• Title/Summary/Keyword: beamforming techniques

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Computational Complexity Analysis of Cascade AOA Estimation Algorithm Based on FMCCA Antenna

  • Kim, Tae-yun;Hwang, Suk-seung
    • Journal of Positioning, Navigation, and Timing
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    • v.11 no.2
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    • pp.91-98
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    • 2022
  • In the next generation wireless communication system, the beamforming technique based on a massive antenna is one of core technologies for transmitting and receiving huge amounts of data, efficiently and accurately. For highly performed and highly reliable beamforming, it is required to accurately estimate the Angle of Arrival (AOA) for the desired signal incident to an antenna. Employing the massive antenna with a large number of elements, although the accuracy of the AOA estimation is enhanced, its computational complexity is dramatically increased so much that real-time communication is difficult. In order to improve this problem, AOA estimation algorithms based on the massive antenna with the low computational complexity have been actively studied. In this paper, we compute and analyze the computational complexity of the cascade AOA estimation algorithm based on the Flexible Massive Concentric Circular Array (FMCCA). In addition, its computational complexity is compared to conventional AOA estimation techniques such as the Multiple Signal Classification (MUSIC) algorithm with the high resolution and the Only Beamspace MUSIC (OBM) algorithm.

The OFDMA/TDD System based on Transmit and Receive Beamforming Utilizing the Preamble for Receive Beamforming (수신 빔형성 프리앰블을 이용한 송수신 빔형성 기반 OFDMA/TDD 시스템)

  • Heo, Joo;Chang, Kyung-Hi
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.9A
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    • pp.749-754
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    • 2005
  • It is well-known that mobile communication systems are usually limited in their performance and capacity by three major impairments, which are multipath fading, delay spread and co-channel interference (CCI). OFDMA (OFDM-FDMA) system can cope with the multipath fading and delay spread easily due to the beneficial properties of OmM technology. Though OFDMA scheme avoids intra-cell interference using the orthogonality among subcarriers, the scheme contains difficulty of reducing co-channel interference. Therefore, in this paper, adaptive antenna techniques are deployed into OFDMA/TDD system to minimize the co-channel interference induced by adjacent cells and to enhance the uplink performance. For the improvement of downlink performance, we apply TxAA (Transmit Adaptive Array), a kind of transmit diversity technique, utilizing preamble symbols for training antenna may into OFDMA/TDD transmitter side. Simulation results show that the uplink and downlink performance under multipath Rayleigh fading channel improved 9dB and 7dB each compared with the case of single antenna system at target BER $10^{-3}$ .

Comparison Study of Beam Pattern for FDD downlink CDMA Signals (FDD에서 하향링크 CDMA신호의 빔패턴 비교 연구)

  • Kim, Sang-Choon;Son, Kyung-Soo;Ha, Joo-Young;Lee, Sung-Mok;Jang, Won-Woo
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.2
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    • pp.358-365
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    • 2007
  • In this paper, the effects of transmit beamforming on downlink performance in DS-CDMA communication systems are investigated. The uplink and downlink in FDD systems use different carrier frequencies. If the downlink uses the same weighting vectors as the uplink, the antenna beam for downlink is formed with certain DOA shift and it thus affects the beamforming gain. So, the impacts of different frequencies on the downlink beam patterns are studied. One possible algorithm to convert uplink beamforming weights to downlink, which is called frequency-calibrated processing, is also evaluated to reduce the degradation of downlink performance due to different frequencies. Under frequency selective channels, the downlink chooses a PUPW beamforming scheme when the uplink employs a PPPW vectors. To form a beam pattern for a PUPW after combining the downlink PPPWs converted from the uplink PPPWs, three approaches are studied. One method is to consider only one dominant path and thus obtain a single main-beam. In the others, multiple-beams weighted with the magnitudes of all paths and equally weighted with all paths are constructed.

Sixth-Generation Networks and Integrated Sensing and Communications (6G 통신에서의 센싱과 통신의 결합 서비스(ISAC))

  • D.M. Baek;T.Y. Kim
    • Electronics and Telecommunications Trends
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    • v.38 no.6
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    • pp.107-118
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    • 2023
  • Sixth-generation (6G) networks may allow to evolve from everything connected to everything sensed. Integrated sensing and communications (ISAC) requires the higher frequencies, wider bands, and more advanced antenna technology offered by 6G technology. We analyze advanced beamforming techniques to overcome the poor propagation characteristics of millimeter and terahertz waves as well as new waveforms designed to include sensing. This paper is intended to provide communication researchers with short summaries of ISAC, use cases, and standardization initiatives as guidelines for exploring new research and development directions.

Determination and Performance Evaluation of Codevectors Utilizing Phase Difference Distribution Characteristics of Circular Antenna Arrays (원형 안테나 배열의 위상 차이 분포 특성을 활용한 코드벡터 결정 방식 및 성능 평가)

  • Kim, Huiwon;Suh, Junyeub;Sung, Wonjin
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.10
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    • pp.3-9
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    • 2016
  • Current mobile communication systems utilize the multiple-input multiple-output (MIMO) transmission technique as an important means to enhance the bandwidth efficiency. Accurate beamforming via channel estimation contributes to the signal-to-interference-plus-noise ratio (SINR) increase and the system performance improvement when MIMO transmission techniques are employed. Therefore, determination of beamforming vectors as well as the design of appropriate codebooks defining these codevectors play an important role in system operation. In this paper, we statistically analyze the phase difference between the channels corresponding to adjacent antenna elements in order to design an efficient codebook for uniform circular arrays (UCAs). We introduce new parameters which compensate for the additional phase difference observed in its probability density functions (PDFs). The performance of the proposed codebook is tested using the spatial channel model (SCM) to demonstrate its gain over the standard codebooks adopted in the long term evolution (LTE) Releases 8 and 10.

A Beamforming Method for a Perturbed Linear Towed Array (비선형 형상 견인 어레이를 위한 빔형성 기법)

  • 김승일;도경철;오원천;윤대희;이충용
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.5
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    • pp.478-484
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    • 2002
  • Linear towed arrays (LTA) have a nonlinear shape due to tow vessel motion, ocean swells and currents. By reasons of nominally linear shape, various towed array shape estimation techniques have been developed since the perturbed shape cause the error in target detection. In this paper,, we propose the beamforming method for the perturbed LTA with simple structure. The proposed method linearizes a nonlinear phase of steering vector with position information measured by two reference sensors. It can be proved using some properties of Markov transition matrix, and iteration number of linearization process is decided by variance of cross phase difference. As a result of computer simulation in the ocean environment, beampattern of the proposed method is almost same with the ideal case in my type of array shape. In the signal-to-noise ratio (SNR) performance simlation, the DOA estimation performance of the proposed beamforming method is evaluated, and the comparison with Bartlett beamformer of the LTA shows that the proposed method can estimate. the spatial characteristic of sources more accuracy.

Performance Evaluation of Beamformer for STBC-OFDM Systems (STBC-OFDM 시스템에서 빔형성 기법의 성능평가)

  • 이상문;최형진
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.6C
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    • pp.883-892
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    • 2004
  • Recently, in order to improve high speed data transmission and spectral efficiency in wireless communication systems, the study on the combination OFDM and space-time coding is active. Also, a solution to improve system capacity in multiuser systems is to use adaptive antennas. In a system using STBC, the signals transmitted from two transmit antennas are superposed at the receive antenna and the interference between two transmit antennas of a user occures. Thus it is difficult to apply the conventional beamforming techniques for single antenna to the systems using space-time coding. In this Paper, we present the MMSE beanforming technique using training sequence for STBC-OFDM systems in reverse link and evaluate the performance by using various parameters in TU and HT channels.

Mitigation of Inter-Symbol Interference in Underwater Acoustic Communication Using Spatial Filter (공간 필터를 이용한 수중음향통신의 인접 심볼 간 간섭 완화)

  • Eom, Min-Jeong;Park, Ji-Sung;Ji, Yoon-Hee;Kim, J.S.
    • The Journal of the Acoustical Society of Korea
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    • v.33 no.1
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    • pp.48-53
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    • 2014
  • The underwater acoustic communication (UAC) is characterized by doubly spread channel. It is included in the time-variant doppler shift and delay-time spreads due to multiple paths. To compensate such distorted signals, various techniques including time-reversal processing, spatial diversity, phase estimator, and equalizer are being applied. In this paper, a spatial filter based on the beamforming is proposed as a method to mitigate such inter-symbol interferences that are generated in time-varying multipath channels. The proposed technique realizes coherent communications by steering the direction of the desired signals and improves the performance of UAC by increasing the signal-to-interference plus noise ratio using the array gain.

Ultrasound Synthetic Aperture Beamformer Architecture Based on the Simultaneous Multi-scanning Approach (동시 다중 주사 방식의 초음파 합성구경 빔포머 구조)

  • Lee, Yu-Hwa;Kim, Seung-Soo;Ahn, Young-Bok;Song, Tai-Kyong
    • Journal of Biomedical Engineering Research
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    • v.28 no.6
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    • pp.803-810
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    • 2007
  • Although synthetic aperture focusing techniques can improve the spatial resolution of ultrasound imaging, they have not been employed in a commercial product because they require a real-time N-channel beamformer with a tremendously increased hardware complexity for simultaneous beamforming along M multiple lines. In this paper, a hardware-efficient beamformer architecture for synthetic aperture focusing is presented. In contrast to the straightforward design using NM delay calculators, the proposed method utilizes only M delay calculators by sharing the same values among the focusing delays which should be calculated at the same time between the N channels for all imaging points along the M scan lines. In general, synthetic aperture beamforming requires M 2-port memories. In the proposed beamformer, the input data for each channel is first upsampled with a 4-fold interpolator and each polyphase component of the interpolator output is stored into a 2-port memory separately, requiring 4M 2-port memories for each channel. By properly limiting the area formed with the synthetic aperture focusing, the input memory buffer can be implemented with only 4 2-port memories and one short multi-port memory.

Code-Book Based Beamforming Techniques for Improving SIR (코드북 기반 SIR 향상 빔 형성 기법)

  • Ahn, Jongmin;Lee, Dongkyu;Park, Chul;Kim, Hanna;Chung, Jaehak
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.8
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    • pp.1469-1476
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    • 2015
  • We propose a beam selection algorithm that improves inter sector SIR using a code-book of a circular array antenna in multi-sector wireless mesh network environments. The proposed method improves SIR using a combination of fed back code-book and guarantees QoS of all nodes. Computer simulation exhibits the proposed scheme demonstrates 4.42dB higher SIR than that of the conventional code-book method, QoS with proportional fair is improved by 1.70dB and fact that all nodes are satisfied Qos is also shown.