• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.467-469
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• 2006

In wireless network environments, as users' demands on high-speed data communications due to increase of multi-media services, the necessity of new high-speed WLAN technologies has appeared. Nowaday, IEEE is standardizing a new WLAN protocol caned as IEEE 802.11n. To effectively use wireless resources, IEEE 802.11n introduces MAC aggregation function which is similar to that in IEEE 802.11e. In case of transmitting several frames without MAC aggregation, the frames include individual frame header and trailer, and their corresponding acknowledgement frames can appear on wireless link. However, if they are aggregated into single MAC frame, we can reduce the number of used bits due to frame headers/trailers and also remove redundant acknowledgement frames. In this paper, we explain two different MAC frame aggregation methods for IEEE 802.11e and IEEE 802.11n and evaluate their throughput by simulations.

• ETRI Journal
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• v.34 no.1
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• pp.98-101
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• 2012

The directional medium access control (MAC) protocol improves the throughput of mobile ad hoc networks but has a deafness problem and requires location information for neighboring nodes. In the dual-channel directional MAC protocol [12], the use of omnidirectional packets does not require the exact location of destination node. In this letter, we propose a tone dual-channel MAC protocol with directional antennas to improve the throughput of mobile ad hoc networks. In the proposed MAC protocol, we use a directional CTS and an out-of-band directional DATA tone with a new blocking algorithm to improve the spatial reuse. We confirm the throughput performance of the proposed MAC protocol by computer simulations using the Qualnet simulator.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1319-1335
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• 2017

This paper proposes an opportunistic reporting-based sensing-reporting-throughput optimization scheme that maximizes the spectral efficiency of secondary users (SUs) in cooperative cognitive radio networks with a soft combining rule. The performance of cooperative spectrum sensing depends on the sensing time, the reporting time of transmitting sensing results, and the fusion scheme. While longer sensing time and reporting time improve the sensing performance, this shortens the allowable data transmission time, which in turn degrades the spectral efficiency of SUs. The proposed scheme adopts an opportunistic reporting scheme to restrain the reporting overhead and it jointly controls the sensing-reporting overhead in order to increase the spectral efficiency of SUs. We show that there is a trade-off between the spectral efficiency of SUs and the overheads of cooperative spectrum sensing. The numerical results demonstrate that the proposed scheme significantly outperforms the conventional sensing-throughput optimization schemes when there are many SUs. Moreover, the numerical results show that the sensing-reporting time should be jointly optimized in order to maximize the spectral efficiency of SUs.

• Journal of IKEEE
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• v.1 no.1 s.1
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• pp.176-184
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• 1997

The Asynchronous Transfer Mode(ATM) networks are being adopted as backbones over various parts of Internet. Also, TCP is one of the most widespread transport protocols, nowdays. It can be used with ATM. But, TCP shows poor end-to-end performance on ATM networks. Effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. The low throughput is due to wasted bandwidth as congested link transmits cells from corrupted packets. This paper examines the behavior of TCP over ATM with limited bandwidth in a broadband environment. As multiple VBR sources occupies most of the available bandwidth, there has been a starvation effect, so TCP sources couldn't get the chance of transmitting data. Also, throughput is proportional to the amount of buffer.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.28-33
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• 2001

Screw conveyors are used extensively in industrial for conveying and elevating materials. Despite their apparent simplicity, the mechanics of the conveying action is very complex. so many engineers depend on experiential data. Capacities of screw are pumping, steady flow of polymer melts, steady volumetric throughput etc. they are affected by geometry of screw, heat flux, pressure on inside barrel, rotating velocity, friction coefficient at screw surface etc. by computation volumetric efficiency increases as rotating velocity increases and decreases as friction coefficient increases. also it decreases with short pitch length. and double flight screw is more effective than single flight screw. The temperature of polymer melts by heating pad and injection pressure play a very important role in the injection molding machine. so in this paper we analyze thermal distortion and stress of screw includes pressure and temperature distributions by finite element analysis to understand what design factors influence on volumetric throughput efficiency of the screw and thermo-mechanical characteristics of screw.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3731-3750
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• 2014

This paper considers a wideband cognitive radio network (WCRN) which can simultaneously sense multiple narrowband channels and thus aggregate the detected available channels for transmission and studies the ergodic throughput of the WCRN that operated under: the wideband sensing-based spectrum sharing (WSSS) scheme and the wideband opportunistic spectrum access (WOSA) scheme. In our analysis, besides the average interference power constraint at PU, the average transmit power constraint of SU is also considered for the two schemes and a novel cognitive radio sensing frame that allows data transmission and spectrum sensing at the same time is utilized, and then the maximization throughput problem is solved by developing a gradient projection method. Finally, numerical simulations are presented to verify the performance of the two proposed schemes.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.533-534
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• 2006

This paper presents the architecture design of a high-speed, low-complexity 128-point radix-$2^4$ FFT processor for ultra-wideband (UWB) systems. The proposed high-speed, low-complexity FFT architecture can provide a higher throughput rate and low hardware complexity by using 2-parallel data-path scheme and single-path delay-feedback (SDF) structure. This paper presents the key ideas applied to the design of high-speed, low-complexity FFT processor, especially that for achieving high throughput rate and reducing hardware complexity. The proposed FFT processor has been designed and implemented with the 0.18-m CMOS technology in a supply voltage of 1.8 V. The throughput rate of proposed FFT processor is up to 1 Gsample/s while it requires much smaller hardware complexity.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.73-76
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• 2000

In the basic continuous ARQ schemes (Go-Back-N or Selective Repeat ARQ), each block is continuously transmitted without interruptions. Only when the transmitter receives NAK from the receiver side, the transmitter stops sending current data block and retransmit the erroneous block (Naked block). When channel error rate increases and become sufficiently high, there exists a point at which each block of message is transmitted, on average, more than once. Under such conditions, it will be more efficient to send continuously two or more copies(generally $\ell$ copies) of each block from the first transmission over noisy channel. A request for repeat will be made again only when none of $\ell$ duplicates are received correctly. By this way, the proposed scheme yields a better throughput efficiency and holds nearly constant throughput as compared to others continuous A.R.Q schemes under wide error rate variations (0 < P < 0.3).

• Journal of Communications and Networks
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• v.14 no.2
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• pp.151-161
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• 2012

This paper considers a two-user Gaussian interference channel with energy harvesting transmitters. Different than conventional battery powered wireless nodes, energy harvesting transmitters have to adapt transmission to availability of energy at a particular instant. In this setting, the optimal power allocation problem to maximize the sum throughput with a given deadline is formulated. The convergence of the proposed iterative coordinate descent method for the problem is proved and the short-term throughput maximizing offline power allocation policy is found. Examples for interference regions with known sum capacities are given with directional water-filling interpretations. Next, stochastic data arrivals are addressed. Finally, online and/or distributed near-optimal policies are proposed. Performance of the proposed algorithms are demonstrated through simulations.

• Journal of the Korea Society for Simulation
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• v.12 no.1
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• pp.21-34
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• 2003

This paper deals with a case study of workload analysis of an operator in an automatic line for machining the race of ball bearing. Eleven machines and three hoppers are installed in the line which is operated by an operator. The elements of operation are separated into machine controlled elements, operator controlled elements and machine/operator controlled elements. In order to analyze the system, time and motion studies are used for gathering input data for the simulation model. The first objective of this study is to evaluate whether the workload of operator is reasonable or not. The second objective is to increase throughput by reducing tact time and the last one is to increase frequencies of inspection by reducing interval. Thus we suggest some ideas for improvement, and as a result, the throughput is improved about 9%. In spite of the increasing of throughput, the allowance of operator is also increased about 4%.