Jyri Putkonen

A Statistical Spatio-Temporal Radio Channel Model for Large Indoor Environments at 60 and 70 GHz

Millimeter-wave radios operating at unlicensed 60 GHz and licensed 70 GHz bands are attractive solutions to realize short-range backhaul links for flexible wireless network deployment. We present a measurement-based spatio-temporal statistical channel model for short-range millimeter-wave links in large office rooms, shopping mall, and station scenarios. Channel sounding in these scenarios at 60 and 70 GHz revealed that spatio-temporal channel characteristics of the two frequencies are similar, making it possible to use an identical channel model framework to cover the radio frequencies and scenarios. The sounding also revealed dominance of a line-of-sight and specular propagation paths over diffuse scattering because of weak reverberation of propagating energy in the scenarios. The main difference between 60 and 70 GHz channels lies in power levels of the specular propagation paths and diffuse scattering which affect their visibility over the noise level in the measurements, and the speed of power decay as the propagation delay increases. Having defined the channel model framework, a set of model parameters has been derived for each scenario at the two radio frequencies. After specifying the implementation recipe of the proposed channel model, channel model outputs are compared with the measurements to show validity of the channel model framework and implementation. Validity was demonstrated through objective parameters, i.e., pathloss and root-mean-square delay spread, which were not used as defining parameters of the channel model.

Enabling wireless backhauling for next generation mmWave networks

This paper presents some key findings w.r.t. the Radio Resource Management (RRM) in wireless Backhaul (BH) of mmWave networks. First, the envisioned design of mmWave backhaul architecture is outlined highlighting the most important newly needed functional blocks and in what they differ from a non-mmWave architectures. Next, the challenges and functionality of RRM techniques are discussed, focusing on Routing and Link scheduling algorithms in such BH architecture. Furthermore different possible interactions between RRM functions are explored. Finally, preliminary analytical and experimental study on the performance of different link scheduling and routing functions for mmWave backhauling are provided, highlighting in particular the impact of traffic load and dynamic route selection on BH End to End delay.

On the Mutual Orthogonality of Millimeter-Wave Massive MIMO Channels

Mutual orthogonal user channels in multiuser (MU)-multiple-input multiple-output (MIMO) systems are desirable and can be approximately obtained under independent and identically distributed (i.i.d.) Rayleigh fading assumption with a very large number of base station antennas. However, it has been shown that at millimeter-wave (mmW) frequencies, this assumption is not valid due to the limited number of multipath components and spatial channel correlation. In this paper, we examine the mutual orthogonality of a realistic 60-GHz outdoor propagation channel with practical large antenna arrays, and determine the factors deciding it based on the channel data generated by means of deterministic field prediction. The results obtained reveal relationships between mutual orthogonality, inter-user distance, number of active users, transmit array dimensions, and downlink system capacity at 60-GHz band, which are useful for designing future mmW massive MU-MIMO systems.

Impact of mounting structures twists and sways on point-to-point millimeter-wave backhaul links

This paper investigates an impact of twists and sways of mounting structures on the performance of point-topoint millimeter-wave backhaul links. Characteristics of twists and sways are studied by experimental measurements performed on different telecom infrastructure sites and municipal sites considered for small cells installations. The measurements are done in four cities in Russia and Finland in the period from June to November 2014. Statistical distributions of the twists and sways amplitudes are derived from the experimental data and applied for analysis of the impact that such deflections may have on performance of the millimeter-wave links. An enhanced approach for channel availability estimation is proposed where two statistical parameters are involved as random channel attenuation values: rain absorption and losses caused by antenna deflections due to twists and sways. To illustrate the practical usefulness of the approach, link gain degradations and channel availabilities are calculated for several practical scenarios. For example, it is found that for 20 beamwidth antennas and realistic sways of typical thin lamp poles available in most cities, the received power level may decrease from 2 dB and up to 20 dB. That gives essentially different results for the link distance prediction relative to the case when the twists and sways effects are not taken into account.

70 GHz Radio Wave Propagation Prediction in a Large Office

Site-specific millimeter-wave propagation prediction requires data of the environment under study, which is usually not available for indoor scenarios. With means of laser scanning the details of the indoor environment can be captured accurately in the form of a point cloud. The total field is estimated as a sum of paths backscattering from the point cloud, where the electromagnetic scattering for each path is calculated with a single-lobe directive model. In this paper we focus on predicting the radio wave propagation in a large office environment at 70 GHz, where the accuracy is evaluated by comparing measured and predicted mean delays and delay and azimuth spreads. We also present a method for dealing with shadowing in the indoor environment. The results show good agreement between measured and predicted delay and azimuth spreads for line-of-sight links, and also non-line-of-sight links can be predicted with reasonable accuracy.

Challenges and opportunities for millimeter-wave mobile access standardisation

This paper presents the main advantages and challenges that the introduction of millimeter-wave mobile access brings to the forthcoming 5G system architecture, focusing on the expected impact of that technology on standards and regulation bodies. The EU-funded project MiWaveS is taken as a concrete example for the standardization impact.

MmWave use cases and prototyping: A way towards 5G standardization

In the framework of the forthcoming 5G telecommunication system, the definition of realistic use cases and prototypes strongly connected to them is key in order to demonstrate how well emerging enabling technologies can fulfil the challenges introduced by the 5G Heterogeneous Network (HetNet) architecture. This paper shows how millimeter wave (mmWave) technologies can be properly assessed by selecting real-life use cases and then deriving out of experimental platforms significant system Key Performance Indicator (KPI). Finally, the status of mmWave activities in standards bodies is described, highlighting which bodies are to be addressed for a successful go-to-market of such emerging technology.

Dual-Band Multipath Cluster Analysis of Small-Cell Backhaul Channels in an Urban Street Environment

Thanks to the large spectrum chunks available above 6-GHz bands, several centimeter-wave (cm-wave) and millimeter- wave (mm-wave) bands are being exploited for mobile communications to meet 5G high data speed and low latency requirements. The 5G standardization has been started with the channel modelling for the bands from 6 and up to 100 GHz, and the current models adapting the 3GPP stochastic cluster-based approach. This paper presents a recent measurement campaign and multipath cluster characterization of 15 and 28 GHz channels in an urban street canyon. The measurement environment and setup are targeted for small-cell backhaul scenarios, whose model parameters are currently lacking in current standardized channel models. Inter-cluster and intra-cluster characteristics are presented and compared between two measured frequency ranges. The results show that the number of MPCs per cluster is noticeable higher in 28 GHz, and that is mainly attributed by the higher measurement bandwidth in this band. The higher number of MPCs in 28 GHz leads to little wider cluster delay and angle spreads, while other model parameters are similar or just little varied with carrier frequency. The paper also provides other relevant cluster statistics required to establish 3GPP channel model for the scenario of interest in the 15 and 28 GHz bands.

5G E-band backhaul system evaluations: Focus on moving objects and outdoor to indoor transmission

It is expected that small cells will carry more than half of the total traffic in 5G, resulting in a huge increase of wireless backhaul traffic. To successfully design and deploy the mmW backhaul system, it is essential to evaluate the performance in different scenarios, also links installed in low human height-level elevations. We report a recent 5G E-band backhaul system measurement campaign focusing on the effects of vehicles passing across and pedestrian walking along the line-of-sight, and outdoor to indoor penetration loss. With the car roofs and humans moving in the same height or a bit lower than the radio LOS, their impact on the radio signal is clearly seen but is not detrimental. By introducing small changes in height, the impact can be reduced from 12 dB to 3.4 dB. The range of penetration losses of modern glass is from 5 dB to 39 dB.

Radio resource management for heterogeneous millimeter-wave backhaul and access network

This paper explores network design requirements and radio resource management (RRM) functionalities required to enable a heterogeneous millimeter-wave (mmW) network in both backhaul and access links. First, the envisioned design of a heterogeneous mmW network is outlined highlighting the main functional blocks and the key differentiating factors from non-mmW architectures. Next, the RRM functionalities required in both backhaul and access networks are discussed in detail, focusing on routing, link scheduling, dynamic TDD in the backhaul and dynamic “beam cell” management on the access links. Finally, some recent findings are presented, highlighting the impact of identified functionalities on network-wide performance indicators including latency and packet loss ratio.