We use the sum-product algorithm (SPA) to propose a reduced-complexity detector for serially concatenated continuous phase modulated (SCCPM) signals with noisy channel state information (CSI) at the receiver. Two channel effects-phase noise (PN) and flat fading-are tackled using the statistical model and associated factor graph (FG) of the problem. Although optimal performance is not assured due to the loopy nature of the FG, as well as simplifying assumptions made in the algorithm development, simulations show that very significant performance gains are possible, and the gap between systems with noiseless and noisy CSI can be reduced to about 1 dB using the proposed methods. The increase in complexity compared to the conventional decoder, which treats CSI estimates as if they were equal to their true values, is small.

We investigate the detection of space time codes (STC) modulated using continuous phase modulation (CPM), in quasi-static fading channels. A symbol-by-symbol iterative detector with an optimum front-end is derived, and its reduced-complexity implementation is considered. Also, we have introduced several full-rank STC-CPM systems, constructed by combining full-diversity STCs with simple, widely-used CPM schemes, and introducing a small frequency offset. According to the simulation results, the bit error rate (BER) performance of the detector for quasi-static fading is around 1 dB from the case without fading. Furthermore, a comparison of the performance of the proposed detector with results from previous work on STC-CPM showed an improvement in the range of 2-3 dB. Moreover, the detector is robust to the errors in estimating the channel state information (CSI), which is a desirable feature for practical implementation.

We use the sum-product algorithm to handle the problem of phase noise (PN) in the detection of a serially concatenated continuous phase modulated system. Although optimal performance is not assured due to the loopy nature of the factor graph describing the problem, as well as simplifications made in the algorithm development, simulations show that significant performance gains are possible, and the gap between systems with and without PN can be reduced to about 1 dB using the proposed method. The increase in complexity compared to ignoring PN is small, and no periodic pilot symbols are inserted within a code word, although we assume the availability of a phase-locking mechanism to set the initial phase offset to a small range around zero. We use a different Gaussian approximation from what has been previously proposed, and this results in a less complex algorithm

We investigate the detection of space time codes (STC) modulated using continuous phase modulation (CPM) in quasi-static fading channels. An optimum symbol-by-symbol iterative detector is derived and its practical implementation using the concept of principal component analysis (PCA) is considered. To assess the performance, numerical examples for different STC-CPM schemes are presented. According to the simulation results, the proposed detector obtains very good power efficiencies. Moreover, the bit error rate (BER) performance of the detector for quasi-static fading is very close to the case without fading, highlighting its effectiveness to mitigate fading.

We investigate the performance of space time codes (STCs) modulated using continuous phase modulation (CPM) for different quasi-static Rayleigh fading channels. We propose few STC-CPM schemes that satisfy the full-rank condition, which is necessary to achieve maximum diversity, and also provide some guideline on how to find such STC-CPM schemes. To assess the performance, numerical examples are presented, and according to these results, the proposed STC-CPM systems perform similar to linearly modulated STCs

We investigate the detection of space time coded (STC) signals modulated using continuous phase modulation (CPM) in fast Rayleigh fading channels. A symbol-by-symbol iterative detector with an optimum front-end is derived, and its practical implementation using the concept of principal component analysis (PCA) is considered. To assess the performance, numerical examples for different STC-CPM schemes are presented. According to the simulation results, the proposed detector obtains very good power efficiencies. Moreover, the bit error rate (BER) performance of the proposed detector is in the range of 0.5-1 dB from the case without fading, highlighting its effectiveness to mitigate fading.

We propose a new stopping criterion for iterative decoding of concatenated codes. The new stopping rule observes the a priori probabilities of different symbols and stops further iterations in the decoder whenever the average number of symbols in a trellis section below a certain a priori value, is above a predefined threshold. According to numerical examples for some practical transmission systems, the proposed criterion saves more decoding iterations than existing stopping rules. Also, it performs very close to the maximum possible limit of any stopping rule, with a very small degradation in bit error rate (BER) performance.

We propose a new reduced-complexity iterative decoding algorithm. The main concept is to approximate the aposteriori probabilities (APP) by a set of few sequences, and to reduce the size of this set with iterations. According to the numerical results on the bit error rate (BER) performance and the convergence behavior by extrinsic information transfer (EXIT) chart analysis, the algorithm could obtain a good balance between performance and complexity.

A new algorithm to reduce the computational complexity of iterative decoding is presented. The algorithm reduces the complexity by removing certain branches from the corresponding trellis diagram. A threshold on a priori values is used as the elimination criterion. To assess the performance, numerical results for serially concatenated convolutional codes transmitted over an additive white Gaussian noise channel is presented. The results show that for the system considered, the algorithm can reduce the complexity by one third with a negligible degradation in error performance.