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Communications Letters, IEEE

Issue 9 • Date Sept. 2001

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Displaying Results 1 - 10 of 10
  • Near-optimal multiuser detection in synchronous CDMA using probabilistic data association

    Publication Year: 2001 , Page(s): 361 - 363
    Cited by:  Papers (113)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (67 KB) |  | HTML iconHTML  

    A probabilistic data association (PDA) method is proposed in this letter for multiuser detection over synchronous code-division multiple-access (CDMA) communication channels. PDA models the undecided user signals as binary random variables. By approximating the inter-user interference (IUI) as Gaussian noise with an appropriately elevated covariance matrix, the probability associated with each user signal is iteratively updated. Computer simulations show that the system usually converges within three to four iterations, and the resulting probability of error is very close to that of the optimal maximum-likelihood (ML) detector. Further modifications are also presented to significantly reduce the computational cost. View full abstract»

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  • On the relation between V-BLAST and the GDFE

    Publication Year: 2001 , Page(s): 364 - 366
    Cited by:  Papers (90)  |  Patents (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (74 KB) |  | HTML iconHTML  

    This letter shows that the receiver processing of the Vertical Bell Labs Layered Space-Time (V-BLAST) architecture may he viewed as a generalized decision feedback equalizer (GDFE) as applied to a multiple-input-multiple-output (MIMO) channel. It is proven that, depending on the criterion chosen to reduce the interference, the receiver operations of the V-BLAST system are fundamentally equivalent to either a zero-forcing (ZF) or a minimum-mean-square-error (MMSE) GDFE. View full abstract»

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  • A "better than" Nyquist pulse

    Publication Year: 2001 , Page(s): 367 - 368
    Cited by:  Papers (97)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (92 KB) |  | HTML iconHTML  

    A novel ISI-free pulse is presented that has smaller maximum distortion, a more open receiver eye, and a smaller probability of error in the presence of symbol timing error than the Nyquist pulse for the same excess bandwidth. View full abstract»

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  • Channel capacity of MIMO architecture using the exponential correlation matrix

    Publication Year: 2001 , Page(s): 369 - 371
    Cited by:  Papers (221)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (58 KB) |  | HTML iconHTML  

    Multiple-input multiple output (MIMO) communication architecture has recently emerged as a new paradigm for wireless communications in rich multipath environment, which has spectral efficiencies far beyond those offered by conventional techniques. The channel capacity of the MIMO architecture in independent Rayleigh channels scales linearly as the number of antennas. However, the correlation of a real-world wireless channel may result in a substantial degradation of the MIMO architecture performance. In this letter, we investigate the MIMO channel capacity in correlated channels using the exponential correlation matrix model. We prove that, for this model, an increase in correlation is equivalent to a decrease in signal-to-noise ratio (SNR). For example, r=0.7 is the same as 3-dB decrease in SNR. View full abstract»

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  • Innovative pulse shaping for high-performance wireless TDMA

    Publication Year: 2001 , Page(s): 372 - 374
    Cited by:  Papers (11)  |  Patents (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (62 KB) |  | HTML iconHTML  

    This letter introduces a novel pulse shaping scheme that enables receivers to demonstrate high performance in wireless fading environments. Called carrier interferometry pulse shaping, pulses are created by the superposition of N carriers. At the receiver, low probability-of-error performance is achieved by breaking the pulse into its frequency components and optimally recombining to create frequency diversity benefits. When implemented in a wireless TDMA system, simulations indicate 5-8-dB improvement at probability-of-error of 10/sup -2/ over traditional Gaussian pulse shaping with decision feedback equalization (DFE(6,4)) in hilly terrain (HT) and typical urban (TU) channels. View full abstract»

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  • Joint decoding and carrier phase recovery algorithm for turbo codes

    Publication Year: 2001 , Page(s): 375 - 377
    Cited by:  Papers (27)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (130 KB) |  | HTML iconHTML  

    In this letter, we investigate the sensitivity of the iterative maximum a posteriori probability (MAP) decoder to carrier phase offsets and propose simple carrier phase recovery algorithms operating within the iterative MAP decoding iterations. The algorithms exploit the information contained in the extrinsic values generated within the iterative MAP decoder to perform carrier recovery, thus requiring low hardware complexity. View full abstract»

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  • Integrating voice and data applications in T/CDMA architectures

    Publication Year: 2001 , Page(s): 378 - 380
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (83 KB) |  | HTML iconHTML  

    This letter analyzes the behavior of two time-code division architectures serving voice and data applications on the uplink of a cellular radio system. Both solutions attribute speech users one code over a timeslot, whereas data users are granted several codes over the same timeslot or a single code over several time slots. Call admission control dynamically attributes resources if specified levels of transmission quality are met. The blocking probability of the two classes of users is determined, demonstrating that the multicode T/CDMA approach performs better than the multislot solution and than a pure CDMA system. View full abstract»

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  • Optimal Farrow coefficients for symbol timing recovery

    Publication Year: 2001 , Page(s): 381 - 383
    Cited by:  Papers (12)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (70 KB) |  | HTML iconHTML  

    The Farrow structure provides an efficient way to implement interpolation filters. Such filters are often required in digital modems to allow symbol timing recovery. A method for generating Farrow filter coefficients that minimize the mean square error (MSE) at the symbol decision instants is presented. Minimizing the MSE at the symbol decision instants is nearly equivalent to minimizing the symbol error rate (SER) but is more mathematically convenient. The MSE at times other than the symbol decision instants does not affect the SER and is not considered in the optimization. Example coefficients are tabulated and performance is illustrated using SER results generated by computer simulation. View full abstract»

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  • Operation and cost optimization of a distributed servers architecture for on-demand video services

    Publication Year: 2001 , Page(s): 384 - 386
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (71 KB) |  | HTML iconHTML  

    Distributed servers architecture offers storage and streaming scalabilities for video services. In this letter, we propose and analyze an on-demand scheme in which the local servers store the beginning portion (i.e., the "prefix") of videos and deliver it by means of unicast streams to the clients. The clients are able to merge onto on-going multicast streams delivered from the repository by means of their set-top buffers. Given a certain limited repository (and thereof multicast) bandwidth, we investigate how the total cost of the local servers can be minimized. We show that if the local storage is the main cost, the size of the prefixes is likely to increase with the video popularity. On the other hand, if the server cost mainly comes from streaming capacity, the size of the prefixes is likely to decrease asymptotically with the video popularity. View full abstract»

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  • Arrival rate estimation algorithm for single group slotted ALOHA systems

    Publication Year: 2001 , Page(s): 387 - 389
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (81 KB) |  | HTML iconHTML  

    In this letter, a new recursive tracking algorithm is presented that is capable of estimating the real arrival rate, /spl lambda//sub real/, to the system. The estimated value of the arrival rate, /spl lambda//sub estimated/, is used to dynamically adjust the control parameters of the system, hence ensuring that the operating point of the system is pushed toward the required settling point, whatever the real arrival rate to the system. This algorithm utilizes system information through the feedback channel in order to dynamically adjust the estimated value of the arrival rate and hence update the values of the control parameters. View full abstract»

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IEEE Communications Letters  is aimed at satisfying the need for rapid dissemination of information, offering a vehicle for authors to expose their results to be used in future developments. This ensures early recognition of work. 

 

 

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Editor-in-Chief
George K. Karagiannidis
Aristotle University of Thessaloniki
Greece