• 한국축산시설환경학회지
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• 제20권1호
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• pp.21-26
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• 2014

The goal of this study was to investigate acoustic characteristic of feed anticipating calls of heifers and cows. 6 cows and 6 heifers housed in a pen ($6.0m{\times}10.0m$) which was bedded with sawdust and straw. They were fed a standard ration of commercial concentrate and hay was ad libitum. The calls of heifers and cows were divided into Type 1 and Type 2 which were classified based on the shapes of waveform and spectrograms, respectively. There was difference in the fundamental frequency (P < 0.0001) and $1^{st}$ formant (P < 0.0077) among the calls. Acoustic parameters with the exception of fundamental frequency and $1^{st}$ formant were no difference between cows' calls and heifers' calls (P > 0.05). Duration of cows' calls was lower than that of heifers' calls, whereas the intensity of Type 1 calls was higher than that of Type 2 calls (P > 0.05).

• 대한수학회지
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• 제35권3호
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• pp.691-712
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• 1998

We consider an M$_1$, M$_2$/G/1/ K retrial queueing system with a finite priority queue for type I calls and infinite retrial group for type II calls where blocked type I calls may join the retrial group. These models, for example, can be applied to cellular mobile communication system where handoff calls have higher priority than originating calls. In this paper we apply the supplementary variable method where supplementary variable is the elapsed service time of the call in service. We find the joint generating function of the numbers of calls in the priority queue and the retrial group in closed form and give some performance measures of the system.

• 전자공학회논문지 IE
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• 제48권4호
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• pp.47-52
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• 2011

본 논문에서는 다양한 형태의 서비스를 고려한 호 수락 방법에 대해 셀룰라 시스템 성능을 분석하였다. 본 연구에서는 호수락 제어 방법으로 등가대역 개념에 신규호의 차단률과 핸드오버호의 절단률에 따라 대역폭을 가변 시키는 방법을 사용하였다. 컴퓨터 시뮬레이션으로 이 호 수락 방법을 사용하여, 핸드오버 호를 위해 자원예약을 두고 또한 수락되지 않는 호는 버퍼에 대기시킴에 따른 시스템의 성능을 살펴보았다.

• International Journal of Contents
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• 제8권2호
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• pp.19-22
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• 2012

New and handoff calls control mechanisms are the key point to wireless cellular networks. In this paper, we present an adaptive algorithm for dynamic channel allocation scheme with guard channels and also with handoff calls waiting queue ensuring that handoff calls take priority over new calls. Our goal is to find better tradeoff between handoffs and new calls blocking probabilities in order to achieve more efficient channel utilization. Simpy is a Python based discrete event simulation system. We use Simpy to build our simulation models to get analytical data.

• 한국통신학회논문지
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• 제21권11호
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• pp.2817-2827
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• 1996

In this paper, we propose a new channel assignment scheme considering traffic characteristics in the CDMA cellular system. The object of proposed method is to reduce the hard handoff of data calls which are very sensitive to transmission errors. In this algorithm, we use three channel assignment policies. First, all of the data calls are assigned to the primary CDMA channel if possible. Second, priority for primary CDMA channel is given to data calls by assigning some primary CDMA traffic channels exclusively for data calls. Third, data calls are assigned to the CDMA channel most served by neighbor cells, when all of the primary CDMA traffic channels are used. A performance analysis shows the minimum soft handoff probability of data calls in handoff which is guarantied any cellconfiguration is increased above 40% by the adopting proposed algorithm.

• 전자공학회논문지B
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• 제33B권6호
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• pp.136-148
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• 1996

In this paper, we analyze the traffic characteristics in microcell and macrocell overlaid PCS system which process voice and dta calls separately each others. in this system, data calls are delayed in queue when all of channels are occupied, while voice calls are bolcked in that case. For this, we calculated inter-microcell handoff area dwelling time distribution and handoff area dwelling time distribution between microcell and macrocell. We analyze traffic performance using this results. We used M/M/C/K model, and analyzed traffic performance of macrocell with handoff area variation of microcell.

• 한국경영과학회지
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• 제23권3호
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• pp.135-151
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• 1998

The demand of large capacity in coming cellular systems makes inevitable the deployment of small cells, rendering more frequent handoff occurrences of calls than in the conventional system. The key issue is then how effectively to reduce the chance of unsuccessful handoffs, since the handoff failure is less desirable than that of a new call attempt. In this study, we consider the control policies which give priority to handoff calls by limiting channel assignment for the originating new calls, and allow queueing the new calls which are rejected at their first attempts. On this system. we propose the problem of finding an optimal call control strategy which optimizes the objective function value, while satisfying the requirements on the handoff/new call blocking probabilities and the new call delay. The objective function takes the most general form to include such well-known performance measures as the weighted average carried traffic and the handoff call blocking probability. The problem is formulated into two different linear programming (LP) models. One is based on the direct employment of steady state equations, and the other uses the theory of semi-Markov decision process. Two LP formulations are competitive each other, having its own strength in the numbers of variables and constraints. Extensive experiments are also conducted to show which call control strategy is optimal under various system environments having different objective functions and traffic patterns.

• 산업경영시스템학회지
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• 제29권4호
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• pp.100-106
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• 2006

We analyze a voice/data integrated traffic model of the cellular mobile communication system with hybrid guard channels for voice and handoff calls. In a multi-service integrated wireless environment, quality of service guarantee is crucial for smooth transportation of real time information. Real time voice traffic requires a guaranteed upper bounded on both delay and packet error rate, whereas data traffic does not. Voice traffic has high transmission priority over data packets. Thus one of the important problems is the design of admission control schemes which can efficiently accommodate the differential quality of service requirements. In this paper, a hybrid guard channel scheme is considered in which arriving calls are assigned channels as long as the number of busy channels in the cell is below a predetermined first threshold. When the number of busy channels reaches the first threshold, new originating data calls are queued in the infinite data buffer. Then reaches second threshold, only handoff calls are assigned the remaining channels and new originating voice calls are blocked. We evaluate the system by a two-dimensional Markov chain approach and generating function method and obtain performance measures included blocking probability and forced termination probability.

• 한국경영과학회지
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• 제36권3호
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• pp.45-59
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• 2011

OFDMA systems have been expected to be widely used to provide multimedia services over wireless channels. To evaluate performance of the OFDMA system, power should be considered as system resource as well as subcarriers. This study propose a queueing traffic model incorporating two kinds of resources (power and subcarriers), and an extended model giving a priority to handoff calls over new calls. Some extensive experiments are conducted to illustrate the usefulness of the proposed traffic model.

• 경영과학
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• 제10권1호
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• pp.127-137
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• 1993

The blocking probabilities of nx64Kb/s multi-slot calls are generally much higher than that of single slot calls. In order to improve these blocking probabilities of multi-slot calls, we propose a scheme which searches the different numbers of time slots for different types of calls. We analyze the performance of our scheme in a double-buffered time-space-time switching network which accommodates multi-slot calls as well as single-slot calls. The proposed method yields the reduced blocking probabilities, the increased traffic handling capacity and teh reduced CPU processing load, compared with those of the conventional methods.