• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.4
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• pp.59-67
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• 2016

With the enhancement of built-in communication capabilities in various meters and wearable devices, which implies Internet of things (IoT), the demand of small-area embedded processors has increased. In this paper, we introduce a small-area 32-bit pipelined processor, Juno, which is available in the field of IoT. Juno is an EISC (Extendable Instruction Set Computer) machine and has a 2/3-stage pipeline structure to reduce the data dependency of the pipeline. It has a simple pipeline controller which only controls the program counter (PC) and two pipeline registers. It offers $32{\times}32=64$ multiplication, 64/32=32 division, $32{\times}32+64=64$ MAC (multiply and accumulate) operations together with 32*32=64 Galois field multiplication operation for encryption processing in wireless communications. It provides selective inclusion of these algebraic logic blocks if necessary in order to reduce the area of the overall processor. In this case, the gate count of our integer core amounts to 12k~22k and has a performance of 0.57 DMIPS/MHz and 1.024 Coremark/MHz.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.19-24
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• 2016

In Long Term Evolution-Advanced (LTE-A), small cell enhancement(SCE) has been developed as a cost-effective way of supporting exponentially increasing demand of wireless data services and satisfying the user quality of service(QoS). However, due to the dense and irregular distribution of a large number of small cells, the offloading scheme should be applied in the small cell network. In this paper, we propose an user offloading scheme for SCE in LTE-Advanced system. We divide the small cells into different clusters according to the reference signal received power(RSRP) from user equipment(UE). Within a cluster, We apply the user offloading scheme with the consideration of the number of users and interference conditions. Simulation results show that proposed scheme can improve the throughput, and spectral efficiency of small cell users. Eventually, proposed scheme can improve overall cell performance.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.13-18
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• 2016

In Long Term Evolution-Advanced (LTE-A), small cell enhancement(SCE) has been developed as a cost-effective way of supporting exponentially increasing demand of wireless data services and satisfying the user quality of service(QoS). However, there are many problems such as the transmission rate and transmission quality degradation due to the dense and irregular distribution of a large number of small cells. In this paper, we propose a clustering based interference management scheme in dense small cell network. We divide the small cells into different clusters according to the reference signal received power(RSRP) from user equipment(UE). Within a cluster, an almost blank subframe(ABS) is implemented to mitigate interference between the small cells. In addition, we apply the power control to reduce the interference between the clusters. Simulation results show that proposed scheme can improve Signal to Interference plus Noise Ratio(SINR), throughput, and spectral efficiency of small cell users. Eventually, proposed scheme can improve overall cell performance.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.101-111
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• 2008

This paper introduces a high-speed Reed-Solomon(RS) decoder, which reduces the hardware complexity, and presents an RS decoder based FEC architecture which is used for 40Gb/s optical communication systems. We introduce new pipelined degree computationless modified Euclidean(pDCME) algorithm architecture, which has high throughput and low hardware complexity. The proposed 16 channel RS FEC architecture has two 8 channel RS FEC architectures, which has 8 syndrome computation block and shared single KES block. It can reduce the hardware complexity about 30% compared to the conventional 16 channel 3-parallel FEC architecture, which is 4 syndrome computation block and shared single KES block. The proposed RS FEC architecture has been designed and implemented with the $0.18-{\mu}m$ CMOS technology in a supply voltage of 1.8 V. The result show that total number of gate is 250K and it has a data processing rate of 5.1Gb/s at a clock frequency of 400MHz. The proposed area-efficient architecture can be readily applied to the next generation FEC devices for high-speed optical communications as well as wireless communications.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.94-105
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• 2008

Numerous platforms have been developed for ZigBee-based network embedded systems. Also, operating systems like TinyOS have been installed to facilitate efficient implementation of wireless sensor network applications which collect data, and/or execute commands. First of all, porting an operating system on a new platform may need invention of a substitute for a required but unsupported hardware component. This paper presents a multiplexed virtual system timer for a platform without a counter comparator which we have contrived to emulate by using an extra counter. Such porting also injects unexpected faults which cause a variety of painful failures. Unfortunately, TinyOS requires to handle a lot of asynchronous hardware interrupts which are hard to trace during debugging. Besides, simulators are not available for a new platform since the models of hardware on the platform are not usually developed, yet. We propose novel instrumentation techniques which can be used to effectively trace the bugs in such lack of debugging environment. These techniques are used to identify and fix a great deal of nasty issues in porting TinyOS 2.0 on MG2400 and MG2455 platforms made by RadioPulse Inc.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.10
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• pp.45-52
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• 2008

We investigated the design of an RF-powered, wireless temperature sensor tag chip using $0.18-{\mu}m$ CMOS technology. The transponder generates its own power supply from small incident RF signal using Schottky diodes in voltage multiplier. Ambient temperature is measured using a new low-power temperature-to-voltage converter, and an 8-bit single-slope ADC converts the measured voltage to digital data. ASK demodulator and digital control are combined to identify unique transponder (ID) sent by base station for multi-transponder applications. The measurement of the temperature sensor tag chip showed a resolution of $0.64^{\circ}C/LSB$ in the range from $20^{\circ}C$ to $100^{\circ}C$, which is suitable for environmental temperature monitoring. The chip size is $1.1{\times}0.34mm^2$, and operates at clock frequency of 100 kHz while consuming $64{\mu}W$ power. The temperature sensor required a -11 dBm RF input power, supported a conversion rate of 12.5 k-samples/sec, and a maximum error of $0.5^{\circ}C$.

• Journal of IKEEE
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• v.18 no.4
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• pp.544-551
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• 2014

This paper suggests an algorithm to measure low-level radiation by radiation measuring devices, and the other algorithm to improve reaction speed of the device to better respond to dramatic changes in radiation amount. The former algorithm to improve the accuracy of measuring low-level radiation takes advantage of a dual window radiation measurement method which is based on accumulated average of pulses gathered by a radiation measuring sensor. The latter algorithm is to enhance reaction speed of a measuring device to more sensitively react to dramatic changes in radiation amount by adopting a dual window radiation measurement method which analyzes data patterns newly put into for six seconds. To verify the suggested algorithms, a hardware-which consists of sensor and high-voltage generator, controller, charger and power supply circuit, wireless communication part, and display part-was used. Tests conducted on the dual window radiation measurement method as used in the suggested algorithm have proved that accuracy improves to measure low-level radiation of 5uSv/h, and linearity also gets better. Other tests were conducted to see whether the suggested algorithm enhances the reaction speed of a radiation measuring device so that the device responds better to dramatically changing radiation amount. The experimental results have shown meaningful changes in numbers after six seconds. Therefore, the conclusions are made that the algorithm enhances the reaction speed of the device.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.9
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• pp.809-819
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• 2004

In this paper, in order to exclude the expansion of M/W relay frequency or its new frequency assignment possibly, we analyzed a possibility of substituting M/W system by B-WLL or optical fiber network regarding service quality and economical points. To define the target of service quality, pre-condition and analysis method for the selected media have been derived to compare each other. E1 transmission with BER 10$^{-1}$ was chosen as a reference capacity, and service distance was calculated f3r the selected media as a function of availability. Also from the economical point we considered 3 systems such as optical fiber, M/W, and B-WLL based upon basic system structure, and analyzed them for various line configurations of fiber optic and B-WLL according to service period, system capacity, transmission distance, and data rate. It was confirmed that B-WLL can provide quality of service with 99.999 % availability within 1.6 km cell radius, and for optical fiber substitution, the leased fiber conduit on an electric pole is more economical than M/W system irrespective of service period, but in case of directly digging for underground conduit, it turned out ineffective regardless of cabling duct types.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.5
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• pp.908-915
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• 2001

In this paper, it is analyzed theoretically that the performance degradation, caused by carrier frequency offset, in an OFDM/M-ary PSK system. Then, when Turbo coding is adopted to an OFDM/M-ary PSK system, the degree of performance enhancement is evaluated. Finally, the maximum frequency offset is calculated to satisfy the BER performance required in a Turbo coded OFDM/M-ary PSK system. As results of analysis, it is shown that the more the number of M-ary is, the worse the BER performance is. Moreover, 7dB, 9dB, and 17dB of $E_b/N_o$ are required in QPSK, 8PSK and 16PSK systems, respectively in order to satisfy the error performance, $BER=10^{-3}$ for voice communication. If $E_b/N_o$ are 10㏈ and 15㏈, the frequency offset should be below 0.05 and 0.075, respectively, for voice communication. When Turbo coding is adopted to an OFDM/M-ary PSK system, the less the number of M-ary is, the greater the performance enhancement of Turbo coding is. If the number of a M-ary system of the system is below 16, it is found that required $E_b/N_o$ is about 8dB to satisfy $BER=10^{-5}$ Moreover, in the system the Turbo coding scheme, voice communication is available with greatly low$E_b/N_o$, and 8dB of $E_b/N_o$ is enough for data communication regardless of the permission range of frequency offset.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.277-288
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• 2013

3GPP LTE-Advanced (Third Generation Partnership Project Long Term Evolution-Advanced) as a next generation mobile communication standard introduced small base stations such as femto cells or pico cells, and D2D (Device-to-Device) communications between mobiles in the proximity in order to satisfy the needs of rapidly growing wireless data traffic. A diverse range of topics has been studied to solve various interference situations which may occur within a single cell. In particular, an introduction of a small base station along with D2D communication raises important issues of how to increase the channel capacity and frequency efficiency in HetNets (Heterogeneous Networks). To this end, we propose in this paper methods to manage the interference between the macro cell and other small cells in the HetNet to improve the frequency efficiency. The proposed CCN (Cluster Coordinator Node)-assisted ICI (Inter-Cell Interference) avoidance methods exploit the CCN to control the interference in HetNet comprising of an MeNB (Macro enhanced Node-B) and a large number of small cells. A CCN which is located at the center of a number of small cells serves to avoid the interference between macro cell and small cells. We propose methods of resource allocation to avoid ICI for user equipments within the CCN coverage, and evaluate their performance through system-level computer simulations.