• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.92-98
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• 2007

We propose the schemes for the dynamic channel allocation (DCA) in multi-cell OFDMA systems to avoid co-channel interference (CCI) without the additional complexity. The allocatable subcarriers areas, which is designed to avoid CCI among cells, are determined for each cell. Each cell allocates the subcarriers within the allocatable subcarriers area of the cell independently. We consider the trade off between the reduced frequency selection diversity and the amount of CCI on a subcarrier by the determination of allocatable subcarriers area. Hence, the equal allocation bound scheme for the high selectivity channel and the flexible allocation bound scheme for the low selectivity channel are proposed. Through the numerical results, it is confirmed that the proposed schemes have better performance in the aspects of the number of overlapping allocated subcarriers, the capacity and the outage probability compared to the case which does not determined the allocatable subcarriers area.

• The KIPS Transactions:PartC
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• v.14C no.4
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• pp.349-358
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• 2007

Ethernet Passive Optical Network(EPON), which is one of PON technologies for realizing FTTx(Fiber-To-The-Curb/Home/Office), can cost-effectively construct optical access networks. In addition, EPON can provide high transmission rate up to 10Gbps and it is compatible with existing customer devices equipped with Ethernet card. To effectively control frame transmission from ONUs to OLT EPON can use Multi-Point Control Protocol(MPCP) with additional control functions in addition to Media Access Control(MAC) protocol function. For EPON, many researches on intra- and inter-ONU scheduling algorithms have been performed. Among the inter-ONU scheduling algorithms, IPS(Interleaved Polling with Stop) based on polling scheme is efficient because OLT assigns available time portion to each ONU given the request information from all ONUs. Since the IPS needs an idle time period on uplink between two consecutive frame transmission periods, it wastes time without frame transmissions. In this paper, we propose a dynamic bandwidth allocation algorithm to increase the channel utilization on uplink and evaluate its performance using simulations. The simulation results show that the proposed Two-phase Cycle Danamic Bandwidth Allocation(TCDBA) algorithm improves the throughput about 15%, compared with the IPS and Fast Gate Dynamic Bandwidth Allocation(FGDBA). Also, the average transmission time of the proposed algorithm is lower than those of other schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.608-616
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• 2007

OFDM Systems for multi-user use adaptive modulation and ending (AMC) which is a method that selects suitable modulation order and code rate depending on channel state of each user. Using AMC, OFDM system can provide high quality and reliable communication. Base station using AMC scheme requires downlink channel information of each terminal to operate optimality. However, under practical system environment, it is unsuitable to transmit all channel information because uplink bandwidth of the system is limited. In this paper, we propose a flexible block-wise loading (FBL) algorithm combined with a novel CQI feedback scheme with reduced number of required bits to optimize the performance of AMC system. Proposed algorithm allocates sub-carrier groups dynamically to improve the sector throughput and outage probability performance.

• Journal of Internet Computing and Services
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• v.3 no.2
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• pp.15-26
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• 2002

Since multimedia data such as video and audio data are displayed within a certain time constraint, their computation and manipulation should be handled under limited condition. Traditional real-time scheduling algorithms could net be directly applicable, because they are not suitable for multimedia scheduling applications which support many clients at the same time. Rate Regulating Proportional Share Scheduling Algorithm is a scheduling algorithm considered the time constraint of the multimedia data. This scheduling algorithm uses a rate regulator which prevents tasks from receiving more resource than its share in a given period. But this algorithm loses fairness, and does not show graceful degradation of performance under overloaded situation, This paper proposes a new modified algorithm. namely Modified Proportional Share Scheduling Algorithm considering the characteristics of multimedia data such as its continuity and time dependency, Proposed scheduling algorithm shows graceful degradation of performance in overloaded situation and the reduction in the number of context switching, Furthermore, a new evaluation method is proposed which can evaluate the flexibility of scheduling algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.59-65
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• 2008

In this paper, a new adaptive resource allocation scheme is proposed in orthogonal frequency-division multiple access(OFDMA) systems with rate proportionality constraints. The problem of maximizing the overall system capacity with constraints on bit error rate, total transmission power and rate-proportionality for user requiring different classes of service is formulated. Since the optimal solution to the constrained fairness problem is extremely complex to obtain, a low-complexity suboptimal algorithm that separates subchannel allocation and power allocation is proposed. Firstly, the number of subchannels to be assigned to each user is determined based on the users' average signal-to-noise ratio and rate-proportion. Subchannels are subsequently distributed according to the modified max-min criterion. Lastly, based on the subchannel allocation, the optimal power allocation by solving the Language dual problem is proposed. Additionally, in order to reduce the computational complexity, iterative rate proportionality tracking algorithm is proposed for maximizing the capacity together with maintaining the rate proportionality constraint.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.229-235
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• 2010

The Orthogonal Frequency Division Multiplexing(OFDM) has been strongly recommended as a transmission technique in order to satisfy requests of high speed and high quality multimedia information. This paper considers resource allocation algorithm which supports the user Quality of Service(QoS) for multi-user OFDM system with simple CSI (Channel State Information) structure. After users eligible for services and the number of subcarrier are determined by minimum request data rate and average channel gain, subcarriers are allocated to increase total transmission rates. Although ideal CSI is not reported to base station, compared to conventional algorithm, we have obtained better result with simple CSI structure.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.412-414
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• 2003

무선 이동망에서 점점 증가하는 멀티미디어 트래픽의 QoS(Quality of Service)를 위해서는 충분한 자원이 제공되어야 한다. 하지만 무선망에서의 자원은 한정적이므로 이를 효율적으로 활용해야 멀티미디어 트래픽에 대한 QoS 보장이 가능하다. 이 논문에서는 무선망에서의 멀티미디어 트래픽에 대한 QoS 보장 알고리즘을 제안하였다. 제안된 알고리즘은 이동단말이 위치한 주위 셀의 자원들을 미리 예약하는 방식을 기반으로 하는 admission control 방법이다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.3
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• pp.165-173
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• 2007

In this paper, we propose a new minimum resources allocation algorithm for optimal design automation. In the proposed algorithm, the operation are allocated to functional units so that the number of interconnection wires between functional units can be minimized. The registers are allocated to the maximal clusters generated by the minimal cluster partitioning algorithm. Finally, the interconnection is minimized by removing the duplicated inputs of multiplexers and exchanging the inputs across multiplexers. The efficiency of the proposed allocation algorithm is shown by experiments using benchmark examples.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4A
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• pp.344-350
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• 2007

Start after striking space key 2 times. Lately, a lot of researches have been done on the resource allocation for multiuser OFDM(Orthogonal Frequency Division Multiplexing) systems due to its spectral efficiency for high-rate multimedia data services. For multimedia services in which every user is guaranteed to have minimum required bit rate and bit error probability, it is critical to utilize the limited resources efficiently to improve the performance of the system. The introduced allocation method improves spectral efficiency to use the left subcarriers in Zhang's algorithm. By using this method, the system can provide services to more users constantly, except for a bit increasing complexity and memory for deciding the left subcarriers and reallocating the subcarriers.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.73-75
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• 2004

그리드 컴퓨팅의 기본 개념은 여러 대의 저 성능 컴퓨터 자원을 통합하여 고성능 컴퓨팅 환경을 구축하는 것이다. 이런 환경을 관리하기 위해서는 요청된 작업에 대해 자원 관리 시스템의 효율적인 자원 탈당 기능이 중요하다. 본 논문에서는 효과적인 자원의 선택을 위해 CPU의 종합적인 성능을 평가하는 UC 단위 모델을 제안하고, 제안된 모델을 기준으로 자원관리 시스템에서 저 성능 컴퓨터 자원을 효율적으로 할당 할 수 있도록 저 성능 자원 우선 알고리즘을 제안하며, 이를 이용한 에이전트 기반 자원관리 시스템을 구현한다.