• Title/Summary/Keyword: Multi-Path Gain Method

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A Study on performance improvement of MMSE Multi-User Detector (MMSE 다중사용자 검출기의 성능 향상에 관한 연구)

  • Yoo, Dong-Kwan
    • Journal of the Korea Society of Computer and Information
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    • v.12 no.1 s.45
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    • pp.145-154
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    • 2007
  • In this paper, an improved detection method is proposed by supplementing various types of Multi-Path gam for a MMSE Multi-User detecter. This method is proposed to complement the shortcomings of the conventional detection method which is used for multiuser detection in STBC(Space-Time Block Code) CDMA system. We analyzed the improved method in bit error probability viewpoint and compared the result with that of the conventional method. In this result, we showed that the improved method obtains better performance of bit error probability than the conventional method when parameters such as delay, number of user and SNR are changed.

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A Study on the Multi-Path Gain Adaptive MMSE Detector (다중경로 이득 적응형 MMSE 검출기에 관한 연구)

  • 유동관
    • Journal of the Korea Society of Computer and Information
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    • v.9 no.2
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    • pp.89-96
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    • 2004
  • In this paper, an improved method is proposed by supplementing multi-path gain for detection. This method is proposed to complement the shortcomings of the conventional detection method which is used for multiuser detection in STBC(Space-Time Block Code) CDMA system. We analyzed the improved method in bit error probability viewpoint and compared the result with that of the conventional method. From this result, we showed that bit error probability of the improved method is superior to that of the conventional method when the parameters such as delay, number of user and SNR are increased.

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A Study on the performance improvement of Multi-Path Gain in a MMSE Detector (MMSE 검출기에서 다중경로 이득 개선에 관한 연구)

  • Yoo Dong-Kwan
    • Journal of the Korea Society of Computer and Information
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    • v.10 no.2 s.34
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    • pp.153-158
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    • 2005
  • In this paper, an improved detection method is Proposed by supplementing multi-path gain for a MMSE detecter. This method is Proposed to complement the shortcomings of the conventional detection method which is used for multiuser detection in STBC CDMA system. We analyzed the improved method in bit error Probability viewpoint and compared the result with that of the conventional method In this result, we showed that the improved method obtains better performance of bit error probability than the conventional method when parameters such as delay, number of user and SNR are increased.

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EKF based Mobile Robot Indoor Localization using Pattern Matching (패턴 매칭을 이용한 EKF 기반 이동 로봇 실내 위치 추정)

  • Kim, Seok-Young;Lee, Ji-Hong
    • The Journal of Korea Robotics Society
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    • v.7 no.1
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    • pp.45-56
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    • 2012
  • This paper proposes how to improve the performance of CSS-based indoor localization system. CSS based localization utilizes signal flight time between anchors and tag to estimate distance. From the distances, the 3-dimensional position is calculated through trilateration. However the error in distance caused from multi-path effect transfers to the position error especially in indoor environment. This paper handles a problem of reducing error in raw distance information. And, we propose the new localization method by pattern matching instead of the conventional localization method based on trilateration that is affected heavily on multi-path error. The pattern matching method estimates the position by using the fact that the measured data of near positions possesses a high similarity. In order to gain better performance of localization, we use EKF(Extended Kalman Filter) to fuse the result of CSS based localization and robot model.

Performance Analysis of 1-2-1 Cooperative Protocol in Wireless Sensor Networks (무선 센서 네트워크에서 1-2-1 협력 프로토콜에 관한 연구)

  • Choi, Dae-Kyu;Kong, Hyung-Yun
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.8 no.5
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    • pp.113-119
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    • 2008
  • Conventional 1-1-1 cooperative protocol offers path-loss gain as advantage of multi-hop and spatial diversity which is equivalent to MIMO system. This protocol is enable to get higher reliability and reduction of power consumption than those of the single-hop or multi-hop. But the 1-1-1 cooperative protocol get only the diversity order 2 and limited path-loss reduction gain because this protocol has a single cooperative relay. We propose 1-2-1 cooperative protocol using two cooperative relays R1, R2. The 1-2-1 cooperative protocol can improve path-loss reduction and increase diversity order 3. Moreover, the cooperative relay R2 attains diversity order 2. The signaling method in transmission uses DF (Decode and Forward) or DR (Decode and Reencode) and 1-2-1 DF/DR cooperative protocol are applied to clustering based wireless sensor networks (WSNs). Simulations are performed to evaluate the performance of the protocols under Rayleigh fading channel plus AWGN (Additive White Gaussian Noise).

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Sparse Index Multiple Access for Multi-Carrier Systems with Precoding

  • Choi, Jinho
    • Journal of Communications and Networks
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    • v.18 no.3
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    • pp.439-445
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    • 2016
  • In this paper, we consider subcarrier-index modulation (SIM) for precoded orthogonal frequency division multiplexing (OFDM) with a few activated subcarriers per user and its generalization to multi-carrier multiple access systems. The resulting multiple access is called sparse index multiple access (SIMA). SIMA can be considered as a combination of multi-carrier code division multiple access (MC-CDMA) and SIM. Thus, SIMA is able to exploit a path diversity gain by (random) spreading over multiple carriers as MC-CDMA. To detect multiple users' signals, a low-complexity detection method is proposed by exploiting the notion of compressive sensing (CS). The derived low-complexity detection method is based on the orthogonal matching pursuit (OMP) algorithm, which is one of greedy algorithms used to estimate sparse signals in CS. From simulation results, we can observe that SIMA can perform better than MC-CDMA when the ratio of the number of users to the number of multi-carrier is low.

Performance Analysis of MC-DS/CDMA System with Phase Error and Hybrid SC/MRC-(2/3) Diversity (위상 에러와 하이브리드 SC/MRC-(2/3)기법을 고려한 MC-DS/CDMA 시스템의 성능 분석)

  • Kim Won-Sub;Park Jin-Soo
    • The KIPS Transactions:PartC
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    • v.11C no.6 s.95
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    • pp.835-842
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    • 2004
  • In this paper, we have analyzed the MC-DS/CDMA system with input signal synchronized completely through adjustment of the gain in the PLL loop, by using the hybrid SC/MRC-(2/3) technique, which is said to one of the optimal diversity techniques under the multi-path fading environment, assuming that phase error is defined to the phase difference between the received signal from the multi-path and the reference signal in the PLL of the receiver. Also, assuming that the regarded radio channel model for the mobile communication is subject to the Nakagami-m fading channel, we have developed the expressions and performed the simulation under the consideration of various factor, in the MC/DS-CDMA system with the hybrid SC.MRC-(2/3) diversity method, such as the Nakagami fading index(m), $the\;number\;of\;paths\;(L_p),$ the number of hybrid SC.MRC-(2/3) $diversity\;branches\;(L,\;L_c),$ the number of users (K), the number of subcarriers (U), and the gain in the PLL loop. As a result of the simulation, it has been confirmed that the performance improvement of the system can be achieved by adjusting properly the PLL loop in order for the MC/DS-CDMA system with the hybrid SC/MRC-(2/3) diversity method to receive a fully synchronized signal. And the value of the gain in the PLL loop should exceed 7dB in order for the system to receive the signal with prefect synchronization, even though there might be a slight difference according to the values of the fading index and the spread processing gain of the subcarrier.

Symbol Synchronization of OFDM Systems using Signs of Preamble Signals (훈련신호의 부호를 사용한 OFDM 시스템의 심볼동기)

  • 황진권
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.5A
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    • pp.502-513
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    • 2004
  • This paper proposes a symbol synchronization method in the IEEE 802.11a wireless OPDM system, which uses only signs of the in-phase and the quadrature signals in the short preamble. The short preamble is sampled with 2 tines of Nyquist sampling rate and both of the autocorrelation and the cross-relation are used in the proposed method. This method has some advantages that the ACG (Automatic Gain Control) can be processed concurrently during the short preamble and its implementation is not much complicated. The proposed symbol synchronization method is verified through simulations on frequency offset, multi-path and white Gaussian noise.

Single Carrier Frequency Domain Equalization in 3-slot Based Amplify-and-Forward Relaying Network for Shadow Area (음영 지역을 위한 3-슬롯 기반의 AF 방식 중계기 네트워크에서의 단일 반송파 주파수 대역 등화 기법)

  • Won, Hui-Chul
    • Journal of Korea Society of Industrial Information Systems
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    • v.17 no.7
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    • pp.9-16
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    • 2012
  • In order to extend cell coverage and to cope with shadow areas, a relay-assisted wireless communications system has been widely studied. In this paper, we propose new equalization method for single carrier (SC) frequency domain equalizer (FDE) in amplify-and-forward (AF) relaying multi-path networks to improve the performance at shadow areas. The performance of SC-FDE system in 3-slot based multi-path networks can be improved considerably with the diversity gain which we obtain by equalizing the combined signal from relays by means of the minimum mean square error (MMSE) criteria. We find the weighting coefficients of maximum ratio combining (MRC) and the tap coefficients of MMSE equalizer for SC-FDE in AF relaying multi-path networks. Simulation results show that the proposed system considerably outperforms the conventional SC-FDE system.

Beam Tracking Method Using Unscented Kalman Filter for UAV-Enabled NR MIMO-OFDM System with Hybrid Beamforming

  • Yuna, Sim;Seungseok, Sin;Jihun, Cho;Sangmi, Moon;Young-Hwan, You;Cheol Hong, Kim;Intae, Hwang
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.17 no.1
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    • pp.280-294
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    • 2023
  • Unmanned aerial vehicles (UAVs) and millimeter-wave frequencies play key roles in supporting 5G wireless communication systems. They expand the field of wireless communication by increasing the data capacities of communication systems and supporting high data rates. However, short wavelengths, owing to the high millimeter-wave frequencies can cause problems, such as signal attenuation and path loss. To address these limitations, research on high directional beamforming technologies continue to garner interest. Furthermore, owing to the mobility of the UAVs, it is essential to track the beam angle accurately to obtain full beamforming gain. This study presents a beam tracking method based on the unscented Kalman filter using hybrid beamforming. The simulation results reveal that the proposed beam tracking scheme improves the overall performance in terms of the mean-squared error and spectral efficiency. In addition, by expanding analog beamforming to hybrid beamforming, the proposed algorithm can be used even in multi-user and multi-stream environments to increase data capacity, thereby increasing utilization in new-radio multiple-input multiple-output orthogonal frequency-division multiplexing systems.