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Wireless Communications, IEEE Transactions on

Issue 6 • Date Nov. 2004

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Displaying Results 1 - 25 of 70
  • Table of contents

    Publication Year: 2004 , Page(s): c1 - 1866
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  • IEEE Transactions on Wireless Communications publication information

    Publication Year: 2004 , Page(s): c2
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    Freely Available from IEEE
  • Performance analysis of an FFH/BFSK receiver with product-combining in a fading channel under multitone interference

    Publication Year: 2004 , Page(s): 1867 - 1872
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB) |  | HTML iconHTML  

    The bit-error probability (BEP) is evaluated for a fast frequency-hopping binary frequency-shift-keying (FFH/BFSK) spread-spectrum communication system over Rician fading channels in the presence of worst-case multitone jamming (MTJ) and additive white Gaussian noise (AWGN). A diversity reception scheme of product-combining is applied at the receiver. Two types of MTJ models, namely n=1-band MTJ and independent MTJ, are considered in this letter. To obtain the final decision statistics, the closed-form or a single finite integral expressions of cumulative distribution functions (CDFs) of the ratio of two square-law detectors' outputs per hop are derived. According to the numerical results, it is shown, unlike the known knowledge for the AWGN channel, that independent MTJ is more harmful than n=1-band MTJ for the product-combining receivers (L≥2) in fading channels. View full abstract»

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  • Decision feedback differential detection for differential orthogonal space-time modulation with APSK signals over flat-fading channels

    Publication Year: 2004 , Page(s): 1873 - 1878
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    Differential orthogonal space-time modulation (DOSTM) with amplitude/phase shift keying (APSK) signals has been recently proposed to improve the data throughput of the DOSTM with PSK signals over quasi-static channels. In this letter, decision feedback differential detection (DF-DD) based on linear prediction is presented for the DOSTM with APSK Signals (DOSTM-APSK) over flat-fading channels. The proposed DF-DD offers better performance than the differential detection when the channel experiences fast fading. The coefficients of the linear prediction based DF-DD can be obtained by an adaptive recursive least-squares algorithm, where the channel statistics are not needed. The proposed DF-DD is also applicable to the general unitary differential space-time modulation. View full abstract»

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  • Iterative transmitter and receiver optimization for CDMA networks

    Publication Year: 2004 , Page(s): 1879 - 1884
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB) |  | HTML iconHTML  

    Optimization of the capacity of a single-cell code-division multiple-access (CDMA) system, both from the perspective of the maximum number of users that can be served at a required quality of service level and from the information theoretic perspective, has been recently shown to be achieved by the same joint transmit and receive strategies. We propose an alternating minimization based iterative algorithm that updates the transmitters and the corresponding receivers of the users. The algorithm is suitable for online implementation, and the objective function is suitable for extension to multicell networks, both of which are in contrast with the previously proposed algorithms. We show that the algorithm is provably convergent to the optimum signature sequences and the corresponding receivers. View full abstract»

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  • BEM-based SISO detection of orthogonal space-time block codes over frequency flat-fading channels

    Publication Year: 2004 , Page(s): 1885 - 1889
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    The expectation-maximization algorithm for maximum a posteriori (MAP) estimation of a random vector is applied to the problem of detection of orthogonal space-time block codes over time-selective Rayleigh fading channels. This results in a soft-in soft-out detection algorithm suitable for iterative detection/decoding schemes. Simulation results show that the error performance of the proposed detection algorithm is very close to that of a MAP detector endowed with an ideal knowledge of the channel state if the fading rate is not too fast. View full abstract»

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  • Closed-loop quasi-orthogonal STBCs and their performance in multipath fading environments and when combined with turbo codes

    Publication Year: 2004 , Page(s): 1890 - 1896
    Cited by:  Papers (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB) |  | HTML iconHTML  

    Quasi-orthogonal space-time block codes (QO-STBCs) achieve full code rate at the expense of loss in diversity gain. We propose two feedback methods for QO-STBCs to achieve full diversity and full code rate. In the first method, signals radiated from various antennas are rotated by phasors according to feedback from the receiver, whereas the second method is based upon antenna weighting/selection. For high to moderate feedback error rates, it is demonstrated that the proposed methods outperform the quantized transmit beamformer. The performance improvement is also investigated for these closed-loop methods when the transmitted signal is error control coded. View full abstract»

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  • Application of NB/WB AMR speech codecs in the 30-kHz TDMA system

    Publication Year: 2004 , Page(s): 1897 - 1901
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    A new system enhancement method is proposed for the EIA/TIA-136 system offering both channel operational range extension and improved performance within the current operational range. The existing time-division multiple-access (TDMA) (136) speech codec, the IS-641 enhanced full rate vocoder, operates at a fixed bit rate and does not allow the reallocation of bits to channel error protection as channel conditions degrade. The research presented here investigates the application of the narrow-band adaptive multirate (NB-AMR) speech codec and the wide-band AMR (WB-AMR) codec, both originally designed for the 200 kHz GSM channel, in the TDMA (TIA/EIA-136) 30-kHz system. In particular, we investigate adaptively allocating bits between NB/WB speech coding and error control coding within the limited channel bandwidth. Four modes out of 17 have been carefully chosen for the new TDMA/AMR system. Switching between codec rates as channel conditions change produces range extension below a C/I of 15 dB while also improving performance in the existing operational range above 15 dB. We keep the time slot formats unchanged so that our method is completely compatible with existing 136 systems. View full abstract»

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  • Initial weight computation method with rapid convergence for adaptive array antennas

    Publication Year: 2004 , Page(s): 1902 - 1905
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB) |  | HTML iconHTML  

    This paper presents a rapid initial weight computation method for adaptive array antennas. The proposed method estimates a correlation matrix and a correlation vector, where the correlation matrix is estimated using not only received samples with the desired signal, but also those before starting the transmission of the desired signal. The proposed method reduces the number of known symbols required for weight convergence. Furthermore, the combined use of the proposed method and the decision-feedback minimum mean square error combining method significantly improves weight convergence. Numerical results show that the combined method converges an array with sixteen antennas by using less than ten known symbols. View full abstract»

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  • Globally optimal transmitter placement for indoor wireless communication systems

    Publication Year: 2004 , Page(s): 1906 - 1911
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    A global optimization technique is applied to solve the optimal transmitter placement problem for indoor wireless systems. An efficient pattern search algorithm - DIviding RECTangles (DIRECT) of Jones et al.- has been connected to a parallel three-dimensional radio propagation ray tracing modeler running on a 200-node Beowulf cluster of Linux workstations. Surrogate functions for a parallel wideband code-division multiple-access (WCDMA) simulator were used to estimate the system performance for the global optimization algorithm. Power coverage and bit-error rate are considered as two different criteria for optimizing locations of a specified number of transmitters across the feasible region of the design space. This paper briefly describes the underlying radio propagation and WCDMA simulations and focuses on the design issues of the optimization loop. View full abstract»

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  • Bit-interleaved space-time coded modulation with iterative decoding

    Publication Year: 2004 , Page(s): 1912 - 1917
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    Bit-interleaved space-time coded modulation (BI-STC), which combines serial concatenation of bit-interleaved coded modulation (BICM) with space-time block codes, can effectively exploit the available diversity in space and time under various fading conditions. In this letter, we propose to use iterative decoding to further improve the performance of BI-STC by exploiting the concatenating structure of the codes. The decoding metric is therefore modified to fit for the iterative process, and the derived error bounds suggest that set-partition labeling instead of gray labeling should be used when considering iterative decoding. View full abstract»

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  • Iterative channel estimation for turbo equalization of time-varying frequency-selective channels

    Publication Year: 2004 , Page(s): 1918 - 1923
    Cited by:  Papers (80)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB) |  | HTML iconHTML  

    We investigate turbo equalization, or iterative equalization and decoding, as a receiver technology for systems where data is protected by an error-correcting code, shuffled by an interleaver, and mapped onto a signal constellation for transmission over a frequency-selective channel with unknown time-varying channel impulse response. The focus is the concept of soft iterative channel estimation, which is to improve the channel estimate over the iterations by using soft information fed back from the decoder from the previous iteration to generate "extended training sequences" between the actual transmitted training sequences. View full abstract»

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  • A low-complexity enhancement to suboptimal CDMA receivers

    Publication Year: 2004 , Page(s): 1924 - 1927
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB) |  | HTML iconHTML  

    Conventional matched-filter detectors for code-division multiple-access (CDMA) systems suffer from multiple-access interference (MAI) caused by nonzero correlation between spreading codes at the receiver. A host of advanced detector structures have been proposed to reduce the effect of MAI and, hence, improve performance. However, most multiuser detectors suffer from their relatively complex implementations. A simple method is proposed to improve the performance of the conventional detector by detecting and correcting decision errors at its output without the use of forward error correcting (FEC) codes. The proposed post-detection error control method is shown to substantially improve the performance of the conventional detector, but has a much lower complexity than most other multiuser detectors. View full abstract»

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  • Iterative EM receiver for space-time coded systems in MIMO frequency-selective fading channels with channel gain and order estimation

    Publication Year: 2004 , Page(s): 1928 - 1935
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB) |  | HTML iconHTML  

    An iterative receiver for a space-time trellis coded system in frequency-selective fading channel is proposed. It performs channel gain estimation and sequence detection by using the expectation-maximization (EM) algorithm. Channel order estimation is included in the receiver to avoid unnecessary trellis computations by using the conditional model order estimator (CME). In addition, three modifications to the original CME criterion are proposed to improve the estimation accuracy. Simulation results show that the proposed receiver has a slight degradation in frame error rate performance to the known channel maximum likelihood receiver. Moreover, it outperforms the conventional fixed long-tap length EM receiver with a lesser complexity. Furthermore, the proposed modifications to the CME criterion improve the channel order estimation accuracy, thus minimizing unnecessary computations. View full abstract»

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  • On strategies of multiuser MIMO transmit signal processing

    Publication Year: 2004 , Page(s): 1936 - 1941
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB) |  | HTML iconHTML  

    In this letter, we introduce five different strategies of linear transmit signal processing for multiuser multiple-input multiple-output (MIMO) systems and provide performance comparisons in terms of maximum throughput in both uncorrelated and correlated channels when the number of transmit antennas is much larger than the number of receive antennas. It is shown that the multiuser MIMO schemes are preferable to time-division multiple-access (TDMA)-based MIMO schemes, hence demonstrating the power of multiuser MIMO signal processing. Our work also indicates possibilities for future research in finding efficient suboptimal algorithms. As an example, we show that our multiuser MIMO decomposition scheme can improve the maximum throughput compared to TDMA-based MIMO schemes for large number of transmit antennas or high transmit power. View full abstract»

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  • DOA and channel parameter estimation for wideband CDMA systems

    Publication Year: 2004 , Page(s): 1942 - 1947
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB) |  | HTML iconHTML  

    We consider the uplink of a direct-sequence code-division multiple-access system and we assume that the base station is endowed with a linear antenna array. Transmission takes place over a multipath channel and the goal is to estimate the channel parameters (path gains and delays) and the directions of arrival of the signal echoes from a user entering the network. We propose an estimator that operates in an iterative fashion and exploits knowledge of the transmitted symbols (training sequence). Compared to other existing schemes, it is simpler to implement as it reduces a complicated multidimensional optimization problem to a sequence of one-dimensional searches. Computer simulations indicate that the proposed scheme is useful even in applications over rapidly varying channels where the training sequence must be short compared with the channel decorrelation time. View full abstract»

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  • Adaptive Viterbi algorithm with ARQ for bounded complexity decoding

    Publication Year: 2004 , Page(s): 1948 - 1952
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    Adaptive bounded computational and memory requirements for a Viterbi decoder can be achieved using an error trapping Viterbi decoder algorithm initially develop for hybrid automatic repeat request (ARQ) implementations. Partial path metrics and a sliding window are used to eliminate unreliable paths in the decoder trellis thus reducing the computational and memory requirements. An ARQ is issued if all paths are eliminated. The algorithm is adaptive allowing the receiver to dynamically allocate memory and processing, to improve reliability or received packets, or to reject packets with lower reliability to avoid buffer overruns. The result is the ability to trade off resources versus delay and throughput. View full abstract»

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  • Space-time coding for MIMO systems with co-channel interference

    Publication Year: 2004 , Page(s): 1953 - 1958
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB) |  | HTML iconHTML  

    We consider the design of space-time codes for multiple-input multiple-output (MIMO) systems operated in the presence of co-channel interference (CCI). Based on the pairwise probability of error analysis, we develop a new design criterion that determines the code robustness to CCI (CCI diversity gain). We further develop an algebraic framework for constructing space-time codes that jointly optimize the fading and CCI diversity gains. The proposed framework is general for arbitrary numbers of transmit antennas and quadrature amplitude modulation constellations. Numerical results that quantify the performance gains offered by the proposed techniques are also presented. View full abstract»

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  • Extending orthogonal block codes with partial feedback

    Publication Year: 2004 , Page(s): 1959 - 1962
    Cited by:  Papers (48)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB) |  | HTML iconHTML  

    During the last few years a number of space-time block codes have been proposed for use in multiple transmit antennas systems. We propose a method to extend any space-time code constructed for m transmit antennas to m p transmit antennas through group-coherent codes (GCCs). GCCs make use of very limited feedback from the receiver (as low as 1 bit). In particular the scheme can be used to extend any orthogonal code (e.g., Alamouti code) to more than two antennas while preserving low decoding complexity, full diversity benefits, and full data rate. View full abstract»

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  • A performance study of dual-hop transmissions with fixed gain relays

    Publication Year: 2004 , Page(s): 1963 - 1968
    Cited by:  Papers (318)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB) |  | HTML iconHTML  

    This letter presents a study on the end-to-end performance of dual-hop wireless communication systems equipped with nonregenerative fixed gain relays and operating over flat Rayleigh-fading channels. More specifically, it first derives generic closed-form expressions for the outage probability and the average probability of error when the relays have arbitrary fixed gains. It then proposes a specific fixed gain relay that benefits from the knowledge of the first hop's average fading power and compares its performance with previously proposed relay gains that in contrast require knowledge of the instantaneous channel state information of the first hop. Finally, the letter investigates the effect of the relay saturation on the performance of the systems under consideration. Numerical results show that nonregenerative systems with fixed gain relays have a comparable performance to nonregenerative systems with variable gain, more complex, relays. These results also show that relay saturation of these systems results in a minimal loss in performance. View full abstract»

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  • Generalized multiuser orthogonal space-division multiplexing

    Publication Year: 2004 , Page(s): 1969 - 1973
    Cited by:  Papers (151)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    This paper addresses the problem of performing orthogonal space-division multiplexing (OSDM) for downlink, point-to-multipoint communications when multiple antennas are utilized at the base station (BS) and (optionally) all mobile stations (MS). Based on a closed-form antenna weight solution for single-user multiple-input multiple-output communications in the presence of other receiver points, we devise an iterative algorithm that finds the multiuser antenna weights for OSDM in downlink or broadcast channels. Upon convergence, each mobile user will receive only the desired activated spatial modes with no cochannel interference. Necessary and sufficient conditions for the existence of OSDM among the number of mobile users, the number of transmit antennas at the BS, and the number of receive antennas at the MS, are also derived. The assumption for the proposed method is that the BS knows the channels for all MS's and that the channel dynamics are quasi-stationary. View full abstract»

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  • Rank constrained temporal-spatial matrix filters for CDMA systems

    Publication Year: 2004 , Page(s): 1974 - 1979
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    Efficient interference suppression techniques are needed to maximally utilize the potential gains of code-division multiple-access systems. In this letter, a receiver structure which combines multiuser detection (temporal filtering) and receiver beamforming (spatial filtering) in a multipath environment is considered. Following previous work, we model the receiver as a linear matrix filter and use the minimum mean-squared error (MMSE) as the performance criterion. Motivated by the high complexity of the optimum receiver, we propose rank constrained temporal-spatial filters which are simpler and near-optimum. The MSE is minimized subject to a structural constraint, using an iterative algorithm based on alternating minimization. The constraint on the receiver matrix filter narrows down the solution space, which helps to solve the optimization problem more efficiently. The constraint can be set appropriately by the system designer to achieve the desired tradeoff between performance and complexity. Numerical results indicate that a performance close to that of the optimum filter can be achieved with a simple iterative structure, even in highly loaded systems. Adaptive implementation of the rank constrained filters is derived. A new adaptive scheme is proposed which is a combination of the alternating minimization and the least mean squares methods. The convergence properties are investigated along with the effect of the number paths. View full abstract»

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  • Performance analysis of combined transmit selection diversity and receive generalized selection combining in Rayleigh fading channels

    Publication Year: 2004 , Page(s): 1980 - 1983
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    We analyze the average symbol error rate (SER) of M-PSK and M-QAM modulations with transmit antenna selection diversity (SD) and receive generalized selection combining (GSC) in Rayleigh fading channels. SER formulas are derived in closed form, and numerical results show that transmit SD and receive GSC are flexible to tradeoff performance for complexity. View full abstract»

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  • Quantitative analysis of a new method for real-time generation of SNR estimates for digital phase modulation signals

    Publication Year: 2004 , Page(s): 1984 - 1988
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    A new method of estimating the signal-to-noise ratio for M-PSK receivers was presented previously, which derives that estimate from the locked-state value of a new family of carrier lock detectors. A quantitative analysis is undertaken in which it is shown that this method requires significantly less hardware and/or software resources than estimation from the received signal's error rate, is irrespective of the data sequence, and necessitates far fewer symbols in order to arrive at an equally accurate estimate. View full abstract»

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  • Resource allocation for FDMA-based regenerative multihop links

    Publication Year: 2004 , Page(s): 1989 - 1993
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    An approximate but explicit fractional bandwidth and power allocation algorithm for orthogonal regenerative frequency-division multiple-access-based multihop communication systems over ergodic flat-fading channels is presented. The exposed algorithm is assessed for a two-hop scenario, where it is shown to operate within 10% of the optimum resource allocation. The achieved end-to-end capacity is up to 45% higher if compared to a trivial allocation strategy with equal resources. View full abstract»

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The IEEE Transactions on Wireless Communications publishes high-quality manuscripts on advances in the state-of-the-art of wireless communications.

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Editor-in-Chief
Jeff Andrews
Cullen Trust for Higher Education Endowed Professor of Engineering