Turbo Trellis Coded Modulation Research Articles

Performance Improvement for Medical Image Transmission Systems using Turbo-Trellis Coded Modulation (TTCM)

Digital images have become an essential working tool in several areas such as the medical field, the satellite and astronomical field, film production, etc. The efficiency of a transmission system to exchange digital images is crucial to allow better and accurate reception. Generally, transmitted images are infected with noise. In the medical field, this noise makes the process of diagnosing difficult. To eliminate the transmission errors, an Error Correcting Code (ECC) can be used with the aim to guarantee excellent reception of the images and allowing a good diagnosis. In this paper, source and channel encoding/ decoding functions are studied during medical image transmission (LUNG). At first, the Turbo-Code (TC) is used as ECC and subsequently the Turbo-Trellis Coded Modulation (TTCM). The simulation results represent the curves giving the Bit Error Rate (BER) as a function of the signal to noise ratio (Eb/N0). In order to compare these two systems properly, the MSSIM (Mean Structural Similarity) parameter was used. The obtained results showed the effect and importance of ECC on the transmission of medical images using TTCM which gave better results compared to TC with regard to increasing the performance of the transmission system by eliminating transmission noise.

Higher performance and lower complexity turbo decoding scheme for 4G-LTE using unpunctured turbo trellis-coded modulation

<p>Thanks to the success of smart phones and mobile-ready laptops, data traffic has recently grown exponentially, and the demand for mobile data has risen very dramatically. These requests in large capacity can only be satisfied by a high efficiency and a very good optimization of the infrastructures of the mobile networks, while taking into account the constraints which are the power, bandwidth and a limited complexity. The task of developing mobile technologies has also evolved from a national or regional focus to a complex and growing mission, supported by global standards development organizations such as 3GPP (3rd Group Partnership Project). Through this research, we present everything related to the simulation of the 4G mobile network system (LTE), which can provide high data flow with good quality, through three model channels known as (EPA, EVA, ETU). In this work we focus on the block ‘iterative decoding channel encoder’ in the LTE system, where the iterative channel coding called ‘Turbo-code’ (TC) is substituted by the iterative coding channel called ‘Unpunctured Turbo Trellis-coded Modulation’ (UTTCM). The simulation results showed that with less decoding complexities, UTTCM's LTE system gives good performance (in terms of BER).</p>

Distributed Joint Source-Channel Coding-Based Adaptive Dynamic Network Coding

Distributed Source Coding (DSC) schemes rely on separate encoding but joint decoding of statistically dependent sources, which exhibit correlation. More specifically, Distributed Joint Source-Channel coding (DJSC) is associated with the scenario, where the correlated source signals are transmitted through a noisy channel. On one hand, employing DSC or DJSC schemes exploits the existing correlation between sensors resulting in minimising the transmission energy required by the sources, while maintaining reliable communication. On the other hand, Network Coding (NC) is an efficient data transport technique leveraging network efficiency, by allowing Relay Nodes (RNs) in a communication network to combine multiple data packets received via the incoming links before transmitting them to the Destination Node (DN). In this paper, the bandwidth-efficient Distributed Joint Turbo Trellis-Coded Modulation (DJTTCM) aided by both Dynamic Network Coding (DNC) and Adaptive DNC (ADNC)-based cooperative transmission schemes are proposed. Both systems are proposed for supporting correlated source transmissions over hostile channels experiencing both small-scale and large-scale fading in which the RNs dynamically transmit its non-binary linear combinations to the DN. A substantial gain of 19.5 dB was attained at a correlation coefficient of $\rho = 0.8$ over its counterpart dispensing with NC.

Performance analysis of the odd–even uniform interleaver for turbo codes

Interleaver design has been an intense research area since the invention of turbo codes, both from theoretical and technological perspectives, still receiving the attention of engineers. This work is a theoretical treatment on the subject of interleaver design, bringing into focus the odd-even constraint. Odd-even interleavers constrain information symbols at odd (even) positions to remain at odd (even) positions after interleaving. Having been adopted in a range of operational communication standards as parts of turbo codes on the one hand, and having raised scepticism about their gain in the literature of turbo trellis-coded modulation on the other hand, these interleavers have motivated the present article. Concretely, the authors perform a bit-error analysis of turbo-code ensembles generated by the odd–even uniform interleaver , following the union-bound approach by Benedetto et al. for the analysis of the uniform interleaver. They find that the odd–even constraint does not affect the interleaver gain of uniform-interleaver ensembles; rather, it triggers a redistribution of multiplicities that leads to slightly worse performance mainly in the error-floor region. The authors' findings are corroborated by bit-error-rate simulations.

Convergence analysis of the unpunctured turbo trellis-coded modulation (UTTCM)

In this paper, the performance of the Unpunctured Turbo Trellis-Coded Modulation (UTTCM) over Additive White Gaussian Noise (AWGN) channel is analyzed using the non-binary extrinsic information transfer (EXIT) chart. The exchange of the extrinsic information between the decoder components is tracked, allowing the generation of an EXIT chart, which is a powerful tool for analyzing the convergence behavior of iterative decoding and prediction of convergence position. The Simulation results are compared with the turbo cliff positions on the BER curves.

Turbo Trellis-Coded Differential Chaotic Modulation

In this brief, a novel turbo trellis-coded differential chaotic modulation (TTC-DCM) system is proposed, where parallel concatenated trellis codes are combined with the M-ary differential chaotic shift keying (M-ary DCSK) scheme. An extrinsic information transfer chart is employed to analyze the convergence over additive white Gaussian noise channel and multipath Rayleigh channels. Simulation results show that the new scheme can obtain considerable coding gains without impairing the bandwidth efficiency in comparison with the M-ary DCSK scheme and the trellis-coded differential chaotic modulation scheme. Moreover, compared to the direct-sequence spread-spectrum turbo trellis-coded modulation scheme, TTCDCM has lower complexity and better robustness in the absence of channel state information over multipath Rayleigh channels. Overall, because of the merits of promising performance, high bandwidth efficiency, robustness to poor channel conditions, and an easy-to-implement property, the TTC-DCM scheme is suitable for bandlimited communication applications under poor channel conditions.

Four-Dimensional Trellis Coded Modulation for Flexible Optical Communications

We experimentally investigate four-dimensional (4­D) Trellis coded modulation (TCM) based on polarization-division multiplexed (PDM) 16-ary quadrature amplitude modulation (QAM), PDM-32QAM, and PDM-64QAM formats. A multirate optical transponder is enabled by only a single-encoder/decoder structure. The scheme is resilient to cycle-slip events due to its 90° phase rotation invariant property. In addition, the performance of 4-D turbo TCM (TTCM) is investigated. The superior performance of TTCM over TCM is experimentally validated. Furthermore, the performance of 4-D TCM/TTCM is compared with standard PDM- m QAM formats combined with the soft-decision (SD) forward error correction (FEC) codes. It is shown that 4-D TCM concatenated with a low-complexity hard-decision FEC could be an interesting candidate for complexity-performance tradeoff with SD-FEC.

An Experimental Comparison of Coded Modulation Strategies for 100 Gb/s Transceivers

Coded modulation is a key technique to increase the spectral efficiency of coherent optical communication systems. Two popular strategies for coded modulation are turbo trellis-coded modulation (TTCM) and bit-interleaved coded modulation (BICM) based on low-density parity-check (LDPC) codes. Although BICM LDPC is suboptimal, its simplicity makes it very popular in practice. In this work, we compare the performance of TTCM and BICM LDPC using information-theoretic measures. Our information-theoretic results show that for the same overhead and modulation format only a very small penalty (less than 0.1 dB) is to be expected when an ideal BICM LDPC scheme is used. However, the results obtained for the coded modulation schemes implemented in this paper show that the TTCM outperforms BICM LDPC by a larger margin. For a 1000 km transmission at 100 Gbit/s, the observed gain was 0.4 dB.

Distributed Source–Channel Coding Using Reduced-Complexity Syndrome-Based TTCM

In the context of distributed joint source–channel coding, we conceive reduced-complexity turbo trellis coded modulation (TTCM)-aided syndrome-based block decoding for estimating the cross-over probability $p_{e}$ of the binary symmetric channel, which models the correlation between a pair of sources. Our joint decoder achieves an accurate correlation estimation for varying correlation coefficients at 3 dB lower SNR, than conventional TTCM decoder, despite its considerable complexity reduction.

Distributed Source Coding and Its Applications in Relaying-Based Transmission

Distributed source coding (DSC) schemes rely on separate encoding but joint decoding of statistically dependent sources, which exhibit correlation. DSC has numerous promising applications ranging from reduced-complexity handheld video communications to onboard hyperspectral image coding under computational limitations. The concept of separate encoding at the first sight compromises the attainable encoding performance. However, the DSC theory proves that independent encoding can in fact be designed as efficiently as joint encoding, as long as joint decoding is allowed. More specifically, distributed joint source-channel coding (DJSC) is associated with the scenario, where the correlated source signals are transmitted through a noisy channel. In this paper, we present a concise historic background of DSC concerning both its theory and its practical aspects. In addition, a series of turbo trellis-coded modulation (TTCM)-aided DJSC-based cooperative transmission schemes are proposed. DJSC scheme is conceived for the transmission of a pair of correlated sources to a destination node (DN). The first source sequence is TTCM encoded, and then, it is compressed before it is transmitted both over a Rayleigh fading channel, where the second source signal is assumed to be perfectly decoded side-information at the DN for the sake of improving the achievable decoding performance of the first source. The proposed scheme is capable of performing reliable communications for various levels of correlation near to the theoretical Slepian–Wolf/Shannon (SW/S) limit. Pursuing our objective of designing practical DJSC schemes, we further extended the above-mentioned arrangement to a more realistic cooperative communication system, where the pair of correlated sources are transmitted to a DN with the aid of a relay node (RN). Explicitly, the pair of correlated source sequences are TTCM encoded and compressed before transmission over a Rayleigh fading multiple access channel, where our proposed scheme is capable of operating within 0.55 dB from the SW/S limit for a correlation coefficient value of $\rho = 0.8$ , and within 0.07 bits of the minimum SW compression rate. The RN transmits both users’ signal with the aid of a powerful superposition modulation technique that judiciously allocates the transmit power between the two signals. The correlation is beneficially exploited at both the RN and the DN using our powerful iterative joint decoder, which is optimized using extrinsic information transfer characteristics charts.

Turbo Trellis-Coded Hierarchical-Modulation Assisted Decode-and-Forward Cooperation

Hierarchical modulation (HM), which is also known as layered modulation, has been widely adopted across the telecommunication industry. Its strict backward compatibility with single-layer modems and its low complexity facilitate the seamless upgrading of wireless communication services. The potential employment of HM in cooperative communications has the promise of increasing the achievable throughput at low power consumption. In this paper, we propose a single-relay-aided hierarchical-modulation-based cooperative communication system. The source employs a pair of turbo trellis-coded modulation (TTCM) schemes relying on specially designed HM, whereas the relay invokes the decode-and-forward (DAF) protocol. We have analyzed the system's achievable rate, as well as its bit error ratio (BER), using Monte Carlo simulations. The results demonstrate that the power consumption of the entire system is reduced to 3.62 dB per time slot (TS) by our scheme.

A High Spectral Efficient Non-Binary TTCM-assisted G2 STBC-OFDM for 4G Systems

paper deals with the MIMO-OFDM technique that candidate with the fourth generation (4G) of the wireless communication systems, this technique can provide high data rate transmission without increasing transmit power and expanding bandwidth, also it can efficiently use space resources and has a bright future. This paper presents the channel coding assisted STBC-OFDM systems, and employs the Coded Modulation techniques (CM), since the signal bandwidth available for wireless communications is limited. Furthermore, a non-binary Turbo Trellis Coded Modulation (TTCM) decoder-based multidimensional MAP algorithm- assisted G2 STBC-OFDM is design and implemented. The idea of Non-binary codes has been extended for symbols defined over rings of integers, which outperform binary codes with only a small increase in decoding complexity. The simulation results show that the performance of the TTCM decoding algorithm outperforms the binary decoding methods and suitable to deal with error control coding of the STBC- OFDM schemes. Keywordscodes, TTCM, non-binary error correcting codes, Rings

Pragmatic Distributed Algorithm for Spectral Access in Cooperative Cognitive Radio Networks

A pragmatic distributed algorithm (PDA) is proposed for supporting the efficient spectral access of multiple Primary Users (PUs) and Cognitive Users (CUs) in cooperative Cognitive Radio (CR) networks. The novelty of our PDA is that the PUs negotiate with the CUs concerning the specific amount of relaying and transmission time, the CU is granted, which the CU will either accept or decline. The CUs may serve as relay nodes for relaying the signal received from the PUs to their destinations, while both the PUs' and the CUs' minimum rate requirements are satisfied. This will reduce the required transmission power and/or increase the transmission rate of the PU. Our results show that the proposed scheme performs better than the benchmarker, despite its significantly lower overhead and complexity. Moreover, we show that the cooperative spectral access based on our PDA reaches an equilibrium, when it is repeated for a sufficiently long duration. These benefits are achieved, because the PUs are motivated to cooperate by the incentive of achieving a higher PU rate, whilst non-cooperation can be discouraged with the aid of a limited-duration punishment. Furthermore, we invoke an attractive practical adaptive Turbo Trellis Coded Modulation (ATTCM) scheme, which appropriately adjusts the code rate and the modulation mode according to the near-instantaneous channel conditions. It was found that the joint design of coding, modulation and user-cooperation may lead to significant mutual benefits for all the PUs and the CUs.

시간 선택적 페이딩 채널 환경에서 DPSAM Turbo TCM에 관한 연구

스마트 미디어 시대에 대용량 데이터 서비스가 필수적이고 모바일 이동성과 데이터 신뢰성이 보장되어야 한다. 고속 데이터의 신뢰성을 높이기 위해서는 강력한 채널 코딩 방식 및 변조 기술이 요구되고 있다. 본 논문에서는 최적 복호 방법, 반복 복호를 통하여 부호화 이득이 우수한 Turbo Codes에 대역폭 효율을 증대시키기 위한 고차 변조기술을 적용한 Turbo TCM 복호기의 구조를 제시하고 시간 선택적 페이딩 채널 환경에서 연집에러 발생 시 성능을 향상시키는 DPSAM 방식에 대해 제안하다. 제안된 방식은 기존의 방식과 비교해서 BER이 <TEX>$10^{-2}$</TEX>이고 반복 복호수가 3인 경우 약 3dB 우수하고 BER이 <TEX>$10^{-3}$</TEX>이고 반복 복호수가 7인 경우 약 6dB 성능 개선을 보인다. 제안된 방식은 추가 대역폭이 필요하지만 대역폭 손실에서 발생하는 부가 비트율에 대해 Turbo TCM 기술로 대역폭 손실을 극복할 수 있다. Mobile mobility and data reliability should be guaranteed as well as amounts of data services are essential in the era of smart media. In order to improve the reliability of high-speed data, strong channel coding and modulation techniques are required. In this paper, the structure of Turbo TCM decoder, applying high-order modulation techniques and the DPSAM method which improves performances in time-selective fading channels in the case of burst errors are suggested through the optimal decoding method and iteration decoding so as to improve bandwidth efficiency in Turbo Codes with excellent encoding gain. The proposed method in comparison with the existing method is that 3dB is superior in case that BER is <TEX>$10^{-2}$</TEX> and the number of iterations is 3. In addition, the function is improved at approximately 6dB in case that BER is <TEX>$10^{-3}$</TEX> and the number of iterations is 7. The proposed method requires additional bandwidth; however, the bandwidth loss can be overcome through Turbo TCM technology on the additional bit rate from the bandwidth loss.

A Low Complexity Implementation in Hardware on Simplified Log-MAP Algorithm for T-TCM Decoding

A simplified decoding algorithm for turbo trellis-coded modulation (T-TCM) is proposed, which is easy to implement in hardware. The algorithm exploits a new piece-wise function to replace the logarithmic term of the Jacobian logarithm based on the MacLaurin Series. Simulation results show that the proposed algorithm can archive log-MAP-similar decoding performance with a much lower computational complexity. It can reduce about 40% of calculation in contrast to the improved MAX-Log-MAP.

Reduced complexity Log-MAP algorithm with Jensen inequality based non-recursive max∗ operator for turbo TCM decoding

In this paper, a reduced complexity Log-MAP algorithm based on a non-recursive approximation of the max∗ operator is presented and studied for turbo trellis-coded modulation (TTCM) systems. In the algorithm, denoted as AvN Log-MAP, the max∗ operation is generalized and performed on n≥2 arguments. The approximation is derived from the Jensen inequality. The non-recursive form of the max∗ calculations allows to achieve significant reduction in the decoding effort in comparison to the conventional Log-MAP algorithm. Bit-error rate performance simulation results for serial and parallel TTCM schemes in the additive white Gaussian noise and uncorrelated Rayleigh fading channels show that the AvN Log-MAP algorithm performs close to the Log-MAP. Performance and complexity comparisons of the AvN Log-MAP algorithm against the Log-MAP and several relevant reduced complexity turbo decoding algorithms proposed in the literature reveal, that it offers favorable low computational effort for the price of small performance degradation.

Reduced-Complexity Syndrome-Based TTCM Decoding

The iterative decoder of Turbo Trellis Coded Modulation (TTCM) exchanges extrinsic information between the constituent TCM decoders, which imposes a high computational complexity at the receiver. Therefore we conceive the syndrome-based block decoding of TTCM, which is capable of reducing the decoding complexity by disabling the decoder, when syndrome becomes zero. Quantitatively, we demonstrate that a decoding complexity reduction of at least 17% is attained at high SNRs, with at least 20% and 45% reduction in the 5^{th} and 6^{th} iterations, respectively.

Evaluation of the Effects of Co-Channel Interference on the Bit Error Rate of Wireless Networks with Error Correcting Codes in Fading Channels

This paper presents a performance analysis of wireless networks using error correcting codes on channels with Rayleigh fading in the presence of co-channel interference. The performance is evaluated in terms of the average bit error rate (BER) using TCM (Trellis-Coded Modulation) and TTCM (Turbo Trellis-Coded Modulation) schemes for QAM modulations. The effects of co-channel interference are evaluated through Monte Carlo simulation in scenarios where the system is affected by a dominant interfering synchronous and similar to the target user. For each coded-modulation schemes, the results show that there are BER floors, which vary according to the signal-interference (S/I).

Improved MIMO Turbo-Trellis Coded Modulation Under Channel Estimation Errors

Turbo-trellis coded modulation (TTCM) schemes are designed for reliable transmission over quasi-static fading channels. Assuming pilot-assisted channel estimation, practical limitations in power and the number of pilot symbols lead to imperfect channel estimates. A general method for robust multiple-input multiple-output (MIMO) receiver design under channel estimation errors was recently proposed by Sadough et al.. Here, this technique is applied to improve the performance of MIMO-TTCM receivers under channel estimation errors in quasi-static fading channels where the TTCM scheme is commonly used. We compare our proposed reception method to the conventional mismatched receiver in terms of bit error rate and extrinsic information transfer chart analysis. Our results confirm the adequacy of the proposed receiver for improving MIMO-TTCM iterative decoding in situations where only an imperfect channel estimate is available at the receiver.

Design of unpunctured turbo trellis-coded modulation

In this paper, the design of newly introduced turbo encoding scheme called ‘Unpunctured Turbo Trellis-Coded Modulation’ (UTTCM) is exposed. The performance improvement of this encoding scheme is obtained by setting a design criterion for each of its components namely: the search rules of best constituent encoders’ generator polynomials, the constellation and the associated mapping. Simulation results show that the optimized UTTCM outperforms TTCM and PCTCM for all considered spectral efficiencies, and presents competitive error floors. As examples, for a spectral efficiency of 3bits/symbol (bps), UTTCM with 8 decoding iterations outperforms TTCM by 0.05dB at BER=10−4; and for a spectral efficiency of 4bps and 6 decoding iterations, UTTCM outperforms Fragouli's PCTCM by 0.07dB at BER=10−5.