OFDM modulation seems to be a good choice to deal with highly distorted transmission channels, and ldpc error correction codes allow the system performance to get close to the Shannon capacity. Performance improvement...
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ISBN:
(纸本)9781479904020;9781479904037
OFDM modulation seems to be a good choice to deal with highly distorted transmission channels, and ldpc error correction codes allow the system performance to get close to the Shannon capacity. Performance improvement of the ldpc-coded OFDM system can be accomplished by use of irregular binary ldpc codes along with an appropriate match between the bits of the codeword and the OFDM subchannels. Non-binary ldpc codes over high order finite fields GF(q) are an additional booster in case of short to moderate codeword lengths. In this paper, a simple practical method of the subchannel ordering for OFDM modulation with non-binary ldpc codes is proposed. The method exploits some special structural properties of the ldpc code parity check matrix generated based on the PEG (Progressive-Edge-Growth) algorithm. A noticeable improvement was achieved for regular codes when the column weights of the parity check matrix is equal to 2.
As a solution to limited bandwidth and high energy consumption of information infrastructure as well as heterogeneity of optical networks, a hybrid multidimensional coded modulation scheme is proposed employing all av...
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ISBN:
(纸本)9781479909025
As a solution to limited bandwidth and high energy consumption of information infrastructure as well as heterogeneity of optical networks, a hybrid multidimensional coded modulation scheme is proposed employing all available electrical and optical degrees of freedom. Electrical basis functions are based on either modified orthogonal polynomials or prolate spheroidal wave functions, while optical ones on polarization and spatial mode states. The proposed scheme is both multi-Tb/s and beyond 100 Tb/s enabling technology. Additionally, the proposed scheme provides the adaptive, software-defined, and dynamic allocation of bandwidth with fine granularity. Finally, the proposed scheme significantly outperforms the conventional polarization-division multiplexed QAM.
In this paper, we propose a hybrid multidimensional coded-modulation (CM) scheme based on a new multidimensional signal constellation design as a solution to limited bandwidth and high energy consumption of informatio...
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In this paper, we propose a hybrid multidimensional coded-modulation (CM) scheme based on a new multidimensional signal constellation design as a solution to limited bandwidth and high energy consumption of information infrastructure. This multidimensional signal constellation, herewith called vector-quantization-based signal constellation design (VQ-SCD), is based on the vector quantization theory. The proposed scheme employs both the electrical basis functions (in the form of the prolate spheroidal wave functions) and the optical basis functions (in the form of polarization and spatial mode states) as optical basis functions. The proposed coded VQ-SCD scheme is the enabling technology for optical serial transport with bit rates exceeding 1000 Tb/s (1 Pb/s). In addition, the CM scheme we proposed allows for the adaptive, elastic, and dynamic allocation of the bandwidth. This fine granularity bandwidth manipulation is envisioned as a part of future software-defined optical networking.
We describe the channel equalization problem, and its prior estimate of the channel state information (CSI), as a joint Bayesian estimation problem to improve each symbol posterior estimates at the input of the channe...
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We describe the channel equalization problem, and its prior estimate of the channel state information (CSI), as a joint Bayesian estimation problem to improve each symbol posterior estimates at the input of the channel decoder. Our approach takes into consideration not only the uncertainty due to the noise in the channel, but also the uncertainty in the CSI estimate. However, this solution cannot be computed in linear time, because it depends on all the transmitted symbols. Hence, we also put forward an approximation for each symbol's posterior, using the expectation propagation algorithm, which is optimal from the Kullback-Leibler divergence viewpoint and yields an equalization with a complexity identical to the BCJR algorithm. We also use a graphical model representation of the full posterior, in which the proposed approximation can be readily understood. The proposed posterior estimates are more accurate than those computed using the ML estimate for the CSI. In order to illustrate this point, we measure the error rate at the output of a low-density parity-check decoder, which needs the exact posterior for each symbol to detect the incoming word and it is sensitive to a mismatch in those posterior estimates. For example, for QPSK modulation and a channel with three taps, we can expect gains over 0.5 dB with same computational complexity as the ML receiver.
Next-generation dynamic and elastic optical networking can be enriched by the employment of several techniques that have been introduced recently. In this paper we consider the elastic networking potential of optical ...
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ISBN:
(纸本)9781467322270
Next-generation dynamic and elastic optical networking can be enriched by the employment of several techniques that have been introduced recently. In this paper we consider the elastic networking potential of optical orthogonal frequency division multiplexing (OFDM), spatial multiple input multiple output (MIMO), and multidimensional coded modulation. Specifically, these three advanced approaches are re-defined in the context of dynamic bandwidth routing and flexible lightpath assignment for future optical networks. Key aspects of the novel spectral-spatial networking concept are presented.
We propose a new strategy for cooperative transmit diversity based on physical layer network coding and multiuser detection. Physical-layer Network coding (PNC) exploits interference, instead of avoiding it, all sourc...
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We propose a new strategy for cooperative transmit diversity based on physical layer network coding and multiuser detection. Physical-layer Network coding (PNC) exploits interference, instead of avoiding it, all source nodes transmit simultaneously to significantly enhance network throughput. The scenario under consideration is one in which two source nodes A and B transmit information to a common destination node D. Simulation results show that our new scheme outperforms traditional cooperative diversity based on decode-and-forward about 1.5 dB in terms of frame-error-rate (FER) but less complexity.
CDMA systems in comparison with other communication systems, are resistant against unauthorized information detection attacks, yet have some weakness with respect to some eavesdropping techniques. Increasing the physi...
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ISBN:
(纸本)9781424437092
CDMA systems in comparison with other communication systems, are resistant against unauthorized information detection attacks, yet have some weakness with respect to some eavesdropping techniques. Increasing the physical layer built-in security through secure scrambling method is an advantageous method. Besides, using some capacity achieving codes such as ldpc codes, was shown that help the system for better secrecy and good performance. Here a ldpc coded CDMA system with AES scrambling as the secure method is described and analyzed. The performance of the system is acceptable along with all the security advantages mentioned above.
In this paper, we study the performance of our single carrier receiver model using turbo coding and regular low density parity check (ldpc) coding. The single carrier receiver utilizes filter bank based frequency doma...
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ISBN:
(纸本)9781424417223;9781424417216
In this paper, we study the performance of our single carrier receiver model using turbo coding and regular low density parity check (ldpc) coding. The single carrier receiver utilizes filter bank based frequency domain equalizer, which is then followed by a low complexity, iterative noise predictive decision feedback equalizer (NP-DFE). Furthermore, the average computation rate as a function of E-b/N-0 ratio is observed for different coding methods, thus characterizing the performance vs. complexity trade-offs in the considered receiver structure in terms of the channel coding. Clear performance benefits from the NP-DFE loop can be achieved and the averaged complexity increase in our system is tolerable in the E-b/N-0 range where frame error rates below 10(-1) are achieved. In addition, by fixing the maximum decoding complexity to be the same between turbo and ldpc codes, the performance of these codes is similar but the averaged complexity of the ldpc code saturates to a clearly lower level.
To find the minimum distance computation of ldpc codes is a NP problem,there has been no simple way to obtain the minimum distance of ldpc codes because of the code length being very *** provide a solution to deal wit...
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To find the minimum distance computation of ldpc codes is a NP problem,there has been no simple way to obtain the minimum distance of ldpc codes because of the code length being very *** provide a solution to deal with this hard problem,this paper develops an algorithm to estimate the weights and distance of ldpc codes based on generator *** paper establishes the upper bounds of weights and distances of ldpc codes by using the vectors of generator matrices,which is different from the existed probabilitistic search methods for the weights' and distances of LCPC *** proposed algorithm can greatly reduce the searching time of weights and *** the algorithm we can obtain some ldpc codes of great distances and being free girth *** verify the algorithms to be valid.
Broadband packet data services are demanded in the next generation mobile communications systems. Multi-carrier CDMA (MC-CDMA) is considered to be a promising wireless technique. Hybrid ARQ (HARQ) is a powerful error ...
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ISBN:
(纸本)9781424402632
Broadband packet data services are demanded in the next generation mobile communications systems. Multi-carrier CDMA (MC-CDMA) is considered to be a promising wireless technique. Hybrid ARQ (HARQ) is a powerful error control technique. It is known that the HARQ throughput performance of MC-CDMA degrades due to the residual inter-code interference (ICI) after frequency-domain equalization (FDE). The use of frequency-domain soft interference cancellation (FDSIC) technique can reduce the residual ICI and improve the throughput performance. An important technical problem is the generation of accurate residual ICI replica for FDSIC. In this paper, we consider low-density parity-check coded (ldpc-coded) MC-CDMA HARQ and generate the residual ICI replica from a-posteriori log-likelihood ratio (LLR) obtained by the ldpc decoder. We evaluate, by computer simulation, the throughput performance in a frequency-selective Rayleigh fading channel. We show that if the residual ICI is removed, MC- CDMA can provide better throughput performance than orthogonal frequency division multiplexing (OFDM).
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