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General differential modulation scheme for quasi-orthogonal space-time block codes with partial or full transmit diversity

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IET COMMUNICATIONS 2007年第2期1卷 256-266页

作者： Song, L.-Y. Burr, A. G. Univ York Dept Elect Commun Res Grp York YO10 5DD N Yorkshire England

A general and simple differential modulation scheme that can be applied to both partial-diversity quasi-orthogonal space-time block codes and full-diversity quasi-orthogonal space-time block codes is reported. A new class of quasi-orthogonal coding structures is presented for various number of transmit antennas. Differential encoding and decoding can be simplified to differential Alamouti codes by grouping the signals in the transmitted matrix and decoupling the detection of data symbols, respectively. For the codes with partial transmit diversity, the new scheme can achieve constant amplitude of transmitted signals, and avoid signal constellation expansion;in addition, it has a linear signal detector with very low complexity. Simulation results show that these partial-diversity codes can provide very useful results at low signal-to-nose ratio for current communication systems. For codes with full transmit diversity achieved by constellation rotation, the proposed scheme has performance equal to the best full-rate quasi-orthogonal schemes previously described in the literature with the benefit of a simpler detector. Moreover, a simple linear detector is also presented for the case when two orthogonal ASK constellations are used. Extension to more than four transmit antennas is also considered.

关键词： diversity reception linear signal detector differential detection amplitude shift keying partial transmit diversity full transmit diversity modulation coding differential modulation scheme block codes space-time codes diversity transmission Alamouti codes matrix transmission ASK constellations quasiorthogonal space-time block codes transmitting antennas orthogonal codes decoding

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Effect of error in channel state information on the channel capacity with QAM signalling and the design of robust signal constellations

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IET COMMUNICATIONS 2007年第6期1卷 1118-1125页

作者： Al-Askary, O. Slimane, S. B. Royal Inst Technol Dept Informat & Commun Technol Stockholm Sweden

The effects of channel estimation errors on the channel capacity of a discrete time, discrete input, infinite output Rayleigh fading channel are investigated. The case of conventional modulation methods such as phase shift keying (PSK) and quatrature amplitude modulation (QAM) is investigated at first where it was observed that the capacity degrades rapidly with increasing channel estimation errors. The effect of error in the channel estimation is similar to the effect of higher noise in the channel that depends on the transmitted signal. A genetic algorithm is used to optimise the signal constellation in order to maximise the capacity for a given finite number of signal points. The aim of trying to maximise the capacity is to estimate the remaining gap in performance between a traditional modulation scheme such as QAM and the best possible constellation that is optimised for the channel. The constellations obtained from the genetic algorithm are, in general, not directly implementable. A method to design practical robust signal constellations that overcome the effect of channel state information (CSI) error is presented. The robust signal constellations obtained show a performance that is very close to the otimal constellations. In this work, the probability distribution of the error in CSI is assumed to be known.

关键词： telecommunication signalling Rayleigh channels decoding channel estimation modulation coding channel estimation errors genetic algorithm QAM signalling quatrature amplitude modulation decoding schemes quadrature amplitude modulation discrete time discrete input infinite output Rayleigh fading channel channel state information channel coding channel capacity signal constellations genetic algorithms

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Packet scheduling in 3.5G high-speed downlink packet access networks: Breadth and depth

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IEEE NETWORK 2007年第1期21卷 41-46页

作者： Al-Manthari, Bader Hassanein, Hossam Nasser, Nidal Queens Univ Sch Comp Telecommun Res Lab Kingston ON K7L 3N6 Canada Univ Guelph Dept Comp & Informat Sci Guelph ON N1G 2W1 Canada

Forecasts for emerging mobile device markets anticipate that bandwidth will be squeezed by demanding applications like multimedia on demand. This will spur the need for data rates beyond what the upcoming 3G wireless cellular systems such as UNITS can offer. To boost the support for such high data rates, HSDPA, labeled as a 3.5G wireless system, has been introduced in Release 5 of UNITS technical specifications. HSDPA is a definite step toward meeting the "anywhere, anytime, and in any form" 4G communication concept. HSDPA promises a peak data rate of up to 10 Mb/s, five times larger than the data rate offered by 3G systems. In order to support such high data rates, HSDPA relies on many new technologies, among which is packet scheduling. In this article we provide breadth and depth related issues of packet scheduling in HSDPA, discuss state-of-the-art HSDPA scheduling algorithms in terms of their objectives, advantages, and limitations, and suggest further research issues that need to be addressed. In addition, we propose a packet scheduling algorithm for data traffic in HSDPA. Simulation results demonstrate the effectiveness of the proposed algorithm.

关键词： Scheduling algorithm Downlink Multiaccess communication Throughput modulation coding Radio control 3G mobile communication Radio network Media Access Protocol Algorithm design and analysis

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Design of a DVB-T/H COFDM receiver for portable video applications

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IEEE COMMUNICATIONS MAGAZINE 2007年第8期45卷 112-120页

作者： Chen, Lei-Fone Lee, Chen-Yi Natl Chiao Tung Univ Dept Elect Engn Hsinchu Taiwan

Mobile video services have generated a lot of interest recently. To reach a cost-effective solution, design trade-offs among system performance, hardware complexity, and power consumption must be considered in the early design phase of such applications. In this article, we present a system overview, simulation platform, and hardware design of a DVB-T/H baseband receiver. Starting with a design platform, several algorithms on both inner and outer receivers are developed to meet target system performance under different channels. Then, system architecture and related key modules are explored, taking into account both silicon area and power consumption. Finally, several design issues related to the integration of the proposed DVB-T/H inner and outer receivers are addressed.

关键词： Digital video broadcasting Circuits Transmitters OFDM modulation Baseband modulation coding TV receivers RF signals Source coding Radio frequency

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Medium access control protocol design for vehicle-vehicle safety messages

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2007年第2期56卷 499-518页

作者： Xu, Qing Mak, Tony Ko, Jeff Sengupta, Raja PINC Solut Inc Berkeley CA 94709 USA Univ Calif Berkeley Dept Civil & Environm Engn Berkeley CA 94720 USA Calif Partners Adv Transit & Highways Richmond CA 94804 USA

We propose a medium access control protocol design for a vehicle to send safety messages to other vehicles. We develop a Quality-of-Service (QoS) model for safety messages that are consistent with the active vehicle safety systems literature. Each message has a range and useful lifetime. The QoS target has each message received with high probability within its specified lifetime by each vehicle within its specified range. The protocol design is based on rapidly rebroadcasting each message multiple times within its lifetime in combination with the 802.11 Distributed Coordination Function. This makes the design compatible with emerging standards for Dedicated Short-Range Communication. Six different design variations are proposed. We derive equations and develop a simulation tool to assess the performance of the designs. Using these, we identify the best and most easily implemented designs. Design performance depends on the number of rebroadcasts, power, modulation, coding, and vehicular traffic volumes. We show that under certain assumptions on the loss probability tolerated by safety applications, the design is able to transport safety messages in *** hoc networks.

关键词： Media Access Protocol Access protocols Vehicle safety Quality of service Vehicles Communication standards Equations modulation coding Telecommunication traffic Traffic control

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Scheduling schemes for multimedia service in wireless OFDM systems

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IEEE WIRELESS COMMUNICATIONS 2007年第5期14卷 99-105页

作者： Zhu, Haiying Julie Hafez, Roshdy H. M. Carleton Univ Dept Syst & Comp Engn Ottawa ON K1S 5B6 Canada

Scheduling schemes play a key role in the system performance of broadband wireless systems such as WLANs/WMANs. Maximal SNR and Round Robin are two conventional scheduling strategies that emphasize efficiency and fairness, respectively. The Proportional Fair scheme provides a trade-off between efficiency and fairness, and has been well Studied in TDMA and CDMA systems. In this article we extended the PF scheduling scheme to OFDM-based BWSs (OPF). In addition, we propose three variations: Adaptive OPF (AOPF), Multimedia AOPF (MAOPF), and Normalized MAOPF (NMAOPF) in order to meet the QoS requirements for multirate services in multimedia systems. The adaptive modulation and coding schemes in time varying and frequency selective fading are considered. The system performances of the algorithms are compared in terms of efficiency (throughput and mean packet delay) and fairness (user satisfaction rate and average user rate). Joint physical and media access control layer simulation results show that AOPF and MAOPF can improve throughput at the cost of fairness, and NMAOPF can provide the highest throughput without losing fairness.

关键词： Multimedia systems OFDM Throughput System performance Round robin Time division multiple access Multiaccess communication Adaptive systems modulation coding Fading

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Optimising quasi-orthogonal STBC through group-constrained linear transformation

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IET COMMUNICATIONS 2007年第3期1卷 373-381页

作者： Yuen, C. Guan, Y. L. Tjhung, T. T. Inst Infocomm Res Singapore 119613 Singapore Nanyang Technol Univ Sch Elect & Elect Engn Singapore 639798 Singapore

The generic algebraic structure of a quasi-orthogonal space-time block code (QO-STBC) has been derived, and group-constrained linear transformation (GCLT) as a mean to optimise the diversity and coding gains of a QO-STBC with square or rectangular QAM constellations has been proposed. Compared with QO-STBC with constellation rotation (CR), QO-STBC with GCLT requires only half the number of symbols for joint detection, hence lower maximum-likelihood decoding complexity. The optimum GCLT parameters for QO-STBC with square QAM constellation have been derived analytically. The optimised QO-STBCs with GCLT are able to achieve full-transmit diversity and have negligible performance loss compared with QO-STBCs with CR at the same code rate.

关键词： GCLT maximum likelihood decoding block codes space-time codes group-constrained linear transformation algebraic codes QO-STBC quadrature amplitude modulation quasiorthogonal space-time block code diversity optimisation orthogonal codes generic algebraic structure modulation coding maximum-likelihood decoding complexity rectangular QAM constellations

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Iterative low-complexity multi-user detection for asynchronous multi-sequence signalling based bit-interleaved coded modulation code division multiple access systems

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IET COMMUNICATIONS 2007年第4期1卷 628-637页

作者： Tseng, D-F. Lu, K-C. Natl Taiwan Univ Sci & Technol Dept Elect Engn Taipei 106 Taiwan

An uplink direct sequence spread spectrum communications systems employing a multi-sequence model over a quasi-static frequency-selective fading channel is considered. In analogy with bit-interleaved coded modulation (BICM) technique, a group of bits at the output of a bit-wise interleaver is mapped uniquely to a complex signalling vector belonging to an orthogonal plane sequence modulation signal space, which is constructed over a set of expanded signature sequences. This transmission system provides not only bandwidth efficiency offered by additional signal planes but also time diversity resulting from the BICM technique. It is observed that at high system traffic load error performance could degrade substantially due to user cross-correlations, multi-access asynchronism as well as channel frequency selectivity. The authors employ a 'turbo principle' receiver, consisting of a soft interference cancellation scheme, soft demappers and maximum a posteriori decoders, to avert this capacity loss by exploiting the serially concatenating structure at the transmitter. After simple mathematical manipulation, a soft space-time linear minimum mean-square error multi-user detector could even be explored on the basis of per signal plane per user. Both analytical performance-bound and computer simulation of the proposed framework in terms of bit-error rate (BER) are revealed. Further, performance comparisons with convolutionally coded and conventional bandwidth-efficient coded direct sequence code division multiple access systems under the same system conditions are illustrated. The authors have also investigated the impact of labelling maps on the BER performance.

关键词： multiuser detection space-time linear minimum mean-square error multiuser detector code division multiple access systems fading channels turbo principle receiver modulation coding telecommunication traffic system traffic load error code division multiple access least mean squares methods quasi-static frequency-selective fading channel direct sequence spread spectrum communications systems asynchronous multisequence signalling iterative low-complexity multiuser detection bit-interleaved coded modulation soft interference cancellation scheme interference suppression soft demappers error statistics bit-error rate bandwidth efficiency spread spectrum communication telecommunication signalling maximum a posteriori decoders

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Implementable wireless access for B3G networks - Part III: Complexity reducing transceiver structures

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IEEE COMMUNICATIONS MAGAZINE 2007年第3期45卷 98-104页

作者： Dohler, Mischa McLaughlin, Stephen Sweeney, Peter Hanzo, Lajos Univ Edinburgh Edinburgh EH8 9YL Midlothian Scotland Univ Surrey Guildford GU2 5XH Surrey England Univ Southampton Southampton SO9 5NH Hants England

This article presents a comprehensive overview of some of the research conducted within Mobile VCE's Core Wireless Access Research Programme,1 a key focus of which has naturally been on MIMO transceivers. The series of articles offers a coherent view of how the work was structured and comprises a compilation of material that has been presented in detail elsewhere (see references within the article). In this article MIMO channel measurements, analysis, and modeling, which were presented previously in the first article in this series of four, are utilized to develop compact and distributed antenna arrays. Parallel activities led to research into low-complexity MIMO single-user space-time coding techniques, as well as SISO and MIMO multi-user CDMA-based transceivers for B3G systems. As well as feeding into the industry's in-house research program, significant extensions of this work are now in hand, within Mobile VCE's own core activity, aiming toward securing major improvements in delivery efficiency in future wireless systems through cross-layer operation.

关键词： Transceivers Radio communication Transmitting antennas Convolutional codes Quadrature phase shift keying Fading Error analysis Concatenated codes Channel coding modulation coding

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Radio resource management in MIMO-OFDM-based wireless infrastructure mesh networks: Issues and approaches

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IEEE COMMUNICATIONS MAGAZINE 2007年第11期45卷 100-107页

作者： Niyato, Dusit Hossain, Ekram Univ Manitoba Dept Elect & Comp Engn Winnipeg MB R3T 2N2 Canada TR Labs Winnipeg MB Canada

We present a survey on the radio resource management issues in MIMO-OFDM-based infrastructure wireless mesh networks. The major components in radio resource management (i.e., scheduling and admission control) and related research issues are discussed. We review related work in the literature. We propose a game-theoretic model for admission control in IEEE 802.11n-based WMNs using the MIMO-OFDM technology. The proposed scheme uses Q-learning, which is a reinforcement learning algorithm, to gain knowledge on system performance. Then this knowledge is used to determine payoff for the game formulation to obtain the Nash equilibrium for the decision on admitting or rejecting a new connection at a mesh router.

关键词： Resource management Mesh networks MIMO Transmitting antennas Receiving antennas Admission control Diversity reception modulation coding Algorithm design and analysis Performance gain

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