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Communications Letters, IEEE

Issue 12 • Date Dec. 2003

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Displaying Results 1 - 14 of 14
  • Source-adaptive power allocation for digital modulation

    Page(s): 569 - 571
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB) |  | HTML iconHTML  

    A novel joint source channel-coding technique called source-adaptive power allocation is introduced for the transmission of continuous-amplitude waveform source samples over a noisy channel. Starting from a binary or quaternary digital modulation scheme we apply a power control, which depends on the unquantized source samples, to the modulation signal points before they are transmitted over the channel. The resulting system shows strongly superior performance compared with conventional schemes. View full abstract»

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  • Exact bit error rate analysis of TH-PPM UWB systems in the presence of multiple-access interference

    Page(s): 572 - 574
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (294 KB) |  | HTML iconHTML  

    A new method is proposed for precisely calculating the bit error probability of a time-hopping binary pulse position modulation ultra-wideband system with multiple access interference. The analytical expression is validated by simulation and used to assess the inaccuracy of the Gaussian approximation. View full abstract»

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  • Peak-to-average power ratio in MIMO-OFDM systems using selective mapping

    Page(s): 575 - 577
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (293 KB) |  | HTML iconHTML  

    This letter evaluates the peak-to-average power ratio (PAR) performance in a space-time block coded (STBC) multi-input multi-output orthogonal frequency-division multiplexing (MIMO-OFDM) system using the selective mapping (SLM) approach. The investigated SLM-based MIMO-OFDM system selects the transmitted sequence with the lowest average PAR over all transmit antennas and retrieves the side information very accurately at the expense of only 0.5-dB degradation of the PAR, which can improve the overall detection performance of the MIMO-OFDM system with erroneous side information, compared to the individual SLM approach. View full abstract»

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  • Universal stability results for low rate adversaries in packet switched networks

    Page(s): 578 - 580
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (235 KB) |  | HTML iconHTML  

    In this work, we consider a generalized version of the adversarial model and study the universal stability (stability in any network) of scheduling policies under low load rates. We show that any work-conserving policy is universally stable at any load rate r<(1/d), where d is the largest number of links crossed by any packet. We also show that system-wide time priority policies are universally stable at any load rate r<(1/(d-1)). View full abstract»

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  • Approximation of SNR degradation due to carrier frequency offset for OFDM in shadowed multipath channels

    Page(s): 581 - 583
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    We derive an approximate expression for signal-to-noise ratio (SNR) degradation of orthogonal frequency division multiplexing due to carrier frequency offset over a shadowed multipath channel, to explicitly show the effects of system and channel parameters on the degradation of the received SNR. The results show that, for small frequency offset, the SNR degradation is proportional to the square of the frequency offset and the square of the number of subcarriers. It is also shown that, if E/sub s//N/sub 0/ is reasonably large, the SNR degradation becomes insensitive to E/sub s//N/sub 0/, which is contrary to the case of the additive white Gaussian noise channel. View full abstract»

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  • Improved neighbor detection algorithm for AODV routing protocol

    Page(s): 584 - 586
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    In this letter, a problem related to the behavior of WLAN 802.11 b network cards when working in the ad hoc mode is described. This behavior was noticed during experimental evaluation of an ad hoc network that was using the AODV (ad hoc On-demand Distance Vector) routing protocol. The observed problem affects the neighbor detection algorithm of the AODV routing protocol and has a deteriorating impact on performance of ad hoc networks that use this protocol. An improvement of the neighbor detection algorithm based on the differentiation of good and bad neighbors using signal to noise ratio (SNR) value is proposed, described and experimentally verified. View full abstract»

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  • Performance evaluation of mobile wireless communication systems with link adaptation

    Page(s): 587 - 589
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB) |  | HTML iconHTML  

    The performance of key quality-of-service metrics for mobile cellular systems with link adaptation is evaluated by means of a teletraffic analysis. To our knowledge, no similar analysis considering link adaptation exists in the literature. In particular, novel mathematical expressions for inter-cell handoff call arrival rate, intracell handoff failure, and forced termination probabilities are derived. View full abstract»

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  • A new full-rate full-diversity orthogonal space-time block coding scheme

    Page(s): 590 - 592
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (270 KB) |  | HTML iconHTML  

    In this work, we present a new space-time orthogonal coding scheme with full-rate and full-diversity. The proposed space-time coding scheme can be used on quaternary phase-shift keyed (QPSK) transceiver systems with four transmit antennas and any number of receivers. An additional feature is that the coded signals transmitted through all four transmit antennas do not experience any constellation expansion. The performance of the proposed coding scheme is studied in comparison with that of 1/2-rate full-diversity orthogonal space-time code, quasi-orthogonal code, as well as constellation-rotated quasi-orthogonal code. Our study shows that the proposed coding scheme offers full rate and outperforms the 1/2-rate orthogonal codes as well as full-rate quasi-orthogonal codes when the signal-to-noise increases. Compared to the constellation-rotated quasi-orthogonal codes (the improved QO scheme), the newly proposed code has the advantage of not expanding the signal constellation at each transmit antenna. The performance of the newly proposed code is comparable to that of the improved QO scheme. View full abstract»

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  • Optimization of symbol mappings for bit-interleaved coded Modulation with iterative decoding

    Page(s): 593 - 595
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB) |  | HTML iconHTML  

    We investigate bit-interleaved coded modulation with iterative decoding (BICM-ID) for bandwidth efficient transmission, where the bit error rate is reduced through iterations between a multilevel demapper and a simple channel decoder. In order to achieve a significant turbo-gain, the assignment strategy of the binary indices to signal points is crucial. We address the problem of finding the most suitable index assignments to arbitrary, high order signal constellations. A new method based on the binary switching algorithm is proposed that finds optimized mappings outperforming previously known ones. View full abstract»

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  • Robust video transmission over error-prone channels via error correcting arithmetic codes

    Page(s): 596 - 598
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (278 KB) |  | HTML iconHTML  

    We propose arithmetic codes (ACs) with a forbidden symbol as a joint entropy coding and error protection tool for robust video transmission over error-prone channels. In particular, we introduce a MAP decoder of ACs, and apply it to the transmission of 3-D SPIHT coded video and RTP/UDP/IP H.264 video with data partitioning. Experimental results show that the proposed system exhibits several advantages with respect to other schemes, and outperforms rate-compatible punctured convolutional (RCPC) codes in the applications considered. View full abstract»

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  • Rearrangeability of multicast Clos networks with middle-stage fan-out

    Page(s): 599 - 600
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (197 KB) |  | HTML iconHTML  

    The sufficient and necessary conditions under which a three-stage Clos network is rearrangeable for multicast connections are given. It is assumed that only switches of the middle stage have the fan-out property. Such an assumption is valid for some practical switching systems, e.g., high-speed crossconnects. View full abstract»

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  • Network management agent allocation scheme in mesh networks

    Page(s): 601 - 603
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (230 KB) |  | HTML iconHTML  

    In this letter, we propose a scheme for constructing a reliable alarm detection structure in the communication networks. We investigate how to allocate a minimal set of management agents and still cover all alarms in mesh networks under the assumption that alarms are delivered along provisioned paths. We also consider the probabilistic nature of alarm loss and propose an efficient scheme for allocating a minimal set of agents while keeping the overall alarm loss probability below a threshold. View full abstract»

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  • List of reviewers

    Page(s): 604 - 608
    Save to Project icon | Request Permissions | PDF file iconPDF (152 KB)  
    Freely Available from IEEE
  • 2003 Index IEEE Communications Letters Vol. 7

    Page(s): 609 - 633
    Save to Project icon | Request Permissions | PDF file iconPDF (355 KB)  
    Freely Available from IEEE

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