Performance of equalized I-Q 16-QAM in frequency selective fading

The demand for high speed wireless systems dictates the use of bandwidth efficient modulation schemes. Trellis coded I-Q 16-QAM is shown here to be suitable for such applications. The performance of this scheme with decision feedback equalization is evaluated over a two-ray Rayleigh channel. Comparisons between the I-Q scheme with a conventional TCM scheme based on 8-PSK show coding gains of about 4 dB at a BER of 10 -

Decision feedback equalisation of coded I-Q QPSK in mobile radioenvironments

The bit error rate (BER) performance of equalised I-Q quadrature phase-shift keying (QPSK) is evaluated for wideband cellular systems. Decision feedback equalisation with the square-root Kalman updating algorithm is employed for I-Q coded systems. A gain of about 6 dB is achieved in favour of the I-Q scheme compared with the conventional Gray-mapped QPSK at a BER of 10-

Performance of equalized I-Q QPSK over 2-ray Rayleigh fading

In many wideband cellular systems, the channel experiences frequency selective fading. This paper evaluates the bit error rate (BER) performance of equalized I-Q QPSK over frequency selective Rayleigh fading channels. I-Q trellis codes were shown to possess excellent inherent minimum time diversity over flat fading Rayleigh channels. However, they have not been examined for frequency-selective fading channels, where channel equalization is required. In this work, I-Q QPSK systems performance over these channels employing a decision feedback equalizer (DFE) is evaluated. Very reliable communication over the mobile channel is obtained using I-Q QPSK combined with interleaving and adaptive equalization compared to the traditional Gray-mapped trellis code

Performance of equalized I-Q 16-QAM in frequency selective fading

The demand for high speed wireless systems dictates the use of bandwidth efficient modulation schemes. Trellis coded I-Q 16-QAM is shown here to be suitable for such applications. The performance of this scheme with decision feedback equalization is evaluated over a two-ray Rayleigh channel. Comparisons between the I-Q scheme with a conventional TCM scheme based on 8-PSK show coding gains of about 4 dB at a BER of 10 -

Performance of equalized I-Q QPSK over 2-ray Rayleigh fading

In many wideband cellular systems, the channel experiences frequency selective fading. This paper evaluates the bit error rate (BER) performance of equalized I-Q QPSK over frequency selective Rayleigh fading channels. I-Q trellis codes were shown to possess excellent inherent minimum time diversity over flat fading Rayleigh channels. However, they have not been examined for frequency-selective fading channels, where channel equalization is required. In this work, I-Q QPSK systems performance over these channels employing a decision feedback equalizer (DFE) is evaluated. Very reliable communication over the mobile channel is obtained using I-Q QPSK combined with interleaving and adaptive equalization compared to the traditional Gray-mapped trellis code

Design and Performance of Trellis Codes for Wireless Channels

Signal fading is one of the primary sources of performance degradation in mobile radio (wireless) systems. This dissertation addresses three different techniques to improve the performance of communication systems over fading channels, namely trellis coded modulation (TCM), space diversity and sequence maximum a posteriori decoding (MAP).In the first part, TCM schemes that provide high coding gains over the flat, slow Rayleigh distributed fading channel are presented. It is shown that the use of two encoders in parallel used to specify the in-phase and quadrature components of the transmitted signal results in large performance improvements in bit error rates when compared with conventional TCM schemes in which a single encoder is used. Using this approach which we label ﲉ-Q TCM codes with bandwidth efficiencies of 1, 2, and 3 bits/sec/Hz are described for various constraint lengths. The performance of these codes is evaluated using tight upper bounds and simulation.In the second part, the use of space diversity with three different combining schemes is investigated. Expressions for the cutoff rate parameter are shown for the three combining schemes over the fully interleaved Rayleigh-distributed flat fading channel. Also, tight upper bounds on the pairwise error probability are derived for the three combining schemes. Examples of I-Q TCM schemes with diversity combining are shown. The cutoff rate and a tight upper bound on the pairwise error probability are also derived for maximal ration combining with correlated branches.In the last part the problem of reliably transmitting trellis coded signals over very noisy channels is considered. Sequence maximum a posteriori (MAP) decoding of correlated signals transmitted over very noisy AWGN and Rayleigh channels is presented. A variety of different systems with different sources, modulation schemes, encoder rates and complexities are simulated. Sequence MAP decoding proves to substantially improve the performance at very noisy channel conditions especially for systems with moderate redundancies and encoder rates. A practical example for coding the CELP line spectral parameters (LSPs) is also considered. Two source models are used. Coding gains of as much as 4 dB are achieved

Performance of Equalized I-Q 16 QAM in Frequency Selective Fading

The demand for high speed wireless systems dictates the use of bandwidth efficient modulation schemes. Trellis coded I-Q 16-QAM is shown here to be suitable for such applications. The performance of this scheme with decision feedback equalization is evaluated over a two-ray Rayleigh channel. Comparisons between the I-Q scheme with a conventional TCM scheme based on 8-PSK show coding gains of about 4 dB at a BER of 10-3

Space-Time Trellis Coded 8PSK Schemes for Rapid Rayleigh Fading Channels

This paper presents the design of 8PSK space-time (ST) trellis codes suitable for rapid fading channels. The proposed codes utilize the design criteria of ST codes over rapid fading channels. Two different approaches have been used. The first approach maximizes the symbol-wise Hamming distance (HD) between signals leaving from or entering to the same encoder′s state. In the second approach, set partitioning based on maximizing the sum of squared Euclidean distances (SSED) between the ST signals is performed; then, the branch-wise HD is maximized. The proposed codes were simulated over independent and correlated Rayleigh fading channels. Coding gains up to 4 dB have been observed over other ST trellis codes of the same complexity

Performance of Equalized I-Q 16 QAM in Frequency Selective Fading

The demand for high speed wireless systems dictates the use of bandwidth efficient modulation schemes. Trellis coded I-Q 16-QAM is shown here to be suitable for such applications. The performance of this scheme with decision feedback equalization is evaluated over a two-ray Rayleigh channel. Comparisons between the I-Q scheme with a conventional TCM scheme based on 8-PSK show coding gains of about 4 dB at a BER of 10-3