• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7B
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• pp.455-462
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• 2007

The GTS(Guaranteed Time Slot) of IEEE802.15.4 standard, which is the contention free access mechanism, has some problems such as the limited number of deployed devices, the low channel utilization and the service confirm delay. The proposed Cyclic-CFA(Contention Free Access) scheme is a modified polling algorithm that allows a large number of devices to be served Contention Free Access without polling packets. The Cyclic-CFA scheme improves the channel utilization dramatically and also reduces service delay time.

• Journal of Internet Computing and Services
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• v.12 no.4
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• pp.45-50
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• 2011

In this paper, the encoding time delay of FH/TDD(Frequency Hopping/Time Division Duplex) based Motion JPEG image compression CODEC is analyzed for radio video transmissions of multi-camera systems in a vehicle. And, Synchronized connection of minimum channel collision is designed with synchronized shift and access according to channel status for Motion JPEG based FH/TDD multiple access.

• Journal of the Korea Society of Computer and Information
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• v.20 no.9
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• pp.1-10
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• 2015

In this paper, we propose a new variable latency L1 data cache architecture for multi-core processors. Our proposed architecture extends the traditional variable latency cache to be geared toward the multi-core processors. We added a specialized data structure for recording the latency of the L1 data cache. Depending on the added latency to the L1 data cache, the value stored to the data structure is determined. It also tracks the remaining cycles of the L1 data cache which notifies data arrival to the reservation station in the core. As in the variable latency cache of the single-core architecture, our proposed architecture flexibly extends the cache access cycles considering process variation. The proposed cache architecture can reduce yield losses incurred by L1 cache access time failures to nearly 0%. Moreover, we quantitatively evaluate performance, power, energy consumption, power-delay product, and energy-delay product when increasing the number of cache access cycles.

• IE interfaces
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• v.17 no.3
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• pp.294-304
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• 2004

In the IS-95 packet service system, the radio channels are generally classified into the dedicated and common traffic channels. In this paper, the performance of the common traffic channel access method is evaluated using simulation. The simulation results are compared with those of random access method. Simulation results show that the capacity can be increased up to 25% by applying the proposed common channel access method. The delay problem and variance of BER are also discussed.

• IEMEK Journal of Embedded Systems and Applications
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• v.15 no.6
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• pp.299-305
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• 2020

We have developed a scheduler that additionally consider network performance by extending the Kubernetes developed to manage lots of containers in cloud computing nodes. The network delay adapt characteristics of the compute nodes were learned during server operation and the learned results were utilized to develop placement algorithm by considering the existing measurement units, CPU, memory, and volume together, and it was confirmed that the low delay network service was provided through placement algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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• pp.2509-2528
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• 2012

Time division multiple access (TDMA) is a widely used media access control (MAC) technique that can provide collision-free and reliable communications, save energy and bound the delay of packets. In TDMA, energy saving is usually achieved by switching the nodes' radio off when such nodes are not engaged. However, the frequent switching of the radio's state not only wastes energy, but also increases end-to-end delay. To achieve high energy efficiency and low delay, as well as to further minimize the number of time slots, a multi-objective TDMA scheduling problem for industrial wireless mesh networks is presented. A hybrid algorithm that combines genetic algorithm (GA) and simulated annealing (SA) algorithm is then proposed to solve the TDMA scheduling problem effectively. A number of critical techniques are also adopted to reduce energy consumption and to shorten end-to-end delay further. Simulation results with different kinds of networks demonstrate that the proposed algorithm outperforms traditional scheduling algorithms in terms of addressing the problems of energy consumption and end-to-end delay, thus satisfying the demands of industrial wireless mesh networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.7
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• pp.641-655
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• 1992

In this paper, the performance of the various multiple accesstechniques for the mobile computer network has been studied in the consideration of the characteristics. Of the mobile communication channel. In the case of the hidden node occurring, it could be seen that the performance of the code division multiple access(CDMA) technique. With simultaneous access function is better than that of the other packet access methods such as carrier sensed multiple access(CAMA). Busy tone mulitiple access(BTMA)and idle signal muitiple access(ISMA) in the view of the throuhtput and mean delay time. Also it has been shown that the performance of the CDMA method is superior to that of other packet access techniques such as multiple access(CSMA).etc when the fading effect or impulsive noise exists in the mobile channel. Especially in the case of the distributed mobile network. It has been shown that the receiver-transmitter based CDMA method using the characteristics of CDMA effectively has better throughput and less mean delay time than the commontransmitter based CDMA technique.

• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.402-409
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• 2014

Wireless local area network (WLAN) is a widely used wireless access method due to its easy usability and excellent performance. However, its performance degrades significantly as the number of users increases. In busy train stations, where the number of WLAN users are large and, more importantly the number of simultaneous packet transmission attempts is extremely large due to the time synchronization upon train arrival, the packet transmission delay problem is very severe and almost impossible for WLAN stations to initiate communication with WLAN networks. In this paper, a novel distributed WLAN access scheme for efficient WLAN communication in busy train stations is proposed. Using the proposed scheme, WLAN access delay can be significantly reduced under highly congested traffic environments. Therefore, a significant performance enhancement for the WLAN performance used in the Communication Based Train Control (CBTC) can be achieved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.6
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• pp.778-785
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• 2020

Wireless mesh networks consist of mesh clients, mesh routers and mesh access points. The mesh router connects wireless network services to the mesh client, and the mesh access point connects to the backbone network using a wired link and provides Internet access to the mesh client. In this paper, a limited number of mesh routers and mesh access points are used to propose optimization algorithms for network design for wireless mesh networks. The optimization algorithm in this paper has been applied with a sub-subscription algorithm, which is one of the meta-heuristic methods, and is designed to minimize the transmission delay for the placement of mesh routers and mesh access points, and produce optimal results within a reasonable time. The proposed algorithm was evaluated in terms of transmission delay and time to perform the algorithm for the placement of mesh routers and mesh access points, and the performance evaluation results showed superior performance compared to the previous meta-heuristic methods.

• Journal of Internet Computing and Services
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• v.9 no.5
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• pp.141-151
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• 2008

In the paper, we analyze the performance of random access channels in multi-service multi-user OFDMA systems. The resource of the random access channels in OFDMA systems are available sub-channels and PN-codes. For given available sub-channels and PN-codes,' we analyze the performance of the random access channels of OFDMA systems in terms of the access success probability, the blocking probability, the access delay and the throughput per each service class. Further, we find the feasible region of the access probability of each service class in which the allowable minimum access success probability, the allowable maximum blocking probability and the allowable maximum access delay are satisfied. The results also can be used to find proper region of the access probabilities of each service class for differentiated quality of service(QoS)s, and for the system operations in multi-service multi-user OFDMA systems.