Channel Reliability Research Articles

Fresh Caching of Dynamic Content Over the Wireless Edge

We introduce a framework and provably-efficient schemes for ‘fresh’ caching at the (front-end) local cache of content that is subject to ‘dynamic’ updates at the (back-end) database. We start by formulating the hard-cache-constrained problem for this setting, which quickly becomes intractable due to the limited cache. To bypass this challenge, we first propose a flexible time-based-eviction model to derive the average system cost function that measures the system’s cost due to the service of aging content in addition to the regular cache miss cost. Next, we solve the cache-unconstrained case, which reveals how the refresh dynamics and popularity of content affect optimal caching. Then, we extend our approach to a soft-cache-constrained version, where we can guarantee that the cache use is limited with arbitrarily high probability. The corresponding solution reveals the interesting insight that ‘whether to cache an item or not in the local cache?’ depends primarily on its popularity level and channel reliability, whereas ‘how long the cached item should be held in the cache before eviction?’ depends primarily on its refresh rate. Moreover, we investigate the cost-cache saving trade-offs and prove that substantial cache gains can be obtained while also asymptotically achieving the minimum cost as the database size grows.

The Effects of Vehicle-to-Infrastructure Communication Reliability on Performance of Signalized Intersection Traffic Control

Vehicle-to-infrastructure communications can inform an intersection controller about the location and speed of connected vehicles. Recently, the design of adaptive intersection control algorithms that utilize this information received substantial research attention. These studies typically assume perfect communications. This study explores the possible effects of a temporal decrease in the reliability of the communication channel, on the intersection throughput. Road traffic and DSRC-VANET communications are modelled by integrating traffic and communication simulation tools (Vissim and OMNeT++, respectively). Simulations of scenarios with challenging, but realistic communication distortions conditions show significantly larger average delays to vehicles compared to scenarios with perfect communication conditions. These additional delays are largely independent of whether all or only some of the intersection approaches are affected by the communication distortions. Furthermore, delays do not increase uniformly on all signal groups. They may even decrease for some, which causes unfair allocation of green times. The control may be corrected for the lost communications using the information received in previous time intervals and simple assumptions about the vehicle movements. This correction decreases delays in all scenarios both for isolated and connected intersections. It performs similarly to the case with perfect communications when the communication distortions are distributed uniformly among all intersection approaches. Overall, the results demonstrate that the impact of the communication distortions should be considered in the design of the adaptive intersection control algorithms.

Position coding as a means of increasing the range of optical communications links

Subject of study. We present research on the range of atmospheric optical communications links as a function of atmospheric conditions, the types of laser beam modulation used, and the type of interference-resistant coding used. Aim. We develop an approach for increasing the range of free-space optical communications links by improving resistance to atmospheric turbulence. Methods. We show that the modulation technique and channel coding must be compatible if optimum results are to be achieved. Pulse position modulation and interference-resistant position coding are one example of such a compatible combination; a holographic code in which a sequence of pulses representing a 1D linear hologram of a single pulse replaces a single pulse in the desired position is one example of an interference-resistant code. In this case, position modulation is still being used, but in the form of multiple pulse position modulation. A holographic code takes advantage of the fact that holograms are divisible, and a fragment of the hologram can be used for recovery of transmitted data (as well as data hidden by noise). The recovery capacity of the holographic code depends on the hologram length—the number of slots per symbol interval. Main results. We show that holographic coding provides higher interference resistance and a lower probability of detector error and provides the same benefit as an increase in transmitter power. Practical significance. The benefit from holographic coding may be used to either increase the communications range or increase the communications channel reliability. Position coding has the advantages that the redundant information required for interference-resistant encoding is created within the symbol interval, does not affect the symbol repetition frequency, and has no effect on the data transmission rate.

Security State Estimation for Cyber-Physical Systems against DoS Attacks via Reinforcement Learning and Game Theory

This paper addressed the optimal policy selection problem of attacker and sensor in cyber-physical systems (CPSs) under denial of service (DoS) attacks. Since the sensor and the attacker have opposite goals, a two-player zero-sum game is introduced to describe the game between the sensor and the attacker, and the Nash equilibrium strategies are studied to obtain the optimal actions. In order to effectively evaluate and quantify the gains, a reinforcement learning algorithm is proposed to dynamically adjust the corresponding strategies. Furthermore, security state estimation is introduced to evaluate the impact of offensive and defensive strategies on CPSs. In the algorithm, the ε-greedy policy is improved to make optimal choices based on sufficient learning, achieving a balance of exploration and exploitation. It is worth noting that the channel reliability factor is considered in order to study CPSs with multiple reasons for packet loss. The reinforcement learning algorithm is designed in two scenarios: reliable channel (that is, the reason for packet loss is only DoS attacks) and unreliable channel (the reason for packet loss is not entirely from DoS attacks). The simulation results of the two scenarios show that the proposed reinforcement learning algorithm can quickly converge to the Nash equilibrium policies of both sides, proving the availability and effectiveness of the algorithm.

Fake & original: the case of Japanese food in Southeast Asian countries

This paper seeks to answer two main questions: whether restaurants using a national brand to capture customers in fact use original national ingredients for producing food and, in cases where original ingredients are not used, what is the economic rationale behind this choice? Specifically, the study focuses on Japanese restaurants in three Southeast Asian countries, using a theoretical model and an empirical investigation based on interviews and survey data collected through field research. Considering restaurants, their suppliers, and their customers, we show how a dual asymmetric-information problem exists, between suppliers and restaurants and between restaurants and their customers. The results indicate that a first reason for buying non-original ingredients—important especially for cheaper restaurants—is a desire to reduce costs. That said, the use of non-original ingredients occurs among all types of Japanese restaurants in the three studied countries. It does not depend on the presence of a Japanese chef or owner, nor on the share of Japanese customers. By contrast it does significantly depend on the reliability of the wholesale channel, and the resultant difficulties that restaurants encounter when buying original ingredients.

Evaluation of the Rationality of Using GSM-R Modems of the New Series

The article highlights the problematic issues related to the appearance of a new specialized GSM-R modem TRC-5RME (ext)* H on the market, the serial production of which was launched in 2020 by the German company TRIORAIL, which is one of the leaders in the European market for the production of specialized equipment for railway rolling stock. Would it be rational to use the new TRC-5rme (ext)* H modem to solve the tasks assigned to the rolling stock communication equipment? What major changeswill already existing solutions that have been used for a long time on the railway transport of different countries undergo? To identify the factors contributing to the adoption of such a decision, a comparative analysis of the characteristics of modems will be carried out. Special attention will be paid to the speed of information transmission and indicators of the reliability of the communication channel. The design features of the modem of the new series will also be analyzed, a preliminary assessment of the integration of the TRC-5rme (ext) H modem into existing communication equipment manufactured by enterprises will be carried out.

Comparative analysis of magnetic induction based communication techniques for wireless underground sensor networks.

A large range of applications have been identified based upon the communication of underground sensors deeply buried in the soil. The classical electromagnetic wave (EM) approach, which works well for terrestrial communication in air medium, when applied for this underground communication, suffers from significant challenges attributing to signal absorption by rocks, soil, or water contents, highly varying channel condition caused by soil characteristics, and requirement of big antennas. As a strong alternative of EM, various magnetic induction (MI) techniques have been introduced. These techniques basically depend upon the magnetic induction between two coupled coils associated with transceiver sensor nodes. This paper elaborates on three basic MI communication mechanisms i.e. direct MI transmission, MI waveguide transmission, and 3D coil MI communication with detailed discussion of their working mechanism, advantages and limitations. The comparative analysis of these MI techniques with each other as well as with EM wave method will facilitate the users in choosing the best method to offer enhanced transmission range (upto 250 m), reduced path loss (<100 dB), channel reliability, working bandwidth (1–2 kHz), & omni-directional coverage to realize the promising MI-based wireless underground sensor network (WUSN) applications.

ПЕРЕСТАНОВОЧНОЕ ДЕКОДИРОВАНИЕ В МАЛОМОЩНЫХ БЕСПРОВОДНЫХ СЕНСОРНЫХ СЕТЯХ

Wireless sensor networks are currently considered for many subject areas as effective communication systems, including, for example, industrial and agricultural facilities and enterprises, monitoring of sensors of transport security systems, medicine applications, environmental and weather monitoring, etc. In such systems, the correction code (CC) is a classic approach used to increase the reliability of the data transmission channel while simultaneously reducing the required transmitted signal power, called the energy gain code. At the same time, the power of the transmitter is reduced due to additional power consumption in the receiver decoder. Stronger codes provide better performance with lower power requirements, but have more complex decoders with higher power consumption than relatively simple error control systems. If the additional power consumption at the output of the decoder exceeds the savings in transmitted power due to the use of CC, then such a code will not be energy efficient compared to a system with a non-redundant code. Various codes can be used to protect data, while the best codes for which the critical distance turns out to be large according to a number of studies are codes with a low parity check density. The paper proposes an alternative variant based on the synthesis of a permutation decoding system using the method of localization of a limited number of permutations and the organization of additional parity checks exclusively for the verification bits of the CC using the Bayesian approach to iterative transformations of integer soft solutions of symbols.

5G New Radio Physical Downlink Control Channel Reliability Enhancements for Multiple Transmission-Reception-Point Communications

Non-coherent transmission from multiple transmission-reception-points (TRPs)/base stations or panels to a user equipment (UE) is exploited in 5G NR to improve downlink reliability and cell-edge throughput. Ultra reliable low-latency communications (URLLC) and enhanced Mobile BroadBand (eMBB) are prominent target use-cases for multi-TRP or multi-panel transmissions. In Third-Generation Partnership Project (3GPP) Release 17 specifications, multi-TRP-based transmissions were specified for the physical downlink control channel (PDCCH) specifically to enhance its reliability and robustness. In this work, a comprehensive account of various multi-TRP reliability enhancement schemes applicable for the 5G NR PDCCH, including the ones supported by the 3GPP Release 17 specifications, is provided. The impact of the specifications for each scheme, UE and network complexity and their utility in various use-cases is studied. Their error performances are evaluated via link-level simulations using the evaluation criteria agreed in the 3GPP proceedings. The 3GPP-supported multi-TRP PDCCH repetition schemes, and additionally proposed PDCCH repetition and diversity schemes are shown to be effective in improving 5G NR PDCCH reliability and combating link blockage in mmWave scenarios. The link-level simulations also provide insights for the implementation of the decoding schemes for the PDCCH enhancements in different channel scenarios. Analysis of the performance, complexity and implementation constraints of the proposed PDCCH transmission schemes indicate their suitability to UEs with reduced-capability or stricter memory constraints and flexible network scheduling.

Modeling of information transmission systems in modern mobile terms

The work is dedicated to information transmission systems in modern mobile networks. The main task of any information transmission system is to combat various kinds of interference which lead to distortion or complete information loss and thus reduced communication channel reliability. Therefore, it became necessary to develop adaptive data transmission systems, in which adaptive methods help to achieve high-quality control in the absence of sufficiently complete a priori information about the characteristics of the controlled process or under conditions of uncertainty. The research was carried out on a simulation model of data transmission built on the basis of binary symmetry. The proposed adaptive system is based on the assessment of the state of the data transmission channel, according to which the bit rate of the transmitted data and the parameters of the noise-correcting code are selected, which provides a certain level of errors on the receiving side, taking into account the limited bandwidth of the communication channel. The developed simulation model of adaptation to the state of the communication channel demonstrates the required level of reliability and allows to work with different levels of noise in the communication channels, and the occurrence of an error in the channel can be either uniform during data transmission or random. The results of simulation modeling testify to the correctness of the proposed solution and allow the evaluation the main parameters of information transmission systems in mobile networks. The proposed model of information transmission with adaptation to the state of the communication channel may be applied in modern mobile networks, telecommunications and computer systems with an increased level of quality requirements for information transmitted at low speed, since the proposed solution does not require complex calculations.

On the assessment of the reliability of the train radio communication channel

The research purposeis to develop an approach to assessing the reliability of a train radio communication channel based on the representation of a radio communication network in the form of a model that includes both traditional elements (various types of equipment, a wire channel) and a radio channel, which is proposed to be described by the availability of radio coverage, which varies depending on the location of the mobile subscriber. In the research methods of the theory of reliability, and, in particular, the assessment of the availability factor of the elements of the radio communication system and communication channels, dynamically changing during the movement of the mobile radio station. In addition, to assess the energy of radio channels, the theory of radio wave propagation was applied, including on the basis of industry recommendations for calculating radio communication networks of JSC Russian Railways. As result of the research, a method was proposed for assessing the dependence of the reliability of a train radio communication channel (in terms of readiness) on the track coordinate. In this case, the radio communication channel dynamically changes the composition of the elements when the mobile subscriber moves along the railway section. Simultaneously, for each point of the section, the calculation formula is also dynamically changed, which makes it possible to find the value of the readiness of the communication channel. The proposed approach allows to identify the sections of technological radio communication networks that are weakest from the point of view of communication reliability and take this information into account when planning work to improve the reliability of communication networks.

A high-density 256-channel cap for dry electroencephalography.

High‐density electroencephalography (HD‐EEG) is currently limited to laboratory environments since state‐of‐the‐art electrode caps require skilled staff and extensive preparation. We propose and evaluate a 256‐channel cap with dry multipin electrodes for HD‐EEG. We describe the designs of the dry electrodes made from polyurethane and coated with Ag/AgCl. We compare in a study with 30 volunteers the novel dry HD‐EEG cap to a conventional gel‐based cap for electrode‐skin impedances, resting state EEG, and visual evoked potentials (VEP). We perform wearing tests with eight electrodes mimicking cap applications on real human and artificial skin. Average impedances below 900 kΩ for 252 out of 256 dry electrodes enables recording with state‐of‐the‐art EEG amplifiers. For the dry EEG cap, we obtained a channel reliability of 84% and a reduction of the preparation time of 69%. After exclusion of an average of 16% (dry) and 3% (gel‐based) bad channels, resting state EEG, alpha activity, and pattern reversal VEP can be recorded with less than 5% significant differences in all compared signal characteristics metrics. Volunteers reported wearing comfort of 3.6 ± 1.5 and 4.0 ± 1.8 for the dry and 2.5 ± 1.0 and 3.0 ± 1.1 for the gel‐based cap prior and after the EEG recordings, respectively (scale 1–10). Wearing tests indicated that up to 3,200 applications are possible for the dry electrodes. The 256‐channel HD‐EEG dry electrode cap overcomes the principal limitations of HD‐EEG regarding preparation complexity and allows rapid application by not medically trained persons, enabling new use cases for HD‐EEG.

Communication via mobile phone as an effective tool of public health: Findings of MAMAmobi program

IssueThe level of timely referrals to health specialists among Russian pregnant women is low, as well as the level of preventive knowledge and health information that often is derived from unreliable sources. About 2/3 of Russian women who are smoking don't quit smoking during pregnancy and breastfeeding. There is low level of breast feeding among Russian women. During COVID -19 there is need for reliable information. Given the geography of the country, there is need for pregnant woman and mothers with a newborn for modern health service and relevant information.DescriptionProgram MAMAmobi - free mobile service for pregnant women and new mothers to delivering up-to-date health information regarding maternal and child health via all channels on mobile phones: messengers, mobile applications, YouTube, social media, Email, text msgs, etc. All the content and messages are developed and reviewed by the leading experts in the field. Each client automatically receives individual messages on her mobile phones according to her pregnancy term or a baby birthday.Results250,000 pregnant women and new mothers reached by the program annually. Program monitoring identified increasing number of women who practice breast feeding and practice healthy behaviour. Dissemination of the evidence-based information on vaccine and immunisation among the audience increase women make a rational decision. The rate of women taking folic acid is higher among women participating in the program compared to control group.LessonsCommunication via mobile phone brings the most accurate information to women, motivate them to keep their own health and babies' health, allow to deliver information on urgent issues, establish high reliability of such channel and keep adherence to the program very high.Key messages The service is a viable tool that brings improvement in women’s knowledge on maternal and child health including prevention of smoking and alcohol consumptions, COVID-19 and etc and change behaviour.The communication channels on smartphones should be changed according to expectations of the target group and available technology.

The Arch Electrode: A Novel Dry Electrode Concept for Improved Wearing Comfort.

Electroencephalography (EEG) is increasingly used for repetitive and prolonged applications like neurofeedback, brain computer interfacing, and long-term intermittent monitoring. Dry-contact electrodes enable rapid self-application. A common drawback of existing dry electrodes is the limited wearing comfort during prolonged application. We propose a novel dry Arch electrode. Five semi-circular arches are arranged parallelly on a common baseplate. The electrode substrate material is a flexible thermoplastic polyurethane (TPU) produced by additive manufacturing. A chemical coating of Silver/Silver-Chloride (Ag/AgCl) is applied by electroless plating using a novel surface functionalization method. Arch electrodes were manufactured and validated in terms of mechanical durability, electrochemical stability, in vivo applicability, and signal characteristics. We compare the results of the dry arch electrodes with dry pin-shaped and conventional gel-based electrodes. 21-channel EEG recordings were acquired on 10 male and 5 female volunteers. The tests included resting state EEG, alpha activity, and a visual evoked potential. Wearing comfort was rated by the subjects directly after application, as well as at 30 min and 60 min of wearing. Our results show that the novel plating technique provides a well-adhering electrically conductive and electrochemically stable coating, withstanding repetitive strain and bending tests. The signal quality of the Arch electrodes is comparable to pin-shaped dry electrodes. The average channel reliability of the Arch electrode setup was 91.9 ± 9.5%. No considerable differences in signal characteristics have been observed for the gel-based, dry pin-shaped, and arch-shaped electrodes after the identification and exclusion of bad channels. The comfort was improved in comparison to pin-shaped electrodes and enabled applications of over 60 min duration. Arch electrodes required individual adaptation of the electrodes to the orientation and hairstyle of the volunteers. This initial preparation time of the 21-channel cap increased from an average of 5 min for pin-like electrodes to 15 min for Arch electrodes and 22 min for gel-based electrodes. However, when re-applying the arch electrode cap on the same volunteer, preparation times of pin-shaped and arch-shaped electrodes were comparable. In summary, our results indicate the applicability of the novel Arch electrode and coating for EEG acquisition. The novel electrode enables increased comfort for prolonged dry-contact measurement.

Subcarrier Mapping for Underwater Video Transmission Over OFDM

We study the transmission of high-quality video underwater. The underwater acoustic medium pathloss attenuation depends not only on transmission distance but also on the frequency occupied by the signal, where lower frequencies have lower attenuation for a given distance. We propose cross-layer design algorithms that exploit this frequency-dependent attenuation by connecting channel reliability to the structure of the compressed video. The video data are categorized based on their importance. Orthogonal frequency-division multiplexing is adopted as the modulation technique, such that different data can be sent on different frequencies. The underlying communications system accompanied with a noise analysis is developed in this article. The signal and noise statistics are used in the simulations to represent the underwater channel. We propose three new techniques and compare them to three baseline techniques. In the proposed techniques, important video information is transmitted on the least attenuated frequencies while less important data are transmitted through higher frequencies. Simulation results show that at least one of our proposed techniques can achieve significant improvements in the peak signal-to-noise ratio in comparison to the baseline techniques.

Real-time bi-directional people counting using an RGB-D camera

Purpose The purpose of this paper is to propose a new framework and improve a bi-directional people counting technique using an RGB-D camera to obtain accurate results with fast computation time. Therefore, it can be used in real-time applications. Design/methodology/approach First, image calibration is proposed to obtain the ratio and shift values between the depth and the RGB image. In the depth image, a person is detected as foreground by removing the background. Then, the region of interest (ROI) of the detected people is registered based on their location and mapped to an RGB image. Registered people are tracked in RGB images based on the channel and spatial reliability. Finally, people were counted when they crossed the line of interest (LOI) and their displacement distance was more than 2 m. Findings It was found that the proposed people counting method achieves high accuracy with fast computation time to be used in PCs and embedded systems. The precision rate is 99% with a computation time of 35 frames per second (fps) using a PC and 18 fps using the NVIDIA Jetson TX2. Practical implications The precision rate is 99% with a computation time of 35 frames per second (fps) using a PC and 18 fps using the NVIDIA Jetson TX2. Originality/value The proposed method can count the number of people entering and exiting a room at the same time. If the previous systems were limited to only one to two people in a frame, this system can count many people in a frame. In addition, this system can handle some problems in people counting, such as people who are blocked by others, people moving in another direction suddenly, and people who are standing still.

A Novel Coordinated Multipoint Scheme With Zero Guard Interval for ATSC 3.0 Single Frequency Networks

Advanced Television Systems Committee (ATSC) has issued ATSC 3.0 as the standard for the next-generation of Digital Terrestrial Television (DTT) broadcasting. ATSC 3.0 introduces several new features including Layered Division Multiplexing (LDM) that is a form of Non-Orthogonal Multiple Access (NOMA). ATSC 3.0 supports the legacy Single Frequency Networks (SFN), where the Guard Interval (GI) is considered to overcome the multipath as well as the asynchronous reception from different transmitters. Considering the huge distances between the DTT broadcasters, the GI overhead could be comparable to the data size, making the control/data ratio unfavorable. This paper proposes the association of Coordinated MultiPoint (CoMP) in SFN with NOMA-LDM. A novel formation of the channel matrix is provided that jointly includes the asynchronous channel's cross correlations for further joint detection of the signals at the receiver. The purpose is to enhance the coverage and spectral efficiency while avoiding hectic guard intervals or directional antennas. The capacity region is derived in an information theoretic framework based on exploiting the asynchronous channels' memory and correlation. We show that the spectral efficiency can exceed that of the non-coordinating schemes, provided that the proper receiver is equipped with the proposed channel matrix formation. Our extensive simulations validate that our proposed association of CoMP-SFN with NOMA-LDM provides a considerable boost in the coverage and channel reliability, while increasing the spectral and power efficiency.

DLSTM-Based Successive Cancellation Flipping Decoder for Short Polar Codes.

Polar code has been adopted as the control channel coding scheme for the fifth generation (5G), and the performance of short polar codes is receiving intensive attention. The successive cancellation flipping (SC flipping) algorithm suffers a significant performance loss in short block lengths. To address this issue, we propose a double long short-term memory (DLSTM) neural network to locate the first error bit. To enhance the prediction accuracy of the DLSTM network, all frozen bits are clipped in the output layer. Then, Gaussian approximation is applied to measure the channel reliability and rank the flipping set to choose the least reliable position for multi-bit flipping. To be robust under different codewords, padding and masking strategies aid the network architecture to be compatible with multiple block lengths. Numerical results indicate that the error-correction performance of the proposed algorithm is competitive with that of the CA-SCL algorithm. It has better performance than the machine learning-based multi-bit flipping SC (ML-MSCF) decoder and the dynamic SC flipping (DSCF) decoder for short polar codes.

Design of Training Sequences for Multi User—MIMO with Accurate Channel Estimation Considering Channel Reliability Under Perfect Channel State Information Using Cuckoo Optimization

Design of Training Sequences for Multi User—MIMO with Accurate Channel Estimation Considering Channel Reliability Under Perfect Channel State Information Using Cuckoo Optimization

Online Learning-Based Reconfigurable Antenna Mode Selection Exploiting Channel Correlation

Reconfigurable antennas (RAs) emerged as a promising technology that can deal with channel variations and enhance the capacity and reliability of the wireless channel. To fully exploit the advantage of RAs, optimal antenna modes need to be selected in an online manner. However, the channel statistics are unknown a priori. Multi-armed bandit-based online learning algorithms were proposed to address this challenge, but the main drawback of existing approaches are that their regret scales linearly with the number of antenna modes, which converges slowly when the latter is large. To improve the scalability, we first apply an existing algorithm: Thompson sampling via Gaussian process (TS-GP), and propose two new algorithms for antenna mode selection: upper confidence bound with channel prediction (UCB-CP) and Thompson Sampling with channel prediction (TS-CP). TS-GP uses Gaussian prior to model the reward distribution of each antenna mode, as well as the correlation among them. UCB-CP and TS-CP exploit channel modeling to predict the channel conditions of unexplored antenna modes at each time step, by relating the correlation between different channel states to the underlying antenna modes. We prove the finite-time regret bound of UCB-CP and show that it is independent from the number of arms, when the expected channel estimation errors are small enough. We also extend the algorithms to the mobile setting. Both simulation results and real-world experiments show that all of our proposed learning algorithms can significantly improve the convergence rate and yield much lower regret (thus higher throughput) than existing schemes.