Optimization of sliding window algorithm for space-time turbo trellis codes

Motivated by the remarkable performance of turbo codes, the design of space-time turbo trellis coded modulation (ST turbo TCM), which is based on the turbo structure, has been proposed in the literature. However, like other turbo based coding schemes, its complexity and decoding latency are drawbacks making them unattractive for time sensitive applications. To achieve memory savings and reduce decoding latency, we propose a simplified ST turbo TCM decoder using sliding window technique. In particular, the performance of QPSK ST turbo TCM schemes on slow flat Rayleigh fading channels for various system parameters are considered. Based on simulation results, optimum sliding window sizes will be given for different configurations

We consider the design of 16-QAM space-time trellis codes (STTCs) for quasi-static Rayleigh flat fading channels. Based on the /spl Sigma//sub o/-rank criterion and the trace criterion, new 16-state and 64-state 16-QAM STTCs were constructed. The performance of the codes was evaluated by simulation. It is shown that the new 16-state code outperforms the previous hand-designed codes by about 1 dB.

Space-time coding has been proposed recently for MIMO wireless communication systems. Most of these space-time coding schemes use the assumption that either no channel state information, or the channel mean/covariance information, is available at the transmitter. We propose a new space-time coding scheme for a close-loop transmission system, where quantized channel phase information is available at the transmitter. A new performance criterion is derived for the quasi-static fading channel. This design criterion is then used to construct a new class of space-time trellis codes. The proposed code construction is based on the concatenation of a standard M-TCM outer code with an inner code. The inner code is selected from a series of inner codes using the channel phase feedback. The series of inner codes is constructed based on the systematic set partitioning of two classes of space-time signal designs. Simulation results show significant improvement over other space-time trellis codes. In addition, the proposed coding scheme enjoys low peak-to-average power ratio, simple decoding, and easy implementation without complicated eigenanalysis.

Impulsive, non-Gaussian noise is prevalent in wireless environments. We adopt an impulsive noise model over multi-input-multi-output (MIMO) channels and discuss receiver and code design over fading channels with impulsive noise. We derive code design criteria for the so-called genie-aided, and minimum distance receivers, both of which yield criteria identical to the nonimpulsive, Gaussian noise case. We also study the performance of certain space-time block codes (STBCs) and space-time trellis codes (STTC) over impulsive noise channels with the genie-aided receiver (GAR) and minimum distance receiver (MDR). The performance loss incurred by the impulsive nature of the noise is shown to increase with the diversity order for the MDR. To approximate the good performance of the practically unrealistic GAR, we propose a maximum a posteriori (MAP) receiver, whose performance can be tightly lower bounded by the GAR. We simplify the optimal MAP receiver by an approximation and show that for alt cases of practical interest, only 2 terms in the approximation are sufficient to get a near-MAP performance. Simulations corroborate our analytical findings

We propose a new family of space-time trellis codes, which are constructed by combining a super set of QOSTBC with minimum decoding complexity and an outer MTCM encoder. A systematic set-partitioning method for QAM constellations is given. The proposed scheme can be used for systems with four and more than four transmit antennas. Furthermore, its decoding complexity is low because branch metric calculations can be done in a symbol-wise way. Several design examples are presented. Simulation results demonstrate that the proposed scheme has a comparable performance as super quasi-orthogonal space-time trellis codes presented by Jafarkhani and Hassanpour while providing a lower decoding complexity

Space-time block codes and space-time trellis codes have recently been introduced to improve the performance of wireless systems. In this paper, we reconsider first the design criteria for space-time trellis codes in our context of application that is OFDM-based WLAN. We show by simulations that the rapid Rayleigh fast fading criteria are appropriate and we propose a code optimized accordingly. Then, we compare space-time block coding solutions with trellis-based ones, both including convolutional coding and interleaving. For that purpose, we also designed and simulated a rate 1/2 space-time trellis code, in which the channel and space-time coding are jointly optimized.

The potential for capacity increase in multiple-antenna wireless communication systems has drawn considerable attention to space-time codes. However, most of the existing space-time code construction methods have assumed ideal channel models: either quasi-static fading or fast fading. In this work, we propose a systematic space-time trellis code construction method for correlated fading channels. We derive the performance criteria that take into account both spatial and temporal channel correlation, assuming that the space-time correlation matrix is of full rank. Moreover, we introduce a new design criterion and analyze the properties of the space-time trellis codes satisfying the proposed criterion. Using the design criterion, we develop a code construction procedure that jointly considers diversity advantage and coding advantage for an arbitrary number of transmit antennas and any memoryless modulation. The flexibility of the proposed code construction method is demonstrated by designing space-time trellis codes for two, three, and four transmit antennas with quaternary phase-shift keying (QPSK), 8PSK (phase-shift keying), and 4ASK (amplitude-shift keying) modulations. The simulation results demonstrate that not only can our method generate new codes for an arbitrary number of antennas, but in some special cases, where previously proposed codes exist, our codes also perform very well.

In this paper, Beam Pattern Scanning (BPS), a transmit diversity technique, is compared with two well known transmit diversity techniques, space-time block coding (STBC) and space-time trellis coding (STTC). In BPS (also called beam pattern oscillation), controlled time varying weight vectors are applied to the antenna array elements mounted at the base station (BS). This creates a small movement in the antenna array pattern directed toward the desired user. In rich scattering environments, this small beam pattern movement creates an artificial fast fading channel. The receiver is designed to exploit time diversity benefits of the fast fading channel. Via the application of simple combining techniques, BPS improves the probability-of-error performance and network capacity with minimal cost and complexity. In this work, to highlight the potential of the BPS, we compare BPS and Space-Time Coding (i.e., STBC and STTC) schemes. The comparisons are in terms of their complexity, system physical dimension, network capacity, probability-of-error performance, and spectrum efficiency. It is shown that BPS leads to higher network capacity and performance with a smaller antenna dimension and complexity with minimal loss in spectrum efficiency. This identifies BPS as a promising scheme for future wireless communications with smart antennas.

수중통신에서는 다중경로로 인해 심벌간의 상호간섭이 발생하여 시스템의 성능을 저하시킨다. 최근 수중 통신시스템에서는 이러한 열악한 채널환경을 극복하고 전송률을 향상시키기 위하여 등화기 및 채널 부호화와 시공간 부호화 방식의 효율적인 연접 구조가 수중통신에서 MIMO시스템으로 응용되어 연구되고 있다. 수중 MIMO 환경에서 시공간 부호화 방식 중에서는 시공간 블록 부호화 방식과 시공간 격자 부호화 방식이 있으며, 시공간 격자 부호화 방식이 등화기 및 채널 부호화 방식에 최적이다. 따라서 본 논문에서는 다중경로 채널 환경에서 효율적인 전송을 위해 터보 Pi 부호화기를 외부부호로 사용하고, MIMO시스템에서 전송 다이버시티와 부호화이득을 동시에 가지는 시공간 격자부호를 내부부호로 구성한다. 그리고 심볼간 상호 간섭 제거를 위해 Zero Forcing 등화기법을 사용하여 수중채널에서의 시뮬레이션을 통해 성능을 확인하였다. In the underwater communication, the performance of system is reduced because of the inter-symbol interference occur by the multi-path. In the recent years, to deal with poor channel environment and improve the throughput, the efficient concatenated structure of equalization, channel codes and Space Time Codes has been studied as MIMO system in the underwater communication. Space Time Codes include Space Time Block Codes and Space Time Trellis Codes in underwater communication. Space Time Trellis Codes are optimum for equalization and channel codes among the Space Time Codes to apply in the MIMO environment. Therefore, in this paper, turbo pi codes are used for the outer code to efficiently transmit in the multi-path channel environment. The inner codes consist of Space Time Trellis Codes with transmission diversity and coding gain in the MIMO system. And Zero Forcing method is used to remove inter-symbol interference. Finally, the performance of this model is simulated in the underwater channel.

In this letter, space time (ST) trellis codes are developed for systems with an arbitrary number of receiver antennas in quasi-static fading channels applying M-ary continuous phase frequency shift keying (CPFSK) modulation with M = 4 and 8 for h = 1/M. The maximizing minimum squared Euclidean distance criterion (MMSEDC) is applied in the code search algorithm when obtaining the ST codes. The results show that a significant performance gain can be obtained by using the ST codes from the MMSEDC code search algorithm compared to the ST codes obtained in X. Zhang and M.P. Fits (2003) for CPFSK modulation systems

The problem of designing codes with close-to-capacity performance on the multiple-input multiple-output (MIMO) quasi-static fading channel (QSFC) is addressed. We consider three different coding schemes - namely, direct transmission of random-like codes, concatenation with linear processing orthogonal space-time block codes (o-STBC) and concatenation with space-time trellis codes (STTC). The constrained modulation outage capacity of each of these schemes is computed. It is shown how low-density parity check (LDPC) codes may be used to approach capacity in these cases. For the STTC, the serial concatenation scheme of Gulati et al. (2001) turns out to have close to capacity performance.

The achievable performance of channel coded space-time trellis (STT) codes and space-time block (STB) codes transmitted over wideband channels is studied in the context of schemes having an effective throughput of 2 bits/symbol (BPS) and 3 BPS. At high implementational complexities, the best performance was typically provided by Alamouti's unity-rate G/sub 2/ code in both the 2-BPS and 3-BPS scenarios. However, if a low complexity implementation is sought, the 3-BPS 8PSK space-time trellis code outperforms the G/sub 2/ code. The G/sub 2/ space-time block code is also combined with symbol-by-symbol adaptive orthogonal frequency division multiplex (AOFDM) modems and turbo convolutional channel codecs for enhancing the system's performance. It was concluded that upon exploiting the diversity effect of the G/sub 2/ space-time block code, the channel-induced fading effects are mitigated, and therefore, the benefits of adaptive modulation erode. In other words, once the time- and frequency-domain fades of the wideband channel have been counteracted by the diversity-aided G/sub 2/ code, the benefits of adaptive modulation erode, and hence, it is sufficient to employ fixed-mode modems. Therefore, the low-complexity approach of mitigating the effects of fading can be viewed as employing a single-transmitter, single-receiver-based AOFDM modem. By contrast, it is sufficient to employ fixed-mode OFDM modems when the added complexity of a two-transmitter G/sub 2/ scheme is affordable.

Thus far, most work on space-time trellis codes (STTCs) has assumed that the transmitter has no knowledge about the channel. In certain situations, however, it is reasonable to assume that the channel information at the transmitter is available. In this paper, we consider diagonally weighted space-time trellis codes with two transmit antennas. We derive performance criteria for designing STTCs and a feedback scheme in a perfect feedback channel. A simple modification of the conventional STTC is proposed, based on the performance criteria, and some modified STTCs are found through computer search. Simulation results show that the modified STTCs achieve improved performance over a wide range of feedback channel conditions.

To achieve full cooperative diversity in a relay network, most of the existing space-time coding schemes require the synchronization between terminals. A family of space-time trellis codes that achieve full cooperative diversity order without the assumption of synchronization has been recently proposed, where it is assumed that the delays occurring at the relays must be integer multiples of the symbol duration. In this paper, we consider a cooperative system in which the delays can be fractional symbol duration and, correspondingly, multiple sampling per symbol interval is used at the destination. We show that the previously proposed space-time trellis codes for the system with integer symbol delays can still achieve asynchronous full diversity in the new scenario. Furthermore, compared with the applications in the system with integer symbol delays, the decoding complexity of the optimal Viterbi algorithm for the codes does not increase in the system with fractional symbol delays.

In ST-MTCM, the inter-distance, especially the intra-distance can determine the system performance, therefore, we focus attention on maximizing the intra-distance and the inter-distance. Using the proposed scheme, the optimum codes can achieve the theoretical maximal diversity gain and improves the coding gain compared to known codes.