Wi-Fi may be coming soon to a lamppost near you
IMAGE: NIST COMMUNICATIONS RESEARCHERS TRAVELED TO DOWNTOWN BOULDER, COLORADO, TO VERIFY THEIR CHANNEL MODEL FOR EVALUATING HIGH-FREQUENCY WIRELESS NETWORK DESIGNS. SUNG YUN JUN IS CHECKING THE ALIGNMENT OF THE TRANSMITTER, MOUNTED 6 METERS HIGH ON A MAST, WITH THE RECEIVER ANTENNA ARRAY ON THE ROOF OF THE BLUE VAN. DEREK CAUDILL, BARELY VISIBLE INSIDE THE VAN, IS PREPARING SOFTWARE PROGRAMS TO COLLECT MEASUREMENT DATA. JUSTIN SADINSKI, IN A YELLOW VEST, IS CHECKING EQUIPMENT ON THE MASTS. view more
CREDIT: NIST
As Wi-Fi is deployed more widely in cities, and perhaps at higher frequencies, it may depend on an abundant urban asset: streetlight poles.
To help ensure these networks work well, researchers at the National Institute of Standards and Technology (NIST) developed and verified a novel model that will help wireless communications providers analyze how high to attach Wi-Fi equipment to light poles.
In general, the NIST team found that the optimal height depends on transmission frequency and antenna design. Attaching equipment at lower heights of around 4 meters is better for traditional wireless systems with omnidirectional antennas, whereas higher locations 6 or 9 meters up are better for the latest systems such as 5G using higher, millimeter-wave frequencies and narrow-beam antennas.
An international group, the Telecom Infra Project, is promoting the idea of making Wi-Fi available over the unlicensed 60 gigahertz (GHz) frequency band by installing access points on light poles. A technical challenge is that signals in this band, which are higher than traditional cellphone frequencies, are sparse and tend to scatter off rough surfaces.
Until now, measurements of 60 GHz urban channels have produced limited data. NIST developed a channel model for tracking transmissions that recognizes the sparse, scattery features of these signals and uses a novel algorithm for analyzing the measured paths that extends beyond the usual parameters of signal delays and angles to include receiver locations. The model’s prediction accuracy is comparable to that of more complicated methods.
NIST researchers traveled to downtown Boulder, Colorado, to test their model against actual channel measurements. The measurements were recorded at 4, 6 and 9-meter antenna heights to investigate the trade-offs. The model matched real-world measurements very well.
“We verified the model we developed and used measurements from downtown to prove this point further,” said Derek Caudill, an electronics engineer who worked on the project at NIST. “This work shows that by using our model, someone like a cell provider can account for various advantages and disadvantages of 60 GHz access points and signals on light poles in urban environments.”
The team used custom NIST equipment called a channel sounder, with a stationary transmitter mounted on a mast and a mobile receiver on the roof of a van. The transmitter and receiver are both topped with an array of electronically switched antennas with defined 3D radiation patterns. The sounder can precisely measure many radio channel characteristics and has a unique ability to measure the time dynamics — how the properties of the waves change over time as the receiver moves — of a millimeter-wave channel even when in motion.
The researchers were especially interested in data on how signals spread across physical space. Large spreads are generally considered bad as they indicate multiple received signals and more interference. It is generally better to have one clear path for communication.
“Our data show that those spreads are wider at higher heights,” NIST engineer Jelena Senic said. “This means that with fewer obstructions between transmitter and receiver, the power is more distributed in space.”
For conventional wireless systems with omnidirectional antennas, the smaller spreads are preferable to avoid interference, which means Wi-Fi equipment should be mounted at lower heights on lampposts.
“However, the next-generation wireless systems will operate at millimeter-wave frequencies and should employ highly directional antennas with very narrow beams, or pencil beams,” Senic said. “With this configuration, transmitter and receiver will steer their narrow beams in order to find the best possible link; that is, the propagation path that has maximum power. In this case, a higher angular spread is preferable because it will provide diversity in space; that is, transceivers will have the ability to steer beams in more directions in order to find the best link.”
NIST researchers went a step further and recorded the measurement data on the NIST campus to validate that the new model could be applied to different environments. Results on campus were comparable to downtown, substantiating that the model can be generalized to different environments and use cases.
Paper: S.Y. Jun, C. Lai, D. Caudill, J. Wang, J. Senic, N. Varshney and C. Gentile. Quasi-Deterministic Channel Propagation Model for 60 GHz Urban WiFi Access from Light Poles. IEEE Antennas and Wireless Propagation Letters. Published online April 29, 2022. DOI: 10.1109/LAWP.2022.3171503
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Quasi-Deterministic Channel Propagation Model for 60 GHz Urban WiFi Access from Light Poles
Advancing beyond 5G in wireless communications
IMAGE: SCHEMATIC ILLUSTRATION OF THE SIMULTANEOUSLY TRANSMITTING AND REFLECTING RIS ELEMENT view more
CREDIT: INTELLIGENT AND CONVERGED NETWORKS
From 3G to 4G to 5G, wireless communications are evolving, and the next step is underway. What will constitute 6G, and how will it work with existing infrastructure? An international collaboration set out to begin answering such questions and published their investigation on April 29 in Intelligent and Converged Networks at DOI: https://doi.org/10.23919/ICN.2022.0005.
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“Despite the massive roll-out of 5G networks worldwide, which provide higher flexibility and spectrum/energy efficiency compared to their fourth-generation counterparts, it is inevitable that the sixth generation — 6G — of wireless networks, expected around 2030, and beyond will require more radical communication paradigms, especially at the physical layer,” said paper author Ruiqi Liu, master researcher with the Wireless Research Institute, ZTE Corporation.
“When we review the candidate technologies for next generation networks, we believe that reconfigurable intelligent surface is among the most promising technologies that will make their way into 5G-advanced and 6G standards and eventually into future networks.”
A reconfigurable intelligent surface (RIS) is a planar structure with individually programmable components, allowing for dynamic control at any single point. The RIS can reroute an incoming signal to precisely hit the intended recipient for improved coverage or couple it with another for boosted connection. The circuits making up the cell units of the RIS are relatively cheap, according to Liu, and since the cells are passive, the RIS is also more energy efficient than its predecessors.
“The incorporation of RISs in wireless networks has been recently advocated as a revolutionary means to transform any wireless signal propagation environment to a dynamically programmable one for various networking objectives,” Liu said. “Currently, the global standards of wireless communications, mainly specified by the 3rd-Generation Partnership Project (3GPP) that unites telecommunication standard development organizations to establish the mobile broadband standard, has not explicitly included RIS as a feature. However, RIS can be evolved from the current work on network controlled repeaters and can be deployed in a standard transparent way for current networks — if it is compatible with all current designs and doesn't rely on any new signaling.”
Many 3GPP partners are analyzing RISs in some way, Liu said, including studying and specifying use cases, deployment scenarios, channel models and more, as well as technical challenges and requirements. His team reviewed the latest advances in RIS hardware architectures and their operational considerations, as well as the most recent developments in the modeling of RISs and RIS-empowered wireless signal propagation. They also presented the channel estimation approaches for such systems, which help determine how signals can most effectively and securely be sent.
“Future networks will be greener, more affordable and intelligent because of the advantages RIS can provide, so we highlighted important aspects of RIS in this paper to provide an understanding of this technology and how the wireless network will evolve towards the next generation,” Liu said. “We believe that the current standardization activities will help to mature this technology and pave way to its commercialization in the future. Currently, though, RIS is still a dynamic research topic under study, with many possible options to explore. Many key issues still need to be solved before launching RISs commercially.”
Next, Liu said the researchers plan to examine the key issues of channel modelling, estimating and feedback in depth, as well as review different hardware architectures, as part of the global standardization effort.
Other contributors include Mengnan Jian, Wireless Research Institute, ZTE Corporation; George C. Alexandropoulos, Department of Informatics and Telecommunications, National and Kapodistrian University of Athens, Greece; Ertugrul Basar, Communications Research and Innovation Laboratory (CoreLab), Department of Electrical and Electronics Engineering, Koc. University, Turkey; Chongwen Huang, College of Information Science and Electronic Engineering, Zhejiang University, China; Yuanwei Liu, School of Electronic Engineering and Computer Science, Queen Mary University of London, England; and Chau Yuen, Engineering Product Development (EPD) Pillar, Singapore University of Technology and Design.
The EU H2020 RISE-6G partly supported this research.
The paper is also available on SciOpen (https://www.sciopen.com/home) by Tsinghua University Press.
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About Intelligent and Converged Networks
Intelligent and Converged Networks is an international specialized journal that focuses on the latest developments in communication technology. The journal is co-published by Tsinghua University Press and the International Telecommunication Union (ITU), the United Nations specialized agency for information and communication technology (ICT). Intelligent and Converged Networks draws its name from the accelerating convergence of different fields of communication technology and the growing influence of artificial intelligence and machine learning.
About SciOpen
SciOpen is a professional open access resource for discovery of scientific and technical content published by the Tsinghua University Press and its publishing partners, providing the scholarly publishing community with innovative technology and market-leading capabilities. SciOpen provides end-to-end services across manuscript submission, peer review, content hosting, analytics, and identity management and expert advice to ensure each journal’s development by offering a range of options across all functions as Journal Layout, Production Services, Editorial Services, Marketing and Promotions, Online Functionality, etc. By digitalizing the publishing process, SciOpen widens the reach, deepens the impact, and accelerates the exchange of ideas.
JOURNAL
Intelligent and Converged Networks
ARTICLE TITLE
"Reconfigurable Intelligent Surfaces for Wireless Communications: Overview of Hardware Designs, Channel Models, and Estimation Techniques"
Prepare for the foreseeable future of 6G
Energy efficient solution proposed for energy hungry phased arrays in THz communications
Peer-Reviewed PublicationWith 5G wireless service becoming available and 6G systems on the horizon, scientists are working to address the high energy consumption issues related to communication in the Terahertz (THz) bandwidth, which will be crucial for the future 6G technology development. A team of researchers had undertaken a study of a reconfigurable intelligent surface technique, exploring its potential for addressing the high energy consumption problem for THz communication.
The team, with researchers from China and the United Kingdom, published their findings on April 29, 2022, in the journal Intelligent and Converged Networks at DOI: https://doi.org/10.23919/ICN.2022.0003.
THz communication generally refers to frequencies above 100 gigahertz (GHz). With its tremendous bandwidth, the THz band holds promise for its ability to support future 6G wireless systems with their high data rates. Where 5G wireless systems typically require several GHz of bandwidth in the millimeter-wave band, the THz band is capable of providing tens of GHz bandwidth. At the higher frequency rate of the THz band, one of the major obstacles is the severe propagation attenuation, where the signal loses its strength during transmission. Massive multiple-input multiple-output (MIMO) can be used to compensate for the path loss that occurs at higher frequencies. But the existing THz communication with massive MIMO has high energy consumption requirements. Reconfigurable intelligent surfaces (RIS) offer a possible solution to these high energy challenges.
An RIS is a programmable structure where the electric and magnetic properties of the surface can be changed. By changing these properties on the RIS, researchers can control communication channels. The research team addressed the high energy consumption problem in THz communication by proposing a RIS-hybrid precoding architecture, that combines analog and digital precoding, to achieve the analog beamforming. In beamforming the wireless signal is focused at a specific receiving device, instead of being broadcast in all directions, resulting in faster, more reliable connections. This RIS technique proves to be more energy efficient than the phased array technique typically used.
“Phased array-based hybrid precoding in THz communication requires a large number of analog phase shifters to realize the analog beamforming, which results in very high energy consumption. In our work, to reduce energy consumption, the energy-hungry phased array in the conventional hybrid precoding architecture is replaced by the energy-efficient RIS to realize the analog beamforming,” said Yu Lu, a Ph.D. candidate at Tsinghua University.
The team’s next step was to create a low-complexity algorithm based on deep learning to solve the analog beamforming problem and to maximize the sum-rate of the users. In deep learning, computers are taught to learn by example, similar to the way humans learn. Their simulation results showed that their proposed algorithm has a much lower runtime than the traditionally used algorithm with about the same sum-rate performance. The scientists hope that their work will motivate others toward more research involving RIS for possible application in future 6G communications.
In their research, the team only looked at the one possible scenario for RIS application, where it is used as an alternative to the traditional energy-hungry phased array at the transmitter. Looking ahead, the research team sees other possible uses for RIS. “For example, if a RIS is employed between the transmitter and receiver, RIS is able to overcome the signal blockage problem in a wireless propagation environment by providing an extra propagation path. In the future, we plan to do some in-depth research on exploiting RIS on the receiver side to enhance the received signal power,” Lu said.
Other members of the research team include Mo Hao, with Tsinghua SEM Advanced ICT Laboratory at Tsinghua University, and Richard Mackenzie, with BT Technology, Ipswich, United Kingdom. The research is funded by the National Key Research and Development Program of China and the National Natural Science Foundation of China.
The paper is also available on SciOpen (https://www.sciopen.com/home) by Tsinghua University Press.
###
About Intelligent and Converged Networks
Intelligent and Converged Networks is an international specialized journal that focuses on the latest developments in communication technology. The journal is co-published by Tsinghua University Press and the International Telecommunication Union (ITU), the United Nations specialized agency for information and communication technology (ICT). Intelligent and Converged Networks draws its name from the accelerating convergence of different fields of communication technology and the growing influence of artificial intelligence and machine learning.
About SciOpen
SciOpen is a professional open access resource for discovery of scientific and technical content published by the Tsinghua University Press and its publishing partners, providing the scholarly publishing community with innovative technology and market-leading capabilities. SciOpen provides end-to-end services across manuscript submission, peer review, content hosting, analytics, and identity management and expert advice to ensure each journal’s development by offering a range of options across all functions as Journal Layout, Production Services, Editorial Services, Marketing and Promotions, Online Functionality, etc. By digitalizing the publishing process, SciOpen widens the reach, deepens the impact, and accelerates the exchange of ideas.
JOURNAL
Intelligent and Converged Networks
ARTICLE TITLE
"Reconfigurable Intelligent Surface Based Hybrid Precoding for THz Communications"
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