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Communications, IEEE Transactions on

Issue 1 • Date Jan. 1997

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Displaying Results 1 - 20 of 20
  • Comment on "Cycle slips in synchronizers subject to smooth narrow-band loop noise"

    Page(s): 19 - 20
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    This comment pinpoints and rectifies the misconception in the paper of Moeneclaey, Starzac and Meyr (see ibid., vol.36, no.7, p.867-74, 1988) where additive channel noise effects have been confused with phase jitter effects, leading to wrong, interpretations of basic synchronizer functionalities. View full abstract»

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  • Multilevel differential polarization shift keying

    Page(s): 95 - 102
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    We analyze the performance of coherent optical communication systems which employ polarization shift keying (PolSK) modulation, introducing for the first time the requirements for multilevel, differential PolSK. For M-ary signal constellations with M>2, the three-dimensional (3-D) nature of the signal constellations within Stokes space requires the use of double-differential modulation and detection (M-DDPolSK). Coding constraints on the signals place an additional restriction on such systems. We present detailed analysis and simulations for a 6-DDPolSK modulation scheme in which the signal points are located at the vertices of an octahedron in Stokes space View full abstract»

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  • Throughput analysis of some ARQ protocols in the presence of feedback errors

    Page(s): 35 - 44
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    Automatic-repeat-request (ARQ) protocols have been analyzed for quite some time, but the issue of errors in the feedback channel has not received much attention. In some applications, such as digital mobile communications, this issue can be important. Accordingly, this paper examines the effect of feedback errors on the throughputs of the stop-and-wait (SW), go-back-N (GBN), and selective repeat (SR) ARQ protocols for the ease of a point-to-point channel under some feedback information assumptions. It is shown that the deleterious effects of feedback errors on the throughputs of continuous (e.g., GBN and SR) ARQ protocols can be greatly reduced by a simple modification in the retransmission operation, provided that the “complete state” of the receiver is sent back with each acknowledgment View full abstract»

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  • On the analytical computation of the interference statistics with applications to the performance evaluation of mobile radio systems

    Page(s): 103 - 109
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    We provide a general analytical framework for the computation of the interference statistics in mobile radio cellular systems. This approach, which takes into account log-normal shadowing, distance path loss, best cell site selection and power control based on signal strength, applies to various cellular environments, including narrowband systems (e.g., IS-54 and Group Special Mobiles GSM) and code-division multiple-access (CDMA) systems. Some examples of application are provided View full abstract»

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  • Multidimensional trellis coded phase modulation using a multilevel concatenation approach. I. Code design

    Page(s): 64 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    The first part of this paper presents a simple and systematic technique for constructing multidimensional M-ary phase shift keying (MPSK) trellis coded modulation (TCM) codes. The construction is based on a multilevel concatenation approach. In which binary convolutional codes with good free branch distances are used as the outer codes and block MPSK modulation codes are used as the inner codes (or the signal spaces). Conditions on phase invariance of these codes are derived and a multistage decoding scheme for these codes is proposed. The proposed technique can be used to construct good codes for both the additive white Gaussian noise (AWGN) and fading channels as is shown in the second part of this paper View full abstract»

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  • Coding for a channel with quantization in the presence of an estimable interference

    Page(s): 45 - 51
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    The encoding and decoding schemes presented are aimed at enabling the transfer of data through a channel in which two types of interference are added to the transmitted signal and the sum is quantized. One of these interferences is known (or can be estimated), whereas the second is an additive white Gaussian noise (AWGN). Since the input of the quantizer is not accessible, the known interference can not be removed from the received signal. We show that the error rate for an uncoded transmission through this channel is unacceptably large, even for low noise levels and linear quantization. It is also shown that the problem becomes even more severe when a nonlinear quantization is present. Therefore, coding is essential and a huge coding gain is achievable in this application. An upper-bound on the error rate, contributed by the component codes of a multilevel code, has been developed for multistage decoding. Results of computer simulations of a practical case with optimal and suboptimal decoding algorithms, both developed in this paper, are presented View full abstract»

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  • Authors' reply [to “Comment on cycle slips in synchronizers subject to smooth narrow-band loop noise”]

    Page(s): 21 - 22
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    The claims in the comment of Popken (see ibid., vol.45, no.1, p.19-20, 1997) are wrong. We point out that the discrepancy of the cycle slip rates obtained in our paper and that of Meyr, Popken and Mueller (see ibid., vol.COM-34, no.5, p.436-45, 1986) is not due to a misconception in our paper, but rather to a different modeling of the loop noise. In order to obtain cycle slip rates by means of Fokker-Planck techniques, Meyr et al. were forced to use an oversimplified model, yielding essentially flat loop noise. In our paper, cycle slip rates were obtained by means of level crossing techniques, while preserving the smooth narrowband nature of the loop noise View full abstract»

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  • A continuously adaptive MLSE receiver for mobile communications: algorithm and performance

    Page(s): 80 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The paper presents a Euclidean distance maximum likelihood sequence estimation (MLSE) receiver, based on the Viterbi algorithm (VA), suitable for fading and noisy communications channels, as that specified by the Group Special Mobiles (GSM). In a mobile cellular system, the fast varying channel characteristics, due to the fading and Doppler effects, require adaptive methods to update the channel coefficients to the MLSE receiver. The proposed technique continuously estimates the channel characteristics directly within the metric calculation of the VA. At each step of the VA, the sequence associated to the path with the best metric value (minimum-survivor method) among the survivor paths is used to update the channel estimate (employing conventional adaptive algorithms) throughout the entire informative sequence. However, the detection of the transmitted data sequence is performed by the VA only at the end of each burst. The proposed technique allows simpler receiver implementation and the simulation results show a good performance of this adaptive MLSE receiver in typical GSM environments View full abstract»

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  • Integrating error detection into arithmetic coding

    Page(s): 1 - 3
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    Arithmetic coding for data compression has gained widespread acceptance as the right method for optimum compression when used with a suitable source model. A technique to implement error detection as part of the arithmetic coding process is described. Heuristic arguments are given to show that a small amount of extra redundancy can be very effective in detecting errors very quickly, and practical tests confirm this prediction View full abstract»

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  • Analytical distribution of linearly modulated cochannel interferers

    Page(s): 73 - 79
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    The closed form expressions of the probability density function (PDF), the cumulative distribution function (CDF) and the characteristic function of the disturbance due to a multilevel cochannel interferer are obtained. The analysis assumes L-level amplitude shift keying (L-ASK) modulated signals, nonreturn to zero (NRZ) pulses, transmission over a distortion-free channel and matched filter reception. The distribution for the multiple cochannel interferers case can then be obtained by means of the characteristic function method. As an application example, the closed-form expression of the error-floor for an L-ASK system in the presence of one cochannel interferer is given. The comparison with respect to the Gaussian approximation is also discussed View full abstract»

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  • Soft decision decoding of linear block codes based on ordered statistics for the Rayleigh fading channel with coherent detection

    Page(s): 12 - 14
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    The soft decision decoding algorithm based on the ordered statistics proposed by Fossorier and Lin (see IEEE Trans. Inform. Theory, vol.41, no.9, p.1379-96, 1995) is applied to the Rayleigh fading channel with coherent detection. For an (N, K) block code, it is shown that order-1 reprocessing, or equivalently considering K+1 codeword candidates, provides most of the coding gain over uncoded binary phase shift keying (BPSK). In addition to its contribution to coding for the Rayleigh fading channel, the article also provides a general framework for evaluating the error performance of an algorithm based on a total or partial ordering of a random variable (RV) depending on one or many other RVs and illustrates how the reprocessing method of Fossorier et al. relates to the reliability measures defining the ordering View full abstract»

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  • Good trellises for IC implementation of Viterbi decoders for linear block codes

    Page(s): 52 - 63
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    This paper investigates trellis structures of linear block codes for the integrated circuit (IC) implementation of Viterbi decoders capable of achieving high decoding speed while satisfying a constraint on the structural complexity of the trellis in terms of the maximum number of states at any particular depth. Only uniform sectionalizations of the code trellis diagram are considered. An upper-bound on the number of parallel and structurally identical (or isomorphic) subtrellises in a proper trellis for a code without exceeding the maximum state complexity of the minimal trellis of the code is first derived. Parallel structures of trellises with various section lengths for binary BCH and Reed-Muller (RM) codes of lengths 32 and 64 are analyzed. Next, the complexity of the IC implementation of a Viterbi decoder based on an L-section trellis diagram for a code is investigated. A structural property of a Viterbi decoder called add-compare-select (ACS)-connectivity which is related to state connectivity is introduced. This parameter affects the complexity of wire-routing (interconnections within the IC). The effect of five parameters namely: (1) effective computational complexity; (2) complexity of the ACS-circuit; (3) traceback complexity; (4) ACS-connectivity; and (5) branch complexity of a trellis diagram on the very large scale integration (VLSI) complexity of a Viterbi decoder is investigated. It is shown that an IC implementation of a Viterbi decoder based on a nonminimal trellis requires less area and is capable of operation at higher speed than one based on the minimal trellis when the commonly used ACS-array architecture is considered View full abstract»

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  • Data-aided frequency estimation for burst digital transmission

    Page(s): 23 - 25
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    Burst transmission of digital data is employed in several applications such as satellite time-division multiple access (TDMA) systems and terrestrial mobile cellular radio. We propose a new algorithm for carrier frequency estimation in burst-mode phase shift keying (PSK) transmissions. The algorithm is data-aided and clock-aided and has a feedforward structure that is easy to implement in digital form. Its estimation range is large, about ±20% of the symbol rate and its accuracy is close to the Cramer-Rao bound (CRB) for a signal-to-noise ratio (SNR) as low as 0 dB. Comparisons with earlier methods are discussed View full abstract»

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  • Modified Viterbi decoders for joint data detection and timing recovery of convolutionally encoded PPM and OPPM optical signals

    Page(s): 90 - 94
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    Two novel Viterbi decoders, known as joint Viterbi decoder (JVD) and enhanced Viterbi decoder (EVD), for synchronization and data detection are introduced and analyzed for convolutionally-encoded (CE) optical pulse-position modulation (PPM) and overlapping PPM (OPPM) channels. For the JVD algorithm, a count metric is employed to perform the Viterbi decoding in the absence of synchronization. For the EVD algorithm, a memory array is utilized to reduce the computation time of the JVD algorithm. With the aid of a previously proposed upper-bound and taking advantage of the minimal asymptotic normalized timing error (MANTE) concept, approximate performance measures for the EVD and JVD receivers are obtained View full abstract»

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  • A new wideband high frequency channel simulation system

    Page(s): 26 - 34
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    This paper provides a technical overview of a high frequency (HF) channel simulation system that is applicable to either narrowband or wideband HF channels. Although narrowband models of the HF channel have existed for many years, they are applicable only to a limited set of actual narrowband channel conditions. The need for an HF channel model that is valid for both narrow and wide bandwidths over a more extensive range of channel conditions motivated the research reported in this paper. Wideband propagation, noise, and interference models have been developed and implemented in a real-time digital simulator that utilizes state-of-the-art signal processing hardware with a throughput in excess of 1 mega samples/s. The simulator architecture has the flexibility to permit its application to future simulator designs as faster signal processing components become available. The current simulation system can be used for simulating radio channels other than HF because the propagation, noise, and interference models are implemented in software. This flexibility results in a very powerful test instrument View full abstract»

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  • Analysis of hybrid, coherent FDMA/CDMA systems in Ricean multipath fading

    Page(s): 15 - 18
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    This paper extends the analysis presented by Eng and Milstein (see IEEE J. Select. Areas Commun., vol.12, no.5, p.938-951, 1994) of a hybrid frequency division multiple access/code-division multiple-access [FDMA/CDMA (F/CDMA)] system in a Rayleigh fading environment to include the presence of a direct-path component (i.e., Ricean fading). The results show that a “wideband” CDMA system out performs a hybrid system, although the combination of a specular component and an exponentially decaying multipath intensity profile (MIP) with a large decay factor may result in only a minimal degradation of system performance for a hybrid system View full abstract»

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  • Partially coherent DS-SS performance in frequency selective multipath fading

    Page(s): 110 - 118
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    The bit-error rate (BER) performance of a direct sequence spread spectrum (DS-SS) signal, operating over a multipath Rayleigh fading channel, is investigated when corrupted by phase noise as well as additive white Gaussian noise (AWGN). The phase noise arises from phase locked loop (PLL) dynamics and results in imperfect receiver phase estimates whereby the phase errors assume Tikhonov densities. The phase estimates are used by a multipath-combining RAKE receiver for demodulation. Approximate upper-bounds on the bit error probability are obtained and evaluated for different combinations of channel parameters and for various values of the average loop signal-to-noise ratio (SNR). Results indicate that for a PLL with loop SNR 10 dB above the system E b0, the degradation is less than 3 dB, and for a loop SNR of 20 dB above Eb0, the degradation is less than 1 dB View full abstract»

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  • Differential PSK block demodulation over a flat correlated Rayleigh-fading channel

    Page(s): 9 - 11
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    A technique is proposed to design a block demodulator for differential phase shift keying (DPSK) signals over a frequency flat correlated Rayleigh-fading channel. The technique allows one to drastically reduce the error floor typically present in the bit error rate (BER) curves at high signal to noise ratios (SNRs). The main idea is to use the Karhunen-Loeve expansion to have a more precise description of the fading process at the receiver end View full abstract»

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  • Analysis of multidimensional trellis-coded MPSK in Rice-lognormal fading channels

    Page(s): 4 - 8
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    The paper addresses the analysis of multidimensional trellis-coded M-ary phase shift keying (MPSK) modulation over a Rice-lognormal fading channel model, applicable to a variety of environments and to both terrestrial and satellite mobile communications. Bounds to the bit error probability are derived and applied to the analysis of a few selected trellis-coded modulation (TCM) schemes. The results, confirmed by simulation, show that on the Rice channel there exists a threshold in bit energy-to-noise density ratio above which the effective code length is the dominant parameter, while the free distance is dominating below. However, the influence of both parameters is mitigated when shadowing is present View full abstract»

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  • A new evaluation criterion for Clos- and Benes-type rearrangeable switching networks

    Page(s): 119 - 126
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    An extended comparison and a classification of the control algorithms for rearrangeable switching networks is tried in this study. Besides of the failure probability Pf a new evaluation criterion is introduced, the mean number of rearranges R, the network performs in order to satisfy incoming calls. A simulation comparison for eight control algorithms concerning Clos-type networks and networks with 2×2 elements is attempted with very helpful results for the network design. Furthermore, some deadlock conditions discovered in one of these algorithms are completely recovered. The comparison is carried out for both evaluation criteria (Rm and Pf) and it is shown that the new criterion leads to a deep insight of the systems, necessary for a successful network design 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.

 

 

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Editor-in-Chief
Robert Schober
University of British Columbia