1,720,970 research outputs found
Multi-Level Radial Basis Function Network Based Equalisers for Rayleigh Channel
No full textRadial Basis Function (RBF) network based channel equalisers have a close relationship with Bayesian schemes. Decision feedback is introduced in the design of the RBF equaliser in order to reduce its computational complexity. The RBF Decision Feedback Equaliser (DFE) was found to give similar performance to the conventional mean square error (MSE) DFE over Gaussian channels using various Quadrature Amplitude Modulation (QAM) schemes, while requiring a lower feedforward and feedback order. Over Rayleigh-fading channels similar findings were valid for binary modulation, while for higher order modems the RBF based DFE requires increased feedforward and feedback orders in order to outperform the conventional MSE DFE scheme
A Wideband Radial Basis Function Decision Feedback Equaliser Assisted Burst-by-Burst Adaptive Modem
No full textThe performance of radial basis function-based decision feedback equalized (RBF DFE) burst-by-burst adaptive quadrature amplitude modulation (AQAM) is presented for transmissions over dispersive wide-band mobile channels. This scheme is shown to give a significant improvement in terms of the mean bit error rate (BER) and bits per symbol (BPS) performance compared to that of the individual fixed modulation modes. The structural equivalence of the RBF DFE to the optimal Bayesian equalizer enables it to potentially outperform the conventional Kalman-filtered AQAM DFE scheme. Index Terms—Adaptive modulation, decision feedback equalization, radial basis function, wide-band modem
Upper-Bound Performance of Radial Basis Function Decision Feedback Equalised Burst-by-Burst Adaptive Modulation
No full textThe upper-bound performance of radial basis function decision feedback equalised (RBF DFE) burst-by-burst adaptive modulation is presented for tranmissions over dispersive wideband mobile channels. The RBF DFE is capable of estimating the 'short term bit error rate' of the received data burst and this estimate is used as the modem mode switching criterion in order to switch between different modulation schemes. The performance of this scheme and that of the individual fixed modulation schemes is compared, demonstrating a significant mean bit error rate (BER) and bits per second (BPS) performance improvement
Radial Basis Function Decision Feedback Equaliser Assisted Burst-by-Burst Adaptive Modulation
No full textThe performance of radial basis function decision feedback equalised burst-by-burst adaptive modulation is presented for transmission over dispersive wideband mobile channels. Radial Basis Function (RBF) network based channel equalisers have a close relationship with Bayesian schemes. The RBF decision feedback equaliser (RBF DFE) is capable of estimating the 'short term bit error rate' of the received data burst and this estimate is used as the modem mode switching criterion in order to switch between different modulation schemes. This scheme is shown to give a significant improvement in terms of mean bit error rate (BER) and bits per symbol (BPS) performance compared to that of the individual fixed modulation schemes
Turbo Equalization of Convolutional Coded and Concatenated Space Time Trellis Coded Systems using Radial Basis Function Aided Equalizers
No full textIn this contribution a reduced-complexity radial basis function (RBF) aided neural-network based turbo equalization (TEQ) scheme is proposed for employment in a serially concatenated convolutional coded and systematic space time trellis coded (CC-SSTTC) arrangement. A two-path Rayleigh fading channel having a normalised Doppler frequency of 3.3615 x l0E-05 was used. The BER performance of the RBF-CC-SSTTC(4,4) scheme employing a transmission burst consisting of 100 symbols using a space-time-trellis (STT) interleaver of at least 400 symbols and eight turbo equalization iterations was found to be similar to that of the CC-SSTTC system using a trellis-based TEQ, which attains the optimum performance. However, the Jacobian RBF based TEQ provided a complexity reduction factor of 14
Radial Basis Function Assisted Turbo Equalization
No full textThis paper presents a turbo equalization (TEQ) scheme, which employs a radial basis function (RBF)-based equalizer instead of the conventional trellis-based equalizer of Douillard et al. Structural, computational complexity, and performance comparisons of the RBF-based and trellis-based TEQs are provided. The decision feedback-assisted RBF TEQ is capable of attaining a similar performance to the logarithmic maximum scheme in the context of both binary phase-shift keying (BPSK) and quaternary phase-shift keying (QPSK) modulation, while achieving a factor 2.5 and 3 lower computational complexity, respectively. However, there is a 2.5-dB performance loss in the context of 16 quadrature amplitude modulation (QAM), which suffers more dramatically from the phenomenon of erroneous decision-feedback effects. A novel element of our design, in order to further reduce the computational complexity of the RBF TEQ, is that symbol equalizations are invoked at current iterations only if the decoded symbol has a high error probability. This techniques provides 37% and 54% computational complexity reduction compared to the full-complexity RBF TEQ for the BPSK RBF TEQ and 16QAM RBF TEQ, respectively, with little performance degradation, when communicating over dispersive Rayleigh fading channels. Index Terms—Decision-feedback equalizer (DFE), Jacobian logarithm, neural network, radial basis function (RBF), turbo coding, turbo equalization (TEQ)
Iterative Radial Basis Function Assisted Turbo Equalisation of Various Coded Modulation Schemes
No full textA Radial Basis Function (RBF) assisted turbo equaliser (TEQ) scheme is investigated, which is based on various coded modulation schemes. Specifically, Trellis Coded Modulation (TCM), Turbo Trellis Coded Modulation (TTCM), Bit-Interleaved Coded Modulation (BICM) and BICM with iterative decoding (BICM-ID) are studied, when communicating over frequency selective fading channels. At a given complexity, the TTCM RBF-TEQ provides the best Bit Error Ratio (BER) and Frame Error Ratio (FER) performance. The RBF-TEQ structure is shown to provide an SNR performance improvement of about 5.5dB at a BER of 10-4 in comparison to the conventional non-iterative DFE scheme
Genetic Algorithm Aided Radial Basis Function Assisted Multiuser Detection for Synchronous CDMA
No full textRadial Basis Function Assisted Turbo Equalisation
No full textThis paper presents a novel turbo equalisation scheme, which employs a Radial Basis Function (RBF) Decision Feedback Equaliser (DFE) and the so-called Jacobian logarithmic complexity reduction technique instead of the conventional trellis-based equaliser. The proposed turbo equaliser is shown to achieve identical bit error rate (BER) performance to the conventional turbo equaliser, while incurring a factor 4.4 lower ‘per-iteration’ complexity in the context of 4-level Quadrature Amplitude Modulation (4QAM)
Block Turbo Coded Burst-by-Burst Adaptive Radial Basis Function Decision Feedback Equaliser Assisted Modems
No full textA novel adaptive modem scheme is to be presented for transmissions over wideband mobile channels, which employs a Radial Basis Function (RBF) based decision feedback equaliser, in order to mitigate the effects of the dispersive wideband channel. Turbo codes are invoked for improving the bit error rate (BER) and bits per symbol (BPS) performance of the scheme, which is shown to give a significant improvement in terms of mean BPS performance compared to that of the uncoded RBF equaliser assisted adaptive modem
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