Bjorn Halvarsson

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-A Field Measurements: 8x8 MIMO and Carrier Aggregation

The introduction of 8×8 MIMO and carrier aggregation in the 3GPP LTE Rel. 10 opens up for increased user throughput. The potential gains using these techniques have been evaluated in a field measurement campaign with a testbed implementation. A downlink throughput exceeding 1 Gbps has been achieved combining 8×8 MIMO in an outdoor macro scenario with carrier aggregation using three component carriers (3×20 MHz). The relation between the achievable throughput and the channel richness arising from the physical environment and antenna spacing was demonstrated. The performance of MIMO setups ranging from 1×2 up to 8×8 was evaluated in indoor-to-indoor, outdoor-to-indoor, and outdoor-to-outdoor deployments. It was observed that each added transmit or receive antenna increased the throughput. These gains were achieved with a compact UE antenna that is reasonable in size for implementation in a consumer device.

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.

Novel Wi-Fi - LTE Real-Time Traffic Steering - First Field Measurement Results

A novel algorithm, real-time two-way traffic steering, has been developed to address the issue in mixed cellular-wireless deployments that current commercial terminals switch from cellular access to wireless access regardless of the expected bitrate in the wireless cell. In contrast to terminal-controlled traffic steering mechanisms, no changes on the terminal side are needed in order to benefit from the proposed algorithm. The algorithm was tested in an end-to-end test network and very promising results were obtained for both a single user and for multiple users. Two scenarios were considered: In the first scenario, real-time two-way traffic steering was demonstrated for one single moving user. Here the capability of selecting the best access was demonstrated. In the latter scenario, multiple users were moving together mimicking users arriving to and leaving from a train station. Here the load balancing capabilities of the algorithm were demonstrated and it was also seen that the pro-posed algorithm distributes the resources in a fair way between the users.

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).

Field Evaluation of the New Flexible LTE Transmission Mode

Transmission Mode 9 (TM9) is a key component in Release 10 of 3GPP Long Term Evolution (LTE). TM9 contains mobile individual Demodulation Reference Symbols (DMRS). DMRS increases the flexibility of radio resource utilization and opens for a plurality of features such as downlink beamforming and power control. This paper contains measurement results from a trial in a heterogeneous network deployment with a TM9 prototype implementation on a commercial system. It shows that TM9 improves downlink throughput significantly by itself in certain scenarios. An improvement of up to 0.4 bps/Hz is observed around cell edge and in the range expansion zone. This improvement comes from enhanced demodulation based on DMRS.

LTE seamless mobility demonstrated with combined cell in a heterogeneous network

The increased demand on capacity in cellular networks calls for increased site density and heterogeneous networks. With unchanged mobility pattern this will increase the handover rate, the signaling load and the impact from handover on experienced user quality. An attractive solution to mitigate the handover impact is Combined Cell which combines area splitting gain with seamless mobility. In this paper seamless mobility is demonstrated by measurements from a trial with a LTE Combined Cell prototype in a full scale heterogeneous network deployment. The downlink spatial reuse capacity is assessed to be close to separate cell deployment already with release 10 of LTE.

Beamforming Gain Measured on a 5G Test-Bed

This paper presents measurement results from different deployments with a 5G test-bed on a 15-GHz frequency band. The beam gain with a grid-of-beam solution applied to an 8x8 element antenna array is compared with a reference wide-beam power equivalent antenna. The beamforming gain in outdoor environment is found to be large, it is in the range of 10-13 dB in line-of-sight (LoS) and 7-12 dB in non-LoS. In a reflective and rich indoor environment, the gain is as expected lower but still substantial, 5-11 dB. The potential of a hybrid analog-digital solution is also assessed as an upper bound with perfect phase coherent combination of several beams. To reach an average beamforming gain of 14 dB it is sufficient with the combination of three beams in outdoor LoS, while eight beams are required in the indoor scenario.

5G trial system coverage evaluation utilizing multi-point transmission in 15 GHz frequency band

The downlink coverage of a 5G trial system operating within the 15 GHz frequency band is evaluated in this paper with the help of drive test measurements. Key 5G features, such as beamforming, beam tracking and multi-point transmission have been utilized during the measurements. The results indicate that multi-point transmission provides a clear improvement to the downlink coverage. Received signal strength is improved due to the macro diversity offered by the utilization of multiple transmission points. Furthermore, distributed MIMO, i.e. the possibility for the user equipment (UE) to simultaneously receive independent data streams from multiple transmission points, results in large improvements in the average rank values. This is the case in particular for the locations in between the transmission points, where the UE has sufficiently good links towards the serving nodes. Finally, as a result of both the improved signal strength and higher rank values, the average downlink throughput is improved by 33–46% (whole area) or 39–42% (busy square). All in all, the trial system is able to maintain a very high downlink throughput, varying from 4 to 13 Gbps, towards a UE moving within the busy square, which demonstrates the benefit of seamless mobility between the different beams and transmission points.