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Communications, IEEE Transactions on

Issue 12 • Date Dec. 2005

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Displaying Results 1 - 25 of 35
  • Table of contents

    Page(s): c1 - c4
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    Freely Available from IEEE
  • IEEE Transactions on Communications publication information

    Page(s): c2
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  • On maximum-length linear congruential-sequences-based low-density parity-check codes

    Page(s): 1977 - 1980
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    This letter extends a low-density parity-check code construction using maximum-length linear congruential sequences by Prabhakar and Narayanan. The corresponding bipartite graphs of their construction were guaranteed to have a girth larger than four by a sufficient condition. However, their sufficient condition was limited to regular codes and data-node degree equal to three. The extension in this letter allows arbitrary data-node degrees and is applicable to irregular codes. Further, simpler sufficient conditions are derived and larger girths are addressed. View full abstract»

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  • Multiple-symbol differential sphere decoding

    Page(s): 1981 - 1985
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB) |  | HTML iconHTML  

    In multiple-symbol differential detection (MSDD) for power-efficient transmission over Rayleigh fading channels without channel state information, blocks of N received symbols are jointly processed to decide on N-1 data symbols. The search space for the maximum-likelihood (ML) estimate is therefore (complex) (N-1)-dimensional, and maximum-likelihood MSDD (ML-MSDD) quickly becomes computationally intractable as N grows. Mackenthun's low-complexity MSDD algorithm finds the ML estimate only for Rayleigh fading channels that are time-invariant over an N symbol period. For the general time-varying fading case, however, low-complexity ML-MSDD is an unsolved problem. In this letter, we solve this problem by applying sphere decoding (SD) to ML-MSDD for time-varying Rayleigh fading channels. The resulting technique is referred to as multiple-symbol differential sphere decoding (MSDSD). View full abstract»

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  • Rate-one space-time block codes with full diversity

    Page(s): 1986 - 1990
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    Orthogonal space-time block codes provide full diversity, and maximum-likelihood (ML) decoding for orthogonal codes can be realized on a symbol-by-symbol basis. It has been shown that rate-one complex orthogonal codes do not exist for systems with more than two transmit antennas. For a general system with N transmit and M receive antennas, it is very desirable to design rate-one complex codes with full diversity. In this letter, we provide a systematic method of designing rate-one codes (real or complex) for a general multiple-input multiple-output system. Full diversity of these codes is then achieved by constellation rotation. A generalized, reduced-complexity decoding method for rate-one codes is also provided. View full abstract»

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  • Joint source-channel coding using combined TCQ/CPM: iterative decoding

    Page(s): 1991 - 1995
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    An iterative decoding approach to joint source and channel coding (JSCC) using combined trellis-coded quantization (TCQ) and continuous phase modulation (CPM) is proposed. The channel is assumed to be the additive white Gaussian noise channel. This iterative procedure exploits the structure of the TCQ encoder and the continuous phase modulator. The performance in terms of the signal-to-distortion ratio (SDR) is compared with that of a combined TCQ/trellis-coded modulation (TCM) system. It is shown that the combined TCQ/CPM systems are both power- and bandwidth-efficient, compared with the combined TCQ/TCM system. For source encoding rate R=2 b/sample, it is observed that the combined TCQ/CPM systems with iterative decoding working at symbol level converge faster than the systems working at bit level. The novelty of this work is the use of a soft decoder and an iterative decoding algorithm for TCQ-based JSCC systems. The combined TCQ/CPM with iterative decoding is considered for the first time. View full abstract»

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  • A hybrid ARQ protocol using integrated channel equalization

    Page(s): 1996 - 2001
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB) |  | HTML iconHTML  

    In this letter, a new hybrid automatic repeat request (ARQ) approach is presented to enhance receiver performance for communication systems employing forward error-correction codes in frequency-selective fading environments. This new approach involves a simple modification to the traditional turbo equalizer by combining multiple ARQ transmissions via integrated channel equalization. This modification leads to better computational efficiency, better exploitation of channel diversity, better channel-estimation ability, and improved performance (frame-error rates) when concatenated with an outer code. These improvements are verified through evaluations of extrinsic information transfer charts and ARQ simulations when compared with iterative combining of multiple transmissions. View full abstract»

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  • Another look at the performance of MRC schemes in Nakagami-m fading channels with arbitrary parameters

    Page(s): 2002 - 2005
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    In this letter, we take a close look at the performance of maximal ratio combining (MRC) schemes operating in a flat-Nakagami-m fading environment with arbitrary fading parameters. We derive an expression for the probability density function (pdf) of the output signal-to-noise ratio (SNR) by expressing the moment generating function of the output SNR in the form of multiple Barnes-type contour integrals. By evaluating the inverse transform and converting the multiple contour integrals into infinite series, we are able to derive an expression for the pdf of the output SNR when the Nakagami fading parameters along the diversity branches take on real and arbitrary values. Consequently, the average bit-error rate can now be expressed in terms of Lauricella's multivariate hypergeometric function, which can be easily evaluated numerically. Special cases of the main results reduce to known results in the literature. The results, which apply to independent as well as correlated diversity branches, will be useful for predicting the system performances when the Nakagami fading parameters are real and arbitrary. View full abstract»

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  • Analytical performance analysis of the linear multistage partial PIC receiver for DS-CDMA systems

    Page(s): 2006 - 2010
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    In this letter, we derive a recursive expression for the decision statistic of a linear multistage partial parallel interference cancellation (PIC) receiver for direct-sequence code-division multiple-access systems that allow us to present two closed-form expressions (exact and approximate) for the bit-error probability of this receiver. The bit-error rate is computed in terms of the number of PIC stages, set of cancellation parameters, crosscorrelation between the users' codes, amplitude of the users' signals, and noise power. View full abstract»

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  • Minimal PAM decompositions of CPM signals with separable phase

    Page(s): 2011 - 2014
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    This letter proposes a new pulse amplitude modulation decomposition of continuous phase modulation (CPM) signals under the constraint of phase response separability. The separability condition is met by a broad class of CPM signals, including full-response signals. We show that the proposed decomposition has minimal cardinality of Nc=L(M-1), where M is the alphabet size and L is the CPM memory length. The cardinality increases linearly with L, while previous proposed decompositions have cardinalities ML-ML-1, which grow exponentially with L. View full abstract»

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  • A search strategy for ultra-wideband signal acquisition

    Page(s): 2015 - 2019
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    The ultra-wideband (UWB) channel is characterized by the presence of dense multipath and robustness to multipath fading. By taking system performance subsequent to acquisition into account, it was shown recently that there are multiple phases (called the hit set) where a receiver lock can be considered as successful acquisition. In this case, the serial search may no longer be the optimal choice for the sequential search strategy in the acquisition system. In this letter, we consider the problem of finding better search strategies in the set of all search strategies which are permutations of the search space. The large size of the search space and the absence of any exploitable structure make the problem of finding the permutation search strategy which minimizes the mean detection time prohibitively complex. However, if we take the first-order approximation that the probabilities of detection of all the hit-set phases are equal, then there exists a permutation search strategy which minimizes the mean detection time. Since the actual probabilities of detection are not equal, this search strategy, although not optimal, serves as a useful heuristic solution to an otherwise intractable problem. Furthermore, we see that this search strategy has a simple Jump-by-H structure, and improves the mean detection time by a significant amount compared with the serial search. View full abstract»

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  • Necessary and sufficient conditions for rearrangeable Logd(N,m,p)

    Page(s): 2020 - 2023
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    We extend previous results on sufficient conditions for rearrangeable Log2(N,m,p) networks to Logd(N,m,p) networks. We show that the original argument using path-intersecting graphs cannot be extended to d>2, and we give a new argument. Further, we show our sufficient conditions are also necessary. View full abstract»

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  • Differential space-frequency modulation via smooth logical channel for broadband wireless communications

    Page(s): 2024 - 2028
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB) |  | HTML iconHTML  

    In this letter, a differential space-frequency modulation (DSFM) scheme is proposed for multiple input multiple-output (MIMO)-orthogonal frequency-division multiplexing (OFDM) systems in broadband wireless communications. We assume that the fading channels keep constant only within each OFDM block, and may change independently from one OFDM block to another. The differential schemes proposed for MIMO-OFDM systems in the literature cannot successfully decode with such a rapidly fading channel, since the successful decoding of the previously existing schemes relies on the assumption that the fading channel keeps constant within a period of several OFDM blocks, and it changes slowly from a period of several OFDM blocks to another. In our proposed DSFM scheme, the transmitted signals are differentially encoded in the frequency domain within each OFDM block. Thus, the differential decoding can be performed over subcarriers within each single OFDM block. Furthermore, if a statistical channel power-delay profile (PDP) is known at the transmitter, we propose to create a smooth logical channel to improve the performance of the DSFM scheme. We obtain the smooth logical channel by sorting the channel frequency responses over subcarriers from a statistical point of view. If the logical channel is not smooth enough, we further consider a pruning process in which we use only the "good" part of the channel and get rid of the "bad" part of the channel. Simulation results show that the proposed DSFM scheme over a smooth logical channel (with pruning, if necessary) performs well for various channel PDPs. View full abstract»

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  • Balanced capacity of wireline multiuser channels

    Page(s): 2029 - 2042
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB) |  | HTML iconHTML  

    This paper analyzes the multiuser capacity of Gaussian frequency-selective wireline multiaccess channels. Both the uplink (multiple-access channel) and downlink (broadcast channel) capacity regions are considered. The concept of balanced capacity is introduced to characterize the multiuser channel performance. Algorithms for the computation of the balanced multiuser capacity (and the associated power allocations) are proposed for an arbitrary number of users. The optimal power allocation in a K-user memoryless Gaussian channel is analyzed in detail, and an extension to intersymbol interference channels is given with various kinds of power constraints. Results are provided for a wireline access network with 20 users. View full abstract»

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  • Multivariate block polar quantization

    Page(s): 2043 - 2053
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    We introduce multivariate block polar quantization (MBPQ). MBPQ minimizes the weighted squared-error distortion for a set of complex variables representing one block of a signal under a resolution constraint for the entire block. MBPQ performs below the lower bound for classical bivariate quantization, both for Gaussian complex variables and for complex variables found from sinusoidal analysis of audio data. Still, it is of similar complexity as traditional polar quantizers. In the case of audio data, we found a performance gain of about 2.5 dB over the best performing conventional resolution-constrained polar quantization (an extension of unrestricted polar quantization). View full abstract»

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  • Low-complexity iterative joint source-channel decoding for variable-length encoded Markov sources

    Page(s): 2054 - 2064
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB) |  | HTML iconHTML  

    In this paper, we present a novel packetized bit-level decoding algorithm for variable-length encoded Markov sources, which calculates reliability information for the decoded bits in the form of a posteriori probabilities (APPs). An interesting feature of the proposed approach is that symbol-based source statistics in the form of the transition probabilities of the Markov source are exploited as a priori information on a bit-level trellis. This method is especially well-suited for long input blocks, since in contrast to other symbol-based APP decoding approaches, the number of trellis states does not depend on the packet length. When additionally the variable-length encoded source data is protected by channel codes, an iterative source-channel decoding scheme can be obtained in the same way as for serially concatenated codes. Furthermore, based on an analysis of the iterative decoder via extrinsic information transfer charts, it can be shown that by using reversible variable-length codes with a free distance of two, in combination with rate-1 channel codes and residual source redundancy, a reliable transmission is possible even for highly corrupted channels. This justifies a new source-channel encoding technique where explicit redundancy for error protection is only added in the source encoder. View full abstract»

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  • PAM decomposition of M-ary multi-h CPM

    Page(s): 2065 - 2075
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB) |  | HTML iconHTML  

    It is known that any multilevel continuous phase-modulated (CPM) signal with a single modulation index can be exactly represented by a sum of pulse-amplitude modulated (PAM) waveforms. In this paper, we show how multi-h CPM signals can also be represented in this manner. The decomposition is presented in general terms as a function of the alphabet size, modulation indexes, and phase pulse of the CPM scheme. The number of pulses required to exactly construct the signal is shown to increase over that previously given for single-h schemes; this increase is in proportion to the number of modulation indexes. We propose an approximation which significantly reduces the number of signal pulses and which minimizes the mean-squared error for an arbitrary set of modulation indexes. We show that this approximation can have two objectives: 1) to reduce the number of pulses in the same manner as has been proposed for single-h schemes; and/or 2) to reduce the number of multi-h pulses; we also show the conditions where this latter objective is most practical. We compare this minimum mean-squared error approximation with another method which was recently proposed for CPM. We also give numerical results on detection performance which demonstrate the practicality of the proposed approximation. View full abstract»

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  • A new class of iterative equalizers for space-time BICM over MIMO block fading multipath AWGN channel

    Page(s): 2076 - 2091
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (984 KB) |  | HTML iconHTML  

    This paper addresses the issue of advanced equalization methods for space-time communications over multiple-input multiple-output block fading channel with intersymbol interference. Instead of resorting to conventional multiuser detection techniques (based on the straightforward analogy between antennas and users), we adopt a different point of view, and separate time equalization from space equalization, thus introducing a higher degree of freedom in the overall space-time equalizer design. Time-domain equalization relies on minimum mean-square error criterion and operates on multidimensional modulation symbols, whose individual components can be detected in accordance with another criterion. In particular, when the optimum maximum a posteriori criterion is chosen, substantial performance gains over conventional space-time turbo equalization have been observed for different transmission scenarios, at the price of an increased, albeit manageable, computational complexity. View full abstract»

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  • Infinite series representations of the trivariate and quadrivariate Rayleigh distribution and their applications

    Page(s): 2092 - 2101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB) |  | HTML iconHTML  

    Few theoretical results are known about the joint distribution of three or more arbitrarily correlated Rayleigh random variables (RVs). Consequently, theoretical performance results are unknown for three- and four-branch equal gain combining (EGC), selection combining (SC), and generalized SC (GSC) in correlated Rayleigh fading. This paper redresses this gap by deriving new infinite series representations for the joint probability density function (pdf) and the joint cumulative distribution function (cdf) of three and four correlated Rayleigh RVs. Bounds on the error resulting from truncating the infinite series are derived. A classical approach, due to Miller, is used to derive our results. Unfortunately, Miller's approach cannot be extended to more than four variates and, in fact, the quadrivariate case considered in this paper appears to be the most general result possible. For brevity, we treat only a limited number of applications in this paper. The new pdf and cdf expressions are used to derive the outage probability of three-branch SC, the moments of the EGC output signal-to-noise ratio (SNR), and the moment generating function of the GSC(2,3) output SNR in arbitrarily correlated Rayleigh fading. A novel application of Bonferroni's inequalities allows new outage bounds for multibranch SC in arbitrarily correlated Rayleigh channels. View full abstract»

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  • Turbo equalization via constrained-delay APP estimation with decision feedback

    Page(s): 2102 - 2113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB) |  | HTML iconHTML  

    We consider turbo equalization for intersymbol interference (ISI) channels, wherein soft symbol decisions generated by the channel detector are iteratively exchanged with the outer error-correction decoder based on the turbo principle. Our work is based on low-complexity suboptimal soft-output channel detection using a constrained-delay (CD) a posteriori probability (APP) algorithm. Central to the proposed idea is the incorporation of effective decision-feedback schemes, which significantly reduce complexity while providing immunity against error propagation that typically plagues decision-feedback schemes. We observe that the effect of decision feedback is quite different on turbo equalization versus traditional, hard-decision-generating and noniterative equalization. In particular, we demonstrate that when the feedback scheme applied is inadequate for the given equalizer parameters and ISI condition, the extrinsic information generated by the equalizer becomes distinctly non-Gaussian, and the quality of soft information, as monitored by the trajectory of mutual information, fails to improve in the iterative process. We identify parameters of feedback-based CD-APP schemes that offer favorable complexity/performance tradeoffs, compared with existing turbo-equalization techniques. View full abstract»

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  • Bound-intersection detection for multiple-symbol differential unitary space-time modulation

    Page(s): 2114 - 2123
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB) |  | HTML iconHTML  

    This paper considers multiple-symbol differential detection (MSD) of differential unitary space-time modulation (DUSTM) over multiple-antenna systems. We derive a novel exact maximum-likelihood (ML) detector, called the bound-intersection detector (BID), using the extended Euclidean algorithm for single-symbol detection of diagonal constellations. While the ML search complexity is exponential in the number of transmit antennas and the data rate, our algorithm, particularly in high signal-to-noise ratio, achieves significant computational savings over the naive ML algorithm and the previous detector based on lattice reduction. We also develop four BID variants for MSD. The first two are ML and use branch-and-bound, the third one is suboptimal, which first uses BID to generate a candidate subset and then exhaustively searches over the reduced space, and the last one generalizes decision-feedback differential detection. Simulation results show that the BID and its MSD variants perform nearly ML, but do so with significantly reduced complexity. View full abstract»

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  • Improvement of CSO/CTB performances employing up-converted and polarization modulation techniques

    Page(s): 2124 - 2128
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    A two-wavelength wavelength-division multiplexing (WDM) community antenna television (CATV) transport system that employed up-converted and polarization modulation techniques to reduce the composite second-order (CSO) distortion and optical nonlinearities is proposed and demonstrated. In contrast to a two-wavelength WDM CATV transport system using the intensity modulation technique, good performances of CSO and composite triple beat were obtained, accompanied by acceptable carrier-to-noise ratio value in our proposed system over a 100-km single-mode fiber transmission. View full abstract»

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  • Low-complexity block double-differential design for OFDM with carrier frequency offset

    Page(s): 2129 - 2138
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB) |  | HTML iconHTML  

    Carrier frequency offset (CFO) estimation for orthogonal frequency-division multiplexing (OFDM) has caught attention as OFDM systems have become widely adopted in recent years. In this paper, we design a novel double-differential (DD) codec with low computational complexity. Our design bypasses CFO and channel estimation, and is easy to implement at both transmitter and receiver. It also guarantees full multipath diversity, and reduces the peak-to-average power ratio from the number of subcarriers to the channel order. In addition, it is robust to CFO drifting. The closed form of the performance for our design is derived for OFDM transmissions over frequency-selective channels with CFO. Thorough simulation results corroborate our claims. View full abstract»

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  • The effect of narrowband interference on wideband wireless communication systems

    Page(s): 2139 - 2149
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB) |  | HTML iconHTML  

    This paper evaluates the performance of wideband communication systems in the presence of narrowband interference (NBI). In particular, we derive closed-form bit-error probability expressions for spread-spectrum systems by approximating narrowband interferers as independent asynchronous tone interferers. The scenarios considered include additive white Gaussian noise channels, flat-fading channels, and frequency-selective multipath fading channels. For multipath fading channels, we develop a new analytical framework based on perturbation theory to analyze the performance of a Rake receiver in Nakagami-m channels. Simulation results for NBI such as GSM and Bluetooth are in good agreement with our analytical results, showing the approach developed is useful for investigating the coexistence of ultrawide bandwidth systems with existing wireless systems. View full abstract»

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  • Shifted carrier-hopping prime codes for multicode keying in wavelength-time O-CDMA

    Page(s): 2150 - 2156
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    In this paper, we study the use of shifted carrier-hopping prime codes (CHPC) for multicode keying in wavelength-time optical code-division multiple-access (O-CDMA) systems. By using the code's good properties of zero autocorrelation sidelobes and cross-correlation functions of at most one, each user is assigned M=2m shifted copies of its own code matrix to represent m data bits per symbol with minimal interference. The advantages of our scheme are that: 1) a lower baud rate O-CDMA system can now support a higher bit rate; 2) no network synchronization is required; 3) no M-fold increase in code cardinality is needed, as compared with standard M-code keying; 4) the numbers of optical encoders and decoders can be reduced from M to one per user, a major hardware cost savings; and 5) user code confidentiality is enhanced, as compared with the transmission of one code matrix for each data-bit one in conventional "on-off keying" O-CDMA schemes. Finally, our performance analysis shows that there is a tradeoff between the error probability and the choice of M. View full abstract»

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Aims & Scope

IEEE Transactions on Communications focuses on all telecommunications including telephone, telegraphy, facsimile, and point-to-point television by electromagnetic propagation.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia