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Resource management in the next-generation DS-CDMA cellular networks

IEEE WIRELESS COMMUNICATIONS 2004年第4期11卷 52-58页

作者： Zhang, JH Huai, JP Xiao, RY Li, B Hong Kong Univ Sci & Technol Hong Kong Hong Kong Peoples R China Beijing Univ Aeronaut & Astronaut Beijing 100083 Peoples R China Hong Kong Univ Sci & Technol Hong Kong Hong Kong Peoples R China

direct sequence code-division multiple access has been shown as the predominant access technology to provide high-speed multimedia services in next-generation wireless cellular networks. The DS-CDMA cellular network significantly differentiates itself from the traditional narrowband TDMA/FDMA system, in which great capacity gain can be explored by taking advantage of its unique characteristics. This article addresses resource management in DS-CDMA cellular networks. We first provide an overview of the DS-CDMA network and discuss the main challenges in the design of resource management schemes. We then examine several critical issues within the scope of resource management, including congestion control, rate and power control, and cell planning, with the emphasis on call admission control. Finally, we offer some insights and discussions on the performance aspects, strengths, and weaknesses of existing proposals.

关键词： cellular radio code division multiple access multimedia communication power control spread spectrum communication telecommunication congestion control telecommunication network management telecommunication network planning call admission control congesti Spread spectrum communication telecommunication network planning telecommunication congestion control direct-sequence code-division multiple access code division multiple access Power control Cellular networks access to technology management of resources Call admission control Telecommunication network management

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Synchronization sensitivity of multicarrier systems

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EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS 2004年第3期15卷 223-234页

作者： Steendam, H Moeneclaey, M Ghent Univ TELIN Dept DIGCOM Res Grp B-9000 Ghent Belgium

In this paper, we give an overview of the sensitivity of a number of multicarrier systems to carrier and clock synchronization errors. A comparison is made between orthogonal frequency division multiplexing/ multiple access (OFDM(A)) and two combinations of the orthogonal multicarrier technique and the codedivision multiple access (CDMA) technique, i.e. multicarrier CDMA (MC-CDMA), where the spreading is accomplished in the frequency domain and multicarrier direct-sequence CDMA (MC-DS-CDMA), where the spreading is done in the time domain. We evaluate the effect of small synchronization errors on the BER performance by deriving simple analytical expressions for the BER degradation that are based upon truncated Taylor series expansions. To allow a fair comparison, all considered systems are able to accommodate the same number of users and each user operates at the same data rate. Under these conditions, we show that all multicarrier systems exhibit the same sensitivity to carrier phase jitter and timing jitter. Further, when the number of carriers is equal to the maximum number of users, the different multicamer systems also are equally affected by a carrier frequency offset or a clock frequency offset. Copyright (C) 2004 AEI.

关键词： TIME-DOMAIN direct-sequence code-division multiple access bit error rate performance Frequency-domain analysis numerical invariant Consumers Frequency division carrier frequency offset code division multiple access timing jitter

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Performance analysis of M-ary DS-CDMA systems with imperfect power control

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IEE PROCEEDINGS-COMMUNICATIONS 2004年第6期151卷 574-580页

作者： Chiang, CT I Shou Univ Dept Elect Engn Kaohsiung 84008 Taiwan

The system performance of an M-ary DS-CDMA system is investigated for a coherent reception of uplink signals. In addition, the effect of imperfect power control resulting in a lognormal distribution of signal power on the system performance is also considered. A theoretical expression for the bit error rate (BER) performance of M-ary DS-CDMA systems with imperfect power control is achieved. The results show that the M-ary orthogonal modulation can offer performance improvement in terms of BER and capacity, even under imperfect power control. However, the advantage of M-ary technology is almost lost due to bad power control, even increasing the M value. For a specified performance, the derived results can be used as guides in evaluating the required quality of power control for an M-ary DS-CDMA system. Simulation results verify the theoretical derivations.

关键词： coherent reception direct-sequence code-division multiple access CDMA mobile communications signal power M Value Bit error rate System performance Power control Imperfect performance boost

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Impact of ionospheric scintillations on LEO satellite DS-CDMA communication system

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ELECTRONICS LETTERS 2004年第8期40卷 486-488页

作者： Li, SY Liu, CH Natl Cent Univ Dept Elect Engn Taoyuan 320 Taiwan Natl Def Univ Natl Chung Cheng Univ Dept Elect Engn Taoyuan Taiwan

The impact of ionospheric scintillations is investigated in terms of bit error rate for a multispot beam LEO satellite communication system employing direct sequence-code division multiple access (DS-CDMA) technique. Depending on the satellite orbit parameters and the earth station location, the effect of time-varying ionospheric scintillation on the system varies. Performance degradation can be substantial in times of severe scintillations.

关键词： direct-sequence code-division multiple access close-orbit satellite degradation of performance COMMUNICATION SYSTEMS IONOSPHERIC SCINTILLATION

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Interference suppression for spatial-temporal propagation parameter identification in wireless communications

Interference suppression for spatial-temporal propagation pa...

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International Conference on Communications, Circuits and Systems

作者： Ristaniemi, T Wu, R Tampere Univ Technol Inst Commun Technol FIN-33101 Tampere Finland

ISBN: (纸本)0780386477

In this paper Independent Component Analysis (ICA) is considered for code timing and direction-of-arrival (DOA) estimation, here called two-dimensional code acquisition, in a direct sequence spread spectrum communication system utilizing antenna arrays. A new method named as independent component analysis frequency selection (ICA-FS) is used to perform interference suppression before parameter estimation as to decrease parameter estimation error. It requires a training sequence corresponding to the desired user to be known, and data signals corresponding to different users to be statistically independent.

关键词： direction-of-arrival estimation spread spectrum communication code division multiple access delay estimation interference suppression independent component analysis array signal processing spatial-temporal propagation parameter identification wireless communications independent component analysis frequency selection code timing estimation DOA estimation two-dimensional code acquisition direct sequence spread spectrum communication system antenna arrays parameter estimation error training sequence time delay estimation DS-CDMA direction of arrival estimation suppression of interference delay estimation CARRIER SYSTEM training sequence Antenna arrays code division multiple access Spread spectrum communication array signal processing Parameter estimation direct-sequence code-division multiple access direct sequence spread spectrum communication

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On the total weighted square correlation minimization in multicellular synchronous DS-CDMA systems

On the total weighted square correlation minimization in mul...

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IEEE Information Theory Workshop

作者： Cotae, P Aguirre, M Lacatus, C Univ Texas Dept Elect Engn San Antonio TX 78249 USA

ISBN: (纸本)0780387201

A definition of total weighted square correlation (TWSC) for an overloaded multicellular synchronous DS-CDMA system in the presence of multipath on the uplink is introduced. We assume the channel state information known perfectly both at transmitter and receiver. The optimum solutions of minimizing TWSC are the orthogonal generalized WBE (Welch Bound Equality) spreading sequences. The design of such sequences in the context of cooperative multibase DS-CDMA systems under TWSC criterion is presented.

关键词： cellular radio spread spectrum communication code division multiple access correlation theory minimisation multipath channels binary sequences total weighted square correlation multipath channel channel state information orthogonal generalized WBE Welch bound equality spreading sequences cooperative multibase DS-CDMA systems uplink TWSC minimization synchronous DS-CDMA overloaded multicellular system Multipath channels spreading sequence Channel state information up link code division multiple access correlation theory binary sequences Spread spectrum communication cellular radio direct-sequence code-division multiple access CDMA mobile communications

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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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An iterative frequency-domain decision feedback receiver for CDMA systems

An iterative frequency-domain decision feedback receiver for...

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International Symposium on Wireless Communication Systems (ISWCS)

作者： P. Silva R. Dinis CAPS-IST Technical University of Lisbon Portugal

Unless high-complexity receiver structures are employed, conventional DS-CDMA (direct sequence code division multiple access) schemes can have a poor performance in severe time-dispersive channels, since the orthogonality between the users is lost. In this paper, we propose an iterative frequency-domain decision feedback equalizer for the downlink transmission within DS-CDMA systems employing block-transmission techniques, with an appropriate cyclic extension appended to each block. Our performance results show that the proposed receiver structure has excellent performance, close to the single-user MFB (matched filter bound), even for severe time-dispersive scenarios and/or in the presence of strong interfering channels.

关键词： Multiaccess communication OFDM modulation Decision feedback equalizers Interference Frequency domain analysis Filters direct-sequence code-division multiple access Downlink Degradation RAKE receivers

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Complex orthogonal sequences from amicable Hadamard matrices

Complex orthogonal sequences from amicable Hadamard matrices

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IEEE Conference on Vehicular Technology (VTC)

作者： L.C. Tran J. Seberry B.J. Wysocki T.A. Wysocki T. Xia Ying Zhao Faculty of Informatics University of Wollongong NSW Australia

The paper deals with the novel technique of designing complex spreading sequences with only four phases (0.257/spl pi/, 0.75/spl pi/, 1.25/spl pi/, 1.75/spl pi/). The interesting feature of those new sequences is the fact that not only the complex sequences are orthogonal but the real parts and imaginary parts are independently orthogonal. This can be utilized for spreading of complex constellation signals where the independent spreading using bipolar sequences (real part for in-phase component and imaginary part for quadrature component) can be applied. The paper introduces the theoretical background, and some example constructions of the amicable Hadamard matrices and the corresponding complex spreading sequences. The sequences are later modified using a diagonal method to achieve better correlation properties.

关键词： Error correction Error correction codes Propagation delay Constellation diagram direct-sequence code-division multiple access Multiaccess communication Base stations multiple access interference Multiuser detection Bandwidth

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Total weighted squared correlation design of real multicellular CDMA spreading sequences

Total weighted squared correlation design of real multicellu...

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MILCOM, Military Communications Conference

作者： P. Cotae Department of Electrical and Computer Engineering University of Technology San Antonio TX USA

A definition of total weighted square correlation (TWSC) for an overloaded multicellular synchronous DS-CDMA system in the presence of multipath on the uplink is introduced. We assume the channel state information known perfectly both at transmitter and receiver. The optimum solutions of minimizing TWSC are the orthogonal generalized WBE (Welch bound equality) spreading sequences. The design of such sequences in the context of cooperative multibase DS-CDMA systems under TWSC criterion is presented. The bandwidth of initial generalized WBE signals of each cell is preserved in the extended signal space associated to multiple cell system.

关键词： Multiaccess communication Correlation Bandwidth Design optimization multiple access interference Interference constraints Base stations Channel state information Transmitters direct-sequence code-division multiple access

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