• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.704-711
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• 2003

Recently, the demands for real-time service and multimedia data are rapidly increasing. There are significant redundancies between header fields both within the same packet header and in consecutive packets belonging to the same packet stream. But there are many overheads in using the current UDP/IP protocol. Header compression is considered to enhance the transmission efficiency for small size of payload. By sending the static field information only once initially and by utilizing dependencies and predictability for other fields, the header size can be significantly reduced for most packets. This work describes an implementation for header compression of the headers of U/UDP protocols to reduce overhead on Ethernet network. Typical UDP/IP Header packets can be compressed down to 7 bytes and the header compression system is designed and implemented on the Linux environment. Using the designed Header compression system between a server and a client have the advantage of effective data throughput in network.

• Journal of Korea Multimedia Society
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• v.6 no.6
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• pp.1034-1045
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• 2003

In this paper, we study a multicast transport technique for multimedia services of mobile hosts in wireless network environments. To reduce packet loss during hand-off, we propose a Pre-join scheme in overlapped area and a Buffering scheme in crossover routers. To support seamless service in real time multimedia application, these scheme use an optimal path routing which was provided in remote subscription scheme and a prediction scheme of host movements which was considered overlapped area. To evaluate the peformance of our scheme, we compare Bi-direction tunneling of mobile If, Remote subscription, and MoM by using NS-2. As a result, our scheme shows better performance in network overhead, packet loss and bandwidth's use than other schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.484-493
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• 2009

For the flexible frequency utilization, cognitive radio technique has been prominently considered. The most important requirement in cognitive radio networks is to protect the communications of primary users. Spectrum sensing task by secondary users should be seriously considered in cognitive radio networks, since the spectrum sensing process makes their current quality of service worse. In this paper, we propose the channel sensing scheduling method that keeps the requirements for protecting the primary and guarantee the secondary user's quality of service as possible. The quality of service of secondary user is analyzed in terms of packet delay and loss while the protection-requirements in terms of sensing interval and sensing time predefined. In numerical analysis, we can get appropriate parameters which guarantee QoS in various environment. And simulation results show that this method can improve the performance, delay and the number of transmitted packets against consecutive sensing method.

• Journal of KIISE:Information Networking
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• v.35 no.3
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• pp.192-206
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• 2008

Multihop is the main communication style for wireless sensor networks composed of tiny sensor nodes. Until now, most applications have treated the periodic small sized sensing data. Recently, the burst traffic with the transient and continuous nature is increasingly introduced due to the advent of wireless multimedia sensor networks. Therefore, the efficient communication protocol to support this trend is required. In this paper, we propose a novel PIGAB(Packet Interval Gap based on Adaptive Backoff) protocol to efficiently transmit the burst data in multihop wireless sensor networks. The contention-based PIGAB protocol consists of the PIG(Packet Interval Gap) control algorithm in the source node and the MF(MAC-level Forwarding) algorithm in the relay node. The PIGAB is on basis of the newly proposed AB(Adaptive Backoff), CAB(Collision Avoidance Backoff), and UB(Uniform Backoff). These innovative algorithms and schemes can achieve the performance of network by adjusting the gap of every packet interval, recognizing the packet transmission of the hidden node. Through the simulations and experiments, we identify that the proposed PIGAB protocol considerably has the stable throughput and low latency in transmitting the burst data in multihop wireless sensor networks.

• Journal of the Korea Society for Simulation
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• v.19 no.4
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• pp.89-98
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• 2010

In the heterogeneous system of various wired or wireless network with IP-based backbone, the continuities of agreedon QoS for multimedia services should be guaranteed regardless of network types and terminal mobility through seamless vertical handover. This paper proposes a QoS provisioning mechanism called D-ISHO which guarantees the continuities of agreed-on QoS and seamless for multimedia services by considering both such characteristics as delay, loss rate and jitter per each service and such status as available band-width, call arrival rate and data transmission rate during the vertical handover. Simulation is done for performance analysis with the measure of handover failure rate and packet loss rate.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.6
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• pp.630-640
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• 2002

The compressed video bitstream is very sensitive to transmission errors. If we lost packet or received with errors during the transmission, not only the current frame will be corrupted, but also errors will propagate to succeeding frames. Error concealment is a data recovery technique that enables the decoder to conceal effects of transmission errors by predicting the lost or corrupted video data from the previously reconstructed error free information. Motion vection recovery and motion compensation with the estimated motion vector is a good approach to conceal the corrupted macroblock data. In this paper, we prove that it is reasonable to use the estimated motion vector to conceal the lost macroblock by providing macroblock distortion models. After we propose a new motion vector recovery algorithm based on optical flow fields, we compare its performance to those of conventional error concealment methods. The proposed algorithm has smaller computational complexity than those of conventional algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9B
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• pp.813-821
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• 2008

In recent year, several types of PON(Passive Optical Networks) have been adopted into the subscriber loops for the high speed subscriber lines to meet the needs of some applications based on the Internet and the rapid increase of the Internet users. GPON(Gigabit PON) is a typical access network technology of these PONs which adopt the DBA(Dynamic bandwidth Allocation) scheme in order to transmit upstream traffic efficiently. In this paper, we introduce the gated polling system with a two-stage queue in order to analyze the delay performance of the DBA scheme in a GPON. We use a continuous time queueing model for deriving the mean cycle time and for obtaining the mean packet delay. We give some numerical results to investigate the delay performance for the symmetric polling system with statistically identical stations.

• The KIPS Transactions:PartC
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• v.13C no.7 s.110
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• pp.803-812
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• 2006

This paper analytically evaluates the FEC(Forward Error Correction) symbol size's effect on the performance and energy consumption of 802.11 protocol with the block FEC algorithm over WSN(Wireless Sensor Network). Since the basic recovery unit of block FEC algorithms is symbols not bits, the FEC symbol size affects the packet correction rate even with the same amount of FEC check bits over a given WSN channel. Precisely, when the same amount of FEC check bits are allocated, the small-size symbols are effective over channels with frequent short bursts of propagation errors while the large ones are good at remedying the long rare bursts. To estimate the effect of the FEC symbol site, the paper at first models the WSN channel with Gilbert model based on real packet traces collected over TIP50CM sensor nodes and measures the energy consumed for encoding and decoding the RS (Reed-Solomon) code with various symbol sizes. Based on the WSN channel model and each RS code's energy expenditure, it analytically calculates the transmission efficiency and power consumption of 802.11 equipped with RS code. The computational analysis combined with real experimental data shows that the RS symbol size makes a difference of up to 4.2% in the transmission efficiency and 35% in energy consumption even with the same amount of FEC check bits.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.423-425
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• 2013

스마트 폰, 태블릿 PC와 같은 이동단말기기와 다양한 무선통신 기술의 발전으로 차세대 이동통신망은 다양한 액세스 네트워크들이 공존한다. 다양한 네트워크에서의 서비스 연속성 및 네트워크 상황에 따른 서비스 품질 저하, 그리고 EPC 망의 트래픽 과부하 현상은 여전히 문제로 남아있다. 본 논문에서는 EPC 망에서 측정된 QoS 정보에 따라 트래픽 경로 선택 기법을 제안한다. 제안한 방안을 통해 효율적인 네트워크 활용 방안과 최상의 핸드오버 방안을 제공할 수 있으며 사용자에게는 네트워크 상황에 따른 최적의 서비스를 제공할 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.1023-1031
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• 2010

With recent advances in hardware and wireless communication techniques, wireless multimedia sensor network which collects multimedia data through wireless sensor network has started to receive a lot of attentions from many researchers. Wireless multimedia sensor network requires a research of efficient compression and transmission to process the multimedia data which has large size, in the wireless sensor network that has very low network bandwidth. In this paper, we propose PIT protocol for the transmission based on the priority that classified by the DPCM compression. The PIT protocol sets different priority to the each subbands which are divided by the wavelet transform. The PIT protocol transmits the data with higher priority to guarantee the high image quality. The PIT protocol uses the characteristic of wavelet transform that the transformed image is very insensible to the data loss. In PIT protocol, each subbands of wavelet transformed image has fair weight in the compressed image to utilize the prioriy based transmission. The experiment results show that the PIT protocol improves the quality of image in spite of data loss.