on data and segment affinity measures we show that the performance of our method is scarcely infuenced by the growth of the number of queries.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1384-1390
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• 2008

The TCP protocol is originally designed for wired network, however it performs very poor in wireless network due to different nature of wireless network from wired networks. In terms of TCP performance improvement in wireless Ad-hoc network, many researches show that small congestion window size of TCP connection can improve TCP performance. We propose a new TCP algorithm to improve TCP performance in wireless Ad-hoc network. The basic idea of our approach is that TCP receiver estimates the optimum window size and then sets congestion window limit of TCP sender to an optimum value by using the advertised window field in TCP ACK packet. From extensive computer simulation, the proposed algorithm shows superior performance than traditional TCP protocols in terms of packet delivery ratio and packet loss.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.5
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• pp.870-878
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• 2008

The level of security of most sensor nodes that comprise the sensor networks is low, but because of the low computing power and small storage capacity, it is even very difficult to apply a security algorithm efficiently to the sensor nodes. Therefore, preventing the join of an illegal node to a sensor network is impossible, and the transmitting information is easily exposed and overheard when the transmitting algorithm of the sensor node is hewn. In this paper, we propose a group key management scheme for the sensor network using polar coordinates, so that the sensor nodes can deliver information securely inside a cluster and any illegal node is prevented from joining to the cluster where a sensor network is composed of many clusters. In the proposed scheme, all of the sensor nodes in a cluster set up the authentication keys based on the pivot value provided by the CH. The intensive simulations show that the proposed scheme outperforms the pair-wise scheme in terms of the secure key management and the prevention of the illegal nodes joining to the network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.12
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• pp.2301-2306
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• 2008

SIP(Session Initiation Protocol) has become an universal standard for multimedia communications for both wired and wireless networks since it has been adopted as a standard protocol for IMS platform in 3GPP standardization organization at November 2000. In this paper, we design and implement a SIP-based softphone client program which provides telephony service between internet users and a call center equipped with VoIP gateway. A softphone client based on PC-to-phone connection should guarantee to provide interoperability with various VoIP gateways and higher portability to be able to operate on different PC environments. The softphone client program in this paper has been developed with SIP 2.0 standard protocol to support interoperability and with JAIN SIP and JMF package to achieve higher portability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.6
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• pp.1026-1031
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• 2008

Nowdays, homes and small businesses rely more and more PON(Passive Optical Networks) for financial transactions, private communications and even telemedicine. Thus, encryption for these data transactions is very essential due to the multicast nature of the PON In this parer, we presented our implementation of a counter mode AES based on Virtex4 FPGA. Our design exploits three advanced features; 1) Composite field arithmetic SubByte, 2) efficient MixColumn transformation 3) and on-the-fly key-scheduling for fully pipelined architecture. By pipeling the composite field implementation of the S-box, the area cost is reduced to average 17 percent. By designing the on-the-fly key-scheduling, we implemented an efficient key-expander module which is specialized for a pipelined architecture.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.2
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• pp.254-259
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• 2008

Mesh WLANs, which consist of wireless mesh routers connecting each other in a mesh topology and self-operate after their autoconfiguration, have several advantages in convenience, swiftness and flexibility of deployment and operation over existing WLANs the expansions of which are done by connecting the APs with wires. However, many technical issues still remain to be solved. Among them, network performance degradations due to the interference between the adjacent hops in multi-hop mesh WLANs, and the reusability of the existing wireless network protocols are critical problems to be answered. This work evaluates the VoIP support performance of IEEE 802.11a/g-based mesh WLANs with multiple wireless interfaces with simulations. The results show that there exit an unfairness in VoIP packet delay performances among mobile routers located at different hops, and that although the capacity of the admitted calls can be increased by increasing the size of voice packet payload it is far less than the expected one. This suggests that the existing 802.11 MAC protocols have their limitation when applied in mesh networks and their enhancement or even a newer one nay be required.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.3
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• pp.534-540
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• 2008

The adaptive learning circuit is designed on the basis of modeling of MFSFET (Metal-Ferroelectric-Semiconductor FET) and the numerical results is analyzed. The output frequency of the adaptive learning circuit is inversely proportional to the source-drain resistance of MFSFET and the capacitance of the circuit. The saturated drain current with input pulse number is analogous to the ferroelectric polarization reversal. It indicates that the ferroelectric polarization plays an important role in the drain current control of MFSFET. The output frequency modulation of the adaptive learning circuit is investigated by analyzing the source-drain resistance of MFSFET as functions of input pulse numbers in the adaptive learning circuit and the dimensionality factor of the ferroelectric thin film. From the results, adaptive learning characteristics which means a gradual frequency change of output pulse with the progress of input pulse, are confirmed. Consequently it is shown that our circuit can be used effectively in the neuron synapses of neural networks.