Study of Error Resilience Efficiency of ViterbiConvolutional Coding Combined with STBC in MIMO Systems

Convolutional code is a coding scheme used in communication systems including deep space communications and wireless communications.It provides an alternative approach to block codes for transmission over a noisy channel.The block codes can be applied only for the block of data.The Convolutional coding has an advantage over the block codes in that it can be applied to a continuous data stream as well as to blocks of data.Viterbi decoder employed in digital wireless communication plays a rife role in the overall power consumption of trellis coded modulation decoder.Power reduction in Viterbi decoder could be achieved by reducing the number of states.A pre-computation architecture with T-algorithm was implemented for this purpose, and when we compare this result with full Trellis Viterbi decoder, this approach significantly reduces power consumption without degrading decoding speed.Convolutional encoding with viterbi decoding is a powerful FEC technique that is particularly suited to a channel in which the transmitted signal is corrupted mainly by Additive White Gaussian Noise (AWGN).It operates on data stream and has memory that uses previous bits to encode.The Viterbi Algorithm (VA) is proposed, used for decoding a bit stream that has been encoded using FEC code.The Convolutional encoder adds redundancy to a continuous stream of input data by using a linear shift register.A pre-computation architecture with Viterbi algorithm is implemented for this purpose, Viterbi (Convolutional) encoder and Viterbi decoder are designed and implemented using FPGA technology, which are the essential blocks in digital communication systems.It is particularly suited to a channel in which the transmitted signal is corrupted mainly by AWGN.The Viterbi decoder of Constraint length 7 and code rate ½ is considered.The design is implemented using verilog on Xilinx Spartan 3E and advanced Spartan 6 board and the results and Comparisons are presented.

This paper compares the system performance of transmit diversity schemes for use in interference-limited cellular systems. We focus on evaluating the performance of Alamouti space time block codes (STBC) and cyclic delay diversity (CDD) codes, which are being actively considered for adoption within the 3 GPP-long-term-evolution (LTE) and 802.16e WiMAX standards. While the performance of transmit diversity schemes has been extensively evaluated in noise-limited scenarios, their performance in co-channel interference (CCI) limited cellular systems has received limited attention so far. As cellular systems adopt frequency reuse of one, co-channel interference from other cells becomes a major limitation to system performance. We present system simulation results comparing the performance of transmit diversity schemes using matched filter reception for a multi-carrier OFDM-based cellular system. In particular, the performance of STBC and CDD schemes is compared with respect to the evolving third generation 3 GPP-LTE standard. Our comparison highlights the spatial as well as the multi-user diversity aspects of these schemes and considers a variety of scenarios that will require their use. Our results show that CDD can significantly improve the system spectral efficiency and cell-edge performance over STBC, when used in combination with frequency-dependent scheduling. For open loop transmission without scheduling, the relative diversity gains of STBC and CDD at link layer depend on the interference scenario considered, while the system performance of these schemes is very similar.

In this paper, we consider the two-way relay channel (TWRC) over which communication is performed using space-time block codes (STBC) with physical-layer network coding (PNC) protocol. The three-node two-way relaying (TWR) model consists of two end nodes (sources) simultaneously communicating with each other over a relay node where each node is equipped with two antennas and uses Alamouti's STBC to provide diversity. We consider non-reciprocal channels where fading channel coefficients are independent for opposite directions of the same link. We first derive closed form expressions for the outage probability of the STBC-TWR system and uncoded TWRC assuming equal transmit power at each node and decode-and-forward (DF) strategy at the relay. We show that the STBC-TWR system significantly improves the uncoded TWRC outage performance. Then, to further improve the performance, we propose an optimal power allocation in TWR scheme employing Alamouti's STBC and PNC protocol. The optimal power allocation is obtained by maximizing the sum-rate under the total power constraint. We show that the optimal power allocation considerably improve the outage performance as well as the sum-rate compared to the equal-power case.

Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation scheme widely used in 4G. It is effective for reducing the effects of multipath delay in wireless communication. For OFDM system, total delay spread (Td) is less than symbol period (T); it can be combined with antenna arrays at transmitter and receiver (MIMO) to increase diversity gain called as MIMO-OFDM system. MIMO-OFDM improves system capacity on time-variant and frequency-selective channels. The quality of service provided by a system greatly depends upon the correct selection of modulation scheme. In this paper, analysis and simulation of OFDM-MIMO system with different digital modulation schemes like BPSK, 8-PSK, QPSK, and QAM is performed using Alamouti space–time block codes (STBC). STBC uses spatial and time dimensions for error control unlike traditional methods that uses only time dimension. A comparison study shows that for a given data rate and channel conditions, OFDM-MIMO using STBC with BPSK modulation is better compared with other digital modulation techniques in terms of error performance. OFDM-MIMO using STBC with BPSK modulation is further analyzed and simulated for various antenna configurations. It is observed that as numbers of antennas at transmitter and receiver side are increased, the system diversity increases and gives better performance in terms of BER.

The Alamouti Space Time Block Code (STBC) based Orthogonal Frequency Division Multiplexing (OFDM) is very attractive in frequency selective channel as the channels remain constant over Alamouti code period (two consecutive OFDM symbol block). But when the channel is fast fading, this assumption does not holds good and causes co-channel interference (CCI). Hence, the simple Alamouti detection method is not sufficient to recover the original transmitted signal from the mixed transmitted signals at the receiver side. To cancel the effects of CCI, several detection techniques are addressed namely SIC, DMLD, DZFD, DF and ML. The ML method has the optimum performance but the computational complexity is very high. Therefore, we propose a suboptimal MDF detection which provides comparable performance to that of ML with very less computational complexity. Finally, the performances of the above detection methods are compared in terms of symbol error rate (SER) and computational complexity for STBC OFDM system over doubly selective channel.

Alamouti空时块码与波束形成相结合的方案只使用了两个功率均分的波束,在很多情况下并非最优。该文提出了新的空时块码与波束形成相结合的方案,新方案能够根据信道互相关矩阵的特征值,展开不超过发射端天线数量的波束,在满足空时块码发射天线数量等于波束数量的条件下,与任意码率空时块码结合。该文还利用Gauss-Chebyshev积分对线性调制下新方案的误符号率进行了性能分析,得出了简单的数值计算表达式。新方案由于同时获得了分集增益和波束形成增益,显著提高了系统的性能。

Wireless systems have rapidly moved toward becoming piece of regular day to day existence. Cell Phone systems, Remote LANs and individual region systems are only a couple of cases of largely utilized wireless communications. The Space Time Coding has advanced as a most dynamic research range in wireless communications. Spatial multiplexing builds categorize limit by division a soaring rate motion into several inferior rate streams and transmitting them through the diverse dissimilar antennas. In spatial multiplexing, the beneficiary can effectively interpret each stream given that the got signals have sufficient spatial symbols and that the receiver has sufficient antennas to isolate the streams. The outcome of utilizing these MIMO systems is higher information rate or longer transmit extend without requiring extra transfer speed or transmit control. This paper introduces full information of diversity coding for MIMO system. STBC (space-time block coding) plans including Alamouti's STBC used for 2 transmit antenna plus 2 recievier antanna are investigated. At last, these STBC systems are actualized and analyzed execution as indicated by their bit-error rates utilizing BPSK, QPSK, and 8-PSK modulation schemes.

In recent times, Chaos communication plays a significant role in addressing the security challenges that are more common in the regular communication systems. By exploiting the chaotic waveform properties, variety of chaos-based communication systems are proposed. Considering the aforementioned facets of communication, this research objective at merging the space-time block code (STBC) and orthogonal differential chaos shift keying (ODCSK) methods to improve the security aspects of multiple-input multiple-output (MIMO) based wireless system. Chaos signal is created by using the method called logistic mapping to achieve better secrecy. STBC method is used during the modulation stage for arranging the chaos signal. This system with different types of STBCs is aimed at analysing the differential chaos shift keying (DCSK) and orthogonal DCSK (ODCSK) modulation in AWGN channel. MATLAB software is used to simulate the Bit Error Rate [BER]. Initial simulation proves that the combination of orthogonal DCSK and Alamouti STBC with MIMO system gives better results for AWGN channel when compared to other combinations.KeywordsDifferential Chaos shift keyingSpace-time block codeMultiple-input multiple-output

In this paper, we consider the three-node two-way relay channel (TWRC) over which communication is performed using space-time block codes (STBC) with physical-layer network coding (PNC) protocol. Two end nodes simultaneously communicate with each other over a relay node where each node is equipped with two antennas and uses Alamouti's STBC to provide diversity. First, a closed form expression for the outage probability of the STBC-TWR system is derived, assuming nonreciprocal channels, equal transmit power at each node and decode-and-forward (DF) strategy at the relay. It is shown that the STBC-TWR system significantly improves the uncoded TWRC outage performance. Then, to further improve the performance, an optimal power allocation to maximize the sum-rate under the total power constraint, is proposed. It is shown that the optimal power allocation considerably improve the sum-rate as well as the outage performance compared to the equal-power case.

An algorithm for generating random binary data, convolutional encoding the data, passing the encoded data through a noisy channel, quantizing the received channel symbols, and performing Viterbi decoding on the quantized channel symbols to recover the original binary data is implemented in MATLAB using built-in functions in Communications Toolbox. The developed tool will be used in the educational process in the course Channel coding in telecommunications systems and it will enable students to comprehend the principles of convolutional encoding and Viterbi decoding.

Accurate channel estimates are needed in space-time coded OFDM systems for decoding purposes. In this paper, a novel channel tracking algorithm based on space-time coded training and information symbols is presented. The algorithm takes advantage of the orthogonality properties of the space-time block codes and it is therefore capable of providing channel estimates without performance degradation due to estimation errors from adjacent channels. The algorithm is tested via Monte Carlo computer simulations using both slowly Rayleigh fading channels and time-invariant frequency selective channels and Alamouti space-time block coding. Computer simulations also show that this simple algorithm outperforms LMS-based approach without additional complexity.

The demand for high data rates and low implementation complexity form two of the prerequisites for future wireless local area networks. The V-BLAST architecture and the Alamouti space-time block code are two strong candidates for this particular implementation. The drawback of V-BLAST is its poor performance in correlated fading channels, and for Alamouti STBC, the spectral efficiency is generally poorer than V-BLAST. Trying to overcome these problems leads to a hybrid V-BLAST/Alamouti scheme. Instead of decoupling antennas for separate detection, each transmitted stream is treated as a layer and detected successively using the ordered successive interference cancellation algorithm. We investigate the frame error performance of this hybrid scheme with respect to three parameters: fading channel correlation; number of receive antennas used; spectral efficiency. The hybrid's error performance is compared to those of the V-BLAST and the Alamouti STBC schemes.

This chapter looks at three important modulation paradigms. Trellis-coded modulation (TCM) is considered first. Developed in the late 1970s as a method to conserve bandwidth without sacrificing error performance it has become an extremely important modulation. The second technique is called code-division multiple access (CDMA). It falls within the broad class of multiple access methods and is an administrator's favorite. It makes the addition (or deletion) of new users essentially transparent, easing the administrator's work. However, the technique does have technical merits that warrant its study by communication engineers. It forms the basis for the so-called 3G (third generation) and beyond wireless communication systems. In contrast to TCM, CDMA is a very wideband modulation technique. The last modulation method studied uses space-time codes which provide diversity gain for the fading channel through the use of multiple transmit antennas. The important Alamouti's space-time block code (STBC) is discussed in some detail. It was first described in 1998, almost at the same time Tarokh et al . published their paper on space-time trellis codes. Trellis-coded modulation (TCM) By now one can appreciate that over an AWGN channel, the basic idea in digital communications is to find signal constellations with as large a distance between signals as possible without increasing the energy E b (joules) expended per bit inordinately and with as small a bandwidth as possible.

Media-based modulation (MBM) is a new and promising transmission scheme that employs reconfigurable antennas to create different channel fade realizations and appears as an emerging index modulation (IM) application. In this paper, we present a novel multiple-input multiple-output (MIMO) transmission scheme called multidimensional media-based modulation (M-MBM) by redesigning the classical Alamouti's space-time block coding (STBC) scheme with MBM through the use of the additional dimension of channel states. The error performance of the proposed M-MBM scheme is theoretically analyzed for correlated and uncorrelated channel states and a union bound is obtained for the average bit error probability (ABEP). Moreover, through computer simulations, the superior error performance of the M-MBM scheme over the emerging IM techniques is demonstrated.

In this paper, we propose to use Alamouti's orthogonal space-time block code to improve the performance and the robustness of the spread spectrum watermarking systems. After employing a space-time block code, we embed the coded watermark sequence into the host image in discrete wavelet transform domain. Simulation results show that the use of the space-time block codes considerably increases the robustness of the spead spectrum watermarking system under various attacks.