• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.277-282
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• 2002

In general, requirements for QoS are different according to the type of services in wire-line and wireless ATM networks, and real-time video service is more sensitive to cell transmission delay than to cell loss. Existing handoff schemes emphasizing prevention of cell loss had limitations in cell transmission delay to satisfy QoS. In this paper, a novel scheme to transmit ATM cells with low CLP(when CLP = 0) prior to others and discarding cells with high CLP(when CLF = 1) in ATM cell header among cells to be forwarded to new base station during handoffs in real-time VBR service is proposed. The proposed scheme is proven to be suitable for the satisfaction of QoS of real-time VBR service and appropriate for fast handoffs by giving high CLP value to less meaningful MPEG frames through simulations.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.4
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• pp.14-19
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• 2005

In general, cell transmission delay is more sensitive for real time video service rather than cell losses in a wireless ATM network. Existing handoff schemes, which are emphasizing the prevention of cell losses, have limitations in cell transmission delay to satisfy QoS. In this paper, we propose a scheme to minimize transmission delay generated during the handoff and to maintain the sequence of cells. Transmission delay can be reduced by transmitting ATM cells with low CLP(i.e., CLP=0) prior to others and by discarding cells with high CLP(i.e., CLP= 1). The simulation results show that the proposed scheme is suitable for delay sensitive real time VBR service as well as fast handoff by giving high CLP to less meaningful MPEG frames.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1910-1916
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• 1999

This paper suggested to solve ATM switch performance and service rate which was input buffer managed scheme in ATM network with burst traffic characteristics, For this purpose, ATM multiplexer is prepared before sending for handling burst random input traffic to multiplex and then sort based on cell inter-arrival time and cell processing due time which had been marked after that. The server looks for cell header with the most shortest due time and sends it, thus it is satisfied that real time traffic for instance CBR and rt-VBR was guaranteed cell processing time to send fast than non real time traffic. For analysis of ATM switch performance with cell processing due time and priority, each output port has divided into four different virtual buffer and each buffer has assigned different cell inter-arrival time and processing due time according to ATM Forum for example CBT/rt-VBR, nrt-VBR, ABR and UBR and showed it’s optimal service parameters then analyzed service rate behaviors according to each traffic characteristics.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.91-94
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• 1998

ATM technology is reaching a certain level of maturity that allow for its deployment in local as well as in wide area networks. Concurrently, audiovisual applications are foreseen as one of the major users of such broadband networks. We present in this paper requriement of real-time multimedia service on B-ISDN networks and simulating the transport of MPEG-2 encoded multimedia data over ATM networks using CBR, VBR, ABR of ATM Traffic Service. We compare each delay time considering network performance and propose need for real-time multimedia service.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.3
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• pp.54-64
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• 1998

In this paper, a cell scheduling algorithm is proposed to satisfy the service requirements of CBR, VBR traffics. Particularly, inthe proposed algorithm an ABR traffic which is not included in the conventional cell schedulaing algorithm is treated as one kind of traffic types. The algorithm of RT-VBR and NRT-VBR traffic such that the service requrements of RT-VBR and NRT-VBR traffic are satisfied. The proposed algorithm dynamically schedules cells in a real time by considerin the current traffic conditions. The simulation of the proposed algorithms such as WRR or DWRR in terms of the mean delay time and the maximum queue length.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1160-1168
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• 2000

This paper presents a real-time integrated traffic management (RITM) scheme that can effectively manage variable bit rate (VBR) and available bit rate (ABR) traffics having unpredictable characteristics in asynchronous transfer mode (ATM) networks. An unique feature of this scheme is that it has a special ATM cell control block which makes it possible to monitor bursty traffics in real-time so that the delay incurred to measure cell arrival rate is minimized. Additionally, the proposed scheme intends to dynamically reassign the leftover network resources to VBR/ABR connections without any deterioration in quality of service (QoS) of the existing connections. The RITM scheme has been verified to reliably monitor incoming traffics and to efficiently manage network resources by computer simulations. The capability of managing the incoming ATM traffics in real-time helps determine an optimal acceptable number of user connections for a given network condition. We can use this value as a threshold to protect the network from being congested and to find out a cost-effective buffer design method.

• The Transactions of the Korea Information Processing Society
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• v.7 no.9
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• pp.2940-2947
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• 2000

In the wireless ATM networks, a Medium Access Control (MAC) protocol is required to support an integrated mix of multimedia traffic services. The MAC protocol should be designed in a way that the limited wireless bandwidth can be efficiently utilized maximizing the Quality of Service (QoS) guarantees for various traffic service classes. In this paper, a Dynamic Resource Allocation-based MAC protocol, which satisfies QoS of each traffic service class in the wireless ATM environment, is proposed. The proposed MAC protocol adopts the dynamic channel allocation schemes for a mix of different traffic service classes. The suggested MAC protocol is designed to provide the QoS guarantees for Constant Bit Rate (CBR) or real-time Variable Bit Rate (VBR) traffic through fixed or dynamic reservation. For Available Bit Rate (ABH) traffic, which has the lowest priority among the traffic classes, large improvement in delay by reserving the minimum bandwidth is shown. And for real-time VBR traffic, increase in throughput of transmission is demonstrated because of bandwidth, which is allocated through contention at the initial phase and without contention thereafter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1249-1259
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• 1998

This paper proposes an efficient channel assignment method for real-time service in the IEEE 802.11 Wireless LAN system, and analyzes the supportability to real-time service and the channel utilzation of that through computer simulations. The improved MAC(Medium Access Control) protocol employing the proposed channel assignment method achieved good throughput over contention period as well as contention-free period by making real-time terminals transmit the information about their desiring value before starts of data transmissions. For performance evaluation of the proposed method, a simulation analyzing the variation of allocated bandwidths to terminals using real-time service and their buffer sizes wasexecuted. Real-time data traffics was modeled s 7-stae transition VBR sources, and asynchronous data traffics modeled as Poisson processes. In the simulation, the proposed method showed smaller variation of the bandwidth of each terminal and samller buffer size than the existing method, and also recorded good throughput over contention period.

• The KIPS Transactions:PartC
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• v.8C no.6
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• pp.805-814
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• 2001

In this paper, we propose a new scheduling algorithm that guarantees the delay property of real-time traffic, not considered in previous DWRR(Dynamic Weighted Round Robin) algorithm and also transmits non-real-time traffic efficiently. The proposed scheduling algorithm is a variation of DWRR algorithm to guarantee the delay property of real-time traffic by adding cell transmission method based on delay priority. It also uses the threshold to prevent the cell loss of non-real-time traffic due to cell transmission method based on delay priority. Proposed scheduling algorithm may increase some complexity over conventional DWRR scheme because of cell transmission method based on delay priority. However, the consideration of delay priority can minimize cell delay and require less size of temporary buffer. Also, the results of our performance study shows that the proposed scheduling algorithm has better performance than conventional DWRR scheme due to reliable ABR service and congestion avoidance capacity.

• Journal of Korea Multimedia Society
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• v.15 no.6
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• pp.814-826
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• 2012

In this paper, we propose scheduling algorithms for transporting variable-bit-rate video stream using playback buffer level of the clients over wireless communication networks. The proposed algorithms attempt to maximize the utilization of limited bandwidth between the central video server and the clients over a mobile network. Since a video server may serve several video request at the same time, it is important to allocate and utilize network bandwidth to serve them fairly and efficiently. In order to improve the quality of service and real-time performance of individual video playback, the video server attempts to allocate temporarily more network bandwidth to serve a video request with the lower buffer level preferentially. The simulation results prove the fair service and load balancing among the mobile concurrent clients with different buffer levels and hence maximizing the number of frames that are transported successfully to the client prior to their playback times.