Peter Ökvist

15 GHz propagation properties assessed with 5G radio access prototype

This paper presents coverage and penetration loss measurements in an urban environment at 15 GHz to provide insight into the design and deployment of future 5G systems in higher frequency bands. The measurements are performed using a 5G radio access prototype including two transmission points (TPs) and a mobile terminal over a 200 MHz bandwidth. The TPs and the mobile terminal each consists of multiple antennas, enabling spatial multiplexing of multiple data streams. Coverage measurements are performed for both outdoor and outdoor-to-indoor scenarios. Penetration losses are measured for human body, normal and coated windows, a metallic white board, and a concrete pillar. Outdoor microcellular coverage in line-of-sight (LOS) and lightly shadowed areas is shown to be possible with similar antenna directivities as in the existing cellular networks. Transitions into non-line-of-sight (NLOS) bring additional losses in the order of 20 dB, thereby making the NLOS coverage challenging. Outdoor-to-indoor coverage seems to be limited to areas that are in almost LOS with the outdoor TP. Moreover, the penetration loss of indoor blocking objects seems to further restrict the indoor coverage. Potentials of beamforming as a means to improve the coverage are also evaluated via simulations.

LTE HetNet Trial - Range Expansion Including Micro/Pico Indoor Coverage Survey

Adding low power nodes is one option to meet the increased mobile broadband traffic demands. In the resulting heterogeneous network (HetNet) with different node power levels, range expansion is a key feature to improve uplink as well as to increase the coverage of micro/pico nodes. In this paper measurement results from a trial with Release 8 terminals and system verify that range expansion can improve uplink bit rate at a limited cost in downlink bit rate. Also, the macro versus micro/pico indoor coverage is assessed by scanning three office buildings. Coverage using a 2x1 W pico node is assessed to 75 percent of the coverage with a 2x5 W micro node. Range expansion can increase the indoor coverage with 1.5 to 4 percentages per dB.

LTE frequency selective scheduling performance and improvements assessed by measurements

In this paper the potential of downlink frequency selective scheduling (FSS) is addressed based on measurements in an experimental 3GPP Long Term Evolution (LTE) system setup. We find that scheduling on the best sub-band has the potential to improve channel conditions by up to 2 Channel Quality Indicator (CQI) units, which represents around 4 dB channel gain improvement. The time-frequency fading characteristics as a function of mobile speed is described and verified in measurements where instances of correlated time-frequency fading are observed. In stationary or semi-stationary scenarios CQI reporting delays are not limiting. However, at a mobile speed of 10 km/h the gain is lost when the reporting delay reaches 20 ms at the studied 2 GHz band. A simple prediction algorithm that utilizes how the best sub-band moves in frequency domain can improve the gain at 10 km/h around one CQI unit (2 dB) for the studied measurements indicating improvement potential for FSS at higher mobile speed.

Indoor and Outdoor Experiments on 5G Radio Access Using Distributed MIMO and Beamforming in 15 GHz Frequency Band

This paper presents indoor and outdoor field experimental results that clarify the 4-by-8 MIMO throughput performance when applying distributed multiple-input multiple-output (MIMO) with a narrow antenna beam tracking in the 15 GHz frequency band in the downlink of a 5G cellular radio access system. The experimental results show that throughput exceeding 15 Gbps is achieved with a high average rank of 4 at an indoor office building lobby and outdoor parking area. As for the distributed MIMO gain in terms of throughput in LoS environments, we achieve throughput gain of 39 % and 105 % in the indoor office building lobby and outdoor parking area, respectively. And also throughput gain of 15 % is achieved in N-LoS environment in office building lobby in multi-path rich environment. We also observe a significant increase of throughput and rank when changing the transmission point (TP) spacing from 0.5 to 1.5 m, while only a limited performance improvement when the TP spacing exceeds 1.5 m. Finally, the throughput performance with various TP positions was tested, and the TP locations when facing each other with a TP spacing of 50 m exhibit excellent performance exceeding 10 Gpbs.

15 GHz Street-Level Blocking Characteristics Assessed with 5G Radio Access Prototype

Knowledge about propagation properties and development of realistic channel models at higher frequencies are crucial for evaluations and design decisions in the upcoming 5G standardizations. One propagation phenomenon that requires special attention at higher frequencies is blocking by objects. In this paper, the propagation characteristics in the presence of street-level blocking objects at 15 GHz are investigated based on measurement with a 5G radio access prototype. It is found that blocking by moving obstacles has similar behavior as that by stationary ones. The results are also used to verify the validity of the blocking model developed in the METIS project at higher frequencies. Blocking loss in the range 3-12 dB is observed, which is not larger than that at lower frequency bands. Moreover, our Doppler analysis reveals that for some objects such as cars and vans propagation happens only around the objects; but for other objects such as trees, propagation happens through the object. Reflection and scattering are also identified to contribute to the limited loss from blocking and increase the channel richness enabling improved spatial multiplexing.

Indoor experiment on 5G radio access using beam tracking at 15 GHz band

This paper presents indoor experimental results showing the achievement of 14.5 Gbps throughput performance based on 730.5 MHz bandwidth transmission when applying carrier aggregation (CA) with 8 component carriers (CCs) and 4-by-8 single-user multiple-input multiple-output (MIMO) multiplexing in the 15 GHz frequency band in the downlink of 5G cellular radio access. Beam tracking with massive MIMO is implemented in a 5G testbed to support user mobility with a narrow beam. Experimental results in an indoor multi-path rich environment show that the peak throughput is 14.5 Gbps in a line-of-sight (LoS) environment with high mobility-reference signal received power (MRSRP) and low antenna correlation. The results also show that 12.5 Gbps is achieved behind a wall in non-LOS conditions due to ceiling reflections.

Outer-loop power control based on hybrid ARQ protocol for WCDMA enhanced uplink

In this article, a node B-located outer-loop power control (OLPC) algorithm for WCDMA enhanced uplink (E-UL) based on the number of hybrid automatic repeat request (HARQ) transmission attempts is introduced. The proposed OLPC algorithm can take full advantage of the HARQ protocol since its operation is not affected by the signaling delay between node B and radio network controller (RNC). However, when the Node B-located OLPC is considered in a soft handover (SHO) situation, the Carrier-to-interference Ratio (CIR)-drift problem that emerges compromises the OLPC performance, and some mechanism to compensate for the CIR-drift problem is required. Both an aggressively tuned anti-windup function and an retransmission sequence number (RSN)-based functionality handle this problem. The proposed Node B-located OLPC is evaluated for 2 ms and 10 ms transmission time intervals (TTIs). It is observed that the Node B-located OLPC provides gains in terms of lower CIR and is more beneficial for 2 ms TTI, since the RNC signaling delay has rather severe impact in a shorter round trip time (RTT).

Distributed MIMO demonstrated with 5G radio access prototype

This paper presents measurement results from a distributed 4×4 multiple-input multiple-output (MIMO) trial. The measurements were performed using a 5G radio access prototype including two transmission points (TPs) and a mobile terminal over 200 MHz bandwidth at 15 GHz carrier frequency. The TPs and the mobile terminal each consists of multiple antennas, enabling spatial multiplexing. In the present paper, improvements from using 4×4 MIMO transmission with dual TPs are being assessed and compared with 4×4 MIMO transmission from one single TP. A significant increase in throughput was demonstrated with distributed MIMO where the two TPs were transmitting unique streams in parallel. This significantly improved the spatial multiplexing capacity in line-of-sight and increased the rank significantly beyond the two polarization dimensions. In the performed tests this improved the throughput from 1.1 Gbps (5.7 bps/Hz) to 2.5 Gbps (12.6 bps/Hz).

Experimental evaluation on 5G radio access employing multi-user MIMO at 15 GHz band

This paper presents indoor and outdoor experimental results on the achievable throughput for downlink 8-by-16 multi user (MU)-multiple-input multiple-output (MIMO) using 2 sets of user equipment (UE) and carrier aggregation with 8 component carriers in various measurement areas for 5G radio access. In the presence of four centralized antenna units, the throughput performance is evaluated using the implemented 5G testbed for MU-MIMO operation. The experimental results show that the peak system throughput of 18.6 Gbps and 25.9 Gbps are achieved in indoor and outdoor environments. Furthermore, we confirm that to avoid interference a vertical angle exceeding 18 deg. or a horizontal angle exceeding 10.7 deg. is required between UEs to achieve the throughput of 12 Gbps for a UE when employing MU-MIMO in an outdoor open space.

Measurement-Based Stochastic mmWave Channel Modeling

Emerging mmWave technology will require new channel models. Compared to the lower frequency bands, mmWaves will be more reflected and absorbed but less diffracted. Hence, placement of individual physical structures in the environment will affect the propagation much more than before, providing a challenge for channel modeling. At the same time, however, an increasing amount of information about the topology of the physical environment, in particular for buildings, is made available through better measurement equipment and services for obtaining 3D data. We propose a Monte-Carlo approach for channel modeling where interactions between mmWaves and the surrounding small-scale environment can be included, given a stochastic representation. This method is not only suitable for assessment of basic effects such as material reflection and absorption, but can also in the future be extended to various additional effects such as weather, traffic, foliage, etc. The framework is verified against 15 GHz measurements from an urban environment, demonstrating how major reflection paths can be replicated by modeling the closest buildings.