• Journal of information and communication convergence engineering
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• v.5 no.2
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• pp.93-97
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• 2007

In this paper, centralized access control and slot allocation algorithm is proposed for wireless networks. The proposed algorithm is characterized by the contention-based reservation. In order to reduce the collision probability of reservation request, the base station calculates and broadcasts the transmission probability of reservation requests, and the wireless terminal transmits its reservation request with the received transmission probability. The scheduler allocates the uplink data slots based on the successful reservation requests. Simulation results show that the proposed algorithms can provide high channel utilization, and furthermore, maintains constant delay performance in the heavy traffic environment.

• Journal of information and communication convergence engineering
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• v.8 no.6
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• pp.677-681
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• 2010

This paper proposes a transmission probability control scheme for enhancing the performances of FSA-based RFID system. In order to maximize the system performance, the number of tags attempting to transmit their identifiers in a frame should be kept at a proper level. The reader calculates the transmission probability according to the number of tags within the identification range of reader and then broadcasts it to tags. Tags, in which their slot counter values reach to zero, attempt to transmit their identifiers with the received probability. Simulation results show that the proposed scheme can offer better throughput and delay performance than the conventional one regardless of the number of tags.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3638-3654
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• 2014

Cognitive Radio (CR) users need to sense the environment or channel at regular time interval for sharing the spectrum band of the primary users (PUs). Once find the spectrum idle, CR users start their transmission through it. Even while transmitting, they need to continue the sensing process so that they can leave the spectrum immediately whenever find a PU wanting to use the band. Therefore, detecting PUs is one of the main functions of cognitive radio before transmission and higher the detection probability ensures better protection to the primary users. However, it is not possible to attain a high detection probability (or a low miss detection probability) and low false alarm probability simultaneously as there is a tradeoff between false alarm probability ($P_{fa}$) and the probability of detection ($P_d$). In this paper, the author has provided a comprehensive study on different sensing techniques and discussed their advantages and disadvantages. Moreover, it is expected that, with this article, readers can have a through understanding of sensing techniques in CR and the current research trends in this area.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.3
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• pp.446-458
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• 2013

Recently, energy-efficient cellular transmission has received considerable research attention to improve the energy efficiency of wireless communication. In this paper, we consider a cellular network consisting of one base station (BS) and multiple user terminals and explore the network coding for enhancing the energy efficiency of cellular downlink transmission from BS to users. We propose the network coded cellular transmission scheme and conduct its energy consumption analysis with target outage probability and data rate requirements in Rayleigh fading environments. Then, the energy efficiency in Bits-per-Joule is further defined and analyzed to evaluate the number of bits delivered per Joule of energy cost. Numerical results show that the network coded cellular transmission significantly outperforms the traditional cellular transmission in terms of energy efficiency, implying that given a Joule of energy cost, the network coded cellular transmission scheme can deliver more bits than the traditional cellular transmission.

• International Journal of Contents
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• v.12 no.1
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• pp.65-69
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• 2016

Wireless communication chipsets have fixed transmission rate and communication distance. Although there are many kinds of chipsets with throughput and distance purpose, they cannot support various types of wireless applications. This paper provides theoretic research results in order to support various wireless applications requiring different throughput, delayed quality-of-service (QoS), and different communication distances by using a wireless communication chipset with fixed rate and transmission power. As a performance metric, the probability for a data frame that successfully receives at a desired receiver is adopted. Based on this probability, the average number of transmission in order to make a successful frame transmission is derived. Equations are utilized to analyze the performance of a single-hop with channel coding and a dual-hop without error correction matter transmission system. Our results revealed that single-hop transmission assisted by channel coding could extend its communication distance. However, communication range extending effect of the single-hop system was limited. Accordingly, dual-hop transmission is needed to overcome the communication distance limit of a chipset.

• Journal of Information Processing Systems
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• v.15 no.2
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• pp.331-343
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• 2019

Dynamic thermal rating of the overhead transmission lines is affected by many uncertain factors. The ambient temperature, wind speed and wind direction are the main sources of uncertainty. Measurement uncertainty is an important parameter to evaluate the reliability of measurement results. This paper presents the uncertainty analysis based on Monte Carlo. On the basis of establishing the mathematical model and setting the probability density function of the input parameter value, the probability density function of the output value is determined by probability distribution random sampling. Through the calculation and analysis of the transient thermal balance equation and the steady- state thermal balance equation, the steady-state current carrying capacity, the transient current carrying capacity, the standard uncertainty and the probability distribution of the minimum and maximum values of the conductor under 95% confidence interval are obtained. The simulation results indicate that Monte Carlo method can decrease the computational complexity, speed up the calculation, and increase the validity and reliability of the uncertainty evaluation.

• ETRI Journal
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• v.39 no.5
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• pp.729-736
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• 2017

This work investigates secure cluster-aided multi-hop randomize-and-forward networks. We present a hop-by-hop multi-hop transmission scheme with relay selection, which evaluates for each cluster the relays that can securely receive the message. We propose an analytical model to derive the secure connectivity probability (SCP) of the hop-by-hop transmission scheme. For comparison, we also analyze SCPs of traditional end-to-end transmission schemes with two relay-selection policies. We perform simulations, and our analytical results verify that the proposed hop-by-hop scheme is superior to end-to-end schemes, especially with a large number of hops or high eavesdropper channel quality. Numerical results also show that the proposed hop-by-hop scheme achieves near-optimal performance in terms of the SCP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1501-1509
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• 1996

Mobile stations can be classified by the transmission power level in CDMA system. Different performance parameters will be given to each class of mobile stations so that the appropriate quality ofservices can be provided. In this paper, it is assumed that there are two clsses of mobile stations. with the classification of mobile stations, analytical models are presented for the estimates of the reverse link capacity and the blocking probability. From the model for the reverse link capacity, the maximum number of each class of mobile stations to be served is derived. It is shown that $E_{b/}$I reduction of 1 dB allows the capacity to be increased by 25% and the data transmission rate and the power control accuracy have a significant effect on the reverse link capacity and the blocking probability. Simulation results are provided for validating the anlaytical estimates of the blocking probability.ocking probability.y.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1784-1788
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• 2012

In this paper we considered condition for keep standard error probability in optical transmission system that applied on-off keying transmission which are modulated amplitude along the signal. we calculated received sensitivity of receiver in on-off keying transmission for optical detector have quantum efficiency belong 1 in optical transmission system. For BT is over 30, the number of photon is belong 10000 for maintain standard error probability. also we considered Also, we install a preamplifier to the receiver for considering the low output may be used with a light that was able to get results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.485-492
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• 2003

This paper proposes a transmission probability control scheme for guaranteeing fair packet transmissions in CDMA slotted ALOHA system. In CDMA slotted ALOHA system, the packets transmitted in the same slot act as multiple access interference, so that unsuccessful packet transmissions are caused entirely by multiple access interference. Therefore, in order to maximize the system throughput, the number of simultaneously transmitted packets should be kept at a proper level. In the proposed scheme, the base station calculates the packet transmission probability of mobile stations in the next slot according to the offered load and then broadcasts this probability to all the mobile stations. Mobile stations, which have a packet to transmit, attempt to transmit packet with the received probability. Simulation results show that the proposed scheme can offer better system throughput and average delay than the conventional scheme, and guarantee a good fairness among all mobile stations regardless of the offered load.