• Journal of the Korean Operations Research and Management Science Society
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• v.24 no.2
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• pp.31-39
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• 1999

A new approximation method for finding the steady-state probabilities of the number of customers present in queueing systems with Poisson arrivals and two servers with different deterministic service times with infinite waiting room capacity is developed. The major assumption made for the approximation is that the residual service times of the servers have mutually independent uniform distributions with densities equal to the reciprocals of the respective service times. The method reflects the heterogeneity of the servers only through the ratio of their service times, irrespective of the actual magnitudes and difference. The transition probability matrix is established and the steady-state probabilities are found for a variety of traffic intensities and ratios of the two service times; also the mean number of customers present in the system and in the queue, and server utilizations are found and tabulated. The method was validated by simulation and turned out to be very sharp.

• Journal of Korean Institute of Industrial Engineers
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• v.32 no.4
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• pp.369-372
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• 2006

Suppose that a customer arrives at the GI/M/1/K queueing system when there are customers in the system, $n,m{\geq}0,\;n+m{\leq}K$. Sooner or later, the number of customers in the system will reach . In this paper, we present the Laplace transform of the remaining interarrival time upon reaching level, for the first time, since a customer arrived when there are customers in the system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2B
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• pp.146-153
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• 2006

It is required to have researches on efficient resource allocation schemes in an integrated voice and data CDMA system with the spreading of high-speed wireless internets. In this paper, we proposed a efficient resouce allocation scheme for providing a high speed data service in an integrated CDMA system. In an integrated voice/data CDMA system, resources for voice users are allocated with high priority and residual resources are allocated to the data service. In this case, it is necessary to use a resource allocation scheme for minimizing interference. In this paper, we first explain about a interference minimizing method and define QoS requirements. Based on the method, we proposed a efficient resource allocation scheme which satisfy the QoS requirements. The proposed scheme controls the transmission rate and delay of data users with a priority information such as the number of packets in a queue. From the simulation results, we show that the proposed scheme reduce the blocking probability and delay and improve the performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.11
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• pp.4244-4274
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• 2021

The utilization of UAVs in various fields has led to the development of flying ad hoc network (FANET) technology. In a network environment with highly dynamic topology and frequent link changes, the traditional routing technology of FANET cannot satisfy the new communication demands. Traditional routing algorithm, based on geographic location, can "fall" into a routing hole. In view of this problem, we propose a geolocation routing protocol based on multi-agent reinforcement learning, which decreases the packet loss rate and routing cost of the routing protocol. The protocol views each node as an intelligent agent and evaluates the value of its neighbor nodes through the local information. In the value function, nodes consider information such as link quality, residual energy and queue length, which reduces the possibility of a routing hole. The protocol uses global rewards to enable individual nodes to collaborate in transmitting data. The performance of the protocol is experimentally analyzed for UAVs under extreme conditions such as topology changes and energy constraints. Simulation results show that our proposed QLGR-S protocol has advantages in performance parameters such as throughput, end-to-end delay, and energy consumption compared with the traditional GPSR protocol. QLGR-S provides more reliable connectivity for UAV networking technology, safeguards the communication requirements between UAVs, and further promotes the development of UAV technology.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.6
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• pp.15-22
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• 2012

A performance index of singalized intersections is a standard to optimize signal control variables and to manage traffic flow. Traffic delays is generally used to minimize the average delay time on intersections or networks, progression efficiency is used to improve travel speed of main cooridors or to provide transit signal priority. We manage traffic flows with only selecting one index between delays and progression according to the objective of traffic management and field characteristics. In real field, the driver's satisfaction is high in any performance criteria when the waiting time is shorter and the unnecessary stop in front of traffic is smaller. This paper aims to develop simulation model to represent real progression with concurrently considering delays and progression. In order to reflect an effect of level of traffic volumes and residual queues which don't be considered in prior progression model, we apply shockwave model with flow-density diagram. We derive Cell Transmission Model of Daganzo in order to develop the delay index and the progression index for the macroscopic simulation model. In order to validate the effect, we analysis traffic delays and progression efficiency with comparing this model to Transyt-7F and PASSER V.