Concatenated space-time codes for quasi-static fading channels: constrained capacity and code design

This paper proposes new upper hounds on the performance of space-time trellis codes (STTC) over quasi-static fading channels (QSFC). The proposed bounding approach combines a new low signal-to-noise ratio upper bound together with the traditional union bound. The derived upper bounds show much improved ability to predict the performance of STTC over QSFC, as can be seen from applying them to a published example of STTC.

This paper presents a technique to obtain an expurgated union bound on the frame error rate (FER) of space-time trellis codes (STTCs) on quasi-static Rician fading channels. We first present an algorithm to compute the distance spectrum of STTCs. The proposed algorithm iteratively manipulates the entries of the transition matrix of the product state transition diagram, which is convenient for symbolic computation. Then, a new method to identify the dominant quasi-static fading error events is proposed. Comparisons with simulated results reveal that the expurgated union bound on the FER (obtained using the limiting-before-average technique) using these dominant error events is tight.

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.

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.

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.

A novel full diversity space-time trellis code, referred to as an assembled space-time trellis code (ASTTC), is presented in this letter. For this scheme, space-time trellis coded signals are first linearly transformed, and then the transformed signals are coded by using the Alamouti space-time block code. A new design criterion is proposed. It is shown that the ASTTCs can achieve not only the full diversity order but also a significant coding gain determined by the minimum weighted code distance (MWCD). Based on this design criterion, a new 4-state code is derived by a systematic code search. Simulation results show that the new ASTTC is superior by about 1.7 dB to the TSC (TarokhSeshadri-Calderbank) code at the frame error rate (FER) of 1.0e-2 over quasi-static fading channels.

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

In this thesis we investigate the effects of the physical constraints such as antenna aperture size, antenna geometry and non-isotropic scattering distribution parameters (angle of arrival/departure and angular spread) on the performance of coherent and non-coherent space-time coded wireless communication systems. First, we derive analytical expressions for the exact pairwise error probability (PEP) and PEP upper-bound of coherent and non-coherent space-time coded systems operating over spatially correlated fading channels using a moment-generating function-based approach. These analytical expressions account for antenna spacing, antenna geometries and scattering distribution models. Using these new PEP expressions, the degree of the effect of antenna spacing, antenna geometry and angular spread is quantified on the diversity advantage (robustness) given by a space-time code. It is shown that the number of antennas that can be employed in a fixed antenna aperture without diminishing the diversity advantage of a space-time code is determined by the size of the antenna aperture, antenna geometry and the richness of the scattering environment. In realistic channel environments the performance of space-time coded multipleinput multiple output (MIMO) systems is significantly reduced due to non-ideal antenna placement and non-isotropic scattering. In this thesis, by exploiting the spatial dimension of a MIMO channel we introduce the novel use of linear spatial precoding (or power-loading) based on fixed and known parameters of MIMO channels to ameliorate the effects of non-ideal antenna placement on the performance of coherent and non-coherent space-time codes. The spatial precoder virtually arranges the antennas into an optimal configuration so that the spatial correlation between all antenna elements is minimum. With this design, the precoder is fixed for fixed antenna placement and the transmitter does not require any feedback of channel state information (partial or full) from the receiver. We also derive precoding schemes to exploit non-isotropic scattering distribution parameters of the scattering channel to improve the performance of space-time codes applied on MIMO systems in non-isotropic scattering environments. However, these schemes

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.

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.

The pragmatic approach for the construction of space-time codes over block fading channels leads to low complexity encoders/decoders, making them suitable for various applications including cooperative communications. We propose a design methodology for pragmatic space-time codes, which is based on an extension of the concept of generalized transfer function. Our search algorithm provides code generators for arbitrary number of states, antennas, and fading rates. Numerical results show that the performance of the pragmatic space-time codes obtained by our design methodology is generally better than that of previously known space-time trellis codes in block fading channels.

Wireless sensor network (WSN), a network of minute interconnected sensing element nodes communicating within themselves utilizing radio frequency signals and utilized in immensely enormous quantities to examine and realize the physical world. The communicating sensing element nodes are power-driven by batteries, which have a circumscribed lifetime. Hence managing the energy is a primary requisite for the design of WSN. In this paper, an efficient wireless sensor network utilizing a cooperative Multiple Input Multiple Output (MIMO) predicated on Space Time Trellis Code (STTC) is proposed. This STTC based cooperative MIMO technique is incorporated into Exclusive OR — Low Energy Adaptive Clustering Hierarchy (XOR-LEACH) protocol. For selection of cluster head, the last cluster head and a arbitrary binary vector are XORed together. The proposed system obtains amended performance and is compared with the existing LEACH protocol in terms of network lifespan and residual energy. This system performance in terms of Bit Error Rate (BER) has been analyzed for various detection techniques.

The transmission scheme of multilayered space-time trellis codes (ML-STTC) achieves tradeoff between diversity gain and multiplexing gain by combining space-time trellis code (STTC) and layered space-time (LST) structure in multiple-input and multiple-output (MIMO) systems. In this paper, iterative minimum mean square error (MMSE) group detection and iterative MMSE interference cancellation (IC) group detection schemes are proposed to improve the performance of ML-STTC. Moreover, the iteration can reduce the influence of the detection order on performance, and compensate for the performance loss of the firstly detected layer instead of power allocation in the iterative MMSE IC group detection scheme.

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.