Antti Roivainen

On the coverage of LPWANs: range evaluation and channel attenuation model for LoRa technology

In addition to long battery life and low cost, coverage is one of the most critical performance metrics for the low power wide area networks (LPWAN). In this work we study the coverage of the recently developed LoRa LPWAN technology via real-life measurements. The experiments were conducted in the city of Oulu, Finland, using the commercially available equipment. The measurements were executed for cases when a node located on ground (attached on the roof rack of a car) or on water (attached to the radio mast of a boat) reporting their data to a base station. For a node operating in the 868 MHz ISM band using 14 dBm transmit power and the maximum spreading factor, we have observed the maximum communication range of over 15 km on ground and close to 30 km on water. Besides the actual measurements, in the paper we also present a channel attenuation model derived from the measurement data. The model can be used to estimate the path loss in 868 MHz ISM band in an area similar to Oulu, Finland.

Application of cognitive radio techniques to satellite communication

Applicability of cognitive radio (CR) techniques to satellite communications is investigated and classification for the possible applications is foreseen in this paper. The proposed application scenarios include a) secondary use of satellite spectrum by a terrestrial system, b) secondary use of terrestrial spectrum by a satellite system, and c) a hybrid scenario where terrestrial network coverage is expanded by the use of satellite spots. Key challenges and enabling technologies for each scenario are discussed. Link budget analyses and system simulations are used to define operational limits for interference management in the mentioned scenarios regarding spectrum sensing, transmission power control, and directional antennas. The results show that CR techniques should be applied with caution in satellite bands. However, obvious potential to improve the spectrum efficiency can be seen in each scenario.

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.

Frequency-Agile Pathloss Models for Urban Street Canyons

Frequency-agile pathloss models for urban street canyons are discussed in this paper. The models are floating intercept (FI), fixed reference (FR), and ITU-R M.2135 urban microcellular (UMi) line-of-sight (LOS) and Manhattan-grid non-LOS (NLOS) models. These models are parameterized based on channel sounding campaigns in three cities covering radio frequencies ranging from 0.8 to 60 GHz. Fitting the models with measured pathloss reveals that the models are usable to cover the considered frequency range. The FI and FR models are equally simple and robust, with a slight advantage of the FI model in accuracy because of the larger number of model parameters. The original M.2135 LOS model is based on a two-ray model that includes a break point (BP). The model is extended for a better fit with measurements by including new model parameters such as a pathloss offset and a BP scaling factor that represent local scattering conditions of surrounding environments. The new model parameters are found frequency dependent in many cases. The original M.2135 model is furthermore simplified in NLOS scenarios while maintaining the model accuracy. The model parameters are derived using maximum likelihood estimation, which also showed that the modified M.2135 model offers up to 50% better accuracy compared to the FI and FR models in terms of the employed log-likelihood function (LLF). The improvement in accuracy is particularly remarkable in NLOS scenarios. A full set of parameters is provided for the models, allowing a choice for any given requirements on accuracy and complexity. Finally, applicability of the proposed models to other street canyons is discussed using independent pathloss measurements.

Radio propagation modeling for 5G mobile and wireless communications

This article first identifies requirements of 5G radio propagation models for relevant propagation scenarios and link types derived from the analysis of recently discussed 5G visions and respective 5G technology trends. A literature survey reveals that none of the state-of-the-art propagation models such as WINNER/IMT-Advanced, COST 2100, and IEEE 802.11 fully satisfies the model requirements without significant extensions, and therefore there is room for a new framework of propagation models. We then present a novel map-based propagation model that satisfies the model requirements, and also introduce new extensions to existing stochastic models. Several open issues are finally identified that require further studies in 5G propagation modeling.

Vehicle-to-vehicle radio channel characterization in urban environment at 2.3 GHz and 5.25 GHz

In this paper, we present the channel measurement results of vehicle-to-vehicle (V2V) measurement campaign carried out in Oulu city center, Finland. The measurements were conducted with EB Propsound CSTM at 2.3 GHz and 5.25 GHz center frequencies. The antennas were installed on the roof of the vehicles and the measurements were performed for single-input multiple-output (SIMO) antenna configuration. The campaign results are presented in the form of path loss, delay spread (DS), maximum excess delay, the standard deviation of slow fading (SF) and K-factor. Furthermore, we propose the method for calculating correlation distance for large scale parameters in V2V channel and present the results for correlation distances of SF, DS and K-factor. The correlation distances less than 11 meters were observed.

Interference Study of Micro Licensing for 5G Micro Operator Small Cell Deployments

5G brings along very dense small cell deployments in specific locations such as hospitals, campuses, shopping malls, and factories. This will result in a novel 5G deployment scenario where different stakeholders, i.e., micro operators, are issued local spectrum access rights in the form of micro licenses, to deploy networks in the specific premises. This new form of sharing-based micro licensing guarantees that the local 5G networks remain free from harmful interference from each other and also protects potential incumbent spectrum users’ rights. It admits a larger number of stakeholders to gain access to the 5G spectrum to serve different vertical sectors’ needs beyond traditional mobile network operators (MNO) improving the competition landscape. We characterize the resulting interference scenarios between the different micro operators’ deployments and focus on the building-to-building scenario where two micro operators hold micro licenses in separate buildings in co-channel and adjacent channel cases. We analyze the resulting allowable transmit power levels of a base station from inside one building towards an end user mobile terminal inside another building as a function of the minimum separation distance between the two micro operator networks. Numerical results are provided for the example case of the 3.5 GHz band with different building entry losses characterizing the impact of propagation characteristics on the resulting interference levels. The results indicate that the building entry losses strongly influence the interference levels and resulting required minimum separation distances, which calls for flexibility in determining the micro license conditions for the building specific situation.

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.

Satellite Uplink Transmission with Terrestrial Network Interference

The impact of the terrestrial network interference to a satellite uplink transmission is studied in this paper. In a system, where an LTE terrestrial network is extended by a satellite communication, the terrestrial interference can become a problem. The interference levels are studied via infield measurements and link budget calculations and the interference tolerance of the satellite receiver are studied via computer simulations. The results show that in spite of the long satellite communication link, strictly power limited system and terrestrial interference the satellite link can operate on the same frequency band as the terrestrial network.

Performance of terrestrial network with the presence of overlay satellite network

In a hybrid (integrated) satellite-terrestrial system users are provided services seamlessly via a satellite or a terrestrial network. One approach is to design the hybrid network using frequency reuse in a way that satellite spot beams do not overlap the terrestrial network coverage area for the same frequency bandwidth. However, the satellite beams are drifting over time which inevitably causes interference to the terrestrial network. In this paper, another hybrid network approach is studied in which the coverage of the satellite beam fully overlays the terrestrial network coverage. Specially, the performance of the 3GPP long term evolution (LTE) network is studied in a suburban macrocell environment with the presence of interference from overlapping satellite network. Simulation results are provided for base station (BS) intersite distance (ISD) of 3 km and 6 km assuming BS transmission power of 40 W. The bandwidth of 10 MHz was applied for the terrestrial transmission and the bandwidths of 3, 5 and 10 MHz were assumed for the satellite transmission in order to study the partially and fully overlapping cases. The terrestrial network tolerance depends strongly on the network planning issues such as the BS transmission power and the ISD of base stations. For the applied terrestrial network parameters, the system performance degradation due to satellite interference is small.