Multiple-input Multiple-output Transmission Modes Research Articles

Adaptive Transmission Based on MIMO Mode Switching Over Malaga Turbulence Channel With Pointing Error

In this paper, we propose a dynamic adaptive multiple input multiple output (MIMO) free space optical (FSO) system with spatial mode switching. Based on the channel conditions, the proposed system can select different MIMO transmission modes: diversity, multiplexing or hybrid mode that yields the maximum average channel capacity while satisfying the reliable average bit error rate (BER). Considering the combined effects of path loss, pointing error and atmospheric turbulence-induced fading modeled by Malaga distribution, we derive the closed-form expressions of average channel capacity and average BER of MIMO system for each transmission mode. From adaptive system performance evaluated results, we establish the signal-to-noise ratio (SNR) threshold look-up table (LUT) in different scenarios to select the optimal transmission mode. The extensive numerical results demonstrate that the proposed adaptive system has a significant improvement in average channel capacity compared with each stand-alone mode system. Finally, Monte Carlo simulation is also provided to verify the correctness of the proposed adaptive scheme and conclusions.

Error Rate Performance Investigations of MIMO Transmission Modes through Nakagami-m Fading Channels

In the field of wireless communication systems, the use of multiple antennas at the transmitter and receiver side has gained a huge popularity over the past few decades, due to its tremendous performance enhancing capabilities. Such systems are known as MIMO (Multiple-Input Multiple-Output) systems and can be classified into three main categories; Spatial Multiplexing, Spatial Diversity and Beam forming techniques. The objective of this paper is to evaluate the error rate performance of MIMO transmission modes through Nakagami-m fading channels. The ZF (Zero Forcing), MMSE (Minimum Mean-Square-Error) channel equalization algorithm; STTC (Space Time Trellis Codes), OSTBC (Orthogonal Space Time Block Codes), MRC (Maximal Ratio Combining) and Beamforming methods are analyzed. The QPSK modulation technique is used to evaluate the bit error rate (BER) performances under different SNR scenarios. The results described in this paper suggest considerable improvement in the system performance by incorporating different MIMO techniques in order to improve the wireless transmission link quality.

Routing, spectrum access, and scheduling in multi-hop multi-channel wireless networks with MIMO links

Software-defined radios (SDRs) are a promising technology to enable dynamic channel access and sharing. Multiple Input Multiple Output (MIMO) is another radio technology breakthrough for increasing wireless network capacity. To obtain the full benefits brought by the SDR and MIMO technologies in wireless mesh networks (WMNs), the higher layer mechanisms should exploit their capabilities in a systematic way. In this paper, we investigate routing, channel assignment, link scheduling, and MIMO transmission mode control in multi-channel multi-antenna wireless mesh networks. We first present a cross-layer framework for network performance optimization. Network traffic routing is established on a relatively long time scale to maintain system stability. We then proposed a stream controlled multiple access (SCMA) scheme, which is responsible for assigning frequency channels and scheduling links for data transmission and controlling MIMO transmission modes. It enables efficient spectrum access and sharing in time, frequency, and space, and adapts to varying network conditions. The evaluation results show that the proposed scheme greatly improves network performance compared to the traditional schemes.

Energy-Efficient Adaptive Virtual MIMO Transmission in a Transmit-Side Correlated Wireless Sensor Network

In this paper, performances of two different virtual multiple-input multiple-output (MIMO) transmission schemes — spatial multiplexing (SM) and space-time block coding (STBC) — in a correlated wireless sensor network are analyzed. By utilizing a complex Wishart distribution, we investigate the statistical properties of a correlated virtual MIMO channel between the sensors and data collector that is used in the performance analysis of each MIMO transmission mode. Distributed sensors then transmit their data cooperatively to the data collector by choosing a proper transmission mode adaptively based on the channel conditions and spatial correlation among the sensors. Furthermore, after analyzing the energy efficiencies of SM and STBC, we propose a new energy efficient mode switching rule between SM and STBC. Finally, by analytically deriving the required transmit energy of the proposed adaptive transmission scheme, the manner in which the spatial correlation influences the energy consumption is shown. This suggests a cooperating node scheduling protocol that makes energy consumption less sensitive to the variation of the spatial correlation.

A Next Generation Wireless Simulator Based on MIMO-OFDM: LTE Case Study

The complexity of next generation wireless systems is growing exponentially. The combination of Multiple-Input Multiple-Output (MIMO) technology with Orthogonal Frequency Division Multiplexing (OFDM) is considered as the best solution to provide high data rates under frequency-selective fading channels. The design and evaluation of MIMO-OFDM systems require a detailed analysis of a number of functionalities such as MIMO transmission modes, channel estimation, MIMO detection, channel coding, or cross-layer scheduling. In this paper we present a MIMO-OFDM-based simulator that includes the main physical and link layer functionalities. The simulator has been used to evaluate the performance of the 3GPP Long-Term Evolution (LTE) technology for different MIMO-OFDM techniques under realistic assumptions such as user mobility or bandwidth-limited feedback channel.