Indoor MIMO Channel Research Articles

Dynamic Metasurface Antennas for Higher-order MIMO Systems in Indoor Environments

We propose a MIMO system using a dynamic cavity-backed metasurface antenna (DMA) as a transmit antenna to improve the channel capacity of indoor MIMO channels. The DMA is a printed cavity loaded with tunable metamaterial radiators and fed by radio frequency ports. The DMA can generate radiation patterns that are adaptive to MIMO channels by individual tuning of the metamaterial radiators. In this letter, we study a 4 $\times $ 4 MIMO system operating at 5.9 GHz, consisting of a simulated DMA as transmit antenna and a linear dipole array as receive antenna. Using a ray tracing technique, we simulate indoor MIMO channels and compute MIMO channel capacity at different receiver locations. We demonstrate that the adaptive radiation pattern generated by the DMA can increase the channel capacity. The MIMO system using the DMA can be low cost and low in power consumption, and can find applications where bandwidth, power, and cost represent constraints.

Performance Evaluation of Virtual MIMO Multi-User System in a Measured Indoor Environment at 5 GHz

Wideband indoor MIMO channel measurements were performed in office building with carrier frequency at 5.25 GHz with 100 MHz radio frequency bandwidth. In this paper nineteen measured indoor propagation data sets are used to study the behavior of virtual MIMO system formed by two users compared to its classical user. A classical user having 4 antenna elements, two spaced antennas from two classical users are brought together to form 4 $$\times $$× 8 virtual MIMO with base station having 8 antennas. Nineteen measured datasets are available from which 171 possible virtual MIMO pairs are formed. The capacity, $$K$$K-factor, rms delay spread and spatial correlation are evaluated for 171 possible pairs of users whose channels were measured while standing. The results show that virtual MIMO in many cases is desirable for capacity improvement. The capacity improvement of virtual MIMO system is found to be 60.2 % over both two constituent users and 31 % over only one constituent user. The result show also that capacity improvement is mostly due to the rms delay spread and special correlation reduction than the $$K$$K-factor reduction.

Frequency Characterization of a Polarized UWB MIMO Channel at 3.5 GHz in an Indoor Environment

In this paper, frequency characterization of a UWB indoor MIMO channel is presented. Measurements were conducted on a 4×4 MIMO channel within the frequency range of 2 to 5 GHz with a fixed SNR of 30dB. The impact of antenna polarization on the mutual information was also analyzed with antennas interelement spacing fixed at 2λ. Channel capacity was analyzed both in NLOS and LOS scenarios. It is realized that the spectral efficiency of the channel is a function of the operating frequency and the channel bandwidth.

Research on Improvement of the Next Generation IEEE802.11ac Channel Model

Based on the special correlation of antennas and the power delay profile (PDP) of the cluster model, six models of A-F have been established by the TGn task-group in total. On the basis of the new broadband wireless local area network (WLAN) standard--IEEE 802.11ac with larger bandwidth and multi-user requirements drawn up by the TGac task-group, in this paper, the IEEE 802.11ac channel model is set up by means of improving and simulating the indoor MIMO channel.

Performance Evaluation of Closed-Loop Spatial Multiplexing Codebook Based on Indoor MIMO Channel Measurement

Closed-loop MIMO technique standardized in LTE can support different layer transmissions through precoding operation to match the channel multiplexing capability. However, the performance of the limited size codebook still needs to be evaluated in real channel environment for further insights. Based on the wideband MIMO channel measurement in a typical indoor scenario, capacity loss (CL) of the limited size codebook relative to perfect precoding is studied first in two extreme channel conditions. The results show that current codebook design for single layer transmission is nearly capacity lossless, and the CL will increase with the number of transmitted layers. Furthermore, the capacity improvement of better codebook selection criterions is very limited compared to CL. Then we define the maximum capacity boost achieved by frequency domain layer adaption (FDLA) and investigate its sensitivity to SNR and channel condition. To survey the effect of frequency domain channel variation on MIMO-OFDM system, we define a function to measure the fluctuation levels of the key channel metrics within a subband and reveal the inherent relationship between them. Finally, a capacity floor resulted as the feedback interval increases in frequency domain.

Effect of Polarization on the Correlation and Capacity of Indoor MIMO Channels

We describe a simple multiple-input/multiple-output (MIMO) channel measurement system for acquiring indoor MIMO channel responses. Four configurations of the polarization diversity antenna, referred to asVVV,YYH,YVYandVHH, were studied in terms of the capacity of indoor MIMO systems. Measurements were taken for a3×3MIMO system in the 2.4 GHz band. In addition, the channel capacity, singular-value decomposition, and correlation coefficient were used to explain the effects of various polarization schemes on MIMO fading channels. We also propose an analysis method for polarization channel capacity; this method includes the normalization of the received power and polarization effect for different polarization schemes. The validation of the model is based upon data collected in both light-of-sight (LOS) and non-light-of-sight (NLOS) environments. From the numerical simulation results, the proposed analysis method was close to measurements made in an indoor environment.

Effects of Wall Reflection on Indoor MIMO Channel Capacity

SUMMARY The effects of wall reflection on indoor MIMO channel capacity are statistically investigated with consideration of the average received power, the effective degrees of freedom (EDOF) of multipaths and the eigenvalues of transfer channel covariance matrix. It is found that the stronger wall reflection can lead to higher MIMO channel capacity.

Frequency Correlation Characteristics Due to Antenna Configurations in Broadband MIMO Transmission

Recently, Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) has attracted much attention as a technology achieving high-speed wireless transmission with a limited bandwidth. However, since bit loading and adaptive modulation per sub-carrier should be employed according to the transmission quality of each sub-carrier in MIMO-OFDM, it is very important to understand the frequency correlation characteristics in broadband MIMO channels. This paper investigates the frequency correlation characteristics based on the antenna configuration for actual indoor MIMO channels. The results show that the frequency correlation of the channel capacity for the array antenna configured in the horizontal plane is significantly different compared to that configured in the vertical plane. Moreover, we propose a new cluster model that considers the antenna configuration in both the horizontal and vertical planes to estimate the frequency correlation in broadband MIMO channels.

MIMO channel capacity and modeling issues on a measured indoor radio channel at 5.8 GHz

Multiple transmitters and receivers can be used to provide high link capacity in future wireless systems. Herein, an analysis of indoor environment multiple-input-multiple-output (MIMO) measurements in the industrial, scientific, and medical (ISM) band at 5.8 GHz is performed and the possible increase in capacity, utilizing multiple transmitters and receivers is examined. The investigation shows that in the measured indoor environment, the scattering is sufficiently rich to provide substantial link capacity increases. Furthermore, the effect of intra-element spacing on the channel capacity is studied. Our investigation also shows that the envelope of the channel coefficients for this obstructed-line-of-sight (OLOS) indoor scenario is approximately Rayleigh distributed and the MIMO channel covariance matrix can be well approximated by a Kronecker product of the covariance matrices describing the correlation at the transmitter side and the receiver side, respectively. A statistical narrowband model for the OLOS indoor MIMO channel based on this covariance structure is presented.

Modeling of Wide-Band MIMO Radio Channels Based on NLoS Indoor Measurements

In this paper, we first verify a previously proposed Kronecker-structure-based narrow-band model for nonline-of-sight (NLoS) indoor multiple-input-multiple-output (MIMO) radio channels based on 5.2-GHz indoor MIMO channel measurements. It is observed that, for the narrow-band case, the measured channel coefficients are complex Gaussian distributed and, consequently, we focus on a statistical description using the first- and second-order moments of MIMO radio channels. It is shown that the MIMO channel covariance matrix can be well approximated by the Kronecker product of the covariance matrices, seen from the transmitter and receiver, respectively. A narrow-band model for NLoS indoor MIMO channels is thus verified by these results. As for the wide-band case, it is observed that the average power-delay profile of each element of the channel impulse response matrix fits the exponential decay curve and that the Kronecker structure of the second-order moments can be extended to each channel tap. A wide-band MIMO channel model is then proposed, combining a simple COST 259 single-input-single-output channel model and the Kronecker structure. Monte Carlo simulations are used to generate indoor MIMO channel realizations according to the models discussed. The results are compared with the measured data using the channel capacity and good agreement is found.