This paper proposes a practical throughput upper bound that considers physical layer techniques using adaptive modulation and coding (AMC) for orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) multiplexing. The proposed upper bound is computed from the modulation and coding scheme (MCS) that provides the maximum throughput considering the required block error rate (BLER) at the respective received signal-to-noise power ratios as a constraint. Then, based on the practical throughput upper bound, we present the causes of impairment for selecting the best MCS based on the computed mutual information for OFDM MIMO multiplexing. More specifically, through the evaluations, we investigate the effect of MCS selection error on an increasing maximum Doppler frequency due to the round trip delay time and the effect of channel estimation error of maximum likelihood detection associated with reference signal based channel estimation.

In the next generation mobile communication systems, multiple-input multiple-output (MIMO) multiplexing is an indispensable technique to achieve very high-speed data transmission with a limited bandwidth. In MIMO multiplexing, it is necessary to estimate the channels between transmit and receive antennas for signal detection. In this paper, we propose a minimum mean square error (MMSE) channel estimation using cyclic delay pilot for single-carrier (SC)-MIMO multiplexing. In the proposed channel estimation, the same pilot block is altered through the addition of different cyclic delays and transmitted from different antennas at the same time for simultaneous estimation of all channels between transmit and receive antennas. We evaluate by computer simulation the bit error rate (BER) performance of MIMO multiplexing using the proposed channel estimation and compare it to those using time-multiplexed pilot based channel estimation (TMP-CE) and code-multiplexed pilot based channel estimation (CMP-CE).

Very high-speed data services are demanded in the next generation wireless systems. However, the available bandwidth is limited. The use of multi-input multi-output (MIMO) multiplexing can increase the transmission rate without bandwidth expansion. For high-speed data transmission, however, the channel becomes severely frequency-selective and the achievable bit error rate (BER) performance degrades. In our previous work, we proposed the joint use of iterative frequency-domain parallel interference cancellation (PIC) and two-dimensional (2D) MMSE-FDE for the non-spread single-carrier (SC) transmission in a frequency-selective fading channel. The joint use of PIC and 2D MMSE-FDE can effectively suppress the inter-path interference (IPI) and the inter-code interference (ICI), resulting from the channel frequency-selectivity, and the interference from other antennas simultaneously. An iterative PIC with 2D MMSE-FDE has a high computational complexity. In this paper, to well suppress the interference from other antennas while reducing the computational complexity, we propose to replace 2D MMSE-FDE by 1D MMSE-FDE except for the initial iteration stage and to use multicode spread-spectrum (SS) transmission instead of the non-spread SC transmission. The BER performance of the proposed scheme in a frequency-selective Rayleigh fading channel is evaluated by computer simulation to show that the proposed scheme can basically match the BER performance of 2D MMSE-FDE with lower complexity.

In mobile communications, the channel consists of many resolvable paths with different time delays, resulting in a severely frequency-selective fading channel. The frequency-domain equalization (FDE) can take advantage of the channel selectivity and improve the bit error rate (BER) performance of the single-carrier (SC) transmission. Recently, multi-input multi-output (MIMO) multiplexing is gaining much attention for achieving very high speed data transmissions with the limited bandwidth. Eigenbeam space division multiplexing (E-SDM) is known as one of MIMO multiplexing techniques. In this paper, we propose frequency-domain SC E-SDM for SC transmission. In frequency-domain SC E-SDM, the orthogonal transmission channels to transmit different data in parallel are constructed at each orthogonal frequency. At a receiver, FDE is used to suppress the inter-symbol interference (ISI). In this paper, the transmit power allocation and adaptive modulation based on the equivalent channel gains after performing FDE are applied. The BER performance of the frequency-domain SC E-SDM in a severe frequency-selective Rayleigh fading channel is evaluated by computer simulation.

In this paper, iterative adaptive soft parallel interference canceller (ASPIC) is proposed for turbo coded multiple-input multiple-output (MIMO) multiplexing. ASPIC is applied to transform a MIMO channel into single-input multiple-output (SIMO) channels for maximum ratio diversity combining (MRC). In the ASPIC, replicas of the interference are generated and subtracted from the received signals. For the generation of replicas with higher reliability, iterative ASPIC is proposed. It performs the iterative interference cancellation by feedback of the log-likelihood ratio (LLR) sequence obtained as the turbo decoder output. For iterative ASPIC, at the transmitter, the information sequence and parity sequence are transmitted from different antennas. In this paper, the achievable bit error rate (BER) performance, in a Rayleigh fading channel, for the turbo coded MIMO multiplexing with the proposed iterative ASPIC system is evaluated by computer simulation.