Unitary space-time symbol-based SCCC

In this paper, we focus on the design of optimized binary convolutional codes (CCs) and serially concatenated convolutional codes (SCCCs) in the presence of a-priori information (API) at the receiver. For large signal-to-noise ratios (SNRs), we first propose a CC design criterion based on the minimization of a union bound on the bit error probability (BEP). In this case, relevant performance gains, with respect to previously proposed CCs, are obtained. These gains persist even in the presence of estimation errors on the API. Then, we apply the same union bound-based design criterion to SCCCs. Since the BEP of SCCCs is characterized by a typical waterfall shape, the proposed union bound-based design criterion is accurate only at large SNR, to estimate the BEP floor. In order to complement this analysis, we propose a density evolution-based approach to optimize the SCCC design in terms of minimization of the SNR of the knee of the BEP curve. The obtained simulation results show substantial gains with respect to previously proposed parallel concatenated convolutional coding (PCCCing) schemes optimized under the assumption of no API at the decoder. Moreover, in the presence of strong API the proposed SCCCs allow to approach the Shannon limit (SL) more than any previously proposed turbo coding scheme.

An analysis of performance of Serially Concatenated Convolutional Codes (SCCC) is evaluated on Additive White Gaussian Noise model channel, which is used as a basis, and actions of SCCC on Raleigh flat slow and flat fast faded channels are evaluated in this research work. In DCS the SCCC are utilized to reduce the bit error rates. SCCC encoder consists of RSCC. The major thrust is iterative decoding. This research has utilized BCJR and TDA decoding algorithms. This research analyzed SCCC with interleaved scheme. The BPSK modulation was considered. Performance metric for SCCC over Memory less AWGN channel, and memory based channels i.e. Rayleigh slow and fast Faded Channel is BER verses SNR.

The paper presents a novel cooperative coding scheme using punctured serial concatenated convolutional codes (SCCC). We evaluate its performance in terms of frame error rate (FER) under two cooperation protocols: a decode-and-forward protocol in conjunction with automatic repeat request (ARQ), by which the relay sends an acknowledge bit (ACK) back to the source to indicate whether its data packet is correctly decoded; an adaptive amplify-and-forward protocol, where the amplifying relay node cooperates to forward the message only when the inter-user link gain is above a certain threshold. In both cases, the destination makes the decision on each transmitted bit after appropriately combining signals and performing iterative decoding. Simulation results show that SCCC-based cooperative coding achieves full spatial diversity and exhibits a similar FER performance to that using parallel concatenated convolutional codes (PCCC). At the price of channel feedback, the adaptive decode-and-forward algorithm demonstrates a relatively lower FER than the adaptive amplify-and-forward scheme. Amplified cooperation experiences severe performance degradation due to the inefficiency of repetition coding and error propagation, especially when the quality of the source-relay link deteriorates; however, if the threshold for carrying cooperation is carefully selected, the adaptive amplify-and-forward protocol can perform comparably to the decode-and-forward protocol.

International audience

The paper proposes an analytical method to solve the rate allocation problem in serial concatenated convolutional codes (SCCCs). The goal is to find the best rate allocation between the inner and the outer constituent convolutional codes of an SCCC for constant overall code rate, interleaver size and complexity. Simulation results are shown in the paper to demonstrate the optimum and superior design criteria. In addition, the ‘density evolution’ model is shown to verify the proposed rate allocation method, while indicating that a high rate inner code should not be used for SCCCs. Finally, it is also shown that the upper bounds on BER of ML decoded SCCCs do not provide good design criteria for allocating the rate in iteratively decoded SCCCs.

A coded wideband MC-CDMA system is considered for high-bit-rate data transmission in a typical outdoor environment with Rayleigh multipath fading. First, two powerful interleaved concatenated coding techniques, turbo and serially concatenated convolutional codes (SCCC) codes are applied in the downlink system and important conclusions are derived on their relative performance behavior in this type of system. Simulation results indicate some of the relative merits of SCCC on achieving very low error rates, with relative mitigation of error floor behavior at the typical BER range of interest for wireless data applications. Next, the more critical uplink system is considered, which requires a multiuser detection technique in combination with powerful coding to achieve similar performance. Successive interference cancellation with SCCC coding is presented, with computation of optimal log-likelihood ratios required for this type of interference cancellation followed by SCCC decoding. Application of SCCC coding and interference cancellation has improved the system performance significantly even in the fully loaded case. Based on these results, the combination of SCCC coding and successive cancellation is found to be attractive for high-rate data transmission in the uplink MC-CDMA.

We compare the asymptotic performance of parallel concatenated codes (PCCs) and serial concatenated codes (SCCs) over GF(4). We construct such codes using optimal nonbinary convolutional codes where optimality is in the sense of achieving the largest minimum distance for a fixed number of encoder states. Code rates of the form K/sub 0//(K/sub 0/ + 1) for K/sub 0/ = 1, 8, and 64 are considered. For all of these code rates, we find the minimum distance and its multiplicity for both concatenated code systems. This is accomplished by feeding the encoder with all possible weight-two and weight-three input information patterns and monitoring, at the output of the encoder, the weight of the corresponding codewords and their multiplicity. Our analytical results indicate that the SCC codes outperform their counterpart PCC codes with much lower complexity.

For space-time bit-interleaved coded modulation (ST-BICM) systems with iterative decoding, the overall perfor- mance is affected by the chosen mapping. In bit error rate (BER) curves, one mapping reaches an error floor at a low signal- to-noise ratio (SNR), while other mappings result in a lower error floor at a higher SNR. The constellation mappings are divided into groups where each group exhibits a distinctive BER curve. We show that the convergence abscissa of the system depends on the average total bit errors and the harmonic mean of the minimum squared Euclidean distance. In this paper, we characterize all mapping groups for ST-BICM with 8PSK and present the optimal selection for each mapping group over independent fading channels. I. INTRODUCTION Space-time coding techniques significantly improve trans- mission efficiency in radio channels by using multiple transmit and/or receive antennas and coordination of the signaling over these antennas. Bit-interleaved coded modulation with iterative decoding (BICM-ID) gives good diversity gains and Euclidean distance property with higher order modulation schemes using well known binary convolutional codes (1). Tonello (2) combined these two schemes as space-time BICM (ST-BICM) with Gray mapping. In this paper, we will first show that the asymptotic BER performance of ST-BICM system is equivalent to the single antenna BICM-ID case even when the throughput of ST-BICM is higher. This indicates that the total data rate of ST-BICM can be increased linearly with the number of transmit antennas while maintaining the same error probability as BICM-ID. This demonstrates the superior performance of ST-BICM. Motivated by the fact that the ST-BICM performance can be characterized by BICM-ID with the same code and mapping, we optimize the ST-BICM mappings based on the BICM-ID parameters. While the error floor (EF) bound (1) offers a good match for an error floor region, a heuristic analysis is still needed to study BER curve behaviors of BICM-ID for the water fall region. Thus, we derive design considerations based on both

We investigate the impact of imperfect channel state information (CSI) on the bit error rate (BER) performance of uncoded and coded modulation schemes over Nakagami fading channels using the model proposed in C. Polprasert and JA Ritcey (2005). The analytical and asymptotic BER performance of uncoded M-PSK modulation is evaluated and verified by the simulation. For coded modulation, the error free feedback bound (EF bound) of the bit-interleaved coded modulation with iterative decoding (BICM-ID) for both perfect and imperfect CSI is developed. We show that asymptotically, the error floor generated due to imperfect CSI depends on the fading parameter and the power correlation coefficient between the fading coefficient and its estimate.

In this letter, we propose and compare some new rate-compatible serially concatenated convolutional code (SCCC) families. To obtain them, inner coded bits only are punctured. However, and this is the novelty proposed in the letter, the puncturing is not limited to inner parity bits, but extended also to inner systematic bits, thus obtaining high rate SCCCs (i.e., beyond the outer code rate). The two main applications of this technique are its use in hybrid Automatic-Repeat-reQuest/Forward-Error Correction (ARQ/FEC) schemes and to achieve unequal error protection (UEP) of an information sequence.

Concatenation is a method of building long codes out of shorter ones, it attempts to meet the problem of decoding complexity by breaking the required computation into manageable segments. Concatenated Continuous Phase Frequency Shift Keying (CPFSK) facilitates powerful error correction. CPFSK also has the advantage of being bandwidth efficient and compatible with non-linear amplifiers. Bandwidth efficient concatenated coded modulation schemes were designed for communication over Additive White Gaussian noise (AWGN), and Rayleigh fading channels. An analytical bounds on the performance of serial concatenated convolutional codes (SCCC), and parallel concatenated convolutionalcodes (PCCC), were derived as a base of comparison with the third category known as hybrid concatenated trellis codes scheme (HCTC). An upper bound to the average maximum-likelihood bit error probability of the three schemes were obtained. Design rules for the parallel, outer, and inner codes that maximize the interleaver's gain were discussed. Finally, a low complexity iterative decoding algorithm that yields a better performance is proposed.

We study the impact of imperfect channel state information (CSI) on the bit-error rate (BER) of QAM bit-interleaved coded modulation with iterative decoding (BICM-ID), in flat Rayleigh fading. The key parameter characterizing this effect is the power correlation coefficient /spl rho/ between the fading gain and its estimate. An accurate and efficient bound is developed to predict the asymptotic BER. We also show simulation results for QAM BICM-ID with 8-state and 16-state convolutional codes to provide the performance evaluation. For the 16-state code with modified set partitioning labeling and power correlation /spl rho/=0.95, a BER of 10/sup -6/ can be achieved at E/sub b//N/sub 0/=11 dB, with 4 passes of soft feedback. This corresponds to about 3.5 dB increase in the required E/sub b//N/sub 0/ compared to that of perfect CSI.

Cooperation is an effective technique to increase the diversity in wireless relay networks and hence improve the Bit Error Rate (BER). In this paper, a scheme combining turbo coding and cooperative relay techniques, comprising one source, one destination and a single relay is proposed and studied. The aim of this study is to investigate the bit error rate (BER) performance in cooperative turbo coded systems equipped with an omni-directional antenna element at the transmission and the reception in the presence of channel estimation errors. Herein, the Amplify-and-Forward (AF) cooperation protocol is adopted at the relay level. Furthermore, a single hop scenario is considered, and the imperfect channel state information (CSI) is assumed to be present at the source-destination link. Two turbo codes, are generated at the source using the same polynomial, with overall rates of 1/2 and 1/3, respectively, the 1/2-rated one being generated from the latter using puncturing. Before iterative decoding, the destination performs a maximum ratio combing (MRC) of the signals emanating from the source and the relay transmitters. According to the authors 'knowledge, the investigation of the effect of channel estimation errors on the performance of such systems has not yet been reported.

This letter investigates the bit error rate (BER) performance of orthogonal frequency division multiplexing index modulation, employing the maximal ratio combining-based low-complexity greedy detector (MRC-GD) and the PSK modulation. For performance analysis, we derive tight expressions for both index error probability (IEP) and BER, taking into account channel state information (CSI) uncertainty. This provides insight into various impacts of CSI uncertainty on the diversity gain and error floor of the IEP and the BER, respectively. We clearly show that under imperfect CSI, the MRC-aided GD can perform like the MRC-maximum likelihood detector, at lower complexity. Finally, simulation results are presented to verify the accuracy of derived expressions and the theoretical analysis.

We give an overview of iterative techniques for bit‐interleaved coded modulation. We start with simple methods where a convolutional code is concatenated with a standard QAM modulation scheme. The mapping is carefully chosen different from Gray mapping such that significant gains can be obtained by an iterative (turbo) receiver. The idea can also be applied to transmit antenna diversity as well as spatial multiplexing (MIMO). We then consider various powerful iterative coding schemes which are under discussion in standardisation for wireless systems beyond 3G such as serial or parallel concatenated convolutional codes, repeat accumulate codes and LDPC codes. We give a comparison in terms of complexity and performance.The main intention is to provide an illustrative overview over relevant applications of the turbo principle in demodulation and decoding. It is a summary of results which have been obtained in collaboration between the Institute of Communications Engineering, TUM and DoCoMo Euro‐Labs. Copyright © 2007 John Wiley & Sons, Ltd.