Nuutti Tervo

Geometry-Based Stochastic Channel Model for Two-Story Lobby Environment at 10 GHz

This paper presents a complete parametrization for a three-dimensional (3-D) geometry-based stochastic radio channel model (GSCM) at 10.1 GHz based on a measurement campaign. The radio channel measurements were carried out with a vector network analyzer over a 500 MHz bandwidth in a two-story lobby environment. The measurements were conducted with 9 × 324 dual polarized virtual antenna arrays in line-of-sight (LOS) and non-LOS propagation conditions. The recorded data was post-processed using the estimation of signal parameters via rotation invariance algorithm. The statistical analysis was carried out to provide full 3-D parametrization for the GSCM. The parametrization was verified by radio channel simulations. Multiple-input multiple-output (MIMO) channel is reconstructed from the estimated propagation paths and equivalently the channel simulations are performed by quasi-deterministic radio channel generator using our measurements-based parameters. The channel capacity, Demmel condition number, and relative condition numbers are used as the verification metrics. The results show that the reconstructed MIMO channel matches well the simulated MIMO channel.

Parametrization and Validation of Geometry-Based Stochastic Channel Model for Urban Small Cells at 10 GHz

We derive a full measurement-based parametrization for a 3-D geometry-based stochastic channel model for an urban microcell type of environment at 10 GHz. The measurements were performed with a vector network analyzer and dual polarized virtual arrays at the bandwidth of 500 MHz. The proposed parametrization is validated by channel simulations. Multiple-input multiple-output channel is reconstructed from the measured data and compared with channel generated by the quasi deterministic radio channel generator using the proposed statistical parameters. The capacity and eigenvalue distribution are used as the validation metrics, showing almost perfect match between the reconstructed and simulated channels.

Analyzing 5G RF System Performance and Relation to Link Budget for Directive MIMO

Wideband fifth generation systems utilizing high carrier frequency and multiple-input multiple-output (MIMO) raise major challenges for the system design. Wave propagation and practical hardware tradeoffs at higher frequency ranges provide new boundary conditions for the implementation. This paper addresses system performance boundaries and the analysis method toward multibeam communications at millimeter wave. We combine analysis from antennas and propagation to the radio frequency (RF) transceiver specifications and beamforming requirements. Realistic propagation model and antenna implementation are used to generate beam-specific path gains and provide a wide variety of user scenarios. Using this approach, system level interdependencies and RF performance boundaries can be verified with different antenna configurations in various propagation environments. As an example, we present MIMO link budget analysis targeting 10 Gbits/s for multiple devices in the office scenario at 27 GHz.

RF Driven 5G System Design for Centimeter Waves

5G system design is a complex process due to a great variety of applications and their diverse requirements. This article describes our experiences in developing a centimeter waves mobile broadband concept satisfying future capacity requirements. The first step in the process was the radio channel measurement campaign and statistical modeling. Then the link level design was performed tightly together with the radio frequency (RF) implementation requirements to allow as large scalability of the air interface as possible. We started the concept development at 10 GHz frequency band and during the project World Radiocommunication Conference 2015 selected somewhat higher frequencies as new candidates for 5G. Thus, the main learning was to gain insight of interdependencies of different phenomena and find feasible combinations of techniques and parameter combinations that might actually work in practice, not only in theory.

Digital predistortion of amplitude varying phased array utilising over-the-air combining

In this paper, we propose a simple polynomial linearisation technique for nonlinear phased arrays including amplitude control. Due to the large number of antennas and thus power amplifiers in the array, it is inefficient to linearise each power amplifier individually. Therefore, it is demonstrated that the array can be linearised over-the-air using single polynomial. The simulations show that the linearisation is achieved by first linearising the higher driven PAs at the precompression region and then cancelling the compression by the heavily expanding lower driven PAs. The proposed approach offers an alternative way of re-thinking the concept of array linearisation over multiple PAs.

Hybrid beamforming for single-user MIMO with partially connected RF architecture

Hybrid analog-digital beamforming has been recognized as a promising solution for a practical implementation of massive multiple-input multiple-output (MIMO) systems based on millimeter-wave technology. In this paper, three hybrid beamforming algorithms are proposed for single-user MIMO systems with partially connected radio frequency (RF) architecture, including a singular value decomposition (SVD) matching algorithm, an iterative orthogonalization algorithm, and a transmit-receive zero forcing (ZF) algorithm. The rate performance of the proposed algorithms is compared with fully digital and analog beamforming in a realistic geometry-based stochastic channel model. The simulation results show that the transmit-receive ZF is superior among hybrid methods, and it provides performance relatively close to that of the digital beamforming. In conclusion, carefully designed partially connected hybrid beamforming can obtain an excellent balance between hardware complexity and performance.