The Behaviour of Vertical Bell Laboratories Layered Space-Time Algorithm Combined with Multiuser Detection Schemes in Wireless Communication System

This paper provides the performance analysis of multiuser Vertical Bell Laboratories Layered Space-Time (V-BLAST) system receiver structures for Multiple-input Multiple-Output (MIMO) channel at a base station with assumption of perfect channel estimation and perfect timing delay estimation. In MIMO channels the receivers such as decorrelator, Minimum Mean Square Error (MMSE) and Multistage Parallel Interference Cancellation (MPIC) receiver outperform the conventional receiver. Withal, since the multiple antenna interference led to a strong impact on the performance degradation of a multistage interference cancellation receiver, the performance of MPIC receiver was highly degraded based on system loading.

V-BLAST BASED LDPC-CODED RELAY COOPERATION

An efficient LDPC-coded multi-relay cooperation architecture is proposed based on virtual vertical Bell Labs layered space-time （V-BLAST） processing for uplink communication, where minimum-mean-square-error （MMSE） and BP-based joint iterative decoding based on the introduced muhi-layer Tanner graph are effectively de- signed to detect and decode the corrupted received sequence at the destination. By introducing V-BLAST transmis- sion to the coded multi-relay cooperation, relays send their streams of symbols simultaneously, which increases the data rate and significantly reduces the transmission delay. The theoretical analysis and numerical results show that the new LDPC coded cooperation scheme outperforms the coded non-cooperation under the same code rate, and it also achieves a good trade-off among the performance, signal delay, and the encoding complexity associated with the number of relays. The performance gain can be credited to the proposed V-BLAST processing architecture and BP-based joint iterative decoding by the introduced multi-layer Tanner graph at a receiver-side.

BLIND MULTIUSER DETECTION FOR V-BLAST CODED MULTICARRIER CDMA SYSTEM

Focusing on the space-time coded multiuser mobile communication systems in the frequency-selective fading environment, this paper proposes a Vertical Bell labs LAyered Space-Time (V-BLAST) coded Multicarrier Code-Division Multiple-Access (MC-CDMA) scheme and its blind channel identification algorithm. This algorithm employs an ESPRIT-like method and the singular value decomposition, and the channels between every transmit antenna of every user and every receive antenna of the base station are blindly estimated with a closed-form solution. Based on it, an equivalent Minimum Mean-Squared Error (MMSE) time-domain multiuser detector is derived. Moreover, the proposed scheme exploits the precoding in the transmitter in order to eliminate the constraint of more receive antennas than transmit ones, required by most conventional V-BLAST codec schemes. Computer simulation results demonstrate the validity of this proposed scheme.

AN IMPROVED AND EFFICIENT DETECTION SCHEME FOR V-BLAST SYSTEMS WITH QAM MODULATION

The paper proposed an improved Ordered Successive Interference Cancellation(OSIC) detection scheme for V-BLAST systems with square/rectangular Quadrature Amplitude Modulation(QAM) modulation.It utilizes an equivalent real-valued vector expression of relationship between transmit signals and received signals,exploits the constellation's product-form structure and can eventually make the order,in which components of the transmit signals vector are extracted,more "optimal" in some sense.Thereby,it can offer an improved error probability as compared to the conventional OSIC detection scheme.In addition,the paper also proposes an efficient projection al-gorithm to calculate nulling vectors in a simple recursive fashion in order to avoid the vast increase of complexity,which is due to the fact that the original complex N -dimensional data vector and M×N channel matrix are transformed into a real 2N -dimensional data vector and a real 2M ×2N channel matrix respectively.A scrutinous complexity analysis shows that the complexity increases by only 33% as compared to the conventional scheme.

Symbols detection for frequency-selective V-BLAST OFDM systems

As the combining form of the orthogonal frequency-division multiplexing (OFDM) technique and the vertical Bell Labs layered space-time (V-BLAST) architecture, the V-BLAST OFDM system can better meet the demand of next-generation (NextG) broadband mobile wireless multimedia communications. The symbols detection problem of the V-BLAST OFDM system is investigated under the frequency-selective fading environment. The joint space-frequency demultiplexing operation is proposed in the V-BLAST OFDM system. Successively, one novel half-rate rotational invariance joint space-frequency coding scheme for the V-BLAST OFDM system is proposed. By elegantly exploiting the above rotational invariance property, we derive one direct symbols detection scheme without knowing channels state information (CSI) for the frequency-selective V-BLAST OFDM system. Extensive simulation results demonstrate the validity of the novel half-rate rotational invariance joint space-frequency coding scheme and the performance of the direct symbols detection scheme.

AN ENHANCED DETECTION ALGORITHM FOR V-BLAST SYSTEM

A decoding method complemented by Maximum Likelihood (ML) detection for V-BLAST (Verti- cal Bell Labs Layered Space-Time) system is presented. The ranked layers are divided into several groups. ML decoding is performed jointly for the layers within the same group while the Decision Feedback Equalization (DFE) is performed for groups. Based on the assumption of QPSK modulation and the quasi-static flat fading channel, simulations are made to testify the performance of the proposed algorithm. The results show that the algorithm outperforms the original V-BLAST detection dramatically in Symbol Error Probability (SEP) per- formance. Specifically, Signal-to-Noise Ratio (SNR) improvement of 3.4dB is obtained for SEP of 10?2 (4×4 case), with a reasonable complexity maintained.

Optimal MMSE successive interference cancellation in group-wise STBC MIMO systems

An optimal minimum mean square error successive interference cancellation （OMMSE SIC） scheme for Groupwise space-time block coding （G-STBC） multiple-input multiple-output （MIMO） systems is presented. In such a system, transmit antennas are partitioned into several STBC encoding groups and each group transmits independent data stream which is individually STBC encoded. On the receiver side, by exploring the temporal constraint provided by STBC, an equivalent channel model similar to the one in standard vertical Bell laboratories layered space-time （V-BLAST） systems is generated. Then OMMSE SIC algorithm is performed to detect all the transmitted information. Simulation compares the proposed scheme with non-ordering MMSE SIC scheme and the corresponding equal data rate scheme in V-BLAST systems with the same receive antennas＇ number. Result shows that the proposed scheme has better performance than non-ordering MMSE SIC scheme and by introducing more transmit antennas and adopting the OMMSE SIC scheme, better performance also can be achieved than corresponding V-BLAST systems.

Successive interference cancellation (SIC) in V-BLAST systems with asynchronous transmission mode

The V-BLAST system with asynchronous transmission mode first proposed by Shao can achieve full diversity only by using a simple linear detection scheme under zero forcing （ZF） criterion; therefore it gives a reasonable tradeoff between complexity and performance. In this paper, we propose two types of successive interference cancellation （SIC） detection schemes for the asynchronous V-BLAST system, one is characterized by applying Mr successive interference cancellators before a maximal ratio combiner （where Mr is the number of receive antennas）, and the other has a maximal ratio combiner before a successive interference cancellator. Since Type Ⅰ consumes more energy of the previously detected signals to recover a signal, Type Ⅱ can offer a better performance and simulations demonstrate its validity.

Transmit Antenna Selection with Power and Rate Allocation for Spatial Multiplexing in Distributed Antenna Systems

High spectral efficiency distributed antenna systems （DAS） require vertical Bell-Labs layered space-time （V-BLAST） like spatial multiplexing schemes. However, unlike normal point-to-point multiple input multiple output （MIMO） channels, DAS channels have different large-scale fadings from different transmit antennas, thus making equal power and rate transmission that is feasible in MIMO channels unrealistic in DAS channels. This paper proposes a novel transmit antenna selection scheme with power and rate allocation. The scheme is based on large-scale fading （shadow fading and path loss） and is suitable for VBLAST structures with zero-forcing and successive interference cancellation （ZF-SIC） receivers, ensuring balanced average symbol error rate （SER） performance in each layer. On the receiver side, a fixed detection order is used, which is obtained in the transmit antenna selection process. Simulation results show that the proposed scheme gives good performance gains over equal power and rate transmission systems without antenna selection.