A continuous-phase frequency-shift-keying (CPFSK) signaling technique is suggested that combines convolutional encoding and multi-h signaling. In contrast to regular multi-h signaling, this technique changes the modul...
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A continuous-phase frequency-shift-keying (CPFSK) signaling technique is suggested that combines convolutional encoding and multi-h signaling. In contrast to regular multi-h signaling, this technique changes the modulation index in a preselected pattern in order to maximize the minimum Euclidean distance. A rate-1/2 convolutional encoder along with a 2-h quaternary CPFSK modulator which uses two fixed modulation indexes is considered. Minimum Euclidean distances are calculated corresponding to the best encoder/mapper combinations for different modulation index patterns at attractive pairs of modulation indexes. Numerical results obtained for encoder memory lengths of one and two are used to illustrate that the minimum Euclidean distance of coded CPFSK signals can be significantly increased by combining with multi-h signaling. Modulation index patterns which perform significantly better than regular multi-h signals are determined. An error event analysis over the additive-white-Gaussian noise channel is carried out to investigate the actual error rate performance and to verify the theoretical results.
This paper proposes and evaluates a new co-channel interference cancellation technique that utilizes orthogonal convolutional codes on a multipath Rayleigh fading channel, In a spread spectrum multiple access environm...
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This paper proposes and evaluates a new co-channel interference cancellation technique that utilizes orthogonal convolutional codes on a multipath Rayleigh fading channel, In a spread spectrum multiple access environment, co-channel interference (CCI) limits the performance of the communication link, To remove this interference, several CCI cancellation techniques have been proposed, including the technique that does not require the receiver to have knowledge of the cross-correlation between user sequences, This method leaves residual interference after the cancellation caused by errors in the initial decisions, To reduce the residual interference and improve the initial decisions, the proposed scheme utilizes the error-correcting capability of orthogonal convolutional codes, This paper evaluates the performance of this scheme, Our results show that the proposed CCI canceller offers all improvement in capacity by a factor of 1.5 similar to 3 as compared with a conventional canceller on a multipath Rayleigh fading channel, The proposed canceller works in the presence of residual interference due to imperfect cancellation, The proposed canceller also has a capacity improvement with the use of soft handoff in a multicell configuration.
The impact of the code rate and constraint length on the qualitative performance of optical interleave division multiple access (OIDMA) system is analyzed. The various topologies of convolution encoder design have imp...
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The impact of the code rate and constraint length on the qualitative performance of optical interleave division multiple access (OIDMA) system is analyzed. The various topologies of convolution encoder design have implemented by considering various shift registers as well as several Ex-OR gates to achieve the performance. Further, the bit error rate (BER) calculated for a different possible combination of random inter-leaver. The BER increases with the number of users, whereas it decreases with the code rate and constraint length.
The Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm is a well-known maximum a posteriori probability decoding algorithm which has been proposed earlier for point to point communication applications, employing block codes or...
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The Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm is a well-known maximum a posteriori probability decoding algorithm which has been proposed earlier for point to point communication applications, employing block codes or convolutional codes and turbo codes. This study describes an application of the BCJR algorithm for decoding the output of a multiple-access channel called the noisy three-user binary adder channel, in the presence of additive white Gaussian noise. The computer simulation results are presented for the overall coding performance in terms of bit error rate against signal-to-noise ratio.
Space-time convolutional codes, that provide maximum diversity and coding gain, are produced for cases with PSK modulation and various numbers of states and antennas. The codes are found using a new approach introduce...
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Space-time convolutional codes, that provide maximum diversity and coding gain, are produced for cases with PSK modulation and various numbers of states and antennas. The codes are found using a new approach introduced recently in a companion paper. The new approach provides an efficient method that allows a search for optimum codes for many practical problems. The new approach also provides a simple method for augmenting the criteria of maximum diversity and coding gain with a new measure which is shown to be extremely useful for evaluating code performance without extensive simulations. To validate the approach, an extensive set of simulation results are presented comparing the codes designed here to many other recently proposed space-time convolutional codes. The comparisons, given in terms of frame error rate (FER), indicate that our new method provides codes which yield excellent performance. The approach is especially useful for finding a handful of good codes. Selection among these codes can be made with a limited number of simulations for FER.
This paper suggests that multicarrier modulation reduces the complexity and the delay caused by the multiuser interference cancellation process utilizing convolutional codes. For spread spectrum multiple access, multi...
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This paper suggests that multicarrier modulation reduces the complexity and the delay caused by the multiuser interference cancellation process utilizing convolutional codes. For spread spectrum multiple access, multiuser interference (interference due to signals from other users) limits the performance of the communication link. To remove this interference, a multiuser interference cancellation technique which utilizes orthogonal convolutional codes has been proposed for the uplink (mobiles to a base station) of the cellular code-division multiple-access (CDMA) systems. However, this technique requires the large interleavers and the huge memory, or the artificial multipath diversity and the RAKE system to achieve sufficient coding gain hit is applied for wireless indoor communications and fading is slow compared to the data rate. To reduce the complexity of the canceller, multicarrier modulation is employed as it provides frequency diversity gain and coding gain without the interleavers or the RAKE system. This paper shows that the multicarrier modulation reduces the complexity of the canceller and still provides sufficient coding gain in order to cancel the multiuser interference. The canceller with decoding in the initial decision and multicarrier modulation improves capacity by a factor of 1.4 as compared with the canceller without decoding.
The Viterbi algorithm is a maximum likelihood means for decodingconvolutional codes and has thus played an important role in applications ranging from satellite communications to cellular telephony, In the past, Vite...
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The Viterbi algorithm is a maximum likelihood means for decodingconvolutional codes and has thus played an important role in applications ranging from satellite communications to cellular telephony, In the past, Viterbi decoders have usually been implemented using digital circuits. The speed of these digital decoders is directly related to the amount of parallelism in the design. As the constraint length of the code increases, parallelism becomes problematic due to the complexity of the decoder. In this paper an artificial neural network (ANN) Viterbi decoder is presented. The ANN decoder is significantly faster than comparable digital-only designs due to its fully parallel architecture. The fully parallel structure is obtained by implementing most of the Viterbi algorithm using analog neurons as opposed to digital circuits. Several modifications to the ANN decoder are considered, including an analog/digital hybrid design that results in an extremely fast and efficient decoder. The ANN decoder requires one-sixth the number of transistors required by the digital decoder. The connection weights of the ANN decoder are either +1 or -1, so weight considerations in the implementation are eliminated. This, together with the design's modularity and local connectivity, makes the ANN Viterbi decoder a natural fit for VLSI implementation. Simulation results are provided to show that the performance of the ANN decoder matches that of an ideal Viterbi decoder.
A prototype of a Digital Television Terrestrial Broadcasting System has been implemented according to the European DVB-T standard. The first step in the construction of this prototype involved parameter optimization v...
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A prototype of a Digital Television Terrestrial Broadcasting System has been implemented according to the European DVB-T standard. The first step in the construction of this prototype involved parameter optimization via simulation. This paper presents the optimization process of the system parameters and the final achieved BER performance. Important design aspects such as interleaving, convolutional puncturing codes, Viterbi decoding, pilot-based channel correction and optimal pilot power are considered. The DVB-T standard offers some suggested values of the C/N ratio needed to achieve the desired BER requirements in the receiver. However, they have been obtained assuming ideal channel correction and synchronization. Simulation results are provided here in non-ideal conditions.
A new decoding algorithm based on the modified Viterbi algorithm for repeat request systems is considered. A new asymptotic error probability bound is derived. It is shown that the error exponent for convolutional cod...
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A new decoding algorithm based on the modified Viterbi algorithm for repeat request systems is considered. A new asymptotic error probability bound is derived. It is shown that the error exponent for convolutional coding can be related to the exponent for block coding by a graphical method known as inverse concatenation construction.
The problem of avoiding infinite error propagation in noncatastrophic convolutional codes when using a truncated Viterbi decoder is considered. A truncation length tau is defined in terms of walks in the state diagram...
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The problem of avoiding infinite error propagation in noncatastrophic convolutional codes when using a truncated Viterbi decoder is considered. A truncation length tau is defined in terms of walks in the state diagram. The truncation length guarantees that, in the presence of a sufficiently long guard space, a truncated Viterbi decoder will always recover from any error event. This value of tau is the theoretically smallest possible truncation length.
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