• Proceedings of the Korea Information Processing Society Conference
• /
• 2009.11a
• /
• pp.207-208
• /
• 2009

Peer-to-Peer (P2P) network has great potential on utilizing the network while reducing the server loads. Video on Demand (VoD) has become widely used since we can watch contents we like without having to download the overall file first. The mobile users may not need high quality of video; they only need good enough quality that can be played in the limited resource of physical device and network. So does with the devices with very limited network bandwidth. These issues emerge an idea of allowing Free-Rider in the P2P VoD system, where those low performance devices will only optimize the network utilization, affecting none to the performance of main system.

• The KIPS Transactions:PartC
• /
• v.15C no.5
• /
• pp.399-408
• /
• 2008

Mobile WiMAX provides wireless broadband services for data communication based on IP protocol. The limitation of physical bandwidth in the radio links may cause performance degradation in providing wireless broadband services in WIMAX. To enhance the efficiency of the radio link utilization, Payload Header Suppression (PHS) is defined as an optional header compression mechanism for mobile WiMAX. It has, however, a very limited compression capability since it has very restrictive compression fields. In this paper, hence, we assumed the application of Robust Header Compression (ROHC), a header compression scheme proposed for links characterized by high bit error ratios, long round-trip times (RTT), and scarce resource, to Mobile WiMAX, and studied its performance. Previous studies on ROHC performance merely focused on the impact of high bit error rate. However, bit error is virtually transparent to ROHC in the wireless systems like WiMAX, since the MAC provides the bit error checking function. In order to evaluate the performance of ROHC in the Mobile WiMAX environments, therefore, we evaluated the performance of ROHC with respect to the packet losses instead of bit error. We investigated the impact of the ROHC parameters that are recommended for the implementation in the ROHC and compared the performance of ROHC with PHS.

• The KIPS Transactions:PartC
• /
• v.16C no.5
• /
• pp.661-668
• /
• 2009

The Extended real-time Polling Service (ErtPS) is proposed tosupport QoS of VoIP service with silence suppression which generates variable size data packets in IEEE 802.16e systems. If the silence is suppressed, VoIP should support Comfort Noise Generation (CNG) which generates comfort noise for receiver's auditory sense to notify the status of connection to the user. CNG mode in silent-period generates a data with lower bit rate at long packet transmission intervals in comparison with talk-spurt. Therefore, if the ErtPS, which is designed to support service flows that generate data packets on a periodic basis, is applied to silent-period, resources of the uplink are used inefficiently. In this paper, we proposed the Improved ErtPS algorithm for efficient resource utilization of the silent-period in VoIP traffic supporting CNG. In the proposed algorithm, the base station allocates bandwidth depending on the status of voice at the appropriate interval by havingthe user inform the changes of voice status. The Improved ErtPS utilizes the Cannel Quality Information Channel (CQICH) which is an uplink subchannel for delivering quality information of channel to the base station on a periodic basis in 802.16e systems. We evaluated the performance of proposed algorithm using OPNET simulator. We validated that proposed algorithm improves the bandwidth utilization of the uplink and packet transmission latency

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.05a
• /
• pp.183-186
• /
• 2008

In ubiquitous GIS system, the spatial information could be updated and utilied by mobile terminals. Spatial information stored in mobile terminals should be able to synchronize to the server. However, in mobile environment, there are some limitations in synchronization service due to the limited bandwidth. The ActMAP system, that was developed to consider of mobile environment, has suggested a partial update protocal for synchronization in order to solve the narrow bandwidth problem. But it is still has a problem that it does not consider two-way synchronization between a server and a mobile terminal. This paper suggests a two-way synchronization protocol between a server and mobile terminals. It, therefore, is inclined to supporting updated and utilization of spatial information using mobile terminals.

• Journal of KIISE
• /
• v.44 no.2
• /
• pp.124-131
• /
• 2017

The emerging next-generation manycore processors for high-performance computing are equipped with a high-bandwidth on-package memory along with the traditional host memory. The Multi-Channel DRAM (MCDRAM), for example, is the on-package memory of the Intel Xeon Phi Knights Landing (KNL) processor, and theoretically provides a four-times-higher bandwidth than the conventional DDR4 memory. In this paper, we suggest a mechanism to exploit MCDRAM for improving the performance of MPI intra-node communication. The experiment results show that the MPI intra-node communication performance can be improved by up to 272 % compared with the case where the DDR4 is utilized. Moreover, we analyze not only the performance impact of different MCDRAM-utilization mechanisms, but also that of core affinity for processes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.7
• /
• pp.766-773
• /
• 2007

Conventional wireless sensor network(WSN) has limited power and bandwidth. In order to develop multimedia sensor technology, high data rate communication systems are required. Cooperative communication system can help to decrease power consumption through spatial diversity. In cooperative transmission, one partner node assists one sensor node to transmit their data to destination. Instead of using M partners for M sensor nodes, we propose 1 partner for M sensor nodes. Proposed protocol offers similar diversity order as conventional one with much less bandwidth and hardware. It is able to almost reduce scattered nodes interference using orthogonal sub-carriers. In addition, we examined a power allocation between sensor nodes and relay that optimize the system performance.

• Journal of KIISE:Information Networking
• /
• v.36 no.6
• /
• pp.481-491
• /
• 2009

In this paper, we proposed a hybrid P2P overlay structure for live media streaming. The proposed structure consists of the mesh overlay organized by peers according to the geographical proximity and similar bandwidth range and the tree overlay formed by the peers for which the stability of participation is approved. The proposed scheme enhances the robustness of tree overlay and the long delay of mesh overlay by intelligently combining the utilization of the tree overlay and the mesh overlay. Furthermore, the peers with a large up-link bandwidth are located near to the media source peer. Therefore, it reduces the height of tree, and as a result, the stream transmission delay. Through simulation, we evaluated the performance of the proposed scheme in terms of scalability and quality of services.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37B no.9
• /
• pp.795-805
• /
• 2012

This paper proposes an algorithm and a hardware architecture for a broadcast communication which has the worst bottleneck among multiprocessor using distributed memory architectures. In conventional system, The pipelined broadcast algorithm is an algorithm which takes advantage of maximum bandwidth of communication bus. But unnecessary synchronization process are repeated, because the pipelined broadcast sends the data divided into many parts. In this paper, the MPI unit for pipeline chain algorithm based on circuit switching removing the redundancy of synchronization process was designed, the proposed architecture was evaluated by modeling it with systemC. Consequently, the performance of the proposed architecture was highly improved for broadcast communication up to 3.3 times that of systems using conventional pipelined broadcast algorithm, it can almost take advantage of the maximum bandwidth of transmission bus. Then, it was implemented with VerilogHDL, synthesized with TSMC 0.18um library and implemented into a chip. The area of synthesis results occupied 4,700 gates(2 input NAND gate) and utilization of total area is 2.4%. The proposed architecture achieves improvement in total performance of MPSoC occupying relatively small area.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.6
• /
• pp.245-250
• /
• 2014

This paper presents the broadband printed sleeve-monopole antenna implementing the sleeve monopole structure in the form of PCB. In the proposed antenna, the antenna performance was improved by the diameter variation of the radiator, the length variation of the sleeve, and the variation of the diameter of the sleeve conductor. HFSS simulator of ANSYS corp. was used in order to confirm the antenna parameter characteristic. According to the simulation results, the VSWR was less than 2 for the range of 2.12GHz~3.18GHz. The frequency bandwidth is 1.08GHz. The frequency range of the actual fabricated antenna was 2.0GHz~3.55GHz, the frequency bandwidth is 1.55GHz. The maximum gain was 1.64dBi. The proposed antenna was $56{\times}5{\times}1.6mm$ in size. The utilization possibility of the broadband printed sleeve-monopole antenna could be confirmed according to compare and analyze the simulation and measurement data.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.11
• /
• pp.2553-2562
• /
• 2013

It is difficult for TCP congestion control algorithm to ensure the bandwidth and delay bound required for media streaming services in broadband wireless network environments. In this paper, we propose the COIN TCP (COncave INcrease TCP) scheme for providing a high-quality media streaming services. The COIN TCP concavely increases the congestion window size by adjusting the increment rate of congestion window, that is inversely proportional to the amount of data accumulated in the router queue. As a result, our scheme can quickly occupy the available bandwidth and prevent the heavy congestion. It also improves the link utilization by adjusting the decrement rate of congestion window according to the packet loss rate with the random loss. Through the simulation results, we prove that our scheme improves the total throughput in broadband wireless network.