Fixed Wireless Access Research Articles

Long Term Fade Margin for 90% Availability in Fixed Wireless Links With Diversity

Fixed wireless access is becoming a major 5G application. We measured received power for 72 urban fixed wireless links at 5.8 GHz over a period of 48 hours each. We find that 5-minute power averages show temporal variations requiring additional fade margins close to 6 dB at the 90th percentile. The average power temporal variation was found to increase with the excess path loss of the link. We propose a model that accurately characterizes first and second order link statistics. Spatial and frequency diversity measurements allowed us to also assess the effectiveness of the corresponding fade mitigation techniques. From them we conclude that the long-term fades appear to be consistent with time-varying multipath propagation, as opposed to shadowing.

Modular Hybrid Beamforming for mmWave Fixed Wireless Access

Fixed wireless access has been spreading recently as a complement to wired or fiber solutions, and its implementation on millimeter waves has attracted attention for its potentially high data rates, achievable also in densely populated areas. New hardware and software solutions are needed to overcome various technical issues at those frequencies. We propose a novel modular hybrid beamforming (MHB) architecture, whereby, in receive mode, each module comprises a set of antennas connected to fixed analog beamformers, in turn connected by configurable switches to a smaller set of radio frequency chains. The outputs of all modules are then jointly processed by a digital beamformer. In particular, an MHB performing discrete Fourier transform beamforming for uniform linear arrays is studied. We address the problems of a) switch configuration, b) power allocation and digital beamformer design, and c) channel estimation. For both a) and b) we target the maximization of the total weighted spectral efficiency (WSE) under power and per-user average spectral efficiency (SE) constraints, and we propose greedy efficient solutions. For c) we propose a multistage scheme. We assess the MHB performance in terms of WSE, estimation accuracy, estimation overhead, and computational complexity, and compare them with existing solutions in literature.

Performance Analysis of 5G Fixed Wireless Access Networks with Antenna Diversity Techniques

An increase in the network interconnection has been observed across the world because of multimedia applications and services transmission over the Internet. Nonetheless, a huge number of homes are still experiencing irregular or no broadband connections. Fixed wireless access (FWA) offers an attractive wireless solution for offering multimedia services to various homes compared with fixed-line broadband solutions. However, matching the performance levels of the fixed-line broadband is comparatively demanding for the current access networks. Compared with the fourth-generation (4G) networks, the fifth-generation (5G) technological implementation in FWA is envisioned to give significant enhancements regarding the system capacity, coverage, and connectivity at low-latency. To fulfill the network requirements, 5G systems are anticipated to exploit higher frequency bands. However, radio propagation conditions at higher frequency bands are relatively demanding, owing to the path-loss (PL). In this paper, we discuss different network requirements of the 5G FWA system. Also, a comprehensive overview of the broadband schemes’ technical challenges is presented and we proffer viable solutions for achieving cost-effective and scalable 5G FWA solutions. Moreover, we exploit diversity scheme and present a closed-form expression for the multiple-input, multiple-output scheme in which the PL and beamforming schemes are considered. The accuracy of the proposed closed-form expression is validated by Monte-Carlo simulation over different antenna configurations and signal-to-noise ratios. Based on the presented models, we evaluate and simulate the PL and average transmission rates for different use cases. Simulation results show significant performance improvement compared with a single-input single-output configuration. Apart from being capable of enhancing system performance, the proposed model can be employed for an arbitrary number of transmit and receive antennas. The model is anticipated to pave the way for more robust performance evaluation of multi-antenna-based 5G use cases.

MmWave IEEE 802.11ay for 5G Fixed Wireless Access

Fixed wireless access (FWA) utilizing both licensed and unlicensed millimeter wave (mmWave) spectrum is considered a key technology that can lead to the early deployment of the fifth-generation new-radio (5G-NR) networks. 5G FWA can provide easy installation of network infrastructure and ubiquitous high-speed Internet access at low cost compared to the conventional broadband fixed access networks. In this article, we investigate the mmWave distribution network (mDN) use case that has been standardized recently by the IEEE 802.11ay standard as an alternative 5G FWA solution. Specifically, we provide a comprehensive tutorial view of the considered new protocol specifications and design elements of the mDN. We also highlight some challenging research issues in the field of the mDN. Finally, we provide a case study based on the investigation of the mDN where a low-complexity concurrent transmission protocol is proposed to enhance the network performance while mitigating the interference.

Measurements and path loss models for a TD-LTE network at 3.7 GHz in rural areas

This paper presents an extensive path loss measurement campaign carried out in rural areas at 3.7 GHz, including line-of-sight (LOS) and non-LOS conditions. For this purpose, a commercially established fixed wireless access (FWA) network is exploited, operating with time-division long term evolution configuration. Furthermore, various models are examined and validated regarding their ability to predict accurately the path loss. The results reveal that the standard propagation model (SPM) achieves the best performance, thus being an attractive option for planning rural FWA links. The WINNER II and 3GPP/ITU-R models exhibit very good performance, as well. From the statistical assessment, the shadow fading follows the Lognormal distribution with a standard between 4.6 and 5.4 dB. An almost excellent fit is obtained regardless of the diverse propagation conditions in the specific area. Finally, from the model evaluation was concluded that SPM is highly recommended as the best option for a precise network dimensioning and planning.

Suburban Fixed Wireless Access Channel Measurements and Models at 28 GHz for 90% Outdoor Coverage

Achieving adequate coverage with high gain antennas is key to realizing the full promise of the wide bandwidth available at cm/mm bands. We report extensive outdoor measurements at 28 GHz in suburban residential areas in New Jersey and Chile, with over 2000 links measured for same-street link types (vegetation blocked LOS) from 13 streets and other-street link types (true NLOS) from 7 streets, using a specialized narrowband channel sounder at ranges reaching 200 m. The measurements, applicable to fixed wireless access, involved a 55$^\circ$ transmit antenna placed on the exterior of a street-facing window and a 10$^\circ$ receive horn antenna spinning on top of a van mast at 3 m height, emulating a lamppost-mounted base station. Measured path gain-distance dependence is well represented by power-law models, and azimuth gains at the base are degraded through scattering by more than 4.3 dB for 10% of links. It was found that, with 51 dBm EIRP at the base station and 11 dBi antenna at an outdoor mounted terminal, 1 Gbps downlink rate can be delivered up to 100 m from a base station deployed in the same street with 90% coverage guarantee.

Millimeter-Wave Fixed Wireless Access Using IEEE 802.11ay

IEEE 802.11ay defines new PHY and MAC specifications that enable 100 Gb/s communications in the 60 GHz millimeter-wave (mmWave) band. Among the various use cases supported by IEEE 802.11ay, fixed wireless access, a cost-efficient high-performance alternative and/ or complement to conventional fixed access, differentiates itself due to its unique requirements and characteristics. In this article, our goal is to identify and describe key elements incorporated into IEEE 802.11ay, including scheduling, beamforming, and link maintenance, that efficiently support fixed wireless access. IEEE 802.11ay is thus a viable and strong candidate to form the basis of future generations of standards-compliant (i.e., non-proprietary) mmWave fixed wireless access networks.

Greenfield Design in 5G FWA Networks

With the arrival of 5G, Fixed Wireless Access, which aims at providing households with broadband internet access using mobile technology, has become a relevant use case. Current greenfield design techniques are not optimal since they target at optimizing the radiofrequency configuration for the whole household, sometimes at the expense of other households. However, optimizing only the spot where to install the antenna of the customer premises equipment is enough for Fixed Wireless Access networks. This letter presents an enhancement of automatic greenfield design methodology so that, apart from finding the location where to deploy network base stations and the optimal configuration of network parameters, the optimal location where to deploy customer premises equipment is also determined. A greenfield design exercise has been carried out in a real scenario proving that the proposed method both improves the final network performance and reduces the required deployment economic costs compared with state-of-the-art methodology.

Design and analysis of triple band circular patch antenna

This paper presents a circular slotted patch antenna resonating at three frequencies namely 1.8 GHz, 2.4 GHz and 5.4 GHz. The antenna is fabricated using Roger RT Duroid 5870 substrate having a thickness of 1.5 mm. The multiband behavior is achieved by etching slots on the patch. The measured antenna gains at the three frequencies are 5.5 dBi, 7.8 dBi and 7.9 dBi respectively. This paper extends its contribution by incorporating and discussing the resonation using the higher order modes. The designed antenna is suitable to be used for Global System for Mobile communication (GSM), Wi-Fi applications, Bluetooth, WLAN, Radio Local Area Network (RLAN) and Fixed Wireless Access systems (FWAS).

Evaluating the interference from fixed wireless access TDMA systems into HAPS systems: a probabilistic approach

This study presents a probabilistic model to assess the co-channel interference produced by multiple transmitters of a fixed wireless access network into a high altitude platform stations (HAPS) victim receiver. The authors propose an alternative probabilistic approach that avoids the worst case assumptions usually considered in traditional interference calculation methods, by considering the random modelling of some of the technical parameters involved. More specifically, the geographic positions of fixed wireless access system transmitters are modelled by a two-dimensional point process and their antenna gains in the sidelobe region are modelled as gamma distributed random variables. The proposed method is validated by comparing the minimal operating distance resulting from the traditional deterministic interference calculation methods and that obtained with th proposed approach. Results corresponding to the four possible interfering scenarios indicate that the proposed probabilistic approach leads to a reduction in coordination distances.

Comparative techno-economic evaluation of LTE fixed wireless access, FTTdp G.fast and FTTC VDSL network deployment for providing 30 Mbps broadband services in rural areas

In rural areas in Europe, the deployment of High-Speed Broadband access networks lags far behind the urban and suburban areas due to difficulties of fiber rollout in the final meters. FTTC VDSL is the most widespread technology used for NGA network deployments in Europe but the coverage of VDSL networks is still limited in rural areas. FTTdp networks using G.fast have been proposed as a cost-effective and future-proof alternative to FTTH and FTTB especially in rural areas where FTTC and VDSL cannot always deliver service speeds of 30 Mbps which is the minimum bandwidth defined in the European Digital Agenda as a target to be met by 2020. However, the new target of EU Commission for Gigabit Society and 100 Mbps connections, upgradable to 1 Gbps, for all households in 2025 are unlikely to be achieved by VDSL Vectoring and other copper-based technologies. On the other hand, Fixed Wireless Access (FWA) networks based on LTE technology can be used as a “last mile” solution to provide high-speed broadband access to areas where fixed broadband is limited. LTE technology offers high-speed connections able to support internet browsing and IP services, while it can theoretically support up to 300 Mbps depending on network load and sharing. Thus, it can be considered a viable alternative to other fixed network solutions especially when considering future upgrades to 5G networks that promise gigabit speeds per user. In this paper, a techno-economic study is performed to assess the feasibility of an FWA network deployment based on LTE technology in comparison to FTTdp G.fast and FTTC VDSL network rollout for delivering service speeds of 30 Mbps in rural areas. A variety of different population density, competition and regulation policy scenarios is considered. Cash flow results are presented and standard financial indexes for the business cases are discussed. The results are being assessed through a sensitivity and risk analysis to determine the most influential factors on the return on the investment. Furthermore, the (non) profitability of these cases and the subsidization needed from structural funds are analyzed. The results are aimed to contribute to the debate over network evolution scenarios among academia, industry, regulators, policy makers and governments.

Optical Transport Network Design for 5G Fixed Wireless Access

The fifth generation (5G) of mobile technology, 5G is anticipated to be a significant leap in the evolution of mobile communication. 5G will be designed to attain 1000 times higher data volumes, 10 times lower latency, and 100 times more connected devices than its predecessor, 4G. Due to 5Gs ability to sustain high bandwidth per unit area, 5G is considered to be a cost-efficient solution to provide fixed wireless access (FWA) to households on a large scale. FWA is seen as an attractive alternative for fixed broadband access in scenarios where last mile access based on wired technologies is not economically viable. While approaches for enhancing user experience in a 5G FWA environment are investigated in the research community, the problem of providing cost-effective high capacity transport for FWA deployments still remains a major challenge. This is particularly challenging due to diverse transport network architectures and requirements imposed by different 5G deployment models. This paper addresses this problem by formulating a generalized joint-optimization framework to simultaneously plan wireless access and optical transport for 5G FWA networks in order to minimize the deployment cost while meeting various network requirements. We demonstrate the applicability of the proposed framework by applying it to a real scenario with a range of deployment options and where different types of optical x-haul solutions are considered. The results provide a cornerstone for deployment strategies that will be imperative for realizing a future-proof and cost-effective broadband access network.

Suburban Residential Building Penetration Loss at 28 GHz for Fixed Wireless Access

Fixed wireless access at mm/cm bands has been proposed for high-speed broadband access to suburban residential customers and building penetration loss is a key parameter. We report a measurement campaign at 28 GHz in a New Jersey suburban residential neighborhood for three representative single-family homes. A base antenna is mounted at 3-m height, emulating a base station on a lamppost, moves down the street up to 200 m. A customer premises equipment (CPE) device, acting as relay to provide indoor coverage throughout the desired area, is mounted either on the exterior of a street-facing window or 1.5 m behind the window. The median indoor-outdoor path gain difference, corresponding to the extra loss by moving the window-mounted CPE indoor, is found to be 9 dB for the house with low-loss materials and plain-glass windows, and 17 dB for the house with low-emissivity windows and foil-backed insulation. These losses are in addition to other losses (e.g., vegetation blockage) in comparison to free space propagation.

Path Loss Prediction Model for GSM Fixed Wireless Access

This research investigated the effect of building materials on GSM signals quality. Measurements were conducted on MTN, Glo, Airtel and Etisalat networks using Radio Frequency Signal Tracker on six different building patterns. The results showed that building with alucoboard wall cladding had the highest signal loss while the sandcrete building/unrusted corrugated iron sheet roof had the least signal loss. Also, a model to predict signal penetration through building walls was developed. It was developed using the principles of Fresnel Refraction Coefficient and the knife-edge diffraction. The total losses from the transmitter to the receiver was modelled as a combination of three different effects; losses due to free-space propagation from transmitter to building; the penetration loss was modelled as a combination of the wall penetration loss and the diffraction loss. The results show that despite the condition of the building walls, movement of people in the environment/room also affected the wireless signal quality as well as the chairs and gadgets in the room. The indoor signal path loss in the rooms increased from when the walls were plastered and continued until when the walls were covered with curtains, both rooms reduced by 4dBm. The mean squared error ranged between 1.6dBm and 2.1dBm with a standard deviation between 11.1 and 11.5.

On 5G Radio Access Network Slicing: Radio Interface Protocol Features and Configuration

Network slicing is a fundamental capability for future Fifth Generation (5G) networks to facilitate the cost-effective deployment and operation of multiple logical networks over a common physical network infrastructure in a way that each logical network (i.e. network slice) can be customized and dimensioned to best serve the needs of specific applications (e.g. mobile broadband, smart city, connected car, public safety, fixed wireless access) and users (e.g. general public, enterprise customers, virtual operators, content providers). The practical realization of such capability still raises numerous technical challenges, both in the Core and RAN parts of the 5G system. Through a comprehensive analysis of the impact that the realization of RAN slicing has on the different layers of the radio interface protocol architecture, this article proposes a framework for the support and specification of RAN slices based on the definition of a set of configuration descriptors that characterize the features, policies and resources to be put in place across the radio protocol layers of a next-generation RAN node.

Optical Transport Solutions for 5G Fixed Wireless Access [Invited

With the advent of 5G, fixed wireless access (FWA) has emerged as a promising candidate for rolling out fixed broadband services. By means of radio simulations, we define a 5G radio deployment scenario for FWA that can meet the service requirements of future fixed broadband access. Different transport requirements imposed by different radio access network (RAN) split options are considered and a broad range of optical transport technologies/systems to support the FWA scenario is analyzed. For higher-layer RAN split options, we find that conventional 10G passive optical networks (XG-PONs) and coarse wavelength-division multiplexing (CWDM) technologies are the most cost effective. CWDM provides improved support for low-latency services while XG-PON facilitates future migration to fiber to the home. For lower-layer RAN splits, point-to-point (PtP) fiber or PtP-WDM is required. In the considered scenario, CWDM and PtP technologies are found to be the most cost effective.

Modeling of Dynamic Effect of Vegetation for Fixed Wireless Access System

This paper presents the results of investigation of fixed wireless access performance based on IEEE802.16 standard in wide campus environment. Measurements have been conducted at 5.8 GHz that includes various parameters in different outdoor environments to study the effect of vegetation, street and building. The primary goal of this work is to investigate the performance of received signal strength during daytime and night. Based on the measurement result, small signal deviation recorded for daytime and night. The channel capacity is found varied with environment conditions, wind speed, humidity and temperature. The extent of changes based on blockage is examined as well. The excess loss due to vegetation is ranging from 5.14 to 31.17 dB. Within the research framework, the empirical values obtained are to be scintillated with the statistical models. Henceforth, it is vital to discover the interrelation within the outstanding statistical distributions, such as log-normal, Gaussian, Rayleigh, Rician and Nakagami distributions. In such models, it is found that log-normal distribution best fit the path and excess loss models.

Path Loss Prediction Model for GSM Fixed Wireless Access

This research investigated the effect of building materials on GSM signals quality. Measurements were conducted on MTN, Glo, Airtel and Etisalat networks using Radio Frequency Signal Tracker on six different building patterns. The results showed that building with alucoboard wall cladding had the highest signal loss while the sandcrete building/unrusted corrugated iron sheet roof had the least signal loss. Also, a model to predict signal penetration through building walls was developed. It was developed using the principles of Fresnel Refraction Coefficient and the knife-edge diffraction. The total losses from the transmitter to the receiver was modelled as a combination of three different effects; losses due to free-space propagation from transmitter to building; the penetration loss was modelled as a combination of the wall penetration loss and the diffraction loss. The results show that despite the condition of the building walls, movement of people in the environment/room also affected the wireless signal quality as well as the chairs and gadgets in the room. The indoor signal path loss in the rooms increased from when the walls were plastered and continued until when the walls were covered with curtains, both rooms reduced by 4dBm. The mean squared error ranged between 1.6dBm and 2.1dBm with a standard deviation between 11.1 and 11.5.

Millimeter-wave gigabit broadband evolution toward 5G: fixed access and backhaul

As wireless communication evolves toward 5G, both fixed broadband and mobile broadband will play a crucial part in providing the gigabit-per-second infrastructure for a connected society. This article proposes an MGB system as the solution to two critical problems in this evolution: last-mile access for fixed broadband and small cell backhaul for mobile broadband. The key idea is to use spectrum that is already available in the millimeter-wave bands for fixed wireless access with optimized dynamic beamforming and massive MIMO infrastructure to achieve high capacity with wide area coverage. This article explains the MGB concept and describes potential array architectures for realizing the system. Simulations demonstrate that with 500 MHz of bandwidth (at 39 GHz band) and 28 dBm transmission power (55 dBm EIRP), it is possible to provide more than 11 Gb/s backhaul capacity for 96 small cells within a 1 km radius.

Channel capacity investigation of a linear massive MIMO system using spherical wave model in LOS scenarios

Massive multiple-input multiple-output (MIMO) is a key technology for the 5th generation (5G) of wireless communication systems. The traditional plane wave channel model (PWM) is often not suitable for the large antenna structure, and in certain cases should be replaced by the more accurate spherical wave model (SWM). By using the spherical wave characterization method, this paper investigates the channel capacity performance of a linear massive MIMO system in line-of-sight (LOS) scenarios. Two types of access settings, the point to point (PTP) system and multi-user (MU) system, are considered. In the PTP setting, a geometrical optimization is performed to obtain configurations that are able to generate a full rank channel matrix for a linear massive MIMO system, which yields full spatial diversity even in LOS scenarios. Compared with the approximate and commonly applied rank-1 PWM, this is very useful for fixed wireless access and radio relay systems requiring high throughput. For the MU case, we compare the eigenvalue distributions of the LOS channels using the plane wave and spherical wave characterization method, and sum rate results are obtained by Monte Carlo simulations. The results show that MU systems using the more realistic and accurate SWM can achieve a higher sum rate than results from the PWM. This is beneficial and informative when designing massive MIMO wireless networks.