Constellation design for future communication systems: a comprehensive survey

[EN] The choice of modulation schemes is a fundamental building block of wireless communication systems. As a key component of physical layer design, they critically impact the expected communication capacity and wireless signal robustness. Their design is also critical for the successful roll-out of wireless standards that require a compromise between performance, efficiency, latency, and hardware requirements. This paper presents a survey of constellation design strategies and associated outcomes for wireless communication systems. The survey discusses their performance and complexity to address the need for some desirable properties, including consistency, channel capacity, system performance, required demapping architecture, flexibility, and independence. Existing approaches for constellation designs are investigated using appropriate metrics and categorized based on their theoretical algorithm design. Next, their application to different communication standards is analyzed in context, aiming at distilling general guidelines applicable to the wireless building block design. Finally, the survey provides a discussion on design directions for future communication system standardization processes.This work was supported in part by the Basque Government under Grant IT1234-19, in part by the PREDOC under Program PRE_2020_2_0105, and in part by the Spanish Government through the Project PHANTOM (MCIU/AEI/FEDER, UE) under Gran

Planning Large Single Frequency Networks for DVB-T2

[EN] The final coverage and associated performance of an SFN is a joint result of the properties of all transmitters in the SFN. Due to the large number of parameters involved in the process, finding the right configuration is quite complex. The purpose of the paper is to find optimal SFN network configurations for DVB-T2. Offering more options of system parameters than its predecessor DVB-T, DVB-T2 allows large SFN networks. However, self-interference in SFNs gives rise to restrictions on the maximum inter-transmitter distance and the network size. In order to make optimum use of the spectrum, the same frequency can be reused over different geographical areas - beyond the reuse distance to avoid co-channel interference. In this paper, a methodology based on theoretical network models is proposed. A number of network architectures and network reference models are considered here for different reception modes in order to study the effects of key planning factors on the maximum SFN size and minimum reuse distance. The results show that maximum bitrate, network size and reuse distance are closely related. In addition, it has been found that the guard interval is not the only limiting parameter and that its impact strongly depends on the rest of DVB-T2 mode parameters as well as on the network characteristics (Equivalent Radiated Power, effective height, inter-transmitter distance). Assuming that the C/N requirements are in the vicinity of 20 dB and bitrates over 30 Mbps, it has been found that the network can be as large as 360 x 360 km (delivering 39.2 Mbps) or even 720 x 720 km (delivering 37.5 Mbps). The reuse distance will also have a complex dependency on the DVB-T2 mode and especially the network parameters, ranging from below 100 to 300 km.This work has been financially supported by the Beihang University, IRT, the University of the Basque Country UPV/EHU (UFI 11/30 and program for the specialization of the postdoctoral researcher staff) and by the Spanish Ministry of Economy and Competitiveness under the project HEDYT-GBB (TEC2012-33302)

Large size FFTs over time-varying channels

[EN] In orthogonal frequency division multiplexing (OFDM) signals, the usage of large size fast Fourier transforms (FFTs) reduces the guard interval percentage, and therefore increases the data throughput reducing the data overhead. In addition, for the same pilot pattern, the distance between adjacent pilots is smaller, which will improve the channel estimation. Nevertheless, up to now, they have not been considered for delivering mobile services as the inter-carrier interference (ICI) due to the Doppler effect is very critical. The main objective is to show that taking advantage of the latest improvements in error correction techniques, it is feasible to use large size FFTs for time-varying channels. Furthermore, there is also presented a theoretical estimation for quantifying the loss due to the ICI, and finally several simulation results that reinforce the idea that large OFDM symbols are suitable for mobile channels.This work has been financially supported in part by the University of the Basque Country UPV/EHU (UFI 11/30), by the Basque Government (IT-683–13 and SAIOTEK), by the Spanish Ministry of Science and Innovation under the project NG-RADIATE (TEC2009-14201), and by the Spanish Ministry of Economy and Competitiveness under the project HEDYT-GBB (TEC2012-33302)

Comparison between Different Channel Coding Techniques for IEEE 802.11be within Factory Automation Scenarios

This paper presents improvements in the physical layer reliability of the IEEE 802.11be standard. Most wireless system proposals do not fulfill the stringent requirements of Factory Automation use cases. The harsh propagation features of industrial environments usually require time retransmission techniques to guarantee link reliability. At the same time, retransmissions compromise latency. IEEE 802.11be, the upcoming WLAN standard, is being considered for Factory Automation (FA) communications. 802.11be addresses specifically latency and reliability difficulties, typical in the previous 802.11 standards. This paper evaluates different channel coding techniques potentially applicable in IEEE 802.11be. The methods suggested here are the following: WLAN LDPC, WLAN Convolutional Codes (CC), New Radio (NR) Polar, and Long Term Evolution (LTE)-based Turbo Codes. The tests consider an IEEE 802.11be prototype under the Additive White Gaussian Noise (AWGN) channel and industrial channel models. The results suggest that the best performing codes in factory automation cases are the WLAN LDPCs and New Radio Polar Codes.This work was supported in part by the Basque Government under Grant IT1234-19, in part by the PREDOC under Grant PRE2019_099407, and in part by the Spanish Government through project PHANTOM (MCIU/AEI/FEDER, UE) under Grant RTI2018-099162-B-I00

Traffic Classification for Network Slicing in Mobile Networks

Network slicing is a promising technique used in the smart delivery of traffic and can satisfy the requirements of specific applications or systems based on the features of the 5G network. To this end, an appropriate slice needs to be selected for each data flow to efficiently transmit data for different applications and heterogeneous requirements. To apply the slicing paradigm at the radio segment of a cellular network, this paper presents two approaches for dynamically classifying the traffic types of individual flows and transmitting them through a specific slice with an associated 5G quality-of-service identifier (5QI). Finally, using a 5G standalone (SA) experimental network solution, we apply the radio resource sharing configuration to prioritize traffic that is dispatched through the most suitable slice. The results demonstrate that the use of network slicing allows for higher efficiency and reliability for the most critical data in terms of packet loss or jitter.This research was supported by the Spanish Centre for the Development of Industrial Technology (CDTI) and the Ministry of Economy, Industry and Competitiveness under grant/project CER-20191015/Open, Virtualized Technology Demonstrators for Smart Networks (Open-VERSO)

Analysis of NOMA-Based Retransmission Schemes for Factory Automation Applications

New use cases and applications in factory automation scenarios impose demanding requirements for traditional industrial communications. In particular, latency and reliability are considered as some of the most representative Key Performance Indicators (KPI) that limit the technological choices addressing wireless communications. Indeed, there is a considerable research effort ongoing in the area of wireless systems, not only from academia, but also from companies, towards novel solutions that fit Industry 4.0 KPIs. A major limitation for traditional wireless architectures is related to the harsh nature of the industrial propagation channel. Accordingly, this paper addresses these challenges by studying the reliability and latency performance of the joint use of different retransmission schemes in combination with Non-Orthogonal Multiple Access (NOMA) techniques. Two general retransmission schemes have been tested: time-based and spatial diversity-based retransmissions. An adaptive injection level NOMA solution has been combined with the retransmission schemes to improve the reliability of critical information. In all cases, a particular set of simulations has been carried out varying the main parameters, such as modulation, code rate and the injection level. Moreover, the impact of the number of transmitters in relation to the communication reliability has been analyzed. Results show that spatial diversity-based retransmissions overcome considerably the reliability obtained with time-domain retransmissions while maintaining assumable latency ratesThis work was supported in part by the Basque Government under Grant IT1234-19, in part by the PREDOC under Grant PRE_2020_2_0105, and in part by the Spanish Government through project PHANTOM (MCIU/AEI/FEDER, UE) under Grant RTI2018-099162-B-I0

Empirical Analysis of Medium Wave Field Strength Prediction in Urban Environments

[EN] This paper presents results obtained from four extensive field trials of medium wave DRM (Digital Radio Mondiale) which were carried out in Madrid (Spain), Delhi (India) and Mexico D.F. (Mexico) using different transmission frequencies. The objective is to provide medium wave field strength spatial variability values for urban environments using empirical analysis methodology. The influence of the transmission frequency on medium wave propagation in urban environments is included. Both, long and short term components of the signal spatial variability are studied characterizing wide, medium and narrow streets, and the attenuation caused by different urban fast variation occurrences is statistically featured. All the results presented in this paper are essential for future network planning of new emerging digital broadcasting services and have been validated using the Generalized Lee Method

Predictive CDN Selection for Video Delivery Based on LSTM Network Performance Forecasts and Cost-Effective Trade-Offs

Owing to increasing consumption of video streams and demand for higher quality content and more advanced displays, future telecommunication networks are expected to outperform current networks in terms of key performance indicators (KPIs). Currently, content delivery networks (CDNs) are used to enhance media availability and delivery performance across the Internet in a cost-effective manner. The proliferation of CDN vendors and business models allows the content provider (CP) to use multiple CDN providers simultaneously. However, extreme concurrency dynamics can affect CDN capacity, causing performance degradation and outages, while overestimated demand affects costs. 5G standardization communities envision advanced network functions executing video analytics to enhance or boost media services. Network accelerators are required to enforce CDN resilience and efficient utilization of CDN assets. In this regard, this study investigates a cost-effective service to dynamically select the CDN for each session and video segment at the Media Server, without any modification to the video streaming pipeline being required. This service performs time series forecasts by employing a Long Short-Term Memory (LSTM) network to process real time measurements coming from connected video players. This service also ensures reliable and cost-effective content delivery through proactive selection of the CDN that fits with performance and business constraints. To this end, the proposed service predicts the number of players that can be served by each CDN at each time; then, it switches the required players between CDNs to keep the (Quality of Service) QoS rates or to reduce the CP's operational expenditure (OPEX). The proposed solution is evaluated by a real server, CDNs, and players and delivering dynamic adaptive streaming over HTTP (MPEG-DASH), where clients are notified to switch to another CDN through a standard MPEG-DASH media presentation description (MPD) update mechanismThis work was supported in part by the EC projects Fed4Fire+, under Grant 732638 (H2020-ICT-13-2016, Research and Innovation Action), and in part by Open-VERSO project (Red Cervera Program, Spanish Government's Centre for the Development of Industrial Technology

An Empirical Comparative Study of Prediction Methods for Estimating Multipath Due to Signal Scattering from Wind Turbines on Digital TV Services

[EN] Several authors have theoretically studied the effect of wind turbines on the propagation of electromagnetic waves in the UHF band. The International Telecommunication Union also proposes a simplified model to evaluate the impact caused to television reception by a wind turbine in the Recommendation ITU-R BT.805. This paper presents an empirical study of the above mentioned prediction methods for estimating signal scattering from wind turbines in the UHF band, comparing predicted values with empirical data obtained from a DTV measurement campaign carried out in Spain. As signal scattering is independent of the transmission standard or modulation, the results are applicable to any broadcasting and wireless communication signals in the UHF band that may be affected by the multipath interference caused by a wind farm.This work was supported in part by the Basque Government under both the SAIOTEK program and the program for the training of the researcher staff (BFI08.230)

Empirical Evaluation of the Impact of Wind Turbines on DVB-T Reception Quality

[EN] This paper describes the results of two extensive measurement campaigns for evaluating the potential impact of scattered signals from wind turbines on terrestrial DTV reception quality in the UHF band. A detailed description of the different propagation channels encountered is provided. Furthermore, empirical threshold carrier-to-noise requirements for Quasi Error Free reception in the DVB-T system in the area of influence of a wind farm are presented, and the situations where a significant degradation can be found are identified and characterized.This work has been partially supported by the UPV/EHU GIC 07/110-IT-374-07, by the Basque Government under both the SAIOTEK program and the program for the training of the researcher staff (BFI08.230), by the Spanish Ministry of Science and Innovation under the project NG-RADIATE, TEC2009-14201, and by the Spanish Ministry of Industry, Tourism and Trade under the project ENGINES, TSI-020400-2010-188. ENGINES project is under the Celtic Initiative (Celtic Label CP7-005)