Có 32+ tài liệu thuộc chủ đề "tín hiệu mạng"
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Let us now commence with a brief overview of the AQAM scheme.. A brief overview of the principles of AQAM in a narrow-band Rayleigh fading channel en- vironment is given here. These characteristics of the AQAM switching regime will be shown more explicitly in Section 4.3.4.. This trade-off is governed by the values of the switching thresholds 1,. In the...
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The schematic of the turbo encoder is shown in Figure 5.1. The iterative decoding structure of the turbo decoder is shown in Figure 5.3. L , Figure 5.3: Schematic of the turbo decoder.. is generated by subtracting the contribution of the channel outputs, as shown in Figure 5.3. Consequently, as the number of iterations increases, the estimation of the decoded...
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(a) SNR versus BEP over AWGN channels (b) PDF f7(y) of the instantaneous SNR y Over Rayleigh channel. Figure 6.2(a) depicts the instantaneous BEP as a function of the instantaneous channel SNR. The exact value of the outage probability is given by:. The average BEP P. Let us describe the detailed operation of the adaptive modem scheme of Figure 6.3....
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However, in stipulating this assump- tion, the delay incurred between channel quality estimation and the actual utilization of the estimate was neglected in the wideband AQAM schemẹ. The incorrect estimate precipitates further errors at the output of the equalizer. The performance of the fixed modulation modes of our AQAM scheme in conjunction 257. with error propagation is depicted in Figure...
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Consequently, as depicted in Figure 8.1, the passage of the input sequence { I k } through the channel results in the channel output sequence {vk} that can be expressed as. 7 , and it produces an estimate Ik-T of the transmitted signal IkPT. 2L+m possible combinations of the binary channel input sequence. Expounding further, we denote each of the...
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These switching thresholds govern the tradeoff between the mean BER and the BPS performance of the system. We will briefly summarise, how the performance of the equalizer and the AQAM scheme can be jointly optimized.. As expected, the AQAM switching criteria of the narrow-band scenario mentioned in Section 9.1 has to be modified for the wideband channel environment. Consequently, the...
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10.1 Introduction to Turbo Codes. Figure 10.1: Turbo encoder schematic.. Figure 10.2: Turbo decoder schematic.. Therefore, the iterative scheme shown in Figure 10.2 is usually used. 10.2 Jacobian Logarithmic RBF Equalizer. Expressing Equation 10.3 in a logarithmic form and substituting in the Jacobian logarithm, we obtain:. Note from Equation 10.5 that vil, is a summation of the delayed components. Figure...
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The soft values of the channel coded bits ck are typically quantified in the form of the log-likelihood ratio defined in Equation 10.6. Before passing the above a posteriori LLRs generated by the SISO equaliser to the SISO decoder of Figure 11.1, the contribution of the decoder - in the form of the a priori information C,". Subsequently, the channel...
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A Framework for Existing and Future Wireless Standards, submitted to the Proceedings of the IEEE OIEEE, 2001. Motivated by these requirements in the context of the CDMA-based third-generation wireless systems the outline of the chapter is as follows. In Section 12.2 we re- view the current state-of-the-art in multi-user detection with reference to the receiver family- tree of Figure 12.4....
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13.1 Introduction. The outline of the chapter is as follows. 13.2 Orthogonal Frequency Division Multiplexing. 13.2.1 Historical Perspective. ing techniques which aim to minimise the peak power of the OFDM signal. 13.2.1.2 Synchronization. 13.2.1.3 OFDM / CDMA. 13.2.1.4 Adaptive Antennas. 13.2.1.5 OFDM Applications. Figure 13.1: Schematic of N-subcarrier OFDM transmission system.. 13.2.2 OFDM Modem Structure. In practice, however, it is...
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Space-Time Trellis Coding versus Adaptive Modulation. 14.1 Introduction. 14.2 Space-Time Trellis Codes. 14.2.1 The 4-State, 4PSK Space-Time Trellis Encoder. SPACE-TIME TRELLIS CODES 591. Figure 14.1: The 4-state, 4PSK space-time trellis encoder.. Table 14.1: Operation of the space-time encoder of Figure 14.1.. Figure 14.2: The 4PSK constellation Figure 14.3: The 4-state, 4PSK space-time trellis code.. The 4PSK constellation points are seen...
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In Part I of this monograph initially the performance of the DFE was analysed using multi- level modulation modes over static multi-path Gaussian channels, as shown in Figure 2.10.. However, these experiments were conducted in a fast start-up environment, where adaptation was restricted to the duration of the training sequence length. In these experiments valuable insights were obtained with regards...