Vertical Bell Laboratories Layered Space-Time Architecture Research Articles

Frequency-Domain Block Signal Detection for Single-Carrier Transmission

One-tap frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can significantly improve the bit error rate (BER) performance of single-carrier (SC) transmission in a frequency-selective fading channel. However, a big performance gap from the theoretical lower bound still exists due to the presence of residual inter-symbol interference (ISI) after MMSE-FDE. In this paper, we point out that the frequency-domain received SC signal can be expressed using the matrix representation similar to the multiple-input multiple-output (MIMO) multiplexing and therefore, signal detection schemes developed for MIMO multiplexing, other than simple one-tap MMSE-FDE, can be applied to SC transmission. Then, for the reception of SC signals, we propose a new signal detection scheme, which combines FDE with MIMO signal detection, such as MMSE detection and Vertical-Bell Laboratories layered space-time architecture (V-BLAST) detection (we call this frequency-domain block signal detection). The achievable average BER performance using the proposed frequency-domain block signal detection is evaluated by computer simulation.

Cross-layer analysis of downlink V-BLAST MIMO transmission exploiting multiuser diversity

We develop a queuing analytic model to study cross-layer effects on quality of service (QoS) performance for downlink transmission in a Vertical Bell Laboratories Layered Space-Time Architecture (V-BLAST) multiple input multiple output (MIMO) wireless system exploiting multiuser diversity. As in multiuser single input single output (SISO) systems, multiuser diversity has been shown to have a great potential in improving system throughput in multiuser MIMO systems as well. In a V-BLAST MIMO system, the transmit antennas can carry parallel streams and multiple users can be scheduled for transmissions at the same time. We consider a multiuser diversity scheme that can effectively exploit this extra dimension in multiuser scheduling. To investigate the cross-layer aspect of the performance improvement, we perform a queuing analysis to derive buffer statistics, queuing delay distribution, packet throughput and loss rate experienced in the data link layer when this multiuser diversity technique is deployed in the system. We also present selected numerical results to show how the queuing model can help us to relate these important QoS measures to relevant physical layer and traffic parameters. Usefulness of the developed analytical model is also demonstrated through example applications.

Low-complexity systolic V-BLAST architecture

In multiple-input multiple-output systems, an ordered successive interference canceller, termed the vertical Bell laboratories layered space-time (V-BLAST) algorithm, offers good performance. This letter presents a low-complexity V-BLAST scheme suited for parallel implementation. The proposed scheme, using a greedy ordering, can achieve a performance comparable to that of V-BLAST with optimum ordering, while its computational complexity is lower than a linear detector.

Euclidean Geometry LDPC-VBLAST System Design and Performance Evaluation

Among popular multi-transmit and multi-receive antennas techniques, the VBLAST (Vertical Bell Laboratories Layered Space-Time) architecture has been shown to be a good solution for wireless communications applications that require the transmission of data at high rates. Recently, the application of efficient error correction coding schemes such as low density parity-check (LDPC) codes to systems with multi-transmit and multi-receive antennas has shown to significantly improve bit error rate performance. Although irregular LDPC codes with non-structure are quite popular due to the ease of constructing the parity check matrices and their very good error rate performance, the complexity of the encoder is high. Simple implementation of both encoder and decoder can be an asset in wireless communications applications. In this paper, we study the application of Euclidean geometry LDPC codes to the VBLAST system. We assess system performance using different code parameters and different numbers of antennas via Monte-Carlo simulation and show that the combination of Euclidean geometry LDPC codes and VBLAST can significantly improve bit error rate performance. We also show that interleaving data is necessary to improve performance of LDPC codes when a higher number of antennas is, used in order to mitigate the effect of error propagation. The simplicity of the implementation of both encoder and decoder makes Euclidean geometry LDPC codes with VBLAST system attractive and suitable for practical applications.

MIMO-OFDM Based Evolution Schemes for DPC-OF/TDMA

During these years we have been focusing on developing ultra high-data-rate wireless access systems. One of such kind of systems is called DPC-OF/TDMA [2]-[4] (dynamic parameter controlled orthogonal frequency and time division multiple access) which targets at data rates beyond 100 Mbps. In order to support higher data rates, e.g., several hundreds of mega bps or even giga bps, it is necessary to evolve DPC-OF/TDMA on MIMO-OFDM (multiple-input multiple-output orthogonal frequency division multiplexing) platform. In this paper, we propose two MIMO-OFDM evolution schemes for DPC-OF/TDMA: Ml scheme and M2 scheme. Ml scheme is based on the combination of V-BLAST (vertical Bell laboratories layered space-time architecture) and OFDM. It invests all transmit antennas on multiplexing while exploits no diversity in the transmitter. M2 scheme is based on multi-layer space-time block coded OFDM (multi-layer STBC OFDM). This scheme achieves a good compromise between multiplexing and diversity in the transmitter. We conduct exhaustive simulations for 4x4, 4×6. 4x8, 6×6. 6×8. and 8x8 systems. We are assured that both evolution schemes are very promising in supporting several hundreds of mega bps data rates. Moreover, we find that each evolution scheme has its own prevailing area. When the receive diversity order is limited, M2 scheme has better performance since it embeds transmit diversity; as the receive diversity order increases, the performance gap between the two schemes shrinks and finally Ml scheme prevails in performance. Therefore, the proper choice depends on the system configuration, i.e., how many transmit and receive antennas are used.

Transmit Power Allocation for a Modified V-BLAST System

In this letter, we present a modification of Vertical Bell Laboratories Layered Space-Time (V-BLAST), and propose an effective transmit power allocation (TPA) scheme for the modified system. The proposed TPA scheme minimizes the uncoded bit-error rate (BER) averaged over all detection stages, and requires small feedback overhead. Simulation results show that the modified V-BLAST system with the proposed TPA scheme provides a significant reduction in the uncoded BER compared with the conventional V-BLAST system. When the minimum mean-square error nulling is adopted, the modified V-BLAST system is found to achieve the uncoded BER performance comparable to that of the maximum-likelihood detection for the conventional V-BLAST architecture.