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Blind channel estimation in multicode CDMA using multiantenna receiver

WIRELESS PERSONAL COMMUNICATIONS 2004年第3期28卷 163-178页

作者： Melvasalo, M Koivunen, V Aalto Univ SMARAD CoE Signal Proc Lab FIN-02015 Helsinki Finland

In this paper blind channel estimation methods for long code CDMA system with multicode transmission are proposed. By allocating multiple codes, higher data rates may be provided to a user. Blind channel estimation allows reducing pilot signaling. Hence, higher effective data rates may be achieved and larger sample support may be obtained by using both the information symbols and known pilot symbols for channel estimation. Algorithms are extended to multi-antenna receiver which further improves the performance. The performance of the algorithms is studied in extensive simulations using WCDMA system model. The effects of code selection, interference and noise, number of antennas, antenna correlation are considered using frequency selective channel models. The proposed methods are more robust in the face of interference and code selection than the well-known subspace method in [7]. The computational complexity is lower as well.

关键词： WCDMA multicode antenna array blind channel estimation subspace methods

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Analytical framework for simultaneous MAC packet transmission (SMPT) in a multicode QDMA wireless system

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2004年第1期53卷 223-242页

作者： Krishnam, M Reisslein, M Fitzek, F Arizona State Univ Dept Elect Engn Tempe AZ 85287 USA Acticom GMBH D-13507 Berlin Germany

Stabilizing the throughput over wireless links is one of the key challenges in providing high-quality wireless multimedia services. Wireless links are typically stabilized by a combination of link-layer automatic repeat request (ARQ) mechanisms in conjunction with forward error correction and other physical layer techniques. In this paper, we focus on the ARQ component and study a novel class of ARQ mechanisms, referred to as simultaneous MAC packet transmission (SMPT). In contrast to the conventional ARQ mechanisms that transmit one packet at a time over the wireless air interface, SMPT exploits the parallel code channels provided by multicode code-division multiple access. SMPT stabilizes the wireless link by transmitting multiple packets in parallel in response to packet drops due to wireless link errors.' While these parallel packet transmissions stabilize the link layer throughput, they also increase the interference level in a given cell of a cellular network or cluster of an ad hoc network. This increased interference reduces the number of traffic flows that can be simultaneously. supported in a cell/cluster. We develop an analytical framework for the class of SMPT mechanisms and analyze the link-layer buffer occupancy and the code usage in a wireless system running some form of SMPT. Our analysis quantifies the tradeoff between increased link-layer quality of service and reduced number of supported flows in SMPT with good accuracy, as verified by simulations. In A typical scenario, SMPT reduces the probability of link-layer buffer overflow by over two orders of magnitude (thus enabling high-quality multimedia services, such as real-time video streaming) while supporting roughly 20% fewer flows than conventional ARQ. Our analytical framework provides a basis for resource management in wireless systems running some form of SMPT and optimizing SMPT mechanisms.

关键词： automatic repeat request (ARQ) buffer occupancy capacity code-division multiple access (CDMA) link-layer quality of service (QoS) multicode packet-loss probability throughput

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Channel adaptive fair queueing for scheduling integrated voice and data services in multicode CDMA systems

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COMPUTER COMMUNICATIONS 2004年第9期27卷 809-820页

作者： Wang, L Kwok, YK Lau, WC Lau, VKN Univ Hong Kong Dept Elect & Elect Engn Hong Kong Hong Kong Peoples R China

Code Division Multiple Access (CDMA) systems continue to be critical building blocks of future high performance wireless and mobile computing systems. While CDMA systems are very mature for voice services, their potentials in delivering high quality data services (e.g. multimedia messaging services) are yet to be investigated. One of the most crucial components in an advanced wideband CDMA system is the judicious allocation of band width resources to both voice and high data rate services so as to maximize utilization while satisfying the respective quality of service requirements. Specifically, in a multicode CDMA system, the goal is to intelligently allocate codes to the users' requests. While previous work in the literature has addressed this problem from a capacity point of view, the fairness aspect, which is also important from the users' point of view, is largely ignored. In this paper, we propose a new code allocation approach that is channel adaptive and can guarantee fairness with respect to the users' channel conditions. Simulation results show that our approach is more effective than the proportional fair approach. (C) 2004 Elsevier B.V. All rights reserved.

关键词： wireless multicode code division multiple access scheduling rate allocation fairness channel adaptive

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Performance Analysis of OFDM based UWB Systems with a Frequency-Domain CDMA for Multiple SOPs

Performance Analysis of OFDM based UWB Systems with a Freque...

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IEEE 65th Vehicular Technology Conference (VTC-Spring 2007), vol.5

作者： Esa Kunnari Jari Iinatti Centre for Wireless Communications (CWC) University of Oulu Finland

In this paper, a performance analysis for the frequency-domain code-division multiple-access (CDMA) of multiple simultaneously operating piconets (SOPs) in orthogonal frequency-division multiplexing (OFDM) based ultra-wideband (UWB) systems is presented. Two different strategies for the accommodation of multiples SOPs, namely, the variable spreading factor (VSF) scheme with minimal spreading and the multicode scheme with maximal spreading, were considered. The channel is assumed to be Rayleigh fading with exponentially decaying delay power profile. Furthermore, the analysis takes into account the intersymbol interference (ISI) caused by the multipath delay components exceeding the guard interval. Numerical results demonstrate that the frequency-domain CDMA can be employed to accommodate multiple SOPs while maintaining acceptable performance when a suitable subcarrier combining method is used. The VSF and multicode schemes result in a similar performance when the number of SOPs is large, while notable differences are pointed out when there are only a few SOPs.

关键词： UWB-OFDM MC-CDMA multicode Variable spreading factor Delay spread

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On codes with low peak-to-average power ratio for multicode CDMA

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IEEE TRANSACTIONS ON INFORMATION THEORY 2004年第3期50卷 550-559页

作者： Paterson, KG Hewlett Packard Labs Bristol BS34 8QZ Avon England

Codes which reduce the peak-to-average power (PAPR) in multicode code-division multiple-access (MC-CDMA) communications systems,are systematically studied. The problem of designing such codes is reformulated as a new coding-theoretic problem: codes with low PAPR are ones in which the codewords are far from the first-order Reed-Muller code. Bounds on the tradeoff between rate, PAPR, and error-correcting capability of codes for MC-CDMA follow. The connections between the code design problem, bent functions, and algebraic coding theory (in particular, the Kerdock codes and Delsarte-Goethals codes) are exploited to construct code families with flexible parameters for the small values of n of practical interest. In view of their algebraic structure, these codes enjoy efficient encoding and decoding algorithms. The correspondence concludes by listing open problems in algebraic coding theory and Boolean functions motivated by the correspondence.

关键词： Bent function code-division multiple access (CDMA) envelope Kerdock multicode power rate adaptation Reed-Muller codes Walsh-Hadamard transform

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Cellular multicode CDMA capacity with SIR-based power control in a multipath fading environment

Cellular multicode CDMA capacity with SIR-based power contro...

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15th IEEE International Symposium on Personal, Indoor, Mobile, Radio Communications (PIMRC 2004)

作者： Téllez-Labao, C Romero-Jerez, JM Ruiz-García, M Univ Malaga ETSI Telecomunicac Dept Tecnol Elect E-29071 Malaga Spain

ISBN: (纸本)0780385233

In this paper, the reverse link capacity is analysed for a multicode direct sequence-code division multiple access (multicode DS/CDMA) system with SIR-based power-control in a multiple-cell environment. Mean and variance statistics of total interference power are derived in order to investigate the effect of two important factors on capacity: 1) the required signal to interference ratio (SIR) and 2) the required number of codes, for each type of user. Unlike most previous works related to SIR based power control, the effect of multipath fading is explicitly accounted for and mobiles are assumed to connect to the base station whose pilot signal is received with the highest power.

关键词： multicode CDMA power control target SIR

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On codes with low peak-to-average power ratio for multicode CDMA

On codes with low peak-to-average power ratio for multicode ...

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IEEE International Symposium on Information Theory

作者： Paterson, KG Hewlett Packard Labs Bristol BS34 8QZ Avon England

ISBN: (纸本)0780375017

关键词： Bent function code-division multiple access (CDMA) envelope Kerdock multicode power rate adaptation Reed-Muller codes Walsh-Hadamard transform

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Optimal power distribution control under different total power constraint strategies for multicode MC-CDMA with zero-forcing successive interference cancellation

Optimal power distribution control under different total pow...

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IEEE Wireless Communications and Networking Conference

作者： Tan, M Bar-Ness, Y New Jersey Inst Technol Dept ECE CCSPR Newark NJ 07102 USA

ISBN: (纸本)0780383443

multicode multi-carrier CDMA (MC-CDMA) is a promising candidate for supporting multimedia services in future wireless communications. However, the performance of this system is limited by self-interference (SI) and multi-user interference (MUI). To mitigate this problem, a nonlinear zero-forcing successive interference cancellation (ZF-SIC) receiver is applied in this paper. Furthermore, to minimize each user's bit error rate (BER), optimal power distribution control (PDC) is considered. Results show that in correlated Rayleigh fading channels, the multicode MC-CDMA system based on the ZF-SIC receiver with it optimal PDC remarkably outperforms other receivers proposed in the literature. Moreover, the ZF-SIC integrated with the optimal PDC present significant performance advantage over that with the equal BER PDC, particularly tinder a short-term total transmit power constraint.

关键词： multicode MC-CDMA ZF SIC power distribution control (PDC)

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Equal BER power distribution control for multicode MC-CDMA with MMSE successive interference cancellation

Equal BER power distribution control for multicode MC-CDMA w...

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IEEE International Conference on Communications (ICC 2004)

作者： Tan, MZ Bar-Ness, Y New Jersey Inst Technol ECE Dept Ctr Commun & Signal Proc Res Newark NJ 07102 USA

ISBN: (纸本)0780385330

multicode multi-carrier CDMA (MC-CDMA) is a promising candidate for supporting multimedia services in future wireless communications. However, the performance of this system is limited by self-interference (SI) of user's multicodes and multi-user interference (MUI). In this paper, to mitigate this problem, a minimum mean square error successive interference cancellation (MMSE-SIC) receiver is applied in multicode MC-CDMA. Furthermore, to increase the efficiency of SIC, a simple power distribution control (PDC) algorithm, based on equal BER criterion, is investigated under a short-term constraint of average transmit power. In correlated Rayleigh fading channels, the MMSE-SIC receiver integrated with the equal BER PDC can suppress interference effectively, resulting in a performance close to the single user bound (SUB).

关键词： multicode MC-CDMA MMSE SIC equal BER power distribution control (PDC)

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Performance analysis of multirate MC-CDMA in Rayleigh-fading channels with delay power spectrum exceeding the guard interval

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2006年第3期24卷 542-553页

作者： Kunnari, E Finatti, J Univ Oulu Ctr Wireless Commun FI-90014 Oulu Finland

Multicarrier code-division multiple access (MC-CDMA) is a promising multiplexing technique for future mobile radio systems, which require multirate transmission capability to efficiently support various services with wide range of data rates. In this paper, a generic performance analysis for the multicode and variable spreading factor multirate schemes in MC-CDMA is presented. Results comparing and pointing out notable differences in the error rate performance of these multirate schemes in conjunction with six different combining techniques are presented for the synchronous downlink and both the synchronous and asynchronous uplink. Furthermore, the analysis takes into account also the intersymbol interference caused by the multipath delay components exceeding the guard interval, which is commonly omitted in the literature.

关键词： delay spread multicarrier code-division multiple access (MC-CDMA) multicode multirate transmission subcarrier combining variable spreading factor (VSF)

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