Space-time Trellis Codes Research Articles

Performance of STTC-MC-CDMA Systems with Imperfect Channel Estimation

Since, in a practical system perfect channel state information (CSI) is not possible due to presence of noise. This paper deals with the performance of space-time trellis code (STTC) in multi-carrier code-division multiple-access systems in presence of channel estimation (CE) error and results are compared with perfect CSI at the receiver. The pilot symbol assisted (PSA) technique is used for CE employing minimum mean-square error method. The symbol error rate (SER) performance is observed by employing Viterbi decoding algorithm to decode STTC code at the receiver in multi-path fading channel. The simulated SER performances in presence of CE error and with perfect CSI are compared with the theoretical performances to validate the theoretical analysis.

Adaptively Grouped Multilevel Space-Time Trellis Codes

Grouped multilevel space-time trellis codes (GMLSTTCs) utilize multilevel coding (MLC), antenna grouping and space time trellis codes (STTCs) for simultaneously providing coding gain, diversity improvement and increased spectral efficiency. The performance of GMLSTTCs is limited due to predefining of the antenna groups. It has been shown that when perfect or partial channel state information is available at the transmitter, the performance and capacity of space-time coded system can be further improved. In this paper, we present a new code designed by combining MLC, STTCs, antenna grouping and channel state information at transmitter, henceforth referred to as adaptively grouped multilevel space time trellis codes (AGMLSTTCs). AGMLSTTCs use a single full-diversity STTC at initial some levels and multiple STTCs at some later levels. The single full diversity STTC at each initial level spans all transmit antennas and the STTC at each later level spans a group of transmit antennas. The channel state information at the transmitter is used to adaptively group the transmit antennas for the later levels. Instantaneous channel power gain is calculated between each transmit antenna and all the receive antennas. A subset of transmit antennas having maximum channel power gain is selected to form a group. The simulation results show that AGMLSTTCs enable to transmit more than one data symbol per time slot with improved error performance over GMLSTTCs with predefined transmit antenna grouping.

Optical implementation of a space–time-trellis code for enhancing the tolerance of systems to polarization-dependent loss

We propose a space-time coding scheme designed to increase the tolerance of fiber-optic communications systems to polarization-dependent loss (PDL). A notable increase in the tolerable amount of average link PDL is achieved without affecting the complexity of the overall optical communications link. Other advantages include seamless integration with the broadly deployed blind equalization modules relying on the constant modulus algorithm.

Distributed space‐time trellis codes with continuous phase modulation for amplify and forward relaying

Continuous phase modulation (CPM) is a non-linear power/bandwidth efficient modulation method. Linear modulation methods such as phase shift keying or quadrature amplitude modulation produce large power drain at the power amplifier of the transmitter. Therefore CPM may be an alternative to these modulations in relay/cooperative systems because of its constant envelope property, which enables us to use inexpensive and energy-efficient non-linear power amplifiers. In this study, the authors investigate optimum distributed space-time CPM trellis codes for amplify and forward relaying systems with one to four relays and specifically consider minimum shift keying and quaternary continuous phase frequency shift keying with modulation indices of 1/2 and 1/4. Novel distributed space-time CPM trellis codes are obtained. Error performances of the novel codes and their classical counterparts are compared over frequency non-selective quasi-static Rayleigh-fading channels using the Viterbi algorithm at the destination terminal and superiority of the novel codes are presented.

Improving the Evaluation Performance of Space-Time Trellis Code through STTC Visualisation Tool

In this paper we present a new visualisation approach in the effort of improving the evaluation strategy of space-time trellis code (STTC) generator matrix G. To our knowledge, although visualisation is widely used to handle a variety of problems, it has never been employed specifically to solve complexity problems that are related to generator matrix G evaluation. Most approaches are either mathematically or algorithmically inclined. As such, they tend to offer a series of refinement that enhances the current available method, but do not provide fresh insight on the problem at hand. By comparing it with the enhancement strategy that was discovered via the normal approach (i.e., by analysing algorithm) it was discovered that visualisation had inspired an entirely different pruning technique that outperformed the common approach by 20%.

Performance Analysis Of A Cellular System Using C-Ofdm Techniques

The basic idea of COFDM is to split the modulation samples of incoming data stream onto a large number of carriers instead of modulating a unique carrier. Therefore, COFDM is an effective technique for combating multi-path fading and for highbit- rate transmission over wireless channel. In a single carrier system a frequency Selective fading can cause the entire transmission link to fail, but in an COFDM multi carrier system, only a small percentage of the sub-carriers will be corrupted. Frequency and time interleaving in conjunction with forward error correction coding can then be used to correct for erroneous subcarriers. The background information with the aim to provide an intuitive explanation of our research motivation. C-OFDM is the modulation scheme of choice , as enshrined in International standard for all forms of digital broadcasting both audio and video and including satellite, terrestrial, and cable. In the existing standard the “coding” referred to consists of an inner convolutional code concatenated with an outer R-S code; here in this thesis, we replace the inner code with the coding like space time trellis code for analysis.

MIMO 시스템에서 반복 복호 알고리즘 기반의 계층적 시공간 부호화 방식 연구

차세대 무선통신에서는 다양한 서비스, 높은 신뢰도와 함께 빠른 전송속도를 요구한다. 이러한 요구를 만족시키기 위해서 시공간 격자부호와 터보 부호기를 결합시키는 계층적 시공간 부호기를 사용하였다. 계층적 시공간 부호기에서는 내부 부호와 외부 부호의 두 부호를 연속적으로 연접 시키는 방식이다. 내부 부호로는 DVB-RCS NG 시스템에서 표준으로 제안된 터보 Pi 부호를 사용하고, 외부 부호로는 Blum에 의해 제안된 시공간 격자 부호를 사용한다. 또한 효율적으로 두 부호기를 연접시키기 위하여 인터리버 기법을 사용한다. 그리고 기존의 복호 방법은 시공간 격자 부호와 터보 복호기 내부에서만 반복 복호를 하지만, 본 논문에서는 BCJR 복호기와 함께 전체 반복을 통하여 성능을 향상시키는 방안을 제시하고 시뮬레이션 하였다. 시뮬레이션 결과 본 논문에서 제시하는 효율적인 연접 방식을 이용하면 일반적인 연접 방식에 비하여 약 1.3~1.5dB의 성능이 향상되었다. The next-generation wireless communication requires fast transmission speeds with various services and high reliability. In order to satisfy these needs we study MIMO system used layered space time coded system (LST) combining space time trellis codes (STTC) with turbo codes. In LST, two codes that are inner and outer codes are concatenated in the serial fashion. The inner codes are turbo Pi codes suggested in DVB-RCS NG system, and outer codes are STTC codes proposed by Blum. The interleaver technique is used to efficiently combine two codes. And we proposed and simulated that a full iteration method between turbo decoder and BCJR decoder to improve the performance instead of only processing inner-iteration turbo decoder. The simulation results of proposed effective layered method show improving BER performance about 1.3~1.5dB than conventional one.

Super-orthogonal trellis-coded spatial modulation

Spatial modulation (SM), which employs the indices of multiple transmit antennas to transmit information in addition to the conventional M-ary signal constellations, is a novel transmission technique that has been proposed for multiple-input multiple-output systems. In this study, a new class of space-time trellis codes, called ‘super-orthogonal trellis-coded SM’ (SOTC-SM), is proposed. These codes combine set partitioning and a super set of space-time block coded SM (STBC-SM) codewords to achieve maximal diversity and coding gains by exploiting both SM and space-time block codes. Unlike super-orthogonal space-time trellis codes (SOSTTCs), which parametrise the orthogonal STBCs, these new codes expand the antenna constellation using the principle of SM. Systematic construction methods are presented for the SOTC-SM scheme and design examples are given for 2, 4 and 8 trellis states, at 2, 3 and 4 bits/s/Hz spectral efficiencies. The approximate bit-error probability performance of SOTC-SM is derived and shown to match computer simulation results. A simplified maximum likelihood detection method for the proposed scheme is given. It is shown through computer simulations that the proposed SOTC-SM schemes achieve significantly better error performance than SOSTTCs with comparable complexity.

인지 네트워킹 기반 중첩 융합 네트워크에서 이중 가상 셀 운영방안의 성능분석

데이터 트래픽의 증가와 더불어 인지 기반 중첩 융합 네트워크 환경 하에서의 서비스 성능이 중요한 이슈로 떠오르고 있다. 이에 따라 다양한 이종 네트워크(HetNet)가 결합된 환경 하에서 주변상황의 인지 기능을 활용하는 이중 가상 셀의 구성과 특징에 대해 살펴보고 자원의 효과적 활용에 적합한 개별 이종 네트워크의 특성분석과 특성을 반영하는 시스템측면의 최적화를 고려하여 성능측면의 분석을 다루고자 한다. 이를 위해 가상 이중 셀 시스템의 구성과 운영이 필수적으로 요구된다. 본 논문에서는 기지국의 소형화와 지능화가 진행됨에 따른 활용도 측면의 성능을 분석하였다. 고려하는 시스템은 유용한 가상의 신호를 찾을 수 있는 능력을 활용하여 가상의 이중 셀을 구성하고 고속이동에 따른 무선링크에서의 성능열하를 방지하고 고속의 데이터 전송을 위한 시-공간 트렐리스 코드를 적용한 시스템의 성능을 분석하여 그 유용성에 대해서 시뮬레이션을 통하여 정량적인 분석결과를 얻었다. 이를 바탕으로 다양한 파라메터가 주어진 환경 하에서 전체 시스템에 어떤 영향를 미치는지를 해석하고 고려하는 시스템의 특징을 고찰하였다. With the fast growing data traffic, the performance of the convergent overlay network environment under the cognitive networking environment is crucial for the implementation of the efficient network structure. In order to achieve high capacity and reliable link quality in wireless communication of the overlay convergent networks with the cognitive networking based on the advanced capability of the mobile terminal, a Distributed Wireless Communication System (DWCS) can provide the capability of ambient-aware dual cell system's operation. This paper has considered virtual cell: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on DWCS network. One is the Active Virtual Cell which exists for user's actual data traffic and the other is the Candidate Virtual Cell which contains a set of candidate antennas to protect user's link quality from performance degradation or interruption. The considered system constructs DVC by using cognitive ability of finding useful virtual signals. Also, for multi-user high-rate data transmission, the DWCS system exploits Space-Time Trellis Codes. The effects of changing environments on the system performance has been investigated thereafter.

비정형 통신 채널 환경에서 비행형 에어노드의 대역 효율적인 통신을 위한 연접 다이버시티 시스템

본 논문에서는 비정형 궤도를 따라 이동하며 통신하는 비행체들 간의 데이터 전송 신뢰성을 보장하기 위해 다이버시티 TCM(trellis coded modulation) 코드를 연접한 연접 다이버시티 시스템을 제안하고 그 성능을 분석한 후 제안한 시스템을 설계하였다. 제안한 시스템은 다이버시티 TCM 코드를 연접하였기 때문에 부호화 이득 및 대역 활용의 효율성이 높을 뿐만 아니라 데이터 전송 신뢰성 또한 높다. 이러한 특성은 컴퓨터 시뮬레이션을 통해 확인할 수 있는데 제안한 시스템의 비트 오율 성능(BER)을 시뮬레이션 하여 TCM 코드와 비교해 본 결과 BER <TEX>$10^{-2}$</TEX>에서 약 11dB 우수 하고 최대 다이버시티 이득을 갖는 시공간 블록코드와 비교한 결과 BER <TEX>$10^{-3}$</TEX>에서 약 10dB 우수하다. 또한 다이버시티 이득과 코딩 이득을 갖는 시공간 트렐리스 코드와 비교하였을 경우에는 최대 약 1.5dB 우수함을 확인할 수 있다. 마지막으로 제안한 시스템을 HDL(hardware description language)로 구현하여 그 동작을 확인해 본 결과 그 동작의 결과가 적합함을 확인하였다. In this paper, we propose a concatenated diversity system to assure the data transmission reliability between flight type air nodes which move according to their atypical orbit, then its performance is analyzed using computer simulation and it is designed with hdl. The proposed system cannot only improve a bandwidth efficient and coding gain from diversity TCM code but also the reliability of data transmission is high. From the computer simulation result about bit error rate(BER) of the proposed system, we confirm that its BER performance is about 11dB greater than TCM code at <TEX>$10^{-2}$</TEX> and about 11dB greater than space time block code at <TEX>$10^{-3}$</TEX> which has a full diversity gain. In addition, when we compare its BER performance with space time trellis code which has both a diversity gain and a coding gain, the performance of the proposed system is greater than about 1.5dB at <TEX>$10^{-5}$</TEX>. Lastly, after designing the proposed system with HDL, we can confirm that the operation result is correct.

Distribution and Density Functions of Capacity for Layered Space Time Architecture

In wireless communications spectrum is a scarce resource, and hence imposes a high cost on high data rate transmission. With the emergence of multiple antenna system, another very resourceful dimension-space was utilized for information transmission in air. It has been proved that multiple antenna systems provide higher gain in capacity without increasing the use of spectrum, reliability, throughput, power consumption and less sensitivity to fading, therefore leading to high data rates of wireless communication systems, which is the most sorted outcome of all research work. The study of performance limits of Multiple Input Multiple Output (MIMO) system becomes most important to design and understanding MIMO systems. There are many schemes that can be applied to MIMO systems, such as space time block codes, space time trellis codes and Layered Space Time Architecture. In this paper, the performance of general MIMO system based on Layered Space Time Architecture is studied. For different number of transmit and receive antennas, the Probability Density Function (pdf) and Cumulative Distribution Function (cdf) distributions for capacity of different layers for different SNRs were analyzed and plotted.

Implementation of Space-Time Turbo Coded MC-CDMA Systems

In this paper, the performances of space-time turbo-code (STTuC) and space-time trellis code (STTC) in conjunction with multi-carrier code-division multiple-access (MC-CDMA) systems are evaluated. The minimum mean-square error (MMSE) detection technique is used with multiple input multiple output (MIMO) antenna diversity in quasi static fading channel. The symbol error rate (SER) is obtained using simulation by employing maximum a posteriori (MAP) decoding technique for turbo code and Viterbi algorithm for trellis code system. It is observed that the STTuC-MC-CDMA system performs better then STTC-MC-CDMA system. It is also noted that by increasing the number of iterations the performance gain can be increased up to a certain limit. On the other hand, this improvement in performance comes at the cost of increased computational complexity.

Implementation of Space Time Trellis Code Using Rayleigh Fading Scenario

In this paper we implement space time trellis code using relay fading scenario. We present here the design of the 4psk with 2 transmit antennas and 1,2 receiver antennas at 4,8,16& 32 state. In this paper we constructed 4-psk sttc code using rank, determinant and euclidean distance criterion over rayleigh fading scenario. Keywords: space-time trellis code; multiple transmit antenna, multiple receiver antenna; diversity; wireless communication; fading; s\n ratio;

A novel weighted multilevel space–time trellis coding scheme

It has been shown that when perfect or partial channel state information (CSI) is available at the transmitter, the performance and capacity of a space–time coded system can be further improved. Multilevel space–time trellis codes (MLSTTC’s) are capable of simultaneously providing bandwidth efficiency, diversity improvement and coding gain with significantly reduced decoding complexity, especially for larger constellations and higher throughputs. In this paper, we present a design of combined multilevel space–time trellis codes and beam forming based on feedback from receiver, henceforth referred to as weighted multilevel space–time trellis codes (WMLSTTCs). The channel profile is used to provide a beam forming scheme that achieves the better performance by properly weighting transmitted signals. Weights are selected that matches best with a channel profile feedback from the receiver indicative of long-term characteristics of the wireless channel. WMLSTTCs provide improvement in performance of MLSTTCs.

New Trellis Code Design for Spatial Modulation

Spatial modulation (SM), in which multiple antennas are used to convey information besides the conventional M-ary signal constellations, is a new multiple-input multiple-output (MIMO) transmission technique, which has recently been proposed as an alternative to V-BLAST (vertical Bell Labs layered space-time). In this paper, a novel MIMO transmission scheme, called spatial modulation with trellis coding (SM-TC), is proposed. Similar to the conventional trellis coded modulation (TCM), in this scheme, a trellis encoder and an SM mapper are jointly designed to take advantage of the benefits of both. A soft decision Viterbi decoder, which is fed with the soft information supplied by the optimal SM decoder, is used at the receiver. A pairwise error probability (PEP) upper bound is derived for the SM-TC scheme in uncorrelated quasi-static Rayleigh fading channels. From the PEP upper bound, code design criteria are given and then used to obtain new 4-, 8- and 16-state SM-TC schemes using quadrature phase-shift keying (QPSK) and 8-ary phase-shift keying (8-PSK) modulations for 2,3 and 4 bits/s/Hz spectral efficiencies. It is shown via computer simulations and also supported by a theoretical error performance analysis that the proposed SM-TC schemes achieve significantly better error performance than the classical space-time trellis codes and coded V-BLAST systems at the same spectral efficiency, yet with reduced decoding complexity.

New efficient method to generate optimal 2 n -PSK space-time trellis codes with a large number of transmit antennas

In this study, the author propose a new method called coset partitioning to generate easily and efficiently the best space-time trellis codes (STTCs), thereby reducing considerably the usual important search time. This method, used in the case of 2^n-PSK STTCs, is an extension of the set partitioning proposed by Ungerboeck based on the coset and lattice Calderbank's approach. The main guideline of the coset partitioning is to divide the set of multiple input and output symbols into cosets, not into simple sets as the set partitioning. The case of a large number of transmit antennas is considered because the time to obtain the best STTCs with an exhaustive search is very important when the number of transmit antennas increases. Using the coset partitioning, new 4-PSK STTCs with five to six transmit antennas are generated. Simulation results show that the new codes slightly outperform the best corresponding known codes. Thanks to the effectiveness of the coset partitioning, for the first time, 4-PSK STTCs with seven and eight transmit antennas and 8-PSK STTCs with five to six transmit antennas are obtained. Their performance is also analysed by simulation.

Pragmatic Space-Time Trellis Codes: GTF-Based Design for Block Fading Channels

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.

MIMO System Optimization Using STTC Based STBC with Channel Estimation

We propose a new architecture involving space time trellis code (STTC) concatenated with space time block code (STBC) using modified sphere decoder (MSD-1) at the receiver for improving system performance in the multi-antenna environment. With the aim of increasing the ‘Diversity Order’ of signal set, rotated versions of quadrature amplitude modulation (QAM) constellation have been used in multidimensional space and the associated design parameters required to search an effective signal constellation have been optimized. The limitations on account of complexity owing to multiple copies of data being received after experiencing various channel effects in the multi input multi output (MIMO) systems have been looked into. Accordingly, MSD-1 algorithm has been proposed with lower complexity, which in turn would give rise to a system with high spectral efficiency. The system gains have been verified with channel state information (CSI) errors.

Optimal Generation of Space–Time Trellis Codes via Coset Partitioning

Criteria for designing good space-time trellis codes (STTCs) have been developed in previous publications. However, the computation of the best STTCs is time consuming, because a long exhaustive or systematic computing search is required, particularly for a high number of states and/or transmit antennas. To reduce the search time, an efficient method must be employed to generate the STTCs with the best performance. In this paper, a technique called coset partitioning is proposed to easily and efficiently design optimal 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> -phase-shift keying (PSK) STTCs with any number of transmit antennas. Coset partitioning is an improved extension to multiple-input-multiple-output (MIMO) systems of the set partitioning proposed by Ungerboeck. This extension is based on the lattice and coset Calderbank approach. With this method, optimal blocks of the generator matrix are obtained for 4-PSK and 8-PSK codes. These optimal blocks lead to the generation of the STTCs with the best Euclidean distances between the codewords. Thus, new codes are proposed with three to six transmit antennas for 4-PSK modulation and with three and four transmit antennas for 8-PSK modulation. These new codes outperform the corresponding best known codes. In addition, the first 4-PSK STTCs with seven and eight transmit antennas and the first 8-PSK STTCs with five and six transmit antennas are given, and their performance is evaluated by simulation.

An Efficient ZJ-Based Decoding Algorithm for Space-Time Trellis Codes in Slow Rayleigh Fading Channels

In this paper, we propose a computationally efficient decoding algorithm for space-time trellis codes in slow Rayleigh fading channels. The proposed scheme is based on a stack algorithm with two key ideas: (i) a variable stack size depending upon the signal-to-noise ratio to avoid the exhaustive search of paths and (ii) a normalized metric, which is defined as each cumulative path metric divided by its own length in the stack, to provide an appropriate comparison of the paths with different lengths. Simulation results demonstrate that the proposed algorithm achieves near-ML performance with significant reduction in complexity, compared with the conventional Viterbi algorithm.