ISSN:1124-318X    

DOI:10.1002/ett.4460040302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460040303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460040304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractAn overview is provided of the modulation techniques that are being considered for a new voiceband modem Recommendation, nicknamed V.fast. These techniques include adaptive bandwidth operation for automatically selecting the transmission band, multi‐dimensional trollis coded modulation for higher coding gain, constellation shaping for higher shaping gain, precoding and pre‐emphasis for advanced equalization, and warping for resistance against signal‐dependent impairments. Simulation results are presented to illustrate performance. By adaptively selecting an appropriate combination of these modulation techniques based on line conditions, V.fast modems are expected to double the maximum data rate of standard m

ISSN:1124-318X    

DOI:10.1002/ett.4460040305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this paper, we present a trellis‐coded multicarrier transceiver system, known as Discrete Multitone modulation, for the application of transmitting digital data at the El rate of 2.048 Mbit/s over existing copper telephone lines. The service of El‐HDSL (El‐rate High‐speed Digital Subscriber Lines) is currently being studied by ETSI for future deployment in Europe. Because of severe crosstalk and additive white Gaussian noise (AWGN) encountered in El‐HDSL, the application of a powerful trellis code is highly desirable to ensure reliable system performance, with a required bit‐error‐rate (BER) of no more than 10−7, at the desired El data rate. Detailed descriptions of the DMT transmitter and receiver structures are given, and projected performance results, both with and without the addition of a trellis code, are presented. Because of the different transmission environments encountered in the various countries in Europe, we have performed our computer simulation on both British and German (1) copper twisted‐pairs. We find that with the addition of Wei's powerful 4‐D 16‐state trellis code, we can achieve the El rate with a positive margin over all loops tested using either one or two sets of twisted‐pairs only, depending on the particula

ISSN:1124-318X    

DOI:10.1002/ett.4460040306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractUsing a 2‐step partitioning of the signal constellation and Reed‐Muller component codes, we construct block‐coded modulation (BCM) schemes that achieve an asymptotic coding gain close to 6 dB. The component code associated to the first partitioning step is a distance‐4 or a distance‐8 Reed‐Muller code, and the code associated to the second partitioning step is a simple parity‐check code. We investigate BCM schemes with square signal constellations and a fractional number of information bits per symbol as well as BCM schemes with circular signal constellations and an integer number of information bits per symbol. We use multistage decoding with a Viterbi algorithm for the first component code using the trellis description given by Forney. Our results indicate that with short block lengdis, these BCM schemes compare favorably with trellis coded modulation (TCM) of similar complexity. Due to the rapid increase of the error coefficient, however, they lose their advantage as the block len

ISSN:1124-318X    

DOI:10.1002/ett.4460040307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractWe present the main results of a study devoted to efficient implementation of multilevel coded modulation schemes. The key point here is that the proposed design is flexible, in the sense that the same hardware allows for the implementation of several coded schemes. This goal is achieved by associating a two‐dimensional binary partition chain with a set of punctured convo‐lutional codes. System performance is evaluated through its error probability. This is derived from the weight enumerators of the coded modulation, and the results are confirmed by computer simulation. Hardware implementation is also described brie

ISSN:1124-318X    

DOI:10.1002/ett.4460040308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractOptimum detectors for CPM use in general a large number of filters in order to calculate the optimum metrics. In this paper, we propose correlation detectors that calculate its metrics in a subspace of the signal space. The subspace is selected such that the asymptotic error performance is optimized for the given dimensionality. We focus on noncoherent detectors but show also some results for coherent detectors. The subspace metric calculation is combined with previously published reduced complexity decoding algorithms such as the SAN(B) and RSSD algorithms. Optimum subspace correlation detectors with different number of filters are found for both binary and quaternary CPM schemes. Their error performance on an AWGN channel is derived analytically through the use of a minimum Euclidean distance approach and is also simulated through the symbol error probability. Comparison is done with the optimum detectors. A close agreement between minimum distance and simulated symbol error probability is found for all considered detectors. We find that in most cases only 4 to 6 matched filters are needed in order to obtain a performance that is close to optimum. This corresponds to at least a five‐fold reduction in number of filters and with the reduced complexity search algorithms for making symbol decisions this leads to a dramatic reduction in overall complexit

ISSN:1124-318X    

DOI:10.1002/ett.4460040309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractMultilevel codes give an impressive asymptotic coding gain measured in dB. However, when classical multistage decoding is used, this gain can only be partly realized at bit error rates (BER) around 10−5. It is shown how multistage decoding can be improved for this BER range. We use interleaving between the levels, pass reliability information between the different stages by applying “Soft‐Output” decoders, and apply re‐iterated decoding. In the latter case lower levels are again decoded using the results of the higher levels. It is shown for coded 8‐PSK that additional coding gains up to 2 dB are achieved by these means at the cost of modest complexity, but the decoding delay i

ISSN:1124-318X    

DOI:10.1002/ett.4460040310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIt is by now well known that combined channel coding and digital modulation (in short coded modulation) yield power and bandwidth efficient digital transmission schemes for the Gaussian channel. These schemes perform closer to channel capacity than those where coding and modulation are treated separately. More recently, coded modulation methods have been investigated for transmission over Rayleigh fading channels. It has been discovered that systems optimized for the Gaussian channel are not optimum for fading channels. This is primarily due to the importance of built‐in time diversity of the coded modulation scheme for fading channels.In this paper we give a brief overview of recent developments in signal design for Rayleigh fading channels. Mainly schemes based on phase shift keying are presented. Theoretical guidance for design and identification of the most important system parameters are given. A couple of detailed examples of code designs and their error probability performance are also given. Optimum and suboptimum receivers are discussed. An overview of analytical performance analysis tools, as well as code designs for both trellis coded modulation and block coded modulation is included in the paper. Methods for unequal error protection are given. Potential application areas are identified. An extensive reference list is supplie

ISSN:1124-318X    

DOI:10.1002/ett.4460040311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY