• 한국정보통신설비학회:학술대회논문집
• /
• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
• /
• pp.253-256
• /
• 2008

In this paper, we analyze the performance of RAKE receiver for impulse radio-ultra wide band (IR-UWB) systems in indoor multipath radio channel. Pulse position modulation-time hopping (PPM-TH) signal is considered. And we also consider three types of RAKE receivers, which are ideal RAKE, selective RAKE, and partial RAKE receivers. 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.

• Journal of information and communication convergence engineering
• /
• 제2권3호
• /
• pp.139-144
• /
• 2004

In order to transmit various types of multimedia data (i.e. voice, video, and data) over a wireless channel, the coding and modulation scheme needs to be flexible and capable of providing a variable quality of service, data rates, and latency. In this paper, we study a mobile multimedia COMA network combined with the concatenated Reed-Solomon/Rate Compatible Punctured Convolution code (RS/RCPC). Also, this paper propose the combination of concatenated RS/RCPC coder and COMA RAKE receiver for multimedia COMA traffic which can be sent over wireless channels. From the results, using a frequency selective Rayleigh fading channel model, it is shown that concatenated RS/RCPC coder at the wireless physical layer can be effective in providing reliable wireless multimedia CDMA network. And the proposed scheme that combine concatenated RS/RCPC coder and CDMA RAKE receiver provides a significant gain in the BER performance over multi-user interference and multipath frequency selective fading channels.

• 한국인터넷방송통신학회논문지
• /
• 제10권3호
• /
• pp.179-184
• /
• 2010

본 논문에서, 실내 다중 경로 무선 채널에서 초광대역(UWB: ultra wide band) 시스템을 위한 레이크 수신기의 성능을 분석한다. 펄스 위치-시간 도약(PPM-TH: pulse position modulation-time hopping) 신호가 고려되었다. 그리고 또한 이상적인 레이크, 선택적 레이크, 부분적 레이크 수신기 등의 세 종류의 레이크 수신기를 고려한다. 실내 채널은 IEEE 802.15.SG3a에서 UWB 채널 모델로 제안한 수정된 SV (Saleh and Valenzuela) 모델로 모델링하였다.

• 한국위성정보통신학회논문지
• /
• 제7권2호
• /
• pp.59-66
• /
• 2012

주파수선택성 패이딩 채널 상황에서 Pre-Rake 다이버시티 기술은 이동단말에게 충분한 다이버시티 효과를 제공하며 이동단말의 수신기가 단순한 구조가 되도록 도와준다. 하지만, 기존의 Pre-Rake 시스템은 주파수선택성 페이딩 환경에서 Rake 시스템보다 두 배에 가까운 멀티패스에 의해 영향을 받기 때문에 다중유저 간섭을 Rake 시스템보다 훨씬 더 심각하게 받게 된다. 결국 이와 같은 간섭은 사용자가 증가할수록 성능이 열화하게 되는 원인이 된다. 따라서 이러한 문제점을 해결하기 위해 본 논문에서는 ZCD (Zero Correlation Code) 확산코드를 이용한 Pre-Rake TDD-CDMA 시스템을 제안한다. 또한 GI (Guard interval)를 포함하는 수정된 ZCD 코드들을 제시하고 다양한 채널환경에서 컴퓨터 시뮬레이션을 수행하고 그 성능을 평가한다.

• Journal of Communications and Networks
• /
• 제14권5호
• /
• pp.501-509
• /
• 2012

This paper proposes a joint timing synchronization, channel estimation, and data detection for the impulse radio ultra-wideband systems. The proposed timing synchronizer consists of coarse and fine timing estimation. The synchronizer discovers synchronization points in two stages and performs adaptive threshold based on the maximum pulse averaging and maximum (MAX-PA) method for more precise synchronization. Then, iterative channel estimation is performed based on the discovered synchronization points, and data are detected using the selective rake (S-RAKE) detector employing maximal ratio combining. The proposed synchronizer produces two signals-the start signal for channel estimation and the start signal for start frame delimiter (SFD) detection that detects the packet synchronization signal. With the proposed synchronization, channel estimation, and SFD detection, an S-RAKE receiver with binary pulse position modulation binary phase-shift keying modulation was constructed. In addition, an IEEE 802.15.4a channel model was used for performance comparison. The comparison results show that the constructed receiver yields high performance close to perfect synchronization.

• Journal of Communications and Networks
• /
• 제14권5호
• /
• pp.518-523
• /
• 2012

This paper presents new coherent and non-coherent detection methods for the IEEE 802.15.4a low-rate ultra-wideband physical layer with forward error correction (FEC) coding techniques. The coherent detection method involving channel estimation is based on the correlation characteristics of the preamble signal. A coherent receiver uses novel iterated selective-rake (IT-SRAKE) to detect 2-bit data in a non-line-of-sight channel. The non-coherent detection method that does not involve channel estimation employs a 2-bit data detection scheme using modified transmitted reference pulse cluster (M-TRPC) methods. To compare the two schemes, we have designed an IT-SRAKE receiver and a MTRPC receiver using an IEEE 802.15.4a physical layer. Simulation results show the performance of IT-SRAKE is better than that of the M-TRPC by 3-9 dB.

• 한국통신학회논문지
• /
• 제25권4B호
• /
• pp.635-639
• /
• 2000

상관도가 있는 주파수 선택적 나까가미 페이딩 채널에서의 2D-RAKE 수신기의 평균 비트 에러율을 구하여 성능을 분석하였다. 동일한 RAKE 핑거의 배열 안테나에 수신되는 신호들은 동일한 페이ELD 파라메터를 가지지만 서로 다른 평균 신호 대 잡음비를 갖는 것으로 가정하였다. 또한 서로 다른 RAKE 핑거에 수신되는 신호들은 서로 독립적이지만 서로 다른 평균 신호 대 잡음비를 가지고 서로 다른 페이딩 파라메터를 갖는다고 가정하였다. 위의 분석을 통하여 결합되는 다이버시티 브랜치 간의 상관 특성, 지연 확산 특성, 평균 신호 대 잡음비 분포 그리고 페이딩 파라메터들이 2D-RAKE 수신기의 성능에 밀접한 영향을 줌을 확인하였다.

• 전자공학회논문지A
• /
• 제33A권4호
• /
• pp.37-46
• /
• 1996

In this paper, we analyzed the performance improvement of the DS-CDMA/dPSK cellular mobile communication system with CCI canceller and RAKE receiver techniques in mobile radio channel which is characterized by AWGN, Multi-user interference (mUI) and frequency-selective rayleigh fading. System capacity i.e., number of user per cell has been derived and the evaluated results are shown in figuraes as a function of PN code sequence length, number of RAKE receiver tap, BER and E$_{b}$/N$_{o}$. The voice activity factor is assumed to be 3/8 the number of sectors in a cell 3 and MUI is modeled as gaussian process. From the results, the capacity of the DS-CDMA/DPSK cellular mobile communication system is improved by adopting CCI canceller. When we adopt the RAKE receiver to mitigate the multipath fading, the error performance is improved and the amount of improvement is proportional ot the number of taps L in the case that each tap contains a signal component and the better of improvement can be obtained, the smaller of the SNR difference in each tap. The system capacity is more increased when the CCI canceller and the RAKE receiver is used in cascade.

• 한국통신학회논문지
• /
• 제25권3A호
• /
• pp.353-361
• /
• 2000

The performance of a multi-carrier CDMA system is analyzed considering frequency selective multipath fading and Near/Far effects. The number of multicarrier, multiuser, and arms of RAKE receiver, and the decay ratio of frequency selective multipath fading are used as a parameter for the performance analysis. More over, the distribution and the strength of multiuser interference are also considered. To evaluated the Near/Far effects in a multi-carrier CDMA system, three distribution models are assumed. In the first model. interference to carrier Ratio, I/C, ranges form -4 dB to 4dB, and at each 2 dB interval 20 % of multiuser is assumed to be uniformly distributed. In the second one, I/C ranges from -2 dB to 2 dB, and 33.3% of multiuser is assumed to be equally dispersed at each 2dB interval. The third model is 0 dB of I/C, that is, with perfect power control, multiuser are assumed to be evenly located. In this paper, multi-carrier CDMA system adoption RAKE receiver is proposed to mitigate the frequency selective multipath fading. Form the results, the third model(i.e. perfect power control)shows the best performance, and the narrower range of I/C causes the less effects to the desired signal, which reads to the better performance.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2005년도 추계종합학술대회
• /
• pp.209-212
• /
• 2005

In this paper, based on a detection criterion proposed recently, we investigate the performance of selective rake receivers (SRRs) in fading environment exhibiting impulsive nature. Optimum and suboptimum SRRs for the impulsive fading channel are derived, and suboptimum SRRs with reduced complexity are obtained for practical purposes. Simulation results confirm that, when the noise is impulsive the SRRs designed for impulsive noise offer performance improvement over those optimized for Gaussian environment. The suboptimum SRR is observed to exhibit almost the same performance as the optimum SRR.