• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.64-67
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• 1997

In the total artificial heart(TAH), a transcutaneous information transmission system(TITS) is vely important to monitor the TAH status and detect the device failure, and repair the possible problems. First of all, the communication channel(skin) and method were simulated in terms of transmittance, scattering, reflection and absorption, then the system was designed with size reduction including low power consumption and reliability compared to the previous one. The informations are transmitted through the skin(approximately 1cm in depth) by frequency modulated near infrared(NIR) pulses using 780nm laser diodes as transmitters and photodiode as receiver with high speed and high spectral sensitivity. The logic high and low frequencies are 3MHz, 1MHz respectively. The system is a bidirectional data link for more than 38.4Kbps data rate, full-duplex with a bit error rate of less than $10^{-5}$.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.12
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• pp.1359-1364
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• 2014

IEEE 802.11p is a representative PHY/MAC layer standard in vehicular communications. The performance of IEEE 802.11p based communication systems has been measured in various criterions such as link setup time, error rate, and throughput for the case of one-to-one. In this paper, we measure the performance of IEEE 802.11p based communication systems in large capacity transmission. The performance of large capacity transmission is measured by considering the maximum 32 simultaneous transmission including one-to-one transmission. We consider two transmission schemes, i.e., broadcasting and unicasting, and the performance is represented as the receiving rate and throughput.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3431-3445
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• 2017

Due to the advantages of low transmit power consumption, high spectral efficiency and extended system coverage, Device-to-Device (D2D) communication has drawn explosive attention in wireless communication field. Considering that intra-cell interference caused between cellular signals and D2D signals, in this paper, a network coding-based D2D relay cooperative transmission algorithm is proposed. Under D2D single-hop relay transmission mode, cellular interfering signals can be regarded as useful signals to code with D2D signals at D2D relay node. Using cellular interfering signals and network coded signals, D2D receiver restores the D2D signals to achieve the effect of interference suppression. Theoretical analysis shows that, compared with Amplify-and-forward (AF) mode and Decode-and-forward (DF) mode, the proposed algorithm can dramatically increase the link achievable rate. Furthermore, simulation experiment verifies that by employing the proposed algorithm, the interference signals in D2D communication can be eliminated effectively, and meanwhile the symbol error rate (SER) performance can be improved.

• Journal of Advanced Navigation Technology
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• v.14 no.2
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• pp.198-205
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• 2010

Any user in Ubiquitous environments have to be able to access networks in anywhere and anytime. Thus interests and researches are increasing. In this paper, we propose an interface selection scheme that adaptively utilizes a proper interface, as the wireless channel condition changes, instead of utilizing only one interface while the node is in move. The proposed scheme can determine which interface would be the most proper one by measuring data rate, packet error rate (PER), and end-to-end delay of each interface. From the simulation results, it is verified that the proposed scheme is able to enhance packet transmission about 20% better.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.2027-2034
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• 1997

Frame relay is a fast packet switching technology that performs relaying and multiplexing frames with variable lengths over a wide area link at the T1 or E1 speed, by elminating error and flow control in the network. In frame relay networks, congestion control is typically performed through the rate enforcement with a discard eligibility (DE) bit, and the explicit negative feedback meachanisms using explicit congetion notification bits. In this paper, we consider the congestiong control scheme using the rate enforcement mechanism with DE bit for frame relay network. Assuming that each frame with exponentially distributed length arrives according to the Poission fashion, we can treat the frame relay switch as an M/M/1/K priority queueing system with pushout basis. We analyze and present the blocking probabilities and waiting time distributions of frames.

• Journal of Advanced Navigation Technology
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• v.10 no.2
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• pp.103-113
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• 2006

The numerical methods of finding the optimal position of optical phase conjugator (OPC) and the optimal fiber dispersions are proposed, which are able to effectively compensate overall channels in $8{\times}40$ Gbps WDM system with non zero-dispersion shifted fiber (NZ-DSF) as an optical fiber. And BER characteristics in the system with two induced optimal parameters are compared with those in the system with the currently used mid-span spectral inversion (MSSI) in order to confirm the availability of the proposed methods. It is confirmed that two optimal parameters depend on each other, but less related with the searching procedure. The methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which is a serious problem but the condition in the case of applying the OPC into multi-channels WDM system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.10
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• pp.1854-1862
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• 2006

The numerical methods of finding out the optimal position of optical phase conjugator (OPC) and the optimal fiber dispersions are prosed, which are able to effectively compensate overall channels in $8{\times}40Gbps$Gbps WDM system with non zero - dispersion shifted fiber (NZ-DSF) as an optical fiber. And BER characteristics in the system with two induced optimal parameters are compared with those in the system with the currently used mid-span spectral inversion (MSSI) in order to confirm the availability of the proposed methods. It is confirmed that the applying two induced optimal parameters into WDM system contribute to reduce power penalty to 4 times than that of WDM system with the conventional MSSI. Thus, the methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which generates a serious problem if it was not made but it is the condition in the case of applying the OPC into multi-channels WDM system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.69-74
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• 2014

In this paper, an energy harvesting scheme is investigated in the multi-relay cooperation communication. Our proposal is to maximize the diversity gain and overcome the disadvantages of the limited power wireless devices. The best relay is selected based on the maximizing channel gains from source to relays so that the harvested energy at selected relay is best. If an internal power of the best relay is lower than a defined target power, the best relay will harvest the energy from the source, and the help of the source-destination link is changed to the second best relay. By this operation method, the diversity gain is maintained and the performance of the network is improved. Finally, performance of the proposed protocol is analyzed in terms of bit error rate, utilization efficiency, power collection efficiency.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.27-31
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• 2006

Millimeter over Fiber (MMoF) technique modulates millimeter wave signal optically to transmit it through an optical fiber for long distances with small loss. MMoF system usually uses optical single sideband (OSSB) modulation scheme to reduce fiber chromatic dispersion and obtain high bandwidth efficiency. The optical link of MMoF system using OSSB is treated as a nonlinear amplifier, and the AM/AM characteristic function of the amplifier is a Bessel function of the first kind of order 1. In this paper, we investigate the performance of OFDM MMoF system considering nonlinearity of OSSB modulation. We estimate a power of the nonlinear distortion noise to analyze the theoretical bit error rate(BER), and perform a simulation to verify the theoretical BER.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1B
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• pp.1-7
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• 2000

Generally, one-dimensional fiber optic code-division multiple-access(CDMA) system is encoded and decoded using optical orthogonal codes(OOC’s), where two-dimensional fiber optic CDMA system uses optical orthogonal signature pattern codes(OOSPC’s) for parallel data link process. The OOSPC’s should have good autocorrelation and cross-correlation properties. However, if timing information or synchronization of OOSPC’s can be obtained by other means, the property of autocorrelation may not be restricted and we can increase the number of pattern codes. In this paper we introduce the fiber optic CDMA system for parallel transmission of two-dimensional data and investigate methods of generation of two-dimensional pattern codes. The probability density function of interference noise is calculated in interfering OOSPC’s of the users and the corresponding bit error rate is derived.. We compare each OOSPC’s by plotting bit error rate versus threshold values and the number of simultaneous users, from the result, we propose the optimal OOSPC’s conditions for the parallel transmission of two-dimensional data.