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63rd IEEE Vehicular Technology Conference

作者： Ishihara, Koichi Takeda, Kazuaki Adachi, Fumiyuki Tohoku Univ Dept Elect & Commun Engn Grad Sch Engn Sendai Miyagi 980 Japan

ISBN: (纸本)9780780393912

Frequency-domain equalization (FDE) based on minimum mean square error (MMSE) criterion can significantly improve the BER performance of DS- and MC-CDMA signal transmissions in a severe frequency-selective fading channel. However, since the frequency-distorted signal cannot be completely equalized, the residual inter-code interference (ICI) limits the BER performance improvement. In 4G systems, much higher variable rate data services than in the present 3G systems are required. Orthogonal multicode transmission technique has flexibility in offering variable rate services. However, the BER performance degrades as the number of parallel codes increases. In this paper, we propose a frequency-domain soft interference cancellation (FDSIC) for multicode DS- and MC-CDMA signal transmissions and their achievable BER performances are evaluated by computer simulation.

关键词： DS-CDMA MC-CDMA Frequency-domain equalization(FDE) multicode Interference cancellation

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Performance of a CDMA system employing AMC and multicodes in the presence of channel estimation errors

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IEEE TRANSACTIONS ON COMMUNICATIONS 2008年第2期56卷 189-193页

作者： Kwan, Raymond Leung, Cyril Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

The impact of channel state estimation errors in a CDMA system employing adaptive modulation and coding in conjunction with multicodes is studied. The channel is modelled as a finite-state Markov chain and the performances using (1) a simple moving average (SMA) filter (2) a hidden Markov model (HMM) filter to estimate the channel state are compared. The results show that the HMM filter is more robust and provides a significant throughput improvement over the SMA filter, especially when the channel estimate is quite noisy or the normalized Doppler rate is small.

关键词： CDMA adaptive modulation and coding multicode imperfect channel estimation Rayleigh fading hidden Markov model

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On the comparisons of system performance and capacity of asynchronous STBC MC-CDMA multirate access schemes

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WIRELESS COMMUNICATIONS & MOBILE COMPUTING 2008年第10期8卷 1277-1295页

作者： Hu, Xiaoyu Chew, Yong Huat Stevens Inst Technol Dept Elect & Comp Engn Hoboken NJ 07030 USA Inst Infocomm Res Singapore Singapore Natl Univ Singapore Dept Elect & Comp Engn Singapore 117548 Singapore

Three multirate access schemes, multicode, variable spreading gain (VSG), and spectral overlaid multiple-symbol-rate (MSR), for asynchronous space-time block coded (STBC) multicarrier code division multiple access (MC-CDMA) systems are proposed. The three possible spectral overlaid configurations for MSR systems are also investigated. The expressions to evaluate the multiple access interferences, bit error rate (BER) performances, and system capacities of a antenna STBC MC-CDMA using the three multirate access schemes are obtained. Transmit power allocation is adjusted according to the service rates and the number of active users in each service class to maintain the link quality and to improve the system capacity. Our numerical results show that systems with multicode access scheme using orthogonal Gold spreading codes and with VSG access scheme have similar system performance and capacity, and both perform in general better than systems with MSR access scheme of any spectrum configurations. In case when non-orthogonal Gold codes are used, multicode access scheme shows degradation in the system capacity as compared to VSG, due to the presence of larger self-interference (SI) among the codes used by each user. The achievable capacities for the three spectral overlaid configurations of MSR multirate systems are also compared. Copyright (C) 2007 John Wiley & Sons, Ltd.

关键词： MC-CDMA space-time code multicode variable spreading gain (VSG) multiple-symbol-rate (MSR) BER performance system capacity

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Frame time-hopping patterns in multirate optical CDMA networks using conventional and multicode schemes

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IEEE TRANSACTIONS ON COMMUNICATIONS 2005年第5期53卷 863-875页

作者： Forouzan, AR Nasiri-Kenari, M Rezaee, N Univ Canterbury Dept Elect & Comp Engn Christchurch 8005 New Zealand Univ Tehran Dept Elect & Comp Engn Tehran 14399 Iran Sharif Univ Technol Dept Elect Engn Tehran 113659363 Iran

A class of generalized optical orthogonal codes (OOCs), namely, frame time-hopping (FTH) patterns with an extremely large cardinality, are studied for implementing multirate and multiservice (MR/MS) optical CDMA (OCDMA) networks. Conventional MR/MS methods, namely variable spreading rate and parallel mapping,are considered. Using FTH patterns, the problem of low OOC code cardinality in conventional MR/MS schemes is removed. Moreover, several new multicode methods, using subcode concatenation scheme, are proposed for MR/MS OCDMA. The proposed multicode schemes present flexibility for supporting MR/MS applications such as lower implementation complexity and cost, less need for service synchronization, and finally lower link power budget. Multiple-access performances of the systems are evaluated using saddle-point approximation methods considering photodetector shot-noise, dark current, and circuit thermal noise. The results show that the conventional parallel mapping outperforms the other schemes in high received powers, and the proposed multicode method, using Walsh subcode along with difference modulation, presents the best performance in low received powers for the cases considered.

关键词： frame time-hopping (FTH) multicode multirate (MR) multiservice (MS) optical CDMA optical orthogonal codes (OOCs) parallel mapping subcode concatenation variable spreading rate Walsh code

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Optimal power distribution control for multicode MC-CDMA with zero-forcing successive interference cancellation

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EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING 2005年第5期2005卷 718-729页

作者： Tan, MZ Ibars, C Bar-Ness, Y Agere Syst Allentown PA 18109 USA Ctr Tecnol Telecommun Catalunya Barcelona 08034 Spain New Jersey Inst Technol Ctr Commun & Signal Proc Res Dept Elect & Comp Engn Newark NJ 07102 USA

Multicarrier CDMA (MC-CDMA) has become a promising candidate for future wireless multimedia communications for its robustness to frequency-selective fading and its flexibility in handling multiple data rates. Among different multirate access schemes, multicode MC-CDMA is attractive for its high performance, good flexibility in rate matching, and low complexity. However, its performance is limited by self-interference (SI) and multiuser interference (MUI). In this paper, a zero-forcing successive interference cancellation (ZF-SIC) receiver is used to mitigate this problem for multicode MC-CDMA. Furthermore, optimal power distribution control (PDC), which minimizes each user's bit error rate (BER), is considered. Our results show that, in correlated Rayleigh fading channels, the ZF-SIC receiver integrated with the optimal PDC dramatically improves the performance of the multicode MC-CDMA system in comparison with other receivers proposed in the literature. Moreover, the optimal PDC significantly outperforms the PDC based on equal BER criterion, particularly under a short-term transmit power constraint.

关键词： multicode multicarrier CDMA zero-forcing successive interference cancellation power distribution control

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Gilles Apap's Mozart cadenza and expanding musical competences of twenty-first-century musicians and music educators

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MUSIC EDUCATION RESEARCH 2008年第1期10卷 15-39页

作者： Webb, Michael Univ Sydney Sydney Conservatorium Mus Sydney NSW 2006 Australia

In western musical contexts at global and local levels, musicians are becoming increasingly involved in what might be termed multicode music making and are expanding their musical competences. In this article I consider the practical and cognitive implications of such an expanding of competences for music education at various levels. Combining ethnomusicological and music educationist perspectives, I ground the discussion in a reading of various media texts, a consideration of pedagogical trends, a field observation, and instances of autoethnography. Engaging with recent discussions of ethnomusicology's notions of bimusicality and intermusicality, I conceptualise plural musical practices according to metaphors of growth, and stretching or reforming, both within and outwards from a core of culturally grounded musical skills, values and understandings. I propose a framework for fostering the expanding of musical competences, offer brief, personal case studies and conclude by referring to emerging literature on the training of future music educators.

关键词： expanding musical competences multicode bimusicality intermusicality

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Downlink scheduling schemes for CDMA networks with adaptive modulation and coding and multicodes

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2007年第10期6卷 3668-3677页

作者： Kwan, Raymond Leung, Cyril Simon Fraser Univ Sch Engn Sci Burnaby BC V5A 1S6 Canada Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

For the problem of allocating radio resources in the downlink of a CDMA network studied in [1], the modulation and coding schemes, numbers of multicodes, and transmit powers used for all mobile stations (MS's) are jointly chosen so as to maximize the total transmission bit rate during each scheduling interval, subject to certain constraints. The approach employs discrete mathematical programming, which is potentially complex, and analytical solutions are not available. In this paper, sub-optimal approaches are examined. In particular, analytical expressions are derived for optimal resource allocation involving a single MS. Based on the single-MS solution, a sub-optimal, sequential optimization procedure for multiple MS's is presented. Numerical results show that when the order for allocating resources to MS's is judiciously chosen based on the MS channel conditions and/or traffic loads, the sequential solution is an attractive alternative to the more complex joint optimization. This is especially true when radio resources are scarce.

关键词： adaptive modulation and coding CDMA downlink scheduling high-speed packet data multicode

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Performance of a new premulticoded multicarrier DS-CDMA system in Nakagami fading

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IEEE TRANSACTIONS ON COMMUNICATIONS 2007年第7期55卷 1363-1373页

作者： Cao, Yewen Tjhung, Tjeng Thiang Ko, Chi Chung Shandong Univ Jinan 250100 Peoples R China Inst Infocomm Res Singapore 119613 Singapore Natl Univ Singapore Dept Elect & Comp Engn Singapore 119260 Singapore

In this paper, we proposed a new multicarrier, direct sequence code division multiple access, the so-called premulticoded MC-DS-CDMA system. In this scheme, the basic MC-DS-CDMA system is augmented with a precoder and a multicode encoder at the transmitter. The multicode encoder is an inverse Walsh-Hadamard transform (IWHT) unit, while the precoder is a recently suggested "constant amplitude" encoder that guarantees that the IWHT output stream has binary level. While IWHT, multicarrier (MC) transmission, and direct sequence spreading provide us with frequency diversity, the constant amplitude precoder ensures that the transmitted waveform is spread BPSK signal, minimizing peak to average-power ratio (PAPR) problem. The multicode and (MC) combination also addresses the need for flexible high data rate services in present day wireless communications. In the receiver, after matched filtering or correlation demodulation for each subcarrier and WHT operation, a detection strategy based on minimum-mean-square-error (MMSE) criterion is used. We have derived an upper bound for the bit error rate (BER) performance in Nakagami fading channel. Numerical results are compared with those obtained from a single carrier DS-CDMA. system (SC-DS-CDMA) and a MC-DS-CDMA scheme without the precoding and IWHT units. We show that our proposed MC-DS-CDMA scheme has a much better BER performance compared with both of these schemes.

关键词： DS-CDMA MMSE detection multicarrier CDMA multicode

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On joint order statistics in correlated Nakagami fading channels

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IEEE COMMUNICATIONS LETTERS 2007年第9期11卷 717-719页

作者： Kwan, Raymond Ho, Paul Leung, Cyril Simon Fraser Univ Sch Engn Sci Burnaby BC V5A 1S6 Canada Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

In this letter, the joint probability density function (pdf) of the order statistics for a set of correlated Nakagami-m fading channels is derived. This result is useful in analyzing the performance of a variety of diversity schemes which involve branch selection. The derivation also yields a computationally efficient method for obtaining the marginal pdf of the p-th order statistic for a set of correlated Nakagami-m fading channels.

关键词： adaptive modulation and coding multicode imperfect channel estimation CDMA Nakagami fading

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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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65th IEEE Vehicular Technology Conference

作者： Kunnari, Esa Iinatti, Jari Univ Oulu CWC FI-90014 Oulu Finland

ISBN: (纸本)9781424402656

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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