Coded modulation assisted iterative parallel interference cancellation aided CDMA

Space-time block coded (STBC) in-phase quadrature-phase (IQ)-interleaved coded modulation (CM) schemes are proposed for orthogonal frequency division multiplexing (OFDM). Trellis coded modulation (TCM), turbo TCM (TTCM), bit-interleaved coded modulation (BICM) and iteratively decoded BICM (BICM-ID) schemes having a similar decoding complexity are employed in conjunction with 16-level quadrature amplitude modulation (16QAM) for yielding an effective throughput of 3 information bits per symbol. The IQ-diversity attained by the proposed schemes provides a significant additional coding gain. It was found that TTCM and BICM-ID assisted STBC-IQ-OFDM were the best schemes in terms of the achievable bit error ratio and frame error ratio, respectively.

In this paper, we have proposed a bandwidth efficient turbo trellis-coded modulation scheme for the non-coherent multiple-antenna Rayleigh fading channel, where the channel state information (CSI) is not necessary both at the transmitter and the receiver. In this scheme, we merge the unitary space-time modulation (USTM) as constellations with the turbo trellis-coded modulation, resulting in the turbo trellis-coded USTM (TTC-USTM), with the trellis-coded USTM encoder as the component encoders. We have also derived the iterative maximum a posteriori (MAP) algorithm. Through computer simulations, we demonstrated that without bandwidth expansion, TTC-USTM produces significant coding gains over its uncoded counterparts.

Bandwidth efficient parallel-concatenated turbo trellis coded modulation (TTCM) schemes were designed for communicating over uncorrelated Rayleigh fading channels. A symbol-based union bound was derived for analysing the error floor of the proposed TTCM schemes. A pair of in-phase (I) and quadrature-phase (Q) interleavers were employed for interleaving the I and Q components of the TTCM coded symbols, in order to attain an increased diversity gain. The decoding convergence of the IQ-TTCM schemes was analysed using symbol-based extrinsic information transfer (EXIT) charts. The best TTCM component codes were selected with the aid of both the symbol-based union bound and non-binary EXIT charts for the sake of designing capacity-approaching IQ-TTCM schemes in the context of 8 PSK, 16 QAM and 32 QAM signal sets. It will be shown that our TTCM design is capable of approaching the channel capacity within 0.5 dB at a throughput of 4 bit/s/Hz, when communicating over uncorrelated Rayleigh fading channels using 32 QAM.

We present an improved channel equalizing scheme to be used in Coded OFDM systems over an ISI channel. The scheme uses Turbo Trellis Coded Modulation (TTCM) which retains a powerful error correction capability while elegantly incorporating turbo coding into the Trellis Coded Modulation (TCM). In OFDM over wireless communications, M-ary Quadrature Amplitude Modulation (M-QAM) schemes have been widely used to achieve high bandwidth efficiency. However, M-QAM signals require linear amplification to avoid spectral regrowth and severe performance degradation due to their large envelope fluctuations. Moreover, the OFDM transmitter shapes the signal with a linear pulse shaping filter. The combination of a linear filter with a High Power Amplifier (HPA) forms a nonlinear system with memory, which severely degrades performance. We propose an efficient one-tap-equalizer using a modified LMS algorithm and a novel adaptive predistortion technique to compensate for the nonlinear distortion caused by the high power amplifier cascaded with a linear filter in TTCM-OFDM systems. The performance of this method is compared with methods that have been used previously with OFDM. A computer simulation confirms that the proposed approach is superior to the conventional methods.

The first VLSI implementation of a decoder for multiple-signal (pragmatic) trellis-coded modulation (TCM) is described. Integrated on the same device is an encoder and a decoder for a variable rate binary code. The IC discussed is a 64-state rate 2/3 or 3/4 (used in conjunction with 8 and 16 PSK modulation) TCM decoder. The decoder is also accompanied by a K=7 trellis encoder. Integrated on the TCM decoder is a variable-rate Viterbi decoder (rates 1/2, 3/4, 7/8, 1/3). The chip has been manufactured and tested. The performance in rate 2/3 8 PSK and rate 3/4 16 PSK is shown graphically. Included in each figure is the uncoded performance in addition to the simulated and measured data of the chip. The performance of the chip in the rest of the models is shown. The die size is 320 mils on a side. The device contains 17800 transistors and was fabricated in a state-of-the art 1.0 mu m process. The device has attained clock speeds above 30 MHz under nominal conditions. The power consumption at 10 Mbit/s is less than 0.75 W. >

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 bit-rate video coding techniques using the H.26L standard codec for robust transmission in mobile multimedia environments are presented. For the sake of achieving error resilience, the source codec has to make provisions for error detection, resynchronization and error concealment. Thus a packetization technique invoking adaptive bit-rate control was used in conjunction with the various modulation scheme employed. In this contribution, we propose a burst-by-burst adaptive coded modulation-aided joint detection-based CDMA (ACM-JD-CDMA) scheme for wireless video telephony and characterise its performance when communicating over the UTRA wideband vehicular fading channels. The coded modulation schemes invoked in our fixed modulation mode based systems are low density parity check code based block coded modulation (LDPC-BCM) and turbo trellis coded modulation (TTCM). The performance of LDPC-BCM was evaluated and compared to that of TTCM in the context of the ACM-JD-CDMA system using a practical modem mode switching regime. Both schemes exhibited a similar transmission integrity, although the LDPC arrangement is capable of achieving this at a lower complexity.

Turbo trellis-coded modulation (TCM) with code matched interleaver (CMI) is applied to develop a trellis coded quantization (TCQ). It can been shown that TCQ of memoryless Gaussian sources results in substantial improvement of performance with iterative decoding of turbo TCM and iterative optimization of minimum overall distortion between the source input and decoding output. Numerical results indicate substantial improvement of performance because optimal TCQ based on turbo TCM can be achieved at moderate to high signal-to-noise ratio (SNR) on an additive white Gaussian noise (AWGN) channel for a memoryless Gaussian source and a memoryless uniform source.

An optimal MAP equivalent SOVA decoding algorithm and its simplified suboptimal algorithm for non-binary codes are proposed. The implementation of its suboptimal algorithm is simpler, while its performance is very close to the optimal log-MAP algorithm. The proposed SOVA can be used as a decoder for turbo trellis coded modulation (TTCM). Simulation results for both the proposed SOVA and the log-MAP algorithms for TTCM and binary turbo codes are presented. It is concluded that the proposed SOVA performs very close to the log-MAP algorithm for both the TTCM and binary turbo codes, and its performance is better than the conventional SOVA.

Turbo trellis coded modulation (TTCM) invented by Patrick Robertson adapted the bandwidth efficiency of TCM and iterative decoding of turbo codes and presented better performance without bandwidth expansion [P. Robertson et al., 1996]. But TTCM has a difficulty of implementing a hardware owing to decoder complexity. So, we need efficient scheduling and date storage management. In order to solve this essential problem, we propose a novel TTCM decoder using sliding window technique by using trace back technique, which is popular for realizing long path memories for Virterbi decoders [A.J. Viterbi, Feb. 1998].

Unitary (USTM) has got more attention for its potential in implementing high data rate transmission in a noncoherent multiple-antenna Rayleigh flat fading channel. In this paper, we have given out a bandwidth efficient turbo trellis-coded modulation scheme for the non-coherent multiple-antenna Rayleigh fading channel, where the channel state information (CSI) is not necessary both at the transmitter and the receiver. In this proposal, we combine USTM as constellations with the turbo trellis-coded modulation, resulting in the turbo trellis-coded USTM (TTC-USTM), with the trellis-coded USTM encoder as the component encoders. We have also applied the iterative maximum a posteriori (MAP) algorithm. According to PC simulations, we demonstrated that without bandwidth expansion, TTC-USTM produces obvious coding gains over its uncoded counterparts.

Turbo trellis coded modulation (TTCM) has been widely used as a channel coding scheme that achieves nearcapacity rate without sacrificing bandwidth. Traditionally, linear trellis codes are used as the constituent encoders in the design of TTCM schemes. In this paper we design nonlinear trellis codes that outperform previously designed code over AWGN and fullyinterleaved Rayleigh fading channels.

This paper proposes a novel approach for the implementation of Distributed Video coding (DVC) using 4-PSK turbo trellis coded modulation (TTCM). We have adapted the TTCM concept for source coding by generating parity at the encoder and transferring the symbol mapping to the decoder. The parity bits are sent to the decoder with puncturing as in a turbo based DVC codecs and combined with side information to form the symbols used in the TTCM decoder. The side information is generated by basic frame interpolation. The proposed codec was tested with different test video sequences and the results obtained show up to 6dB improvement in PSNR with less memory for the same bit rate when compared with the turbo coding based DVC codecs.

The classical turbo decoding algorithm is based on the use of binary waveform disturbed by a Gaussian distributed noise. Although a significant amount of coding gain can be achieved, binary turbo codes do not have good bandwidth efficiency unless they are heavily punctured. Turbo trellis coded modulation (TTCM) can provide good turbo code performance without bandwidth expansion. However, it requires unique code design. The simplest way to attain both power and bandwidth efficiency is to adopt high-order modulation schemes with a commonly studied binary turbo code. This approach requires a conversion of the demodulator output associated with the nonbinary channel symbol into bit metrics to input to the binary turbo decoder. This paper investigates various conversion functions for M-ary PSK and M-ary QAM constellations. The turbocoded bit-error-rate performances are compared using these metrics. It is shown that the likelihood metric, which is the optimum for the uncoded case, does not provide the optimum performance in the coded case. This paper also indicates that this turbo-coded waveform can perform as well as TTCM

In this paper, a new turbo trellis coded modulation (T-TCM) scheme is proposed for 8-PSK modulation. A belief propagation algorithm is used for T-TCM decoding. Bit and symbol interleaving techniques are considered for the T-TCM scheme and it is concluded that the symbol interleaved scheme provides better error performance. It is also shown by computer simulations that the distance distribution of the output symbol sequences for the two-weight inputs is improved when primitive feedback polynomials are selected for the constituent encoders instead of nonprimitive ones. Factors that determine performance at high signal to noise ratio are stated. If constituent encoders which maximize the output distances for two- and three-weight inputs are selected, those with maximum effective free distance with minimum multiplicity among them will provide the best error performance. From this issue, a new 8-state punctured T-TCM code for 8-PSK is designed and it is shown by computer simulations that it performs better especially at high SNR ratios with half decoding complexity, compared to the corresponding codes given in the literature.