• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.481-486
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• 2022

The recent rapid growth of the IoT(Internet of Things) is leading to the spread of low-power wireless technology. A major challenge in designing IoT wireless networks is to achieve coexistence between different wireless technologies that share the 2.4 [GHz] ISM (Industrial Scientific Medical) frequency band. Therefore, there is a need for research on improving the reliability of wireless networks and coexisting operation between wireless networks. In particular, it is necessary to study an interference model and performance for mutual service coexistence in a BLE (Bluetooth Low Energy) wireless network environment, which is expected to be widely used as a connection medium between devices in various industrial fields. In this paper, the co-channel interference model with the IEEE 802.15.4 system is established focusing on the physical layer of the BLE system widely used in residential and industrial wireless applications, and the performance of the BLE wireless communication system is analyzed in the co-channel interference environment. As a result of the analysis, as the distance between the interference source and the BLE system increases in an environment where noise and co-channel interference exist, the amount of co-channel interference decreases and the error rate performance of the BLE system improves.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3672-3688
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• 2016

The nonorthogonality between the real and imaginary FBMC/OQAM modulated signals complicates the channel estimation (CE) process, and conventional OFDM CE methods cannot be directly applied to FBMC/OQAM. The conventional preamble-based CE schemes in FBMC/OQAM systems are mainly based on the interference approximation method (IAM) to improve the estimation performance. In this paper, we develop a novel preamble structure to improve the CE performance. We exploit the symmetry pattern to cancel interference and take into account the interference weights in this symmetric structure. The conventional preamble and the proposed preamble are compared via simulations in the IEEE 802.22, 3GPP Vehicular A and Pedestrian A channels. Numerical simulation results demonstrate that the proposed preamble can achieve better bit error ratio (BER) and mean squared error (MSE) performance under the three channel models considered.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.11
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• pp.927-936
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• 2012

In this paper, we study joint feedback design for interference channel (IC). We develop a simple iterative algorithm for the joint feedback design to maximize the expected rate when the transmitters use partial channel-state information (CSI) obtained by the feedback link. Also, from the simulation result, we show that the performance gain is obtained compared to the conventional scheme.

• ETRI Journal
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• v.31 no.4
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• pp.357-364
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• 2009

In this paper, we propose a novel equalization on-channel repeater (OCR) with a feedback interference canceller (FIC) to relay terrestrial digital multimedia broadcasting signals in single frequency networks. The proposed OCR not only has high output power by cancelling the feedback signals caused by insufficient antenna isolation through the FIC, but also shows better output signal quality than the conventional OCR by removing multipath signals existing between the main transmitter and the OCR through an equalizer. In addition, computer simulations and laboratory test results demonstrate that the proposed OCR successfully cancels feedback signals and compensates channel distortions and provides a higher quality transmitting signal with higher output power than conventional OCRs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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• pp.475-490
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• 2010

Cognitive Radio is an advanced enabling technology for the efficient utilization of vacant spectrum due to its ability to sense the spectrum environment. It is important to determine accurate spectrum utilization of the primary system in a cognitive radio environment. In order to define the spectrum utilization state, many CR systems use what is known as the quiet period (QP) method. However, even when using a QP, interference can occur. This causes reduced system throughput and contrary to the basic condition of cognitive radio. In order to reduce the interference time, a frequency-hopping algorithm is proposed here. Additionally, to complement the loss of throughput in the FH, a HMM-based channel prediction algorithm and a channel allocation algorithm is proposed. Simulations were conducted while varying several parameters. The findings show that the proposed algorithm outperforms conventional channel allocation algorithms.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.3-8
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• 2002

A new Modem technique - 8-state Superposed QAM(8SQAM) - for use in power and bandwidth limited digital communication system is proposed. The premodulation baseband signal of the 8SQAM system is a double-interval(2Ts) raised cosine pulse superposed with weighted single-interval(Ts) raised cosine pulse. The performance of the 8SQAM, in a nonlinearly amplified multi-channel environment with additive white Gaussian noise(AWGN), inter-symbol interference(ISI), inter-modulation(IM) and adjacent channel interference(ACI), is analyzed via computer simulation. The simulation result shows that the 8SQAM outperforms 8PSK by about 1.6㏈ at BER=$1\times10^{-4}$ when HPA IBO is 1㏈ and channel Spacing, ${\Delta}F$ is 0.417fb.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1997.11a
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• pp.407-415
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• 1997

In this paper, we apply a digital modulation scheme called Multi-Carrier CDMA (MC-CDMA) to the technique for cochannel interference cancellation using reference correlator, previously proposed. The cancellatoin method will be effective for reducing the interference components which are other users'signal components in a common channel, but fading effect of channel remains as the degrading factor of channel condition. For compensating it, MC-CDMA scheme is introduced to combat agianst the multipath fading. We analize above system and derive the average probability of error in AWGN and Rayleigh fading environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3A
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• pp.257-265
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• 2004

General closed-form expression is derived and analyzed for the exact bit error rate (BER) performance of the arbitrary rectangular Gray coded QAM signal in conjunction with maximal-ratio combining (MRC) diversity on frequency non-selective slow m-distributed Nakagami fading channel in the presence of co-channel interference. Numerical results demonstrate error performance improvement with the use of MRC diversity reception. The new expressions presented here are suitable for evaluating various cases of practical interest on wireless communication channels.

• Proceedings of the IEEK Conference
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• summer
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• pp.27-30
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• 2004

OFDMA is considered as one of the major candidates for broadband wireless access. The OFDMA signal is usually coherently demodulated, requiring the channel estimation which can be estimated using a known pilot signal. In multi-cell environment, the performance of channel estimation is mainly limited by intercell interference. It is desirable to use a pilot signal that can estimate the channel information robust to the intercell interference in the OFDMA uplink system. In this paper, we consider two types of pilot signal applicable to multi-cell OFDMA uplink systems: One is time-multiplexed pilot signal and the other is code­multiplexed pilot signal. Simulation results show that the code-multiplexed pilot is suitable for low mobility environment and time-multiplexed pilot is suitable for high mobility environment.

• International Journal of Internet, Broadcasting and Communication
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• v.5 no.1
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• pp.1-5
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• 2013

Co channel interference and adjacent channel interference of (WiBro) into Wireless LAN (WLAN) in TV White Spaces (TVWS) is evaluated through Spectrum Engineering Advanced Monte Carlo Analysis Tool (SEAMCAT) based on the Monte-Carlo simulation method. As a result, in the case of co channel interference, the minimum distance between WiBro Mobile Station (MS) and WLAN User Equipment (UE) should be 210 m to allow the maximum transmitter power of WiBro UE of 25 dBm. The transmit power of WiBro BS have to be reduced to -4.96 dBm.