• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.5
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• pp.1-9
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• 2000

In this paper, for the reverse link of a imperfect power controlled DS/CDMA cellular system when a mobile radio channel is a Rayleigh distributed multipath fading channel, A extended DS/CDMA blocking probability formula considering both shadowing and multipath fading is derived. Erlang capacity and equivalent channel number considering shadowing are analyzed and compared with those considering both shadowing and multipath fading, respectively. The DS/CDMA blocking probability is calculated based on the analysis method that obtains Erlang capacity and ICF(interference correction factor) using the median value of $E_{b(i)}$/ $I_{0}$ corresponding to each reverse link user Assuming that the blocking probability set 2%, it is observed that the Erlang capacity is 19.97 Erlang at the data rate $R_{b}$=9.6 kbps and 11.67 Erlang at the data rate $R_{b}$=14.4 kbps and then is less 16% and 19% than the Erlang capacity considering shadowing only, respectively. It is also shown that the effect of multipath fading must not be ignored and then exact Erlang capacity and equivalent channel numbers that the DS/CDMA cellular system can support are provided.d.d.d.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.8
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• pp.1-10
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• 2000

Performance analyses of hybrid DS-SFH spread-spectrum systems using coherent MSK and QPSK modulation techniques are considered over Rayleigh fading channel in the presence of multi-tone jamming. The BER equations for MSK and QPSK systems with non-diversity reception in the receiver are derived as the concept of average signal-to-noise power ratio E$\_$b//N$\_$0/ and jamming-to-signal power ratio JSR, and the performances is evaluated for various system parameters. The evaluation of performance is done between fading and nonfading system, and between MSK and QPSK system. Results show that the performances of two systems are similar in low JSR. However, MSK system outperforms QPSK system as JSR increases. Overall performances of two systems are a little improved as the DS spreading gain increases for the total spread-spectrum bandwidth fixed. The performance difference between fading system and nonfading system is similar in low E$\_$b//N$\_$0/, however, it becomes very largewith increase of E$\_$b//N$\_$0/..

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.27-37
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• 2009

Sensor nodes forming a sensor network have limited energy capacity such as small batteries and when these nodes are placed in a specific field, it is important to research minimizing sensor nodes' energy consumption because of difficulty in supplying additional energy for the sensor nodes. Clustering has been in the limelight as one of efficient techniques to reduce sensor nodes' energy consumption in sensor networks. However, energy saving results can vary greatly depending on election of cluster heads, the number and size of clusters and the distance among the sensor nodes. /This research has an aim to find the optimal set of clusters which can reduce sensor nodes' energy consumption. We use a Genetic Algorithm(GA), a stochastic search technique used in computing, to find optimal solutions. GA performs searching through evolution processes to find optimal clusters in terms of energy efficiency. Our results show that GA is more efficient than LEACH which is a clustering algorithm without evolution processes. The two-dimensional GA (2D-GA) proposed in this research can perform more efficient gene evolution than one-dimensional GA(1D-GA)by giving unique location information to each node existing in chromosomes. As a result, the 2D-GA can find rapidly and effectively optimal clusters to maximize lifetime of the sensor networks.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.89-96
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• 2009

As increasing the number of digital control devices installed on aircrafts and their transmission speed, various digital data buses have been introduced to provide reliable and high-speed characteristics. These characteristics of avionics data bus are highly related on the fault-tolerant performance which can make minimize jitter and loss during data transfer. In this paper, we concerned about a new traffic shaping scheme for increasing the reliability of Avionics Full Duplex Switched Ethernet (AFDX) systems based on ARINC 664 standard. We note that the conventional AFDX with a single regulator per virtual link system may produce aggregated traffics as the number of virtual links increasing. The aggregated traffic results in large jitters among frames. To remedy for the jitter and loss of data, we propose a dual regulator scheme for the AFDX system. The purpose of the additional regulator is to additionally regulate aggregated traffics from a number of per virtual link regulators. Using NS-2 simulator, we show that the proposed scheme provides a better performance than the single regulator one. It is worthwhile note that the proposed AFDX with Dual Regulator scheme can be employed to not only aircraft networks but other QoS sensitive networks for robot and industrial control systems.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.10
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• pp.28-33
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• 2009

In this paper, we propose the receiver algorithms suitable for the VHF (Very High Frequency) digital link mode-2(VDL Mode-2) system. Unlike conventional digital communication systems using the root raised cosine filter as a transmit and receive filter, raised cosine filter is used as a transmit filter in the VDL Mode-2 system. Hence, it is crucial to design and implement the optimum lowpass receive filter by considering inter-symbol interference and noise performance. On the other hand, due to the short preamble pattern, it is crucial to develop an efficient packet detection algorithm for reliable communication link for the VDL Mode-2 system. Also, frequency offset due to the carrier frequency difference between transmitter and receiver and doppler frequency shift must be estimated and compensated for reliable communication. In this paper, the optimum receive filter, packet detection and frequency offset compensation algorithms are proposed and the performance of the VDL system employing the proposed algorithms are evaluated.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.10
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• pp.14-27
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• 2009

Polar Code was proposed by Turkish professor Erdal Arikan in 2006 as an idea that splitted input channel is increasing the cutoff rate. The channel polarization consisted of code sequences with symmetric high rate capacity in a given B-DMC(Binary-input Discrete Memoryless Channel) W. The symmetric capacity is the highest rate achievable subject to using the input letters of the channel with equal probability. The channel polarization is said to a set of given N independent outputs of B-DMC W. In other word, N increases when N is a set of binary-input channels {$W^{(i)}_N\;:\;1{\leq}\;i\;{\leq}\;N$}, in I{WN(i)} as the fraction of indices is near to 1, which is approaching to I(W), and it is near to 0, then to 1-I(W), where I(W) presents high rates in reliable wireless communication channel as inputs of W with equal frequences. After all, {WN(i)} is shown to be a state of channel coding. On the based on this Polar codes, this paper analyzes Polar coding and decoding of Arikan and propose Radix4 Polar coding newly.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.84-89
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• 2010

In this paper, a novel voltage-controlled oscillator (VCO) using the microstrip square open loop dual split ring resonator is presented for reducing the phase noise. The square-shaped dual split ring resonator having the form of the microstrip square open loop is investigated to reduce the phase noise. Compared with the microstrip square open loop resonator and the microstrip square open loop split ring resonator as well as the conventional microstrip line resonator, the microstrip square dual split ring resonator has the larger coupling coefficient value, which makes a higher Q value, and has reduced the phase noise of VCO. The VCO with 1.7V power supply has the phase noise of -123.2~-122.0 dBc/Hz @ 100 kHz in the tuning range, 11.74~11.75 GHz. The figure of merit (FOM) of this VCO is-214.8~-221.7 dBc/Hz dBc/Hz @ 100 kHz in the same tuning range. Compared with VCO using the conventional microstrip line resonator, VCO using microstrip square open loop resonator, the phase noise of VCO using the proposed resonator has been improved in 26 dB, 10 dB, respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.10
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• pp.80-85
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• 2010

In this paper, a MIMO antenna is proposed for LTE/DCSl800/USPCSl900 handset applications. The proposed antenna is based on the IFA and its wide bandwidth is obtained by using a stagger tuning technique. To improve the isolation, a suspended line is connected to the shorting points in two antennas, and capacitors and inductors are added to the connected suspended line. Two identical antennas of which dimension is 2.8cc($40{\times}10{\times}7mm$) are mounted on the two end lines of the system ground plane($40{\times}60mm$). Analysis of the antenna performance and optimization is performed using CST Microwave Studio. The bandwidths are satisfied for LTE band class 13(746-787MHz), class 14(758-798MHz) and DCSl800/USPCSl900 band (1710-1990MHz). The isolations between two antennas are about -12dB for LTE band and -10dB for DCSl800/USPCSl900 band. And the radiation efficiency of each antenna is about for LTE band 33% and 45% for DCSl800/USPCSl900 band respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.9
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• pp.29-36
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• 2010

Consider an RFID network configured as a star such that a single reader is surrounded by a crowd of tags. In the RFID network, prior to attaining the information stored at a tag, the reader must cognize the tags while arbitrating a collision among tags' responses. For this purpose, we present a tag cognizance scheme based on framed and slotted ALOHA, which statically provides a number of slots in each frame for the tags to respond. For the evaluation of the cognizance performance, we choose the cognizance completion probability and the expected cognizance completion time as key performance measures. Then, we present a method to numerically calculate the performance measures. Especially, for small numbers of tags, we derive them in a closed form. Next, we formulate a problem to find an optimal time structure which either maximizes the cognizance completion probability under a constraint on the cognizance time or minimizes the expected cognizance completion time. By solving the problem, we finally obtain an optimal number of slots per frame for the tags to respond. From numerical results, we confirm that there exist a finite optimal number of slots for the tags to respond. Also, we observe that the optimal number of slots maximizing the cognizance completion probability tends to approach to the optimal number of slots minimizing the expected cognizance completion time as the constraint on the cognizance time becomes loose.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.45-51
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• 2010

The main issue in mobile cloud computing is how to support a seamless service to a mobile mode. Mobile IPv6 (MIPv6) is a mobility supporting protocol which is standardized by the Internet Engineering Task Force (IETF). Mobile IPv6 fast handovers (FMIPv6) is the extension of MIPv6 which is proposed to overcome shortcomings of MIPv6. Recently, fast handovers for Mobile IPv6 over IEEE 802.16e which is one of broadband wireless access systems has been proposed by the IETF. It was designed for supporting cross-layer fast handover. In this paper, we propose an enhanced cross-layering mobile IPv6 fast handover over IEEE 802.16e networks. In our scheme, a new access router generates a new address for the mobile node by using a layer 2 trigger. We utilize a layer 2 message which is sent from a new base station to the new access router in order to inform the new access router of information of the mobile node. A previous access router sends a binding update message to the mobile node's home agent when it acquires the new address of the mobile node. We evaluate the performance of the proposed scheme compared with the existing schemes in terms of the signaling cost and the handover latency. From the results, we observe that the proposed scheme can support fast handover effectively over IEEE 802.16e networks than existing schemes.