A Simple Layered Space-Time Block Nulling Technique for DSTTD Systems

This paper presents a new and simple decoding algorithm for layered space time block codes such as the two independent Alamouti's codes which are also called the double space-time transmit diversity (DSTTD) system. By using group interference suppression and successive interference cancellation, we can treat DSTTD as two independent space-time block codes (STBC). We can then decode both of these STBC's through a simple maximum likelihood (ML) detector with null space-based interference cancellation. We also compare the proposed interference cancellation (IC) scheme with the conventional MMSE IC scheme. The performance of the proposed IC scheme is comparable to that of the MMSE IC scheme while the complexity of the proposed scheme is lower than that of the MMSE IC scheme.

From 1820 4 times 4 binary matrices, 253 binary preprocessing matrices are designed for double space-time transmit diversity (DSTTD) systems with two 2 times 2 space-time block code (STBC) encoders. Among them, six matrices yielding the highest average minimum-post-processing SNR are proposed from numerical experimentation under uncorrelated channel conditions. The proposed preprocessing performs a superposition of the first and second (second and first) STBC symbols and a selection of two transmit antennas. Simulation results show that the proposed method provides 1.7 dB (1.8 dB) SNR improvement in uncorrelated (correlated) channel environment at 10-3 bit error rate over the conventional antenna shuffling method.

Transmit antenna shuffling (TAS) has been used widely in Double Space Time Transmit Diversity (DSTTD) systems for performance improvement. In this paper, an angle feedback and its feedback selection criterion applied in a space time coding scheme are proposed for DSTTD systems. Compared with the existing TAS scheme, according to the analysis of system, the proposed scheme has lower realization complexity. Simulations show that the proposed scheme with 2-bit angle feedback achieves almost the same performance of DSTTD systems with TAS scheme which requires 3-bit feedback.

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。

In this contribution, the performance of double space time transmit diversity (DSTTD) based multiple-input and multiple-output system with spatial diversity is investigated for cognitive radio network (CRN) based code-division-multiple-access (CDMA) system. CRN is realized in order to invoke available idle spectrum for reliable communication between base station and mobile station. DSTTD is constructed using two space- time processing unit. DSTTD is proven to provide high throughput .The user-specific spreading code is generated using sub-band frequency of CRN. Time-Frequency domain signature sequence is exploited to distinguish secondary users. The performance of CRN based DSTTD-CDMA scheme is analyzed using coded system. At each MS, iterative type of decoder is implemented to estimate secondary users’ information. The performance is analyzed for coded CRN based DSTTD-CDMA system for channel model with Stanford University Interim along with long-term evolution specifications. It is observed through simulation results that coded CR DSTTD-CDMA system establish proficient communication for secondary users while offering higher throughput and higher spectral efficiency and better performance in the context of bit-error-rate with fewer value of signal-to-noise ratio. Further, it is discerned that decoding algorithm obviate adjacent-channel interference along with secondary multi-user interference and CRN based CDMA system in conjunction DSTTD offers solution for high data rate application.

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.

The theoretical error performance of double space time transmit diversity (DSTTD) system with optimum combining receiver is analyzed in this paper. By employing both spatial multiplexing and transmit diversity in one system, DSTTD provides practical tradeoff between system spectral efficiency and diversity gain. We derive exact analytical expressions to describe the symbol error rate for DSTTD systems. The effects of both diversity gain and antenna interference introduced by spatial multiplexing are quantified in the results. In addition, the performance of DSTTD system with successive interference cancellation is also investigated. Simulation results are in excellent agreement with the theoretical results obtained in this paper.

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.

In this paper, we propose a jointly designed diagonal precoder and minimum mean-square error receiver with ordered successive interference cancellation (MMSE-OSIC) for the double space-time transmit diversity (DSTTD) system with low feedback and low-complexity. The proposed transceiver utilizes the structure of the equivalent channel of DSTTD, showing lower computational complexity and better error rate performance than the conventional antenna shuffling schemes with the channel state information at the transmitter.