Massive MIMO Extensions to the COST 2100 Channel Model: Modeling and Validation

To enable realistic studies of massive multiple-input multiple-output systems, the COST 2100 channel model is extended based on measurements. First, the concept of a base station-side visibility region (BS-VR) is proposed to model the appearance and disappearance of clusters when using a physically-large array. We find that BS-VR lifetimes are exponentially distributed, and that the number of BS-VRs is Poisson distributed with intensity proportional to the sum of the array length and the mean lifetime. Simulations suggest that under certain conditions longer lifetimes can help decorrelating closely-located users. Second, the concept of a multipath component visibility region (MPC-VR) is proposed to model birth-death processes of individual MPCs at the mobile station side. We find that both MPC lifetimes and MPC-VR radii are lognormally distributed. Simulations suggest that unless MPC-VRs are applied the channel condition number is overestimated. Key statistical properties of the proposed extensions, e.g., autocorrelation functions, maximum likelihood estimators, and Cramer-Rao bounds, are derived and analyzed.Comment: Submitted to IEEE Transactions of Wireless Communication

The Random Line-of-Sight Over-the-Air Measurement System

As our society becomes increasingly connected, a growing number of devices rely on wireless connectivity. The type, use and form factor of these devices range from wearables to entire vehicles. Additionally, the fifth generation of wireless communication (5G) introduces new communication bands, also at higher frequencies. At these millimeter-wave frequencies, large portions of bandwidth are available which are needed in order to increase the data rates.In this scenario, testing and verifying the wireless communication performance has an increasingly important role. In modern devices, testing needs to be performed over-the-air (OTA), as direct conducted measurements to the antenna ports become unfeasible. Moreover, there is still ongoing research to understand how testing should be performed for devices with large form-factors, such as vehicles, as well as for higher frequencies. The proposed methods are mainly based on techniques for mobile phone testing at the current communication bands, i.e., sub-6 GHz. However, scaling and adapting these methods to work for future needs presents challenges. A possible solution to meet the future testing requirements is offered by the following hypothesis: "If a wireless device is tested with good performance in both pure-LOS and RIMP environments, it will also perform well in real-life environments and situations, in a statistical sense". The rich isotropic multipath (RIMP) and the random line-of-sight (random-LOS) are therefore identified as the two representative edge environments for testing. This thesis focuses on the random-LOS environment, and its practical realization to test the wireless performance of different devices. The thesis is divided into three main parts. The first part describes the practical realization of random-LOS OTA measurement setups. Three different setups are presented, a virtual planar array and two reflector antennas. One reflector system is aimed at vehicular testing for frequencies below 6 GHz, while the other targets smaller devices at 28 GHz. The second part of the thesis focuses on numerical and experimental verification of the random-LOS measurement setups. In the verification, numerical simulations and measurements of the test zone variations are compared for the proposed OTA measurement systems.The third and last part focuses on how passive and active measurements can be performed using a random-LOS measurement setup. The measurements demonstrate the application of the designed OTA measurement systems for passive antenna measurements, as well as active 2x2 multiple-input multiple-output (MIMO) measurements on a complete vehicle

Measurement and Optimization of LTE Performance

4G Long Term Evolution (LTE) mobile system is the fourth generation communication system adopted worldwide to provide high-speed data connections and high-quality voice calls. Given the recent deployment by mobile service providers, unlike GSM and UMTS, LTE can be still considered to be in its early stages and therefore many topics still raise great interest among the international scientific research community: network performance assessment, network optimization, selective scheduling, interference management and coexistence with other communication systems in the unlicensed band, methods to evaluate human exposure to electromagnetic radiation are, as a matter of fact, still open issues. In this work techniques adopted to increase LTE radio performances are investigated. One of the most wide-spread solutions proposed by the standard is to implement MIMO techniques and within a few years, to overcome the scarcity of spectrum, LTE network operators will offload data traffic by accessing the unlicensed 5 GHz frequency. Our Research deals with an evaluation of 3GPP standard in a real test best scenario to evaluate network behavior and performance

Investigation of Prediction Accuracy, Sensitivity, and Parameter Stability of Large-Scale Propagation Path Loss Models for 5G Wireless Communications

This paper compares three candidate large-scale propagation path loss models for use over the entire microwave and millimeter-wave (mmWave) radio spectrum: the alpha-beta-gamma (ABG) model, the close-in (CI) free space reference distance model, and the CI model with a frequency-weighted path loss exponent (CIF). Each of these models have been recently studied for use in standards bodies such as 3GPP, and for use in the design of fifth generation (5G) wireless systems in urban macrocell, urban microcell, and indoor office and shopping mall scenarios. Here we compare the accuracy and sensitivity of these models using measured data from 30 propagation measurement datasets from 2 GHz to 73 GHz over distances ranging from 4 m to 1238 m. A series of sensitivity analyses of the three models show that the physically-based two-parameter CI model and three-parameter CIF model offer computational simplicity, have very similar goodness of fit (i.e., the shadow fading standard deviation), exhibit more stable model parameter behavior across frequencies and distances, and yield smaller prediction error in sensitivity testing across distances and frequencies, when compared to the four-parameter ABG model. Results show the CI model with a 1 m close-in reference distance is suitable for outdoor environments, while the CIF model is more appropriate for indoor modeling. The CI and CIF models are easily implemented in existing 3GPP models by making a very subtle modification -- by replacing a floating non-physically based constant with a frequency-dependent constant that represents free space path loss in the first meter of propagation.Comment: Open access available at: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=743465