Magnus Thurfjell

A power control and scheduling concept for EGPRS

In existing cellular systems power control is used to save battery and to increase radio network capacity. In packet radio systems scheduling and channel allocation have similar characteristics: the quality (data rate) can be increased at the cost of higher energy use. In this paper a concept combining the functions in order to minimize energy use is presented. Furthermore, an interference area model is introduced. With this model the concept can be extended to minimize interference. The concept can be applied to the design of battery saving and spectrum efficient algorithms.

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.

Network Densification Impact on System Capacity

With the tremendous growth of smartphone penetration, the demand for increased capacity in cellular networks has escalated. The trend is predicted to continue for years to come. One common way to cope with the ever increasing capacity demand is to add cells and densify the networks. Network densification was used before the introduction of LTE and Heterogeneous Networks, and will be even more emphasized with the introduction of 5G, where higher frequency bands with more challenging propagation characteristics, will be utilized. This study shows that in a confined geographical area with a fixed number of users, the user bit rate always increases with network densification. It is also shown that the capacity increase slows down with an increased number of cells, due to the increasing interference from the additional cells. Also, if the path loss exponent increases with distance, a reduced distance between cells reduces the capacity increase.

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.

Higher Order Modulation and Turbo Coding for GSM/EDGE Continued Evolution

GSM/EDGE is the worlds largest and most widespread cellular technology. EDGE offers an attractive solution for 3rd generation cellular services in existing GSM networks. The introduction of new services into an existing network typically leads to increased capacity demands, since more users of different service types need to coexist in limited spectrum, while the existing speech service is required to function at least as well as before. Higher Order Modulation in combination with Turbo Coding is proposed to substantially enhance spectrum efficiency and average user bit rates in GSM/EDGE through improved interference robustness and increased peak bit rates. Simulation results indicate link level gains of 2.5-5.5 dB. When additionally applying incremental redundancy, similar relative improvements are shown. Bit rates can be increased by more than 30%, at C/I levels above 30dB. System performance gains are indicated by average user bit rate enhancements of up to 30-40%, along with substantial gains in spectrum efficiency, up to 40%. It is also shown that system gains are rather insensitive to frequency reuse and whether frequency hopping is applied or not (in sparse reuse scenarios).

Reuse of macro frequencies in a micro cell system

In this paper, spectrum management is studied for a scenario with macro cells and contiguous micro cells covering the same urban area. The study is performed in a simulation environment based on detailed information of a city environment and using sophisticated propagation models. It is shown that frequencies from the macro cell layer can be reused in the micro layer to obtain a substantial capacity increase. Careful frequency planning is performed taking into account macro cell interference on a per cell basis in the micro layer as well as the interference relations between different micro cells. To be able to perform analysis and planning, input data from downlink interference measurements or advanced propagation calculations are vital.

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.