• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
• /
• pp.109-112
• /
• 2001

Recently, as demands for super-high speed broad band wireless multimedia service increase, variable researches to develop wireless LAN have been carried out. In this paper, we propose and analyze LS(Least Squares)-PSA(Pilot Symbol Assisted) equalizer which compensates for each subcarrier of different attenuations and phase response for OFDM(Orthogonal Frequency Division Multiplexing)-based indoor wireless LAN systems. The proposed equalizer enhances the $E_{b}$ $N_{o}$ performance of 3dB and 4dB at BER=10$^{-2}$ as compared with LS equalizer in AWGN channel and indoor wireless channel respectively..

• 한국통신학회논문지
• /
• 제33권2A호
• /
• pp.198-203
• /
• 2008

In this paper, we consider the diffuse type of indoor wireless optical communication (WOC) system. To find the channel characteristics of indoor wireless infrared communication system, we investigate the simulation process to get the impulse response of diffuse type and analyze the scenario of the indoor structure which we have built. The simulation results of the impulse response include power ratio and time delay due to bounce times. We get and discuss the receiving power distribution according to six configurations which have different transmitter and receiver positions and reflection coefficients of the indoor structure assumed. The results of this paper are useful to design the indoor wireless optical communication systems.

• 정보통신설비학회논문지
• /
• 제11권1호
• /
• pp.16-22
• /
• 2012

Wireless data communication is easy to be affected by channel noise and degrade reliability and stability by the multipath fading and ISI compared with wired data communication. In this paper, we designed and implemented indoor wireless modem adopted DQPSK modulation scheme for improvement of bandwidth efficiency, and convolutional encoding, Viterbi decoding and hybrid ARQ algorithm combinig FEC with CRC for efficient error control in indoor wireless channel. Testing the implemented wireless modem, we verified the proposed scheme is proper to efficient and reliable indoor wireless data communication.

• 방송공학회논문지
• /
• 제14권5호
• /
• pp.650-653
• /
• 2009

Turbo-coded CDMA system is analyzed and simulated in an indoor wireless infrared channel. The indoor infrared channel is modeled as a non-directed diffuse link. From the simulation results, it is confirmed that the turbo coding is very effective in improving BER (bit error rate) performance, and outperforms BCH code.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
• /
• pp.213-216
• /
• 2000

In this paper, performance of a CDMA-based packet transmission system is analyzed and simulated in a wireless infrared channel. The indoor wireless infrared channel is modeled as a non-directed diffuse link. The pulse position modulation (PPM) is used as a modulation scheme. From the simulation results, it is shown that the RS coding is very effective in improving the packet-delay characteristics of the CDMA-based packet transmission system. The performance improvement is more significant especially when the infrared channel is in a worse condition.

• 한국통신학회논문지
• /
• 제30권5C호
• /
• pp.355-363
• /
• 2005

이 논문은 옥내와 옥외에 걸친 무선 통신 환경에서 통신 성능을 향상시키는 기술에 관한 것이다. 옥외 무선 통신에서 신호 감쇠는 주로 채널의 페이딩 특성으로 발생되는데, 기존의 다중 안테나 방식과 배열 신호처리 알고리즘을 적용하면 이 문제를 해결할 수 있다. 그러나, 옥내 및 옥외 무선 채널을 가진 통신인 경우, 채널 특성은 페이딩과 각도 퍼짐 특성 모두에 영향을 받으므로, 일반적인 방식으로 채널의 각도 퍼짐 특성을 극복할 수 없다. 이를 해결하기 위해 이 논문에서는 옥내와 옥외에 걸친 채널 특성을 분석하고, 각각에 적합한 채널 모형을 생각한다. 또한, 옥내외 채널의 각도 퍼짐 특성을 극복하고 옥내외 통신 성능을 향상하기 위해, 새로운 평균주사 벡터 개념을 사용한 배열 안테나 처리 알고리즘을 제안하고 성능 분석을 수행한다. 컴퓨터 모의 실험을 통한 성능 분석으로 옥내 전송 신호를 옥외 환경에서 다중 안테나로 수신하는 경우, 기존 방식보다 제안된 방식이 좋은 신호대 간섭 잡음비 특성을 가짐을 보인다.

• 한국컴퓨터정보학회논문지
• /
• 제13권5호
• /
• pp.179-186
• /
• 2008

무선 센서 네트워크의 응용범위가 늘어남에 따라 정확한 무선 채널의 정보를 필요로 한다. 실내 또는 실외의 무선 센서 네트워크의 경우 페이딩에 의한 다중 경로 전파가 문제를 일으키고 있다. 본 논문에서는 실내 2.4 GHz 채널에 대한 log-normal path loss 모델링을 살펴본다. 송신기와 수신기 사이의 거리를 1에서 30m까지 변화시키면서 수신 신호 강도 변화를 측정하고, 채널의 감쇄지수와 표준편차를 계산하였다. 계산한 모델의 패킷 수신율을 이용하여 무선 센서 채널을 연결 영역과 차단 영역으로 정의하고, 시뮬레이션과 실험 결과를 통해서 무선 채널의 특징을 비교하였다. 실험결과 실내에서의 연결 영역은 24m, 실외에서의 연결 영역은 14m로 측정되었다.

• ETRI Journal
• /
• 제34권3호
• /
• pp.319-329
• /
• 2012

Closed-loop transmit diversity is considered an important technique for improving the link budget in the third generation and future wireless communication standards. This paper proposes several transmit diversity algorithms suitable for small wireless terminals and presents performance assessment in terms of average signal-to-noise ratio (SNR) and outage improvement, convergence, and complexity of operations. The algorithms presented herein are verified using data from measured indoor channels with variable antenna spacing and the results explained using measured radiation patterns for a two-element array. It is shown that for a two-element array, the best among the proposed techniques provides SNR improvement of about 3 dB in a tightly spaced array (inter-element spacing of 0.1 wavelength at 2 GHz) typical of small wireless devices. Additionally, these techniques are shown to perform significantly better than a single antenna device in an indoor channel considering realistic values of latency and propagation errors.

• 한국정보통신설비학회:학술대회논문집
• /
• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
• /
• pp.39-42
• /
• 2008

In this paper, we analyze the performance of ultra wide band (UWB) systems in indoor wireless channel in accordance with the number of pulses per bit at transmit signals and the decision types of receiver. The indoor channel is modeled as the modified Saleh and Valenzuela (SV) model which has been proposed as a UWB channel model by the IEEE group, IEEE 802.15.SG3a. Two types of UWB signals are considered One is the pulse position modulation-time hopping (PPM-TH) signal. And the other is the pulse amplitude modulation-direct sequence (PAM-DS) signal. It is assumed that the receiver is an ideal receiver which can receive all signals of the multipath.

• 한국정보통신설비학회:학술대회논문집
• /
• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
• /
• pp.30-34
• /
• 2008

In this paper, we analyze the performance of pulse position modulation-time hopping ultra wide band (PPM-TH UWB) systems with antenna diversity technique in indoor wireless channel. A modified Saleh and Valenzuela (SV) model is adopted as a UWB indoor channel model. Perfect synchronization between a transmitter and a receiver is assumed. Therefore, coherent equal gain combining (EGC) scheme to collect the energy available in the multipath components is investigated. It is shown that the performance is improved by increasing the number of antennas at the receiver. The results of this paper can be applied to the applications of UWB.