Boosts access reliability in wireless communications
Scientists propose RIS technology for grant-free massive access in wireless communications
Peer-Reviewed PublicationIMAGE: ILLUSTRATION OF AN RIS-ASSISTED GRANT-FREE MASSIVE ACCESS IN A SMART FACTORY, WHERE A CLUSTER OF RIS SUBARRAYS WORKING IN THE REFRACTION MODE ARE DEPLOYED ON THE WALL OF THE FACTORY. view more
CREDIT: INTELLIGENT AND CONVERGED NETWORKS
With the emerging Internet-of-Things, that holds promise for operating everything from smart homes to smart cities, fifth-generation wireless communication must be able to handle the demands for low delay and high reliability. To meet these demands, researchers propose the use of reconfigurable intelligent surface technology for grant-free massive access to boost the reliability of the access in wireless communication.
The team, led by researchers from Beijing Institute of Technology, published their findings on April 29 in the journal Intelligent and Converged Networks at DOI: https://doi.org/10.23919/ICN.2022.0009.
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Massive machine-type communications (mMTC) is vital to fifth-generation (5G) wireless communication. In mMTC, the communication between machines over wired and wireless networks takes place with little or no intervention from humans. The emerging Internet-of-Things requires this kind of communication with minimal delay and high reliability. In the Internet of Things, machines, sensors, and robots have to be connected to run technologies ranging from smart home security systems to wearable health monitors to wireless inventory trackers to biometric cybersecurity scanners.
To meet the demands of the Internet of Things applications demanding low latency and high reliability, grant-free random access has been proposed as a promising enabler that can simplify the connection procedures and significantly reduce access delays. With grant-free random access, channel resources can be accessed without undergoing a handshake process.
The research team is exploring the reconfigurable intelligent surface (RIS) as a possible solution to these demands. An RIS is a programmable structure where the electric and magnetic properties of the surface can be changed. “We propose to leverage the burgeoning reconfigurable intelligent surface for grant-free massive access working at millimeter-wave frequency to further boost access reliability,” said Xingyu Zhou, lead study author from the Advanced Research Institute of Multidisciplinary Sciences, Beijing Institute of Technology.
Scientists have viewed RIS as an enabling technology for next generation wireless communication networks because of its ability to substantially improve the link quality and the coverage range. An RIS consists of numerous programmable passive elements with ultra-low power consumption and low hardware costs. The RIS can reconfigure the propagation of incident electromagnetic waves by attaching phase shifts that can be controlled independently controllable for each element.
The team studied a scenario that involved a cluster of RIS subarrays operating in reflection mode to assist the grant-free massive access in a smart factory. The RIS subarrays offer an additional degree of freedom and the appropriate refraction matrices design. In the grant-free access models, the most challenging problems are active device detection (ADD) and channel estimation (CE), called joint-ADDCE or JADDCE. By using theoretical derivation, where the scientists draw conclusions from other known assumptions, the team was able to show that the challenging JADDCE problem in this context has the same mathematical form as the traditional grant-free massive access. So they used the efficient approximate message passing (AMP) algorithm, to overcome the JADDCE challenges. Finally, to demonstrate the effectiveness and superiority of their proposed scheme, the team carried out numerical simulations to compare their scheme with the state-of-the-art solutions. Their scheme improved the access channel conditions and enhanced the quality of access services in the smart factory scenario.
Looking ahead the team members see the potential for wide-ranging applications. “Our proposed scheme can be widely used in the future Internet of Things network, such as in smart factories or smart cities, to enhance the efficiency of massive access,” Zhou said. “In future work, we will further exploit the powerful AI tool to implement signal processing more efficiently. Meanwhile, we will evaluate the effectiveness of our proposed scheme from more dimensions and indicators.”
The members of the research team include Xingyu Zhou, Keke Ying, Shicong Liu, Malong Ke, Zhen Gao, and Mohamed-Slim Alouini.
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 Surface Assisted Grant-Free Massive Access
Target active and passive eavesdropping
for improving communications security
IMAGE: TWO-PHASE SECURE COMMUNICATION SYSTEM view more
CREDIT: INTELLIGENT AND CONVERGED NETWORKS
Scientists have developed an intelligent reflecting surface technique to improve the security of communication systems. The IRS-aided technique achieved more secure communication in scenarios involving both active attacks and passive eavesdropping on a two-phase communication system. The research team, with scientists in China and the United Kingdom, published its findings on April 29 in the journal Intelligent and Converged Networks at DOI: https://doi.org/10.23919/ICN.2022.0001.
In recent years, the intelligent reflecting surface (IRS) has emerged as a promising technique that enhances the function and capabilities of wireless networks. An IRS, also known as a reconfigurable intelligent surface (RIS), is a programmable structure consisting of large amounts of passive and low-cost reflecting elements. The research team has shown that the IRS can change the reflection direction of a signal, allowing it to enhance the received signals coming from legitimate users, while also suppressing the signals coming from the eavesdropper. The IRS holds the potential to lessen the interference, extend the coverage area, and improve the physical layer security communication. Its ease of use is a plus too. The IRS can be readily coated on existing buildings, for example on ceilings and walls, which reduces both the cost and complexity of installing it. “The IRS provides a cost-effective and energy-efficient approach, thus holding great promise for security enhancement,” said Gui Zhou, a lead author on the study and a Ph.D. candidate at Queen Mary University of London.
Generally, eavesdroppers work in two ways. In an active attack, the eavesdropper pretends to be a legitimate user and misleads the base station into sending signals toward it during the channel estimation procedure. By comparison, a passive attack is even more challenging to detect because the passive eavesdropper can hide itself. Previous research has shown the benefits of IRS in physical layer security under the threat of active attacks. But that earlier research often assumed perfect channel state information for the eavesdropping channels at the base station. Those conditions are both strict and impractical. Where the previous research has explored imperfect channel states, they were looking at scenarios involving active attacks. This new research is the first to examine the scenario of passive eavesdropping in IRS-aided secure communication.
In the scenario that the team studied involving a two-phase communication system, the base station avoided direct transmission to the attacked user in the first phase. Then other users cooperated in forwarding signals to the attacked user in the second phase, with the help of IRS and energy harvesting technology.
The team proposed this IRS-aided two-phase secrecy communication scheme for a scenario where the eavesdropper has a similar channel direction as a legitimate user. They chose this scheme in order to acquire high-quality eavesdropping information. In specific terms, the base station transmitted signals to the legitimate user with low transmission power during the multicasting phase to reduce information being leaked to the eavesdropper. In the user cooperation phase, other legitimate users used the energy harvested in the previous phase to forward the received signals to the attacked legitimate user with the assistance of IRS. The team studied both active attack and passive eavesdropping in this scenario.
During the eavesdropping scenario and in the presence of partial channel state information, the team investigated a beamforming design problem. In beamforming, the wireless signal is focused on a specific receiving device, instead of being broadcast in all directions, resulting in faster, more reliable connections. During both the active attack and the passive eavesdropping, with partial channel state information, the team developed a beamforming design that maximizes the security rate.
Looking ahead to future studies, the researchers say that their next step is to consider a situation where a reflection link exists between the base station and IRS, where the eavesdropper can also receive the information leaked from the IRS at the first phase. This would increase the obstacle of eavesdropping suppression. “The ultimate goal is to use IRS technology to improve physical layer security under imperfect channel state information,” said Zhou.
The research teams include Gui Zhou and Kok Keong Chai from Queen Mary University of London, United Kingdom; Cunhua Pan and Hong Ren from Southeast University, China; Kezhi Wang from Northumbria University, United Kingdom; and Kai-Kit Wong from University College of London, United Kingdom.
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
User cooperation for IRS-aided secure MIMO systems
Timing, among other factors, improves aging in next-generation wireless communications
IMAGE: A MULTI-USER MISO COMMUNICATION SYSTEM IS CONSIDERED, WHERE A BS EQUIPPED WITH NT ANTENNAS SERVES K (K < NT) SINGLE-ANTENNA USERS. THE COMMUNICATION IS ASSISTED BY AN RIS COMPRISING OF M NEARLY-PASSIVE REFLECTING ELEMENTS AND ONE RIS MICRO-CONTROLLER. WE ASSUME THAT THE BS AND THE RIS KEEP STATIC AND THE USERS ARE MOVING WITH THE SAME VELOCITY. view more
CREDIT: INTELLIGENT AND CONVERGED NETWORKS
In wireless communications, channels can not only change, but they can also age. For contemporary systems, these connections between the transmitter and the receiver break down over time, user movement and power dissipation. Understanding how channels age in future systems, as well as how to mitigate such issues, are key to developing the next generation of wireless communications, according to an international collaboration studying the topic in reconfigurable intelligent surface (RIS)-assisted systems.
They published an analysis of how RIS-assisted communication systems perform under channel aging on April 29 in Intelligent and Converged Networks at DOI: https://doi.org/10.23919/ICN.2022.0002.
RISs are arrays comprising individually programmable and controlled circuits that can dynamically reflect signals and may be the linchpin platform to achieve 6G wireless communications, according to first author Yan Zhang, School of Electronic and Information Engineering, Beijing Jiaotong University.
“Investigating the performance of RIS-assisted communication systems under the condition of channel aging can verify whether deploying an RIS in a wireless communication system can reduce the adverse impact of channel aging on system performance and how much performance gain it can bring,” Zhang said. “This is helpful to provide a theoretical basis for the system optimization design of RIS-assisted communication systems.”
All three components of the communication system can move: the RIS may be a satellite, the base station moves as the Earth rotates and the users are unpredictably mobile. Add in modifications to the communication environment, such as physical barriers or weather interference, and the channels of communication will continuously change over time.
“These factors lead to the so-called channel aging phenomenon where the channels vary across time with correlated channel variables in a transmission,” Zhang said. “Channel aging results in a mismatch between the current and estimated channels that degrades the system performance. But, to the best of our knowledge, there is a lack of studies on the impact of channel aging on RIS-assisted communications systems. Since RIS will help evolve wireless communication, it is of great importance to analyze how RISs can improve the channel quality with user mobility.”
The researchers examined how deploying an RIS in a wireless communication system affects the adverse impact of channel aging on system performance. They modeled a system in which a base station simultaneously sends signals to an RIS and to individual cell phone users. The RIS reflects the signal to the same users, duplicating and strengthening the signal. In this model, the RIS and base station are stationary while the users are moving in a single direction at the same velocity, such as on a highway.
The system mathematically estimates the best channel to send a signal, depending on location, movement, potential barriers and several other factors. The channel varies from the time it is estimated to when it is used to send or detect the signal — this is the aging phenomenon.
“Due to the existence of an extra end-to-end signal propagation path established by the RIS, we found that RISs can reduce the adverse effects of channel aging on the communication system, as well as improve the overall system performance, compared to systems without an RIS,” Zhang said, “Moreover, the system performance improved as the total transmit power and the number of antennas at the base station, the number of the RIS’s reflecting elements and the temporal correlation coefficient increased.”
But, Zhang said, while the RIS can increase transmission capacity by adding reflecting elements, it does not have infinite capacity since it will eventually become saturated.
“This analysis is helpful in providing a theoretical basis for the system optimization design of RIS-assisted communication systems,” Zhang said. “The study can be further generalized along with several promising future work directions, as well. For example, we can apply this approach to the study of spatially correlated fading and more efficient channel estimation methods, to name just a few.”
Other contributors include Huahua Xiao, ZTE Corporation, State Key Laboratory of Mobile Network and Mobile Multimedia Technology; Jiayi Zhang, School of Electronic and Information Engineering, Beijing Jiaotong University; Bo Ai, State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiatong University; and Derrick Wing Kwan Ng, School of Electrical Engineering and Telecommunications, University of New South Wales.
The National Key Research and Development Program of China, the National Natural Science Foundation of China, the Beijing Natural Science Foundation, the Natural Science Foundation of Jiangsu Province, the Royal Society Newton Advanced Fellowship, the Frontiers Science Center for Smart High-Speed Railway System, the Project of China Shenhua, the Fundamental Research Funds for the Central Universities in China, ZTE Corporation, the State Key Laboratory of Mobile Network and Mobile Multimedia Technology, the UNSW Digital Grid Futures Institute and the Australian Research Council’s Discovery Project funded 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
"Performance analysis of reconfigurable intelligent surface assisted systems under channel aging"
The promise and challenge of reconfigurable intelligent surfaces
The world is more connected than ever before, with reliable and consistent wireless communications transmitting to and from individual users — but the technology is evolving to something even better, according to an international research team.
They published an overview of the next-generation technology, called reconfigurable intelligent surfaces (RISs) on April 29 in Intelligent and Converged Networks at DOI: https://doi.org/10.23919/ICN.2022.0007.
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A RIS is an array of dynamic yet passive elements that can be individually and independently controlled to precisely direct a transmission signal from a base station to a mobile user.
“The RIS is an emerging technology, which will hopefully bring a new revolution in wireless communications,” said paper author Muhammad Siddiqi, a graduate student in electronics engineering at Tsinghua University. “RIS has gained enormous attention in recent years by researchers of different communities, and therefore, several research papers have been published in this regard. However, there are still some important open problems that need to be solved.”
In this paper, the researchers provide a comprehensive survey on the emerging RIS technology and discuss key aspects from existing research, including challenges. From detailing RIS models to probing basic transmission principles in the context of RIS to examining prototyped RIS-aided communication systems, the researchers emphasize the promise of RIS while simultaneously stressing caution.
“To provide deep insight on the individual topics, we have given some examples to show the importance of RIS technology in future wireless systems,” said paper author Talha Mir, assistant professor of electronic engineering, Balochistan University of Information Technology, Engineering, and Management Sciences. “We also highlighted the key challenges and provided some opportunities to guide readers for future research trends in the field of RIS-aided communications.”
For example, RISs differ from conventional antenna arrays because they do not perform complex signal processing on incoming transmissions to send them to the intended receiver. Instead, they simply reflect the transmitted signal from the base station to the mobile user. The individual cell units of the RIS are passive unless one needs to be adjusted to achieve the correct angle for a particular signal. Even that adjustment, however, does not require complex processing.
“RIS technology does not incur additional noise while retransmitting the incident wave, which is a substantially unique feature from conventional wireless communication systems,” Siddiqi said. “That’s one new opportunity RISs bring to researchers in the fields of information theory, electromagnetics, wireless communications and signal processing.”
While the opportunities exist, so do the challenges, the researchers said. RIS may not add noise to a signal, but the best approach to estimating and transmitting along a channel remains debatable.
“The channel model of a RIS is still controversial, since some analytical results in existing papers have not been verified by experiments yet,” Mir said. “We are not yet sure, among existing available models, which one will be the best choice for practical scenarios.”
The researchers found the same cautious optimizing in several other areas of RIS research, including performance analysis and RIS implementation, among others.
“It is expected that RIS will be an important research topic in the years to come as it has the potential to create a new horizon in the field of wireless communications,” Mir said. “We believe that RIS technology will become an integral part of future wireless communications, once we answer some important yet challenging questions.”
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 Surface-Aided Wireless Communications: An Overview"
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