Differential Space-time Block Code Research Articles

Soft-Input Soft-Output Multiple Symbol Detection for Ultra-Wideband Systems

A multiple symbol detection (MSD) algorithm is proposed relying on soft information for ultra-wideband systems, where differential space-time block code is employed. The proposed algorithm aims to calculate a posteriori probabilities (APP) of information symbols, where a forward and backward message passing mechanism is implemented based on the BCJR algorithm. Specifically, an MSD metric is analyzed and performed for serving the APP model. Furthermore, an autocorrelation sampling is employed to exploit signals dependencies among different symbols, where the observation window slides one symbol each time. With the aid of the bidirectional message passing mechanism and the proposed sampling approach, the proposed MSD algorithm achieves a better detection performance as compared with the existing MSD. In addition, when the proposed MSD is exploited in conjunction with channel decoding, an iterative soft-input soft-output MSD approach is obtained. Finally, simulations demonstrate that the proposed approaches improve detection performance significantly.

Soft-Input Soft-Output Non-Coherent Detection for Differential Space-Time Block Code Systems

A soft-input soft-output non-coherent detection algorithm is proposed for multi-antenna systems, where differential space-time block code is employed. The proposed algorithm aims to calculate a posteriori probabilities of the information bits by means of forward and backward message passing of the BCJR approach. The proposed algorithm can exploit the soft information effectively with the aid of the bidirectional message passing mechanism. In addition, the proposed algorithm can be exploited in conjunction with channel decoding to obtain an effective iterative detection and decoding approach. In view of low implementation complexity, the application of the proposed scheme is instantiated with the ultra-wideband impulse radio (UWB-IR) systems. Simulations show that the proposed approaches improve detection performance for UWB-IR systems.

Differential orthogonal space‐time block codes for four transmit antennas

A new high-order differential space-time block code (DSTBC) is introduced as an attractive alternative to the well-known coherent space-time block code (STBC) by providing both full space-time diversity and blind detection. A differential detection based on the orthogonal STBC scheme is proposed. The proposed differential scheme is a generalisation of the recent DSTBC already designed for two transmit antennas. The proposed differential encoder consists of a specific trellis diagram that creates a positive correlation between successive differential data. At the receiver side, the well-known Viterbi algorithm is applied using a specific metric that nearly compensates for the 3 dB penalty commonly introduced by the symbol by symbol differential schema, and shows a 0.5 dB performance loss only from the coherent STBC scheme.

BER Analysis of Decision-Feedback Multiple-Symbol Detection in Noncoherent MIMO Ultrawideband Systems

In this paper, we investigate noncoherent multiple-input-multiple-output (MIMO) ultrawideband (UWB) systems where the signal is encoded by differential space-time block code (DSTBC). DSTBC enables noncoherent MIMO UWB systems to achieve diversity gain. However, the traditional noncoherent symbol-by-symbol differential detection (DD) for DSTBC-UWB suffers from performance degradation compared with coherent detection. We introduce a noncoherent multiple-symbol detection (MSD) scheme to enhance the performance of DSTBC-UWB systems. Although the MSD scheme can boost the performance more as the observation window size becomes larger, the complexity of the exhaustive search for MSD also exponentially increases in terms of the window size. To decrease the computational complexity, the concept of decision feedback (DF) is introduced to the MSD for DSTBC-UWB in this paper. The resultant DF-MSD yields reasonable complexity and solid performance improvement. We provide the bit-error-rate analysis for the proposed DF-MSD. Both theoretical analysis and simulation results validate the proposed scheme.

An Improved Differential Space-Time Block Coding Scheme Based on Viterbi Algorithm

This letter proposes a novel improved differential space-time block code (DSTBC) scheme. By introducing a specific redundancy mechanism, the proposed DSTBC encoder behaves as a second-order discrete Markov process that we model by a multilevel trellis diagram. At the receiver side, the well-known Viterbi algorithm is applied without channel state information (CSI). The new scheme completely compensates for the 3-dB penalty, over wide SNR range, noticed in conventional DSTBC scheme and shows a closer performance to coherent STBC.

Performance Analysis of DSTBC over VHF Air-to-Ground Communication Channels

This paper is concerned with evaluating the performance of differential space time block coding (DSTBC) over very high frequency (VHF) aeronautical communication channels (i.e. air-to-ground). Differential phase shift key (DPSK) is one of the differential transmission schemes that transmit information without full channel state information (CSI) at the receiver. There are two main problems that degrade the performance of the communication over this channel, multipath fading which is a common problem in any wireless channel and Doppler shifts which result from aircraft speeds. In order to combat such fading and improve the bit error rate (BER) performance of the communication system over this channel, the paper investigated the usage of multiple input multiple output (MIMO) systems with differential transmission scheme. This was done through computer simulations that analyze the performance of DSTBC using two antennas at the transmitter and N antennas at the receiver. General Terms Wireless communication, multi antenna system.

Multi-amplitude Differential Space-time Block Coding Scheme for Square/Non-Square Code Matrix in MIMO Systems

Differential space-time coding (DSTC) technique has become a good choice when channel estimations are difficult to obtain in multiple antennas system. On the basis of analyzing the existing DSTC schemes, by introducing multi - level quadrature amplitude modulation (MQAM) and matrix transform method, we develop a multi - amplitude differential space-time block coding (STBC) scheme for square or non-square code matrix in MIMO systems , and give the derivation of calculation formula e of the coding advantage in detail. The developed scheme can effectively avoid the performance loss of conventional DSTC schemes based on PSK modulation (i.e. single amplitude DSTC) in high spectrum efficiency . It can be applied to non-square code matrix case , and thus overcomes the shortcoming that existing DSTC schemes are only suit able for square code matrix. Compared with single amplitude DSTC schemes, our scheme has higher spectrum efficiency by carrying information not only on phases but also on amplitudes. Moreover, our scheme has linear decoding complexity, higher coding advantage, and higher code rate for more than two antennas. The simulations results show that the proposed scheme can provide lower BER than the existing single amplitude differential STBC schemes for both square and non-square code matri ces .

Coherent Versus Noncoherent

In this article, we investigate the design philosophies of the existing space-time (ST) block codes (STBCs) in the open literature, namely the orthogonal approach and layered method, followed by the introduction of the generalized linear dispersion architecture. We will demonstrate that the powerful linear dispersion structure is capable of unifying the entire suite of existing schemes and, as a further benefit, it offers extra design flexibility so that diverse system requirements can be satisfied. Furthermore, after characterizing the fundamental relationship between STBCs and differential STBCs (DSTBCs), we highlight the benefits of noncoherently detected schemes, which are capable of exploiting the advantages of multiple antennas, while circumventing the potentially excessive burden of multiantenna channel estimation. Additionally, the linear dispersion structure can also be applied in systems, where the multiantenna array is formed in a distributed fashion by multiple single-antenna-aided cooperating mobile stations. Hence, the design of colocated and cooperative multiple-input-multiple-output (MIMO) systems aiming for achieving diversity is linked from a linear dispersion perspective.

Multiple-Symbol Differential Sphere Detection Aided Differential Space-Time Block Codes Using QAM Constellations

We propose Multiple-Symbol Differential Detection (MSDD) aided Differential Space-Time Block Codes (DSTBCs) using QAM. Our solution eliminates the requirement of high-complexity MIMO channel estimation and its pilot overhead, while mitigating the potential performance degradation of noncoherent receivers in fast fading channels. Additionally, we develop Multiple-Symbol Differential Sphere Detection (MSDSD) for the QAM aided DSTBC schemes advocated, in order to circumvent their potentially excessive complexity.

A Differential MIMO SC-FDE Transceiver Design over Multipath Fast Fading Channels

In this paper, we propose a new differential MIMO single-carrier system with frequency-domain equalization (SC-FDE) aided by the insertion of cyclic prefix. This block transmission system not only inherits all the merits of the SISO SC-FDE system, but is also equipped with a differential space-time block coding (DSTBC) such as to combat the fast-changing frequency selective fading channels without the needs to estimate and then compensate the channel effects. Hence, for practical applications, it has the additional merits of decoding simplicity and robustness against high mobility transmission environments. Computer simulations show that the proposed system can provide diversity benefit as the non-differential system does, while greatly reducing the receiver complexity.

Iterative Noncoherent Receiver for Differential STBC in Fast Fading Channels

An iterative noncoherent receiver that does not exploit channel statistics is proposed for the detection of differential space-time block codes (DSTBCs) in fast-fading channels. For robustness to channel variation, it employs an iterative architecture incorporating <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> information from a channel decoder in the Viterbi detection. Computer simulation shows that the performance of this iterative scheme is comparable with that of ideal coherent detection as the number of iterations increases.

Error Probability Bounds of Concatenated Channel Codes and Differential Space-Time Block Codes

In this letter, we analyze the performance of a class of multiple-antenna systems which concatenate channel codes, e.g., trellis coded modulation (TCM), and differential orthogonal space-time block codes (DOSTBC). Assuming no channel state information (CSI), tight performance bounds for bit and frame error rates are provided under block Rayleigh fading channel. Simulation results are also provided which confirm the accuracy of analytical findings.

Differential coding for non-orthogonal space-time block codes with non-unitary constellations over arbitrarily correlated rayleigh channels

In this paper, we propose a maximum likelihood (ML) decoder for differentially encoded full-rank square nonorthogonal space-time block codes (STBCs) using unitary or non-unitary signal constellations, which is also applicable to full-ranked orthogonal STBC (OSTBC). As the receiver is jointly optimized with respect to the channel and the unknown data, it does not require any knowledge of channel power, signal power, or noise power to decode the signal, and the decision is purely based on two consecutively received data blocks. We analyze the effect of channel correlation on the performance of the proposed system in Rayleigh fading channels. Assuming a general correlation model, an upper bound of the pair-wise error probability (PEP) of the differential OSTBCs is derived. An approximate bound of the PEP for the differential nonorthogonal STBCs is also derived. We propose a precoder designing criterion for differential STBC over arbitrarily correlated Rayleigh channels. Precoding improves the system performance over the correlated Rayleigh MIMO channels. Our precoded differential codes differ from the previously proposed precoder designs for differential OSTBC in the following ways: 1) We propose a precoder design for arbitrarily correlated Rayleigh channels, whereas the previous work considers only for transmit correlation. 2) The previous work is only applicable to the OSTBCs with PSK constellations, whereas our precoder is applicable to any type of full-rank square STBCs with unitary and non-unitary signal constellations.

Macro-Diversity Scheme for a Point-to-Multipoint Communication System by means of D-STBC Method in Fast Fading Environment

In recent years, the space-time block coding (STBC) method has attracted attention to provide transmission diversity in mobile communication systems. Although the STBC method is very effective in slow fading environments, its performance in fast fading environments has yet to be clearly verified. In this paper we propose a railway radio communication system using space-time coding in cooperation with two base stations. Here, we considered the differential STBC (D-STBC) method in railway communication system to overcome difficulties caused by the fast fading environment. We have compared the performance of STBC and D-STBC method where there is frequency offset between two base stations. Moreover, we have presented the simulation result of overall performance of the system including frequency offset and transmission time delay when operating D-STBC method. The overall evaluation on this paper shows that the D-STBC method is suitable for realizing highly reliable railway communication systems.

Quadrature Amplitude Modulation for Differential Space-Time Block Codes

Differential Space-Time Block Codes (DSTBC) do not require any radio channel measurement and channel state information neither on the transmitter nor at the receiver side. Therefore, they are an attractive alternative to coherent Multiple-Input Multiple-output (MIMO) systems. The classical technical proposal for differential techniques is based on M-ary phase shift keying (M-PSK) modulation schemes for DSTBC (PSK-DSTBC). One advantage of this scheme is the constant envelop of the transmit signal, but it is well known that higher-order PSK is less efficient due to the small distance between adjacent points in the constellation diagram. Therefore, in this paper an alternative modulation technique for DSTBC is discussed, which is based on quadrature amplitude modulation (QAM-DSTBC). The signal envelope of the transmit signal is not any more constant in this case. Therefore, the technical challenge of integrating QAM into the DSTBC system design is to control the transmit power in order to avoid an increase or a decrease in transmit power to some extreme values. The mechanism, which is used in this paper to control the transmit power is based on an extension of the original QAM constellation diagram. The additional points, which are integrated into the constellation diagram are used in this case for the mapping procedure to select one of the modulation symbols with high or alternatively low signal power. This means for each single bit pattern there are almost always two modulation symbols available in the mapping procedure one with low and one with high signal power, which gives the basis for a signal power control algorithm. The resulting bit-error-rate (BER) performance of QAM-DSTBC is compared finally to the performance figures of the original proposal of PSK-DSTBC.

BER analysis of MPSK space-time code with differential detection over correlated block-fading Rayleigh channel

MIMO technology proposed in recent years can effectively combat the multipath fading of wireless channel and can considerably enlarge the channel capacity, which has been investigated widely by researchers. However, its performance analysis over correlated block-fading Rayleigh channel is still an open and challenging objective. In this article, an analytic expression of bit error rate (BER) is presented for multiple phase shift keying (MPSK) space-time code, with differential detection over correlated block-fading Rayleigh channel. Through theoretical analysis of BER, it can be found that the differential space-time scheme without the need for channel state information (CSI) at receiver achieves distinct performance gain compared with the traditional nonspace-time system. And then, the system simulation is complimented to verify the above result, showing that the diversity system based on the differential space-time block coding (DSTBC) outperforms the traditional nonspace- time system with diversity gain in terms of BER. Furthermore, the numerical results also demonstrate that the error floor of the differential space-time system is much lower than that of the differential nonspace-time system.

An Efficient Differential MIMO-OFDM Scheme with Coordinate Interleaving

We propose a concatenated trellis code (TC) and coordinate interleaved differential space-time block code (STBC) for OFDM. The coordinate interleaver, provides signal space diversity and improves the codeword error rate (CER) performance of the system in wideband channels. Coordinate interleaved differential space-time block codes are proposed and used in the concatenated scheme, TC design criteria are derived, and the CER performances of the proposed system are compared with existing concatenated TC and differential STBC. The comparison showed that the proposed scheme has superior diversity gain and improved CER performance.

A New Design of Differential Space-Time Block Code Allowing Symbol-Wise Decoding

For four (or more) transmitters, a new design of differential space-time block code allowing symbol-wise decoding is presented in this letter. The new design not only has the minimum (symbol-wise) decoding complexity as that by Yuen, Guan and Tjhung (YGT) but also yields a lower error rate. While the YGT code uses a specially designed symbol constellation, the new code uses a conventional QAM with a rotation. At a high data rate such as 3 bps/Hz, the new design with symbol-wise decoding complexity can even yield a lower error rate than the code by Zhu and Jafarkhani that has the pair-wise decoding complexity.

Multi-Chip Differential Space-Time Block Coding for DS-CDMA

In this letter, we propose a novel space-time coding scheme for fast time-variant direct-sequence code-division multiple access (DS-CDMA) channels. The proposed scheme employs multi-chip differential space-time block coding (MC-DSTBC) and robustness against fast fading is further improved by low-complexity decision-feedback differential detection (DF-DD). Both analytical and simulation results show in good agreement the excellent performance of the novel design in fast time-variant channels.

MLSE Detection with Blind Linear Prediction for Differential Space-Time Block Code Systems

This paper proposes a maximum likelihood sequence estimation (MLSE) for the differential space-time block code (DSTBC) in cooperation with blind linear prediction (BLP) of fast frequency-flat fading channels. This method that linearly predicts the fading complex envelope derives its linear prediction coefficients by the method of Lagrange multipliers, and does not require data of decision-feedback or information on the channel parameters such as the maximum Doppler frequency in contrast to conventional ones. Computer simulations under fast fading conditions demonstrate that the proposed method with an appropriate degree of polynomial approximation is superior in BER performance to the conventional method that estimates the coefficients by the RLS algorithm using a training sequence.