• Title/Summary/Keyword: Uplink signal

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The Performance Analyparkof Bandlimited WCDMA Systems (대역이 제한된 광대역 코드분할 다중화 시스템의 성능 분석)

  • Kim, Young-Sam;Park, Joong-Hoo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.4A
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    • pp.193-199
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    • 2003
  • In this paper, the performance of uplink WCDMA systems was analyzed using the SGA (Standard Gaussian Approximation) method and the SIGA(Simplified Improved Gaussian Approximation) method adopted for the performance analysis in conventional DS-CDMA systems. The performance of bandlimited WCDMA systems was analyzed using the SGA and SIGA method, and computer simulations were performed in AWGN environments having multiple access interference. It was shown that the performance analysis of uplink bandlimited WCDMA systems using the SIGa method may be very efficient through various computer simulations with verying spreading factors, roll-off factors, and signal-to-noise ratios.

Implementation of LTE uplink System for SDR Platform using CUDA and UHD (CUDA와 UHD를 이용한 SDR 플랫폼 용 LTE 상향링크 시스템 구현)

  • Ahn, Chi Young;Kim, Yong;Choi, Seung Won
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.9 no.2
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    • pp.81-87
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    • 2013
  • In this paper, we present an implementation of Long Term Evolution (LTE) Uplink (UL) system on a Software Defined Radio (SDR) platform using a conventional Personal Computer (PC), which adopts Graphic Processing Units (GPU) and Universal Software Radio Peripheral2 (USRP2) with URSP Hardware Driver (UHD) for SDR software modem and Radio Frequency (RF) transceiver, respectively. We have adopted UHD because UHD provides flexibility in the design of transceiver chain. Also, Cognitive Radio (CR) engine have been implemented by using libraries from UHD. Meanwhile, we have implemented the software modem in our system on GPU which is suitable for parallel computing due to its powerful Arithmetic and Logic Units (ALUs). From our experiment tests, we have measured the total processing time for a single frame of both transmit and receive LTE UL data to find that it takes about 5.00ms and 6.78ms for transmit and receive, respectively. It particularly means that the implemented system is capable of real-time processing of all the baseband signal processing algorithms required for LTE UL system.

Low-Complexity Distributed Algorithms for Uplink CoMP in Heterogeneous LTE Networks

  • Annavajjala, Ramesh
    • Journal of Communications and Networks
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    • v.18 no.2
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    • pp.150-161
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    • 2016
  • Coordinated multi-point transmission (CoMP) techniques are being touted as enabling technologies for interference mitigation in next generation heterogeneous wireless networks (HetNets). In this paper, we present a comparative performance study of uplink (UL) CoMP algorithms for the 3GPP LTE HetNets. Focusing on a distributed and functionally-split architecture, we consider six distinct UL-CoMP algorithms: 1. Joint reception in the frequency-domain (JRFD) 2. Two-stage equalization (TSEQ) 3. Log-likelihood ratio exchange (LLR-E) 4. Symmetric TSEQ (S-TSEQ) 5. Transport block selection diversity (TBSD) 6. Coordinated scheduling with adaptive interference mitigation (CS-AIM) where JRFD, TSEQ, S-TSEQ, TBSD and CS-AIM are our main contributions in this paper, and quantify their relative performances via the post-processing signal-to-interference-plus-noise ratio distributions.We also compare the CoMP-specific front-haul rate requirements for all the schemes considered in this paper. Our results indicate that, with a linear minimum mean-square error receiver, the JRFD and TSEQ have identical performances, whereas S-TSEQ relaxes the front-haul latency requirements while approaching the performance of TSEQ. Furthermore, in a HetNet environment, we find that CS-AIM provides an attractive alternative to TBSD and LLR-E with a significantly reduced CoMP-specific front-haul rate requirement.

Spatial spectrum approach for pilot spoofing attack detection in MIMO systems

  • Ning, Lina;Li, Bin;Wang, Xiang;Liu, Xiaoming;Zhao, Chenglin
    • ETRI Journal
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    • v.43 no.5
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    • pp.941-949
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    • 2021
  • In this study, a spatial spectrum method is proposed to cope with the pilot spoofing attack (PSA) problem by exploiting the of uplink-downlink channel reciprocity in time-division-duplex multiple-input multiple-output systems. First, the spoofing attack in the uplink stage is detected by a threshold derived from the predefined false alarm based on the estimated spatial spectrum. When the PSA occurs, the transmitter (That is Alice) can detect either one or two spatial spectrum peaks. Then, the legitimate user (That is Bob) and Eve are recognized in the downlink stage via the channel reciprocity property based on the difference between the spatial spectra if PSA occurs. This way, the presence of Eve and the direction of arrival of Eve and Bob can be identified at the transmitter end. Because noise is suppressed by a spatial spectrum, the detection performance is reliable even for low signal-noise ratios and a short training length. Consequently, Bob can use beamforming to transmit secure information during the data transmission stage. Theoretical analysis and numerical simulations are performed to evaluate the performance of the proposed scheme compared with conventional methods.

Effect Analysis of Residual Frequency Offsets for Asynchronous MC-CDMA Uplink Systems (비동기 MC-CDMA 상향 링크 시스템에서의 잔류 주파수 옵셋 영향 분석)

  • Ko, Kyun-Byoung;Woo, Choong-Chae
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.8
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    • pp.9-15
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    • 2010
  • This paper presents an analysis of asynchronous multicarrier-code division multiple access (MC-CDMA) uplink systems over frequency-selective multipath fading channels when the frequency offsets (FOs) of all users are random variables and the frequency offset for the desired user is compensated. The effect of a residual frequency offset(RFO) on the average bit error rate (BER) is evaluated by the semi-analytical method, then the approximated BER performance is obtained as a closed-form expression. Moreover, the signal to noise ratio (SNR) loss caused by RFO is evaluated. Derived results show that the performance degradation due to RFO is negligible if the estimation error of RFO for the desired user is less than the normalized value of 0.1.

A Feasibility Study on Opportunistic Interference Alignment: Improved Energy Efficiency via Power Control (기회적 간섭 정렬의 실현 가능성 연구: 전력 제어를 통한 에너지 효율성 개선)

  • Shin, Won-Yong;Yoon, Jangho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.5
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    • pp.1077-1083
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    • 2015
  • In this paper, we introduce an energy-efficient opportunistic interference alignment (OIA) scheme that greatly improves the sum-rates in multi-cell uplink networks. Each user employs optimal transmit vector design and power control in the sense of minimizing the amount of generated interference to other-cell base stations while satisfying a required signal quality. As our main result, it is shown that owing to the reduced interference level, the proposed OIA schemes attains larger sum-rates than those of OIA with no power control for almost all signal-to-noise ratio regions. In addition, when both zero-forcing and minimum mean square error (MMSE) detectors are employed at the receiver along with the OIA scheme, it is shown that the OIA scheme with MMSE detection shows superior performance.

A Synchronous Digital Duplexing Technique for Wireless Transmission in Indoor Environments (옥내 환경에서 무선 전송을 위한 동기식 디지털 이중화 방식)

  • Park, Chang-Hwan;Ko, Yo-Han;Park, Kyung-Won;Jeon, Won-Gi;Paik, Jong-Ho;Lee, Seok-Pil;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.12C
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    • pp.971-982
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    • 2008
  • In this paper, we propose a new digital duplexing scheme, called SDD(Synchronous Digital Duplexing), which can increase data efficiency and flexibility of resource by transmitting uplink signal and downlink signal simultaneously. In order to transmit uplink data and downlink data simultaneously, the proposed SDD obtains mutual informations between AP(access point) and each SSs(subscriber station), SS and other SSs by mutual ranging procedure. These informations are used for selection of transmission time, decision of CS insertion, setting of CS length, and FFT duration resetting, etc. It is shown that the proposed SDD is appropriate for duplexing scheme in indoor environments over the conventional TDD(Time Division Duplexing) and FDD(Frequency Division Duplexing).

A Study on the Uplink SDMA Systems: User Scheduling, Transmit Power Control, and Receive Beamforming (상향링크 공간 분할 다중 접속 시스템에서 사용자 스케쥴링, 송신 전력 제어, 수신 빔포밍에 관하여)

  • Cho, Moon-Je;Ban, Tae-Won;Jung, Bang Chul
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.2
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    • pp.289-294
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    • 2014
  • In this paper, we investigate the user scheduling, transmit beamforming, and receive beamforming of uplink space division multiple access (SDMA) systems where multiple users are allowed to transmit their signal to a base station (BS) using the same frequency band simultaneously. The BS performs a receive beamforming using the predetermined pseudo-random pattern and select users with a specific criterion. Especially, in this paper, we propose the threshold-based transmit power control, in which a user decrease its transmit power according if its generating interference to other users's signal is larger than a predetermined threshold. Assuming that the TDD system is used, the channel state information (CSI) can be obtained at each user from pilot signals from the BS. Simulation results show that the proposed technique significantly outperforms the existing user scheduling algorithms.

BER Performance of Spatial Modulation in Uplink Multi-User Environment (상향 링크 다중 사용자 환경에서 공간 변조의 BER 성능)

  • Kim, Jin Kwan;Hyun, Kwangmin;Park, Sang Kyu
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.9
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    • pp.922-927
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    • 2013
  • In this paper, we evaluate the performance of up-link multi-user MIMO systems with SM. The receiver demodulates the received signal using ML method determines the signal which seems to be the most probable after comparing the received signal and all transmitted signal candidates. When transmitting with the same data rate, the SM method shows better performance of bit error rate(BER) than that of the space shift keying(SSK) of the previously proposed multi-user system.

Implementation of a Smart Antenna System for Wide-Band CDMA WLL Channel (광대역 CDMA WLL용 스마트 안테나 시스템 구현)

  • 김미경;황현구;김종헌;박환석;김상태;최승원
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.6
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    • pp.912-918
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    • 2001
  • This paper presents a performance analysis of experimental observations of a uplink smart antenna system operating in a wide-band CDMA environment designed for a WLL (Wireless Local Loop) system. The numerical results shown in this paper have been obtained from practical experiments using commercially developed mobile terminals. The beam pattern provided by the weight vector and the resultant BER (Bit Error Rate) are observed in both indoor and outdoor signal environments. From the experimental observations, it is concluded that the proposed smart antenna system provides significant improvements in receiving both indoor and outdoor signal environments.

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