MATLAB-Based PHY Simulators for Performance Study of the IEEE 802.11ah/af Systems

In recent years the military has been developing mobile Multiple-Input Multiple-Output (MIMO) technology. MIMO communications are attractive due to enhanced performance in urban, high multi-path environments which can cause substantial performance degradation in Single Input Single Output (SISO) communications. In this paper, results of a MIMO mobile network of 2 antenna MIMO radio systems employing spatial diversity, with four nodes in a hub-spoke configuration are given. The purpose was to validate MIMO mobile network performance over that of a SISO network. The experiments were conducted in several different environments such as reduced line of sight, heavily obstructive with buildings and dense foliage and high multipath environments and for On-The-Move (OTM) and At-The-Halt (ATH) test scenarios. Tests were conducted in SISO, MIMO and receiver diversity (RXD) modes for comparison and to show backwards compatibility to SISO radios. The paper highlights the advantages of the MIMO mobile network technology, showing improved throughput, reliable communications and coverage extension in mobile and reduced line of sight scenarios. The results consistently showed on average a 10% to 15% throughput improvement in MIMO over SISO given the same transmit power and operating range.

3rd Generation Partnership Project (3GPP) has recently completed the specification of the Long Term Evolution (LTE) standard. Majority of the world's operators and vendors are already committed to LTE deployments and developments, making LTE the market leader in the upcoming evolution to 4G wireless communication systems. Multiple input multiple output (MIMO) technologies introduced in LTE such as spatial multiplexing, transmit diversity, and beamforming are key components for providing higher peak rate at a better system efficiency, which are essential for supporting future broadband data service over wireless links. Further extension of LTE MIMO technologies is being studied under the 3GPP study item to meet the requirement of IMT-Advanced set by International Telecommunication Union Radiocommunication Sector (ITU-R). In this paper, we introduce various MIMO technologies employed in LTE and provide a brief overview on the MIMO technologies currently discussed in the LTE-Advanced forum.

MIMO (Multiple Input Multiple Output) enabled systems are characterized by higher reliability and transmission rates, as compared to conventional SISO (Single Input Single Output) systems. However, unless administered properly, the MIMO technology may not facilitate very high throughputs on point-to-point wireless links. Therefore, it becomes imperative for the network architect to design such networks in ways that fully exploit the inherent properties of MIMO. In this paper, we first conduct an extensive experimental study, using a powerful hardware platform, in order to understand the behavior of MIMO links in different topological scenarios. Our experiments involve scenarios with MIMO links in isolation, as well as in competition with other MIMO and SISO links. Second, we perform measurements with different commercial platforms towards assessing the ability of each platform to efficiently support the MIMO technology. Based on our experimental observations we deduce that the CPU processing speed of the underlying hardware platform is an important factor that can hide the performance benefits of a MIMO enabled tranceiver. We comment on the applicability of the different hardware choices that we test; furthermore, we suggest the most appropriate choice for building a MIMO testbed, taking into account the cost, the extend-ability and the re-usability of the selected platform. Finally, having adopted this choice in our testbed design, we provide a description of our testbed architecture.

This paper proposes a traceable and practical approach to measure the modulation error ratio (MER) and the power level of digital radio frequency (RF) TV signals. We use calibrated vector signal generator and sampling oscilloscope as both reference and standard to build the MER measurement system and improve the time-base error correction algorithm to increase the accuracy simultaneously; According to the characteristic of digital RF signal which spectrum is similar to noise in a specified frequency band, we adopt an algorithm with spectrum transform and in-band integral to describe the power distribution of frequency components composing the signals. It provides distinct traceable chains between measured physical quantities and metrological benchmark. The experimental results demonstrate that this approach is feasible.

The advent of 5G technology has revolutionized wireless communication, offering unprecedented data rates, reduced latency, and enhanced connectivity. A critical component driving these advancements is Multiple-Input Multiple-Output (MIMO) technology. MIMO utilizes multiple antennas at both the transmitter and receiver ends to improve communication performance. In the context of the Internet of Things (IoT), MIMO plays a pivotal role in enhancing network efficiency, reliability, and capacity and can improve system capacity and reduce interference between different users. By leveraging MIMO, IoT devices can achieve higher data throughput and better signal quality, even in challenging environments. This is particularly important for IoT applications that require real-time data transmission and low latency, such as smart cities, autonomous vehicles, and industrial automation. Additionally, MIMO technology helps in mitigating interference and improving spectrum utilization, making it an essential enabler for the massive connectivity demands of IoT networks in the 5G era. However, due to the high channel dimension, complex channel estimation and precoding algorithms in the system, the system hardware and software overhead will increase. The precoding algorithms of massive MIMO systems are divided into three types: digital, analog and hybrid. The three types of precoding algorithms are summarized and compared, and the advantages and disadvantages of different precoding algorithms and applicable scenarios are summarized. The channel estimation schemes are divided into training estimation and blind estimation, and the advantages and disadvantages of the two types of schemes are summarized. It is pointed out that the reasonable use of the channel sparsity of massive MIMO can improve the quality of channel estimation and reduce the estimation overhead.

Sub-1 GHz bands have been used for many years and now some of them will be reallocated for new applications, including the fifth generation (5G) wireless communication systems and beyond, Internet of Things (IoT), smart grid, etc. As the well-known path-loss (PL) models are mainly applicable in 2-6-GHz frequency range, a new channel measurement campaign is needed to study the propagation characteristics at sub-1 GHz bands. In this article, we conduct fixed-to-mobile wideband channel measurements at 400-600-MHz bands in urban and suburban scenarios using the time domain channel sounder. As the interference and noise signals are severe, the transmitted waveform is carefully designed to enlarge the system dynamic range. Meanwhile, ray tracing simulation is applied to construct the measurement environments and do the mutual verification with measurement results. The two-slope PL model and lognormal shadowing fading model are proposed for large-scale fading channel modeling. The root mean square (RMS) delay spread (DS), number of paths, and diffraction characteristics are also analyzed. The results will have great importance for the coming new applications at sub-1 GHz bands.

Chapter 6 - Internet of Things (NB-IoT and Massive MTC)

In this paper, the STBC (Space-Time Block Codes) transmission technique is used in order to evaluate the link availability and transmission quality of multi antenna systems that operate under various channel conditions. The propagation channel follows the IEEE 802.11n specifications. The influence of the diversity order and the spatial correlation is investigated in terms of error performance and throughput. The efficient use of the space and the power resources leads to significant improvement in the link reliability, if channel state is available at the transmission. The throughput enhancement of a 2×2 MIMO system relatively to the basic SISO (Single Input Single Output) mode is evaluated considering a fix antennas separation and different channel models.

The single frequency network (SFN) has been assumed worldwide by telecommunication operators to save radio frequency resources and homogenize the network. Its applications have transcended the digital terrestrial television and digital radio to become part of the key techniques of the broadband and broadcast convergence for LTE-A, 5G and beyond. However, the transition from a multi frequency network (MFN) to an SFN involves multiple measurement campaigns and tuning of the network to achieve the expected up-performance and quality of service. This paper aims to propose a machine learning model to predict the SFN performance from the legacy MFN parameters. The model is based on regression and classification machine learning algorithms concatenated in three consecutive stages to predict SFN electric-field strength, modulation error ratio and gain. The training and test processes are performed with a dataset of 389 samples from an SFN/MFN trial in Ghent, Belgium. The best performance is obtained with concatenating gradient boosting, random forest, and linear regression, which allows predicting the SFN electric-field strength with an R-2 of 92%, the modulation error ratio with 95%, and SFN gain with 87% from only MFN and position data. Besides, the model allows classifying the data points according to positive or negative SFN gain with an accuracy of 93%.

Wireless Physical Layer Identification (WPLI) aims at identifying or classifying authorized devices based on the unique Radio Frequency Fingerprints (RFFs) to guarantee physical-layer security between each individual device. WPLI is a promising technique in the security area of Internet of Things (IoT), which avoids the burden of conventional software-level security in IoT on the computation capability, on-chip storage and power consumption of devices. Moreover, WPLI directly extracts the RFFs from radio frequency signals at physical layer, which breaks the software-level security barriers of heterogeneous device networks in IoT. However, in the existing works in WPLI, a general work focusing on theoretical characterization of performance WPLI systems in IoT is still in absence. In this work, we evaluate the performance of WPLI in IoT by thoroughly characterizing user capacity of WPLI system as the metric. We utilize the concept of IoT by combining multiple devices to represent one user's secure identity to increase the user capacity of WPLI system. Based on the information-theoretic tool we proposed, the changes in user capacity of WPLI is characterized over typical real-world scenarios according to different number of devices assigned for one user. Various field experiments on classification performance of a practical multi- user-multi-device WPLI system with are conducted to validate the user capacity characterization for each scenario.

Remote control and monitoring systems provide many useful operating advantages in industrial automation and demand highly reliable and secure communication means. Their widespread use is, however, limited because of the high cost of current communications in use making them economically infeasible. Hence, there is a need to develop new low cost communication and control concepts by making such solutions economically feasible. In this paper, we present a scheme for implementing reliable wireless communication links for application of remote control and monitoring system based on current available commercial wireless communication networks, e.g. GPRS/EDGE/UMTS. The reliability enhancement over wireless networks has been proposed and its performance has been studied. This paper examines the proposed solution by means of both analytical and numerical evaluation, and has shown that the demanded reliability performance can be met by using only commercial wireless communication networks

LoRa® and LoRaWAN are one of the most common wireless technologies used today in the Internet of Things. If until now LoRa was strictly used in sub-GHz bands, a new version has been released for the 2.4 GHz band that does not have any duty cycle restrictions and that allows the use of higher datarates, which opens the door to the deployment of new applications (such as asset tracking or indoor localization). In this paper, we present the first extensive evaluation of LoRa 2.4 GHz in a typical indoor environment, both in the presence and lack of human and WiFi activities. We run an exhaustive evaluation of all 128 possible combinations of the different LoRa physical parameters (spreading factor, bandwidth and coding rate) and we show that despite the use of higher frequency, LoRa is capable of maintaining a good connectivity throughout the building, similar to what was observed in sub-GHz bands. Still, some configurations were clearly affected by the daily life activities in the building during the working hours of weekdays.

This paper characterizes and analyses the link budget requirements for the conformal capsule antenna in the medical capsule imager system. A link budget is developed for the capsule system based on certain parameters (frequency, SAR, power limitations) and it is shown that using the present antenna system; a reliable communication link can be developed for indoor communication for bio-telemetry applications. The polarization diversity exhibited by the conformal capsule antenna is tested and compared to simple dipole design. Due to diverse polarization, a reliable link is obtained irrespective of the capsule location and orientation and this study is discussed in detail.

Mobile computing devices require reliable wireless communication links, whereby data rates, transmission range, and power consumption fit the particular needs of the various types of devices. Proper designs of physical layer functions and medium access control mechanisms are crucial for efficient connectivity and coexistence among all participants in a communication cell. We describe a solution for reliable wireless infrared connectivity based on infrared channel reciprocity. Robust header signalling, and variable data rate coding.

Wireless links are characterized by fluctuating quality leading to variable packet error rates which are orders of magnitude higher than the ones of wired links. Therefore, it is of paramount importance to investigate the limitations of using 5G wireless links for internet of things (IoT) applications. 5G wireless links in IoT need to assure determinism of process flows via realtime communication anytime and anywhere, which is an utmost requirement for multiple verticals like automotive, industrial automation and aerospace. Based on a space-time approach, in this work, we provide novel definitions of wireless link availability and reliability, assuming a number of access points (APs) and end points (EPs) deployed over a fixed area. Our objective is to analyze the availability of a service in both domains. In the space domain, we characterize spatially available areas consisting of all locations that meet a performance requirement with confidence. In the time domain, we propose a channel allocation scheme accounting for the spatial availability of a cell. To emphasize the incurred space-time performance trade-offs, numerical results are presented, also highlighting the effect of different system parameters on the achievable link availability and reliability.