• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1045-1049
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• 2001

Wireless LANs in the 2.4 ㎓ ISM- band create a new Electromagnetic Compatibility (EMC) problem. We investigated the interference characteristics between such wireless LANs in the case of identical systems, systems with different technical parameters for modulation and demodulation, and using a Gaussian noise source as a disturbance source. Experimental results show that higher throughput is obtained when adjacent wireless LANs use different systems, and that interference characteristics can be evaluated experimentally using a Gaussian noise source. Calculated BER characteristics for the interference agree with experimental measurements, indicating that this calculation method can be used for the design of the wireless LAN network to avoid interference. It is possible to construct an efficient wireless LAN network by combining different wireless LAN systems.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.203-204
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• 2008

A novel method using scaling down and restoration to reduce the PAPR of OFDM signal is proposed. This method shows a better BER performance than clipping method. And also the throughput efficiency is better than SLM.

• Journal of Advanced Navigation Technology
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• v.11 no.3
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• pp.274-280
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• 2007

An ultra-wideband signal is characterized by a radiated spectrum with wide bandwidth around a relatively low center frequency. In this paper, the bit error rate (BER), packet error rate (PER), and data throughput performance for an ultra-wideband system with M-ary correlation receiver are analyze in additive white Gaussian noise (AWGN) and co-channel interference channel. To evaluate the performance of UWB system, a set of UWB communication waveform as pulse position modulated (PPM) signals consisting of more than one UWB pulse is used. The M-ary PPM signals are defined to be equally correlated in order to simplify the system performance analysis. The analysis for system performance shows that the wireless channel error significantly degrades throughput performance and can be effectively increased by hybrid ARQ scheme. Also, an attempt for comparing the data throughput of ultra-wideband system on different performance improvement schemes and parameters has been made. From the performance evaluation process, it is shown that the effects of wireless channel and hybrid ARQ scheme for ultra wideband M-ary PPM system can be evaluated by means of a suitable combination of the PER, throughput vs. signal-to-noise power ratio per bit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.632-638
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• 2010

In this paper, we propose a fixed-complexity sphere encoder (FSE) for multi-user MIMO (MU-MIMO) systems. The Proposed FSE accomplishes a scalable tradeoff between performance and complexity. Also, because it has a parallel tree-search structure, the proposed encoder can be easily pipelined, leading to a tremendous reduction in the precoding latency. The complexity of the proposed encoder is also analyzed, and we propose two techniques that reduce it. Simulation and analytical results demonstrate that in a $4\times4$ MU-MIMO system, the complexity of the proposed FSE is 16% that of the conventional QRD-M encoder (QRDM-E). Also, the encoding throughput of the proposed endoder is 7.5 times that of the QRDM-E with tolerable degradation in the BER performance, while achieving the optimum diversity order.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.951-959
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• 2011

The low power consumption modulation is required for short range communication. In this paper, we analyze performance of low power consumption modulation scheme such as PSPM, PSSK and QAPM using OFDM transmission in AWGN channel. A PSPM, PSSK and QAPM modulation scheme are decrease in bandwidth efficiency but improved power efficiency than existing PSK and QAM. These modulation schemes can achieve power efficiency because every symbol of modulations has a zero-envelope period like PPM techniques. The OFDM system is high bandwidth efficiency than single carrier system. In this paper, we are propose the frequency domain mapping method for OFDM transmission using low power consumption modulation method. Also, we compare low power OFDM communication system regard to BER performance, throughput and PAPR.

• Journal of Digital Contents Society
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• v.9 no.1
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• pp.1-6
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• 2008

In traditional wireless communication systems the main power consumption is due to the actual transmissions power. Therefore, energy-constrained wireless networks have gained considerable research attention in recent years. Multiple-input-multiple-output (MIMO) structure, or multiple antenna communication is one of the techniques that has gain considerable importance in wireless systems and networks. In this paper, BER and throughput performance of MISO system with Go-back-N ARQ(Automatic Repeat Request) technique in wireless networks are analyzed and the energy consumption of MISO-based wireless networks is compared with conventional SISO-based wireless networks. Obtained results show the applicability of MISO system with Go-back-N ARQ technique in wireless networks with smart system design.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.212-219
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• 2006

In this paper, a new turbo codes-based hybrid automatic repeat request (TC-HARQ) scheme with segment selective repeat (SSR) is proposed. The main strategy is, upon retransmission, to repeat the data that are most important for the next round of decoding based on the distribution of residual errors after current decoding. The performance in terms of reliability and throughput is analyzed. To adapt to correlated fading channels where an inter-leaver is always employed before transmission, we further modify the SSR strategy so that data having experienced correlated deep fading are selected for retransmission. Finally, this proposed scheme is applied to the wideband code division multiple access (WCDMA) system under frequency selective fading channels. Simulation results demonstrate that in all single and multiple user cases, SSR-based TC-HARQ leads to significant throughput improvement with similar bit error rate (BER) performance as compared to type-I TC-HARQ.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.104-110
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• 2008

In this paper, a novel 2-level-search sphere decoding algorithm for multiple-input multiple-output (MIMO) detection and its VLSI implementation are presented. The proposed algorithm extends the search space by concurrently performing symbol detection on 2 level of the tree search. Therefore, the possibility of discarding good candidates can be avoided. Simulation results demonstrate the good performance of the proposed algorithm in terms of bit-error-rate (BER). From the proposed algorithm, an efficient very large scale integration (VLSI) architecture which incorporates low-complexity and fixed throughput features is proposed. The proposed architecture supports many modulation techniques such as BPSK, QPSK, 16-QAM and 64-QAM. The sorting block, which occupies a large portion of hardware utilization, is shared for different operating modes to reduce the area. The proposed hardware implementation results show the improvement in terms of area and BER performance compared with existing architectures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.113-119
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• 2009

The training sequence with the appropriate length for equalization and initial synchronization is necessary before sending the pure data in the burst transmission type DS-UWB system. The length of the training sequence is one of the factors which make throughput decreased. The noble structure with the variable length of the training sequence whose length can be adaptively tailored according to the channel conditions (CM1,CM2,CM3,CM4) in the DS-USB systems is proposed. This structure can increase the throughput without sacrificing the performance than the method with fixed length of training sequence considering the worst case channel conditions. Simulation results under IEEE 802.15.3a channel model show that the proposed scheme can achieve higher throughput than a conventional one with the slight loss of BER performance. And this structure can reduce the computation complexity and power consumption with selecting the short length of the training sequence.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.3
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• pp.31-38
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• 2010

In this paper, we have analyzed and compared the BER and the throughput performance through the computer simulation, after applying several MIMO schemes on the MIMO-OFDM system. Then, the throughput performance of the proposed system, Adaptive-MCM, is analyzed. As a result, the MIMO-OFDM Adaptive-MCM system proposed has a higher average data rate than Non Adaptive-MCM system through the improvement of Trade-off problem between throughput and SNR.