Will the Upper 6 GHz Bands Work for 5G NR?

In the never-ending pursuit of bandwidth, mid-bands have been recently reconsidered as the primary spectrum for 5G NR and its evolution. Laying between the crowded lower frequency bands and the propagation-unfriendly higher bands (i.e., millimeter wave), the upper 6 GHz band (6425-7125 MHz) presents a valuable compromise between capacity and coverage. Recognizing its potential, the research community has expressed interest in this spectrum and conducted several studies. Despite this enthusiasm, the deployment of upper 6 GHz testbeds remains elusive. This paper aims to address this gap by presenting the results of a comprehensive measurement campaign conducted on a 5G NR cellular system operating in the upper 6 GHz band (6425-7125 MHz), specifically deployed within the Politecnico di Milano campus. Our objective was to evaluate the system's performance in a realistic environment and provide insights supported by empirical measurements. The measurement campaign yielded positive results, showcasing a remarkable channel capacity in urban areas, which remained consistently high even at the cell edge and in challenging non-line-of-sight and outdoor-to-indoor scenarios

Multi-Camera View Based Proactive BS Selection and Beam Switching for V2X

Due to the short wavelength and large attenuation of millimeter-wave (mmWave), mmWave BSs are densely distributed and require beamforming with high directivity. When the user moves out of the coverage of the current BS or is severely blocked, the mmWave BS must be switched to ensure the communication quality. In this paper, we proposed a multi-camera view based proactive BS selection and beam switching that can predict the optimal BS of the user in the future frame and switch the corresponding beam pair. Specifically, we extract the features of multi-camera view images and a small part of channel state information (CSI) in historical frames, and dynamically adjust the weight of each modality feature. Then we design a multi-task learning module to guide the network to better understand the main task, thereby enhancing the accuracy and the robustness of BS selection and beam switching. Using the outputs of all tasks, a prior knowledge based fine tuning network is designed to further increase the BS switching accuracy. After the optimal BS is obtained, a beam pair switching network is proposed to directly predict the optimal beam pair of the corresponding BS. Simulation results in an outdoor intersection environment show the superior performance of our proposed solution under several metrics such as predicting accuracy, achievable rate, harmonic mean of precision and recall

Can we exploit machine learning to predict congestion over mmWave 5G channels?

It is well known that transport protocol performance is severely hindered by wireless channel impairments. We study the applicability of Machine Learning (ML) techniques to predict congestion status of 5G access networks, in particular mmWave links. We use realistic traces, using the 3GPP channel models, without being affected using legacy congestion-control solutions. We start by identifying the metrics that might be exploited from the transport layer to learn the congestion state: delay and inter-arrival time. We formally study their correlation with the perceived congestion, which we ascertain based on buffer length variation. Then, we conduct an extensive analysis of various unsupervised and supervised solutions, which are used as a benchmark. The results yield that unsupervised ML solutions can detect a large percentage of congestion situations and they could thus bring interesting possibilities when designing congestion-control solutions for next-generation transport protocols.This work was supported by the Spanish Government (MINECO) by means of the project FIERCE “Future Internet Enabled Resilient smart CitiEs” under Grant Agreement No. RTI2018-093475-A-I00

A simulation study of beam management for 5G millimeter-wave cellular networks

openThis thesis aims at performing a system-level analysis of beam management protocol under different scenarios, mobility conditions and parameters configurations.This thesis aims at performing a system-level analysis of beam management protocol under different scenarios, mobility conditions and parameters configurations

Beamforming based full-duplex for millimeter-wave communication

In this paper, we study beamforming based full-duplex (FD) systems in millimeter-wave (mmWave) communications. A joint transmission and reception (Tx/Rx) beamforming problem is formulated to maximize the achievable rate by mitigating self-interference (SI). Since the optimal solution is difficult to find due to the non-convexity of the objective function, suboptimal schemes are proposed in this paper. A low-complexity algorithm, which iteratively maximizes signal power while suppressing SI, is proposed and its convergence is proven. Moreover, two closed-form solutions, which do not require iterations, are also derived under minimum-mean-square-error (MMSE), zero-forcing (ZF), and maximum-ratio transmission (MRT) criteria. Performance evaluations show that the proposed iterative scheme converges fast (within only two iterations on average) and approaches an upper-bound performance, while the two closed-form solutions also achieve appealing performances, although there are noticeable differences from the upper bound depending on channel conditions. Interestingly, these three schemes show different robustness against the geometry of Tx/Rx antenna arrays and channel estimation errors

5G Mobile Phone Network Introduction in Colombia

The deployment of the 5G mobile network is currently booming, offering commercially available services that improve network performance metrics by minimizing network latency in countries such as the USA, China, and Korea. However, many countries around the world are still in the pilot phase promoted and regulated by government agencies. This is the case in Colombia, where the assignment of the first 5G band is planned for the third quarter of 2021. By analyzing the results of the pilot phase and the roadmap of the Colombian Ministry of Information and Communication Technologies (MinTIC), we can determine the main issues, which contribute to the deployment of 5G mobile technology as well as the plans to achieve a 5G stand-alone network from 4G networks. This is applicable to other countries in Latin America and the world. Then, our objective is to synthesize and share the most important concepts of 5G mobile technology such as the MIMO (multiple input/multiple output) antenna, RAN (Radio Access Network), C-RAN (Centralised-RAN), and frequency bands, and evaluate the current stage of its introduction in Colombia

Modelling 3D blockage effects for millimetre-wave communication systems

The millimetre wave (mmWave) band, which has a frequency range of 30-300 GHz, can provide the desired requirements for future communication systems, such as wide bandwidth and high data-rate with very low latency. However, these advantages entail several consequences and challenges: compared with the microwave band, below 6 GHz, the mmWave band not only suffers from increased path loss but also higher sensitivity to blockage effects due to very short wavelengths. Considering the mmWave band, a human blockage, for example, could severely affect the transmitted signal by causing attenuation of 20 dB or more. With motion, the attenuation problem becomes even more serious. The rapid changes of dynamic blockages surrounding a moving transceiver can cause a significant and sudden impact on channel attenuation, which affects the overall quality of service for mmWave systems. The main scope of this thesis is to develop new mathematical models that accurately capture the dynamics of blockers affecting a moving transceiver in order to compute the resulting channel attenuation accurately. The first Markov chain model studied in this work follows a simple approach by assigning a fixed-attenuation value to each blocker and using a geometric model to generate the transition probability matrices. The transition probabilities are calculated both analytically and via a geometric simulation, where the results are found to match well. The proposed model successfully captures the dynamics of the channel caused by blockers surrounding a moving transceiver. The model works well for stationary scenarios, and the proposed technique of switching between several Markov chains makes the model applicable to a non-stationary average number of blockers as well. The adaptive sum of Markov chains (sum of MC) is another proposed model, which can model the dynamics of blockage effects more accurately than the simpler Markov Chain model. It is adaptive to non-stationary scenarios in any given environment, and it efficiently captures the dynamics of blockages arising from a moving transceiver. The sum of Markov chains model can integrate any desired attenuation function, including the third-generation partnership project (3GPP) blockage model and any lab measurement attenuation profile. The sum of MC model could be a very useful tool for communication engineers, allowing them to perform an initial mmWave coverage analysis for a given environment in the presence of time-varying blockage effects. Unlike human blockage, which has been widely studied in the literature, the impact of other small objects on signal strength, such as metal road signs, is not so well understood. This thesis has carried out a measurement campaign for these small blockers, which induce measured loss in the range of 15- 30 dB, depending on the type and size of the blocker. The thesis also compares those results with existing simulation blockage models for these small objects. These blockage models include the 3GPP model, the multiple knife-edge (MKE) model, and the mmMAGIC model, where the latter two models show a better fit to the measured attenuation of relatively small blockers than the 3GPP model. Finally, the thesis evaluates the impact of blockers on the overall performance of mmWave multiple-input multiple-output (MIMO) wireless systems, where a ray-tracing tool is used to establish all possible propagation paths for a moving transceiver in an outdoor scenario. The performance impact of the measured attenuation profiles for road signs are evaluated for an outdoor scenario using the sum of MC model

Comparative study of indoor propagation model below and above 6 GHz for 5G wireless networks

It has been widely speculated that the performance of the next generation based wireless network should meet a transmission speed on the order of 1000 times more than the current cellular communication systems. The frequency bands above 6 GHz have received significant attention lately as a prospective band for next generation 5G systems. The propagation characteristics for 5G networks need to be fully understood for the 5G system design. This paper presents the channel propagation characteristics for a 5G system in line of sight (LOS) and non-LOS (NLOS) scenarios. The diffraction loss (DL) and frequency drop (FD) are investigated based on collected measurement data. Indoor measurement results obtained using a high-resolution channel sounder equipped with directional horn antennas at 3.5 GHz and 28 GHz as a comparative study of the two bands below and above 6 GHz. The parameters for path loss using different path loss models of single and multi-frequencies have been estimated. The excess delay, root mean square (RMS) delay spread and the power delay profile of received paths are analyzed. The results of the path loss models show that the path loss exponent (PLE) in this indoor environment is less than the free space path loss exponent for LOS scenario at both frequencies. Moreover, the PLE is not frequency dependent. The 3GPP path loss models for single and multi-frequency in LOS scenarios have good performance in terms of PLE that is as reliable as the physically-based models. Based on the proposed models, the diffraction loss at 28 GHz is approximately twice the diffraction loss at 3.5 GHz. The findings of the power delay profile and RMS delay spread indicate that these parameters are comparable for frequency bands below and above 6 GH

Antennas and Propagation Aspects for Emerging Wireless Communication Technologies

The increasing demand for high data rate applications and the delivery of zero-latency multimedia content drives technological evolutions towards the design and implementation of next-generation broadband wireless networks. In this context, various novel technologies have been introduced, such as millimeter wave (mmWave) transmission, massive multiple input multiple output (MIMO) systems, and non-orthogonal multiple access (NOMA) schemes in order to support the vision of fifth generation (5G) wireless cellular networks. The introduction of these technologies, however, is inextricably connected with a holistic redesign of the current transceiver structures, as well as the network architecture reconfiguration. To this end, ultra-dense network deployment along with distributed massive MIMO technologies and intermediate relay nodes have been proposed, among others, in order to ensure an improved quality of services to all mobile users. In the same framework, the design and evaluation of novel antenna configurations able to support wideband applications is of utmost importance for 5G context support. Furthermore, in order to design reliable 5G systems, the channel characterization in these frequencies and in the complex propagation environments cannot be ignored because it plays a significant role. In this Special Issue, fourteen papers are published, covering various aspects of novel antenna designs for broadband applications, propagation models at mmWave bands, the deployment of NOMA techniques, radio network planning for 5G networks, and multi-beam antenna technologies for 5G wireless communications