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Spread Spectrum Techniques and Applications, 2004 IEEE Eighth International Symposium on

Date Aug. 30 2004-Sept. 2 2004

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  • Eighth IEEE International Symposium on Spread Spectrum Techniques and Applications - Programme and Book of Abstracts (IEEE Cat. No.04TH8738)

    Publication Year: 2004
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    Freely Available from IEEE
  • ISSSTA 2004 Table of Contents

    Publication Year: 2004 , Page(s): ii - xiii
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    Freely Available from IEEE
  • General Chair's Welcome

    Publication Year: 2004 , Page(s): xiv
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    Freely Available from IEEE
  • ISSSTA 2004 Organisation Committees

    Publication Year: 2004 , Page(s): xv
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    Freely Available from IEEE
  • Expectation maximization based detection for V-BLAST MIMO communication systems and performance evaluation

    Publication Year: 2004 , Page(s): 255 - 259
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    Maximum likelihood naturally arises as the target criterion for detection in many applications, as well as in layered space-time communications. Nevertheless, existing algorithms for maximum likelihood decoding have computational complexity that is not feasible for implementation in practical systems. Applying the expectation maximization algorithm to the maximum likelihood detection of layered space-time codes, we iteratively maximize the conditional log-likelihood of a single layer, rather than maximizing the intractable likelihood function of all layers. Computer simulations demonstrate the efficiency of the proposed detection scheme, in comparison to the well known ing and cancelling detection scheme. View full abstract»

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  • Achievable rates for MIMO fading channels with limited feedback

    Publication Year: 2004 , Page(s): 1 - 6
    Cited by:  Papers (10)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB) |  | HTML iconHTML  

    Channel information at the transmitter can simplify the coding scheme and increase the achievable data rate over a multiple-input multiple-output (MIMO) fading channel. Feedback from the receiver can be used to specify a precoding matrix, which selectively activates the strongest channel modes. We evaluate the sum data rate per receive antenna when the precoding matrix is quantized with a random vector quantization (RVQ) scheme, assuming a matched filter, or linear minimum mean squared error (MMSE) receiver. Our results are asymptotic as the number of transmit and receive antennas increases with fixed ratio, for a fixed number of feedback bits per dimension. Numerical results show that given a target spectral efficiency, the amount of feedback required by the linear MMSE receiver is only slightly more than that required by the optimal receiver, whereas the matched filter can require significantly more feedback. We also compare these results with a simpler reduced-rank scheme for quantizing the precoding matrix. View full abstract»

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  • Layered encoding for low complexity detection of high-order modulations in MIMO channels

    Publication Year: 2004 , Page(s): 7 - 11
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (793 KB) |  | HTML iconHTML  

    Mobile receiver complexity persists as one of the key areas of concern in the adoption of MIMO technologies for systems such as high-speed downlink packet access (HSDPA) in UMTS. This is particularly the case for high-order modulation schemes such as 16-QAM and 64-QAM, where optimum a posteriori probability (APP) detection becomes too complex, and sub-optimal detection based on serial or parallel interference cancellation performs poorly. The above issues are successfully tackled by introducing a judicious layered encoding process at the transmitter, which once appropriately exploited at the receiver, allows considerable reductions in computational complexity in addition to improvements in performance. View full abstract»

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  • Low complexity receiver design for MIMO bit-interleaved coded modulation

    Publication Year: 2004 , Page(s): 12 - 16
    Cited by:  Papers (16)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB) |  | HTML iconHTML  

    This paper considers multiple-input multiple-output (MIMO) systems with bit-interleaved coded modulation (BICM). Two receiver structures are considered, one based on zero-forcing, the other on minimum mean square error (MMSE). An approximate log-likelihood (ALL) decoding approach is examined in each case, for PSK and QAM. The resulting receivers are significantly lower complexity compared to the maximum likelihood (ML) receiver. We expand on previous results which showed that for the ZF-ALL receiver the performance gap, compared to ML, reduces when either the number of receive antennas or the modulation order is increased. We demonstrate that the ALL metric with BICM counteracts any noise enhancement from the linear receivers. We also show that the linear BICM schemes outperform the corresponding BLAST approaches. View full abstract»

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  • Low complexity iterative receiver for linear precoded MIMO systems

    Publication Year: 2004 , Page(s): 17 - 21
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (502 KB) |  | HTML iconHTML  

    In a multiple input multiple output (MIMO) context, we present, in this paper, a space-time bit interleaved coded modulation (STBICM) system combined with a space-time spreader called linear precoding. We propose a practical low-complexity receiver structure performing iteratively space-time detection and channel decoding. The novelty lies in the linearity of the space-time detector which consists of an MMSE MIMO PSIC equalizer and a linear deprecoder. Spectral efficiency and diversity can easily be tuned while keeping a feasible receiver. In the case of independent flat Rayleigh fading, simulation results show that such a system exploits both spatial diversity and capacity provided by the multi-antenna system. View full abstract»

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  • MIMO capacity with channel state information at the transmitter

    Publication Year: 2004 , Page(s): 22 - 26
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (541 KB) |  | HTML iconHTML  

    This paper presents analytical expressions for the capacity of single-user multi-antenna channels, known instantaneously by both transmitter and receiver, at moderate and high signal-to-noise ratios. Fading channels with both uncorrelated and correlated antennas are encompassed. The characterization is conducted primarily in the limit of large numbers of antennas, with accompanying examples that illustrate the validity of the results for even small numbers thereof. In the absence of correlation, the capacity is also tightly bounded for fixed numbers of antennas with compact closed-form expressions. View full abstract»

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  • Multi-sensor frequency domain multiple access interference canceller for DS-CDMA systems

    Publication Year: 2004 , Page(s): 27 - 31
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (526 KB) |  | HTML iconHTML  

    Direct sequence code division multiple access (DS-CDMA) signals exhibit cyclostationary properties which imply a redundancy between frequency components separated by multiples of the symbol rate. In this paper a multiple access interference canceller (frequency shift canceller) that explores this property is presented. This linear frequency domain canceller operates on the spread signal in such way that the interference and noise at its output is minimized (minimum mean squared error criterion). The frequency shift canceller (FSC) performance was evaluated for a UMTS-TDD scenario and multi-sensor configurations, where the cases of diversity and beamforming were considered. All these configurations are evaluated concatenated with a parallel interference canceller (PIC-2D). The results are benchmarked against the performance of the conventional RAKE-2D detector, the conventional PIC-2D detector and single user scenario, and we observe considerable performance gains with the FSC especially for the diversity case and a performance close to the single user case when it was evaluated jointly with PIC-2D. View full abstract»

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  • Novel concatenated space-time multiuser detector based on recursive constrained CMA with modulus correction

    Publication Year: 2004 , Page(s): 32 - 36
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (679 KB) |  | HTML iconHTML  

    The recursive constrained constant modulus algorithm (R-CCMA) with modulus parameter correction has fast convergence rate and good steady-state performance, and is robust to ill-conditioned initialization of weight vector and modulus parameter. These distinctive properties make it very suitable for time-varying channel applications. This paper presents a novel concatenated space-time multiuser detector based on it for uplink reception in a DS-CDMA system with periodic spreading. It consists of two stages: the spatial filter bank based on block RLS despread respread directing algorithm (BRLS-DRDA) is the first, which extracts the desired signal of each delay path and suppresses interference via spatial domain filtering; the R-CCMA multiuser detector is the following stage whose task is to further suppress interference from other paths and other users with temporal domain processing. Simulations show that it has quite fast convergence rate and very good steady-state performance. View full abstract»

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  • The optimum received signal-power distribution for CDMA packet communication systems employing successive interference cancellation

    Publication Year: 2004 , Page(s): 37 - 41
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (929 KB) |  | HTML iconHTML  

    In CDMA packet communication systems employing the successive interference cancellation (SIC) scheme, the suppression of MAI depends on the received signal-power distribution, in addition to the cross-correlation characteristics of the spreading sequences and the number of transmitted packets. Some work has been done about discovering the received signal-power distribution which makes MAI be suppressed effectively. This distribution minimizes the averaged bit error rate (BER). However, in packet communication systems, it is important to the performance whether packets can be transmitted successfully or not. Even if the averaged BER is high, many packets can be correctly transmitted. It implies that the optimum distribution on averaged BER does not give the best performance of packet transmission. The received signal-power distribution which gives the best performance of packet transmission is derived. Such a distribution makes clear the limit of performance improvement using SIC. View full abstract»

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  • Cochannel interference cancellation for frequency hopped multiple access systems

    Publication Year: 2004 , Page(s): 42 - 46
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB) |  | HTML iconHTML  

    Based on an analysis of the cochannel interference (CCI) pattern of a frequency hopped multiple access signal, the paper proposes a new multiuser detection algorithm for canceling the CCI in frequency hopped multiple access systems. In the proposed scheme, the CCI is cancelled by first detecting the frequency hopping slot, and then classifying and regenerating the candidates of the interference pattern from the time-frequency matrix. Both theoretical analysis and computer simulation results show that, compared to the conventional detector and Mabuchi's detector, this new multiuser detector has lower complexity, better convergence stability, and is suitable for both additive white Gaussian noise (AWGN) channels and Rayleigh fading channels. View full abstract»

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  • FDE-RAKE: a PIC multiuser detector for CDMA downlink

    Publication Year: 2004 , Page(s): 47 - 50
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (493 KB) |  | HTML iconHTML  

    The paper introduces a two stage multiuser detector for CDMA downlink systems. Frequency domain equalization (FDE) is used at the first stage as a single-user detector. A RAKE receiver is then employed at the second stage, following a parallel interference cancellation (PIC) process. The performance of the FDE-RAKE detector is evaluated in a UTRA-TDD system, and compared with the linear multiuser detector. The FDE-RAKE demonstrates a slightly better performance than the linear multiuser detector, while retaining the simplicity of the employed algorithm. It also offers the important advantage that the detection quality of the first stage is significantly better than the detection of the RAKE receiver, which is usually used as the first processing stage in most CDMA multiuser detection strategies. Hence, the second stage of the FDE-RAKE detector can be optionally added if better detection is required. View full abstract»

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  • Minimum conditional probability of error detection for MC-CDMA

    Publication Year: 2004 , Page(s): 51 - 55
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (498 KB) |  | HTML iconHTML  

    Multi-carrier code division multiple access (MC-CDMA) is an attractive choice for high speed wireless communication as it mitigates the problem of intersymbol interference (ISI) and also exploits frequency diversity. The data stream in MC-CDMA is spread using a user specific spreading sequence in the frequency domain and every chip travels on a different sub-carrier. At the receiver, the different sub-carriers have to be combined properly to form the decision variable. Minimum mean square error (MMSE) detection is a popular choice for this, but as it tries to minimize the mean square error (MSE) and not the bit error rate (BER), the BER it attains is not optimum. We propose a minimum probability of error (MPOE) based linear multiuser detector, which tries to minimize the probability of error. A minimum conditional probability of error (MCPOE) detector is introduced for reducing the computational complexity of the MPOE detector. Theoretical and simulation results are presented for the MCPOE and MPOE detector and it can be seen that the MPOE detector outperforms the MMSE detector. View full abstract»

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  • Improved MC-CDMA reception employing two-dimensional decision-feedback pilot and data symbol correction

    Publication Year: 2004 , Page(s): 56 - 60
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (549 KB) |  | HTML iconHTML  

    An algorithm is presented that recovers, to a large degree, the performance degradation due to channel estimation and equalization errors in a multi-carrier code division multiple access (MC-CDMA) system. The algorithm uses the two-dimensional structure of the MC-CDMA frame to estimate the equalization error. It contains two steps that can be applied independently from each other. In the first step, the pilot symbols are corrected and channel estimation and equalization are redone for the received data symbol samples. In the second step, a possible remaining mismatch on the equalized data symbol samples is 're-equalized' and new symbol decisions on the 're-equalized' signal are made. It is shown that the algorithm is able to improve the performance in additive white Gaussian noise (AWGN) and fading channels with and without channel coding. On a frequency-selective fading channel and with standard Rcc=1/2 convolutional coding, a performance improvement of approximately 4.75 dB is possible at a BER of 10-6. View full abstract»

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  • Multicarrier spread spectrum: a coding perspective

    Publication Year: 2004 , Page(s): 61 - 66
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (665 KB) |  | HTML iconHTML  

    The paper reveals the interrelation between multicarrier spread spectrum (MC-SS) transmission and multilevel coding (MLC). It is shown that MC-SS systems can be interpreted as a multilevel code with repetition codes in the levels. The paper is intended to provide new insights into both MC-SS systems and MLC. For both schemes, a lot of theory has been provided by numerous publications and particular parts of the existing theory for one scheme can be applied to the other. View full abstract»

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  • Performance analysis of MC-CDMA system with and without guard interval in two-path channel

    Publication Year: 2004 , Page(s): 67 - 71
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (855 KB) |  | HTML iconHTML  

    We analyze the performance of the multi-carrier CDMA (MC-CDMA) system with and without guard interval (GI) in a two-path channel. From the results, we show that the BER performance in the two cases is almost the same. This implies the removal of GI for the MC-CDMA system. View full abstract»

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  • On the design of spectrally overlaid multiple-symbol-rate multicarrier CDMA systems supporting multirate services

    Publication Year: 2004 , Page(s): 72 - 76
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (823 KB) |  | HTML iconHTML  

    Two types of spectrally overlaid multiple-symbol-rate (MSR) asynchronous multicarrier code division multiple access (MC-CDMA) systems are proposed. One type of systems has constant spreading gain (CSG) and the other has variable spreading gain (VSG) for different services; both systems have different symbol rates at each subcarrier for different services. Two possible configurations of CSG systems are also proposed. An adaptive power control is proposed to maintain the link quality and improve the system capacity. The multiple access interference, and hence system capacity, for each type of MSR MC-CDMA system is investigated. From the numerical results obtained, it can be concluded that the MSR MC-CDMA systems with VSG and with CSG configuration 2 can both obtain much steadier performance and system capacity than the system with CSG configuration 1. View full abstract»

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  • An optimal pilot embedding scheme for channel identification and source recovery

    Publication Year: 2004 , Page(s): 77 - 81
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (523 KB) |  | HTML iconHTML  

    An optimal pilot embedding scheme is proposed for multipath channel identification. The scheme adds the columns of a Hadamard matrix to the transmitted signal to help estimate the channel. At the receiver, the channel is estimated as a function of the mean of the received blocks. A power allocation scheme is derived for approximately determining the optimal amount of power to allocate to the information symbols and the added pilot symbols. View full abstract»

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  • Theoretical boundaries for combined information estimation and non data-aided channel estimation in UWB

    Publication Year: 2004 , Page(s): 82 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB) |  | HTML iconHTML  

    One of the main advantages of ultra wide band (UWB) systems is the extreme time resolution due to the huge bandwidth of several GHz. This allows the distinction between many different propagation paths in multipath environments and thus transmits with very low power. In order to benefit from the advantages of UWB, accurate estimations of the current channel realization are necessary. We derive theoretical boundaries for pulse transmission for the expected BER, the accuracy of the channel estimation and the interaction between these two problems. As an example, the popular time-hopping pulse-position-modulation UWB (TH-PPM UWB) is used to show the trade-off between information and channel estimation. View full abstract»

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  • A multipath mobile channel model for microcell environment

    Publication Year: 2004 , Page(s): 87 - 91
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (549 KB) |  | HTML iconHTML  

    We present a geometric multipath propagation model for a microcell mobile environment. The model provides the statistics for the direction-of-arrival (DOA) of multipath components; also it provides the multipath power delay profiles (PDP), which are used to evaluate the bit error rate (BER) and the signal to interference ratio (SIR) for the direct-sequence code division multiple access (DS-CDMA). The probability density function (pdf) for the DOA under the proposed model is compared with experimental results for indoor multipath channel. The experimental results agree with the proposed model's simulation results. View full abstract»

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  • Decoupled maximum likelihood multiuser channel estimation for asynchronous DS-CDMA system

    Publication Year: 2004 , Page(s): 92 - 96
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (743 KB) |  | HTML iconHTML  

    A decoupled maximum likelihood (DEML) channel estimation scheme using recursive matrix computation is proposed for asynchronous code-division multiple access (CDMA) communication systems. The transmission medium is characterized by the presence of multipath components and the parameters of interest are the delays and complex gains of the propagation paths. The DEML estimation is obtained using a training sequence. Followed by DEML estimation, a recursive algorithm is used to find the estimator so as to spread the computational time over each processing window. Lastly, the proposed recursive technique is extended to track a moderate time-varying fading channel using decision feedback. The performance of the derived algorithm is benchmarked against perfect channel knowledge on one hand and DEML estimator without decision feedback on the other hand in terms of bit-error-rate. View full abstract»

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  • Information theoretic approach to finite state Markov modelling of time varying channels

    Publication Year: 2004 , Page(s): 97 - 101
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (517 KB) |  | HTML iconHTML  

    The time varying binary symmetric channel (TVBSC) model is presented in this paper. The TVBSC is developed to be the simplest model which captures the most important non-trivial attributes of general time-varying channels. An information theoretic analysis verifies that this model holds the essential elements of the behavior of time varying channels. The influence of the channel uncertainty is captured serving to significantly differentiate the TVBSC model from other two-state Markov models, especially from the the Gilbert-Elliot model. This elementary form of time varying channel model has an information capacity that is calculated using several methods. Given this capacity, the most efficient way for the time varying communications channel response estimation can be considered. Finally, accurate approximations for the TVBSC information capacity are found, providing better inside into the capacity analysis of time varying communication channels. View full abstract»

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