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Performance Degradation in Pre-rake Frequency-division Duplex/direct sequence-code division multiple access Systems

DEFENCE SCIENCE JOURNAL 2010年第3期60卷 282-289页

作者： Subhas, C. Naidu, K. Rama Reddy, Y. Venkatarami Sree Vidyanikethan Engn Coll Tirupati 517102 Andhra Pradesh India JNTU Coll Engn Anantapur 515002 Andhra Pradesh India Andhra Pradesh Publ Serv Commiss Hyderabad Andhra Pradesh India

The transmitter-based pre-rake diversity combining technique reduces the complexity, size and cost of the mobile unit (MU), while achieving the same inter symbol interference (ISI) mitigation effects of rake receiver for direct sequence-code division multiple access (DS-CDMA) systems. The technique is based on preprocessing of transmitted signal relying on knowledge of the channel state information (CSI) before transmission. In most of the previous works, this a priori information is either assumed or estimated for the uplink and the same is applied to the downlink in time division duplex (TDD) systems due to channel reciprocity. In this paper, a method for channel prediction to evaluate the pre-rake system using binary phase-shift keying (BPSK) modulation in frequency-division duplex (FDD) through analytical and computer simulations for DS-CDMA downlink has been proposed. The performance of the system was also evaluated under ideal and predicted channel conditions using different spreading codes. The findings will have widespread applications in defence communication equipment.

关键词： direct sequence-code division multiple access DS-CDMA rake receiver pre-rake inter-symbol interference frequency-division duplex FDD channel prediction

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Performance analysis of an interference cancellation technique for radio navigation

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IET RADAR SONAR AND NAVIGATION 2018年第4期12卷 426-432页

作者： Jang, Jaegyu Seo, Seungwoo Ahn, Woo-Guen Lee, Jangyong Park, Junpyo Agcy Def Dev Satellite Nav Team Yuseong PP Box 35 Daejeon South Korea

This study describes the theoretical performance of a successive interference cancellation (IC) technique as an electronic counter countermeasure and verifies its feasibility through experiments. In a radio navigation system using direct sequence/code division multiple access, strong pseudorandom signals can be used as interference sources for unauthorised users when regional radio navigation needs to be denied in a specific area, while authorised users can use both the strong signal and the global navigation satellite system (GNSS) ranging signal for navigation through the IC method. To determine the feasibility of this selective jamming concept, this study investigated its theoretical performance and compared the results with experimental ones. The experimental results show that a maximum jamming-to-signal ratio performance of 57 dB or higher can be achieved, which is similar to the theoretical estimation.

关键词： interference suppression radiofrequency interference satellite navigation electronic countermeasures code division multiple access spread spectrum communication jamming successive interference cancellation technique successive IC technique electronic counter countermeasure direct sequence-code division multiple access strong pseudorandom signals regional radionavigation system GNSS ranging signal selective jamming concept maximum jamming-to-signal ratio performance gain 57 dB

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Error probability of direct sequence-code division multiple access systems with adaptive antenna minimum mean-square error multiuser receivers in Rayleigh-lognormal fading

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IET COMMUNICATIONS 2009年第10期3卷 1649-1658页

作者： Moro, A. Spagnolini, U. Andrew Telecommun Prod SRL R&D Dept I-20041 Agrate Brianza MI Italy Politecn Milan Dip Elettron & Informaz I-20133 Milan Italy

In direct sequence-code division multiple access (DS-CDMA) cellular systems spreading codes, fading and positions of the users can be modelled as independent random variables and the corresponding multiuser interference (MUI) experienced by the base station is non-stationary. Here we evaluate in closed form the bit error probability for space-time linear minimum mean square error (MMSE) multiuser receivers for symbol-synchronous DS-CDMA system ( bounds are provided for symbol-asynchronous system) by extending the known asymptotic results for random spreading sequences to non-stationary MUI. The analysis is based on the effective interference at the decision variable that is carried out to account for the non-stationary MUI that results from the multiuser beamforming that adapts each spatial. filter to the randomness of the angle of arrivals of all the users. Propagation for each user is Rayleigh-lognormal faded channels as it is fairly general to model the imperfect power-control. The numerical validation proves that a simple geometrical model is accurate to evaluate the error probability for any arbitrary system loading.

关键词： bit error probability Rayleigh-lognormal fading channel error statistics least mean squares methods multiuser beamforming code division multiple access spatial filter random spreading sequences space-time linear minimum mean square error multiple access communication multiuser detection DS-CDMA multiuser receivers direct sequence-code division multiple access Interpolation and function approximation (numerical analysis) Radio links and equipment multiuser interference Rayleigh channels spread spectrum communication MMSE adaptive antenna Other topics in statistics

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Multiuser Detection over Generalized-K Fading Channels using Two-Stage Initialized Teaching Learning Based Optimization 5

Multiuser Detection over Generalized-<i>K</i> Fading Channel...

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International Conference on Advances in Computing, Communications and Informatics (ICACCI)

作者： Gondela, Lakshmi Manasa Pamula, Vinay Kumar Tipparti, Anil Kumar Univ Coll Engn Kakinada JNTUK Dept Elect & Commun Engn Kakinada 533003 India MVSR Engn Coll Dept Elect & Commun Engn Hyderabad 501510 Andhra Pradesh India

ISBN: (纸本)9781509020287

A multiuser detection (MUD) technique for direct sequence-code division multiple access (DS-CDMA) systems over generalized-K (GK) fading channels using teaching learning based optimization algorithm (TLBO) with two-stage initialization (TSI) is proposed. In DS-CDMA systems, MUD techniques are applied to combat multiple access interference (MAI)and ambient noise. Empirical results proved that the ambient noise is non-Gaussian and impulse in nature which degrades the performance of the system substantially. The DS-CDMA signals are transmitted over channels that introduce impulsive noise, shadowing and fading. In this paper, we develop least-squares (LS), Huber and Hampel M-estimation based MUD technique for joint detection of DS-CDMA signals in the presence of MAI, impulsive noise, modeled by Laplace distribution, and channel fading, modeled by GK distribution. The TLBO with TSI (TLBO-TSI) algorithm is used to minimize a penalty function that is a less rapidly increasing function of residuals. Average bit error rate (BER) is computed to assess the performance of the TLBO-TSI based detector. Obtained results demonstrate that the proposed robust technique offer significant performance gains with increase in signal-to-noise ratio (SNR) and diversity order in the presence of heavy-tailed impulsive noise.

关键词： Bit error rate direct sequence-code division multiple access Generalized-K distribution multi user detection teaching learning based optimization

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Multiuser Detection over Generalized-K Fading Channels using Two-Stage Initialized Teaching Learning Based Optimization

Multiuser Detection over Generalized-K Fading Channels using...

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International Conference on Advances in Computing, Communications and Informatics

作者： Lakshmi Manasa Gondela Vinay Kumar Pamula Anil Kumar Tipparti Department of Electronics and Communication Engineering University College of Engineering Kakinada JNTUK Kakinada India 533003 Department of Electronics and Communication Engineering MVSR Engineering College Hyderabad India 501510

ISBN: (纸本)9781509020300

A multiuser detection (MUD) technique for direct sequence-code division multiple access (DS-CDMA) systems over generalized-K (GK) fading channels using teaching learning based optimization algorithm (TLBO) with two-stage initialization (TSI) is proposed. In DS-CDMA systems, MUD techniques are applied to combat multiple access interference (MAI) and ambient noise. Empirical results proved that the ambient noise is non-Gaussian and impulse in nature which degrades the performance of the system substantially. The DS-CDMA signals are transmitted over channels that introduce impulsive noise, shadowing and fading. In this paper, we develop least-squares (LS), Huber and Hampel M-estimation based MUD technique for joint detection of DS-CDMA signals in the presence of MAI, impulsive noise, modeled by Laplace distribution, and channel fading, modeled by GK distribution. The TLBO with TSI (TLBO-TSI) algorithm is used to minimize a penalty function that is a less rapidly increasing function of residuals. Average bit error rate (BER) is computed to assess the performance of the TLBO-TSI based detector. Obtained results demonstrate that the proposed robust technique offer significant performance gains with increase in signal-to-noise ratio (SNR) and diversity order in the presence of heavy-tailed impulsive noise.

关键词： Bit error rate direct sequence-code division multiple access Generalized-K distribution Multi user detection Teaching learning based optimization

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System-Level Throughput of Non-orthogonal access with SIC in Cellular Downlink When Channel Estimation Error Exists 79

System-Level Throughput of Non-orthogonal Access with SIC in...

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IEEE 79th Vehicular Technology Conference (VTC-Spring)

作者： Yamamoto, Kenta Saito, Yuya Higuchi, Kenichi Tokyo Univ Sci Grad Sch Sci & Technol Tokyo 162 Japan NTT DOCOMO INC Radio Access Network Dev Dept London England

ISBN: (纸本)9781479944828

We investigate the influence of channel estimation error on the achievable system-level throughput performance of non-orthogonal access with successive interference cancellation (SIC) in the cellular downlink. The channel estimation error in non-orthogonal access causes residual interference in the SIC process, which decreases the achievable user throughput. Furthermore, the channel estimation error causes error in the transmission rate control for the respective users, which may result in decoding error at not only the destination user terminal but also other user terminals for SIC. However, we show that by using a simple transmission rate back-off algorithm, the impact of the channel estimation error is effectively alleviated and non-orthogonal access with SIC achieves clear average and cell-edge user throughput gains relative to orthogonal access similar to the case with perfect channel estimation.

关键词： cellular radio channel estimation code division multiple access error analysis interference suppression SIC process cell-edge user throughput gains cellular downlink channel estimation error exists decoding error destination user terminal direct sequence-code division multiple access nonorthogonal access residual successive interference cancellation system-level throughput performance transmission rate control back-off algorithm Base stations Channel estimation Decoding Downlink Interference Silicon carbide Throughput channel estimation direct-sequence code-division multiple access Downlink Throughput non-orthogonal code division multiple access BASE STATION cellular radio suppression of interference DECODING Error analysis SILICON CARBIDE

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Resource allocation and scheduling in uplink for multimedia CDMA wireless systems

Resource allocation and scheduling in uplink for multimedia ...

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IEEE/Sarnoff Symposium on Advances in Wired and Wireless Communication

作者： Akin, HC Wasserman, KM Univ Calif San Diego Sch Elect Engn La Jolla CA 92093 USA

ISBN: (纸本)0780382196

We introduce a novel power allocation and scheduling scheme in a DS-CDMA (direct sequence - code division multiple access) wireless communication system with real-time connections. Generally in a CDMA system all users share the same bandwidth which makes the system, interference limited. Because of this nature of such a system, power control is crucial especially in uplink. Traditionally, for real-time traffic power control is aimed to have equal received powers at the base station to overcome the near-far effect. We will relax this design objective and explore a different power allocation and scheduling scheme to achieve maximum total throughput in the system. We formulate the optimization problem which achieves the optimum power allocation and scheduling scheme, and then reduce the optimization problem to a linear programming problem and solve it. We use our results to discuss and compare our novel scheme with the traditional perfect power controlled CDMA systems, to show that the introduced scheme outperforms traditional perfect power controlled CDMA.

关键词： code division multiple access power control multimedia communication bandwidth allocation linear programming scheduling spread spectrum communication telecommunication traffic personal communication networks resource allocation uplink scheduling multimedia wireless systems DS-CDMA power allocation direct sequence-code division multiple access wireless communication system maximum total throughput real-time traffic direct-sequence code-division multiple access Power control power splitting linear programming code division multiple access Wireless communication systems Resource utilization real-time traffic Spread spectrum communication telecommunication traffic bandwidth allocation CARRIER SYSTEM up link

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Multipath interference canceller for high-speed packet transmission with adaptive modulation and coding scheme in W-CDMA forward link

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2002年第2期20卷 419-432页

作者： Higuchi, K Fujiwara, A Sawahashi, M NTT DoCoMo Inc Wireless Access Lab Kanagawa 2398536 Japan

This paper proposes a mutlipath interference canceller (MPIC) associated with orthogonal code-multiplexing that achieves much higher peak throughput than 2 mb/s with adaptive data modulation for high-speed packet transmission in the wideband direct sequence-code division multiple access (W-CDMA) forward link, and evaluates its throughput performance by computer simulation. The simulation results elucidate that sufficient multipath interference (MPI) suppression is achieved by a four-stage MPIC with 6-12 orthogonal code-multiplexing using one iterative channel estimation with pilot and decision feedback data symbols and further that the interference rejection weight control according to the number of observed multipaths is effective in improving the throughput. It is also demonstrated that MPIC exhibits a superior MPI suppression effect to a chip equalizer in the lower received signal energy per bit-to-background noise spectrum density (E-b/N-0) channel around 0-3 dB owing to the successive channel estimation at each stage. We show that the maximum peak throughput using MPIC is approximately 2.1 fold that without MPIC in a two-path and three-path Rayleigh fading channel and that the peak throughput of 8.0 mb/s is achieved using 64QAM data modulation in a two-path fading channel within a 5-MHz bandwidth. Furthermore, the required average E-b/N-0 for satisfying the same throughput with MPIC is decreased by more than 2.0 dB. MPIC utilizes an efficient high-level data modulation scheme and is very effective in extending the coverage in which much higher throughput can be provided under multipath fading channels for high-speed packet transmission in the W-CDMA forward link.

关键词： adaptive modulation direct sequence-code division multiple access interference canceller multipath packet transmission

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Experiments on pilot symbol-assisted coherent multistage interference canceller for DS-CDMA mobile radio

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2002年第2期20卷 433-449页

作者： Sawahashi, M Higuchi, K Andoh, H Adachi, F NTT DoCoMo Inc Wireless Access Lab Yokosuka Kanagawa 2398536 Japan Tohoku Univ Grad Sch Engn Dept Elect & Commun Engn Sendai Miyagi 9808579 Japan

A three-stage coherent multistage interference canceller (COMSIC) employing pilot symbol-assisted (PSA) channel estimation for replica generation of multiple access interference (MAI) is implemented and its performance in the presence of frequency selective multipath fading is experimentally evaluated by a multipath fading simulator. A fast transmission power control (TPC) method suitable for COMSIC is also proposed, in which the signal-to-interference plus background noise power ratio (SIR) at the matched filter (MF) based Rake receiver is measured to achieve a short TPC delay and the target signal-to-interference ratio value is compensated by an outer loop so that the measured block error rate (BLER) is equal to the prescribed target value. The experimental results show that as expected the COMSIC satisfactorily reduces the MAI even when the number of active users is equal to the spreading factor in a multipath fading environment, and thus, improves the bit error rate (BER) performance in a multiuser environment. The results also show that the proposed fast TPC method with a two-slot delay associated with COMSIC works satisfactorily and the combination of COMSIC and fast TPC significantly decreases the transmission power of a mobile station (required transmission power of a mobile station with COMSIC at the average BER of 10(-3) is decreased by approximately 2.0 (3.0) dB compared with the MF-based Rake receiver with (without) antenna diversity reception). This extends the cell coverage, battery life, and increases the system capacity in the reverse link.

关键词： channel estimation direct sequence-code division multiple access interference canceller transmission power control

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